WO2012098160A1

WO2012098160A1 - Disposable protection for micro-engineered devices

Info

Publication number: WO2012098160A1
Application number: PCT/EP2012/050715
Authority: WO
Inventors: Alexandru ANDREI; Wolfgang Eberle; Karl Malachowski; Philippe Soussan; Simone Severi
Original assignee: Imec
Priority date: 2011-01-18
Filing date: 2012-01-18
Publication date: 2012-07-26

Abstract

A device (100) is presented comprising a functional structure (101) that needs to be partially exposed and therefore mechanically unprotected during the usage of the device. This exposed functional structure is part of a micromachined device having also a part that is mounted and protected by an electronic package (102). A micromachined protection structure (103) is attached to the functional structure via at least one anchoring mechanism (104). The protection structure (103) can be detached by breaking the anchoring mechanism (104). Furthermore, a method to fabricate such a device (100) is presented.

Description

Disposable protection for micro-engineered devices

Field of the Invention

The present invention relates to a device comprising a disposable and temporary protection of at least part of an exposed functional structure, e.g. of at least part of a micro-machined device. Said protection may be especially beneficial for structures comprising one or more parts having high aspect ratio dimensions, in order to protect the high aspect ratio part(s). More particularly, the present invention relates to a device comprising a protection structure suitable for protecting fragile micro-machined exposed functional structures such as neural implants.

Furthermore the invention relates to processing methods for manufacturing a device comprising a temporary protection structure for at least one exposed functional structure such as e.g. at least one fragile micro-machined part of the device partially unprotected by the packaging, and to devices comprising the temporary protection structure manufactured by the method.

Background of the Invention

Micro Electrical Mechanical Systems (MEMS) based on Silicon wafer level processing techniques started to be used about 20 years ago for their capability of sensor miniaturization and batch production. This significantly improved performances and reduced production costs. However, most of the time these devices are fragile and their packaging is always an issue that sometimes multiplies by 10 or more the price of the final product. Appropriate protection of fragile MEMS is even more difficult to achieve when some part of the M EMS needs to be exposed to the outside world during its use. This part of the device will be referred to as "exposed functional structure" in the rest of the document.

In the particular case (but this can be generalized to any MEMS) the device comprises an exposed micro-machined structure that has high aspect ratio dimensions, e.g. having one dimension 100 times or more bigger than the other two dimensions (for example L = few centimeters, H and W = few micrometers), protection of said fragile structure is extremely important. Said structure may be for example the implanted part of a micro-machined neural implant. Said structure needs to be protected in order to allow the full device to be safely packaged, shipped and manipulated by the end user without having any area of its body accidentally touched (for these sizes touching is equivalent to irreversible damage or brake). The end user needs to remove the protection only at the very last moment when he or she intends to use the device. The problem behind the present invention is hence protecting a structure temporarily up to just before actual use. Lin et al. (US 5,591,139) describe an IC processed micro-needle. The micro-needle includes an interface region and a shaft. The micro-needle is attached to a wafer via support beams. To facilitate testing and manipulation, the micro-needle can be separated from the wafer by breaking the support beams. Although Lin et al. offer protection for the micro-needle, no disclosure is made of a protection for a product which can be directly used after removing the protection, in which the end user needs to remove the protection only at the very last moment when he or she intends to use the device. The device presented by Lin et al. comprises a structure that can be detached from the wafer but offers no protection for such structure during further processing or handling steps after detaching the micro-needle from the wafer. Hence, the technique presented by Lin et al. does not provide a protection solution for singulated devices i.e. after they have been removed from the wafer.

Previous work, such as for example by Lin et al., does not describe packaged devices, they describe e.g. only devices without a package. These devices still need to be packaged before they can be used e.g. for implanting or other purposes. At this moment there is no suitable solution that does not involve any additional processing (i.e. that are built in the same time as the micromachined device itself) for fragile devices such as e.g. packaged neural implants and other products which need to be protected during transport in order to avoid breaking off or bending of exposed functional structures such as e.g. the needles of implants.

Summary of the Invention It is an object of embodiments of the present invention to provide a good disposable protection for micro-engineered devices, in particular for example for high aspect ratio parts micro-engineered devices.

The above objective is accomplished by a device and a method according to embodiments of the present invention. In a first aspect of the invention a device is provided comprising:

A micromachined device having an exposed functional structure and an unexposed functional structure;

a package on which the micromachined device is mounted and that protects the unexposed functional structure of the micromachined device but leaves the unexposed functional structure externally accessible; and a protection structure for at least part of the exposed functional structure, attached to the micromachined device via at least one anchoring mechanism, wherein the protection structure (103) can be detached by breaking the at least one anchoring mechanism.

It is an advantage of embodiments of the present invention that an individual device has its own protection structure and may keep this protection structure trough all steps of device singulation, packaging, storage, shipping and further handling, up to just before actual use.

In embodiments of the first aspect of the invention, the exposed functional structure may comprise any part of a MEMS device, a micro-needle, a probe, a neural implant or any other fragile micromachined device part which needs to be protected for handling purposes. In embodiments of the first aspect of the invention, the at least one anchoring mechanism may comprise a membrane, connecting the protection structure to an outer edge of the micromachined device. The membrane, at locations where it forms the anchoring mechanism, may have a different, in particular lower, mechanical strength value than the material surrounding the anchoring mechanism. In embodiments of the first aspect of the invention, the at least one anchoring mechanism may partly or fully connect the protection structure to the micromachined device. In embodiments of the present invention, the protection structure may be provided at at least one side of the part of the exposed functional structure to be protected, for example at at least one side of a high aspect ratio part thereof. In particularly advantageous embodiments, the protection structure substantially surrounds an exposed functional structure to be protected, for example a high aspect ratio part thereof. With "substantially surrounds" is meant that the surrounding is over 75% or more, for example 80% or more, such as e.g. 90% or more of the circumference of the exposed functional structure. The surrounding of the protection structure with respect to the exposed functional structure may be a surrounding in a plane, i.e. the protection structure in accordance with embodiments of the present invention does not need to surround in a third dimension the exposed functional structure to be protected. The "surrounding" protection structure allows to more reliably protect the exposed functional structure.

