JPH10123166A - Semiconductor acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain stable output characteristics and at the same time simplify structure. SOLUTION: A semiconductor sensor chip 21 has a weight part 23 that is supported via beam part 24 in a frame body 22 and is structured to detect an acceleration up to approximately ±1G by utilizing the piezo resistance effect of a resistance element being formed at the above beam part 24. The semiconductor sensor chip 21 is supported for a pedestal 26 with a thermal coefficient of expansion that is equivalent to it via the frame body 22. At this time, the frame 22 and the pedestal 26 are adhered by a flexible adhesive 29 where a plurality of resin beads 28 functioning as a spacer are blended. Then, by setting the dimension of an air gap between the weight part 23 and the pedestal 26 to 7-15μm in that adhesion state, the air damping of the weight part 23 is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor acceleration sensor for detecting acceleration by using a semiconductor material having a large piezoresistance coefficient, and more particularly to a relatively low level acceleration of about ± 1 G or less. The present invention relates to a semiconductor acceleration sensor configured as described above.

[0002]

2. Description of the Related Art FIGS. 35 and 36 show an example of a conventionally known semiconductor acceleration sensor. FIG. 35 shows a planar shape of a semiconductor sensor chip which forms the core of the semiconductor acceleration sensor, and FIG. 36 shows a schematic sectional structure of the semiconductor acceleration sensor.

In FIG. 35, a semiconductor sensor chip 1
Is formed using a silicon single crystal substrate.
Inside the first frame 2, attach the second frame 3 to the arm 4
And the weight 5 is supported inside the second frame 3 in a cantilever manner via four beams 6. In this case, each of the beam portions 6 (portion where a large distortion occurs when an acceleration is applied) includes:
A resistance element (not shown) is formed by a diffusion method or the like, and the acceleration is detected by using a strain gauge formed by these resistance elements.

[0006] In a semiconductor acceleration sensor 7 shown in FIG. 36, a first frame 2 of a semiconductor sensor chip 1 is anodically bonded to a peripheral portion of a glass pedestal 8, and is supported on the glass pedestal 8. With such a support structure, the distortion caused by the difference in the coefficient of thermal expansion between the semiconductor sensor chip 1 and the glass pedestal 8 causes the beam portion 6 (resistance element portion) to be distorted.
Is absorbed by the arm 4 (see FIG. 35). The glass pedestal 8 is formed with a concave portion 8 a at a position corresponding to the weight portion 5 and the beam portion 6, and a gap of about 400 μm exists between the concave portion 8 a and the weight portion 5. Has become.

The semiconductor sensor chip 1 and the glass pedestal 8 are mounted on a ceramic substrate 9 together with a processing circuit 10 and the like, and are housed in a metal case 11 in the mounted state. In this case, the oil 12 is contained in the metal case 11.
The damping of the weight portion 5 of the semiconductor sensor chip 1 is performed by the oil 12. The processing circuit 10 and the semiconductor sensor chip 1 are connected by bonding wires 13.

[0006]

However, in the above-mentioned conventional structure, there is a problem that the structure is generally complicated, for example, a sealing structure for preventing leakage of the oil 12 is required. In recent years, there has been an increasing need to detect relatively low levels of acceleration of about 1 G or less in applications such as automobile ABS or a device for preventing sideslip during turning. However, the conventional configuration using oil damping as described above. With such an acceleration sensor, it has been difficult to sufficiently reduce the detectable acceleration.

Therefore, in recent years, the above problems can be solved all at once by making full use of micromachining technology, and the need to detect a relatively low level acceleration of about ± 1 G or less can be met. A semiconductor acceleration sensor having a structure has been considered.

Specifically, by adopting a configuration in which the semiconductor sensor chip is supported on a pedestal made of a material having the same thermal expansion coefficient as that of the semiconductor sensor chip (preferably, the same material), the thermal expansion of the two is achieved. Eliminates adverse effects due to distortion due to differences in coefficients. In addition, by adopting a configuration in which the air gap formed between the weight portion of the semiconductor sensor chip and the pedestal performs air damping of the weight portion, FIG.
The oil 12 and its sealing structure as shown in 6 are not required, thereby simplifying the structure, and detecting a relatively low level acceleration of about ± 1 G or less by increasing the processing accuracy of the beam portion and the like. Make it possible.

By the way, a semiconductor acceleration sensor having such a configuration is actually manufactured, and its output characteristics, in particular, an output value in a state of zero acceleration serving as a reference of the sensor characteristics (hereinafter referred to as 0G output). Measured, the phenomenon that the 0G output fluctuated every measurement occurred. The inventor of the present application has carefully repeated a wide variety of experiments and analysis of experimental results on such a phenomenon, and has come to the conclusion that the cause is caused by electrostatic attraction generated inside the semiconductor acceleration sensor.

That is, a power supply voltage for driving the semiconductor sensor chip is applied to the semiconductor sensor chip.
Since it is inevitable that a certain amount of capacitance exists between the semiconductor sensor chip and the pedestal, the surface of the weight portion of the semiconductor sensor chip and a predetermined air gap exist in the weight portion. Electrostatic induction phenomena occur in that charges of different polarities are collected on the surface of the opposing pedestal, and the effect of the electric field accompanying this causes an electrostatic attraction between the weight portion and the pedestal, thereby causing an electrostatic attraction between the two. It was found that the size of the air gap fluctuated from the initially set value, and that such fluctuation caused the variation of the 0G output. Also. It has also been found that there is a phenomenon that the fluctuation range of the 0G output varies depending on the initial setting value of the air gap size and the potential difference generated between the semiconductor sensor chip and the pedestal.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to manage a gap size between a weight portion displaced in accordance with acceleration and a pedestal opposed thereto. Alternatively, a semiconductor acceleration sensor is provided in which stable output characteristics can be obtained simply by adopting a configuration for suppressing a potential difference generated between a semiconductor sensor chip and a pedestal, and the structure can be simplified. Is to do.

[0012]

Means for Solving the Problems In order to achieve the above object, the means described in claim 1 can be employed. The greatest feature of this means is that the weight portion of the semiconductor sensor chip and the pedestal supporting the sensor chip are arranged close to each other to perform air damping of the weight portion. The dimension of the air gap between the weight portion and the pedestal is set to 7 μm or more.

According to an experiment conducted by the inventor of the present invention, an acceleration up to about ± 1 G is provided by using a piezoresistive effect of a resistance element formed on the beam, having a weight supported via the beam. In the semiconductor sensor chip capable of detecting the air gap, the air gap dimension between the weight portion and the pedestal is 7 μm.
It has been confirmed that, when the weight is equal to or more than the above, the fluctuation of the 0G output (output value at zero acceleration) caused by the electrostatic attraction generated between the weight portion and the pedestal falls within an allowable range.

Therefore, by adopting the above means,
Deterioration of output characteristics due to electrostatic attraction generated inside can be prevented, and stable output characteristics can be obtained. Further, since the oil for damping as in the conventional configuration is not required, the structure can be simplified. In addition, according to the first aspect of the present invention, since the thermal expansion coefficients of the semiconductor sensor chip and the pedestal supporting the semiconductor sensor chip are made equal, distortion generated between the semiconductor sensor chip and the pedestal can be suppressed. .

According to a second aspect of the present invention, the size of the air gap between the weight portion and the pedestal is set in a range of 7 to 15 μm. In this case, according to the experiment of the inventor of the present application, the size of the air gap between the weight portion and the pedestal was 15 μm.
It has been found that a sufficient air damping effect can be obtained if it is less than about m. Therefore, by adopting the above means, it is possible to simultaneously prevent the output characteristics from deteriorating due to the vibration of the weight portion.

According to a third aspect of the present invention, the relationship between the air gap dimension d between the weight portion and the pedestal and the bottom area S of the weight portion is defined as 0.01 ≦ S / d ² ≦ 0.05. It is characterized in that the air gap is filled, that is, the set value of the air gap dimension d is changed according to the size of the bottom area S of the weight portion.

According to an experiment conducted by the inventor of the present application, the acceleration having a weight portion supported via a beam portion and having an acceleration up to about ± 1 G by utilizing a piezoresistance effect of a resistance element formed on the beam portion. In a semiconductor sensor chip capable of detecting the force, if the value of S / d ² is 0.05 or less, the fluctuation of the 0G output due to the electrostatic attraction generated between the weight portion and the pedestal is within an allowable range. It has been confirmed that it fits within. Also,
It has been found that when the value of S / d ² is 0.01 or more, a sufficient air damping effect can be obtained.

