KR20020083407A - Microstructure for vertical displacement measurement and vertical movement, and fabricating method thereof - Google Patents

Abstract

PURPOSE: A structure for measuring and driving vertical displacement and a method for fabricating the same are provided to simplify a fabricating process by fabricating a structure and an electrode, simultaneously. CONSTITUTION: A rectangular frame(32) is installed at a predetermined height from a bottom of a body(10) of a single crystalline silicon wafer. A torsional spring(20) is extended from both sides of the rectangular frame(32) to the outer direction. The torsional spring(20) is connected with an inner wall of the body(10). The rectangular frame(32) is supported by the torsional spring(20). An inertial mass body(34) and a mobile electrode(30) are formed in the inside of the rectangular frame(32). A fixing electrode(40) is formed between the mobile electrodes(30). A trench having a narrow opening is formed in the fixing electrode(40). The fixing electrode(40) is connected with a fixing anchor(42) by an anchor side portion(46).

Description

Microstructure for vertical displacement measurement and vertical movement, and fabricating method

The present invention relates to a vertical displacement measurement and drive structure and a method of manufacturing the same, and more particularly, to a silicon structure and a method for manufacturing the vertical displacement measurement and drive.

The vertical displacement measuring and driving structure generally includes a top electrode and a bottom electrode horizontally in the structure to measure a change in capacitance between these electrodes according to the vertical displacement.

However, in order to manufacture such a structure, since the fabrication of the structure and the fabrication of the electrode cannot be performed at the same time, patterning of the electrode and the structure must be performed several times, and deposition of a sacrificial layer or wafer bonding to maintain a constant gap between the electrodes The manufacturing process is complicated, such as requiring a process. In addition, in order to precisely measure the vertical displacement, the distance between the electrodes must be narrow, so that there is a problem that the adhesion phenomenon between the structure and the electrode where the vertical displacement occurs can easily appear.

The present invention was created to improve the above problems, and an object of the present invention is to provide a vertical displacement measurement and driving structure in which a structure and an electrode are manufactured at the same time, and thus the process is simple, and electrodes are arranged horizontally , thereby excluding structural adhesion. To provide.

Another object of the present invention is to provide a method for producing the structure.

1 is a perspective view of a vertical displacement measurement and drive structure according to a first embodiment of the present invention;

2 is a plan view of FIG.

3 is a schematic cross-sectional view of a surface cut in the III-III 'direction of FIG.

4A to 4C are views illustrating vertical displacement measurement according to the structure of FIG. 1;

5 is a cross-sectional view showing a first modification of FIG. 3;

6 is a sectional view showing a second modification of FIG.

7 is a schematic plan view of a vertical displacement measurement and drive structure according to a second preferred embodiment of the present invention;

FIG. 8 is a schematic cross-sectional view of a portion cut in the VII-VII 'direction of FIG. 7;

9 is an electron scanning micrograph of an acceleration measuring system manufactured using a vertical displacement measuring structure according to the present invention;

FIG. 10 is an enlarged photograph of a fixed comb electrode and a mobile comb electrode, which are part of FIG. 9; FIG.

11 is a graph showing the result of applying the accelerometer of FIG.

12A to 12F are steps illustrating a manufacturing method according to the present invention.

* Description of Signs of Major Parts of Drawings *

10: body 12: body bottom

20: torsion spring 22: bending spring

30: moving comb electrode 32: square frame

34: inertial mass 40: fixed comb electrode

42: anchor anchor 44: trench

54: oxide film 56: polycrystalline silicon electrode

58: metal electrode

In order to achieve the above object, the vertical displacement measuring and driving structure of the present invention comprises: a body; A frame suspended from the body; A plurality of support beams extending from the frame and connected to the body such that the frame is supported within the body; A movable electrode formed to extend in the frame; And a fixed electrode facing the moving electrode while being supported and floating from the body,

The length of the opposing moving electrode and the fixed electrode in the vertical direction is different from each other.