In embodiments of the first aspect of the invention, the protection structure of the device may be formed by a substrate on or in which the exposed functional structure is formed, and the at least one anchoring mechanism may be formed by the substrate or by an insulating layer such as e.g. an oxide layer, of the substrate. In embodiments of the first aspect of the invention, at least one anchoring mechanism might have a V-shaped groove at its surface. As an additional advantage, the groove in the anchoring mechanism ensures that the protection structure will break off easily and also at the correct position.

In embodiments of the first aspect of the invention, at least one anchoring mechanism might have a geometry having V-shaped notches on both sides. As an additional advantage, the V-shaped notches on both sides reduce the stress needed to break the anchoring mechanism.

In embodiments of the first aspect of the invention, at least one anchoring mechanism might have a thinner and/or weaker material composition than the rest of the device parts due to other material inclusions or due to the presence of dopants locally altering the mechanical strength of the anchoring mechanism. As an additional advantage, changing the properties of the material of the anchoring mechanism will ease breaking it.

In embodiments of the first aspect of the invention, at least one anchoring mechanism may comprise any of a V-shaped groove at its surface, V-shaped notches on both or all sides or the at least one anchoring mechanism may have a thinner and/or weaker material composition than the rest of the device, or a combination thereof.

In embodiments of the first aspect of the invention, the device further comprises electrical connections for connecting the micromachined device to the package. In such embodiments, the device may be an electronic excitation or recording device and the package may contain electronic circuitry for driving excitation or recording structures located on the exposed functional structure, such as e.g. electrodes.

In embodiments of the first aspect of the invention, the micromachined device, for example the exposed functional structure thereof, comprises integrated circuit components such as sensors and/or actuators. Typically, integrated circuit components such as sensors and actuators are sensitive devices which preferably should only be exposed just before usage. In embodiments of the first aspect of the invention, the thickness of the exposed functional structure might be substantially thinner than the thickness of the protection structure. For an exposed functional structure lying in a plane, the thickness of the exposed functional structure is defined in a direction perpendicular to the plane. As an additional advantage, a protection structure thicker than the exposed functional structure offers better protection for thin exposed functional structures such as very thin devices for implantation purposes, such as for example micromachined neural implants. A device according to embodiments of the first aspect of the invention may further comprise a passivation layer, such as for example a biocompatible passivation layer. An advantage of such passivation layer is that the exposed functional structure may be shielded from degrading contamination. As an additional advantage, a biocompatible passivation layer ensures that the device is suitable for implanting it in living tissue. The passivation layer ensures no contact between possible toxic materials and the tissue wherein the device is inserted.

In particular embodiments of the invention, the exposed functional structure might be the shank of a neural implant for implantation purposes in living tissue.

In a second aspect, the present invention provides a method for fabricating a device as described in the first aspect of the invention. A method according to embodiments of the second aspect of the present invention comprises the following steps:

providing a substrate;

defining a micromachined device in the substrate, the micromachined device comprising an unexposed functional structure for being packaged and an exposed functional structure for being externally accessible;

Patterning at least one deep trench in the substrate, thereby defining an area of the exposed functional structure and an area of a protection structure, wherein the protection structure is attached to the micromachined device via at least one anchoring mechanism and is arranged for protecting the exposed functional structure from damage by physical contact;

- thinning the backside of the substrate to a desired thickness;

mounting the unexposed functional structure of the micromachined device on a package.

It is an advantage of embodiments of the second aspect of the present invention that the method provides a packaged device, where part of the micromachined device, more particularly an exposed functional structure, is provided with, e.g. surrounded by, a protection structure. The protection structure may be for mechanically protecting that exposed functional structure from breakage and/or for protecting that functional structure against damage by physical contact by touching it, for example accidentally.

It is an advantage of embodiments of the present invention that the manufacturing of the protection structure by micromachining as in accordance with embodiments of the present invention does not involve additional processing steps, thereby having the lowest possible impact on the final device price. In embodiments of the second aspect of the invention, the area of the protection structure may be defined so that the protection structure is substantially surrounding the exposed functional structure in order to provide optimal protection. With "substantially surrounding" is meant that the protection structure surrounds the exposed functional structure over 75% or more, for example 80% or more, such as e.g. 90% or more of the circumference of the exposed functional structure. As an additional advantage, the exposed functional structure is then as much as possible protected by the protection structure. This is advantageous for e.g. probes or micro-needles whereby a U-shaped protection structure may be created for protecting the probes or micro-needles.

In embodiments of the second aspect of the invention, the substrate comprises an insulating layer, such as e.g. an oxide layer. In alternative embodiments, an insulating layer, such as e.g. an oxide layer, may be deposited on the substrate. Such insulating layer, e.g. oxide layer, may be used as a stopping layer during device manufacturing, more particularly during thinning of the backside of the substrate. As an advantage, the insulating layer, e.g. oxide layer, may be used as a stopping layer for removing material. In particular embodiments of the second aspect of the present invention, thinning of the backside of the substrate may comprise thinning the backside of the substrate underneath the area of the exposed functional structure of the micromachined device to a desired thickness. Thinning the backside of the substrate may comprise, but preferably does not comprise, thinning the backside of the substrate underneath the area of the protection structure. This way, the thickness of the exposed functional structure can be fabricated thinner than the thickness of the protection structure. As an additional advantage, this delivers better protection for the exposed functional structure.

In embodiments of the invention, the insulating layer, e.g. oxide layer, may be used as an anchoring mechanism for attaching the protection structure to the micromachined device. In use, the insulating layer, e.g. oxide layer, may be broken at the location where it connects the protection structure to the micromachined device, so as to remove the protection structure from the micromachined device.

