KR100408528B1 - A microgyroscope and a method therefor - Google Patents

Abstract

PURPOSE: A high-sensitivity micro gyroscope and a manufacturing method thereof are provided to easily process a signal and largely reduce the manufacturing cost by making the detected capacitance of a sensing plate be linearly proportion to the angular velocity. CONSTITUTION: A high-sensitivity micro gyroscope comprises a substrate; a suspended vibrating plate(60a) suspended on the substrate and composed of comb teeth formed at the edge and a plurality of rectangular through-holes arranged in the center; an angular velocity sensing plate(60b) fixed on the substrate, connected to an electrode, and formed with rectangular protruded plate members inserted into the rectangular through-holes of the vibrating plate; and an exciting plate(60c) including comb teeth crossing the comb teeth formed at the edge of the suspended vibrating plate. The suspended vibrating plate and the angular velocity sensing plate are multilayer formed by alternately layering polycrystal silicon layers and silicon nitride layers.

Description

High sensitivity micro gyroscope and its manufacturing method {A microgyroscope and a method therefor}

The present invention relates to a microgyroscope for detecting an inertial angular velocity of an object and a method of manufacturing the same, and more particularly, to a vibration type microgyroscope having excellent angular velocity sensing sensitivity and easy signal processing.

As shown in FIG. 1, the vibrating microgyroscope has a suspension structure oscillated in the x-axis direction when the suspension structure is rotated in the Z-axis direction by the force of Coriolis when a rotational force of angular velocity Ω around the y-axis is given. It is a sensor that detects the displacement ΔZ and detects any external angular velocity Ω by detecting the displacement ΔZ and signal processing.

Vibration type micro gyroscopes are being applied to a wide range of applications, such as those applied to automobile auto navigation systems or camcorders. Miniaturization of the gyroscope size is an essential requirement when it is mounted on a camcorder. Recently, CSDL of USA and Murata of Japan have already developed a vibrating microgyroscope using silicon process. It was produced and presented.

As an example of a conventional microgyroscope, a schematic perspective view of a CSDL micro gyroscope is shown in FIG. 2. As shown, the microgyroscope generates an electrostatic force at the comb structure 102 by applying an alternating voltage to the excitation electrode 101. Since only the attractive force exists, the inertial mass 103 is excited in directions opposite to each other in the x-axis direction. When an angular velocity Ω is input from the outside, a Coliolis force of 2 × m × Ω × v acts in the z-axis direction so that the inertial masses 103 vibrate in opposite directions in the z-axis direction. At this time, the capacitance between the sensing electrode 105 and the inertial mass 103 formed on the substrate 104 is inversely proportional to the distance between the inertial mass 103 and the sensing electrode 105. Therefore, by measuring the change in capacitance between the two inertial masses 103 and the sensing electrode 105, the Coriolis force can be measured, thereby obtaining the angular velocity Ω.

Here, the two inertial masses 103 are used to reduce the influence of noise generated in the two inertial masses 103 or the change in output caused by line acceleration, angular acceleration, temperature change, or the like. That is, by dividing the outputs from the two inertial masses 103, such noise cancels each other and the sense signal is doubled. For this reason, having two inertial masses is essential in a gyro.

To achieve good performance as a gyroscope, the two inertial masses must resonate at the same resonant frequency. If the resonant frequency of the two inertial masses differs due to manufacturing errors or other reasons in a gyroscope with two inertial masses, the excitation and sensing circuits become very complicated because the performance is degraded or the respective inertial masses must be detected and detected at two frequencies. For this reason, when designing a gyroscope, two inertial masses are designed to be tuned to each other.

This tuning structure is also used in CSDL's microgyroscopes. The tuning effect of this tuning structure is apparent as the width of the support beam 106 becomes thinner. 3A and 3B show the vibration modes of excitation of the microgyroscope of the CSDL. However, even when the width of the support beam 106 is too thin, as shown in FIG. 3B, the support beam 106 itself is not only bent, resulting in large structural damping but also excellent stability of the gyroscope. Falls out. In order to reduce the structural deflection, when the width of the support beam 106 is increased, the two inertial masses 103 become independent structures and have different resonant frequencies even by a small fabrication error.

4A and 4B also show sensing vibration modes of the gyroscope of the CSDL. As shown in FIG. 4A, the inertial mass 103 may oscillate obliquely with respect to the substrate 104 plane depending on the width of the support beam 106. Thus, the capacitance change between the inertial mass 103 and the sensing electrode 105 has a secondary nonlinearity.

Furthermore, the microgyro of the two companies has an angular velocity sensing sensitivity of only a few degrees / sec, and there is a problem that the signal processing circuit is complicated.

