KR20070071026A - Method for preventing stiction in microsystem - Google Patents

Abstract

A method for preventing stickiness in a micro structure is provided to prevent defects with water molecule by forming a hydrophobic layer on a surface of the micro structure. A method for preventing stickiness in a micro structure includes the steps of preparing a substrate having a micro structure covered by a sacrifice layer, etching the sacrifice layer(200), washing a substrate with deionized water(201) so as to remove by-product, washing the substrate with isopropyl alcohol steam(202) in order to convert a surface of the micro structure into a hydrophilic surface, vapor depositing HMDS to form a coating layer(203) so as to convert the hydrophilic surface of the micro structure into a hydrophobic surface, and drying a resulting object(204).

Description

How to prevent adhesion of microstructures {METHOD FOR PREVENTING STICTION IN MICROSYSTEM}

1 is a view showing a microstructure used in the adhesion prevention method according to an embodiment of the present invention,

2 is a flowchart illustrating a method of adhering microstructures according to a first embodiment of the present invention;

3A to 3E are cross-sectional views of a process in the microstructure of FIG. 1 according to FIG. 2;

Figure 4 is a flow chart showing the adhesion method of the microstructures according to the second embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

11 polycrystalline silicon wafer 12 first sacrificial layer

13: polycrystalline silicon 14: second sacrificial layer

16: hydrophilic surface 17: coating film

The present invention relates to a technology for processing a microstructure including a micro-electro-mechanical system (MEMS), and more particularly, to a method of preventing adhesion of a microstructure.

A sticking phenomenon is an unintentional adhesion to the surface of a microstructure, so that the force to recover does not overcome the forces acting on the surface such as capillary forces, van der Waals, or electrostatic force Talk about the phenomenon. Such adhesion phenomenon is largely classified into release-related stiction and in-use stiction when removing a sacrificial layer.

First, the adhesion phenomenon when the sacrificial layer is removed is caused by the liquid capillary force due to the adhesion that the structure does not adhere to the floor and is not dropped during the structure release process. At present, this phenomenon can be solved by the technique of avoiding the liquid gas phase interface by methods such as sublimation drying method, supercritical drying method and hydrofluoric acid vapor drying method. In addition, small protrusions can be created around the microstructure to reduce the capillary force by changing the liquid shape (meniscus).

However, these methods also cannot solve the occurrence of adhesion that the microstructure is not restored due to humidity or excessive impact during operation. The reason is that when the surfaces of adjacent microstructures come into contact with each other, forces such as capillary, electrostatic, and van der Waals are generated, and the surface adhesion is caused by these forces, resulting in damage to the device, resulting in adhesion of the structure. Because.

Recently, methods for chemically modifying the surface of structures have been published, for example hydrogen passivation, hydrogen bond fluoride monolayers, plasma deposited fluorocarbon thin films, and covalently-bound hydrocarbon self-assembled monolayers. assembled monolayer (SAM). The representative one of these is the SAM method. However, this SAM method also has a disadvantage in that the processing method is complicated, the process cost is high, and the dependence on temperature is strong.

As described above, the conventional sublimation drying method, supercritical drying method, and hydrofluoric acid vapor drying method are techniques for avoiding the liquid surface shape during drying after removing the sacrificial layer of the structure. There is a problem that is attached to the bottom of the structure is affected significantly. In addition, the SAM method recently developed has a long process time and a disadvantage that the process cost is expensive.

In order to solve the above problems, a method of depositing and drying a silane-based compound has recently been developed, but this also requires a multi-step cleaning process and increases the cost thereof (Korean Patent Publication, 10-2004-O048208).

The present invention is proposed to solve the problems of the prior art, to form a hydrophobic film on the surface of the microstructure by the vapor phase coating of HMDS commonly used in the semiconductor mask process to prevent defects with water molecules by the ambient humidity or the environment The purpose of the present invention is to provide a method for preventing adhesion of microstructures that can easily prevent adhesion of microstructures without increasing the cost.

Method for preventing adhesion of the microstructures of the present invention for achieving the above object is to prepare a substrate having a microstructure covered by a sacrificial layer, etching the sacrificial layer, to remove the by-products remaining after etching the sacrificial layer Washing with deionized water, washing with isopropyl alcohol to change the surface of the microstructure to a hydrophilic surface while removing by-products remaining after the deionized water, and the surface of the microstructure having the hydrophilic surface. To a hydrophobic surface, wherein the step of converting the surface of the microstructure having the hydrophilic surface into a hydrophobic surface comprises the chemical formula of C ₆ H ₁₉ NSi _{2 on} the surface of the microstructure having the hydrophilic surface. Characterized in that the HMDS having a vapor deposition and then dried, the gas phase of the HMDS Complex is characterized in that the vapor deposition for 1-10 minutes at a temperature of 130~200 ℃, wherein the drying is used for baking, and the baking temperature is characterized by a 160 ℃ ~250 ℃.

Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. .

1 is a view showing a microstructure used in the adhesion prevention method according to an embodiment of the present invention.

