JPH0792186A - Semiconductor acceleration sensor - Google Patents

Abstract

PURPOSE:To provide a semiconductor acceleration sensor for detecting the acceleration accurately over a wide frequency range while resisting against excessive impact or an acceleration close to oscillation frequency. CONSTITUTION:An overlapped part 3 is formed in the center of a semiconductor substrate 2 using a semiconductor fabrication technology. The overlapped part 3 is supported freely rockably with respect to the peripheral outer frame part 5 by a thin strain imparting part 4 to which a viscoelastic body 6 is attached on the surface or rear thereof. Consequently, even if the sensor part 1 is subjected to excessive impact, the viscoelastic body 6 buffers the impact applied to the strain imparting part 4 which is thereby protected against being damaged. The viscoelastic body 6 also prevents the amplitude of vibration at the overlapped part 3 from being maximized in the vicinity of resonance frequency thus improving the frequency characteristics of semiconductor acceleration sensor.

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 formed by processing a semiconductor substrate.

[0002]

2. Description of the Related Art A semiconductor acceleration sensor has been conventionally manufactured by using a semiconductor planar process, and is characterized by its small size, high sensitivity and high reliability.

[0003]

However, the strain-generating portion connecting the weight portion and the support portion of the semiconductor acceleration sensor needs to be formed to a thin thickness of several μm to several tens of μm, and an excessive strain from the outside such as a fall may occur. There is a problem that the strained portion having poor impact resistance is relatively easily damaged by the impact of (1). In addition, a resonance frequency exists in the sensor section consisting of the weight section, the support section, and the strain generating section.When acceleration having a frequency close to this resonance frequency is applied to the sensor section, the amplitude of the weight section is maximized and There is a problem that the parts are damaged.

Further, ideally, it is desirable that the acceleration can be detected in the widest possible frequency range. However, since the resonance frequency exists in the sensor section, the accuracy of acceleration detection deteriorates in the frequency band near the resonance frequency. However, there is a problem that the usable frequency range of the semiconductor acceleration sensor is limited. The present invention has been made in view of the above problems, and provides a semiconductor acceleration sensor that can be accurately detected over a wide frequency range without being damaged even if an excessive impact or an acceleration close to the resonance frequency is applied. The purpose is.

[0005]

In order to achieve the above-mentioned object, the invention of claim 1 is such that a weight portion, a thin straining portion, and a supporting portion for swingably supporting the weight portion by the straining portion. And a sensor portion integrally formed by processing a semiconductor substrate, and a viscoelastic body is attached to at least one of the front and back surfaces of the strain generating portion.

According to a second aspect of the present invention, there is provided a sensor section in which a weight portion, a thin strain element and a support portion which swingably supports the weight element by the strain element are integrally formed by processing a semiconductor substrate. Capillary phenomenon is used in the narrow gap provided between the stopper portion and the stopper portion, which is provided in the sensor portion so as to face the weight portion and restricts the displacement of the weight portion beyond a predetermined value, and the strain portion. And a viscoelastic body attached to the surface of the strain-flexing portion.

According to a third aspect of the present invention, there is provided a sensor section in which a weight portion, a thin strain-generating portion, and a supporting portion which swingably supports the weight portion by the strain-generating portion are integrally formed by processing a semiconductor substrate. A substrate on which the stopper portion is provided on both the front and back surfaces of the sensor portion so as to face the weight portion and restricts the weight portion from being displaced more than a predetermined amount, and the sensor portion with the stopper portion provided on the front and back surfaces is bonded to the surface. And seals the sensor part and the stopper part bonded to the surface of the substrate and attaches to the surface of the strain generating part by using the capillary phenomenon to flow into a narrow gap provided between the stopper part and the strain generating part. And a viscoelastic body.

[0008]

According to the structure of the invention of claim 1, the weight portion, the thin strain generating portion, and the supporting portion for swingably supporting the weight portion by the strain generating portion are integrally formed by processing the semiconductor substrate. Since a viscoelastic body is attached to at least one of the front and back surfaces of the strain-flexing part, it is possible to apply excessive impact to the semiconductor acceleration sensor or to apply acceleration with a frequency near the resonance frequency of the sensor part. In addition, the impact on the strain-flexing part can be mitigated by the viscoelastic body to prevent the strain-defining part from being damaged, and the displacement due to the swing of the weight part is maximized with respect to the acceleration of the frequency near the resonance frequency. The frequency range of acceleration that can be detected can be expanded by suppressing the above.