It is preferable that the inertial mass which is opposed to extend in the frame; is further provided.

The body is a single crystal silicon wafer or an SOI silicon wafer sequentially stacked with a silicon base portion, an insulating layer and a silicon layer, the bottom is the insulating layer, or an SOG silicon wafer sequentially stacked with a glass and silicon layer, The bottom is the glass. At this time, the silicon base portion of the SOI silicon wafer is preferably single crystal silicon or epitaxially grown polysilicon.

When the support beams are torsional springs, the vertical length of all the fixed electrodes of the opposing electrodes is always shorter or longer by a predetermined length than the vertical length of the opposing moving electrode.

In addition, when the support beams are bending springs, one side of the opposing electrodes is shorter by a predetermined length than the length of the vertical direction of the opposite movable electrode in the vertical length of the fixed electrode, and the other side is the vertical length of the movable electrode. Is shorter than the length in the vertical direction of the opposite fixed electrode by a predetermined length.

In order to achieve another object of the present invention, the vertical displacement measurement and drive structure manufacturing method of the present invention comprises the steps of: (a) masking to adjust the etched width of the silicon wafer body; (B) forming trenches having different depths by performing RIE etching with a silicon etching apparatus having a high aspect ratio through the mask; (C) removing the bottom of the trench to form a floating electrode structure above the silicon body; And (d) forming a metal electrode on the surface of the body.

The silicon wafer of step (a) may use a silicon on insulator (SOI) or silicon on glass (SOG) wafer.

If the silicon wafer of step (a) is a single crystal silicon wafer, (e) forming an insulating oxide film on the resultant of step (c) in the body and on the surface; (F) forming a polycrystalline silicon electrode on the oxide film; And (g) insulating the polycrystalline silicon electrode formed on the bottom of the body by anisotropic etching, wherein the step (d) is performed on the polycrystalline silicon electrode formed on the surface of the body after the (bar) step. Forming a metal electrode;

The trenches having different depths in the step (b) are formed with a trench having a lower depth as the etching target width is narrower, and the vertical length of the opposing electrode formed by the step (c) is an electrode formed by a trench having a lower depth. It is preferable that the vertical length of is shorter by a predetermined length than the vertical length of the electrode formed by the trench having a long depth.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view of a vertical displacement measuring and driving structure according to a first embodiment of the present invention, FIG. 2 is a plan view of FIG. 1, and FIG. 3 is a schematic cross-sectional view of a portion cut in the direction of III-III 'of FIG. 4A to 4C illustrate the principle of measuring vertical displacement according to the structure of FIG. 1.

First, referring to FIGS. 1 to 3, in the body 10 of the single crystal silicon wafer, the square frame 32 is formed to float from the bottom of the body 12, and the outer side of the square frame 32 faces the outside. A torsion spring 20 extending in the direction and connected to the inner wall of the body is formed. This torsional spring 20 supports the square frame 32. Inside the rectangular frame 32, there is an inertial mass 34 and a movable comb electrode 30 which are formed to extend in an inward direction therefrom. A fixed comb electrode 40 having a narrow opening 44 is formed between the movable comb electrodes 30. The fixed comb electrodes 40 are connected to the fixed anchor 42 by the anchor horizontal portion 46. Connected and supported from the body bottom 12. That is, the square comb 32 and the moving comb electrode 30 and the inertial mass 34, which are connected therein and floated from the body bottom 12, are supported by the torsion spring 20 to the body 10, The fixed comb electrode 40 suspended from the body bottom 12 is supported on the body 10 by the fixing anchor 42. The vertical length of the fixed comb electrode 40 is shorter than the vertical length of the opposing moving comb electrode 30.