Referring to FIG. 1, after depositing the first sacrificial layer 12 on the single crystal silicon wafer 11, the first sacrificial layer 12 is etched to form a microstructure connected to a part of the single crystal silicon wafer 11. The polysilicon 13 is formed, and the second sacrificial layer 14 is deposited on the polysilicon 13. Here, the first sacrificial layer 12 and the second sacrificial layer 14 are silicon oxide-based oxide films or photoresists deposited by the CVD method.

In the structure having the completed microstructure as described above is subjected to a flotation process for supporting the microstructure, that is, polycrystalline silicon 13 from the single crystal silicon wafer (11), the adhesion phenomenon occurring during the flotation process and the adhesion phenomenon occurring during use In order to prevent the process proceeds as in FIG.

2 is a flowchart illustrating a method of adhering microstructures according to a first embodiment of the present invention, and FIGS. 3A to 3E are cross-sectional views illustrating processes of the microstructure of FIG. 1 according to FIG. 2. Hereinafter, a description will be given with reference to FIGS. 2 and 3A to 3E.

Referring to FIG. 2, a first process 100 for etching a sacrificial layer, a second process 101 for cleaning with deionized water, a third process 102 for cleaning using an isopropyl alcohol liquid, and vapor deposition of HMDS And a fourth process 103 of forming a coating film and a fifth process 104 of drying.

First, the first process 100 is a process of etching the first and second sacrificial layers 12 and 14. When the first and the second sacrificial layers 12 and 14 are photoresist, wet etching using solvent is performed. Alternatively, dry etching using oxygen plasma (0 ₂ plasma) is possible.

When the first and second sacrificial layers 12 and 14 are silicon oxide films, wet etching using an aqueous hydrofluoric acid (HF) solution is possible.

Next, the second process 101 is a process of cleaning using deionized water, and is a process of removing the by-products (15 'in FIG. 3A) remaining during the first process 100 (see FIG. 3B). Preferably, washing with deionized water proceeds by dipping for 10 minutes.

Next, the third process 102 is performed using the isopropyl alcohol liquid to remove subsequent by-products (15a in FIG. 3b) during the sacrificial layer etching remaining after the second process 101 is carried out. coating) This is a pre-wetting process to form a coating film with a uniform thickness during the work. Preferably, washing with isopropyl alcohol liquid phase is carried out for 1 to 2 minutes.

As described above, when the cleaning is performed using the isopropyl alcohol liquid phase, all residual byproducts 15a are removed, and the surface of the polysilicon layer 13 is changed to the hydrophilic surface 16 (see FIG. 3C).

Next, the fourth process 103 forms a coating film 17 on the surface of the structure hydrophilized by the isopropyl alcohol of the third process 102 to change the surface into a hydrophobic surface to prevent bonding with moisture to prevent adhesion of the structure. Is a process of minimizing (see FIG. 3D). That is, since the coating film 17 coated by HMDS vapor deposition is a hydrophobic film having a hydrophobic surface, the surface of the polycrystalline silicon is changed from hydrophilic to hydrophobic surface.

Preferably, the coating film 17 is obtained by vapor deposition of HMDS for 1 minute to 10 minutes at high temperature (130-200 ° C). The chemical formula of the HMDS is represented by C ₆ H ₁₉ NSi ₂ , the structure of the HMDS is as follows.

Next, the fifth process 104 is a process of drying by baking after coating the HDMS. At this time, the baking temperature during drying is 160 ℃ to 250 ℃ (see Figure 3e).

On the other hand, the drying may proceed simultaneously with the deposition of the coating film (17). That is, baking is performed in-situ after vapor deposition of HMDS.

4 is a flowchart illustrating a method of adhering microstructures according to a second exemplary embodiment of the present invention, which is performed with respect to the microstructure of FIG. 1 and will be described with reference to FIGS. 3A to 3E.

Referring to FIG. 4, a first process 200 for etching a sacrificial layer, a second process 201 for cleaning with deionized water, a third process 202 for cleaning using isopropyl alcohol vapor, and vapor deposition of HMDS And a fourth process 203 to form a coating film and a fifth process 204 to dry.

First, the first process 200 is a process of etching the first and second sacrificial layers 12 and 14. When the first and the second sacrificial layers 12 and 14 are photoresist, wet etching using solvent is performed. Alternatively, dry etching using oxygen plasma (0 ₂ plasma) is possible.

When the first and second sacrificial layers 12 and 14 are silicon oxide films, wet etching using an aqueous hydrofluoric acid (HF) solution is possible.

Next, the second process 201 is a process of washing using deionized water, and is a process of removing the by-products ('15' of FIG. 3A) remaining during the first process 200 (see FIG. 3B). Preferably, washing with deionized water proceeds by dipping for 10 minutes.

