JP2012018004A - Etching method of semiconductor substrate and manufacturing method of capacitance type micro electromechanical system (mems) sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a etching method of semiconductor substrate, capable of forming a recess having an accurately controlled depth without depending on a shape or a size of an etching pattern.SOLUTION: In a first step of etching a semiconductor substrate 3, anisotropic deep reactive ion etching is performed using a resist mask 59 having a large number of openings 88 of the same pattern at positions opposing to etching regions 87 independently partitioned to each other. A large number of recesses 89 having approximately the same depth are thereby formed on a surface of the semiconductor substrate 3. In a second step, side walls 90 defining a large number of recesses 89 of the semiconductor substrate 3 are removed by etching in lateral direction parallel to the surface of the semiconductor substrate 3.

Description

  The present invention relates to a method for etching a semiconductor substrate and a method for manufacturing a capacitive MEMS sensor using the same.

In recent years, MEMS devices have attracted attention because devices using MEMS (Micro Electro Mechanical Systems) technology have begun to be installed in mobile phones and the like.
As a technique for etching at a high aspect ratio in manufacturing a MEMS device, deep reactive ion etching (DIE) is known.

Special table 2007-519891 gazette

In the deep RIE, the etching rate differs depending on the shape of the etching pattern in the semiconductor substrate. Therefore, when etching patterns having different shapes and sizes are mixed during the fabrication of the MEMS device, the depths of the recesses formed by the deep digging RIE vary from pattern to pattern.
An object of the present invention is to provide a method for etching a semiconductor substrate capable of forming a recess having a precisely controlled depth regardless of the shape or size of the etching region.

  Another object of the present invention is to provide a method for manufacturing a capacitive MEMS sensor capable of manufacturing a pair of electrodes (first electrode and second electrode) for detecting a change in capacitance as designed. Is to provide.

  The method for etching a semiconductor substrate according to claim 1 for achieving the above object is a method for selectively etching the etching region of the semiconductor substrate in which the etching region is defined, wherein a plurality of locations in the etching region are provided. Forming a plurality of first recesses having openings of the same shape and size in the etching region by deep reactive ion etching in a predetermined pattern from the semiconductor, and the semiconductor defining the plurality of first recesses Forming a second recess in which the plurality of first recesses are integrated in the etching region by removing the side wall of the substrate by isotropic ion etching.

  According to this method, the second recess is formed in the etching region defined in the semiconductor substrate. Prior to the formation of the second recess, the semiconductor substrate is deeply reactive ion etched in a predetermined pattern from a plurality of locations in the etching region. That is, the deep reactive ion etching is performed on the semiconductor in the etching region with the same pattern (opening pattern having the same shape and size). Therefore, the etching rate when forming the plurality of first recesses in the etching region can be made substantially equal. As a result, by executing the deep reactive ion etching process, it is possible to form a plurality of first recesses having substantially the same depth in the etching region. Then, by removing the sidewall of the semiconductor substrate defining the plurality of first recesses by isotropic ion etching, the plurality of first recesses are integrated, thereby forming a second recess that occupies the etching region. The Thereby, the etching region of the semiconductor substrate can be selectively etched.

  That is, according to this method, as a first step, a plurality of first recesses are formed by performing deep reactive ion etching on a semiconductor substrate vertically with a pattern having a uniform shape and size. Thereby, a 2nd recessed part can be formed in the depth as designed. Therefore, the second recess having a precisely controlled depth can be formed in the semiconductor substrate regardless of the shape or size of the etching region.

  Therefore, as shown in claim 2, even when the first etching region and the second etching region having different shapes or sizes are mixed in the semiconductor substrate, as the first step, an opening pattern having the same shape and size is used. By vertically deep reactive ion etching of the semiconductor substrate, a plurality of first recesses are simultaneously formed in the first and second etching regions, and the semiconductor substrate is laterally isotropic as a second step. Ion etching may be performed. Thereby, the depth of the 2nd recessed part formed in a 1st etching area | region and the depth of the 2nd recessed part formed in a 2nd etching area | region can be arrange | equalized substantially equally.

And this etching method can be suitably employ | adopted for the manufacturing method of an electrostatic capacitance type MEMS sensor, for example.
Specifically, as shown in claim 3, a semiconductor substrate, a first electrode formed on a surface portion of the semiconductor substrate, and a surface formed on the surface portion of the semiconductor substrate, the first electrode A method for manufacturing a capacitive MEMS sensor including a second electrode facing each other with a gap, wherein the first and second electrodes are formed outside a region where the first electrode and the second electrode are to be formed. A step of defining an etching region so as to define a region to be formed, and a plurality of first openings having the same shape and size by performing deep reactive ion etching in a predetermined pattern from a plurality of locations in the etching region. Forming a plurality of first recesses in the etching region, and removing the side walls of the semiconductor substrate defining the plurality of first recesses by isotropic ion etching. The conjugated been second recess formed in the etched region may be performed and the step of forming the first and second electrodes at the same time.

  Accordingly, the depth of the second recess can be accurately controlled, so that the first region can be formed in any shape or size that is defined for partitioning the first electrode and the second electrode. The electrode and the second electrode can be formed with a thickness as designed (thickness in the thickness direction of the semiconductor substrate).

