JP3385759B2 - Semiconductor yaw rate sensor and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor yaw rate sensor suitable for vehicle body control, navigation, etc., and a method for manufacturing the same.

[0002]

2. Description of the Related Art A conventional yaw rate sensor for detecting a yaw rate or the like acting on a vehicle body of an automobile is disclosed in Japanese Patent Laid-Open No.
A vibration gyro as disclosed in Japanese Patent No. 223817 is known. In this vibrating gyro, a piezoelectric element is bonded to a specified surface of a metal square bar to form a vibrating body,
This is supported by a thin rod.

Further, Japanese Patent Application Laid-Open No. 4-142420 discloses an angular velocity sensor having a structure in which a piezoelectric element is bonded to a metal tuning fork. That is, in any of these devices that detect acceleration such as yaw rate, the piezoelectric element vibrates the main body, and the distortion caused by the Coriolis force generated by the yaw rate that is the measurement target is detected by the piezoelectric element. Trying to detect by the change of.

Here, the Coriolis force generated at the yaw rate is used as the detection principle.
Is expressed by the following equation. Fc = 2 mVω (1) m: mass V: velocity ω: angular velocity As can be seen from the equation (1), the Coriolis force Fc is the mass m.
When the angular velocity ω is generated when the object of is moving at the velocity V, it is perpendicular to the moving direction and the direction of the rotation axis of the angular velocity ω, and its magnitude is the mass m, the velocity V, and the angular velocity ω. Occurs in proportion. Therefore, if the Coriolis force can be measured, the angular velocity can be obtained.

By the way, the performance such as the detection sensitivity in this type of sensor mechanism depends on the supporting method and the processing accuracy, and a particularly high-performance sensor is expensive due to the difficulty in processing and assembling. Further, there is a problem that miniaturization of the sensor is not easy due to restrictions of processing and assembly.

On the other hand, the applicant of the present application has previously developed a new semiconductor yaw rate sensor that applies semiconductor technology and is small in size and can be manufactured at a low cost by utilizing a transistor type displacement detection mechanism. No. 5-311762 is proposed.

In this semiconductor yaw rate sensor, a weight portion is supported by a beam, a source electrode and a drain electrode are formed on a substrate portion facing the weight portion, and the weight portion is used as a gate electrode via an air gap. A transistor is formed, and an electrode for exciting the weight portion is formed on the weight portion and the substrate.

According to this structure, when a yaw rate is generated in the excited weight portion, the Coriolis force acts in the substrate direction to change the air gap, which changes the drain current of the transistor. The yaw rate can be detected by measuring.

The sensor having this structure can be manufactured by diverting the IC process, and has a feature that the size is reduced and the processing accuracy is dramatically improved. However, as a result of further studies, it was found that there are problems that accuracy is reduced due to the inability to detect differentially, erroneous detection occurs due to acceleration, and a circuit load for solving this is large. Further, in the method of forming a transistor, the method of setting the gate width using the diffusion of impurities has a problem that the diffusion width of the impurities is short, so that the gate width is small and a sufficient current value for detection cannot be secured.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and solves the deterioration of detection accuracy and erroneous detection of acceleration even if it is a transistor type, and is mounted on, for example, an automobile. It is an object of the present invention to provide a small-sized and high-performance semiconductor yaw rate sensor that can be effectively used for vehicle body control, navigation, etc., and a manufacturing method thereof.

[0011]

In order to achieve the above object, (1) a semiconductor yaw rate sensor according to the present invention comprises:
A semiconductor substrate and a semiconductor substrate, which are arranged above the semiconductor substrate with a predetermined space therebetween and are supported by a beam structure so as to be displaceable,
A movable electrode for excitation is integrally formed so as to project in parallel with the semiconductor substrate, and a weight that functions as a gate electrode of a transistor and a predetermined gap above the semiconductor substrate are provided with a gap between the movable electrode and the movable electrode. And a fixed electrode for excitation that vibrates the weight using electrostatic force, and is arranged horizontally with respect to the semiconductor substrate, and one end thereof
Overlap at a part of the circumference of the weight
And the two or more sets of source and drain electrodes are formed, comprises a lower electrode formed on at least the no source electrode and drain electrode regions of the weights opposed portions of said semiconductor substrate, said weight and a transistor with the source electrode and the drain electrode and the gate electrode by, the weight at a predetermined period by said excitation fixed electrode when excited in the semiconductor substrate and the horizontal direction, the said weight due to the action of the yaw rate Semiconductor substrate
And horizontal displacement is differentially detected by a change in current between the two or more sets of source and drain.