In embodiments of the second aspect of the invention, the method further comprises a step of mounting the device to a carrier before thinning the backside of the substrate and separating the carrier from the device after thinning. As an additional advantage, this eases the thinning of the device by e.g. grinding. Deep trenches other than the deep trenches defining the area of the exposed functional structure and the area of the protection structure, but in particular embodiments patterned at the same time, are separating individual devices across the wafer. To prevent scattering of the devices while performing the thinning process e.g. by grinding, the devices need to be fixed to a carrier, such as for example a tape, to facilitate the thinning process, e.g. grinding process.

In embodiments of the second aspect of the invention, the carrier is mounted to the device with a glue. To remove the device from the carrier, e.g. tape, the glue may be dissolved using a suitable solvent or its adhesion may be reduced, for example by exposing it to UV light.

In embodiments of the second aspect of the invention, the method further comprises a step of patterning a V-shaped groove in the at least one anchoring mechanism or patterning V-shaped notches on both sides or changing the material properties of the at least one anchoring mechanism by locally doping the at least on anchoring mechanism or a combination of two or more of the above. In embodiments of the second aspect of the invention, the method further comprises a step of depositing a biocompatible layer onto at least part of the micromachined device, such as onto at least part of the exposed functional structure, e.g. at least onto a high aspect ratio part thereof.

Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims.

For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described herein above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

The above and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

Brief Description of the Drawings

All figures are intended to illustrate some aspects and preferred embodiments. The figures are depicted in a simplified way for reason of clarity. Not all alternatives and options are shown and therefore the invention is not limited to the content of the given drawings. Like numerals are employed to reference like parts in the different figures. The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 illustrates a micromachined device according to embodiments of the invention, comprising an exposed functional structure surrounded by a temporary protection structure after packaging the micromachined device into a final device. The part of the micromachined device that is not protected by the packaging is referred to as "exposed functional structure".

FIG. 2A- FIG. 2E illustrate different processing steps to provide a temporary protection structure around an exposed functional structure and final packaging of the micromachined device according to embodiments of the invention. FIG. 3 illustrates a neural implant device according to embodiments of the present invention, having its shank protected by a U-shaped protection structure while its wider end is fixed on the edge of a printed circuit board (exterior package).

FIG. 4 illustrates a dry etch pattern that may be used to define at the same time the outline of the shank of a neural implant device and its substantially surrounding U-shaped (temporary) protection structure, according to embodiments of the invention.

FIG. 5A illustrates a top view of a neural implant having a temporary protection structure according to embodiments of the invention, and FIG. 5B illustrates a side view of the device shown in FIG. 5A after applying a vertical force onto the temporary protection structure in order to remove it from the neural implant. FIG. 6A and FIG. 6B illustrate a 3D view and a side view, respectively, of a neural implant according to embodiments of the invention with a protection structure thicker than the shaft. The side view of FIG. 6B illustrates how during the protection structure removal, one can notice the much thinner shaft compared to the protection structure and the packaged part (fixed on a printed circuit board) of the neural implant. FIG. 7A illustrates a 3D top view of a neural implant according to embodiments of the invention having a temporary protection structure onto which extra material is deposited, said extra material being present only on top and bottom of the protection area and not on the area of the functional structure. FIG. 7B illustrates how during the protection structure removal one can notice this thickness difference. FIG. 8 is a photograph of a packaged neural implant based on the design shown in FIG. 3 with discernible information provided on its U-shaped temporary protection structure.

FIG. 9 illustrates in top view the deep semiconductor, e.g. silicon, etch pattern with, as an example only, realistic dimensions of the neural implant shown in FIG. 8 and the design view shown in FIG. 3. Exemplary notch design and precise dimensions of the anchoring mechanism are also shown.

FIG. 10 illustrates a top view of a neuroprobe device having a temporary protection structure according to embodiments of the present invention onto which extra material is deposited.

FIG. 11 illustrates a device comprising a buried sacrificial layer which is built into the substrate itself or deposited onto the substrate before fabrication of the device. The layer is used as a stopping layer for thinning a device. It also can reinforce the anchorage between the protection structure and the exposed functional structure.

Any reference signs in the claims shall not be construed as limiting the scope. Detailed description of illustrative embodiments of the Invention

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention. Where dimensions are illustrated, this is by way of example, for one single set of embodiments only. It is not intended to limit the present invention to the dimensions given in these examples.

Moreover, the term top, bottom and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the preferred embodiments described herein are capable of operation in other orientations than described or illustrated herein. It is to be noticed that the term "comprising", used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments. Similarly it should be appreciated that in the description of exemplary preferred embodiments, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

In the description provided herein, numerous specific details are set forth. However, it is understood that preferred embodiments may be practiced without these specific details. In other instances, well- known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

Where in the context of the present invention reference is made to micro-machined devices or to micro-engineered devices, reference is made to devices with micro scale features to micron level tolerances, including microelectromechanical systems (MEMS). Both terms micro-machined and micro-engineered are supposed to mean the same, and can be used for one another. Where in embodiments of the present invention reference is made to packaging, reference is made to enclosures and protective features built into the product. Such packaging may be obtained by means of a wide variety of technologies as known by a person skilled in the art. Examples include, but are not limited thereto, ceramic packages, metal packages, plastic packages, encapsulation. Where in embodiments of the present invention reference is made to a functional structure, a structure is meant which is a part of the micromachined device that fulfils some function necessary for the correct use of the full device. This means that no part of the functional structure can be disposed, broken or damaged without compromising the partial or complete correct function of the full device. A micromachined device according to embodiments of the present invention comprises an exposed functional structure and an unexposed functional structure. The unexposed functional structure is that part of the micromachined device that is protected by the packaging. The exposed functional structure is any part of the micromachined device that is not protected by the packaging. This can be either because it extends outside the package or because the package provides only partial coverage. The protection structure can also have specific functions (electrical testing, display, labels) but its removal does not compromise the correct function for which the device was built.

Where in embodiments of the present invention reference is made to an externally accessible exposed functional structure, reference is made to a device part that can be physically contacted, e.g. by touching.

Where in embodiments of the present invention reference is made to an anchoring mechanism, any suitable type of connection between a functional structure and a protection structure is meant to be included. The anchoring mechanism may include a single anchor point, a plurality of distributed anchor points, at least one anchor region, or an anchor layer.