FIG. 1 is a schematic plan view of a gyro sensor. FIG. 2 is a schematic plan view of the sensor unit shown in FIG. FIG. 3 is a plan view of an essential part of the X-axis sensor shown in FIG. 4 is a cross-sectional view of the main part of the X-axis sensor shown in FIG. 2, and is a cross-sectional view taken along the section line IV-IV in FIG. FIG. 5 is a plan view of the main part of the Z-axis sensor shown in FIG. 6 is a cross-sectional view of the main part of the Z-axis sensor shown in FIG. 2, and is a cross-sectional view taken along the cutting line VI-VI of FIG. 7 is a cross-sectional view of the main part of the Z-axis sensor shown in FIG. 2, and is a cross-sectional view taken along the cutting line VII-VII in FIG. FIG. 8 is a schematic cross-sectional view of the integrated circuit shown in FIG. FIG. 9A is a schematic cross-sectional view showing the manufacturing process of the gyro sensor according to one embodiment of the present invention, and shows a cut surface at the same position as FIG. FIG. 9B is a schematic cross-sectional view showing the manufacturing process of the gyro sensor according to one embodiment of the present invention, and shows a cut surface at the same position as FIG. 6. FIG. 9C is a schematic cross-sectional view showing the manufacturing process of the gyro sensor according to one embodiment of the present invention, and shows a cut surface at the same position as FIG. FIG. 10A is a schematic cross-sectional view showing a step subsequent to FIG. 9A. FIG. 10B is a schematic cross-sectional view showing a step subsequent to FIG. 9B. FIG. 10C is a schematic cross-sectional view showing a step subsequent to FIG. 9C. FIG. 11A is a schematic cross-sectional view showing a step subsequent to FIG. 10A. FIG. 11B is a schematic cross-sectional view showing a step subsequent to FIG. 10B. FIG. 11C is a schematic cross-sectional view showing a step subsequent to FIG. 10C. FIG. 12A is a schematic cross-sectional view showing a step subsequent to FIG. 11A. FIG. 12B is a schematic cross-sectional view showing a step subsequent to FIG. 11B. FIG. 12C is a schematic cross-sectional view showing a step subsequent to FIG. 11C. FIG. 13A is a schematic cross-sectional view showing a step subsequent to FIG. 12A. FIG. 13B is a schematic cross-sectional view showing a step subsequent to FIG. 12B. FIG. 13C is a schematic cross-sectional view showing a step subsequent to FIG. 12C. FIG. 14A is a schematic sectional view showing a step subsequent to FIG. 13A. FIG. 14B is a schematic cross-sectional view showing a step subsequent to FIG. 13B. FIG. 14C is a schematic cross-sectional view showing a step subsequent to FIG. 13C. FIG. 15A is a schematic cross-sectional view showing a step subsequent to FIG. 14A. FIG. 15B is a schematic cross-sectional view showing a step subsequent to FIG. 14B. FIG. 15C is a schematic cross-sectional view showing a step subsequent to FIG. 14C. FIG. 16A is a schematic cross-sectional view showing a step subsequent to FIG. 15A. FIG. 16B is a schematic cross-sectional view showing a step subsequent to FIG. 15B. FIG. 16C is a schematic cross-sectional view showing a step subsequent to FIG. 15C. FIG. 17A is a schematic cross-sectional view showing a step subsequent to FIG. 16A. FIG. 17B is a schematic cross-sectional view showing a step subsequent to FIG. 16B. FIG. 17C is a schematic cross-sectional view showing a step subsequent to FIG. 16C. FIG. 18A is a schematic sectional view showing a step subsequent to FIG. 17A. FIG. 18B is a schematic cross-sectional view showing a step subsequent to FIG. 17B. FIG. 18C is a schematic cross-sectional view showing a step subsequent to FIG. 17C. FIG. 19A is a schematic sectional view showing a step subsequent to FIG. 18A. FIG. 19B is a schematic cross-sectional view showing a step subsequent to FIG. 18B. FIG. 19C is a schematic cross-sectional view showing a step subsequent to FIG. 18C. FIG. 20A is a schematic cross-sectional view showing a step subsequent to FIG. 19A. FIG. 20B is a schematic cross-sectional view showing a step subsequent to FIG. 19B. FIG. 20C is a schematic cross-sectional view showing a step subsequent to FIG. 19C. FIG. 21A is a schematic cross-sectional view showing a step subsequent to FIG. 20A. FIG. 21B is a schematic cross-sectional view showing a step subsequent to FIG. 20B. FIG. 21C is a schematic cross-sectional view showing a step subsequent to FIG. 20C. FIG. 22A is a schematic sectional view showing a step subsequent to FIG. 21A. FIG. 22B is a schematic cross-sectional view showing a step subsequent to FIG. 21B. FIG. 22C is a schematic cross-sectional view showing a step subsequent to FIG. 21C. FIG. 23A is a schematic sectional view showing a step subsequent to FIG. 22A. FIG. 23B is a schematic cross-sectional view showing a step subsequent to FIG. 22B. FIG. 23C is a schematic cross-sectional view showing a step subsequent to FIG. 22C. FIG. 24A is a schematic sectional view showing a step subsequent to FIG. 23A. FIG. 24B is a schematic sectional view showing a step subsequent to FIG. 23B. FIG. 24C is a schematic sectional view showing a step subsequent to FIG. 23C. FIG. 25A is a schematic sectional view showing a step subsequent to FIG. 24A. FIG. 25B is a schematic sectional view showing a step subsequent to FIG. 24B. FIG. 25C is a schematic cross-sectional view showing a step subsequent to FIG. 24C. FIG. 26A is a schematic sectional view showing a step subsequent to FIG. 25A. FIG. 26B is a schematic cross-sectional view showing a step subsequent to FIG. 25B. FIG. 26C is a schematic cross-sectional view showing a step subsequent to FIG. 25C. FIG. 27A is a schematic sectional view showing a step subsequent to FIG. 26A. FIG. 27B is a schematic cross-sectional view showing a step subsequent to FIG. 26B. FIG. 27C is a schematic cross-sectional view showing a step subsequent to FIG. 26C. FIG. 28A is a schematic sectional view showing a step subsequent to FIG. 27A. FIG. 28B is a schematic cross-sectional view showing a step subsequent to FIG. 27B. FIG. 28C is a schematic cross-sectional view showing a step subsequent to FIG. 27C. FIG. 29A is a schematic sectional view showing a step subsequent to FIG. 28A. FIG. 29B is a schematic sectional view showing a step subsequent to FIG. 28B. FIG. 29C is a schematic cross-sectional view showing a step subsequent to FIG. 28C. FIG. 30A is a schematic sectional view showing a step subsequent to FIG. 29A. FIG. 30B is a schematic sectional view showing a step subsequent to FIG. 29B. FIG. 30C is a schematic cross-sectional view showing a step subsequent to FIG. 29C. FIG. 31A is a schematic cross-sectional view showing a step subsequent to FIG. 30A. FIG. 31B is a schematic cross-sectional view showing a step subsequent to FIG. 30B. FIG. 31C is a schematic cross-sectional view showing a step subsequent to FIG. 30C. FIG. 32A is a schematic sectional view showing a step subsequent to FIG. 31A. FIG. 32B is a schematic cross-sectional view showing a step subsequent to FIG. 31B. FIG. 32C is a schematic cross-sectional view showing a step subsequent to FIG. 31C. FIG. 33A is a schematic sectional view showing a step subsequent to FIG. 32A. FIG. 33B is a schematic cross-sectional view showing a step subsequent to FIG. 32B. FIG. 33C is a schematic cross-sectional view showing a step subsequent to FIG. 32C. FIG. 34A is a schematic sectional view showing a step subsequent to FIG. 33A. FIG. 34B is a schematic cross-sectional view showing a step subsequent to FIG. 33B. FIG. 34C is a schematic cross-sectional view showing a step subsequent to FIG. 33C. FIG. 35A is a schematic sectional view showing a step subsequent to FIG. 34A. FIG. 35B is a schematic cross-sectional view showing a step subsequent to FIG. 34B. FIG. 35C is a schematic cross-sectional view showing a step subsequent to FIG. 34C. FIG. 36A is a schematic sectional view showing a step subsequent to FIG. 35A. FIG. 36B is a schematic sectional view showing a step subsequent to FIG. 35B. FIG. 36C is a schematic cross-sectional view showing a step subsequent to FIG. 35C. FIG. 37 is a schematic plan view of the semiconductor substrate in the step of FIG. 31A. FIG. 38 is a schematic plan view of the semiconductor substrate in the step of FIG. 31B.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
<Overall configuration of gyro sensor>
First, the overall configuration of the gyro sensor will be described with reference to FIG.
FIG. 1 is a schematic plan view of a gyro sensor. In FIG. 1, a part of the portion sealed in the resin package is shown in a transparent state.

  The gyro sensor 1 is a capacitance type that is detected based on a change in capacitance of a capacitance element, and includes, for example, camera shake correction of a video camera or a still camera, position detection of a car navigation system, motion detection of a robot or a game machine, etc. Used for applications. The gyro sensor 1 has an outer shape of a rectangular parallelepiped-shaped (square shape in plan view) defined by a resin package 2.

The gyro sensor 1 includes a semiconductor substrate 3 having a rectangular shape in plan view, a sensor unit 4 disposed in the center of the semiconductor substrate 3, and an integrated circuit 5 (ASIC) disposed in the periphery of the semiconductor substrate 3 surrounding the sensor unit 4. : Application Specific Integrated Circuit).
The sensor unit 4 includes an X-axis sensor 6, a Y-axis sensor 7, and a Z-axis sensor 8 as sensors for detecting angular velocities around three axes that are orthogonal in a three-dimensional space.

  The X-axis sensor 6 uses the vibration Ux in the X-axis direction to generate a Coriolis force Fz in the Z-axis direction when the gyro sensor 1 is tilted, and detects a change in capacitance due to the Coriolis force. The angular velocity ωy acting around the Y axis is detected. The Y-axis sensor 7 uses the vibration Uy in the Y-axis direction to generate a Coriolis force Fx in the X-axis direction when the gyro sensor 1 is tilted, and detects a change in capacitance due to the Coriolis force. Thus, the angular velocity ωz acting around the Z axis is detected. The Z-axis sensor 8 uses the vibration Uz in the Z-axis direction to generate a Coriolis force Fy in the Y-axis direction when the gyro sensor 1 is tilted, and detects a change in capacitance due to the Coriolis force. Thus, the angular velocity ωx acting around the X axis is detected.

The integrated circuit 5 performs, for example, a charge amplifier that amplifies the electric signal output from each sensor, a filter circuit (low-pass filter: LPF, etc.) that extracts a specific frequency component of the electric signal, and performs a logical operation on the filtered electric signal. A logic circuit is included, and is constituted by, for example, a CMOS device.
Further, in this embodiment, five electrode pads 9 are provided on the surface of the gyro sensor 1 at each of a pair of edge portions facing each other with the sensor unit 4 interposed therebetween in a plan view. The electrode pads 9 are arranged along the respective edges at equal intervals. These electrode pads 9 include, for example, pads for applying a voltage to the sensor unit 4 and the integrated circuit 5.
<Configuration of X-axis sensor and Y-axis sensor>
Next, the configuration of the X-axis sensor and the Y-axis sensor will be described with reference to FIGS.

FIG. 2 is a schematic plan view of the sensor unit shown in FIG. FIG. 3 is a plan view of an essential part of the X-axis sensor shown in FIG. 4 is a cross-sectional view of the main part of the X-axis sensor shown in FIG. 2, and is a cross-sectional view taken along the section line IV-IV in FIG.
The semiconductor substrate 3 is made of a conductive silicon substrate (for example, a low resistance substrate having a resistivity of 1 mΩ · m to 30 Ω · m, preferably 5 mΩ · m to 25 mΩ · m). The semiconductor substrate 3 has a cavity 10 inside, and an X-axis sensor 6 and a Y-axis sensor 7 are formed on an upper wall 11 (surface portion) of the semiconductor substrate 3 having a top surface that partitions the cavity 10 from the surface side. And the Z-axis sensor 8 is formed. That is, the X-axis sensor 6, the Y-axis sensor 7, and the Z-axis sensor 8 are part of the semiconductor substrate 3 and floated with respect to the bottom wall 12 of the semiconductor substrate 3 having a bottom surface that divides the cavity 10 from the back surface side. It is supported by.