Therefore, by adopting the above means,
Deterioration of output characteristics due to electrostatic attraction generated inside and deterioration of output characteristics due to vibration of the weight portion can be prevented at the same time, and stable output characteristics can be obtained.

According to the fourth aspect, the space between the pedestal and the frame of the semiconductor sensor chip supported by the pedestal is
Since it is adhered by the flexible adhesive, the stress acting on the semiconductor sensor chip side from the pedestal side can be reduced, and the output characteristics can be further stabilized.

According to the fifth aspect, the frame for supporting the semiconductor sensor chip on the pedestal and the auxiliary frame for supporting the weight are supported in a cantilever manner via the arm. Therefore, mechanical distortion on the frame side is absorbed by the arm portion, and as a result, it is possible to contribute to stabilization of output characteristics.

According to the sixth aspect of the present invention, the dimensional control of the air gap between the weight portion and the pedestal is performed by the spacer provided between the pedestal and the frame on the semiconductor sensor chip side. Therefore, the dimensional control of the air gap can be easily performed.

According to the seventh aspect of the present invention, the stress acting on the semiconductor sensor chip side from the pedestal side can be reduced by the flexible adhesive, and the weight portion and the resin beads blended in the adhesive can be reduced. The dimensional control of the air gap between the pedestals can be strictly and easily performed. In addition, since the resin beads have a general property of having a relatively low elastic modulus, there is no possibility that the presence of the resin beads impairs the stress relaxation function of the flexible adhesive.

According to the means of the present invention, the dimension of the air gap between the weight portion and the pedestal is controlled by the projection integrally formed on the pedestal side or the frame side.
There is an advantage that no extra parts are required.

According to the ninth aspect of the present invention, the voltage applying means for applying a voltage of the same level as the power supply voltage applied to the semiconductor sensor chip to the base is provided.
The electric potentials of the pedestal and the semiconductor sensor chip are forcibly held so as to be at the same level. As a result, it is possible to eliminate an adverse effect due to external static electricity, and to prevent an extreme fluctuation of the 0G output.

According to the tenth aspect, since excessive deformation of the weight portion is restricted by the convex portion, there is no possibility that the beam portion is damaged when excessive acceleration acts.

According to the eleventh aspect, the variation in the initial characteristics of the 0 G output can be suppressed by the burn-in process, and as a result, the yield in the manufacturing process is improved.

[0027] In order to achieve the above object, a first aspect is provided.
The means described in (2) can be adopted. The feature of this means is that a support member having a function of suppressing generation of a potential difference between the semiconductor sensor chip and the pedestal when the semiconductor sensor chip is supported on the pedestal is used.

According to such a configuration, the potential difference generated between the semiconductor sensor chip and the pedestal is reduced, so that the electrostatic attraction generated between the weight portion and the pedestal is also reduced. As a result, it is possible to prevent output characteristics from deteriorating due to electrostatic attraction generated inside, and to obtain stable output characteristics. Further, in order to obtain such an effect, it is only necessary to provide a support member having predetermined electrical characteristics, so that the structure can be simplified.

According to a thirteenth aspect of the present invention, the resistance between the semiconductor sensor chip and the pedestal via the supporting member is set to 10 or more.
It is characterized by being set to ¹⁰ Ω or less. According to the experiment of the inventor of the present application, it was found that when the resistance value between the semiconductor sensor chip and the pedestal was 10 ¹⁰ Ω or less, the potential difference generated between the sensor chip and the pedestal could be suppressed to an allowable range. I have. Therefore, by adopting the above means, it is possible to effectively prevent the deterioration of the output characteristics due to the electrostatic attraction generated inside.

According to the measures of claims 15 and 17,
Since the potential difference generated between the semiconductor sensor chip and the pedestal becomes small, the deterioration of the output characteristics can be prevented, and the size of the air gap between the weight portion and the pedestal can be controlled by the beads included in the support member. The configuration as described in the item 1 can also be adopted.

In particular, according to the present invention, the supporting member for supporting the semiconductor sensor chip on the pedestal comprises a flexible adhesive for adhering the semiconductor sensor chip and the pedestal, and a compounding agent for the flexible adhesive. Since it is composed of a plurality of resin beads formed, the potential difference between the semiconductor sensor chip and the pedestal can be reduced, and the stress acting on the semiconductor sensor chip from the pedestal side can be reduced. Can be further stabilized.

According to the twenty-first aspect, the pedestal for supporting the semiconductor sensor chip and the semiconductor sensor chip are integrally formed of the same material, so that the potential difference generated between the semiconductor sensor chip and the pedestal is sufficient. And the electrostatic attraction generated between the weight portion and the pedestal is also significantly reduced. As a result, it is possible to prevent output characteristics from deteriorating due to electrostatic attraction generated inside, and to obtain stable output characteristics. According to this means, the number of components can be reduced.

According to the measures of claims 23 and 24,
A situation in which the influence of external static electricity on the semiconductor sensor chip is prevented by the electrostatic shield. That is, when static electricity from the outside acts on the semiconductor sensor chip, a large electrostatic attraction is generated between the weight portion and the pedestal, and 0 G
Although there is a possibility of causing an extreme fluctuation of the output, such a situation is prevented by the electrostatic shield.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a sectional structure of a main part of the semiconductor acceleration sensor, FIG. 2 shows a plan view of a semiconductor sensor chip which is a core of the semiconductor acceleration sensor, and FIG. 3 shows a bridge circuit formed on the semiconductor sensor chip. (Strain gauge) is schematically shown, and FIG. 4 shows the bridge circuit.

In FIG. 2, the semiconductor sensor chip 21
Is formed by electrochemically etching a material having a large piezoresistance coefficient such as a silicon single crystal substrate, and a weight 22 is placed inside a frame 22 having a size of about 3 × 3 mm to 4 × 4 mm. The portion 23 is supported in a doubly supported manner via four beam portions 24 symmetrically arranged.

Each of the beam portions 24 is formed by using, for example, an epitaxial layer portion formed on a silicon single crystal substrate. Each of the beam portions 24 is provided with two resistive elements (reference numerals R11 to R14, R21 in FIGS. 3 and 4) by a diffusion method or the like.
To R24) are formed, and the acceleration is detected using a bridge circuit formed by these resistance elements.

More specifically, as shown in FIG.
4, the resistance elements R11, R12, R13, R
Each pair of R21, R22, and R23, R24 is provided in a positional relationship such that one of the pair contracts and deforms in accordance with the displacement of the weight 23, and the other expands and deforms. Then, two series resistors (R11 and R21, R13 and R23, R12
And R22, R14 and R24) as one side, and a pair of input ends T1 and T2 and a pair of output ends T3 and T4 of the bridge circuit are connected to four bridges formed on the frame 22. It is connected to the bonding pad 22a via a thin-film wiring pattern.

As shown in FIG. 4, the bridge circuit is configured such that the resistance elements deforming in the same direction are located on sides facing each other. Also, the input terminal T1
And T2 are connected to a power supply terminal + Vcc and a ground terminal GND, respectively, and output terminals T3 and T4 are connected to a positive output terminal + V and a negative output terminal -V, respectively.
It should be noted that a thin-film wiring pattern is also used for forming a bridge circuit, and this wiring pattern is denoted by reference numeral a in FIG.

In this case, the weight of the weight 23 is set to, for example, about 1.4 mg in order to detect an acceleration up to about ± 1 G by utilizing the piezoresistance effect of the resistance element. In addition, the thickness, width, and length of the beam portion 24 are 4 to 7 μm, 140 to 180 μm, and 5 respectively.
It is set to about 30 to 570 μm. However, these weights and dimensions are merely examples, and when the weight of the weight 23 is changed, the dimensions of the thickness, width, and length of the beam 24 are naturally changed. Will be done.

In FIG. 1, the semiconductor acceleration sensor 25
(Hereinafter, abbreviated as a G sensor) supports the semiconductor sensor chip 21 on a pedestal 26 via a frame 22 and stores an integrated body of the semiconductor sensor chip 21 and the pedestal 26 in a housing 27 described later. It is constituted by. The pedestal 26 is formed of a material having the same coefficient of thermal expansion as the semiconductor sensor chip 21, specifically, a silicon substrate of the same material.