The present invention was devised to improve the above problems, and an object thereof is to provide a vibration type micro gyroscope having a linear angular velocity sensing sensitivity and a simple signal processing circuit and a method of manufacturing the same.

1 is an explanatory diagram for explaining the direction of Coriolis force,

2 is a schematic perspective view of a CSDL micro gyroscope as an example of a conventional micro gyroscope;

3A and 3B are diagrams illustrating an oscillation mode of the microgyroscope of FIG. 2,

Figure 3a is a front view, Figure 3b is a plan view,

4A and 4B are diagrams illustrating a sensing vibration mode of the microgyroscope of FIG. 1.

Figure 4a is a front view, Figure 4b is a plan view,

5A to 5C are cross-sectional views of a high sensitivity microgyroscope according to the present invention.

5a is a plan view,

5B is a cross-sectional view taken along the line AA ′ of FIG. 5A;

5C is a cross-sectional view taken along the line BB ′ of FIG. 5A;

FIG. 5D is a perspective view illustrating an excitation plate and a suspension diaphragm of FIG. 5A;

6A to 6E are cross-sectional views after the step-by-step process of manufacturing the microgyroscope of FIGS. 6A to 6D.

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

10. Silicon Substrate 20. Silicon oxide

30. Silicon nitride film Wiring pattern

50.PSG Pattern

60. Multiple layers of polycrystalline silicon / silicon nitride film

60a. Suspension diaphragm 60b. Angular Velocity Sensing Plate (Rectangular Protruding Plate Member)

60c. With plate 60d. Direction detection plate

70. Metal Electrode

101. Excitation electrode 102. Comb structure

103. Inertial masses (suspended structures) Board

105. Sense Electrode

In order to achieve the above object, a vibration type micro gyroscope according to the present invention includes a substrate; Suspension diaphragm floating on the substrate, the comb teeth are formed at the edge thereof, the plurality of rectangular through holes formed in the center; An angular velocity detecting plate fixed on the substrate and connected to an electrode, the angular velocity detecting plate formed of rectangular protruding plate members respectively inserted into rectangular through holes of the diaphragm; And an excitation plate having comb teeth intersecting with the comb teeth formed at one edge of the suspension diaphragm.

In the present invention, the suspension vibration plate and the angular velocity detection plate is preferably formed of a multilayer in which a polycrystalline silicon layer and a silicon nitride layer are alternately stacked,

It is preferable to further provide an excitation direction sensing plate having a comb teeth intersecting the comb teeth formed on the other edge of the suspension diaphragm.

In addition, in order to achieve the above object, a method of manufacturing a vibrating microgyroscope according to the present invention, (A) forming an oxide film on a silicon substrate; (B) depositing a silicon nitride film on the silicon oxide film; (C) forming a wiring pattern with polycrystalline silicon for wiring on the silicon nitride film; (D) depositing and selectively etching a sacrificial PSG film on the wiring pattern to form a predetermined PSG sacrificial pattern; (E) growing a multilayer of polycrystalline silicon / silicon nitride film on the PSG sacrificial pattern; (F) selectively etching the multiple layers of the polycrystalline silicon / silicon nitride film by dry etching to form a pattern for a structure; (G) forming a metal electrode on the structure pattern; And (h) removing the PSG sacrificial pattern.

In the present invention, it is preferable to use reactive ion etching or inductively coupled etching as the dry etching method in the step (bar).

With reference to the drawings will be described in detail a vibrating microgyroscope and a method for manufacturing the same according to the present invention.

In order to solve the conventional problems, in the present invention, as shown in FIG. 5, the structure of the portion detecting the displacement by the force of Coriolis is designed such that the capacitance changes linearly with respect to the displacement, and the structure is polycrystalline. It consists of multiple layers of silicon and silicon nitride film. Detailed manufacturing process is as follows.

First, as shown in FIG. 6A, a thick oxide film 20 is formed on the surface of the silicon substrate 10, and the silicon nitride film 30 is deposited thereon. This is to reduce the parasitic capacitance between the structures formed during manufacturing and driving. Next, the wiring polycrystalline silicon is deposited and the wiring pattern 40 is formed through a photolithography process.

Next, as shown in FIG. 6B, a PSG layer is deposited on the sacrificial layer and selectively etched to form a predetermined PSG pattern 50.

Next, as shown in FIG. 6C, a multilayer 60 of polycrystalline silicon / silicon nitride film is grown on the PSG sacrificial pattern 50 and then the multilayer is subjected to reactive ion etching (RIE), induction. A pattern for a structure is formed by selectively etching by inductively coupled plasma atomic etching (ICP).

Next, as shown in FIG. 6D, the metal for the electrode is deposited and the metal electrode 70 is formed by a lift-off technique.