Further, on the surface of the semiconductor substrate 3, a part of wiring included in these sensors is exposed as a pad 13 on both sides opposed to each other with the cavity 10 interposed therebetween. These pads 13 are electrically connected to the electrode pads 9 by, for example, bonding wires (not shown) when packaged by the resin package 2.
The X-axis sensor 6 and the Y-axis sensor 7 are disposed adjacent to each other with a space therebetween, and the Z-axis sensor 8 is disposed so as to surround each of the X-axis sensor 6 and the Y-axis sensor 7. In this embodiment, the Y-axis sensor 7 has substantially the same configuration as that obtained by rotating the X-axis sensor 6 by 90 ° in plan view. Therefore, in the following, the configuration of the Y-axis sensor 7 will be replaced with a specific description by describing the portions corresponding to the respective portions in parentheses when describing the respective portions of the X-axis sensor 6.

  A support portion 14 is formed between the X-axis sensor 6 and the Z-axis sensor 8 and between the Y-axis sensor 7 and the Z-axis sensor 8 to support them in a floating state. The support portion 14 extends from one side wall 15 having a side surface that divides the cavity 10 of the semiconductor substrate 3 from the lateral side, extends across the Z-axis sensor 8 toward the X-axis sensor 6 and the Y-axis sensor 7, and An annular portion 17 surrounding the X-axis sensor 6 and the Y-axis sensor 7 is integrally included.

The X-axis sensor 6 and the Y-axis sensor 7 are arranged inside the individual annular portions 17 and are supported at two opposite positions on the inner wall of the annular portion 17. The Z-axis sensor 8 is supported on both side walls of the linear portion 16.
The X-axis sensor 6 (Y-axis sensor 7) has an X fixed electrode 21 (Y fixed electrode 41) as a first electrode fixed to the support portion 14 provided in the cavity 10, and the X fixed electrode 21. It has X movable electrode 22 (Y movable electrode 42) as the 2nd electrode held so that vibration is possible. The X fixed electrode 21 and the X movable electrode 22 are formed with the same thickness.

The X fixed electrode 21 (Y fixed electrode 41) is spaced from the base portion 23 (base portion 43 of the Y fixed electrode 41) having a square shape in plan view fixed to the support portion 14, along the inner wall of the base portion 23. And a plurality of sets of electrode portions 24 (electrode portions 44 of the Y fixed electrode 41) arranged in a comb-like shape.
On the other hand, the X movable electrode 22 (Y movable electrode 42) extends in a direction crossing the electrode portion 24 of the X fixed electrode 21, and both ends of the beam portion 25 (beam of the Y-axis sensor 7) can be expanded and contracted along the direction. The base part 26 (the base part 46 of the Y movable electrode 42) connected to the base part 23 of the X fixed electrode 21 via the part 45), and the electrode part 24 of the X fixed electrode 21 adjacent to each other from the base part 26. It includes an electrode part 27 (electrode part 47 of the Y movable electrode 42) arranged in a comb-teeth shape that extends to both sides and meshes so as not to contact the electrode part 24 of the X fixed electrode 21.

In the X-axis sensor 6, the beam portion 25 expands and contracts and the base portion 26 of the X movable electrode 22 vibrates (vibrates Ux) along the surface of the semiconductor substrate 3, so that the electrode portion 24 of the X fixed electrode 21 has comb teeth. The individual electrode portions 27 of the X movable electrode 22 meshed with each other vibrate alternately in a direction toward and away from the electrode portion 24 of the X fixed electrode 21.
The base portion 23 of the X fixed electrode 21 has a linear main frame extending in parallel with each other, and a reinforcing frame is combined with the main frame so that a triangular space is repeated along the main frame. It has a truss-like frame structure.

  The electrode portions 24 of the X fixed electrode 21 are equal to each other, with each base end portion connected to the base portion 23 and a pair of two electrode portions in a straight line in plan view whose front ends face each other. A plurality are provided at intervals. Each electrode part 24 has a frame structure in a ladder shape in plan view including a linear main frame extending in parallel with each other and a plurality of horizontal frames constructed between the main frames.

On the other hand, the base portion 26 of the X movable electrode 22 includes a plurality of (six in this embodiment) linear frames extending in parallel with each other, and both ends thereof are connected to the beam portion 25. Two beam portions 25 are provided at both ends of the base portion 26 of the X movable electrode 22.
The electrode portion 27 of the X movable electrode 22 is a planar view ladder including a linear main frame extending in parallel with each other across each frame of the base portion 26 and a plurality of horizontal frames constructed between the main frames. It has a frame structure.

  Further, in the X movable electrode 22, the insulating layer 28 that crosses the horizontal frame from the surface to the cavity 10 on a line that divides each electrode portion 27 into two along the direction orthogonal to the vibration direction Ux (this implementation) In the form, silicon oxide) is embedded. By this insulating layer 28, each electrode part 27 is insulated and separated into two on one side and the other side along the vibration direction Ux. Thereby, the separated electrode portions 27 of the X movable electrode 22 function as independent electrodes in the X movable electrode 22.

A first insulating film 33 and a second insulating film 34 made of silicon oxide (SiO ₂ ) are sequentially stacked on the surface of the semiconductor substrate 3 including the X fixed electrode 21 and the X movable electrode 22, and this second insulating film An X first drive / detection line 29 (Y first drive / detection line 49) and an X second drive / detection line 30 (Y second drive / detection line 50) are formed on the line 34.
The X first drive / detection wiring 29 supplies a drive voltage to one side (in this embodiment, the left side in FIG. 3) of each electrode part 27 insulated and separated from the two, and from the electrode part 27 A change in voltage associated with a change in capacitance is detected. On the other hand, the X second drive / detection wiring 30 supplies a drive voltage to the other side (in this embodiment, the right side of FIG. 3) of each electrode part 27 that is insulated and separated into two, A change in voltage accompanying a change in capacitance is detected from the electrode unit 27.

In this embodiment, the X first and second drive / detection wirings 29 and 30 are made of aluminum (Al). X The first and second drive / detection wirings 29 and 30 are electrically connected to the individual electrode portions 27 via contact plugs 31 and 51 penetrating the first and second insulating films 33 and 34. .
The X first and X second drive / detection wires 29 and 30 are routed on the support portion 14 via the beam portion 25 of the X movable electrode 22 and the base portion 23 of the X fixed electrode 21, and a part thereof Is exposed as a pad 13. The X first and X second drive / detection wirings 29 and 30 each have a beam portion 25 itself made of a part of the conductive semiconductor substrate 3 in a section passing through the beam portion 25 of the X movable electrode 22. It is used as a current path. Since no aluminum wiring is provided on the beam portion 25, the stretchability of the beam portion 25 can be maintained.

Further, an X third drive / detection wiring 32 for detecting a change in voltage accompanying a change in capacitance is routed from the electrode portion 24 of the X fixed electrode 21 to the support portion 14, and this X third drive As with the other wirings 29 and 30, a part of the / detecting wiring 32 is exposed as the pad 13.
In the semiconductor substrate 3, the upper surfaces and side surfaces of the X fixed electrode 21 and the X movable electrode 22 are covered with a protective thin film 35 made of silicon oxide (SiO ₂ ) together with the first insulating film 33 and the second insulating film 34.

  In addition, a third insulating film 36, a fourth insulating film 37, a fifth insulating film 38, and a surface protective film 39 are sequentially stacked on the second insulating film 34 in a portion outside the cavity 10 on the surface of the semiconductor substrate 3. Yes. That is, in this gyro sensor 1, the number of insulating films stacked on the sensor is smaller than the number of insulating films included in the integrated circuit 5, and in this embodiment, the insulating film of the sensor is the first. The insulating film 33 has a two-layer structure of a first insulating film 33 and a second insulating film 34, and the insulating film of the integrated circuit 5 has a six-layer structure of first to fifth insulating films 33, 34, 36 to 38 and a surface protective film 39.

  In the X-axis sensor 6 having the above structure, the same polarity / different polarity drive is provided between the X fixed electrode 21 and the X movable electrode 22 via the X first to X third drive / detection wires 29, 30, and 32. Voltage is applied alternately. As a result, a Coulomb repulsive force / Coulomb attractive force is alternately generated between the electrode portion 24 of the X fixed electrode 21 and the electrode portion 27 of the X movable electrode 22. As a result, the comb-shaped X movable electrode 22 vibrates left and right (vibrates Ux) along the X-axis direction with respect to the comb-shaped X fixed electrode 21. In this state, when the X movable electrode 22 rotates around the Y axis as a central axis, a Coriolis force Fz is generated in the Z axis direction. Due to the Coriolis force Fz, the facing area between the electrode portion 24 of the X fixed electrode 21 and the electrode portion 27 of the X movable electrode 22 that are adjacent to each other changes. Then, the angular velocity ωy about the Y axis is detected by detecting the change in capacitance between the X movable electrode 22 and the X fixed electrode 21 due to the change in the facing area.