The invention will now be described by a detailed description of several preferred embodiments. It is clear that other preferred embodiments can be configured according to the knowledge of persons skilled in the art without departing from the true spirit or technical teaching of the invention as defined by the appended claims.

It is an object of embodiments of the present invention to provide a method for temporarily providing a protection structure for at least a part or a functional area of a micromachined device. Said protection structure may be in particular beneficial for exposed functional structures (devices) or parts thereof having high aspect ratio dimensions, such as for example neural implants manufactured based on semiconductor, e.g. silicon, technology processing techniques. It is an advantage of embodiments of the present invention that a protection structure for at least part of a micromachined device or an exposed functional structure of a micromachined device (e.g. the shaft of a semiconductor, e.g. silicon, based neural implant device) is provided such that said part is protected and not damaged and/or touched during shipping and any further manipulation. It is a further advantage of embodiments of the present invention that a temporary protection structure may be provided for at least a part or an exposed functional structure of a micromachined device in an easy to implement process which introduces few or even almost no extra processing steps to a standard fabrication process of the micromachined device.

It is an advantage of embodiments of the present invention that a temporary protection structure may be provided for at least a part or an exposed functional structure of a micromachined device which may be manufactured at the same time as the micromachined device itself.

It is a further advantage of embodiments of the present invention that the temporary protection structure may be easily and manually (acceptable size) removed by an end-user. This puts particular constraints on the size of the protection structure. Furthermore, it is an advantage of embodiments of the present invention that the size of the protection structure allows application of eye visible and discernable labels for extra information about the structure (device) itself, a feature particularly useful when the size of the micromachined device is so small that no eye visible marking could be fitted anywhere on its surface.

It is a further advantage of embodiments of the present invention that the price impact of the temporary protection structure is negligible since the protection structure according to embodiments of the present invention is using substrate (e.g. wafer) area that may not be used for fabricating another device (geometrical limitations) in said substrate area. In case said substrate area would be available for device fabrication then a trade-off has to be made between this lost substrate (wafer) area and the higher chance of the device getting damaged during manipulation. In a first aspect, embodiments of the invention provide a device having a temporarily and disposable (removable) protection structure around at least part of a micromachined device or around an exposed functional structure of said micromachined device. Said protection structure is preferably manufactured at the same time as the micromachined device itself (at wafer level) and offers mechanical protection during packaging, shipping and manipulation. Said protection structure is having at least one anchoring mechanism to the micromachined device itself. The at least one anchoring mechanism may be manufactured simultaneously with the micromachined device itself (wafer level processed) and is strong enough for normal manipulation hazards. However, the one or more anchoring mechanisms can easily break when manipulated in a specific way, so as to remove the protection structure from the micromachined device, thus freeing the exposed functional structure for further use. According to particular embodiments the micromachined device is a semiconductor, e.g. silicon technology, micro-machined device having or comprising parts having high aspect ratio dimensions. Said high aspect ratio dimension may have one dimension 100 times or more bigger than the other two dimensions (for example L = few centimeters, H and W = few micrometers).

According to embodiments, the micromachined device may have a fragile part e.g. a part with high aspect ratio dimensions which needs to be protected, such as e.g. a shaft (implanted part) of a neural implant device. Semiconductor, e.g. silicon, manufactured neural implant shafts typically have a width around 50μιη to 200μιη and a thickness from 15μιη to about ΙΟΟμιη or 200μιη but with lengths ranging from few mm (in general 2 or 3 mm) up to a few cm (in general l-3cm). FIG. 9 illustrates in top view the deep semiconductor, e.g. silicon, etch pattern of one example embodiment, with realistic dimensions of the neural implant shown in FIG. 8.

According to embodiments of the present invention, the micromachined device itself may further comprise active (sub)devices such as integrated circuit components, e.g. sensors and/or actuators built with semiconductor, e.g. Si, compatible technology. The micromachined device may need some part thereof to be exposed to the environment only during its use. Generally this exposed part is mechanically sensitive and even a slight touch could damage it or deteriorate the performance of the functional structure(or the performance of the device as a whole). According to particular embodiments of the present invention, the micromachined device may comprise or may be the implantable shaft of a neural implant for electrical stimulation and recording. The micromachined device may have insulated conductive, e.g. metal, lines and exposed conductive, e.g. metal, areas (referred to as electrodes) on its front side, said conductive lines connecting electrodes placed near the tip of the micromachined device to a wire bonding area from where the electrical signals recorded by the tip will be transferred to some external equipment. In other words, said micromachined device is, in these particular embodiments, built to record or to send electrical signals from or to the brain with its electrodes (exposed conductive areas at its tip).

According to embodiments of the present invention, the micromachined device may further comprise a passivation layer on top in order to protect the device from mechanical or chemical aggressions during use. Said passivation layer may for example be selected from Si0₂, SiN, various polymers, oxide layers, or combinations of these. Said passivation layer may be a biocompatible insulating polymer e.g. parylene. Said passivation layer may be removed in some areas if needed but some devices/sensors might not need this removal in order to function correctly.

According to embodiments of the present invention, the protection structure may have a thickness which is substantially equal or preferably greater than (at least in the same order of) the thickness of the exposed functional structure (or in the same order of the whole final device). In case the thickness of the final device is for example ΙΟΟμιη, the thickness of the protection structure may be around ΙΟΟμιη as well.

According to embodiments of the present invention, the protection structure may have a thickness which is thicker than the thickness of the exposed functional structure. In case the thickness of the final device is ΙΟΟμιη, the thickness of the protection structure may be between ΙΟΟμιη and 725μιη (corresponding to the thickness of a standard 8 inch Si substrate). The difference in thickness between the protection structure and the sensitive area of the exposed functional structure of the device may be easily achieved by combining trench patterning and a selective backside etch of the sensitive area of the device that needs to be protected. A thicker protection structure thickness compared to the thickness of the exposed functional structure to be protected may be also achieved by depositing and selective patterning of material on the front side and possibly on the backside of the protection structure. As an example, polymer patterns up to 60μιη thick can be easily achieved by using a spin-on technique (spinning), for example a polyimide film. This may lead to a protection structure that is up to 120μιη thicker than the device part to be protected. According to embodiments of the present invention, the anchoring mechanism(s) have to be hard enough to maintain the protection structure in place during manufacturing, handling, shipping, but weak enough in order to brake them when the protection structure is manipulated in a certain way (e.g. prior to use, for removal of the protection structure).

According to embodiments of the present invention, the anchoring mechanism(s) may be situated on an opposite side of the area where the user will apply the force needed to remove the protection structure e.g. at the extremities of the functional area in order to provide good leverage and higher stress on the anchoring mechanism(s) during the protection structure removal.

According to embodiments of the present invention, the anchoring mechanism(s) may have a specific geometry that concentrates stress e.g. a connection between the functional structure and the protection structure having V-shaped notches on both sides which is such that under stress, the breakage will occur at this location rather than in other areas where the stress will not increase enough to lead to breakage when the protection is mechanically solicited during its removal. According to embodiments of the present invention, the anchoring mechanism(s) may be thinner and /or weaker than the rest of the protection structure. The anchoring mechanism(s) may be weaker due to a difference in thickness, the lack of the passivation layer, and/or a difference in composition e.g. due to the presence of dopants locally altering the mechanical strength of the anchoring mechanism. They may also be made of a different material that the rest of the protection structure.

According to embodiments of the present invention, there may be at least 1 anchoring mechanism. However, the number of anchoring mechanisms may be extended to more individual anchoring mechanisms.

According to embodiments of the present invention, there may be more than one protection structure around different parts of a same device, thereby protecting different parts of a micromachined device or different exposed functional structures of a same device. During use, said different protection structures may be removed separately or at the same time. Also, each of these protection structures may have one or more anchoring mechanisms.

According to embodiments of the present invention, the at least one micromachined device of the device may be coated with a passivation layer while the area defining the anchoring mechanism(s) is not. This may be required if the passivation layer is too strong and could prevent the anchoring mechanisms to easily brake during removal of the protection structure.

In a second aspect, embodiments of the present invention provide a method for solving the problem of temporarily protecting at least a part of a device or an exposed functional structure of a device (e.g. micro-machined devices), thereby avoiding damage to said devices or areas during handling before actual use or further manipulation of said device. The problem is solved in accordance with embodiments of the present invention by providing a protection structure around at least part of a micromachined device of the device, whereby said protection structure is preferably manufactured at the same time as the micromachined device itself (at wafer level) and thereby offers mechanical protection during packaging, shipping and manipulation. Said device protection is having at least one anchoring mechanism to the micromachined device itself that is processed simultaneously or during the processing of the micromachined device (in case of semiconductor based devices during wafer level processing) and that is strong enough for normal manipulation hazards but that can easily brake when manipulated in a specific way. According to embodiments of the present invention, a method is provided for temporarily providing a protection structure for at least a part or an exposed functional structure of a device such as for example a micro-machined device. Said method comprises at least the steps of: Providing a substrate,

Defining a micromachined device on the front side of said substrate,

Optionally providing a passivation layer at least on said micromachined device,

Patterning first deep trenches in the front side of the substrate, thereby defining boundaries of the area of an exposed functional structure of the micromachined device and at the same time patterning additional (second) deep trenches defining boundaries of an area of a protection structure around at least part of said exposed functional structure, wherein said additional deep trenches are connected to said first deep trenches by means of anchoring mechanisms defined in the substrate,

- Releasing the area of the exposed functional structure along with the area of the protection structure from the rest of the substrate.

FIG. 2A- FIG. 2E illustrate different processing steps to provide a temporary protection structure around an exposed functional structure and final packaging of the micromachined device. The layer stacks are drawn as cross sectional views along the dashed line of the schematic top view of FIG. 1. On the surface of a substrate 200 at least one micromachined device 101, comprising at least one exposed functional structure 110 and at least one unexposed functional structure 111, is defined (see FIG. 2A). The unexposed functional structures 111 may be embedded in a final device packaging 102 while exposed functional structures 110 may be part of a sensitive active area that needs to be exposed during the device use. The protection structure 103 around this sensitive area of the exposed functional structure 110 is defined by first trenches 201 in the substrate 200. These first trenches 201 leave one or more anchoring mechanisms 104, in the embodiment illustrated two anchoring mechanisms 104, bridging some part of the protection structure 103 to the micromachined device 101. Second trenches 108 defining the outline of the whole device (micromachined device 101 and protection structure 103) can be patterned in the same process step (see FIG. 2B). In the case of device release by wafer thinning, the device side (front side) of the wafer is attached to, e.g. glued on, a carrier wafer 205 with temporary attachment means, e.g. glue 206 (see FIG. 2C). The substrate 200 is then thinned from the backside, for example by grinding. Once the backside of the substrate has been thinned (see FIG. 2D) to the desired thickness (less than or equal to the final device thickness) the device 100 including its protection structure 103 are removed from the carrier wafer 205 and the remaining substrate 106. The device 100 including the protection structure 103 is mounted on a device package 102 (see FIG. 2E).

According to embodiments of the present invention, the substrate 200 may be a semiconductor substrate such as a semiconductor wafer. Examples of substrates which may be used in embodiments of the present invention are, for example, single crystal or polycrystalline Si, single crystal or poly- crystalline Ge, glass, quartz, polymer, etc.

According to embodiments of the present invention, the area of the micromachined device 101, e.g. the area of the exposed functional structure 110, may comprise integrated circuit components such as sensors and/or actuators built with semiconductor, e.g. Si, compatible technology that need some part of the micromachined device to be exposed to the environment only during its use. Generally this exposed part is mechanically sensitive and even a slight touch during packaging, shipping or use could damage it or deteriorate the performance of the micromachined device 101.