Next, as shown in FIG. 6E, the structure is completed by removing the PSG sacrificial pattern 50.

The configuration and operation of the manufactured gyroscope will be described with reference to FIGS. 5A to 5D.

As shown, the microgyroscope according to the present invention includes a suspension diaphragm 60a on a substrate. This suspension diaphragm 60a floats on a board | substrate, and the comb teeth are formed in each edge of the square structure, and several rectangular through-holes are formed in the center part. In addition, an angular velocity detecting plate 60b is provided, which is fixed on the substrate and connected to an electrode (hatched display area) by rectangular protrusion plate members 60b respectively inserted into rectangular through holes of the suspension diaphragm 60a. Is formed. And, it is also provided with an excitation plate 60c, which is provided with a comb teeth intersecting the comb teeth formed on the left edge of the suspension vibration plate (60a). In particular, the protruding plate member of the suspension diaphragm 60a and the angular velocity detecting plate 60b is formed of a multilayer in which a polycrystalline silicon layer and a silicon nitride layer are alternately stacked to increase sensing sensitivity of the angular velocity. Further, further comprising an excitation direction detecting plate 60d having a comb teeth intersecting with the comb teeth formed on the right edge of the suspension diaphragm 60a, by maintaining the excitation direction at a constant speed, the generation of the Coriolis force is accurately input. Try to happen proportionally. 5D clearly shows the arrangement relationship between the suspension structure 60a and the protruding plate member 60b of the excitation plate.

As shown in FIG. 5A, the microgyroscope having such a structure vibrates the structure in the x-axis direction, and when a certain rotational force (angular velocity) with the y-axis is applied to the structure, the force in the z-axis direction. The so-called Coriolis force occurs. Due to this Coriolis force, the structure vibrates in the z-axis direction, wherein the capacitance between the sensing electrode 40 and the suspension vibration structure 60a is linear to the displacement in the z-axis direction of the suspension vibration structure 60a. Will be proportional to However, as shown in FIGS. 5B and 5C, when the stacking period of the structures 60 (60a, 60b) formed of multiple layers of the polycrystalline silicon layer and the silicon nitride film is equal to or slightly larger than the maximum displacement that the structure can cause, the capacitance The displacement ratio can be greatly improved. If the capacitance is linearly proportional to the displacement (displacement is proportional to the magnitude of the angular velocity), the amount of angular velocity can be easily detected from the capacitance during signal processing, and the same noise exists when the capacitance: displacement ratio is large. In this situation, the sensitivity of angular velocity detection can be improved compared to the case where the capacitance: displacement ratio is low.

As described above, the high-sensitivity microgyroscope according to the present invention has a suspension diaphragm which floats on a substrate, has comb teeth formed at each edge of the rectangular structure, and has a plurality of rectangular through-holes formed at the center thereof. By inserting the rectangular protruding plate members of the angular velocity detecting plate into the rectangular through-holes, and having a vibrating plate on one side of the suspended diaphragm to have a suspended diaphragm, the detection capacitance of the sensing plate is increased by the angular velocity. Linearly proportional to, signal processing is easy and simple, greatly reducing the fabrication cost of the sensor. In addition, by providing a direction detecting plate provided on the other edge of the suspension diaphragm to maintain a constant direction, the generation of Coriolis force is caused to occur in proportion to the input angular velocity accurately. Furthermore, the protruding plate members of the suspension diaphragm and the angular velocity sensing plate were formed of multiple layers in which polycrystalline silicon layers and silicon nitride layers were alternately stacked, thereby significantly increasing the sensitivity to the angular velocity. In addition, the above structure has a large capacitance: angular velocity ratio, so that the angular velocity detection resolution can be increased, and thus it can be applied to various systems requiring a high performance gyroscope.

Claims (4)

Board; Suspension diaphragm floating on the substrate, the comb teeth are formed at the edge thereof, the plurality of rectangular through holes formed in the center; An angular velocity detecting plate fixed on the substrate and connected to an electrode, the angular velocity detecting plate formed of rectangular protruding plate members respectively inserted into rectangular through holes of the diaphragm; And An excitation plate having comb teeth intersecting with the comb teeth formed at one edge of the suspension diaphragm; Micro gyroscope, characterized in that provided. The method of claim 1, And said suspension diaphragm and said angular velocity sensing plate are formed of multiple layers in which a polycrystalline silicon layer and a silicon nitride layer are alternately stacked. The method of claim 1, And a direction detecting plate having comb teeth intersecting with the comb teeth formed on the other edge of the suspension diaphragm. The method of claim 1, And the suspended diaphragm is floating above the upper portion of the rectangular protruding plate member of the angular velocity detecting plate.