In this embodiment, the angular velocity ωy about the Y-axis is obtained by taking a difference between detection values of one and the other electrode portions of the X movable electrode 22 that is insulated and separated.
In the Y-axis sensor 7, drive voltages of the same polarity / different polarity are provided between the Y fixed electrode 41 and the Y movable electrode 42 via the Y first to Y third drive / detection wirings 49, 50, 52. Given alternately. Thereby, a Coulomb repulsive force / Coulomb attractive force is alternately generated between the electrode portion 44 of the Y fixed electrode 41 and the electrode portion 47 of the Y movable electrode 42. As a result, the comb-shaped Y movable electrode 42 vibrates left and right (vibrates Uy) along the Y-axis direction with respect to the comb-shaped Y fixed electrode 41. In this state, when the Y movable electrode 42 rotates around the Y axis, a Coriolis force Fx is generated in the X axis direction. Due to the Coriolis force Fx, the facing area between the electrode portion 44 of the Y fixed electrode 41 and the electrode portion 47 of the Y movable electrode 42 that are adjacent to each other changes. Then, the angular velocity ωz around the Z axis is detected by detecting the change in capacitance between the Y movable electrode 42 and the Y fixed electrode 41 due to the change in the facing area.
<Configuration of Z-axis sensor>
Next, the configuration of the Z-axis sensor will be described with reference to FIGS. 2 and 5 to 7.

FIG. 5 is a plan view of the main part of the Z-axis sensor shown in FIG. 6 is a cross-sectional view of the main part of the Z-axis sensor shown in FIG. 2, and is a cross-sectional view taken along the cutting line VI-VI of FIG. 7 is a cross-sectional view of the main part of the Z-axis sensor shown in FIG. 2, and is a cross-sectional view taken along the cutting line VII-VII in FIG.
With reference to FIG. 2, the semiconductor substrate 3 made of conductive silicon has a cavity 10 inside as described above. The upper surface 11 (surface portion) of the semiconductor substrate 3 is supported by the support portion 14 so as to float with respect to the bottom wall 12 of the semiconductor substrate 3 so as to surround each of the X-axis sensor 6 and the Y-axis sensor 7. A Z-axis sensor 8 is disposed.

The Z-axis sensor 8 includes a Z-fixed electrode 61 as a first electrode fixed to a support portion 14 (straight line portion 16) provided in the cavity 10, and a Z-axis sensor 8 that is held so as to be able to vibrate with respect to the Z-fixed electrode 61. And a Z movable electrode 62 as two electrodes. The Z fixed electrode 61 and the Z movable electrode 62 are formed with the same thickness.
In the Z-axis sensor 8, the Z movable electrode 62 is disposed so as to surround the annular portion 17 of the support portion 14, and the Z fixed electrode 61 is disposed so as to further surround the Z movable electrode 62. The Z fixed electrode 61 and the Z movable electrode 62 are integrally connected to both side walls of the linear portion 16 of the support portion 14.

The Z fixed electrode 61 includes a base portion 63 as a first base portion having a square ring shape in plan view fixed to the support portion 14, and a linear portion of the base portion 63 with respect to the X axis sensor 6 (Y axis sensor 7). 16 includes a plurality of comb-like electrode portions 64 as first electrode portions provided on a portion on the opposite side to 16.
On the other hand, the Z movable electrode 62 faces the base portion 65 as a second base portion having a square ring shape in plan view and between the base portion 65 and each of the comb-like electrode portions 64 of the Z fixed electrode 61 adjacent to each other. And an electrode portion 66 as a comb-like second electrode portion that meshes so as not to contact the electrode portion 64 of the Z fixed electrode 61. The base portion 65 of the Z movable electrode 62 has a linear main frame extending in parallel with each other, and the reinforcing frame is combined with the main frame so that a triangular space is repeated along the main frame. It has a truss-like frame structure. The base portion 65 of the Z movable electrode 62 having such a structure has a section in which the reinforcing frame is omitted in a portion opposite to the side where the electrode section 66 is disposed, and the main frame of the section is the Z frame. It functions as a beam portion 67 for enabling the movable electrode 62 to move up and down.

In other words, in the Z-axis sensor 8, the beam portion 67 is distorted, and the base portion 65 of the Z movable electrode 62 is moved toward and away from the cavity 10 with the beam portion 67 as a fulcrum as if it were a pendulum. By rotating (vibrating Uz), the electrode portion 66 of the Z movable electrode 62 meshed with the electrode portion 64 of the Z fixed electrode 61 in a comb shape vibrates up and down.
The base portion 63 of the Z fixed electrode 61 has a linear main frame extending in parallel with each other, and a reinforcing frame is combined with the main frame so that a triangular space is repeated along the main frame. It has a truss-like frame structure.

  The individual electrode portions 64 of the Z fixed electrode 61 have base ends connected to the base portion 63 of the Z fixed electrode 61, distal ends extending toward the Z movable electrode 62, and equal intervals along the inner wall of the base portion. They are arranged in a comb shape. In addition, an insulating layer 68 (silicon oxide in this embodiment) is embedded from the surface to the cavity 10 so as to cross the electrode portion 64 in the width direction in a portion near the base end portion of each electrode portion 64. It is. With this insulating layer 68, the individual electrode portions 64 of the Z fixed electrode 61 are insulated from the other portions of the Z fixed electrode 61.

  In addition, on the both sides of the portion (opposing portion 84) of the base portion 63 of the Z fixed electrode 61 facing the tip portion 70 (described later) of the electrode portion 66 of the Z movable electrode 62, the main frame of the truss structure is arranged in the width direction. An insulating layer 69 as a first isolation insulating layer is embedded from the surface of the semiconductor substrate 3 to the cavity 10 so as to cross. As a result, the facing portion 84 surrounded by the insulating layer 69 and the triangular space of the truss structure is insulated from other portions of the base portion 63 of the Z fixed electrode 61.

  On the other hand, each electrode portion 66 of the Z movable electrode 62 has a base end portion 71 connected to the base portion 65 of the Z movable electrode 62 and a distal end portion 70 extending between the electrode portions 64 of the Z fixed electrode 61. The Z fixed electrodes 61 are arranged in a comb-teeth shape so as not to contact the electrode portion 64. Further, a portion of the Z movable electrode 62 near the tip 70 is provided as a second isolation insulating layer from the surface of the semiconductor substrate 3 to the cavity 10 so as to cross the electrode 66 in the width direction. Insulating layer 73 (in this embodiment, silicon oxide) is embedded. In addition, in the portion of the Z movable electrode 62 near the base end portion 71 of the individual electrode portion 66, the insulating layer 74 (this layer) extends from the surface of the semiconductor substrate 3 to the cavity 10 so as to cross the electrode portion 66 in the width direction. In the embodiment, silicon oxide) is embedded. By these insulating layers 73 and 74, each electrode portion 66 is divided into three portions (a distal end portion 70, a proximal end portion 71, and an intermediate portion between the distal end portion 70 and the proximal end portion 71). Part 72).

Further, the individual electrode portions 66 of the Z movable electrode 62 are warped in an arc shape in cross section in a direction away from the cavity 10 of the semiconductor substrate 3 so as to protrude from the surface of the electrode portion 64 of the Z fixed electrode 61. A portion 81 projecting upward from the surface of the substrate.
As described above, the first insulating film 33 and the second insulating film 34 made of silicon oxide (SiO ₂ ) are sequentially stacked on the surface of the semiconductor substrate 3 including the Z fixed electrode 61 and the Z movable electrode 62. The first insulating film 33 is thicker than the other parts on the surface of the Z movable electrode 62. Thereby, a relatively large stress can be applied to the Z movable electrode 62, and the electrode portion 66 of the Z movable electrode 62 can be warped. A Z first detection wiring 75, a Z first drive wiring 76, a Z second detection wiring 77, and a Z second drive wiring 78 are formed on the second insulating film 34.

  The Z first detection wiring 75 and the Z second detection wiring 77 are respectively connected to the electrode portion 64 of the Z fixed electrode 61 and the intermediate portion 72 of the Z movable electrode 62 which are adjacent to each other. That is, in the Z-axis sensor 8, the electrode portion 64 of the Z fixed electrode 61 and the intermediate portion 72 of the Z movable electrode 62, to which the Z first detection wiring 75 and the Z second detection wiring 77 are connected, are connected to each other. The electrodes of the capacitive element (detection unit) are opposed to each other with a distance d, a constant voltage is applied between them, and the capacitance changes according to the change of the distance d.

  Specifically, the Z first detection wiring 75 is formed along the base portion 63 of the Z fixed electrode 61, and straddles the insulating layer 68 of each electrode portion 64 of the Z fixed electrode 61. It contains aluminum wiring that branches off. The branched aluminum wiring is electrically connected to the front end side of the insulating layer 68 in each electrode part 64 through a contact plug 79 penetrating the first insulating film 33 and the second insulating film 34. . In addition, as shown in FIG. 2, the Z first detection wiring 75 is routed on the support portion 14 via the base portion 63 of the Z fixed electrode 61, and a part thereof is exposed as the pad 13.