[0012] (2) or a semiconductor substrate, are arranged at a predetermined distance above said semiconductor substrate, is supported freely displaced by the beam structure, and a weight which serves as a gate electrode of the transistor, before Symbol semiconductor Placed horizontally with the board
And a part of the end part thereof faces a part of the periphery of the weight.
Two or more sets of source electrodes and drain electrodes formed to overlap with each other in a position, and at least a region of the semiconductor substrate facing the weight without the source electrode and the drain electrode. An exciting lower electrode for vibrating by utilizing the gate electrode, the source electrode and the drain electrode formed of the weight, and the exciting lower electrode forming the transistor at a predetermined cycle. When the vertical vibration is applied, the weight front
It is characterized in that the displacement in the horizontal direction with respect to the semiconductor substrate is differentially detected by the current change between the two or more sets of source and drain.

(3) In the semiconductor yaw rate sensor having a semiconductor structure, the yaw rate detecting section for detecting a yaw rate and the acceleration detecting section for detecting an acceleration are provided, and the acceleration detecting section detects the acceleration from the yaw rate detecting section. It is characterized in that the detected amount is canceled.

(4) Further, in the method for manufacturing a semiconductor yaw rate sensor according to the present invention, the first step of introducing impurities into the surface of the semiconductor substrate to form two or more sets of source and drain electrodes, and the semiconductor substrate A second step of forming a sacrificial layer on the main surface, and a third step of forming a beam-shaped weight and an excitation fixed electrode for the weight on the sacrificial layer,
One of the source electrode and the drain electrode is attached to the weight.
Shape the opening so that the end overlaps the weight.
By the fourth step of forming and the formation of the opening
A fifth step of etching away the exposed sacrificial layer ,
Ions in the semiconductor substrate are self-aligned with the openings.
Inject it into the area around the weight, and
And one end of the source and drain electrodes
Sixth step of setting the burlap region as the gate width
And the displacement of the weight in the horizontal direction with respect to the semiconductor substrate
Differential detection is performed by changing the current between the two or more sets of source and drain.
The sacrificial layer underneath the weight so that it can be exposed.
And a seventh step of removing the groove. The weight is vibrated by the electrostatic force from the excitation fixed electrode and is displaced by the Coriolis force generated by the yaw rate.

[0015]

According to the configuration of (1), the weight is vibrated in the horizontal direction with respect to the substrate by the electrostatic force generated by applying a voltage at a frequency between the fixed electrode for excitation and the weight, and the vibration is perpendicular to the substrate. When a yaw rate with the direction as the axis is applied, the weight is displaced in the horizontal direction with respect to the substrate due to the Coriolis force, and the gate width in the transistor configuration portion is changed. Here, since the two transistors are arranged so that the gate width is displaced in the opposite phase, the drain current is also changed in the opposite phase, and the differential detection becomes possible. The differential detection doubles the amount of change in current, enabling highly accurate detection. According to this configuration, the drain current changes even when acceleration is applied in the direction perpendicular to the substrate, but since the two transistors change in phase and in the same amount, differential detection does not result in erroneous detection. Further, even if the drain current changes due to the temperature characteristics of the transistor, the same amount changes in the same phase, so that differential detection does not result in erroneous detection.