According to the second aspect of the present invention, the sensor portion is formed by integrally processing the weight portion, the thin strain element and the support portion that swingably supports the weight element by processing the semiconductor substrate. And a capillary phenomenon in the narrow gap provided between the stopper portion and the strain-flexing portion, and the stopper portion that is disposed in the sensor portion so as to face the weight portion and restricts the displacement of the weight portion beyond a predetermined value. Since it is provided with a viscoelastic body that is introduced and attached to the surface of the strain-flexing portion, damage to the strain-generating portion is prevented by the stopper portion and the viscoelastic body, and the frequency range of acceleration that can be detected can be expanded. Since the viscoelastic body is attached according to the size of the gap between the stopper portion and the strain-flexing portion, it is possible to reduce the dimensional variation of the viscoelastic body.

According to the third aspect of the present invention, the sensor portion is formed by integrally processing the weight portion, the thin strain element and the support portion that swingably supports the weight element by processing the semiconductor substrate. A stopper portion that is provided on both the front and back surfaces of the sensor portion so as to face the weight portion and restricts the weight portion from displacing more than a predetermined amount, and a sensor portion where the stopper portion is disposed on both the front and back surfaces is bonded to the surface. Substrate and the sensor part and the stopper part bonded to the surface of the substrate are sealed, and the surface of the strain generating part is introduced into the narrow gap provided between the stopper part and the strain generating part by utilizing the capillary phenomenon. Since a viscoelastic body attached to the viscoelastic body is provided, not only can the strain-prone part be prevented from being damaged and the frequency range of acceleration that can be detected can be expanded, but also a sealing material that seals the sensor part and the stopper part can be used. Attached to the surface of the strain Rukoto can, it is possible to reduce the manufacturing process is able to attached simultaneously viscoelastic body and sealing step.

[0011]

【Example】

(Embodiment 1) FIG. 2 shows a perspective view of a sensor portion 1 of a semiconductor acceleration sensor of this embodiment. As shown in FIG. 2, a weight portion 3 is formed at the center of the semiconductor substrate 2 by using a semiconductor processing technique. The weight portion 3 is swingably supported by a surrounding outer frame portion 5 by a thin strain element 4, and the outer frame portion 5 serves as a support portion. A piezoresistor 4a for detecting strain is formed on the surface of the strain generating section 4.

FIG. 1 is a sectional view taken along the line AA of FIG. When acceleration G is applied in the direction shown by the arrow in FIG. 1, the weight portion 3 is bent by the acceleration. Due to the bending of the weight portion 3, stress and strain in proportion to the acceleration G are generated in the thin strain element 4. The resistance value of the piezoresistor 4a changes in proportion to the strain generated in the strain generating section 4. By extracting the change in the resistance value as a voltage output by forming a bridge, for example, a voltage corresponding to the acceleration G can be obtained, and the magnitude of the acceleration G can be detected as a voltage value.

As shown in FIG. 1, in this embodiment, a viscoelastic body 6 is attached to the front surface (see FIG. 2B) or the back surface (see FIG. 1A) of the strain generating portion 4. . The viscoelastic body 6 can be attached by a method such as attaching silicon gel or silicone rubber, or coating a resin material such as polyimide. In the above configuration, even when an excessive shock (acceleration) is applied to the sensor unit 1, the viscoelastic body 6 can mitigate the shock applied to the strain generating unit 4 and protect the strain generating unit 4 from the excessive shock. As a result, it is possible to prevent the strain portion 4 from being damaged.

Further, in the conventional structure in which the viscoelastic body 6 is not provided, when the natural frequency of the sensor section 1 and the frequency of the acceleration G applied from the outside are close to each other, the weight section 3 resonates to maximize the amplitude, As shown in FIG. 4, although the frequency range f ₀ (flat portion in the figure) where acceleration can be accurately detected becomes narrow, a book in which the viscoelastic body 6 is attached to at least one of the front and back surfaces of the strain-flexing portion 4 is used. in the configuration examples, it is possible to suppress to maximize the amplitude of the weight part 3 in the vicinity of the resonance frequency by the viscoelastic member 6, the frequency range f ₁ that the acceleration can be accurately detected as shown in FIG. 3 ( The flat portion in the figure) becomes wider, and the frequency characteristic can be improved even as a semiconductor acceleration sensor. Further, by appropriately selecting the viscosity of the material used for the viscoelastic body 6, it is possible to control the impact resistance of the strain-flexing portion 4 or to provide various frequency characteristics.