In the vertical displacement measuring and driving structure formed of the electrodes 30 and 40, the capacitance formed between the two electrodes 30 and 40 changes as the moving comb electrode 30 moves away from the fixed comb electrode 40. The vertical displacement is measured. Therefore, when the structure is rotated counterclockwise in the structure formed with the torsion spring 20, as shown in the + Z direction (right direction of the drawing) of FIGS. 4A and 4B, the left capacitance C _left is vertical. The capacitance decreases according to the displacement amount, but the right capacitance C _right maintains a constant capacitance for a predetermined distance. When the structure is rotated in the clockwise direction, as shown in the -Z direction (left side of the figure) of FIGS. 4A and 4B, C _right decreases with vertical displacement and C _left maintains a constant capacitance for a predetermined distance. Accordingly, when the left capacitance is subtracted from the right capacitance, as shown in FIG. 4C, since the capacitance difference C _right -C _left increases and decreases linearly with respect to the vertical displacement, the vertical displacement can be measured by measuring the capacitance difference.

In the above embodiment, the fixed comb electrode 40 is shorter than the movable comb electrode 30 by a predetermined length. However, the fixed comb electrode 40 is longer than the movable comb electrode 30 by a predetermined length. A vertical displacement measuring structure is formed.

In addition, since the fixed comb electrode 40 and the movable comb electrode 30 are horizontally disposed in the structure, adhesion between the electrodes 30 and 40 does not occur even when the movable comb electrode 30 is vertically displaced.

5 is a cross-sectional view of a vertical displacement measurement and drive structure using a silicon on insulator (SOI) silicon wafer as a first modification of the first embodiment, and the same reference for components having the same function as the components of the first embodiment. Use numbers and omit detailed descriptions. Preferably, the silicon base portion is monocrystalline silicon or epitaxially grown polysilicon.

Referring to the drawings, the SOI silicon wafer is formed by sequentially stacking the silicon base portion 13, the insulating layer 14, and the silicon layer 15, and the fixed electrode 40, the moving electrode 30, and the vertical displacement structure. An inertial mass 34 or the like is suspended on the insulating layer 14, and the fixing anchor 42 is fixed on the insulating layer 14.

6 is a cross-sectional view of a vertical displacement measurement and driving structure using a silicon on glass (SOG) silicon wafer as a second modification of the first embodiment, and the same reference for components having the same function as the components of the first embodiment. Use numbers and omit detailed descriptions.

Referring to the drawings, in the SOG silicon wafer, the silicon layer 17 is anodic bonded on the glass 16, and the fixed electrode 40, the moving electrode 30, and the inertial mass 34, which are vertical displacement structures, are formed. ) Is floated on the glass 16, and the fixing anchor 42 is fixed on the glass 16.

Therefore, when the SOI wafer or the SOG wafer is used, since the vertical displacement structure is insulated by the insulating layer 14 and the glass 16, the moving electrode 30 and the fixed electrode 40 as in the case of using a single crystal wafer. Subsequent steps to electrically insulate) may be omitted.

FIG. 7 is a schematic plan view for explaining a second embodiment of the present invention, and FIG. 8 is a schematic cross-sectional view of a portion cut in the Ⅷ-Ⅷ 'direction of FIG. 7, and the same reference numerals are used for objects having the same structure as in the first embodiment. Use numbers and omit detailed descriptions.

Referring to the drawings, the rectangular frame 32 is formed in a floating state from the bottom of the body 12, the bending spring 22 which extends outward from both sides facing the rectangular frame 32 and connected to the inner wall of the body ) Is formed. The bending spring 22 supports the square frame 32. Inside the rectangular frame 32, there is an inertial mass 34 and a movable comb electrode 30 which are formed to extend in an inward direction therefrom. The moving comb electrode 30 on one side (left side in the drawing) has a narrow trench 44 formed therein, and as shown in FIG. 8, the vertical length is larger than the vertical length of the fixed comb electrode 40 formed therebetween. short. On the other hand, the trench 44 having a narrow opening is formed in the fixed comb electrode 40 between the moving comb electrodes 30 on the other side (right side of the drawing), and the vertical length of the moving comb electrode 30 whose vertical length is opposite to each other. It is formed shorter. In addition, as shown in FIG. 8, the structure except the fixed anchor 42 is formed in a floating state from the bottom 12 of the body.