Further, according to the configuration of (2), the weight is vibrated in the vertical direction with respect to the substrate by the electrostatic force generated by applying a voltage at a frequency between the lower electrode for excitation and the weight, and this is perpendicular to the vibration direction. When a yaw rate with a horizontal axis is applied to the substrate, the weight is displaced in the horizontal direction with respect to the substrate due to the Coriolis force, and the gate width in the transistor component changes. Here, since the two transistors are arranged so that the gate width is displaced in the opposite phase, the drain current is also changed in the opposite phase, and the differential detection becomes possible. The differential detection doubles the amount of change in current, enabling highly accurate detection. According to this configuration, the drain current changes even when acceleration is applied in the direction perpendicular to the substrate, but since the two transistors change in phase and in the same amount, differential detection does not result in erroneous detection. Further, even if the drain current changes due to the temperature characteristic of the transistor, it is not erroneously detected by the differential detection. This configuration has a simpler sensor shape than the configuration of (1).

According to the configuration of (3), the operation for removing the acceleration component contained in the yaw rate detection signal becomes possible.
By going through the manufacturing process as described in (4), the drain currents of the two transistors used for the differential can be easily made equal, and adjustment work such as trimming can be omitted.

[0018]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a configuration diagram showing a plan view of a first embodiment of a yaw rate sensor according to the present invention. Reference numeral 1 is a semiconductor substrate (here, a P-type silicon substrate is used). Anchor portions 21 to 24 are formed on, for example, four positions on the semiconductor substrate 1.
The weight 4 is supported by beams 31 to 34, one ends of which are supported by 1 to 24, respectively. The reason why the beams 31 to 34 are provided with a bend is that the weight 4 is movable in the x and y directions in the drawing, which are the horizontal directions of the substrate.

The weight 4 is for gaining a displacement amount due to the yaw rate, and also serves as a gate electrode in the transistor. Exciting movable electrodes 51 to 54 for receiving vibration are formed at four corners of the weight 4 so as to project in the horizontal direction of the substrate.

The above anchor portions 21 to 24 and the beams 31 to 3
4, the weight 4, and the excitation movable electrodes 51 to 54 are integrally formed of a heat resistant metal such as polysilicon or tungsten. In this embodiment, a typical material, polysilicon, is used.

That is, the weight 4 and the excitation movable electrodes 51 to 54 formed integrally with the weight 4 are arranged at a predetermined interval on the main surface of the semiconductor substrate 1, and are anchored via the beams 31 to 34. Held by parts 21-24.

On the other hand, on the semiconductor substrate 1, the beams 31 to 3 are formed.
4, a weight 4, and a lower electrode 9 having a shape corresponding to the shape is formed at a portion facing the movable electrodes 51 to 54 for excitation. The lower electrode 9 is composed of a diffusion layer formed by introducing N-type impurities into the semiconductor substrate 1 made of P-type silicon by means of ion implantation or the like. Is prevented from being displaced in the substrate direction and coming into contact with the substrate 1.

Further, on the semiconductor substrate 1, source electrodes 71 and 72 and drain electrodes 81 and 82 are formed respectively under the pair of opposing sides of the weight 4, and a part of them overlaps the weight 4. Configure a transistor with a gap. The source electrodes 71 and 72 and the drain electrodes 81 and 82 are diffusion layers formed by introducing N-type impurities into the semiconductor substrate 1 made of P-type silicon by means such as ion implantation.

Further, on the semiconductor substrate 1, the excitation movable electrodes 51 to 54 integrally formed with the weight 4 and the excitation fixed electrodes 61 to 64 are arranged to face each other with a predetermined gap. These excitation fixed electrodes 61 to 64 are formed of a polysilicon material at the same time as the excitation electrodes 51 to 54 and the like, and have a potential difference at a predetermined frequency between the weight 4 and the excitation movable electrodes 51 to 54 integrally formed. Is given to the weight 4 to give vibration in the x direction shown in the figure.

Although not shown in detail, the weight 4 is connected to an external circuit via the beams 31 to 34 and the anchor portions 21 to 24 and aluminum wiring on the substrate 1. The lower electrode 9 is also connected to an external circuit via the aluminum wiring on the substrate 1. Further, the excitation fixed electrodes 61 to 64 are also connected to an external circuit for supplying a voltage signal of a predetermined frequency via the aluminum wiring on the substrate 1.

However, it is assumed that the phase of the voltage signal is inverted by 180 degrees in the set of 61 and 62 and the set of 63 and 64. Further, the source electrodes 71, 72 and the drain electrode 8
Reference numerals 1 and 82 are connected to an external current detection circuit via aluminum wiring on the substrate 1.