  On the other hand, the Z second detection wiring 77 detects a change in voltage accompanying a change in capacitance from the electrode portion 66 of the Z movable electrode 62. The Z second detection wiring 77 is formed along the base portion 65 of the Z movable electrode 62 and extends to the intermediate portion 72 across the insulating layer 74 near the base end portion 71 of each electrode portion 66 of the Z movable electrode 62. It contains aluminum wiring that branches off. The branched aluminum wiring is electrically connected to the intermediate part 72 of each electrode part 66 through a contact plug 80 penetrating the first insulating film 33 and the second insulating film 34. As shown in FIG. 2, the Z second detection wiring 77 is routed on the support portion 14 via the base portion 65 of the Z movable electrode 62, and a part thereof is exposed as the pad 13.

  Further, the Z first drive wiring 76 and the Z second drive wiring 78 are a facing portion 84 (first contact portion) of the Z fixed electrode 61 and a Z movable electrode facing each other in a direction orthogonal to the facing direction of the electrodes constituting the capacitive element. 62 are respectively connected to the distal end portion 70 (second contact portion). That is, in this Z-axis sensor 8, a driving voltage is applied between the opposed portion 84 of the Z fixed electrode 61 and the distal end portion 70 of the Z movable electrode 62, and the coulomb generated by the voltage change of the driving voltage. The drive part which vibrates Z movable electrode 62 with force is comprised.

  Specifically, the Z first drive wiring 76 supplies a drive voltage to the facing portion 84 of the Z fixed electrode 61. The Z first drive wiring 76 spans both sides of the insulating layer 69 using the surface of the second insulating film 34 and faces the opposing portion 84 via a contact plug 85 penetrating the first insulating film 33 and the second insulating film 34. And the aluminum wiring electrically connected to the portion excluding the facing portion 84 of the base portion 63, and the remaining portion is configured using the base portion 63 of the Z fixed electrode 61 made of conductive silicon. Yes. Further, as shown in FIG. 2, the Z first drive wiring 76 is routed on the support portion 14, and a part thereof is exposed as the pad 13.

  On the other hand, the Z second drive wiring 78 supplies a drive voltage to the distal end portion 70 of the Z movable electrode 62. The Z second drive wiring 78 extends between the distal end portion 70 and the proximal end portion 71 of the electrode portion 66 using the surface of the second insulating film 34 and penetrates the first insulating film 33 and the second insulating film 34. An aluminum wiring electrically connected to the distal end portion 70 and the proximal end portion 71 through a contact plug 86, and the remaining portion uses the base portion 65 of the Z movable electrode 62 made of conductive silicon. Configured. Further, as shown in FIG. 2, the Z second drive wiring 78 is routed on the support portion 14 and a part thereof is exposed as the pad 13.

In the semiconductor substrate 3, the upper surfaces and side surfaces of the Z fixed electrode 61 and the Z movable electrode 62 are covered with a protective thin film 35 made of silicon oxide (SiO ₂ ) together with the first insulating film 33 and the second insulating film 34.
In addition, a third insulating film 36, a fourth insulating film 37, a fifth insulating film 38, and a surface protective film 39 are sequentially stacked on the second insulating film 34 in a portion outside the cavity 10 on the surface of the semiconductor substrate 3. Yes. In the portion, the opening 82 exposing the Z first detection wiring 75, the Z first drive wiring 76, the Z second detection wiring 77, and the Z second drive wiring 78 as the pad 13 is provided on the surface. The protective film 39 is formed through the fifth, fourth and third insulating films 36.

  In the Z-axis sensor 8, the same polarity / position is provided between the facing portion 84 of the Z fixed electrode 61 and the tip portion 70 of the Z movable electrode 62 via the Z first drive wiring 76 and the Z second drive wiring 78. Different polarity driving voltages are applied alternately. Thereby, a Coulomb repulsive force / Coulomb attractive force is alternately generated between the facing portion 84 of the Z fixed electrode 61 and the tip portion 70 of the Z movable electrode 62. As a result, as if the comb-shaped Z movable electrode 62 is a pendulum, the comb-shaped Z fixed electrode 61 is also vertically moved along the Z-axis direction with respect to the Z fixed electrode 61 with the vibration center as the center. It vibrates (vibrates Uz). In this state, when the Z movable electrode 62 rotates around the X axis, a Coriolis force Fy is generated in the Y axis direction. Due to the Coriolis force Fy, the facing area S between the electrode portion 64 of the Z fixed electrode 61 and the intermediate portion 72 of the electrode portion 66 of the Z movable electrode 62 that are adjacent to each other changes. Then, the change in the capacitance C between the Z movable electrode 62 and the Z fixed electrode 61 due to the change in the interelectrode distance d is detected via the Z first detection wiring 75 and the Z second detection wiring 77. Thus, the angular velocity ωx around the X axis is detected. In this embodiment, the angular velocity ωx around the X axis is obtained by taking the difference between the detection value of the Z axis sensor 8 surrounding the X axis sensor 6 and the detection value of the Z axis sensor 8 surrounding the Y axis sensor 7. Desired.

  The difference is obtained, for example, by reversing the positional relationship between the fixed electrode and the movable electrode of the Z-axis sensor 8 surrounding the X-axis sensor 6 and the fixed electrode and the movable electrode of the Z-axis sensor 8 surrounding the Y-axis sensor 7. be able to. That is, in one Z-axis sensor 8, as described above, the Z movable electrode 62 is disposed so as to surround the annular portion 17 of the support portion 14, and the Z fixed electrode 61 is disposed so as to further surround the Z movable electrode 62. Deploy. On the other hand, in the other Z-axis sensor 8, a Z fixed electrode is disposed so as to surround the annular portion 17 of the support portion 14, and a Z movable electrode is disposed so as to further surround the Z fixed electrode. Thereby, between the pair of Z-axis sensors 8, the Z movable electrode 62 and the other Z movable electrode are shaken differently, so that a difference is generated.

Even when the positional relationship between the fixed electrode and the movable electrode of the one and the other Z-axis sensors 8 is the same, a difference can be obtained by reversing the warping direction of the movable electrode. That is, in one and the other Z-axis sensor 8, as described above, the Z movable electrode is disposed so as to surround the annular portion 17 of the support portion 14, and the Z fixed electrode is disposed so as to further surround the Z movable electrode. Then, the warp direction of the other Z movable electrode is not the direction away from the cavity 10 but the direction toward the back surface of the semiconductor substrate 3 so that the Z movable electrode protrudes from the back surface of the Z fixed electrode. As a result, a capacitance difference is generated between the pair of Z-axis sensors 8 when the Z movable electrode vibrates, and thus a difference is generated.
<Configuration of integrated circuit>
Next, the configuration of the integrated circuit will be described with reference to FIG. FIG. 8 is a schematic cross-sectional view of the integrated circuit shown in FIG. 8 is different in scale from the above-described other cross-sectional views (FIGS. 4, 6, and 7), and therefore the size of the expression is different even in the portion to which the same reference numerals are assigned. .

As described above, the integrated circuit 5 is formed on the semiconductor substrate 3 on which the X-axis sensor 6, the Y-axis sensor 7, and the Z-axis sensor 8 are formed so as to surround them.
The integrated circuit 5 is composed of a CMOS device, and includes an N channel MOSFET 91 and a P channel MOSFET 92 formed on the semiconductor substrate 3.
The NMOS region 93 in which the N-channel MOSFET 91 is formed and the PMOS region 94 in which the P-channel MOSFET 92 is formed are insulated and isolated from each other by the element isolation unit 95.

The element isolation portion 95 forms a trench (shallow trench 96) dug relatively shallow from the surface of the semiconductor substrate 3, forms a thermal oxide film 97 on the inner surface of the shallow trench 96 by a thermal oxidation method, and then performs CVD. An insulator 98 (for example, silicon oxide (SiO ₂ )) is deposited in the shallow trench 96 by the (Chemical Vapor Deposition) method.

  In the NMOS region 93, a P-type well 99 is formed. The depth of the P-type well 99 is larger than the depth of the shallow trench 96. In the surface layer portion of the P-type well 99, an N-type source region 101 and a drain region 102 are formed with the channel region 100 interposed therebetween. The end portions of the source region 101 and the drain region 102 on the channel region 100 side have a small depth and impurity concentration. That is, in the N-channel MOSFET 91, an LDD (Lightly Doped Drain) structure is applied.

A gate insulating film 103 is provided on the channel region 100. The gate insulating film 103 is formed in the same layer as the first insulating film 33 (that is, in contact with the surface of the semiconductor substrate 3).
A gate electrode 104 is provided on the gate insulating film 103. The gate electrode 104 is made of N-type polycrystalline silicon (Poly-Si).