In the vertical displacement measuring and driving structure, the capacitance formed between the two electrodes changes as the moving comb electrode 30 moves away from the fixed comb electrode 40, and the vertical displacement is measured with this change. Therefore, when the structure moves vertically upward (+ z direction), the left capacitance (C _left ) decreases with the amount of vertical displacement, while the right capacitance (C _right ) maintains a constant capacitance for a predetermined distance. When the structure moves vertically downward (-z direction), on the contrary, C _right decreases with the vertical displacement, and C _left maintains a constant capacitance for a predetermined distance. Accordingly, when the capacitance between the left electrodes is subtracted from the right capacitance, as shown in FIG. 4C, since the capacitance difference C _right -C _left increases and decreases linearly with respect to the vertical displacement, the vertical displacement is measured by measuring the capacitance difference.

Meanwhile, although the structure using the single crystal silicon wafer has been described in the second embodiment, an SOI silicon wafer or an SOG silicon wafer may be used instead of the single crystal silicon wafer as shown in FIGS. 5 and 6.

9 is an electron scanning microscope photograph of an accelerometer using a vertical displacement measurement and driving structure supported by a torsion spring, and FIG. 10 is an enlarged photograph of a fixed comb electrode and a moving comb electrode, which are part of FIG. 11 is a result graph using the accelerometer of FIG. 9.

11 shows the frequency response of the accelerometer when a sinusoidal acceleration input of 1 G peak-to-peak 10 Hz is applied to the accelerometer. The signal-to-noise ratio is 100 when a carrier signal of 15 kHz is used. At least one is obtained and from this the noise equivalent acceleration of this accelerometer is calculated as 10 mG.

A method of manufacturing a vertical displacement structure supported by a torsional spring using a single crystal silicon wafer will be described with reference to Figs. 12A to 12F.

First, as shown in FIG. 12A, masking is performed with photoresist (PR) on a single crystal silicon wafer prepared to a predetermined size. At this time, a narrow space 45 which is not masked is formed where a shallow depth electrode is to be formed.

Next, when a reactive ion etching (RIE) is performed using a high-section ratio silicon etching device (not shown) using a Bosch process to make a height difference between electrodes, a thin trench 47 is formed in a narrow unmasked area. Where there is no wide masking, wide and deep trenches 48 are formed, as shown in FIG. 12B. This is due to the RIE lag phenomenon that the larger the trench width, the faster the etch rate and the deeper the etching depth of the silicon.

Next, when the bottom of the trench is removed, the electrode floats from the bottom surface 12 as shown in FIG. Crystal Reactive Etching and Metallization) can also be used. Since the floating process proceeds laterally from the bottom of the trench, the electrode 40 formed by the trench having a lower depth has a shorter vertical length than the electrode 30 formed by the trench having a long depth. The thin electrodes 40 appear to form a pair, but as shown in FIG. 1, these pairs are connected at a predetermined interval, and can be seen that they are supported by the fixing anchor 42.

Next, as shown in FIG. 12D, an insulating oxide film 54 is formed on the body surface and the resultant formed in the previous step for insulation between the electrodes, and then a polycrystalline silicon electrode 56 is formed on the oxide film 54. (See FIG. 12E). Subsequently, the bottom of the body on which the polycrystalline silicon electrode 56 is formed is separated by anisotropic etching (see FIG. 12F).

Meanwhile, a metal electrode 58 for wire bonding is formed on the polycrystalline silicon electrode 56 formed on the surface of the body (see FIG. 12F).

Therefore, no separate patterning work is required to form the electrode, and the vertical displacement measurement and the driving structure can be manufactured by a single photolithography process.