Next, the third process 202 is performed using the isopropyl alcohol liquid to remove the remaining by-products (15a in FIG. 3b) during the sacrificial layer etching remaining after the second process 201 is carried out, and the coating of the subsequent HMDS ( coating) This is a pre-wetting process to form a coating film with a uniform thickness during the work. To this end, washing is performed using isopropyl alcohol vapor (Vapor). That is, in addition to the liquid phase cleaning of the first embodiment, in the second embodiment, washing in the gas phase using isopropyl alcohol vapor at 180 ° C to 220 ° C, that is, isopropyl alcohol vapor at a temperature of 180 ° C to 220 ° C is possible.

As described above, when washing is performed using isopropyl alcohol vapor, all residual by-products 15a are removed, and the surface of the polysilicon layer 13 is changed to the hydrophilic surface 16 (see FIG. 3C).

Next, the fourth process 203 forms a coating film 17 on the surface of the structure hydrophilized by the isopropyl alcohol of the third process 202 to hydrophobize the surface to prevent bonding with moisture to minimize adhesion of the structure. (See FIG. 3D). That is, since the coating film 17 coated by HMDS vapor deposition is a hydrophobic film having a hydrophobic surface, the surface of the polycrystalline silicon 13 is changed from hydrophilic to hydrophobic surface.

Preferably, the coating film 17 is obtained by vapor deposition of HMDS for 1 minute to 10 minutes at high temperature (130-200 ° C). The HMDS is represented by C ₆ H ₁₉ NSi ₂ , and the structure of the HMDS is the same as that of Chemical Formula 1 in the first embodiment.

Next, the fifth process 204 is a process of drying by baking after coating the HDMS. At this time, the baking temperature during drying is 160 ℃ to 250 ℃ (see Figure 3e).

On the other hand, the drying may proceed simultaneously with the deposition of the coating film (17). That is, baking is performed in-situ after vapor deposition of HMDS.

In the above-described first and second embodiments, the microstructures use polycrystalline silicon, but the microstructures may be metal structures in addition to silicon structures such as polycrystalline silicon, wherein the metal structures include aluminum, aluminum alloy or copper. .

As described above, the present invention is not limited to the above-described embodiments and the accompanying drawings, and the present invention may be variously substituted, modified, and changed without departing from the spirit of the present invention. It will be apparent to those of ordinary skill in Esau.

The present invention as described above prevents the bonding of moisture due to ambient humidity or environmental change through the formation of a hydrophobic coating film by HMDS, thereby minimizing adhesion occurring during the removal of the sacrificial layer of the microstructure or during use to extend the life of the product. It can be effective.

In addition, the present invention is very simple compared to the existing methods it is possible to use the devices used in the conventional semiconductor manufacturing process, the chemical used extensively in the mask process of the semiconductor manufacturing process by using the new chemical HMDS Since this is not necessary, there is an effect of reducing the manufacturing cost.

In addition, the coating film for preventing adhesion according to the present invention is applicable to all metal structures (aluminum or aluminum alloys, copper or copper alloys, etc.) as well as silicon structures.

Claims (11)

Preparing a substrate having a microstructure covered by a sacrificial layer; Etching the sacrificial layer; Washing with deionized water to remove by-products remaining after etching the sacrificial layer; Washing with isopropyl alcohol to change the surface of the microstructure to a hydrophilic surface while removing byproducts remaining after the deionized water; And Converting the surface of the microstructure having the hydrophilic surface into a hydrophobic surface Method of preventing adhesion of microstructures comprising a. The method of claim 1, Replacing the surface of the microstructure having the hydrophilic surface with a hydrophobic surface, Method for preventing adhesion of the microstructures, characterized in that the vapor-deposited HMDS having a chemical formula of C ₆ H ₁₉ NSi _{2 on} the surface of the microstructure having a hydrophilic surface and then dried. The method of claim 2, The vapor deposition of the HMDS is, Method for preventing adhesion of microstructures, characterized in that vapor deposition at a high temperature of 130 to 200 ℃ for 1 to 10 minutes. The method of claim 2, The drying is using a baking, the temperature of the baking is 160 ℃ to 250 ℃ characterized in that the adhesion prevention method of the microstructure. The method of claim 2, The drying is the adhesion prevention method of the microstructures, characterized in that to proceed in-situ after the vapor deposition of the HMDS. The method of claim 1, The washing using the isopropyl alcohol, Method for preventing adhesion of microstructures, characterized by using isopropyl liquid phase. The method of claim 6, The washing using the isopropyl liquid phase, A method for preventing adhesion of microstructures, which proceeds for 1 to 2 minutes. The method of claim 1, The washing using the isopropyl alcohol, Method for preventing adhesion of microstructures, characterized by using isopropyl vapor. The method of claim 8, The cleaning method using the isopropyl alcohol vapor, isopropyl alcohol vapor at a temperature of 180 ℃ to 220 ℃ using the adhesion prevention method of the microstructure. The method of claim 1, The microstructure is a silicon structure or a metal structure, characterized in that the adhesion prevention method of the microstructure. The method of claim 10, The metal structure is an adhesion prevention method of the microstructure, characterized in that aluminum, aluminum alloy or copper.

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