In this embodiment, the semiconductor acceleration sensor having a cantilever structure in which the weight part 3 is supported only on one side has been described, but the structure is one in which both ends are fixed and the strain generating part 4 is in a film structure. May be (Embodiment 2) A plan sectional view of a semiconductor acceleration sensor of this embodiment is shown in FIG. In the semiconductor acceleration sensor of this embodiment, the stopper portion 7 that restricts the weight portion 3 from being displaced more than a predetermined amount.
The a and 7b are opposed to the weight portion 3 and arranged on both front and back surfaces of the sensor portion 1 by bonding or the like. Further, a narrow gap 8 is provided between the stopper portion 7a on the front surface side and the surface of the strain-flexing portion 4, and the surface-side stopper portion 7a near the joint portion between the strain-generating portion 4 and the weight portion 3 is provided. A groove 9 for preventing the inflow of the sealing material is provided.

Stoppers 7a are provided on both front and back surfaces of the sensor unit 1,
The sensor chip formed by joining 7b is die-bonded on, for example, an alumina substrate 10, and the wiring formed on the alumina substrate 10 and the sensor unit 1 are connected by a wire 11 by wire bonding.
Then, in order to protect the sensor chip and the wire 11, the whole is sealed with a sealing material A. Here, the sealing material A
A material having viscoelasticity such as silicon gel, silicon rubber, or epoxy resin is used as the material, and the sealing material A for sealing the sensor chip is flowed into the gap 8 between the stopper portion 7a and the strain generating portion 4. A viscoelastic body 6 is attached to the surface of the strain generating section 4. The above-mentioned silicon gel and the like used as the encapsulating material A are all thermosetting, and when heated and cured, they are in a state of having fluidity. Therefore, the sealing material A flows into the gap 8 due to the capillary phenomenon, and the inflowing sealing material A collects in the groove 9 provided in the stopper portion 7a on the front surface side.
The viscoelastic body 6 can be formed by hardening without penetrating into the inside of the groove 9.

By the way, when joining the stopper portions 7a and 7b to both front and back surfaces of the sensor portion 1, conventionally, as shown in FIG. 6, the joint portion between the sensor portion 1 and the stopper portions 7a and 7b is made of gold and germanium. A method of eutectic bonding is used with an alloy (Au-Ge alloy) or an alloy of gold and tin (Au-Sn alloy). That is, as shown in FIG. 7, an alloy layer 12 in which the above alloy is vapor-deposited in advance to a thickness of about 2 μm on a portion of the surface of the stopper portion 7a that contacts the outer frame portion 5
Is formed, and the alloy layer 12 is melted in a state where the stopper portion 7a is in contact with the sensor portion 1 to perform eutectic bonding. However, in such a method, the alloy layer 12 spreads on the surface of the stopper portion 7a at the time of melting, so that there is a problem that the thickness of the alloy at the joint portion after the eutectic joining varies and cannot be controlled.

Therefore, as shown in FIGS. 8 (a) and 8 (b), trapezoidal protrusions 13 having a height dimension lower than the thickness of the alloy layer 12 are provided at the four corners of the surface of the stopper portion 7a so as to be adjacent to each other. An alloy is vapor-deposited between the protrusions 13 to form the alloy layer 12 (for example, when the thickness of the alloy layer 12 is 2 μm, the protrusions 1
The height dimension of 3 is 1.5 μm). Therefore, even if the melted alloy layer 12 spreads over the surface of the stopper portion 7a, the protrusion 13 comes into contact with the surface of the sensor portion 1 as shown in FIG. The height of the protrusion 13 can be controlled by limiting the gap of the height of the protrusion 13 to the height of the protrusion 13.

[0019]

According to the invention of claim 1, the weight portion, the thin strain generating portion, and the supporting portion for swingably supporting the weight portion by the strain generating portion are integrally formed by processing the semiconductor substrate. Since a viscoelastic body is attached to at least one of the front and back surfaces of the strain-flexing part, it is possible to apply excessive impact to the semiconductor acceleration sensor or to apply acceleration with a frequency near the resonance frequency of the sensor part. In addition, there is an effect that the impact applied to the strain-flexing portion can be alleviated by the viscoelastic body and damage to the strain-flexing portion can be prevented. Further, there is an effect that it is possible to expand the frequency range of the detectable acceleration by suppressing the displacement caused by the swing of the weight portion from being maximized with respect to the acceleration having a frequency near the resonance frequency.