In the above structure, a more specific structure will be described below with reference to FIG. FIG. 2A is A of FIG.
A semiconductor substrate 1 showing a cross-sectional structure corresponding to line A
Is composed of P-type silicon and has N on its main surface.
A source electrode 71 and a drain electrode 81, which are diffusion layers of type impurities, are formed. At this time, since the weight 4 functions as a gate, the inversion layer 91 is formed between the source electrode 71 and the drain electrode 81. Weight 4 and semiconductor substrate 1
A gap 100 is set between and, and the weight 4 can be displaced three-dimensionally.

FIG. 2B shows a sectional structure corresponding to the line BB in FIG. 1. The insulating film 11 is formed on the semiconductor substrate 1.
0 is formed on which the weight 4 is attached to the beams 32, 33,
It is supported via the anchor portions 22 and 23. That is,
The insulating film 110 sets the gap 100, and
₂ and Si ₃ N ₄ etc. A lower electrode 9 made of an impurity diffusion layer is formed on the main surface of the semiconductor substrate 1.

The insulating film 110 includes the weight 4 and the beams 31 to 31.
4 and the semiconductor substrate 1, which is a sacrificial layer that sets the gap between the semiconductor substrate 1 and the semiconductor substrate 1. The gap 100 is formed by etching away the portions corresponding to the anchor portions 21 to 24.
During this etching, the polysilicon, which is the material forming the weight 4, the beams 31 to 34, and the anchor portions 21 to 24, and the substrate 1 are not etched, and the insulating film 1 that is a sacrificial layer is not etched.
An etchant is used which only etches 10.

FIG. 2C shows a sectional structure corresponding to the line CC of FIG. 1, in which a gap 100 is set between the weight 4 and the surface of the substrate 1. FIG. 2D is D of FIG.
The cross-sectional structure corresponding to the -D line is shown in FIG.
Drain electrodes 81 and 8 which are diffusion layers due to impurities
2. The lower electrode 9 is formed, and the movable electrode 4 is formed via the gap 100. The inversion layer 9 is provided between the source electrode 71 and the drain electrode 81 and between the source electrode 72 and the drain electrode 82 facing the weight 4 functioning as a gate.
1, 92 are formed. At this time, the source electrodes 71, 7
2. Since the drain electrodes 81 and 82 are formed so as to project from the end of the weight 4, the inversion layers 91 and 92 are the source electrodes 7 and 7.
1 is not formed in the entire area between the drain electrode 81 and the source electrode 72 and the drain electrode 82. The weight 4 is an inversion layer 91,
The region 92 is the same, and the source electrode 71 and the drain electrode 8
1. The positions are set so that the currents between the source electrode 72 and the drain electrode 82 are equal.

The operation of the yaw rate sensor thus configured will be described. When a voltage is applied between the weight 4 and the semiconductor substrate 1, the inversion layers 91 and 92 are formed, and the source electrodes 71 and 72 and the drain electrodes 81 and 8 are formed.
An electric current flows between the two. Further, the fixed electrodes for excitation 61 to
The excitation voltage having a frequency between 64 and the excitation movable electrodes 51 to 54 is applied to the excitation fixed electrodes 61 and 62, 63 and 6
The weight 4 is applied to the substrate 1 by shifting the phase by 180 degrees.
And vibrate horizontally (x direction in FIG. 1). Since the Coriolis force generated by the yaw rate is proportional to the speed of this vibration, in order to increase the vibration speed,
The frequency is preferably selected at the resonance point where the amplitude becomes large.

When a yaw rate having an axis perpendicular to the semiconductor substrate 1 is generated for the weight 4 which is excited and vibrating in this way, Coriolis force proportional to the vibration speed and the mass of the vibrating body is generated, and the weight 4 is generated. Is displaced in the y direction shown by 1 in the figure. When the weight 4 functioning as a gate is displaced in the y direction, the current between the source electrodes 71 and 72 and the drain electrodes 81 and 82 changes, and the yaw rate can be detected by this change in current.

