JP2008008694A - Strain measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein strain sensitivity varies widely in measuring strains by using a strain measuring apparatus composed of a silicon substrate, since the silicon substrate is high in rigidity. <P>SOLUTION: At least a strain detecting section is disposed on the principal surface of the silicon substrate, and an insulating film is disposed on the upper surface of the strain detecting section, and a protection layer is disposed on the upper surface of the insulating film. Electric wiring connected electrically with the strain detecting section is arranged in the protection layer, and a mounting face is disposed on the surface of the protection layer. Since the strain detecting section is made close to an object to be measured without the intermediary of the silicon substrate having a high rigidity, the area where a property following strains is stable, is expanded, whereby the variation in strain sensitivity is reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus capable of measuring strain of an object.

  As a technique for measuring the deformation (strain) of a measurement object, a technique using a metal foil strain gauge utilizing the fact that the resistance value of the metal foil changes due to the strain is known. By attaching this strain gauge to the object to be measured, the length of the metal foil is changed following the strain of the object to be measured, and the resistance value of the metal foil that changes as a result can be detected to enable strain measurement of the object to be measured. Technology.

  However, when trying to drive these batteries, there is a problem that the batteries are consumed quickly because of the large power consumption. In view of this, the inventors of the present invention have proposed a semiconductor mechanical quantity measuring apparatus using an impurity diffusion resistance (hereinafter referred to as diffusion resistance) in which impurities are introduced into single crystal silicon as a strain sensitive resistor in order to reduce power consumption of the strain sensitive resistor. (For example, refer to Patent Document 1).

JP 2005-114443 A

  However, when strain is measured by a strain measuring device made of a silicon substrate, there is a concern that the variation in strain sensitivity of the strain detector becomes large because the rigidity of the silicon substrate is large. In the strain measuring apparatus described in Patent Document 1, since the opposite surface side of the main surface on which the diffusion resistance of the silicon substrate is formed is attached to the object to be measured, the rigidity of the silicon substrate greatly affects the sensitivity of strain detection. End up.

  An object of the present invention is to provide a strain measuring apparatus that can be driven with low power consumption, can perform highly accurate measurement, has little variation in strain sensitivity, and has high reliability.

  The above object is to provide a strain measuring apparatus for measuring strain by attaching to an object to be measured, a semiconductor substrate, a strain detector having an impurity diffusion layer provided on one principal surface of the semiconductor substrate, and the one principal surface. A protective layer made of a resin material, and a wiring provided in the protective layer and electrically connected to the strain detector, the protective layer being on the opposite side of the semiconductor substrate, This is achieved by a strain measuring device having a mounting surface to be attached to a measurement object or a mounting member.

  According to the present invention, since the strain detection unit can be brought close to the object to be measured without using a silicon substrate having high rigidity, the region in which the strain followability is stabilized is expanded, variation in strain sensitivity is reduced, and reliability is improved. Provided with high strain measurement device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a plan structure of a main part of the strain measuring apparatus according to the present embodiment, and FIG. 2 shows a cross-sectional structure taken along line AA of FIG.

  In the strain measuring apparatus 100 of the present embodiment shown in FIG. 1 and FIG. 2, at least a strain detector 2 is provided on the main surface 1a of a semiconductor substrate 1 which is a single crystal semiconductor substrate. It is formed from diffused resistors. Furthermore, since the strain detector 2 is formed of a Wheatstone bridge circuit composed of four impurity diffusion resistors, output fluctuations due to temperature drift can be removed, and strain can be detected with high accuracy.

  An insulating film 8 is provided on the strain detector 2. Although not shown, a thin film group such as a wiring for taking out an electric signal and an insulating material for insulating them is formed between the strain detector 2 and the insulating film 8 as necessary. In the present embodiment, the semiconductor substrate 1 and the strain detector 2, the insulating film 8 and other thin film groups formed on the main surface 1a of the semiconductor substrate 1 are collectively referred to as a sensor chip 200. A substrate pad 9 is provided on the surface of the sensor chip 200 and is electrically connected to the strain detector 2.

A protective layer 3 made of an organic film is provided so as to be in contact with the insulating film 8, and a wiring 4 is provided inside the protective layer 3 (although the wiring 4 does not exist on the AA cross section). For convenience of explanation, the projection onto the AA cross section is shown in FIG. The wiring 4 electrically connects the substrate pad 9 and the protective layer pad 10. A lead wire or the like is pulled out from the protective layer pad 10 and connected to an external measuring apparatus main body such as a data logger to measure strain. By providing the wiring 4 in the protective layer 3, disconnection of the wiring 4 and contact between the wirings 4 can be prevented. The protective layer 3 includes a central portion (first region) 3a having a strain detection portion attached to the upper portion thereof and not having the wiring 4, and a wiring around the central portion 3a, and a protective pad on the surface having the semiconductor substrate. And a peripheral portion (second region) 3b. By disposing the wiring 4 in the peripheral portion 3b avoiding the central portion 3a to which the strain detecting unit 2 is attached, variation in strain sensitivity due to the wiring 4 can be reduced. A mounting surface 11 is provided on the surface of the protective layer 3 opposite to the semiconductor substrate 1, and the mounting surface 11 is attached to a mounting member such as an object to be measured 6 or a mounting plate (not shown). The mounting surface 11 is desirably flat.

