CN100509611C

CN100509611C - Microelectron mechanical system obverse structure releasing protecting method

Info

Publication number: CN100509611C
Application number: CNB2007100223599A
Authority: CN
Inventors: 秦明; 张筱朵; 黄庆安
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2007-05-15
Filing date: 2007-05-15
Publication date: 2009-07-08
Anticipated expiration: 2027-05-15
Also published as: CN101077767A

Abstract

The protected front structure releasing process in the post-treatment of micro electromechanical system includes the following steps: the first depositing one intermediate layer in the whole front side of the chip, and etching to form the intermediate layer pattern to cover the aluminum pads and aluminum leads; the subsequent depositing one aluminum layer in the whole front side of the chip, and etching to form the aluminum layer pattern or forming etching windows to complete the making of the composite film; etching the chip with composite film in optimized TMAH etching solution to eliminate front silicon, and wet etching to eliminate aluminum layer; and dry etching to eliminate the intermediate layer of organic film or wet etching to eliminate the intermediate layer of titanium layer or other metal layer.

Description

The guard method that microelectron mechanical system obverse structure discharges

Technical field

The present invention relates to the front protecting method that Facad structure discharges in a kind of MEMS (microelectromechanical systems) post processing; especially when CMOS-MEMS technology is made monolithic integrated sensor, in the MEMS aftertreatment technology during front body silicon wet etching to the guard method of polycrystal layer under surfaces of aluminum lead-in wire, pad and the passivation layer of the cmos circuit part that completed.

Background technology

Along with the fast development of integrated circuit technology, the silicon micro-machining technology compatible mutually with traditional IC technology become the mainstream technology of making microsensor, microactrator and MEMS.And be low cost, the batch process that the CMOS-MEMS technology can realize the front microsensor by this CMOS process compatible Monolithic integrated MEMS technology that MEMS structure division and cmos circuit are made on the same substrate.Wet etching is a MEMS aftertreatment technology comparatively commonly used in the CMOS-MEMS technology, utilizes the anisotropic etch characteristic of alkaline solutions such as KOH, TMAH, EDP to realize the structures such as chamber, groove of sensor.But aluminum pad of making in the CMOS technology and polycrystalline structure are very easily corroded by above-mentioned corrosive liquid, so the chip that CMOS technology is finished is not suitable for directly carrying out the wet etching in the follow-up post processing, need take certain measure to be protected.The angle one of seeking this measure is from the performance that improves corrosive liquid it more to be considered with the CMOS process compatible; The 2nd, from adding the diaphragm consideration at ready-made CMOS part passivation layer and aluminum pad.See at present that from the angle of corrosive liquid the technology of comparative maturity is to optimize the TMAH corrosive liquid; behind mix certain silica flour and oxidant, can make the right Si/Al corrosion of TMAH corrosive liquid than uprising the scope that is able to carry out miniature body processing, to reach the purpose of protection.But for long high temperature corrosion, add that the height of chip surface rises and falls, corrosive liquid might penetrate passivation etching and cause failure to the polysilicon layer under the passivation layer.From the diaphragm angle, this diaphragm should be in conjunction with selected corrosive liquid, possesses and characteristic such as the chip surface adhesiveness is good, corrosion-resistant, high temperature resistant, if to carrying out etching in the front of chip, this film also should have can be by the characteristic of photoetching.The film that is used for this protection at present is a monofilm all, mainly contains the Si of PECVD deposit ₃N ₄Film, however it need be big to pinhold density, step coverage is not that fine these two aspects are improved.PECVD deposit SiC film, it needs the control actual process parameter to reach the characteristics of low stress, corrosion resistance equally.The gold film though can resist the golden film of corrosion of alkaline solution well and the adhesion property between silicon substrate and the chip surface passivation layer is not fine, adopts the thick gold membrane cost too high in addition.Though therefore above three kinds of methods introducing can reach the effect of wet etching front protecting, and its limitation is all arranged.