That is, when the weight 4 vibrates in the x direction in FIG. 1, there is no change in the inversion layer regions 91 and 92 corresponding to the gate width of the transistor, but when the yaw rate occurs, the weight 4 is caused by the Coriolis force. Are displaced in the y direction shown in FIG. At this time, the inversion layer regions 91 and 92 increase and decrease in reverse phase, and the source electrodes 71 and 72 and the drain electrodes 81 and 8 are formed.
Since the current between the two changes to the opposite phase, differential detection is possible.

The yaw rate detection circuit based on this differential detection is constructed as shown in FIG. In FIG. 3, 121,
Reference numeral 122 denotes a transistor for detecting the yaw rate (the gate electrode by the weight 4 in FIG. 1, the source electrode 7 on the semiconductor substrate 1 side).
1, 72 and drain electrodes 81, 82), 1
Reference numerals 31 and 132 are resistors required for current-voltage conversion, and 140 is a voltmeter for measuring voltage changes due to the yaw rate.

First, when the yaw rate is not generated, the resistance values of the resistors 131 and 132 are equal, and the transistor 12
Since the resistors 1 and 122 (inversion layer regions) are also configured to be equal to each other, the voltmeter 140 indicates 0V.

Next, when a yaw rate occurs, the resistances of the transistors 121 and 122 change to opposite phases, and the voltmeter 140
The potential difference is displayed on and the yaw rate is detected. In this case, since the potential difference is doubled as compared with the case where the transistor is used alone, highly accurate detection becomes possible.

When acceleration in the direction perpendicular to the substrate occurs, the gap 100 shown in FIG. 2A changes and the carrier concentration of the inversion layer 91 changes, so that the transistor 12 is formed.
The resistance of 1,122 changes, but this is transistor 1
Since there is the same phase and the same amount of change in 21 and 122, no potential difference occurs in the voltmeter 140. Therefore, erroneous detection due to acceleration can be prevented.

Further, regarding the resistance change due to the temperature characteristic generated in the transistors 121 and 122, since the transistors 121 and 122 have the same phase and the same amount, erroneous detection can be prevented.

FIG. 4 shows the manufacturing process of the source electrode 71 portion constituting the transistor section in four stages (A) to (D). The left side of the figure is a top view and the right side of the figure is a top view side. It is the AA sectional view taken on the line. The source electrode 72 and the drain electrodes 81 and 82 are completely the same as the source electrode 71, and are therefore omitted.

First, as shown in FIG. 4A, an impurity is introduced into the surface of the semiconductor substrate 1 by ion implantation to form a diffusion resistance 71 which becomes a source electrode. Next, FIG. 4 (B)
As shown in FIG. 3, a sacrificial layer 110 and a polysilicon layer are formed on the substrate 1, and the polysilicon layer is processed to form a weight 4 that functions as a gate. When forming the weight 4, an opening 150 not shown in FIG. 1 is provided. The opening 150 is formed on the end of the source electrode 71.

Thereafter, as shown in FIG. 4C, a resist 160 is formed by a photo process. At this time, the resist 160 has an opening 152 larger than the opening 150.
Is formed. Using this resist 160 as a mask,
The sacrifice layer 110 below the opening 150 is removed by etching to form the opening 151. At this time, the opening 151
Is preferably slightly larger than the opening 150.

Ions are implanted through the openings 152, 150 and 151 to form an amorphous electrically insulating region 170 on the semiconductor substrate 1. This insulating region 170
Is formed in the opening 150 of the weight 4 by self-alignment,
The final source electrode 71 is formed by partially insulating the source electrode 71. The insulating region 170 becomes larger than the opening 150 due to the scattering of the implanted ions, and the region 1 that is also insulated in the portion facing the weight 4
71 can be formed. The impurities used for ion implantation are Ar
And the like, and those which do not serve as a dopant are preferable.

Finally, as shown in FIG. 4D, the sacrifice layer is etched to form the gap 100 and make the weight 4 movable. Larger than the opening 150 the insulating region 17 0
When the weight 4 is displaced in the y direction due to
The overlap between the source electrode 71 and the drain electrode 81 increases, the inversion layer region 91 expands, and the current increases. When the weight 4 is displaced in the opposite direction, the inversion layer region 9
Since 1 is narrowed, the current decreases.