In this case, the space between the frame 22 and the base 26 is
It is bonded by a flexible adhesive 29 containing a plurality of resin beads 28 as spacers. In the bonded state, the space between the weight 23 and the pedestal 26 of the semiconductor sensor chip 21 is sufficiently close. By doing so, the damping portion 23 is configured to perform air damping. Specifically, by selecting the diameter of the resin beads 28, the size of the air gap between the weight portion 23 and the pedestal 26 is set in the range of 7 to 15 μm, preferably in the range of 8 to 15 μm.

Generally, resin beads have a low elastic modulus, but the resin beads 28 used in this embodiment are
It is desirable that the elastic modulus is 10 GPa or less.
In order to satisfy such demands, polydinivir benzene resin, silicone resin, urethane resin, acrylic resin,
Polyimide resin, flexible epoxy resin, vinyl resin, etc. can be used.

The flexible adhesive 29 preferably has an elastic modulus of 500 MPa or less. For example, silicone resin, urethane resin, acrylic resin, polyamide resin, polyimide resin, flexible epoxy resin, or the like is used. it can.

As shown in FIGS. 5 and 6, the pedestal 26
In a state housed in a concave portion 27 a formed in the housing 27, it is fixed on a ceramic substrate 27 b constituting the housing 27 by adhesion. For such bonding, a flexible adhesive 3 containing a plurality of resin beads 30 is used.
1 (see FIG. 1). Also in this case, it is desirable to use a resin bead 30 having an elastic modulus of 10 GPa or less, as described above. It is desirable to use one having an elastic modulus of 500 MPa or less.

The housing 27 is formed by laminating a plurality of ceramic substrates 27b, and is formed in a box shape having the above-mentioned concave portion 27a and a trapezoidal portion 27c adjacent thereto. On the trapezoidal portion 27c, an amplifying circuit 32 having a function of applying a power supply voltage to the semiconductor sensor chip 21 and amplifying a detection output by the sensor chip 21, and a level of the power supply voltage applied to the amplifier circuit 32 An adjustment circuit 33 for performing adjustment or the like is die-bonded.

The ceramic substrate 27b constituting the housing 27 is formed by using a conductive paste (not shown) printed between the substrates 27b, a through-hole (not shown) penetrating each substrate 27b, and the like. In addition, a plurality of wiring patterns for supplying power and extracting detection output are formed.

In this case, as shown in FIG. 6, on the upper edge of the housing 27, a group of external terminals 27d connected to those wiring patterns is provided, and
7c is provided with an internal terminal group 27e also connected to the wiring pattern. In addition, the semiconductor sensor chip 2
1 and the amplifier circuit 32, and between the amplifier circuit 32, the adjustment circuit 33, and the internal terminal group 27e are connected by wire bonding means.

In particular, as shown in FIGS. 1 and 5, for example, an aluminum paste or a copper paste is provided between a ceramic substrate 27b facing the concave portion 27a of the housing 27 and a ceramic substrate 27b located below the ceramic substrate 27b. Alternatively, a thin-film electrostatic shield 34 made of a conductive material such as tungsten paste is formed over the entire area. Although not specifically shown, the electrostatic shield 34 is connected to a ground line using a through hole or the like formed in the ceramic substrate 27b.

On the housing 27, a lid 35 (see FIG. 5) made of, for example, a ceramic substrate is provided by air bonding to hermetically seal the inside thereof. 25 is completed. In practice, the output characteristics are stabilized by performing burn-in processing on at least the semiconductor sensor chip 21 and the pedestal 26 supporting the semiconductor sensor chip 21. In the present embodiment, for example, a predetermined voltage (5 to 6) is applied to the semiconductor sensor chip 21.
(Approximately 120 V) while applying a voltage
The burn-in process of exposing to the atmosphere for a predetermined time (about 6 hours) or more is performed.

According to the configuration of the present embodiment described above, the following operations and effects can be obtained. That is,
In this embodiment, by setting the size of the air gap between the weight portion 23 of the semiconductor sensor chip 21 and the pedestal 26 supporting the sensor chip 21 in the range of 7 to 15 μm, the weight portion 23 Is damped by air damping between the weight portion 23 and the pedestal 26. In the case of such a configuration, it is apparent that the size of the air gap dimension is deeply involved in the amount of vibration damping due to air damping.

The inventor of the present application can detect acceleration up to about ± 1 G using the piezoresistance effect of the G sensor 25 configured as described above, that is, the resistance element formed on the beam portion 24. The relationship between the vibration of the weight portion 23 and the size of the air gap between the weight portion 23 and the pedestal 26 was determined by experiment for the G sensor 25 having the semiconductor sensor chip 21 described above. In this experiment, the G sensor 25
This is to examine the amount of vibration attenuation (air damping characteristic) in a state where vibration is applied to the weight portion 23, and the experimental data is shown in FIG.

As is apparent from FIG. 9, the weight 23
If the size of the air gap between the base 26 and the base 26 is about 15 μm or less, it is understood that a sufficient air damping effect can be obtained in general specifications.
It is possible to prevent the output characteristics of the G sensor 25 from deteriorating due to the vibration of the weight 23. In order to satisfy stricter specifications, for example, a specification of a vibration attenuation amount of 3 dB or less, the air gap dimension may be set to about 11.5 μm or less.

The reason why the lower limit of the size of the air gap between the weight portion 23 and the pedestal 26 is set to 7 μm in the present embodiment is as follows. That is, the G sensor 25
As a result of the inventor of the present invention, the phenomenon in which the output value in the state of zero acceleration (hereinafter referred to as “0G output”), which is a reference of the sensor characteristics in the above, varies.
It is determined that the output level always fluctuates in a certain direction, and that the direction of the fluctuation is a direction in which the weight portion 23 is drawn to the pedestal 26 side. Further, the cause of the fluctuation occurs inside the G sensor 25. We concluded that it was due to electrostatic attraction.

Such a phenomenon will be described with reference to FIG. 7 showing a sectional structure of a main part of the G sensor 25. A power supply voltage for driving the semiconductor sensor chip 21 is applied to the semiconductor sensor chip 21, and the semiconductor sensor chip 21 and the pedestal 26 are adhered to each other by a flexible adhesive 29 having an insulating property. Due to such a configuration, it is inevitable that a certain amount of capacitance exists between the two.

For this reason, as shown in FIG. 7, for example, positive charges (+) are collected on the surface of the weight 23 on the side facing the pedestal 26, and the negative polarity of the opposite polarity is collected on the pedestal 26 side. An electrostatic induction phenomenon in which charges (−) are collected occurs, and the weight portion 23 and the pedestal 2
An electrostatic attraction F expressed by the following equation is generated between 6.

[0056]

F = 1/2 × ε × S × (V / d) ² where ε is the relative permittivity of air, S is the bottom area of the weight portion 23,
V indicates the potential difference between the weight 23 and the pedestal 26, and d indicates the size of the air gap.

When such an electrostatic attractive force F is generated, the weight 23 is attracted to the pedestal 26 side.
This causes variation in the G output. Therefore, from the above equation,
It can be seen that the fluctuation range of the 0G output varies depending on the initial set value of the air gap dimension between the weight 23 and the pedestal 26.

As described above, the inventor of the present application carried out the work of confirming the effect of the size of the air gap on the 0G output by calculation and experiment. That is, FIG. 8 shows the relationship between the potential difference between the semiconductor sensor chip 21 and the pedestal 26 and the amount of fluctuation of the 0G output by setting the size of the air gap from 5 μm to 10 μm.
The calculation results are shown in the state where the distance is changed by 1 μm at a time, and the calculation results are indicated by the solid curve.
In FIG. 8, black circles indicate values obtained by actually measuring the relationship between the potential difference and the 0 G output when the air gap size is 6 μm. Note that this measurement was performed by applying a plurality of levels of potential differences between the semiconductor sensor chip 21 and the pedestal 26 using the constant voltage power supply 36 and the variable voltage power supply 37 as shown in FIG.