According to a second aspect of the present invention, there is provided a sensor section in which a weight portion, a thin strain-generating portion, and a supporting portion for swingably supporting the weight portion by the strain-generating portion are integrally formed by processing a semiconductor substrate. Capillary phenomenon is used in the narrow gap provided between the stopper portion and the stopper portion, which is provided in the sensor portion so as to face the weight portion and restricts the displacement of the weight portion beyond a predetermined value, and the strain portion. Since it is provided with a viscoelastic body that is introduced and attached to the surface of the strain generating section, the effect of preventing damage to the strain generating section by the stopper section and the viscoelastic body and expanding the frequency range of detectable acceleration, Since the viscoelastic body is attached according to the size of the gap between the stopper portion and the strain generating portion, there is an effect that the dimensional variation of the viscoelastic body can be reduced.

According to a third aspect of the present invention, there is provided a sensor section in which a weight portion, a thin strain-generating portion, and a support portion which swingably supports the weight portion by the strain-generating portion are integrally formed by processing a semiconductor substrate. A substrate on which the stopper portion is provided on both the front and back surfaces of the sensor portion so as to face the weight portion and restricts the weight portion from being displaced more than a predetermined amount, and the sensor portion with the stopper portion provided on the front and back surfaces is bonded to the surface. And seals the sensor part and the stopper part bonded to the surface of the substrate and attaches to the surface of the strain generating part by using the capillary phenomenon to flow into a narrow gap provided between the stopper part and the strain generating part. Since it has a viscoelastic body, it is possible to prevent damage to the strain-causing part and expand the frequency range of detectable acceleration. Attached to the surface of the strained part as a body And, there is an effect that it is possible that the reducing can manufacturing step of attaching a simultaneous viscoelastic body and sealing step.

[Brief description of drawings]

FIG. 1 is a cross-sectional plan view of a sensor unit according to a first embodiment.

FIG. 2 is a perspective view of the sensor unit showing the same as above.

FIG. 3 is a diagram showing a frequency characteristic of detected acceleration in the above.

FIG. 4 is a diagram showing frequency characteristics of acceleration detected by a conventional semiconductor acceleration sensor.

FIG. 5 is a plan sectional view showing a second embodiment.

FIG. 6 is a plan cross-sectional view of the sensor section and the stopper section of the above.

FIG. 7 is a plan view showing a stopper portion of the above.

8A and 8B show another stopper portion, FIG. 8A is an overall plan view, and FIG. 8B is an enlarged cross-sectional view of a main portion before joining.
(C) is an enlarged cross-sectional view of a main part after joining.

[Explanation of symbols]

 1 sensor part 2 semiconductor substrate 3 weight part 4 strain generating part 5 outer frame part 6 viscoelastic body

Claims (3)

[Claims] 1. A strain sensor comprising a weight portion, a thin strain element, and a support portion integrally supporting a weight portion by the strain element to swingably support the weight portion. A semiconductor acceleration sensor having a viscoelastic body attached to at least one of the front and back surfaces of the section. 2. A sensor portion integrally formed by processing a semiconductor substrate with a weight portion, a thin strain element and a support portion that swingably supports the weight portion by the strain element, and a sensor portion opposed to the weight portion. Strain sensor is installed in the sensor section to restrict the weight section from displacing more than a predetermined amount, and a narrow gap provided between the stopper section and the strain-flexing section flows into the narrow gap using the capillary phenomenon. A semiconductor acceleration sensor, comprising: a viscoelastic body attached to a surface of the portion. 3. A sensor portion integrally formed by processing a semiconductor substrate with a weight portion, a thin strain generating portion, and a supporting portion that swingably supports the weight portion by the strain generating portion, and a weight portion. On the front and back sides of the sensor unit to prevent the weight unit from displacing more than a predetermined amount, the substrate on which the sensor units with the stopper units disposed on the front and back sides are bonded to the surface, and the substrate surface. A viscoelastic body that seals the bonded sensor part and stopper part and flows into the narrow gap provided between the stopper part and the strain-flexing part by utilizing the capillary phenomenon and is attached to the surface of the strain-defining part. A semiconductor acceleration sensor, comprising: