KR100442824B1 - A micromachine and a method for fabricating the same - Google Patents

Abstract

PURPOSE: A micro structure element and a manufacturing method thereof are provided to make a thick silicon micro structure without bending or damage caused by the residual stress of deposited silicon and to prevent the structure and a silicon substrate from sticking to each other. CONSTITUTION: A silicon substrate(100) is doped with a predetermined electroconductive material to have electroconductivity and formed with a micro structure of the predetermined thickness recessed from the center to both sides. A first glass substrate(200) has a first surface on which first and second electrodes(301,302) separated from each other are formed. The first electrode is directly contacted with the silicon substrate. The second electrode faces the recessed micro structure of the silicon substrate. External contact electrodes(303,304) are disposed to connect the electrodes to the outside on a second surface opposite to the first surface. A second glass substrate(300) is adhered on the opposite side of an adhering surface of the first glass substrate of the silicon substrate to seal the micro structure.

Description

Microstructure device and method for manufacturing the same {A micromachine and a method for fabricating the same}

The present invention relates to a micro structure (MEMS; Micro Electro Mechanical System) using an ultra-fine processing technology, and more particularly, to anodic bonding technology, deep RIE etching technology, and bulk etching technology of a silicon substrate and a glass substrate. The present invention relates to a microstructure device in which a thick silicon microstructure is formed by bonding, and a method of manufacturing the same.

In general, in the method of making a microgyroscope using a comb drive (comb drive), as shown in FIG. 1, the microstructure (2) with polycrystalline silicon using a polysilicon surface micromachining process method, as shown in FIG. ) And the sensing electrode 2 ′, or as shown in FIG. 2, the microstructure 6 was made of silicon doped with boron using a wafer dissolved method. . In this method, there is a limit to thickening the vibration structure, which has a close influence on the sensitivity of the microgyroscope, and thus there is a fundamental limitation in improving the performance of the microgyroscope. The problems of the two microstructure manufacturing process are summarized below.

A) polysilicon surface micromachining process

1. In the Low Stress Chemical Vapor Deposition (LPCVD) method, as shown in FIG. 1, the polycrystalline silicon stacking the microstructure 2 on the silicon substrate 1 has its own residual stress. Due to the thick stacking is limited to about 10㎛. When stacked excessively, this causes the microstructure 2 to bend. In order to prevent such warpage, ancillary heat treatment processes such as annealing are required. In addition, due to the various mechanical properties of the polysilicon, the performance of the microgyroscope tends to vary depending on the type of polysilicon furnace used.

2. Wet etching is performed to eliminate the sacrificial layer for the gap between the microstructure 2 and the electrode 2 ', so that the microstructure 2 and the bottom silicon 1 are stuck during the wet etching. Abandonment tends to occur. This results in a device that is not working smoothly, which reduces productivity. To prevent this sticking, new process development and additional equipment are needed.

3. Many small holes are drilled in the microstructures 2 for the wet etching process mentioned in 2, which results in a smaller area of the actual microstructures 2 and a lighter weight. This results in a sensitivity loss of about 25%.

4. Since parasitic capacitance is generated due to the structural problems constituting the vibrating structure 2 and the sensing electrode 2 'on the silicon substrate 1, the noise is large and signal-to-noise is high. noise) In FIG. 1, reference numeral 3 is an Al electrode, and reference numeral 4 is a wire for electrically connecting with an outside.

B) bulk etch wafer dissolution method;

1. Since the residual stress of the boron-doped silicon structure 6 as shown in FIG. 2 is large, it is not easy to make a thick microstructure 6. In addition, a heat treatment process such as annealing is required to eliminate residual stress.

2. Since the lower metal electrode 7 is exposed to an etchant during the bulk etching process, there is a limit to the selection of the metal electrode material.

The present invention has been made to improve the above problems, it is possible to form a thick silicon microstructure without bending or damage due to the residual stress of the silicon deposited, the structure and the silicon substrate is adhered by the etched solution when forming the structure It is an object of the present invention to provide a microstructure device and a method of manufacturing the same that can prevent discarding.

1 is a vertical cross-sectional view after the formation of a conventional polysilicon microstructure,

2 is a vertical cross-sectional view after microstructure formation by a conventional wafer dissolved bulk method;

3 is a vertical sectional view of a microstructure device according to the present invention;

4A to 4G are vertical cross-sectional views after the microfabrication step by step of the microstructure device according to the present invention.