Technology contents

Technical problem: the purpose of this invention is to provide the guard method that a kind of microelectron mechanical system obverse structure discharges; this method be in a kind of safe and reliable MEMS aftertreatment technology during the bulk silicon etching of front to the guard method of polycrystal layer under surfaces of aluminum lead-in wire, pad and the passivation layer of CMOS part; this method utilizes the TMAH corrosive liquid after structure of composite membrane and the optimization to combine; when having finished the release of Facad structure, solved because of passivation layer compactness and caused the permeating corrosion problem; have the process compatible with CMOS, technology realizes characteristics such as simple.

Technical scheme: have the part of aluminum pad and aluminum lead to make one deck intermediate layer (this intermediate layer can be other metals except that aluminum metal, also can be a kind of organic material of the IC of being compatible with technology) at the chip surface of carrying out cmos circuit; Then at entire chip front surface deposit layer of metal aluminium lamination; The positive then window that needs corrosion of opening carries out bulk silicon etching with the TMAH corrosive liquid of optimizing.Aluminium lamination with the superiors after finishing structure and discharging removes with corroding method, and the intermediate layer optionally can keep or remove.

Specifically may further comprise the steps:

1.), utilize photoetching, etching process to produce the figure in intermediate layer then, guarantee that chip front side itself has the part of aluminum pad or aluminum lead to cover and goes up the intermediate layer earlier at the positive deposit one deck of entire chip intermediate layer material,

2.) follow deposit layer of aluminum on the entire chip front, the figure that utilizes photoetching, etching process to produce aluminium lamination is promptly opened corrosion window, has finished the making of composite membrane this moment,

3.) then the above chip of having made composite membrane is put into TMAH corrosive liquid after the optimization, after the bulk silicon etching aluminium lamination is fallen with wet etching the front bulk silicon etching; If the intermediate layer is selected organic film then with the way of dry etching it is removed, if select titanium layer and gold layer then it is removed with wet etching method.

The optimization method of TMAH corrosive liquid is: selecting concentration is the TMAH corrosive liquid of 10wt.%, mix therein greater than the silica flour of 3.0wt.% and greater than the ammonium persulfate of 1.2wt.% as the bulk silicon etching liquid after optimizing, corrosion temperature is at 70 ℃ to 90 ℃.

The corrosive liquid of wet etching method is respectively, and the corrosive liquid typical proportion of aluminium is an acetate: nitric acid: phosphoric acid=20:3:77, corrosion temperature are 40 ℃; The corrosive liquid typical proportion of gold is the KI of 4g, and the iodine of 1g is dissolved in the water of 40ml, and corrosion temperature is 20 ℃ to 50 ℃; The corrosive liquid of titanium is a diluted hydrofluoric acid.

The intermediate layer of composite membrane is other metals except that aluminum metal, or a kind of organic material that is compatible with IC technology.

Beneficial effect: the present invention is applied to CMOS-MEMS technology and makes in the monolithic integrated sensor, can not be damaged to the cmos circuit part that has completed when having guaranteed the MEMS structure fabrication.The special protection to the part of aluminum pad and aluminum lead is played in the intermediate layer, and itself and the superiors' aluminium are isolated.The superiors' aluminium is based on the TMAH corrosive liquid, and can to obtain very high Si/Al corrosion in certain silica flour and oxidant (as the ammonium persulfate) back of mixing under certain corrosion temperature condition more almost nil than making the corrosion to aluminium.Therefore the superiors' aluminium can play and prevent that corrosive liquid from penetrating the bad passivation layer of compactness, has protected the polysilicon layer the passivation layer under not to be corroded, and if the enough thick long high temperature (85C °) that can guarantee of this layer aluminium corrode.Certain organic film such as polyimide film can be selected in the intermediate layer, and certain is not the metal level of aluminium perhaps not select the person.If the intermediate layer is selected titanium layer and gold layer for use; then this layer metal level can be used as another layer metal line playing in protection aluminum pad and aluminum lead; for example can be integrated again to CMOS part and MEMS part interconnection line, need not remove so can be retained on the chip.