As is apparent from FIG. 8, the calculation results almost agree with the actually measured values. In short, in order to reduce the above-mentioned electrostatic attractive force F so that the fluctuation of the 0G output falls within the allowable range, it is necessary to increase the air gap dimension between the weight 23 and the pedestal 26 to some extent. In this embodiment, the air gap dimension is set to 7 μm or more based on the characteristics as shown in FIG. 8 and the fact that the designed potential difference applied between the semiconductor sensor chip 21 and the pedestal 26 is about 3.5 V. , Preferably 8 μm or more (10 μm or more when particularly strict specifications are required)
Is set to

In short, as a result of setting the air gap dimensions as described above, it is possible to prevent the output characteristics from deteriorating due to the vibration of the weight portion 23, and also to prevent the output characteristics from deteriorating due to the electrostatic attraction generated inside. At the same time, prevention can be achieved, and stable output characteristics can be obtained.

In this case, the size of the air gap between the weight 23 and the pedestal 26 is controlled by a plurality of resin beads 28 interposed between the pedestal 26 and the frame 22 on the semiconductor sensor chip 21 side. As a result, the gap size can be controlled strictly and easily,
This can contribute to stabilization of output characteristics.

Further, according to the present embodiment in which the vibration of the weight portion 23 is damped by air damping, the oil for damping as in the conventional configuration is not required, so that the structure can be simplified. Moreover, the semiconductor sensor chip 2
1 and the pedestal 26 supporting the same have the same thermal expansion coefficient, so that distortion caused by thermal stress generated between the semiconductor sensor chip 21 and the pedestal 26 can be suppressed, and the conventional semiconductor sensor chip As described above, a frame having a double structure is not required, and the overall size can be reduced.

The space between the pedestal 26 and the frame 22 of the semiconductor sensor chip 21 supported by the pedestal 26 has a low elastic modulus (500 MPa).
a), the stress acting on the semiconductor sensor chip side 21 from the pedestal 26 side can be reduced, and the output characteristics can be further stabilized. In this case, the resin beads 28 functioning as spacers are mixed in the flexible adhesive 29, and the resin beads 28 having a relatively low elastic modulus (10 GPa or less) are used. Therefore, there is no possibility that the presence of the resin beads 28 hinders the stress relaxation function of the flexible adhesive 29.

When external static electricity acts on the semiconductor sensor chip 21, a large electrostatic attraction is generated between the weight 23 and the pedestal 26, which may cause an extreme fluctuation of the 0G output. In contrast, in the present embodiment,
Since the electrostatic shield 34 for removing the influence of static electricity on the semiconductor sensor chip 21 is provided on the entire bottom surface of the housing 27, the situation where the external static electricity affects the semiconductor sensor chip 21 is effectively reduced. , And can contribute to stabilization of the 0G output.

FIG. 10 shows the relationship between the amount of external static electricity and 0 G
An experimental result showing how the relationship with the output changes depending on the presence or absence of the electrostatic shield 34 is shown. It is understood from FIG. 10 that when the electrostatic shield 34 is provided, a situation in which the 0G output fluctuates extremely due to the influence of external static electricity can be reliably prevented.

In addition, at least the semiconductor sensor chip 2
1 and the pedestal 26 supporting the same, a burn-in process of exposing the semiconductor sensor chip 21 to a predetermined temperature atmosphere for a predetermined time or more while applying a predetermined voltage to the semiconductor sensor chip 21 is performed. Variations can be suppressed, and as a result, the weight 23 and the pedestal 2
In combination with the configuration in which the size of the air gap between the six is set as described above, the yield in the manufacturing process is improved.

FIG. 11 shows the result of sampling the fluctuation state of the 0 G output of a large number of G sensors 25 subjected to the burn-in process. FIG. It can be seen that the fluctuation amount is small. When the fluctuation amount of the 0 G output is allowed to be, for example, ± 0.1 G, the yield is improved to nearly 99%, and it is possible to cope with more severe specifications. It can be seen that the yield is improved to 92% or more when the tolerance is up to ± 0.05G.

(Second Embodiment) FIGS. 12 to 14 show a second embodiment of the present invention. Only the portions different from the first embodiment will be described below. In FIG. 13, four bonding pads 22a provided on the semiconductor sensor chip 21 side (see FIG. 3 in the first embodiment).
Are connected by bonding wires 38 to four bonding pads 32 a provided on the amplifier circuit 32 side. In this case, of the bonding pad 32a on the side of the amplifier circuit 32, the power supply terminal of the semiconductor sensor chip 21+
To supply the power supply voltage to Vcc (see FIG. 3),
As shown in FIG. 12, a bonding wire 39 (corresponding to a voltage applying means in the present invention) is connected to a bonding pad 26a formed on the pedestal 26 of the semiconductor sensor chip 21.

As a result of this configuration, a voltage at the same level as the power supply voltage applied to the semiconductor sensor chip 21 is applied to the pedestal 26 through the bonding wires 39. For this reason, the potentials of the pedestal 26 and the semiconductor sensor chip 21 can be forcibly maintained to be at the same level, so that adverse effects due to external static electricity can be eliminated. become able to.

FIG. 14 shows the amount of external static electricity and 0 G
An experimental result showing how the relationship with the output changes depending on the presence or absence of the bonding wire 39 is shown. FIG. 14 shows that when the bonding wire 39 is provided, it is possible to reliably prevent a situation in which the 0G output fluctuates extremely due to the influence of static electricity from the outside.

In this embodiment, the electrostatic shield 34 is additionally provided to ensure the elimination of the adverse effects of external static electricity. The electric shield 34 may be provided as needed.

(Third Embodiment) FIGS. 15 and 16 show a third embodiment of the present invention in which the first embodiment is modified, and only different portions will be described below. In the present embodiment, for example, four convex portions 26b are integrally formed on the surface of the base 26 facing the weight portion 23 so that the convex portions 26b are formed integrally with the weight portion 23 and the pedestal 2.
6 and is characterized in that excessive deformation of the weight portion 23 is restricted by the convex portion 26b (in FIG. 16, the air gap is enlarged for convenience of explanation). State).

In this case, the projection 26b is, for example,
This is formed by performing etching (anisotropic etching, electrochemical etching, or the like) on the beam, and in the present embodiment, it is configured to be symmetrically disposed at a position corresponding to the four beam portions 24.

According to the present embodiment having such a configuration,
When the weight portion 23 is greatly deformed, the weight portion 23 comes into contact with the convex portion 26b, whereby further deformation of the weight portion 23 is regulated. As a result, even when a large acceleration acts on the semiconductor sensor chip 21, a situation in which an excessive torsional force acts on the beam portion 24 is prevented beforehand, and the beam portion 24 is not likely to be damaged. As a result, the reliability as a product is increased.

In the third embodiment, the projection 26b has four
Although at least one protruding portion may be provided, and the protruding portion 26b is formed integrally with the pedestal 26, the protruding portion made of another material is bonded by bonding or the like. It is good also as a structure provided. Further, a configuration in which a convex portion is provided on the weight portion 23 side in a state of facing the pedestal 26 may be adopted.

(Fourth Embodiment) FIG. 17 shows the third embodiment.
A fourth embodiment of the present invention in which the embodiment is further modified is shown, and only different portions will be described below.
In the fourth embodiment, the management of the size of the air gap between the weight portion 23 and the pedestal 26 is the same as that of the resin beads 2 in the first embodiment.
The feature is that a plurality of projections 26c (corresponding to spacers) integrally formed on the pedestal 26 side are used in place of the configuration of FIG. In this case, the protrusion 26c is
6 is formed by etching. However, actually, as shown in FIG.
Since b is formed by changing the shape such as the height, etching of a different step is performed for forming both.

According to the present embodiment having such a configuration,
Since the dimension of the air gap between the weight 23 and the pedestal 26 is controlled by the projection 26c formed integrally with the pedestal 26, there is an advantage that the resin beads 28 (see FIG. 1) are not required.

In the fourth embodiment, the protruding portion 26c is formed on the pedestal 26 side. However, a protruding portion functioning as a spacer may be formed on the frame 22 side of the semiconductor sensor chip 21. . In addition, the protrusion 26b may be provided as needed.

(Fifth Embodiment) By the way, in the first to fourth embodiments described above, in order to realize the miniaturization of the whole sensor, the frame formed by supporting the weight 23 via the beam 24. Although the structure in which the body 22 is bonded to the pedestal 26 (the structure in which the double-structured frame is eliminated) is employed, extremely high detection accuracy is required in order to cope with an application such as a side slip prevention device during turning of an automobile. In such a case, it is desirable to consider adopting a frame having a double structure.