<Description of the symbols for the main parts of the drawings>

1. Silicon substrate 2, 2 '. Polysilicon

3. metal electrode (aluminum) 4. wire

5. pyrex glass substrate 6. Boron doped silicon

7. Metal Electrode (Pt / Ti)

10. First depression surface 20. Second depression surface

100. n ⁺ doped silicon substrate 100a. Preliminary microstructure 100b. Microstructure 200. First Glass Substrate

300. Second Glass Substrate

301. First electrode (signal applying electrode for micro structure)

302. Second electrode (sensing electrode) 303. First external connection electrode

304. Second external connection electrode 305., 306. Wire

In order to achieve the above object, the microstructure device according to the present invention includes a silicon substrate having a predetermined thickness of microstructures having a conductivity by being doped with a conductive material and having a predetermined thickness; A first electrode and a second electrode spaced apart from each other on a surface thereof, wherein the first electrode is in direct contact with the silicon substrate and the second electrode is directly adhered to the silicon substrate so as to correspond to the recessed microstructure of the silicon substrate. First glass substrate; And a second glass substrate adhered to seal the microstructure on the opposite side of the silicon substrate to the adhesive surface of the silicon substrate.

In addition, in order to achieve the above object, the method for manufacturing a microstructure device according to the present invention includes (a) recessing to a predetermined depth so as to face the sensing electrode by selectively etching both surfaces of the central portion of the silicon substrate doped with the conductive material. Forming a preliminary microstructure formed by the first recessed surface and the second recessed surface to ensure a predetermined thickness from the first recessed surface; (B) adhering a first glass substrate to the silicon substrate so as to face the second recessed surface of the microstructure; (C) etching the preliminary microstructures adhered to the first glass substrate to form microstructures; (D) a second glass substrate having holes for connection with the outside and spaced apart from each other to cover the holes, and a second glass substrate having a signal applying electrode for the microstructure on its surface; Adhering to the silicon substrate to face the first recessed surface of the microstructure; And (e) forming external contact electrodes on the inclined surfaces of the holes, respectively, to allow the sensing electrode and the signal applying electrode for the microstructure to be connected to the outside, respectively.

In the present invention, in the step (a), the first recessed surface and the second recessed surface are each etched by a wet etching method, and the step (b) is performed by an anode bonding method, and the (c) step is It is made by an active ion etching method, in the step (d) is used an anode bonding method, the method for manufacturing a second glass substrate with an electrode, comprising the steps of: depositing an electrode material on the second glass substrate; Patterning the deposited electrode material to form signal applying and sensing electrodes for the microstructure; And forming holes to expose the signal applying electrode and the sensing electrodes for the microstructure.

Hereinafter, a microstructure device and a manufacturing method thereof according to the present invention will be described with reference to the drawings.

3 is a vertical sectional view of a microstructure device according to the invention. As shown, the microstructure device using the bulk etching according to the present invention is a silicon substrate 100 having a microstructure 101 is formed between the two glass substrates (200, 300) in the form of an anode bonding Is made. Here, the silicon substrate 100 is n ⁺ doped with a pentavalent element to have conductivity, and a thick microstructure 101 recessed from both sides is formed in the center. The first glass substrate 300 includes a first electrode 301 and a second electrode 302 spaced apart from each other on its surface. The first electrode 301 is a signal applying electrode for applying a voltage signal to the microstructure, and is in direct contact with the silicon substrate 100. The second electrode 302 is a sensing electrode for sensing movement of the microstructure. Disposed to correspond with the recessed microstructure 101 of 100. The second glass substrate 200 is in close contact with the silicon substrate 100 such that the microstructure 101 is sealed to the opposite side of the first glass substrate 300 with the silicon substrate 100 interposed therebetween. When this compacting process is performed in the vacuum chamber, the space in which the microstructures are formed forms a vacuum state.

Figures 4a to 4g is a vertical cross-sectional view after the step of microfabrication of the microstructure device according to the present invention. As shown, the method for manufacturing a microstructure device according to the present invention uses bulk micromachining. Referring to the manufacturing method of such a microstructure in detail as follows.

First, an oxide film (SiO ₂ ) is formed on a surface of the silicon substrate 100 doped with n ⁺ by wet oxidation, and then a SiO ₂ oxide film is etched with a BHF solution using a photoresist pattern to form a mask ( Not shown). Next, the entire surface is etched by TMAH wet etching using this mask (not shown) to form the first recessed surface 10 on the entire central portion of the silicon substrate 100 as shown in FIG. 4A. The depth d of the first recessed surface 10 determines the distance between the microstructure and the sensing electrode, so that the etching depth is precisely etched. Next, as shown in FIG. 4B, the second recessed surface 20 is formed on the rear surface of the central portion of the silicon substrate 100 in the same manner to complete the preliminary microstructure. This second depression 20 determines the thickness t of the microstructure.

Next, as shown in FIG. 4C, anodically bonding the first glass substrate to the silicon substrate 100 so as to face the second recessed surface 20 of the preliminary microstructure formed on the silicon substrate 100. To glue.

Next, an etching mask (not shown) is formed on the preliminary microstructure 100a adhered to the first glass substrate 100, and then the preliminary microstructure 100a is etched by reactive ion etching (RIE). Thus, the microstructure 100b as shown in FIG. 4D is formed.

