DE19638501A1 - Capillary especially micro-capillary production - Google Patents

Abstract

A capillary production method involves forming a capillary-defining groove (21) in the surface (20) of a substrate (2) and then covering the groove with a layer (3) by gas phase deposition (5). Preferably, the layer (3) is formed by a flame hydrolysis process, in which a porous SiO2-based particle layer is deposited from an inclined particle stream, and is then sintered to form a compact layer.

Description

The invention relates to a method for producing a Capillary.

For micromechanical or micro-optical components and modules le of microsystem technology are often with microcapillaries provided body made of, for example, glass or silicon does. For the transport of liquids, for example in Heat sink of a micro cooler, in the printhead of an ink jet printer or in micro atomizers, for the separation of Liquids or gases using planar microcolumn chromatographs, or for chemical or biochemical reak Micro channels become fine channels or a network of channels works. Glass capillaries can be used in sensor technology can be used as cuvettes for microspectrophotometers.

Air-filled microcapillaries, the walls of which are suitable layers can also be used as optical fibers for lasers radiation in the infrared can be used, for example, for Light guide at 10.6 µm with GeO₂ coated capillaries. Likewise, liquid-filled capillaries can be used as light guides are used, for example CCl₄ because of its high ver det constants.

Planar micro-capillary systems are usually replaced by etching zen of grooves according to the photolithographic structure definition produced. Preferred substrate material is silicon, which is available in the form of single-crystal wafers, or glass. The planar structured system is then through Application of a cover plate closed.

A frequently used connection technology for temperature-resistant Bonding is anodic bonding, in which one is oxidized Silicon wafer with a glass containing alkali ions  layer is connected. This technique is based on the presence depend on ions moving in the electric field. In addition, the materials to be joined must suffice have conductivity. It also requires the one set of a cover plate that ver is equally thick and therefore he is often undesirable applies high.

The invention specified in claim 1 has the object reasons, a particularly simple and effective method for Provide production of a capillary.

A major advantage of the method according to the invention is that there is no discreet body in the form of a lid required to cover the groove defining the capillary is.

As with the conventional method, advantageously whole systems of crossing and / or not crossing Capillaries are made by placing in the surface of the Several grooves, each defining a capillary are generated (claim 2).

It can happen that the separated from the gas phase and a groove covering layer, especially in a later one described further treatment, sinks into the groove and there due to the risk that the capillary remaining cavity in the groove is closed. Around To avoid this if possible, it is advisable to use a groove to use a greater depth than width (claim 3).

A particular advantage of the method according to the invention lies in that it's not just for the production of capillaries small clear width, but also for the production of Ka pillaren relatively large clear width between 2 µm and 100 µm is suitable.  

A layer with a layer thickness is advantageously used deposited by at least 10 µm (claim 4). At this Layer thickness ensures that the deposited layer does not tear off.

It is preferred and advantageous on the surface Abge a layer of a material based on SiO₂ divorced (claim 5). It is advisable to use a material to deposit on the basis of SiO₂, the more than 60 Mol percent of SiO₂ consists (claim 6), wherein pure SiO₂ is included.

In preferred embodiments, a material is on the Base of SiO₂ deposited, with at least one substance from the group of substances B₂O₃, P₂O₅, GeO₂, Al₂O₃, Ga₂O₃, TiO₂, ZrO₂, ZnO, MgO, As₂O₃, Sb₂O₅, Bi₂O₃, SnO₂ is doped (Claim 7).

It is favorable if the for the layer to be deposited and the surface used materials at least approximately have the same coefficient of thermal expansion (Claim 8). "Approximately" in this context means that for a given temperature fluctuation range, in which the capillaries are used, a difference between that Coefficient of thermal expansion of the surface and heat expansion coefficient of the applied layer so small is that no mechanical deformation and / or a detachment solution of the layer from the surface occurs. In other wor ten means that the surface and the surface brought layer tolerated thermomechanically.

With the specified layer materials based on SiO₂ is a surface compatible in this sense, which consists of egg Nem material from the group Si, Al₂O₃ and / or a Ma material based on SiO₂ (claim 9).  

It is useful if the layer from the gas phase in shape a porous particle layer is deposited (claim 10). This is the usual deposition process from the Gas phase, for example flame hydrolysis and CVD processes, given.

The deposited porous particle layer becomes more expedient as sintered into a compact layer (claim 11). This means for materials based on SiO₂ for example, that the layer during sintering is a layer of glass that is clear, for example.

The particle layer is advantageously in a gas atmosphere sphere sintered (claim 12).

Expediently, par particle in the form of a particle directed towards the surface stream separated from the gas phase (claim 13), wherein the Particle flow is preferably at an angle of less is directed at 45 ° to the surface (claim 14).