FIGS. 18 to 25 show a fifth embodiment of the present invention employing the above-described double frame structure, which will be described below. 18 shows a cross-sectional structure of a main part of the semiconductor acceleration sensor, FIG. 19 shows a plan shape of a semiconductor sensor chip which is a core of the semiconductor acceleration sensor, and FIG. 20 shows a bridge circuit formed on the semiconductor sensor chip. Is schematically shown.

In FIG. 19, the semiconductor sensor chip 41
Is formed by electrochemically etching a material having a large piezoresistance coefficient, such as a silicon single crystal substrate, inside a rectangular auxiliary frame 42 having a size of about 7 × 7 mm to 8 × 8 mm. The U-shaped frame 43 is supported in a cantilever manner via the arm portion 44, and inside the frame 43,
The weight 45 is supported in a doubly supported manner via four beams 46 symmetrically arranged.

Each of the beam portions 46 is formed by using, for example, an epitaxial layer portion formed on a silicon single crystal substrate, as in the first embodiment. For example, two resistive elements (indicated by reference numerals R11 to R14 and R21 to R24 in FIG. 20) are formed, and acceleration is detected using a bridge circuit formed by these resistive elements. Configuration.

More specifically, as shown in FIG. 20, the resistance elements R11, R12, R13,
Each pair of R14, R21, R22, and R23, R24 is provided in a positional relationship such that one of the pair is contracted and deformed in accordance with the displacement of the weight 45, and the other is expanded and deformed. Then, two series resistors (R11 and R21, R13 and R23, R
12 and R22, R14 and R24), and a pair of input terminals T1 and T2 of the bridge circuit.
Further, a pair of output terminals T3 and T4 are connected to four bonding pads 42a formed on the auxiliary frame 42 via a thin-film wiring pattern.

In this case, for example, the weight of the weight 45 is set to about 6 mg so that the acceleration up to about ± 1 G can be detected by utilizing the piezoresistance effect of the resistance element. The thickness, width, and length of the beam 46 are 3 to 6 μm, 220 to 280 μm, and 470, respectively.
It is set to about 530 μm. However, these weights and dimensions are merely examples, and when the weight of the weight 45 is changed, the dimensions of the thickness, width, and length of the beam 46 are naturally changed. Will be done.

In FIG. 18, the semiconductor acceleration sensor 47
(Hereinafter abbreviated as G sensor) is configured by supporting the semiconductor sensor chip 41 on a pedestal 48 via an auxiliary frame 42 and bonding the pedestal 48 on a thick film substrate 49. The pedestal 48 is formed of a material having a thermal expansion coefficient equivalent to that of the semiconductor sensor chip 41, specifically, a silicon substrate of the same material.

In this case, a flexible adhesive 31 containing a plurality of resin beads 30 is used for bonding between the pedestal 48 and the thick film substrate 49. Although not specifically shown, the semiconductor sensor chip 4 is provided on the thick film substrate 49.
1 is provided with an amplifier circuit having a function of supplying a power supply voltage to the amplifier 1 and amplifying a detection output from the sensor chip 41, an adjustment circuit for adjusting the level of the power supply voltage applied to the amplifier circuit, and the like. Further, the thick film substrate 49 on which the semiconductor sensor chip 41 and the amplifier circuit and the like are mounted as described above is housed in, for example, a metal case having terminals for input and output.

In this case, the space between the auxiliary frame 42 and the pedestal 48 is bonded by a flexible adhesive 29 containing a plurality of resin beads 28 as spacers as in the first embodiment. In the bonded state, the weight 45 of the semiconductor sensor chip 41 and the pedestal 48 are sufficiently close to each other so that the weight 45 is air-damped. Specifically, resin beads 2
By selecting the diameter of 8, the size of the air gap between the weight portion 45 and the pedestal 48 is set in the range of 10 to 22 μm.

When the air gap dimension between the weight 45 and the pedestal 48 is d and the bottom area of the weight 45 is S, the relationship between the air gap dimension d and the bottom area S is as follows.
It is set to a value that satisfies the following equation.

[0089]

Equation 3] According to the fifth embodiment in which ^{0.01 ≦ S / d 2 ≦ 0.05} ...... above, it is possible to obtain the operation and effect as described below.

In this embodiment, the size of the air gap between the weight 45 of the semiconductor sensor chip 41 and the pedestal 48 supporting the sensor chip 41 is set to 10 to 22 μm.
The vibration of the weight 45 is attenuated by air damping between the weight 45 and the pedestal 48 by setting the distance in the range.

The inventor of the present application has proposed a G sensor 47 having a double frame structure as in this embodiment, that is, the auxiliary frame 42.
And a frame 43 supported in a cantilever manner via an arm portion 44 inside thereof, and four frame members 45 provided inside the frame 43 so as to support the weight 45 in a double-supported manner. A G sensor 4 including a beam part 46 and a semiconductor sensor chip 41 capable of detecting an acceleration up to about ± 1 G by utilizing a piezoresistance effect of a resistance element formed in the beam part 46.
7, the vibration of the weight 45 and the weight 45 and the pedestal 4
The relationship with the size of the air gap between 8 was determined by experiments. This experiment is for examining the amount of vibration attenuation (air damping characteristic) in a state where vibration is applied to the weight 45 with respect to the G sensor 47, and the experimental data is shown in FIG. .

As is apparent from FIG. 22, the weight 4
It is understood that if the size of the air gap between the base 5 and the pedestal 48 is about 22 μm or less, a sufficient air damping effect can be obtained in a relatively strict specification in which the allowable range of vibration attenuation is about 6 dB or less. Thus, it is possible to prevent the output characteristics of the G sensor 47 from deteriorating due to the vibration of the weight 45.

The reason why the lower limit of the size of the air gap between the weight 45 and the pedestal 48 in this embodiment is set to 10 μm is as follows. That is, the inventor of the present application states that the 0 G output of the G sensor 47 is
In order to search for the phenomenon of variation due to electrostatic attraction acting between them, the air gap dimension between the weight 45 and the pedestal 48 is set to 0.
Work to confirm the effect on G output by calculation and experiment was performed.

FIG. 21 shows the relationship between the potential difference between the semiconductor sensor chip 41 and the pedestal 48 and the variation of the 0 G output.
It shows the result of calculation in the state of changing by μm,
The result of the calculation is shown by a solid curve. Also,
In FIG. 21, black circles indicate values obtained by actually measuring the relationship between the potential difference and the 0 G output when the air gap size is 16 μm.

As is apparent from FIG. 21, the calculation results almost agree with the actually measured values. As described in the first embodiment, in order to reduce the electrostatic attraction acting between the weight 45 and the pedestal 48 so that the fluctuation of the 0G output falls within an allowable range, the weight 45 is required. In addition, it is necessary to increase the size of the air gap between the pedestals 48 to some extent. In this embodiment, based on the characteristics as shown in FIG. 21 and the fact that the designed potential difference applied between the semiconductor sensor chip 41 and the pedestal 48 is about 3.5 V, the variation allowable range of the 0G output is relatively small. The air gap dimension is set to be 10 μm or more when the voltage is 0.05 V or less which is a strict specification.

In short, as a result of setting the air gap dimensions as described above, it is possible to prevent the output characteristics from deteriorating due to the vibration of the weight portion 45, and to prevent the output characteristics from deteriorating due to the electrostatic attraction generated inside. At the same time, it is possible to prevent the vehicle from slipping, and to obtain a stable output characteristic capable of coping with severe specifications such as a device for preventing a skid during turning of a vehicle.

Also, actually, the weight 45 and the pedestal 48
It is desirable that the size of the air gap between the air gaps is determined in consideration of the size of the bottom area of the weight portion 45 which affects the air damping characteristic. In this embodiment, as shown in the above equation, When the dimension is d and the bottom area is S, the value of S / d ² is set to be in the range of 0.01 to 0.05, thereby stabilizing the 0 G output.