According to embodiments of the present invention, the micromachined device 101 (with or without active devices) may have a fragile part e.g. a part with high aspect ratio dimensions which needs to be protected, also called the exposed functional structure 110, such as for example the tip and shaft of a neural implant. Semiconductor, e.g. silicon, technology based neural implant shafts typically are around 200μιη wide, ΙΟΟμιη or less thick and have lengths ranging from a few mm (in general 2 or 3 mm) up to a few cm (in general l-3cm). According to particular embodiments of the present invention, the exposed functional structure 110 may comprise the tip and shaft of a neural implant and the front side of the substrate 200 may have patterned conductive, e.g. metal, lines, said conductive lines connecting the tip of the future probe shaft to a wire bonding area from where electrical signals recorded by the tip will be transferred to some external equipment. In other words, said active device is built to record electrical signals from the brain with its exposed conductive areas at its tip.

FIG. 3 illustrates a neural implant device 300 having its shank, a high aspect ratio part 110 of the micromachined device 101, protected by a U-shaped protection structure 103 while its wider end 111 is fixed on the edge of a printed circuit board 102 (exterior package). In this embodiment, the anchoring mechanisms 104 connect the protection structure 103 only to the wider part of the micromachined device 101 of the neural implant device and not to its fragile shank 101. Furthermore the location of the anchoring mechanisms 104 coincides with the edge of the package 102 making this area subject to further stress concentration during the brake of the protection structure 103 (when a vertical force is applied on the protection structure around the tip of the neural implant shaft).

According to embodiments of the present invention, the deposition of a passivation layer may comprise the deposition of a layer selected from Si0₂, SiN, various polymers, oxide layers, or combinations of these. Said passivation layer may be a biocompatible polymer e.g. parylene. The protection layer(s) is (are) optional but generally recommended if the design allows it. They may be put in place to protect the micromachined device 101 of the device 100 from chemical or very light mechanical aggressions during use. Said passivation layer may be removed in some areas if needed but some devices/sensors might not need this removal in order to function.

According to embodiments of the present invention, the passivation layer may render the anchoring mechanisms 104 of the protection structure 103 too strong. If this danger exists, the passivation layer may be removed locally in/around those areas by any convenient dry or wet etch method. In case the exposed functional structure 110 is part of a neural implant, the passivation layer may have to be removed by e.g. using state of the art dry or wet etch techniques on 3 different areas: firstly on the (conductive, e.g. metal) tip contact areas of the im plant since most neural implant devices for electrical recording and stimulation need some conductive areas in direct contact with the brain tissue, secondly on the wire bonding pads and thirdly on the areas on top of the anchoring mechanisms 104 to be defined.

According to embodiments of the present invention, the first deep trenches 201 for cutting out said micromachined device 101 of the device and the additional deep trenches 108 defining an area around at least part of said micromachined device 101 are making contact to each other by means of at least one anchoring mechanism 104 being defined in the substrate 200. The trench patterning is typically performed on the front-side of the substrate but can be also performed on the backside or throughout the whole thickness of the substrate if its thickness or means of patterning allows it. Said anchoring mechanism(s) 104 are bridges connecting the protection structure 103 to the body of the device 100 and can be obtained by various means. The simplest way is not to perform any substrate etch or cut in that area. Other means could be under-etching the regions defining the anchoring mechanisms 104 to a depth in the substrate 200 smaller than the depth of the rest of the deep trenches 201, 108 or etching to the full depth of the deep trenches 201, 108 then later creating a bridge in this particular area with some other material. According to embodiments of the present invention, the deep trenches 201, 108 may have a depth in the substrate 200 which is substantially equal to or at least in the same order of the thickness of the final device. In case a final device thickness of ΙΟΟμιη is to be obtained only by backside thinning, the depth of the front side deep trenches has to be ΙΟΟμιη or more. However, if the exposed functional structure 110 of the device 100 that has to be protected and its protection structure 103 are defined by a combination of front and backside etch or cut of the substrate 200 or involve sacrificial layers to be removed on the bottom of the trenches 201, 108, the depth of each individual trench can be lower than the active area device thickness depending on the application, substrate used, process flow and final device dimensions. According to embodiments of the present invention, the trenches 201, 108 may be fabricated using any state of the art dry and/or wet etch, laser ablation dicing or a mix of these techniques. What is important is to maintain at least one bridge between the micromachined device 101 and the protection structure 103 to define the anchoring mechanisms 104. The at least one bridge may also be a thin membrane connecting the protection structure 103 to the micromachined device 101. This membrane may be very thin allowing it to be broken easily in order to disconnect the protection structure 103 from the micromachined device 101. In embodiments of the invention, the membrane is an oxide material.

FIG. 4 illustrates a dry etch pattern that has been used to define at the same time the outline of the exposed functional structure 110, e.g. shank, of a micromachined device 101 of a silicon based neural implant device and its surrounding U-shaped protection structure 103. The shank, being the long rectangular area with a sharp tip at one end, is the most fragile part of this device and is to be exposed during its use (implantation of the shank into the brain tissue). The wider area on the side opposite to the tip is more robust and since this is partially protected by the final packaging 102 it does not require additional protection. The U-shaped protection structure 103 defined around the shank represents the temporary protection connected to the wide and more robust part of the neuroprobe device by two anchoring mechanisms 104.

According to embodiments of the present invention, the patterning of the deep trenches 201 in the substrate 200 defining the micromachined device 101 and suitable for cutting out said micromachined device 101 and the patterning of the additional (second) deep trenches 108 defining a protection structure 103 around at least part of said functional structure 101 and suitable for cutting out said protection structure 103 may be performed in one or more separate etching steps.