By the way, when it is attempted to detect the horizontal displacement of the weight 4, a source-drain electrode having a region which does not overlap with a portion of the weight 4 which functions as a gate is formed. The gate width must be changed by the displacement of the weight 4.

In the case of such a structure, a normal I
After forming the gate done in the C process, the source,
A self-aligned FET manufacturing method for forming a drain cannot be adopted. Therefore, the gate is formed after forming the source and drain electrodes.

Therefore, due to the displacement of the gate that occurs during the process, the overlap between the gate and the source / drain electrodes changes, and the initial current value differs from the designed value, resulting in an offset.

On the other hand, according to the manufacturing method shown in FIG. 4, it is possible to always form a constant inversion layer width (corresponding to the gate width) 172 with respect to the width 41 shown in FIG. It is possible to prevent the occurrence of offset.

Further, in the formation of the gate width utilizing the diffusion of impurities as disclosed in Japanese Patent Application No. 5-311762, there is a problem in that a sufficient current value for detection cannot be secured because the gate width is very small. By increasing the width 41 of the weight 4 shown in FIG. 4D, a sufficient amount of current can be secured.

Although it is possible that the width 41 shown in the figure changes and the inversion layer width 172 changes due to process variations, the inversion layer width formed between the source electrode 72 and the drain electrode 82 used for differential detection. Is expected to change similarly, it is possible to prevent the occurrence of offset.

In the yaw rate sensor described in the above embodiment, the number of beams is four, but the number of beams is not necessarily four. Further, the excitation electrodes are provided on both sides in the vibration direction, but this may of course be provided on one side, and even if two electrodes are provided on each side, one may be provided, and the excitation electrodes may be arranged on a side orthogonal to the oscillation direction. It may be provided throughout. Although the P-type semiconductor is used as the substrate in the description, it may be made of an N-type semiconductor. In this case, the diffusion electrode is of P type.

FIG. 5 shows the configuration of the second embodiment according to the present invention. However, differences from the first embodiment will be mainly described here. That is, in the first embodiment, the weight is vibrated in the horizontal direction with respect to the substrate and the yaw rate having the rotation axis in the vertical direction of the substrate is detected. In this embodiment, the weight is vibrated in the vertical direction with respect to the substrate, and the horizontal direction of the substrate is detected. The purpose is to detect the yaw rate having an axis in the direction.

In FIG. 5, a semiconductor substrate 1a and a weight 4a which also functions as a gate in a transistor are beams 31a and 32.
a, 33a, 34a, anchor portions 21a, 22a, 23
It is held at a predetermined interval with respect to the substrate 1a via a and 24a. A fixed electrode 9a for excitation is provided on the surface of the substrate 1a with a weight 4a and beams 31a, 32a, 33a, 34a.
Is provided in a portion facing to.

Further, on the surface of the semiconductor substrate 1a, the source electrodes 71a, 72a and the drain electrodes 81a, 8a of the transistors are provided at positions facing the pair of sides of the weight 4a, respectively.
2a is formed.

That is, in the first embodiment, the beams 31, 3 are
By providing the bent portions at 2, 33, and 34, the weight 4 enables the two-dimensional displacement of the substrate 1 in the horizontal direction, whereas in the second embodiment, the displacement of the weight 4a is caused in the vertical direction of the substrate (see FIG. 5). Since it is the middle z direction) and the substrate horizontal direction (x direction in FIG. 5),
The beams 31a, 32a, 33a, 34a have no bent portion. Further, in the first embodiment, the weight 4 and the beams 31, 32, 3 are
The lower electrode 9 for preventing the generation of electrostatic force is formed on the surfaces of the substrates 1 and 3 facing each other, but in the second embodiment, the fixed electrode 9a for excitation is formed instead of the lower electrode 9. There is.

The actual operation is as follows. First, when a voltage is applied between the weight 4a and the excitation fixed electrode 9a at a predetermined frequency, the weight 41 vibrates in the direction perpendicular to the substrate 1a (z direction in FIG. 5). Due to this vibration, the weight 4a (1)
The velocity V of the equation occurs.