  In this embodiment, the protective layer 3 provided with the sensor chip 200 and the wiring 4 is collectively referred to as a strain measuring device 100.

  FIG. 3 shows a cross-sectional view of the main part when the strain measuring device according to the first embodiment is provided on a device under test. The mounting surface 11 of the strain measuring device 100 is bonded to the surface of the object 6 to be measured via the adhesive layer 5. Thereby, distortion also arises in the strain measuring apparatus 100 due to the strain change of the DUT 6, and the strain amount can be converted from the output change of the strain detector 2. For example, the adhesive layer 5 can be an epoxy adhesive or a phenol adhesive.

  Next, the operation and effect of this embodiment will be described.

  In the case of a strain measuring device that uses the impurity diffusion layer formed on the surface of the semiconductor substrate 1 as a strain sensitive resistor and measures strain using the piezoresistive effect of the impurity diffusion layer, the strain detection unit 2 has a large rigidity. There is a concern that the variation in strain sensitivity will increase. In the strain measuring apparatus according to the present invention, the strain detector 2 is formed on the main surface of the semiconductor substrate 1, the protective layer 3 for protecting the wiring 4 is provided on the main surface 1 a, and the mounting surface 11 of the protective layer 3. Is attached to the object to be measured, so that the strain detector 2 can be brought close to the object to be measured 6 without passing through the semiconductor substrate 1 having high rigidity, so that the region where the strain followability is stabilized is expanded and the strain sensitivity varies. Can be reduced.

  In addition, when the Young's modulus of the protective layer 3 is high, strain followability is improved, and when the Young's modulus is low, variation in strain sensitivity is reduced. Further, since the mounting surface 11 is flat, variation in strain sensitivity is reduced. In addition, since the strain detection unit 2 is disposed near the center of the semiconductor substrate 1, variations in strain sensitivity are reduced. Moreover, the adhesive strength in a protective layer interface and an adhesive agent improves by using a resin material for the protective layer 3. FIG. Furthermore, as shown in FIG. 4, weather resistance is improved by covering the entire sensor chip 200 with a covering material 12 such as a resin.

  As described above, the strain detector 2 is formed on the main surface of the semiconductor substrate 1, the protective layer 3 for protecting the wiring is provided on the main surface, and the protective layer 3 is attached to the object to be measured. A highly reliable strain measuring device is provided.

  Further, since these strain measuring devices 100 are formed based on the semiconductor substrate 1 which is a semiconductor substrate, they can be manufactured by using a semiconductor process. In the semiconductor process, elements and the like are usually formed only on one main surface of the semiconductor substrate 1. In the strain detection apparatus of the present invention, the strain detection unit 2 and the substrate pad 9 for taking out signals from the strain detection unit 2 are formed on the same main surface, so that the manufacturing process is simplified, and low cost and mass supply are possible. A suitable sensor chip 200 is obtained. In this case, the substrate pad 9 from which the signal is extracted is present on the main surface facing the object 6 to be measured, but by providing the wiring 4 in the protective layer 3, the object 6 side of the sensor chip 200 is measured. It becomes possible to take out a signal from the main surface. If a pad for extracting a signal is formed on the side surface of the semiconductor substrate 1 or the main surface opposite to the strain detection unit 2, the manufacturing process becomes complicated and the manufacturing cost increases.

  The sensor chip 200 can be mounted together with a semiconductor circuit such as a digital circuit such as a CPU, a memory circuit, a communication circuit, or the like. In addition, there is an effect that high-precision, low-cost and mass supply can be performed using semiconductor manufacturing equipment.

  Although FIG. 3 shows the case where the strain measuring device 100 is provided on the surface of the object 6 to be measured, the same effect can be obtained even if the strain measuring device is provided so as to be embedded partially or entirely.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 shows the cross-sectional structure and the planar structure of the main part of the strain measuring device according to the second embodiment, and the same reference numerals are given to the common parts with the first embodiment.

  In the strain measuring apparatus 100 of FIG. 1 according to the first embodiment, the bonding area where the adhesive material 10 is provided extends over the entire lower surface of the protective layer 3, whereas in FIG. Only the protective layer central portion 3a having the wiring is provided, and the peripheral portion 3b having the wiring is not attached. In this embodiment, the same effect as that of the first embodiment is obtained, and the peripheral portion 3b can be slid with respect to the device under test 6 without attaching the peripheral portion 3b to the device under test 6. The strain transmitted to 3b and the strain applied to the wiring 4 are reduced, and disconnection of the wiring 4 can be prevented. The peripheral portion 3b and the device under test 6 may have a gap or may be in contact with each other.