On the other hand, when the SOI silicon wafer or the SOG silicon wafer is used as the body of the structure instead of the single crystal silicon wafer, the bottom surface of the body is made of an insulating layer or glass, thereby forming the insulating layer 54 and The process of forming the polycrystalline silicon electrode 56 and the anisotropic etching of the polycrystalline silicon electrode 56 on the bottom of the body are unnecessary.

As described above, in the vertical displacement measurement and driving structure according to the present invention, the structure and the electrode are simultaneously manufactured to simplify the process. In addition, when used together with the conventional silicon processing method, a six-axis inertial sensor consisting of three angular velocity sensors and three directions of acceleration sensors on the same substrate is produced by simultaneously producing a horizontal and vertical displacement measuring structure in the same wafer. There is an advantage that can be integrated in.

Although the present invention has been described with reference to the embodiments with reference to the drawings, this is only an example, and those skilled in the art will understand that various modifications and equivalent implementations are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined only by the appended claims.

Claims (15)

Body; A frame suspended from the body; A plurality of support beams extending from the frame and connected to the body such that the frame is supported within the body; A movable electrode formed to extend in the frame; And a fixed electrode facing the moving electrode while being supported and floating from the body, Vertical displacement measurement and drive structure, characterized in that the vertical length of the opposite moving electrode and the fixed electrode are different. The method of claim 1, Vertical displacement measurement and drive structure characterized in that it further comprises; an inertial mass extending oppositely in the frame. The method of claim 1, And the body is a single crystal silicon wafer. The method of claim 1, The body is an SOI silicon wafer sequentially stacked with a silicon base portion, an insulating layer and a silicon layer, and the bottom is the insulating layer, the vertical displacement measurement and drive structure. The method of claim 4, wherein And said silicon substrate is single crystal silicon or epitaxially grown polysilicon. The method of claim 1, The body is a SOG silicon wafer sequentially laminated with a glass and a silicon layer, the bottom is the vertical displacement measurement and drive structure, characterized in that the glass. The method of claim 1, And the support beams are torsional springs. The method of claim 7, wherein And the vertical length of all the fixed electrodes of the opposing electrodes is always shorter or longer by a predetermined length than the vertical length of the opposing moving electrode. The method of claim 1, And the support beams are bending springs. The method of claim 9, One side of the opposing electrodes is shorter by a predetermined length than the vertical length of the movable electrode in which the vertical length of the fixed electrode is opposite, and the other side is longer than the vertical length of the fixed electrode in which the vertical length of the movable electrode is opposite. Vertical displacement measurement and drive structure characterized in that it is shorter by a predetermined length. (A) masking to adjust the etched width of the silicon wafer body; (B) forming trenches having different depths by performing RIE etching with a silicon etching apparatus having a high aspect ratio through the mask; (C) removing the bottom of the trench to form a floating electrode structure above the silicon body; And (D) forming a metal electrode on the surface of the body; vertical displacement measurement and drive structure manufacturing method comprising a. The method of claim 11, The method of claim 1, wherein the silicon wafer of step (a) is a silicon on insulator (SOI) or silicon on glass (SOG) wafer. The method of claim 11, The silicon wafer of step (a) is a single crystal silicon wafer, (E) forming an insulating oxide film on the resultant of step (c) in the body and the surface; (F) forming a polycrystalline silicon electrode on the oxide film; And (G) insulating the polycrystalline silicon electrode formed on the bottom of the body by anisotropic etching; And (d) forming a metal electrode on the polycrystalline silicon electrode formed on the surface of the body after the (bar) step. The method according to claim 12 or 13, The trench having different depths in the step (b) is characterized in that a trench having a lower depth is formed as the etching target width is narrower. The method according to claim 12 or 13, The vertical length of the opposite electrode formed by the step (c) is a vertical displacement of the vertical length of the electrode formed by the trench having a lower depth by a predetermined length than the vertical length of the electrode formed by the trench having a long depth. Method of manufacturing measurement and drive structures.