Description of drawings

Fig. 1 is a process structure generalized section of the present invention.

Have among the figure: aluminium lamination 1, intermediate layer 2, passivation layer 3, aluminum pad or aluminum lead 4, body silicon 5.

The specific embodiment

The present invention is the method for protection front cmos circuit part when Facad structure discharges in a kind of MEMS post processing.Chip surface is mainly aluminum pad or aluminum lead 4, passivation layer 3 after finishing according to IC technology cmos circuit.The main enforcement of this method starts from the making to the intermediate layer, the selection in intermediate layer can be that organic film also can be other metal level of non-aluminum metal, earlier at whole surface deposition one deck intermediate layer material, utilize photoetching then, etching process is produced the figure in intermediate layer 2, guarantee that aluminum pad or aluminum lead 4 parts are coated with intermediate layer 2, then deposit layer of aluminum thickness is about 1 micron on entire chip, and utilize photoetching, etching process is produced the figure of the superiors' aluminium lamination 1 and is promptly opened corrosion window, body silicon 5 is corroded by corrosion window with the TMAH corrosive liquid of optimizing then.Being optimized for of TMAH corrosive liquid: selecting concentration is the TMAH corrosive liquid of 10wt.%, mix therein greater than the silica flour of 3.0wt.% (representative value is 3.0wt.%) with greater than 1.2wt.% (representative value 1.3wt.%) be ammonium persulfate as the bulk silicon etching liquid after optimizing, corrosion temperature is in 70 ℃ to 90 ℃ (representative value is 85 ℃) scopes.After bulk silicon etching is intact the superiors' aluminium lamination 1 usefulness wet etching is fallen.If intermediate layer 2 is selected organic film (as polyimides) then with the way of dry etching such as plasma etching it is removed, if select titanium layer and gold layer then it is removed with wet etching method.The corrosive liquid of the wet etching of using in the above process is respectively, and the corrosive liquid typical proportion of aluminium is an acetate: nitric acid: phosphoric acid=20:3:77, corrosion temperature are 40 ℃; The corrosive liquid typical proportion of gold is the KI of 4g, and the iodine of 1g is dissolved in the water of 40ml, and corrosion temperature is 20 ℃ to 50 ℃; The corrosive liquid of titanium is a diluted hydrofluoric acid.

Claims

1. guard method that microelectron mechanical system obverse structure discharges is characterized in that may further comprise the steps:

1.), utilize photoetching, etching process to produce the figure of intermediate layer (2) then, guarantee that chip front side itself has the part of aluminum pad or aluminum lead (4) to cover and goes up intermediate layer (2) earlier at the positive deposit one deck intermediate layer (2) of entire chip material,

2.) follow deposit layer of aluminum on the entire chip front, the figure that utilizes photoetching, etching process to produce aluminium lamination (1) is promptly opened corrosion window, has finished the making of composite membrane this moment,

3.) then the above chip of having made composite membrane is put into TMAH corrosive liquid after the optimization, after body silicon (5) corrosion aluminium lamination (1) is fallen with wet etching front body silicon (5) corrosion; Intermediate layer (2) selects organic film then with the way of dry etching it to be removed, and selects titanium layer and gold layer then with wet etching method they to be removed;

The intermediate layer of composite membrane is other metals except that aluminum metal, or a kind of organic material that is compatible with IC technology;

2. the guard method that microelectron mechanical system obverse structure according to claim 1 discharges, it is characterized in that: the corrosive liquid of wet etching method is respectively, and the corrosive liquid typical proportion of aluminium is an acetate: nitric acid: phosphoric acid=20:3:77, corrosion temperature are 40 ℃; The corrosive liquid typical proportion of gold is the KI of 4g, and the iodine of 1g is dissolved in the water of 40ml, and corrosion temperature is 20 ℃ to 50 ℃; The corrosive liquid of titanium is a diluted hydrofluoric acid.