The reason why the maximum value of S / d ² is set to 0.05 and the minimum value of S / d ² is set to 0.01 in the present embodiment is as follows. That is, the inventor of the present application has found that the value of S / d ² is 0 G
In order to confirm the effect on the output, as shown in FIG. 23, the relationship between the potential difference between the semiconductor sensor chip 41 and the pedestal 48 and the variation of the 0G output is determined by the value of S / d ² (in the example of FIG. 0.01 to 0.07).

As is apparent from FIG. 23, in order for the fluctuation of the 0G output to be within the allowable range, S / S
the value of d ² which is necessary to some extent. That is, the characteristics as shown in FIG.
And the designed potential difference applied between the pedestal 48 and 3.5 V
If the allowable range of the 0G output is 0.05 V or less, which is a relatively severe specification, it is necessary to set the value of S / d ² to 0.05 or less. Become.

Further, the inventor of the present application obtained the relationship between the vibration of the weight 45 and the value of S / d ^{2 for} the G sensor 47 by experiments. This experiment is for examining the amount of vibration attenuation in a state in which vibration is applied to the weight 45 with respect to the G sensor 47, and the experimental data is shown in FIG.

As is apparent from FIG. 24, S / d ²
Is 0.01 or more, a sufficient air damping effect can be obtained in a relatively strict specification in which the allowable range of the vibration attenuation is about 6 dB or less.

Incidentally, the semiconductor sensor chip 41 used in the fifth embodiment has basically the same shape as the semiconductor sensor chip of the conventional configuration (indicated by reference numeral "1" in FIG. 35). In this case, in the present embodiment, the semiconductor sensor chip 41 is replaced with a pedestal 48 having a thermal expansion coefficient equivalent to this.
Since the semiconductor sensor chip 1 is bonded to the upper surface with the flexible adhesive 29 and oil-less air damping is performed, the semiconductor sensor chip 1 is anodically bonded to the glass pedestal 8 and oil damping is performed. The temperature characteristics are better than that.

That is, FIG. 25 shows a conventional G sensor (with anodic bonding and damping oil), a G sensor (with anodic bonding and no damping oil) that performs air damping in a conventional product, The result of measuring the bending of the temperature characteristic of the sensor output is shown for a plurality of samples of the G sensor 47 according to the example.

FIG. 25 shows the distribution of the measurement results (the center value is represented by black circles). As can be understood from FIG. 25, according to the G sensor 47 of the present embodiment, the above-mentioned bending of the temperature characteristic is obtained. 0.6 which is a relatively strict specification
%, The specification sufficiently satisfies the specification.

The G sensor 47 according to the fifth embodiment can be provided with the same electrostatic shield as that of the first embodiment. Further, the configuration as in the above-described second embodiment (the configuration in which the potentials of the pedestal 48 and the semiconductor sensor chip 41 are forcibly held at the same level), the configuration as in the third embodiment (the weight 45 A configuration in which a convex portion for restricting excessive deformation is provided), and a configuration as in the fourth embodiment (a configuration in which a protrusion is provided instead of the resin bead 28 as a spacer) can be applied.

(Sixth Embodiment) FIGS. 26 to 31 show a sixth embodiment of the present invention. Only parts different from the first embodiment will be described below. FIG. 26 shows the appearance of the semiconductor acceleration sensor, and FIG.
2 shows a cross-sectional structure taken along line -A. 26 and 27, the semiconductor acceleration sensor 50 (hereinafter referred to as G
A semiconductor sensor chip 21 having the same configuration as that of the first embodiment is supported on a pedestal 26 via a frame 22 and an integrated body of the semiconductor sensor chip 21 and the pedestal 26 is connected to a housing 27. Is formed by adhering on a ceramic substrate 27b.
A flexible adhesive 31 containing a plurality of resin beads 30 is used for this bonding.

In the G sensor 50 according to the present embodiment,
The frame 22 and the pedestal 26 are bonded together by a bonding material 51 as a support member. The bonding material 51 is formed by adding a plurality of spacer resin beads 51b (for example, about 8 μm in diameter) to the flexible adhesive 51a by, for example, 0.1 wt.
%. in this case,
At least one of the plurality of resin beads 51b is
The surface is formed as conductive beads, for example, plated (coated) with a conductive material such as gold, so that the resistance value via the bonding material 51 between the semiconductor sensor chip 21 and the pedestal 26 becomes 10 ¹⁰ Ω or less. You have set.

Here, FIG. 28 shows a case where the resistance value R1 of the bonding material 51 when the number of the conductive beads included in the group of the resin beads 51b is zero and the case where the entire group of the resin beads 51b are the conductive beads. And the resistance value R2 of the bonding material 51 in the general use temperature range of the G sensor 50 (−30 ° C.
85 ° C.). However, FIG.
The characteristics are that the blending amount of the resin beads 51b is 0.1 wt%,
The resistance value of the resin bead 51b not plated with gold is 2.9 × 10 ¹² Ω,
This is an example in the case where the resistance value of (conductive beads) is several tens Ω.

According to the evaluation results shown in FIG. 28, the resistance value R2 of the bonding material 51 when the entire resin bead 51b group is a conductive bead is about 100Ω.
Actually, the resistance value between the semiconductor sensor chip 21 and the pedestal 26 in the state of being joined by the joining material 51 is 10 ¹⁰
What is necessary is just to determine the ratio of the conductive beads in the resin beads 51b so as to be Ω or less. However, when resin beads plated with gold are used as in this embodiment,
When at least one conductive bead of the resin beads 51b electrically connects the semiconductor sensor chip 21 and the pedestal 26, the resistance value via the bonding material 51 between the semiconductor sensor chip 21 and the pedestal 26 is obtained. Is 10 ¹⁰ Ω or less.

The flexible adhesive 51 used in this embodiment is used.
It is desirable that a has an elastic modulus of 500 MPa or less. For example, silicon resin, urethane resin, acrylic resin, polyamide resin, polyimide resin, flexible epoxy resin, or the like is used. The resin beads 51b preferably have an elastic modulus of 10 GPa or less. For this reason, polydinivir benzene resin, silicone resin, urethane resin, acrylic resin, polyimide resin, flexible epoxy resin, vinyl resin, etc. Use.

The amount of the resin beads 51b to be mixed into the bonding material 51 is determined in consideration of the following circumstances. In other words, the present inventors prepared various samples of the G sensor 50 from those in which the resin beads 51b were not added to the bonding material 51 to those in which the resin beads 51b were added at about 0.55 wt%, The test was performed. This low-temperature storage test is a one-cycle test consisting of measuring the sensitivity S0 of a sample at room temperature, leaving it in an atmosphere at -40 ° C for a predetermined time, and then returning to room temperature and measuring the sensitivity S1. It is set as.

FIG. 29 shows the sensitivity variation ΔS (= (S0−S1) × 100 / S0 (%)) before and after the low-temperature storage test.
This shows the result of measurement in a state where the amount of the resin beads 51b mixed into the bonding material 51 is changed. From this result, when the sensitivity variation ΔS is set to about ± 2%, which is a range in which the acceleration can be accurately detected in the acceleration detection region up to about ± 1 G, the blending amount of the resin beads 51b is set to 0.1 wt.
%. Note that the lower limit of the blending amount is theoretically a value such that at least three resin beads 51b are arranged at an appropriate interval in the bonding surface in order to secure a space between the weight 23 and the pedestal 26. However, from the relationship with the actual process capability, it has been found that an appropriate lower limit is about 0.03 wt% as an empirical value.

According to the present embodiment having the above-described structure, the same voltage as the power supply voltage applied to the semiconductor sensor chip 21 is applied to the pedestal 26 through the conductive beads in the resin beads 51b. Will be
The potential difference between the semiconductor sensor chip 21 and the pedestal 26 is reduced.

That is, when this potential difference is V, the following equation is obtained.

(Equation 4) Here, V0 is a potential difference at the initial stage of voltage application, C is a capacitance between the semiconductor sensor chip 21 and the pedestal 26, R is a resistance value between the semiconductor sensor chip 21 and the pedestal 26, and T is a time constant.

From the above equation, it can be seen that the potential difference V decreases as the resistance value R between the semiconductor sensor chip 21 and the pedestal 26 decreases. In the present embodiment, the resistance between the semiconductor sensor chip 21 and the pedestal 26 is configured to be 10 ¹⁰ Ω or less.
Since the potential difference generated between the semiconductor sensor chip 21 and the pedestal 26 becomes sufficiently small, the electrostatic attraction generated between the weight 23 and the pedestal 26 also becomes small. As a result, it is possible to prevent output characteristics from deteriorating due to electrostatic attraction generated inside the G sensor 50, and to obtain stable output characteristics. In addition, in order to obtain such an effect, it is only necessary to use the bonding material 51 having predetermined electrical characteristics, so that the structure can be simplified.