A sidewall 105 is formed around the gate insulating film 103 and the gate electrode 104. The sidewall 105 is made of silicon nitride (SiN).
Silicides 106 to 108 are formed on the surfaces of the source region 101, the drain region 102, and the gate electrode 104, respectively.
An N-type well 109 is formed in the PMOS region 94. The depth of the N-type well 109 is larger than the depth of the shallow trench 96. In the surface layer portion of the N-type well 109, a P-type source region 111 and a drain region 112 are formed with a channel region 110 interposed therebetween. The depth and impurity concentration of the end portions of the source region 111 and the drain region 112 on the channel region 110 side are reduced. That is, the LD channel structure is applied to the P-channel MOSFET 92.

A gate insulating film 113 is formed on the channel region 110. The gate insulating film 113 is made of silicon oxide.
A gate electrode 114 is formed on the gate insulating film 113. Gate electrode 114 is made of P-type polycrystalline silicon.
A sidewall 115 is formed around the gate insulating film 113 and the gate electrode 114. The sidewall 115 is made of SiN.

Silicides 116 to 118 are formed on the surfaces of the source region 111, the drain region 112, and the gate electrode 114, respectively.
On the semiconductor substrate 3, second to fifth insulating films 34, 36 to 38 and a surface protective film 39 are sequentially stacked. These insulating films are the same as the second to fifth insulating films 34, 36 to 38 and the surface protective film 39 shown in FIGS. 4, 6 and 7.

Drain wirings 119 and 120 and source wirings 121 and 122 are formed on the lowermost second insulating film 34. These wires are made of aluminum (Al), and are the same as the wires (X first drive / detection wire 29, Z first detection wire 75, etc.) of the X-axis sensor 6, the Y-axis sensor 7, and the Z-axis sensor 8 described above. It is formed in one layer.
The source lines 121 and 122 are formed above the source region 101 and the source region 111, respectively. Between the source wiring 121 and the source region 101 and between the source wiring 122 and the source region 111, contact plugs 123 and 124 for electrically connecting them penetrate through the second insulating film 34. Is provided.

The drain wirings 119 and 120 are formed above the drain region 102 and the drain region 112, respectively. Between the drain wiring 119 and the drain region 102 and between the drain wiring 120 and the drain region 112, contact plugs 125 and 126 for electrically connecting them penetrate through the second insulating film 34. Is provided.
Similarly, wirings 127 are formed on the third to fifth insulating films 36 to 38, respectively, and the wirings 127 of the insulating films of the respective layers are electrically connected to each other through contact plugs 128. . In the uppermost fifth insulating film 38, the drain wiring 129 is formed across the drain region 102 and the drain region 112, and the drain wiring 129 includes the drain wiring 119 of the N-channel MOSFET 91 and the drain of the P-channel MOSFET 92. The wiring 120 is connected to both. The contact plugs 123 to 126, 128 are made of tungsten (W).

The surface protective film 39 is formed with an opening 130 that exposes a part of the drain wiring 129 formed on the uppermost fifth insulating film 38 as a pad. The drain wiring 129 exposed as a pad is electrically connected to the electrode pad 9 by, for example, a bonding wire (not shown) while being packaged by the resin package 2.
<Method for Manufacturing Gyro Sensor 1>
Next, with reference to FIG. 9A to FIG. 36A, FIG. 9B to FIG. 36B, and FIG. 9C to FIG.

  FIG. 9A to FIG. 36A are schematic cross-sectional views showing the manufacturing process of the gyro sensor according to one embodiment of the present invention in the order of steps, and show a cut surface at the same position as FIG. FIG. 9B to FIG. 36B are schematic cross-sectional views showing the manufacturing process of the gyro sensor according to one embodiment of the present invention in the order of steps, and show a cut surface at the same position as FIG. 9C to 36C are schematic cross-sectional views showing the manufacturing process of the gyro sensor according to one embodiment of the present invention in the order of steps, and show a cut surface at the same position as FIG.

  In order to manufacture the gyro sensor 1, first, as shown in FIGS. 9A to 9C, the surface of the semiconductor substrate 3 made of conductive silicon is thermally oxidized (for example, temperature 1100 to 1200 ° C., film thickness 5000 mm). . Thereby, the first insulating film 33 is formed on the surface of the semiconductor substrate 3. At that time, the oxidation time of the region where the Z movable electrode 62 is to be formed is made longer than the oxidation time of other portions, and the thickness of the region is increased.

Next, as shown in FIGS. 10A and 10B, the first insulating film 33 is patterned by a known patterning technique, and the insulating layers 28, 68, 69, 73 and 74 are embedded in the X-axis sensor 6 and the Z-axis sensor 8. An opening 18 is formed in the power region. Next, the semiconductor substrate 3 is dug down by anisotropic deep RIE (reactive ion etching) using the first insulating film 33 as a hard mask, specifically, by a Bosch process. As a result, a trench 19 is formed in the semiconductor substrate 3. In the Bosch process, the process of etching the semiconductor substrate 3 using SF ₆ (sulfur hexafluoride) and the process of forming a protective film on the etched surface using C ₄ F ₈ (perfluorocyclobutane) are alternated. Repeated. Thereby, the semiconductor substrate 3 can be etched with a high aspect ratio, but wavy irregularities called scallops are formed on the etched surface (inner peripheral surface of the trench). At this time, as shown in FIG. 10C, the region where the integrated circuit 5 is to be formed is maintained as it is after the previous step.

  Next, as shown in FIGS. 11A and 11B, the inside of the trench 19 and the surface of the semiconductor substrate 3 are thermally oxidized (for example, temperature 1100 to 1200 ° C.), and then the surface of the oxide film is etched back (for example, etched) The film thickness after the back is 21800 mm). As a result, insulating layers 28, 68, 69, 73, and 74 that fill the trench 19 are formed. At this time, as shown in FIG. 11C, the region where the integrated circuit 5 is to be formed is maintained as it is after the previous step.

Next, as shown in FIGS. 12A to 23A and FIGS. 12B to 23B, the region where the sensor unit 4 is to be formed is divided into an N channel MOSFET 91 and a region where the integrated circuit 5 is to be formed by the steps shown in FIGS. 12C to 23C. Until the P-channel MOSFET 92 is formed, the state after the previous process is maintained (except for the time of etch back in FIG. 17C).
In the region where the integrated circuit 5 is to be formed, after the insulating layers 68, 69, 73, 74 are formed in the region where the sensor unit 4 is to be formed, the first insulating film is formed by CVD as shown in FIG. 12C. A silicon nitride film 20 is formed on 33.

  Next, as shown in FIG. 13C, the silicon nitride film 20 and the first insulating film 33 are patterned by a known patterning technique, and an opening 53 is formed in a region where the shallow trench 96 is to be formed. Next, the semiconductor substrate 3 is dug down by dry etching using the silicon nitride film 20 and the first insulating film 33 as hard masks. Thereby, a shallow trench 96 is formed in the semiconductor substrate 3. Next, the inner surface of the shallow trench 96 is oxidized by thermal oxidation with the silicon nitride film 20 and the first insulating film 33 left. As a result, a thermal oxide film 97 is formed on the inner surface of the shallow trench 96.

Next, as shown in FIG. 14C, silicon oxide (SiO ₂ ) is deposited on the semiconductor substrate 3 by the CVD method, and then etched back. As a result, an insulator 98 that fills the shallow trench 96 is formed. After the formation of the insulator 98, the silicon nitride film 20 is removed.
Next, as shown in FIG. 15C, a resist 54 having an opening that selectively exposes the PMOS region 94 is formed, and N-type impurities (for example, phosphorus (P) ions) are implanted (in) using the resist 54 as a mask. Plantation).

Next, as shown in FIG. 16C, a resist 55 having an opening for selectively exposing the NMOS region 93 is formed, and P-type impurities (for example, boron (B) ions) are implanted (in) using the resist 55 as a mask. Plantation).
Thereafter, the semiconductor substrate 3 is heat-treated to activate the implanted ions, and the N-type well 109 and the P-type well 99 are formed in the semiconductor substrate 3.

Next, as shown in FIG. 17C, the first insulating film 33 is thinned by etch back, and the gate insulating films 103 and 113 are formed.
Next, as shown in FIG. 18C, a polycrystalline silicon layer 56 is formed on the gate insulating films 103 and 113 by the CVD method.
Next, as shown in FIG. 19C, a resist 57 having an opening is formed in a region other than the region where the gate electrodes 104 and 114 are to be formed, and the polycrystalline silicon layer 56 is etched using the resist 57 as a mask. Thereby, the gate electrodes 104 and 114 are formed. After the formation of the gate electrodes 104 and 114, the resist 57 is removed. Next, N-type impurities are implanted into the gate electrode 104 and P-type impurities are implanted into the gate electrode 114 by a known ion implantation technique. At this time, impurity ions are implanted into the surface layer portions of the NMOS region 93 and the PMOS region 94 at a low concentration.