Next, the signal applying electrode 301 (first electrode) and the sensing electrode 302 for the microstructures are provided with holes 300a for wiring to the outside and are spaced apart from each other to cover the holes 300a, respectively. As shown in FIG. 4E, the second glass substrate 300 having the two electrodes is provided on the surface thereof such that the sensing electrode 302 faces the first recessed surface 10 of the microstructure 100b. 100). At this time, the bonding step uses an anode bonding method. Here, in the method of forming an electrode on the second glass substrate, first, the electrodes 301 and 302 are patterned on the second glass substrate 100, and then the holes 300a are exposed in the glass substrate so that the electrodes 301 and 302 are exposed. Proceed in order to form a.

Next, as shown in FIG. 4F, the holes 300a are sputtered with external contact electrodes 303 and 304 such that the signal applying electrode 301 and the sensing electrode 302 for the microstructure can be connected to the outside, respectively. Are deposited on the inclined surface of each).

Next, as shown in FIG. 4G, the wires 305 and 306 are bonded to complete the microstructure element.

As described above, the microstructure device using the wafer bulk etching and the method of manufacturing the same according to the present invention use the silicon wafer itself, which is not processed from the material of the microstructure, so there is no problem such as residual stress, and various other mechanical When the wafer to be used also has its characteristics, it is always constant. Therefore, stable mechanical properties of the microstructure can be achieved. Since the thickness of the microstructure is determined by the relationship between the thickness and the processing line width by a deep RIE (reactive ion etching) device, it is possible to form a thick microstructure of 50 μm or more, which has not been manufactured by a conventional manufacturing method. In addition, since the silicon structure is placed on the glass substrate by using anodic bonding, parasitic capacitance is hardly generated and noise can be further reduced. Thus, the reduction in sensitivity of the microstructures can be minimized. In addition, the manufacturing process is simple, the alignment is not very important during the lithography of each mask due to the process characteristics, it is advantageous to improve the productivity when commercialized. In terms of equipment, it does not require expensive equipment except for deep RIE equipment, and the number of equipment required for the manufacturing process is relatively small.

Claims (7)

A silicon substrate having a conductive structure doped with a predetermined conductive material and having a microstructure having a predetermined thickness recessed from both sides at a central portion thereof; A first electrode and a second electrode spaced apart from each other are formed on the first surface, the first electrode is in direct contact with the silicon substrate and the second electrode is disposed to face the recessed microstructure of the silicon substrate, A first glass substrate having first and second electrodes respectively provided with an external contact electrode connected to the outside from a second surface opposite to the first surface, wherein the first surface is directly bonded to the silicon substrate; And And a second glass substrate adhered to the surface opposite to the adhesive surface of the silicon substrate to the first glass substrate so as to seal the microstructure. A silicon substrate having a conductive structure doped with a predetermined conductive material and having a predetermined thickness of microstructures recessed from both surfaces thereof, a signal applying electrode for microstructures covering the spaced apart holes, and a first surface, respectively; The signal applying electrode is in direct contact with the silicon substrate and the sensing electrode is disposed to face the recessed microstructure of the silicon substrate, and the signal applying electrode and the sensing electrode are respectively external from the second surface opposite to the first surface. An external contact electrode is connected to each other, and the microstructure is sealed on a surface opposite to an adhesive surface of the first glass substrate directly bonded to the silicon substrate and the first glass substrate of the silicon substrate. In the method of manufacturing a microstructure device having a second glass substrate bonded to be, (A) The first recessed surface recessed to a predetermined depth so as to face the sensing electrode by selectively etching both surfaces of the central portion of the silicon substrate doped with the conductive material and the second recessed surface to ensure a predetermined thickness from the first recessed surface. Forming a preliminary microstructure formed by; (B) adhering a second glass substrate to the silicon substrate so as to face the second recessed surface of the microstructure; (C) etching the preliminary microstructures adhered to the second glass substrate to form microstructures; (D) a first glass substrate having holes for connection to the outside and having a sensing electrode and a signal applying electrode for microstructures formed on the surface thereof so as to be spaced apart from each other to cover the holes; Adhering to the silicon substrate to face the first recessed surface of the microstructure; And And (e) forming external contact electrodes on the inclined surfaces of the holes to allow the sensing electrode and the signal applying electrode for the microstructure to be connected to the outside, respectively. The method of claim 2, The method of claim 1, wherein the first recessed surface and the second recessed surface are each etched by a wet etching method. The method of claim 2, The step (b) is a method for manufacturing a microstructure device, characterized in that the anode bonding method. The method of claim 2, The step (c) is a method of manufacturing a microstructure device, characterized in that the reactive ion etching method. The method of claim 2, The step (d) is a method for manufacturing a microstructure device, characterized in that the anode bonding method. The method of claim 2, The method of manufacturing the second glass substrate provided with the electrode in the step (d) may include depositing an electrode material on the second glass substrate; Patterning the deposited electrode material to form signal applying and sensing electrodes for the microstructure; And And forming holes to expose the signal applying electrode and the sensing electrodes for the microstructure.

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