On the other hand, when the yaw rate is generated around the y direction shown in FIG. 5, the Coriolis force acts in the x direction in the figure, and the weight 4a is displaced in the x direction. At this time, between the source electrode 71a and the drain electrode 81a, the source electrode 72a
The drain current flowing between the drain electrode 82a and the drain electrode 82a changes to the opposite phase. Therefore, the yaw rate is detected by the differential detection described above. The second embodiment can have a simpler structure than the first embodiment.

FIG. 6 shows the configuration of the third embodiment according to the present invention. However, in FIG. 6, the same parts as those in FIG. 5 are denoted by the same reference numerals, and here, the differences from the second embodiment will be mainly described.

That is, in the second embodiment, the substrate 1a where the weight 4a and the beams 31a, 32a, 33a and 34a are opposed to each other.
The fixed electrode 9a for excitation was provided on the entire surface of the lower electrode 9a in this embodiment as in the first embodiment.
b, and only a part of the substrate 1a facing the center of the weight 4a is used as the excitation fixed electrode 9c. The lower electrode 9b is held at the same potential as the weight 4a in order to suppress the generation of electrostatic force.

With this structure, the magnitude of the electrostatic force can be set by the area of the excitation fixed electrode 9c in addition to the applied voltage between the excitation fixed electrode 9c and the weight 4a.
This makes it possible to adjust the applied voltage during excitation to a desired value by adjusting the area of the excitation fixed electrode 9c.

Particularly, in the sensor structure as shown in this embodiment, the distance between the movable electrode 4a and the substrate 1a is on the order of μm, and a very large electrostatic force is generated by a minute voltage. Therefore, when the movable electrode 4a is excited. It is necessary to make a fine adjustment of the applied voltage in order to prevent the substrate 1a from being adsorbed, but as in this embodiment, the excitation fixed electrode 9c is provided on a part of the surface of the substrate 1a facing the center of the weight 4a. If formed, the area where the electrostatic force is generated can be suppressed, and fine adjustment of the applied voltage becomes unnecessary.

[0061]

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[0089]

As described above, according to the semiconductor yaw rate sensor of the present invention, even if it is a transistor type, it is possible to solve the deterioration of the detection accuracy and the erroneous detection of acceleration, and to realize the miniaturization and high performance. For example, it can be mounted on an automobile or the like and effectively used for vehicle body control, navigation, etc.
Further, such a semiconductor yaw rate sensor has a conventional I
It can be easily manufactured by applying the C manufacturing process, and in particular, the transistor structure portion for detecting the yaw rate can be manufactured with high accuracy due to the member displaced by the action of the yaw rate, so that it is highly sensitive and reliable. A rich yaw rate sensor can be easily obtained.

[Brief description of drawings]

FIG. 1 is a first semiconductor yaw rate sensor according to the present invention.
FIG. 3 is a configuration diagram showing a configuration of an embodiment.

FIG. 2 is a sectional view showing a sectional structure of each part of the embodiment.

FIG. 3 is a circuit diagram showing a configuration of a yaw rate detection circuit of the same embodiment.

FIG. 4 is a cross-sectional view showing stepwise a manufacturing process of a source electrode portion which constitutes the transistor portion of the embodiment.

FIG. 5 is a configuration diagram showing a configuration of a second embodiment according to the present invention.

FIG. 6 is a configuration diagram showing a configuration of a third embodiment according to the present invention.

[Explanation of symbols]

1, 1 a ... Semiconductor substrate, 21-24, 21 a- 24 a ...
Anchor parts 31 to 34, 31a to 34a ... Beams, 4, 4
a ... weight, 5 1 to 5 4 ... excitation movable electrode, 61-6 4 ...
Excitation fixed electrode, 71, 72, 71a, 72a ... Source electrode, 81, 82, 81a, 82a ... Drain electrode,
9, 9 b ... Lower electrode, 91, 92 ... Inversion layer region, 9 a,
9c ... Exciting fixed electrode, 100 ... Gap, 110 ... Insulating film, 121, 122 ... Yaw rate detecting transistor , 131, 132 ... Resistance, 140 ... Voltmeter, 150-
Reference numeral 152 ... Opening portion, 160 ... Resist, 170 ... Insulating region, 41, 171, 172 ... Width.