FIG. 30 shows that the semiconductor sensor chip 21 and the pedestal 26 are insulated (resin beads 51).
(equivalent to the case where the number of the conductive beads included in the group b is zero)).
An experimental result of measuring the amount of change in the sensor output when different levels of voltage are applied to the pedestal 26 in the state where the above voltage is applied is shown. From this result, it can be seen that when the potential of the pedestal 26 becomes the same as that of the semiconductor sensor chip 21, the fluctuation of the sensor output becomes minimum.

FIG. 31 shows the result of sampling the fluctuation state of the 0 G output of a large number of G sensors 50 that have been subjected to burn-in processing. FIG. It can be seen that the fluctuation amount of the output is small, and the yield is improved to 97% or more even in a strict specification in which the fluctuation amount of the 0 G output is allowed only to ± 0.05 G, for example.

When the structure as in the sixth embodiment is adopted, when the semiconductor sensor chip 21 and the pedestal 26 are bonded with the bonding material 51, the compressive force acts on the bonding material 51. It is desirable that the electrical connection between the semiconductor sensor chip 21 and the pedestal 26 by the conductive beads in the resin beads 51b be ensured.

Further, in the sixth embodiment, the conductive beads in which the surface of the resin beads is plated with gold are used. However, the conductive beads in which the conductive material such as silver is plated (coated) on the surface of the resin beads are used. A configuration using beads or conductive beads made entirely of metal may be used.
As the bonding material 51, resin beads 5 are added to a flexible adhesive 51a.
1b was used, but a bonding material formed by combining an adhesive and a plurality of beads (including at least one conductive bead) may be used.

Instead of the bonding material 51, a bonding material made of a conductive adhesive for bonding the semiconductor sensor chip 21 and the pedestal 26 may be used. Further, instead of the bonding material 51, a bonding material composed of an adhesive for bonding the semiconductor sensor chip 21 and the pedestal 26 and carbon powder mixed therein may be used. Further, instead of the bonding material 51, a bonding material made of a conductive adhesive sheet for bonding the semiconductor sensor chip 21 and the pedestal 26 may be used.

(Seventh Embodiment) FIG. 32 shows a seventh embodiment of the present invention in which the sixth embodiment is modified, and only different portions will be described below. In the seventh embodiment, as a supporting member for supporting the semiconductor sensor chip 21 on the pedestal 26, for example, a plurality of protrusions 52a integrally formed on the pedestal 26 side instead of the bonding material 51 in the sixth embodiment. And a support member 52 made of a conductive adhesive 52b for holding the semiconductor sensor chip 21 and the pedestal 26 in contact with each other via the projection 52a. In this case, the protrusion 52a is formed by etching the pedestal 26. It is desirable to use a conductive adhesive having a modulus of elasticity of 500 MPa or less as the conductive adhesive 52b.

According to the present embodiment having such a structure,
Since a voltage of the same level as the power supply voltage applied to the semiconductor sensor chip 21 is applied to the pedestal 26 through the protrusion 52a and the conductive adhesive 52b, the voltage is generated between the semiconductor sensor chip 21 and the pedestal 26. Therefore, the same effect as in the sixth embodiment can be obtained. In particular, according to the present embodiment, the weight 23 and the pedestal 2 on the semiconductor sensor chip 21 side
There is an advantage that the dimensional control of the air gap between the six can be performed by the protrusion 26c integrally formed on the pedestal 26 side.

In the seventh embodiment, the projection 26c is formed on the pedestal 26 side. However, the projection may be formed on the frame 22 side of the semiconductor sensor chip 21. In addition, if the electrical connection between the semiconductor sensor chip 21 and the pedestal 26 via the projection 52a is assured, a normal adhesive can be used instead of the conductive adhesive 52a. .

(Eighth Embodiment) FIGS. 33 and 34 show an eighth embodiment of the present invention in which the sixth embodiment is further modified, and only different portions will be described below. . The eighth embodiment is characterized in that the semiconductor sensor chip 21 and the pedestal 26 are integrally formed from the same material (for example, a silicon single crystal substrate).
FIG. 33 shows an appearance of the semiconductor acceleration sensor, and FIG. 34 shows a cross-sectional structure taken along a line BB of FIG.

In FIGS. 33 and 34, when manufacturing the sensor unit 53 in which the semiconductor sensor chip 21 and the pedestal 26 are integrated, impurity concentration-dependent etching is used. In this case, the high concentration (10 ¹⁹ / c) is applied to the portion to be etched in the silicon single crystal substrate material.
m ³ or more) is formed by ^{P +} or ^{N +} region buried diffusion or ion implantation, HF-HNO3 -CH3 COO
By selectively etching only the high concentration region with an H-based etchant, the semiconductor sensor chip 21
And a pedestal 26 are integrally formed to form a sensor unit 53.

According to the present embodiment having such a configuration,
Since the semiconductor sensor chip 21 and the pedestal 26 are integrally formed of the same material, the potential difference generated between the semiconductor sensor chip 21 and the pedestal 26 is sufficiently small, and the static electricity generated between the weight 23 and the pedestal 26 is reduced. The attraction is also significantly reduced. As a result, also in the present embodiment, it is possible to prevent the output characteristics from deteriorating due to electrostatic attraction generated inside, and to obtain stable output characteristics. According to this means, the bonding material 51 as in the sixth embodiment is not required, and the number of parts can be reduced.

(Other Embodiments) In addition, the present invention is not limited to the above-described embodiment, and the following modifications or extensions are possible. The semiconductor sensor chip 21 or 41 is formed of a silicon single crystal substrate, but may be formed of another material having a large piezoresistance coefficient. The material of the housing 27 and the lid 35 is not limited to ceramic, but may be formed of an insulating material such as glass or a metal. The electrostatic shield 34 is provided on the entire bottom surface of the housing 27. However, the electrostatic shield 34 is also provided on the cover 35, only on the portion corresponding to the bottom surface of the semiconductor sensor chip 21, or on the sensor chip 21.
Various configurations can be implemented, such as a configuration in which it is provided on almost the entire position covering the.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part showing a first embodiment of the present invention.

FIG. 2 is a plan view of a semiconductor sensor chip.

FIG. 3 is a diagram schematically showing a configuration of a bridge circuit formed on the semiconductor sensor chip.

FIG. 4 is a connection diagram of a bridge circuit.

FIG. 5 is an overall vertical sectional view.

FIG. 6 is an overall plan view with the lid removed.

FIG. 7 is a vertical cross-sectional view of a main part for explaining operation.

FIG. 8 shows a potential difference between the semiconductor sensor chip and the base and 0G.
Characteristic diagram showing the relationship with the output using the air gap dimension as a parameter

FIG. 9 is a diagram showing air damping characteristics using an air gap dimension as a parameter.

FIG. 10 is a characteristic diagram showing the relationship between the amount of external static electricity and 0 G output.

FIG. 11 is a diagram illustrating a result of sampling a fluctuation state of 0G output after performing a burn-in process;

FIG. 12 is a view corresponding to FIG. 5, showing a second embodiment of the present invention.

FIG. 13 is a diagram corresponding to FIG. 6;

FIG. 14 is a diagram corresponding to FIG. 10;

FIG. 15 is a plan view of a semiconductor sensor chip and a base according to a third embodiment of the present invention.

FIG. 16 is a longitudinal sectional view of a semiconductor sensor chip and a pedestal portion.

FIG. 17 is a longitudinal sectional view of a semiconductor sensor chip and a pedestal portion showing a fourth embodiment of the present invention.

FIG. 18 is a view corresponding to FIG. 1, showing a fifth embodiment of the present invention.

FIG. 19 is a diagram corresponding to FIG. 2;

FIG. 20 is a diagram corresponding to FIG. 3;

FIG. 21 is a diagram corresponding to FIG. 8;

FIG. 22 is a diagram corresponding to FIG. 9;

FIG. 23 shows a potential difference between semiconductor sensor chip and pedestal and zero.
A characteristic diagram showing the relationship with the G output using the value of S / d ² (S is the bottom area of the weight portion, d is the air gap dimension) as a parameter.

FIG. 24 is a diagram showing the air damping characteristic using the value of S / d ² as a parameter.

FIG. 25 is a diagram showing a result of measuring a bending of a temperature characteristic of a sensor output.

FIG. 26 is a perspective view of a main part showing a sixth embodiment of the present invention.

FIG. 27 is a sectional view taken along line AA of FIG. 26;

FIG. 28 is a characteristic diagram showing evaluation results of resistance values of bonding materials.

FIG. 29 is a characteristic diagram showing the result of measuring the relationship between the blending amount of resin beads and sensitivity fluctuation.

FIG. 30 is a characteristic diagram showing a result of measuring a fluctuation amount of a sensor output with respect to a sample in which a semiconductor sensor chip and a base are insulated from each other

FIG. 31 is a diagram showing a result of sampling a fluctuation state of 0G output after performing burn-in processing;

FIG. 32 is a longitudinal sectional view showing a seventh embodiment of the present invention.

FIG. 33 is a perspective view of a main part showing an eighth embodiment of the present invention.

FIG. 34 is a sectional view taken along line BB of FIG. 33;

FIG. 35 is a plan view of a semiconductor sensor chip showing a conventional configuration.

FIG. 36 is a longitudinal sectional view of the entire semiconductor acceleration sensor having the conventional configuration.

[Explanation of symbols]

21: semiconductor sensor chip, 22: frame, 23: weight, 24: beam, 25: semiconductor acceleration sensor, 26: base, 26b: convex, 26c: protrusion (spacer), 27
... housing, 28 ... resin beads (spacer), 29 ...
Flexible adhesive, 34: electrostatic shield, 35: lid, 39
... bonding wire (voltage applying means), 41 ... semiconductor sensor chip, 42 ... auxiliary frame, 43 ... frame body, 44 ... arm part, 45 ... weight part, 46 ... beam part, 47 ... semiconductor acceleration sensor, 48 ... pedestal 49, thick film substrate, 50, semiconductor acceleration sensor, 51, bonding material (supporting member), 51a, flexible adhesive, 51b, resin bead, 52, support member, 52
a: Projection, 52b: Conductive adhesive, 53: Sensor unit.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yasuki Shimoyama 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Within Nippon Denso Co., Ltd. (72) Inventor Tomohito Kamoda 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Nippon Electric (72) Inventor Norio Kitao 1-1-1, Showa-cho, Kariya-shi, Aichi, Japan

Claims (24)

[Claims] A weight portion supported via a beam portion,
A semiconductor acceleration sensor including a semiconductor sensor chip configured to detect an acceleration up to about ± 1 G using a piezoresistive effect of a resistance element formed in the beam portion, wherein the semiconductor sensor chip is equivalent to the semiconductor sensor chip. While supported by a pedestal formed of a material having a thermal expansion coefficient of
The weight portion is arranged close to the pedestal to perform air damping of the weight portion, and a dimension of an air gap between the weight portion and the pedestal is set to 7 μm or more. Semiconductor acceleration sensor. 2. The semiconductor acceleration sensor according to claim 1, wherein a size of an air gap between the weight portion and the pedestal is set in a range of 7 to 15 μm. 3. The relationship between an air gap dimension d between the weight portion and the pedestal and a bottom area S of the weight portion is set to a value satisfying the following expression. Semiconductor acceleration sensor. ## EQU1 ## 0.01 ≦ S / d ² ≦ 0.05 4. A frame for supporting the weight portion via the beam portion, wherein the pedestal and the frame are bonded with a flexible adhesive. The semiconductor acceleration sensor according to any one of claims 1 to 3. 5. An auxiliary frame for supporting said weight portion via said beam portion, and a frame for supporting said auxiliary frame in a cantilever manner via an arm portion, wherein a space between said pedestal and said frame is provided. 4. The semiconductor acceleration sensor according to claim 1, wherein the semiconductor acceleration sensor is configured to be adhered by a flexible adhesive. 6. A spacer is provided between the pedestal and the frame,
6. The semiconductor acceleration sensor according to claim 1, wherein the dimension of the air gap is controlled by the spacer. 7. The semiconductor acceleration sensor according to claim 6, wherein the spacer is formed by a plurality of resin beads mixed with a flexible adhesive for bonding between the pedestal and the frame. 8. The semiconductor acceleration sensor according to claim 6, wherein the spacer is formed by a plurality of protrusions integrally formed on the pedestal side or the frame body side. 9. A voltage applying means for applying a voltage of the same level as a power supply voltage applied to the semiconductor sensor chip to the pedestal is provided. Semiconductor acceleration sensor. 10. A structure in which at least one of the weight portion and the pedestal is provided with at least one convex portion positioned in a gap between the weight portion and the pedestal, and the convex portion restricts excessive deformation of the weight portion. The semiconductor acceleration sensor according to claim 1, wherein: 11. A burn-in process for exposing said integrated body to a predetermined temperature atmosphere for a predetermined time or more for said semiconductor sensor chip and a pedestal supporting said semiconductor sensor chip. A semiconductor acceleration sensor according to any one of the above. 12. It has a weight portion supported via a beam portion, and is configured to detect an acceleration up to about ± 1 G using a piezoresistance effect of a resistance element formed on the beam portion. A semiconductor acceleration sensor provided with a semiconductor sensor chip, comprising: a pedestal for supporting the semiconductor sensor chip; generating a potential difference between the semiconductor sensor chip and the pedestal as a support member for supporting the semiconductor sensor chip on the pedestal. A semiconductor acceleration sensor characterized by using a device having a function of suppressing noise. 13. The semiconductor acceleration sensor according to claim 12, wherein a resistance value between said semiconductor sensor chip and said base via said supporting member is set to 10 ¹⁰ Ω or less. 14. The semiconductor acceleration sensor according to claim 12, wherein the support member is a conductive adhesive for bonding the semiconductor sensor chip and the pedestal. 15. The support member includes an adhesive for bonding the semiconductor sensor chip and the pedestal, and a plurality of beads mixed therein, and at least one of the plurality of beads is used. 14. The method according to claim 12, wherein the conductive beads are formed of conductive beads.
The semiconductor acceleration sensor as described in the above. 16. The semiconductor acceleration sensor according to claim 15, wherein the conductive beads are formed by coating a surface of a resin bead with a conductive material. 17. The support member is composed of a flexible adhesive for adhering the semiconductor sensor chip and the pedestal, and a plurality of resin beads mixed with the flexible adhesive. 14. The semiconductor acceleration sensor according to claim 12, wherein at least one of the semiconductor acceleration sensors is formed by conductive beads coated with a conductive material. 18. The semiconductor device according to claim 12, wherein the support member is made of an adhesive for bonding the semiconductor sensor chip and the pedestal, and carbon powder mixed with the adhesive. Semiconductor acceleration sensor. 19. The semiconductor acceleration sensor according to claim 12, wherein the support member is a conductive adhesive sheet for bonding the semiconductor sensor chip and the pedestal. 20. The support member according to claim 1, further comprising: a projection integrally formed on the semiconductor sensor chip side or the pedestal side, and holding the semiconductor sensor chip and the pedestal in contact with each other via the projection. 14. The semiconductor acceleration sensor according to claim 12, wherein the semiconductor acceleration sensor is made of an adhesive. 21. It has a weight portion supported via a beam portion, and is configured to detect an acceleration up to about ± 1 G by utilizing a piezoresistance effect of a resistance element formed on the beam portion. A semiconductor acceleration sensor provided with a semiconductor sensor chip according to claim 1, wherein said pedestal for supporting said semiconductor sensor chip and said semiconductor sensor chip are integrally formed of the same material. 22. The semiconductor sensor chip and the pedestal,
The semiconductor acceleration sensor according to claim 21, wherein the semiconductor acceleration sensor is formed by impurity concentration-dependent etching. 23. The semiconductor acceleration sensor according to claim 1, wherein an electrostatic shield is applied so as to remove an influence of static electricity on the semiconductor sensor chip. 24. The semiconductor acceleration sensor according to claim 23, wherein the electrostatic shield is formed on a housing for accommodating the semiconductor sensor chip and the pedestal.