The layer is preferably and advantageously by means of Flame hydrolysis deposited on the surface 15). This procedure is particularly useful for separating the Layer in the form of a directed particle stream suitable.

It is appropriate to lay the layer on a gas phase deposit cooler surface (claim 16).

The method according to the invention is for advantageous manufacture development of microcapillaries for beam converters, power or lei laser, capillaries for liquid transport, for doors of gases or liquids, for chromatography columns, Chemical microreactors, for sensor technology, as cuvettes for microspectrophotometry, for light waveguide technology, as a waveguide for CO₂ laser radiation,  as a liquid-filled conductor for magneto-optical effects or nonlinear effects.

The invention is described in the following description of the figures explained in more detail by way of example. Show it:

Fig. 1 is a vertical section through a plate-shaped substrate having a surface, to be produced in the capillary,

Illustration of Fig. 2, the substrate of Fig. 1 in the same section, wherein in each case a capillary-defining grooves are provided with a vertical to the plane of the longitudinal axis in the surface of three,

Fig. 3 shows the substrate of FIG. 2 in the same sectional view, wherein on the surface a layer separated from the gas phase and covering the grooves in the form of a porous particle layer is separated, and

Fig. 4 shows the substrate of FIG. 3 in the same sectional view after sintering the deposited particle layer to compact glass.

The figures are schematic and not to scale.

The method according to the invention starts with the substrate 2 according to FIG. 1, the surface 20 of the substrate being provided for forming the capillaries to be produced.

With regard to the layer to be deposited on the surface 20 from the gas phase, the substrate 2 should consist of a material which is compatible with the material of the layer with regard to the thermomechanical properties. If the layer to be deposited consists, for example, of a material based on SiO₂₁, the substrate 2 can be made of Si, Al₂O₃ or a material based on SiO₂.

The latter materials for the substrate 2 also have the advantage that the grooves 21 (see FIGS. 2, 3 or 4) to be introduced into the surface 20 and each defining a capillary 1 can be produced by photolithography.

In Fig. 2 it is assumed that in this way three each defining a capillary 1 grooves 21 are introduced into the surface 20 , for example etched, the longitudinal axis, not shown, of which runs vertically to the plane of the drawing, so that the grooves 21 only in Cross section can be seen.

On the surface 20 containing the grooves 21 of the substrate 2 , according to the invention, a layer covering the grooves 21 is deposited from the gas phase, after which the object shown in FIG. 3 has been created, in which the deposited layer is designated by 3.

The prerequisite for this is that the surface 20 can be coated by gas phase coating. The materials specified above for the substrate 2 are suitable for this purpose.

In Fig. 3 the gas phase from which is separated is indicated at 5. In principle, all known processes, including the known CVD process and in particular the known flame hydrolysis, are suitable as processes for the deposition of layer 3 from the gas phase 5 .

Flame hydrolysis has proven to be particularly advantageous. In this method, hydrolyzable or oxidizable chemical compounds are fed in at a comparatively high concentration into a flame consisting of gas and O₂, so that an oxide particle stream 32 is generated. This particle stream 32 is preferably directed at a flat angle α to the surface 20 of typically 25 ° to 30 ° onto the comparatively cool surface 20 of a temperature of typically 200 to 300 ° C., on which the layer 3 forms in the form of a particle layer.

Because of the size of the particles 31 contained in the particle stream 32 , which is typically more than 50 nm, diffusion of the particles 31 into a stagnant gas filling of the nu 21 is difficult. Instead, there is a bridging growth, which causes a cavity 1 defining a capillary 1 to remain in the grooves 21 covered by the layer 3 .

The particle layer 3 produced in this way is porous and is distinguished by relatively good adhesion between the particles 31 , where its adhesion to the surface 20 of the substrate 2 is lower.

In a subsequent sintering process in, for example, an oven the particle layer 3 at an elevated temperature which can 3, for example 900 amounted to 1000 ° C depending on the composition of the layer is sintered to the glass-clear layer 30, which originated the the final product Performing article according to Fig. 4 .

The sintering is preferably carried out in a gas atmosphere, which is indicated at 4 in FIG. 4. The gas atmosphere 4 can consist of O₂, N₂ and / or Ar.

If the sintering takes place at the lowest possible temperature, the layer 3 only shrinks from the thickness d to a smaller thickness dl (see FIG. 4) without sinking into the grooves 21 underneath. The low adhesion of the layer 3 to the surface 20 of the substrate 2 favors lifting of the layer 3 during the shrinking process, so that the layer 3 can span over the grooves 21 .

Once the gas volume has been captured, it is retained even with further heating, provided that the thickness d of the layer 3 is only large enough to prevent the gas from diffusing out of the gas atmosphere 4 . A thickness d of a few micrometers is sufficient for this.

A certain deformation of the capillaries 1 produced and defined by the grooves 21 is observed, which is harmless and its cause on the one hand in a rounding of the inner surface of the grooves 21 under the action of the surface tension, and on the other hand in a slight sinking of the layer 3 or 30 in the grooves 21 , which can also occur due to a shrinkage of the capillary 1 when cooling.

With the method according to the invention, capillaries 1 of about 2 µm to 100 µm inside width w can be produced. As a rule, the ratio t / b between the depth t and the width b of a groove 21 should not be less than one. Cavities 1 defining cavities are retained in deep grooves 21 even if layer 3 or 30 sinks slightly into grooves 21. The deposited layer 3 should have a thickness d of at least 10 μm. If layer 3 is too thin, it tends to tear off.

It has a favorable effect if the layer 3 or 30 is adequately supported by the surface 20 of the substrate 2 . The area ratio Fg / F between the area Fg occupied by the grooves 21 and the total area F given by the surface 20 should be as small as possible less than 0.5. The area Fg is to be understood as the sum of the areas of all individual grooves 21 , the area of an individual groove 21 being multiplied by the product of its width b by its length measured vertically to the plane of the drawing.

The layer 3 or 30 preferably consists of a material based on SiO₂, which preferably consists of more than 60 mole percent SiO₂. In addition to SiO₂, layer 3 or 30 can contain, for example, the substances B₂O₃, P₂O₅, GeO₂, Al₂O₃, Ga₂O₃, TiO₂, ZrO₂, ZnO, MgO, As₂O₃, Sb₂O₅, Bi₂O₃ and / or SnO₂. SiO₂ glasses with a low proportion of animal substances are advantageous because these glasses sink less easily.

Claims (16)

1. A method for producing a capillary (1), wherein in a surface (20) of a substrate (2), the Kapil lare (1) defining the groove (21) is generated and then covered the groove (21), characterized in that that

• - The capillary ( 1 ) defining groove ( 21 ) in a coatable by means of gas phase coating surface ( 20 ) of the substrate ( 2 ) and then produced
• - A layer ( 3 , 30 ) covering the groove ( 21 ) is deposited on the surface ( 20 ) from the gas phase ( 5 ).

2. The method according to claim 1, wherein a plurality of grooves ( 21 ), each defining a capillary ( 1 ), are produced in the surface ( 20 ). 3 The method of claim 1 or 2, wherein a groove ( 21 ) with a greater depth (t) than width (b) is used. 4. The method according to any one of the preceding claims, wherein a layer ( 3 , 30 ) of a layer thickness (d) of at least 10 microns is deposited. 5. The method according to any one of the preceding claims, wherein on the surface ( 20 ), a layer ( 3 , 30 ) made of a material based on SiO₂ is deposited. 6. The method of claim 5, wherein a material on the Ba sis of SiO₂ is deposited, which is more than 60 mol% SiO₂ exists. 7. The method of claim 5 or 6, wherein a material the base of SiO₂ is deposited with at least one Substance from the group of substances TiO₂, ZrO₂, ZnO, MgO, As₂O₃, Sb₂O₅, Bi₂O₃ and / or SnO₂ is doped.   8. The method according to any one of the preceding claims, wherein the materials to be deposited for the layer ( 3 , 30 ) and the surface ( 20 ) have an at least approximately equal coefficient of thermal expansion. 9. The method according to claim 8 and 5 to 7, wherein a surface ( 20 ) is used, which consists of a material from the material group Si, Al₂O₃ and / or material based on SiO₂. 10. The method according to any one of the preceding claims, wherein the layer from the gas phase ( 5 ) in the form of a porous particle layer ( 3 ) is deposited. 11. The method according to claim 10, wherein the deposited particle layer ( 3 ) is sintered into a compact layer ( 30 ). 12. The method according to claim 11, wherein the particle layer ( 30 ) is sintered in a gas atmosphere ( 4 ). 13. The method according to any one of claims 10 to 12, wherein to form the particle layer ( 3 ) particles ( 31 ) in the form of a particle stream ( 32 ) directed to the surface ( 20 ) are separated from the gas phase. 14. The method according to claim 13, wherein the particle stream ( 32 ) is directed at an angle (α) of less than 45 ° onto the surface ( 20 ). 15. The method according to any one of the preceding claims, in particular according to one of claims 12 to 15, wherein the layer ( 3 , 30 ) is deposited on the surface ( 20 ) by means of flame hydrolysis. 16. The method according to any one of the preceding claims, in particular according to claim 15, wherein the layer ( 3 , 30 ) is deposited on a cooler surface relative to the gas phase ( 20 ).