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-6-196721 (JP, A) JP-A-6-196722 (JP, A) JP-A-6-204502 (JP, A) JP-A-61- 114123 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01C 19/56 G01P 9/04 H01L 29/84

Claims (4)

(57) [Claims] 1. A semiconductor substrate, and a semiconductor substrate disposed above the semiconductor substrate with a predetermined space therebetween.
A weight that is displaceably supported by a beam structure and integrally formed with a movable electrode for excitation so as to project in parallel with the semiconductor substrate, and that functions as a gate electrode of a transistor, and a predetermined distance above the semiconductor substrate. And a fixed electrode for excitation, which is disposed with a gap between the movable electrode and the movable electrode and vibrates the weight by using electrostatic force, and is disposed horizontally with respect to the semiconductor substrate, and one end portion of the fixed electrode is in front of the other.
Two or more pairs of source electrodes and drain electrodes which are formed so as to partially overlap each other in the periphery of the weight, and at least the source electrode and the drain of a portion of the semiconductor substrate which faces the weight. A lower electrode formed in a region having no electrode, the gate electrode formed of the weight, the source electrode and the drain electrode forming a transistor, and the excitation fixed electrode forming the weight in the semiconductor substrate at a predetermined cycle. When excited in the horizontal direction, the displacement of the weight in the horizontal direction due to the action of the yaw rate is differentially detected by the change in the current between the two or more pairs of sources and drains. Semiconductor yaw rate sensor. 2. A semiconductor substrate, wherein arranged at a predetermined distance above the semiconductor substrate, is supported freely displaced by the beam structure, and a weight which serves as a gate electrode of the transistor, before Symbol semiconductor substrate and a horizontal Are placed in the
Two or more pairs of source electrodes and drain electrodes which are formed so as to partially overlap each other in the periphery of the weight, and at least the source electrode and the drain of a portion of the semiconductor substrate facing the weight. An excitation lower electrode that is formed in a region without an electrode and that vibrates the weight by using electrostatic force; and a transistor is configured by the gate electrode and the source electrode and drain electrode by the weight, and the excitation lower electrode is provided. said weight with a predetermined cycle by the electrodes when excited in the semiconductor substrate and the vertical direction, the weight of the semi-conductor substrate and the horizontal direction of the current between the displacement the two or more sets of source and drain caused by the action of the yaw rate A semiconductor yaw rate sensor characterized by being differentially detected by a change. 3. The semiconductor substrate is equipotential to the weight in at least a region where the source electrode, the drain electrode, and the lower electrode for excitation are not provided in the facing portion of the movable electrode, and electrostatic force between the weight and the substrate is applied. The semiconductor yaw rate sensor according to claim 2, wherein the semiconductor yaw rate sensor has a lower electrode for suppressing the generation thereof. 4. Two pairs of semiconductor substrates are prepared by introducing impurities into the surface of the semiconductor substrate.
The first step of forming the source electrode and the drain electrode described above, the second step of forming the sacrificial layer on the main surface of the semiconductor substrate, the beam-shaped weight on the sacrificial layer, and the excitation fixed electrode for the weight. The third step of forming and one of the source electrode and the drain electrode on the weight
Shape the opening so that the end overlaps the weight.
A fourth step of forming the opening , a fifth step of etching away the sacrificial layer exposed by forming the opening , and ions in the semiconductor substrate in self-alignment with the opening.
Inject it into the area around the weight, and
And one end of the source and drain electrodes
Sixth step of setting the burlap region as the gate width
And the displacement of the weight in the horizontal direction with respect to the semiconductor substrate
Differential detection with current change between two or more pairs of source and drain
The sacrificial layer below the weight so that
And a seventh step of removing the weight, wherein the weight is vibrated by an electrostatic force from the excitation fixed electrode and is displaced by a Coriolis force generated by a yaw rate.