According to embodiments of the present invention, the depths of the trenches 201, 108 defining the protection structure 103 and the functional structure 101 may be different. This may be desired in a process where a thicker (and hence stronger) protection structure 103 is desired compared to the exposed functional structure 110 final thickness. Besides the stronger mechanical resistance, thicker protection structures 103 have the advantage to bring the exposed functional structure surface beneath the outer surface of the overall device, making them more difficult to be accidentally touched, hence providing better protection. The difference in thickness between the two areas could be achieved by selective thinning of the exposed functional structure 110 (substrate or sacrificial layer etch) or by selective thickening of the protection structure 103 (deposition of additional layers). FIGs. 6A and 6B and FIGs. 7A and 7B illustrate how these two approaches can be applied to the neural implant device shown in FIG. 3. FIG. 6A and FIG. 6B illustrate a 3D view and a side view, respectively, of a neural implant according to embodiments of the invention with a protection structure 103 thicker than the shaft 110. The side view of FIG. 6 B illustrates how during the protection structure removal, one can notice the much thinner shaft 110 compared to the protection structure 103 and the packaged part 111 (fixed on a printed circuit board) of the neural implant. FIG. 7A illustrates a 3D top view of a neural implant according to embodiments of the invention having a temporary protection structure 103 onto which extra material 107 is deposited, said extra material 107 being present on top and bottom of the protection structure 103 and not on the area of the exposed functional structure 110. FIG. 7B illustrates how during the protection structure removal one can notice this thickness difference. In alternative embodiments, not illustrated in the drawings, extra material 107 for thickening the protection structure 103 could be provided at the top or at the bottom thereof only, instead of at both sides.

According to embodiments of the present invention, the protection structure 103 comprises an area suitable for handling before packaging and another (or the same area) where the user can apply a force in order to remove the protection structure 103 by breaking its anchoring mechanism 104 from the rest of the device 100 (release of the functional structure 101). In other words the protection structure 103 according to embodiments of the invention may have three features, one feature suitable for protection of a fragile part of the functional structure 101 (e.g. shank of the neuroprobe), a second one of being suitable for easy handling of the overall device 100 prior to packaging and a third, allowing to be easily removed by applying a force in order to break the anchoring mechanisms 104 to release the functional structure 101.

According to embodiments of the present invention, the anchoring mechanism(s) 104 need to be hard enough to maintain the protection structure 103 in place but weak enough in order to brake when the protection structure 103 is manipulated in a certain way (e.g. prior to use) without damaging the rest of the device 100. In order to achieve this dual function one may follow one or more of these guidelines:

- The anchoring mechanism(s) 104 may be placed opposite to the area where the user will apply the force necessary to remove the protection structure 103 in order to provide good leverage and higher stress on the anchoring mechanism(s)104.

- The anchoring mechanism(s) 104 may have a specific geometry that concentrates stress e.g. a connection between the functional structure 101 and the protection structure 103 having V-shaped notches on both sides which is such that under strain the breakage will occur at that location rather than in other areas where the stress will not increase enough to lead to breakage when the protection is mechanically solicited during its removal.

According to embodiments of the present invention, the anchoring mechanism(s) 104 may be further weakened by locally removing part of the passivation layer. According to embodiments of the present invention, the anchoring mechanism(s) 104 may be further weakened by reducing their thickness by a local (semiconductor, e.g. Si) etch that makes them thinner compared to the rest of the device parts.

According to embodiments of the present invention, the anchoring mechanism(s) 104 may be further weakened by doping the substrate 200 (e.g. silicon) in order to locally alter its mechanical strength. According to embodiments of the present invention, there may be at least 1 anchoring mechanism 104. However, the number of anchoring mechanisms 104 may be extended to more than one discrete anchoring mechanisms 104.

According to embodiments of the present invention, there may be more than one protection structure 103 around different parts of a same device 100 thereby protecting different parts of the same device 100. Said different protection structures 103 may be removed separately or at the same time. Also, each of these protection structures may have one or more anchoring mechanisms 104.

According to embodiments of the present invention, the release of the device 100 including its one or more protection structures may be done by etching the backside of the substrate 200 if the trench patterns 201, 108 defined on the front side of the substrate 200 are less deep than the thickness of the substrate. The backside etch has to be deep enough such that the bottom of the front side trenches is reached.

According to embodiments of the present invention, the release of the micromachined device 101 connected to the protection structure(s) 103 from the rest of the substrate 200 may be achieved by backside grinding of the substrate. The device wafer may therefore be flipped upside down with the front side comprising the deep trenches 201, 108 being attached, e.g. glued, to a carrier wafer 205, e.g. tape. The substrate 200 is then thinned, e.g. grinded, on its backside reducing its thickness until the bottom of the front-side deep trenches (grooves) 201, 108 becomes visible. The grooves 108 are then separating the individual devices 100 across the wafer and they all stay together only because everything is attached, e.g. glued, onto the carrier wafer 205. In a next step the carrier wafer 205 is removed in order to release the individual devices 100. The removal of the carrier wafer 205 may be done by placing the assembly device substrate 200 and carrier wafer 205 in a solution that dissolves the bonding material, e.g. glue, and hence releases the thin devices 100 comprising protection structures 103 attached to the micromachined device 101 by means of the anchoring mechanisms 104.

According to embodiments of the present invention, the release of the micromachined device 101 connected to the protection structures(s) 103 from the rest of the substrate 200 may be done during the step of forming (etching, dicing, laser ablation,...) the deep trenches 108 thereby requiring no extra processing step(s) if the deep trenches (grooves) 108 are deep enough such that said deep trenches 108 basically cut through the whole thickness of the substrate.

According to embodiments of the present invention, if the desired device 100 and its protection structure 103 are thinner than the substrate 200, they can be detached from this substrate 200 by removal (typically wet or dry etch) of a buried sacrificial layer. This layer may be either built in the substrate 200 itself (for example a silicon oxide layer in the case of SOI wafers) or may be deposited on the substrate 200 before the fabrication of the rest of the device. In either case, the trenches 108 defining the outline of the device 100 and its protection structure(s) 103 have to be deep enough to reach the buried sacrificial layer. This approach has the advantage that it does not require any substrate backside thinning.

FIG. 11 illustrates a device comprising a buried sacrificial layer 105 which is built into the substrate itself or deposited onto the substrate before fabrication of the device. The protection structure 103 protects the micromachined device 101, or at least an exposed functional structure 110 thereof. The buried sacrificial layer 105 is a thin layer which can function as an anchoring mechanism 104, connecting the protection structure 103 to the micromachined device 101. The buried sacrificial layer can e.g. be an oxide layer.

According to embodiments of the present invention, the release of the micromachined device 101 connected to the protection structure(s) 103 from the rest of the substrate may be done by a combination of foregoing processes.

According to embodiments of the present invention, after the release of the device and its protection structure(s) 103 from the substrate it is either possible to directly use the device or to mount it in an additional package 102, depending on the device and application. Unless the device has a wireless connection and does not require external power to function, the use of a package 102 may be necessary. This package 102 may provide power and connectivity between the device 100 and external equipment and can be also designed to protect certain areas of the device 100 that don't need to be exposed during its use. Typically the packages 102 are made out of ceramic, metal or plastic material, having some kind of standard connector to external equipment and are electrically connected to the micromachined device 101 of the device 100 by flip chip or wire bonding. The connection area is typically sealed by a cap or a polymer material suck epoxy.

According to embodiments of the present invention, the temporary protection structure 103 may be manually removed by the end user simply by breaking it apart from the rest of the device without damaging the micromachined device 101. FIG. 5A illustrates a top view of a neuroprobe device having a temporary protection structure 103 along a high aspect ratio part of a micromachined device 101 which comprises fragile and high aspect ratio parts. FIG. 5B illustrates a side view of the device shown in FIG. 5A after applying a vertical force in order to remove the temporary protection structure 103 from the micromachined device 101.

According to embodiments of the present invention, the temporary protection structure 103 can withstand stronger horizontal forces than vertical forces, i.e. stronger forces in a plane parallel to a major surface of the substrate 200 than in a direction perpendicular to that plane. The vertical protection is much weaker than the horizontal protection since the width of the protection structure 103 and anchoring mechanisms 104 is few times higher in horizontal direction. The vertical direction is the direction in which the user needs to apply force in order to break the anchoring mechanisms 104. Superior vertical protection may be easily achieved by adding extra process steps that would lead to a protection structure 103 and anchoring mechanisms 104 thicker than the active sensitive part of the device 100. One possible combination may be that after the substrate thinning to the desired protection structure 103 thickness one can perform a dry or wet etch only of the backside of the micromachined device 101. Another solution may be to deposit thick layers of material 107 on top and bottom of the protection structure 103 but not on the micromachined device 101. FIG. 10 and FIG. 7A illustrate top views of a neuroprobe device 100 having a temporary protection structure 103 (along its fragile and high aspect ratio parts) on which extra material 107 is deposited, said extra material being present only on top and bottom of the protection structure 103 and not on the micromachined device 101. FIG. 7B illustrates how one can notice this thickness difference during the protection brake.

According to embodiments of the present invention, the temporary protection structure 103 may comprise on its surface eye visible and discernable labels 109 since the size of said temporary protection structure 103 may be actually bigger than the micromachined device 101 of the device or the exposed functional structure 110 thereof. This makes it possible to include information about the device 100 or the exposed functional structure 110 thereof which would otherwise be difficult to be included on the small area of the device itself.

Claims

1. A device (100), comprising:

a micromachined device (101) comprising an exposed functional structure (110) and an unexposed functional structure (111);

a package (102) mounted on the unexposed functional structure (111), leaving the exposed functional structure (110) externally accessible;

a protection structure (103) for at least part of the exposed functional structure (110), attached to the micromachined device (101) via at least one anchoring mechanism (104), wherein the protection structure (103) can be detached by breaking the at least one anchoring mechanism (104).

2. A device (100) according to claim 1, wherein the protection structure (103) is formed by a substrate and wherein the at least one anchoring mechanism (104) is formed by a membrane.

3. A device (100) according to claim 2, wherein at least one anchoring mechanism (104) is formed by an insulating layer(105).

4. A device (100) according to any of the previous claims, wherein the at least one anchoring mechanism (104) comprises:

a V-shaped groove at its surface; and/or

a geometry having V-shaped notches on both sides; and/or

- a thinner and/or weaker material composition than the rest of the device parts due to other material inclusions or due to the presence of dopants locally altering the mechanical strength of the anchoring mechanism (104).

5. A device (100) according to any of the previous claims, wherein the micromachined device (101) is electrically connected to the package (102).

6. A device (100) according to any of the previous claims, wherein the micromachined device

(101) comprises integrated circuit components such as sensors and/or actuators.

7. A device (100) according to any of the previous claims, wherein a thickness of the exposed functional structure (110) is thinner than a thickness of the protection structure (103).

8. A device according to any of the previous claims, further comprising a passivation layer.

9. A device according to any of the preceding claims, wherein the exposed functional structure

(110) is a shank of a neural implant for implantation purposes in living tissue.

10. A method of fabricating a device (100) as described in claim 1, the method comprising:

providing a substrate (200); defining a micromachined device (101) in the substrate (200);

patterning deep trenches (201) in the substrate (200), thereby defining an area of an exposed functional structure (110) of the micromachined device (101) and an area of a protection structure (103) wherein the protection structure (103) is attached to the micromachined device (101) via at least one anchoring mechanism (104) and is arranged for protecting the exposed functional structure (110);

thinning the backside of the substrate to a desired thickness;

mounting an unexposed functional structure (111) of the micromachined device (101) on a package (102).

11. A method according to claim 10, wherein the substrate (200) comprises an insulating layer (105) or wherein an insulating layer (105) is deposited on the substrate (200) and wherein the insulating layer (105) is used as a stopping layer for thinning.

12. A method according to any of claims 10 or 11, wherein the backside of the substrate (200) underneath the area of the exposed functional structure (110) of the micromachined device (101) but substantially not underneath the area of the protection structure (103) is thinned to a desired thickness.

13. A method according to any of claims 10 to 12, further comprising mounting the device (100) to a carrier (205) before thinning the backside of the substrate (200) and separating the carrier (205) from the device (100).

14. A method according to any of claims 10 to 13, further comprising a step of patterning a V- shaped groove in the at least one anchoring mechanism (104) and/or patterning V-shaped notches on both sides and/or changing the material properties of the at least one anchoring mechanism (104) by locally doping the at least on anchoring mechanism (104).

15. A method according to any of claims 10 to 14, further comprising providing a passivation layer onto at least part of the micromachined device (101).