After ion implantation into the gate electrodes 104 and 114, a silicon nitride film 58 is formed on the semiconductor substrate 3 by CVD, as shown in FIG. 20C.
Next, as shown in FIG. 21C, the silicon nitride film 58 is etched back, whereby the sidewalls 105 and 115 are formed simultaneously.
Next, as shown in FIG. 22C, a resist (not shown) having an opening for selectively exposing the NMOS region 93 is formed on the semiconductor substrate 3, and N is formed on the semiconductor substrate 3 through the opening of the resist. Type impurities are implanted. As a result, an N-type source region 101 and drain region 102 are formed. Further, a resist (not shown) having an opening for selectively exposing the PMOS region 94 is formed on the semiconductor substrate 3, and a P-type impurity is implanted into the semiconductor substrate 3 through the opening of the resist. As a result, a P-type source region 111 and drain region 112 are formed.

Next, as shown in FIG. 23C, the surface layers of the source regions 101 and 111, the drain regions 102 and 112, and the gate electrodes 104 and 114 are silicided to form silicides 106 to 108 and 116 to 118.
Next, as shown in FIGS. 24A to 24C, the second insulating film 34 made of silicon oxide is stacked on the semiconductor substrate 3 by the CVD method.

  Next, as shown in FIGS. 25A to 25C, there are openings in regions where the contact plugs 31, 51, 79, 80, 85, 86 of the sensor unit 4 and the contact plugs 123-126, 128 of the integrated circuit 5 are to be formed. A resist (not shown) is formed, and the second insulating film 34 and the first insulating film 33 are continuously etched through the opening of the resist. Thereby, a contact hole for burying the contact plug is formed at the same time.

  Next, as shown in FIGS. 26A to 26C, a tungsten film that fills the contact hole is deposited by CVD, and the deposited tungsten film is polished by CMP. As a result, contact plugs 31, 51, 79, 80, 85, 86 of the sensor unit 4 and contact plugs 123-126, 128 of the integrated circuit 5 are simultaneously formed of tungsten.

  Next, as shown in FIGS. 27A to 27C, aluminum is deposited (for example, 7000 mm) on the second insulating film 34 by sputtering, and the aluminum deposited layer is patterned. As a result, on the second insulating film 34, the wiring of the sensor unit 4 (X first drive / detection wiring 29, Z first detection wiring 75, etc.) and the wiring of the integrated circuit 5 (drain wirings 119, 120, source wiring 121). , 122) are formed simultaneously.

Next, as shown in FIGS. 28A to 28C, the third insulating film 36 is laminated on the second insulating film 34 by the CVD method.
Thereafter, as shown in FIGS. 29A to 29C, the deposition of the insulating film by CVD, the formation of the contact plug, and the formation of the aluminum wiring are sequentially repeated, and the fourth insulating film 37 and the fifth insulating film 38 are respectively formed. A multilayer wiring structure in which the wiring 127 is formed is formed. After the formation of the multilayer wiring structure, a surface protective film 39 is formed.

  Next, as shown in FIGS. 30A and 30B, the third to fifth insulating films 36 to 38 and the surface protective film 39 on the region where the cavity 10 of the semiconductor substrate 3 is to be formed are removed by etching. At the same time, an opening 82 for exposing the wiring (X first drive / detection wiring 29, Z first detection wiring 75, etc.) of the sensor unit 4 as the pad 13 and the uppermost drain wiring 129 in the integrated circuit 5 are padded. An opening 130 is formed as shown in FIG. 30C. Thereby, an integrated circuit 5 made of CMOS is obtained. Therefore, as shown in FIGS. 31C to 36C, the cavity 10 is formed in the region where the integrated circuit 5 is to be formed in the region where the sensor unit 4 is to be formed by the steps shown in FIGS. 31A to 36A and 31B to 36B. Thus, until the X-axis sensor 6, the Y-axis sensor 7, and the Z-axis sensor 8 are formed, the state where the integrated circuit 5 is manufactured is maintained.

  In the region where the sensor unit 4 is to be formed, after the third to fifth insulating films 36 to 38 and the surface protective film 39 in the region where the cavity 10 is to be formed are removed, the semiconductor substrate according to one embodiment of the present invention. By the etching method, the region where the X fixed electrode 21, the Y fixed electrode 41 and the Z fixed electrode 61, the X movable electrode 22, the Y movable electrode 42 and the Z movable electrode 62 are to be formed in the semiconductor substrate 3 is partitioned. The etching region 87 as the first etching region and the second etching region is etched.

  This etching region 87 includes a plurality of portions partitioned independently (for example, a region 871 that partitions the beam portion 25 of the X movable electrode 22, a comb formed by meshing the X fixed electrode 21 and the X movable electrode 22). A region 872 where the teeth are divided and the gap between the comb teeth is to be formed, a comb tooth formed by the Z fixed electrode 61 and the Z movable electrode 62 meshing with each other, and a region 873 where the gap between the comb teeth is to be formed For example, a region 874 to form a triangular space defining the truss structure of the Z fixed electrode 61).

  Specifically, FIG. 31A, FIG. 31B, FIG. 37 (the cut surface along the cutting line AA in FIG. 37 is FIG. 31A) and FIG. 38 (the cut surface along the cutting line BB in FIG. 38). As shown in FIG. 31B, a resist 59 is formed on the semiconductor substrate 3. The resist 59 has a large number of openings 88 of the same pattern (in this embodiment, circular patterns in plan view having the same shape and size) that face each other for each of the plurality of independent etching regions 87.

The aperture ratio of the unit area (1 mm ² ) of the resist 59 is, for example, 1 to 20%. The distance D between the centers of the adjacent openings 88 is, for example, 3 μm to 30 μm. In FIG. 37 and FIG. 38, the openings 88 are shown to be large for ease of illustration, but in reality, the openings 88 are sized such as the X fixed electrode 21 and the Z fixed electrode 61. It is very small compared.

  Next, the semiconductor substrate 3 is dug down by anisotropic deep RIE using the resist 59 as a mask, specifically by a Bosch process. In the deep digging RIE, the etching depth is the same as the thickness of the X fixed electrode 21, the Y fixed electrode 41 and the Z fixed electrode 61, and the X movable electrode 22, the Y movable electrode 42 and the Z movable electrode 62 to be formed. Can continue. As a result, a large number of cylindrical recesses 89 as first recesses having substantially the same depth are formed on the surface portion of the semiconductor substrate 3. At the same time, planar outlines of the X fixed electrode 21, the Y fixed electrode 41 and the Z fixed electrode 61, and the X movable electrode 22, the Y movable electrode 42 and the Z movable electrode 62 are formed in the etching region 87. After deep digging RIE, the resist 59 is peeled off.

  Next, as shown in FIGS. 32A and 32B, an etching solution (for example, hydrofluoric acid) is supplied into the recess 89. As a result, the side walls 90 of the semiconductor substrate 3 that define a large number of recesses 89 are removed by etching in the lateral direction parallel to the surface of the semiconductor substrate 3. Thus, the surface portion of the semiconductor substrate 3 is formed into the shapes of the X fixed electrode 21, the Y fixed electrode 41, and the Z fixed electrode 61, and the X movable electrode 22, the Y movable electrode 42, and the Z movable electrode 62. A trench 60 as a second recess is formed therebetween.

Note that the etching solution supplied to the recess 89 also comes into contact with the portions of the semiconductor substrate 3 that become the respective electrodes (X fixed electrode 21, Z fixed electrode 61, etc.), but compared with the thickness of the portion. The width of the side wall 90 that defines the recess 89 is very small. For example, as shown in FIG. 31B, the width W ₂ (W ₁ / W ₂ ) of the side wall 90 with respect to the width W ₁ along the surface of the semiconductor substrate 3 at the portion that becomes the Z fixed electrode 61 is 10 to 100. Therefore, it is possible to maintain the shape of the portion to be each electrode (X fixed electrode 21, Z fixed electrode 61, etc.) as designed. The trench 60 is formed by integrating a large number of cylindrical recesses 89, and the bottom wall of the trench 60 is maintained as the bottom wall of the recesses 89. Therefore, the trench 60 is not flat and actually has undulations. It may be uneven.

Next, as shown in FIGS. 33A and 33B, the X fixed electrode 21, the Y fixed electrode 41 and the Z fixed electrode 61, the X movable electrode 22, the Y movable electrode 42 and the Z movable electrode 62 are formed by thermal oxidation or PECVD. A protective thin film 35 made of silicon oxide (SiO ₂ ) is formed on the entire surface of the substrate and the entire inner surface of the trench 60 (that is, the side surface and the bottom surface defining the trench 60).

Next, as shown in FIGS. 34A and 34B, the portion of the protective thin film 35 on the bottom surface of the trench 60 is removed by etch back. As a result, the bottom surface of the trench 60 is exposed.
Next, as shown in FIGS. 35A and 35B, the bottom surface of the trench 60 is further dug down by anisotropic deep RIE using the surface protective film 39 as a mask. As a result, an exposed space 83 in which the crystal plane of the semiconductor substrate 3 is exposed is formed at the bottom of the trench 60.

  Subsequent to this anisotropic deep RIE, as shown in FIGS. 36A and 36B, reactive ions and etching gas are supplied to the exposed space 83 of the trench 60 by isotropic RIE. The semiconductor substrate 3 is etched in the direction parallel to the surface of the semiconductor substrate 3 while being etched in the thickness direction of the semiconductor substrate 3 starting from each exposed space 83 by the action of the reactive ions and the like. Thereby, all the exposed spaces 83 adjacent to each other are integrated to form the cavity 10 inside the semiconductor substrate 3, and in the cavity 10, the X fixed electrode 21, the Y fixed electrode 41 and the Z fixed electrode 61, In addition, the X movable electrode 22, the Y movable electrode 42, and the Z movable electrode 62 are in a floating state.

  In forming the cavity 10, the method shown in FIG. 31A, FIG. 31B, FIG. 37 and FIG. 38 is applied. First, a large number of recesses having openings of the same pattern are formed by deep RIE. Subsequently, the exposed space 83 may be formed by removing the sidewalls of the recesses by isotropic etching, and then the exposed space 83 may be integrated. However, the depth position of the bottom wall 12 of the semiconductor substrate 3 that divides the cavity 10 from the bottom surface side does not have a particularly bad influence on the operation of the gyro sensor 1 and therefore may not be applied.

Through the above steps, the gyro sensor 1 shown in FIG. 1 is obtained.
<Effect>
As described above, according to the manufacturing method of the gyro sensor 1 described above, the X fixed electrode 21, the Y fixed electrode 41, the Z fixed electrode 61, the X movable electrode 22, the Y movable electrode 42, and In order to define the Z movable electrode 62, an etching region 87 (for example, a region including regions 871 to 874) for selectively etching the semiconductor substrate 3 is set.

  Prior to the formation of the trench 60 for defining these electrodes, as a first step, as shown in FIGS. 31A, 31B, 37 and 38, the semiconductor substrate 3 is formed in the same pattern (this embodiment). Then, anisotropic deep digging reactive ion etching is performed using as a mask a resist 59 having a large number of openings 88 of the same shape and size (circular pattern in plan view). That is, the semiconductor in the etching region 87 is deep reactive ion etching with the same pattern. Thereby, a large number of recesses 89 having substantially the same depth can be formed on the surface portion of the semiconductor substrate 3.

  Thereafter, as a second step, as shown in FIGS. 32A and 32B, the side walls 90 of the semiconductor substrate 3 that define a large number of recesses 89 are etched and removed in the lateral direction parallel to the surface of the semiconductor substrate 3. In this way, a large number of recesses 89 are integrated, whereby a trench 60 occupying the etching region 87 is formed. As a result, the etching region 87 of the semiconductor substrate 3 can be selectively etched, and the X fixed electrode 21, the Y fixed electrode 41, the Z fixed electrode 61, the X movable electrode 22, the Y movable electrode 42, and the Z movable electrode 62 can be etched. The trench 60 can be formed between them while being formed into a shape.

  As described above, as a first step, the trench 60 is formed as designed by forming the recesses 89 having substantially the same depth by performing deep reactive ion etching of the semiconductor substrate 3 in a pattern having a uniform shape and size. Can be formed at a depth of Therefore, even if the shape and size of the etched region are completely different, such as a very intricate region such as the etching regions 872 and 873 and a simple region such as the etching region 874, it is accurate. The trench 60 having a controlled depth can be formed. Therefore, the X fixed electrode 21, the Y fixed electrode 41, the Z fixed electrode 61, the X movable electrode 22, the Y movable electrode 42, and the Z movable electrode 62, which are defined by the trench 60, have a thickness as designed (semiconductor substrate). 3 in the thickness direction). As a result, the opposing area between the electrode part 24 of the X fixed electrode 21 and the electrode part 27 of the X movable electrode 22, the opposing area between the electrode part 44 of the Y fixed electrode 41 and the electrode part 47 of the Y movable electrode 42, and Z fixation Since the facing area S between the electrode part 64 of the electrode 61 and the intermediate part 72 of the Z movable electrode 62 can be made as designed, the angular velocity of the gyro sensor 1 can be detected well.

Further, even when the etching region 87 including a plurality of etching regions such as the regions 871, 872, 873, and 874 is selectively etched, the depth of the trench 60 can be accurately controlled, so that it is formed in the etching region 87. All the trenches 60 can be made to have substantially the same depth.
Also, as shown in FIGS. 37 and 38, in the first step of deep RIE, etching is performed with the same pattern from any location on the semiconductor substrate 3 (circular in plan view in this embodiment). Therefore, only one mask is required for patterning the resist 59 formed on the semiconductor substrate 3. Therefore, the manufacturing cost can be reduced. Furthermore, since the resist 59 is patterned once, the manufacturing time can be shortened.

As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form.
For example, in the above-described embodiment, the capacitive gyro sensor is taken up as an example in which the etching method according to the embodiment of the present invention is adopted. However, the etching method is applied to each axis of the capacitive acceleration sensor. The present invention can also be applied when forming a fixed electrode and a movable electrode (X axis, Y axis, and Z axis). In addition, the present invention can be applied not only to the manufacture of electrodes for capacitance type gyro sensors and acceleration sensors, but also, for example, when forming a recess serving as a reference pressure chamber of a piezoresistive type pressure sensor in a semiconductor substrate, a gate trench of a trench gate type MOSFET. The present invention can be applied to all processes for forming a recess in a semiconductor substrate.

In the above-described embodiment, the pattern formed as the first step is a circular shape in plan view as shown in FIGS. 37 and 38. However, if the same pattern is used, an elliptical shape, a square shape, a rectangular shape, and a rhombus shape in plan view are used. , Triangles, trapezoids, etc.
In the above-described embodiment, the mode in which the sensor unit 4 and the integrated circuit 5 are mixedly mounted on the semiconductor substrate 3 has been described. However, the sensor unit 4 and the integrated circuit 5 may be formed on separate semiconductor substrates. Good.

  Further, the aluminum wiring (for example, the X first drive / detection wiring 29, the Z first detection wiring 75, etc.) of the sensor routed on the surface of the semiconductor substrate 3 forms a gate electrode of the integrated circuit 5. By manufacturing in the same process, it can be replaced with wiring made of polysilicon. In that case, unlike the gate electrode, impurities may not be implanted into the polysilicon wiring. This is because the polysilicon wiring is not a wiring for supplying a current to each part of the sensor but a wiring for applying a voltage, and the resistance may be relatively high.

  In addition, various design changes can be made within the scope of matters described in the claims.

DESCRIPTION OF SYMBOLS 1 Gyro sensor 3 Semiconductor substrate 11 Upper wall (surface part of a semiconductor substrate)
21 X fixed electrode 22 X movable electrode 41 Y fixed electrode 42 Y movable electrode 60 trench 61 Z fixed electrode 62 Z movable electrode 87 etching region 88 (resist) opening 89 recess 90 side wall 871 region 872 region 873 region 874 region

Claims (3)

A method of selectively etching an etching region of a semiconductor substrate in which an etching region is defined,
Forming a plurality of first recesses having openings of the same shape and size in the etching region by deep reactive ion etching in a predetermined pattern from a plurality of locations in the etching region; and
Forming a second recess in which the plurality of first recesses are integrated in the etching region by removing the side walls of the semiconductor substrate that define the plurality of first recesses by isotropic ion etching. A method for etching a semiconductor substrate. The etching region includes a first etching region and a second etching region having different shapes or sizes from each other;
2. The method of etching a semiconductor substrate according to claim 1, wherein the step of forming the first recess includes a step of simultaneously forming a plurality of the first recesses in the first etching region and the second etching region, respectively. . A semiconductor substrate;
A first electrode formed on a surface portion of the semiconductor substrate;
A method for manufacturing a capacitive MEMS sensor, comprising: a second electrode formed on the surface portion of the semiconductor substrate and facing the first electrode with a space therebetween;
Defining an etching region so as to partition a region where the first and second electrodes are to be formed outside the region where the first electrode and the second electrode are to be formed;
Forming a plurality of first recesses having openings of the same shape and size in the etching region by deep reactive ion etching in a predetermined pattern from a plurality of locations in the etching region; and
By removing the side walls of the semiconductor substrate that define the plurality of first recesses by isotropic ion etching, a second recess in which the plurality of first recesses are integrated is formed in the etching region, and at the same time, Forming a first and second electrode. A method of manufacturing a capacitive MEMS sensor.

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