  A third embodiment of the present invention will be described with reference to FIG. FIG. 6 shows the cross-sectional structure and the planar structure of the principal part of the strain measuring device according to the third embodiment, and the same reference numerals are given to the parts common to the first embodiment.

In the strain measuring apparatus 100 of FIG. 1 according to the first embodiment, the protective layer 3 of the semiconductor substrate 1 is integrated, whereas in the strain measuring apparatus 101 of the present embodiment shown in FIG. A buffer layer 7 is provided separately as a central portion (first region) 3 a of the protective layer 3 below the portion 2. The buffer layer 7 covers the entire lower portion of the strain detection portion 2 of the sensor chip so as not to cover the wiring 4 and the substrate pad 9. In the present embodiment, the same effects as those of the first embodiment can be obtained, and the peripheral portion 3b of the protective layer 3 can be obtained by making the buffer layer 7 smaller in Young's modulus than the peripheral portion 3b of the protective layer 3. And the distortion added to the wiring 4 is reduced, and the disconnection of the wiring 4 can be prevented. The buffer layer 7 may be hollow, filled with an adhesive, and attached to the object to be measured. Further, if the buffer layer 7 is a separate body and the buffer layer 7 can be deformed independently of the peripheral portion 3b, the strain transmitted to the peripheral portion 3b and the wiring 4 becomes extremely small, and the wiring 4 is protected.

  As the structure of the buffer layer 7, there are a method of covering only the lower part of the strain detection unit 2 as shown in FIG. 7 and a method of covering the entire lower part of the protective layer while covering the lower part of the strain detection unit 2 as shown in FIG. 8. . Since the structure of FIG. 7 can be manufactured using a semiconductor process, there is an advantage that the manufacturing method is simple, and the structure of FIG. 8 has an advantage that strain applied to the protective layer 3 can be further reduced. .

  Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 9 shows the cross-sectional structure of the main part of the strain measuring device according to the fourth embodiment, and the same reference numerals are given to the common parts with the third embodiment.

  In the strain measuring apparatus 101 of FIG. 6 according to the third embodiment, the lower surface of the protective layer 3 and the buffer layer 7 are on the same plane, whereas in the strain measuring apparatus 102 of the present embodiment shown in FIG. The lower surface of the protective layer 3 is in a form above the lower surface of the buffer layer 7. Since the buffer layer 7 protrudes with respect to the peripheral portion 3b and only the buffer layer 7 is adhered to the object to be measured, the protective layer 3 is not strained and the disconnection of the wiring can be prevented.

In this embodiment, the buffer layer 7 that is the protective layer central portion 3a and the peripheral portion 3b of the protective layer are separate members, but the central portion 3a and the peripheral portion 3b of the protective layer are integrally formed as the same member, It is good also as a form which makes the mounting surface 11 side of the part 3a protrude rather than the peripheral part 3b.

It is a figure which shows the principal part cross-section of the mechanical quantity measuring device by the 1st Embodiment of this invention. It is a figure which shows the principal part planar structure of the mechanical quantity measuring device by the 1st Embodiment of this invention. It is a figure which shows the example which provided the mechanical quantity measuring device by the 1st Embodiment of this invention in the to-be-measured object. It is a figure which shows the principal part cross-section of the mechanical quantity measuring device by the 2nd Embodiment of this invention. It is a figure which shows the principal part planar structure of the mechanical quantity measuring device by the 2nd Embodiment of this invention. It is a figure which shows the principal part planar structure of the mechanical quantity measuring device by the 2nd Embodiment of this invention. It is a figure which shows the principal part cross-section of the mechanical quantity measuring device by the 3rd Embodiment of this invention. It is a figure which shows the principal part planar structure of the mechanical quantity measuring device by the 3rd Embodiment of this invention. It is a figure which shows the principal part cross-section of the mechanical quantity measuring device by the 4th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 1a ... Main surface, 2 ... Strain detection part, 3 ... Protective layer, 3a ... Center part (1st area | region), 3b ... Peripheral part (2nd area | region), 4 ... Wiring, 5 ... Adhesion Layer, 6 ... object to be measured, 7 ... buffer layer, 8 ... insulating film, 9 ... substrate pad, 10 ... protective layer pad, 11 ... mounting surface, 12 ... coating material, 100, 101, 102 ... strain measuring device, 200 ... sensor chip.

Claims (12)

In a strain measuring device that is attached to the object to be measured and measures strain,
A semiconductor substrate;
A strain detector having an impurity diffusion layer provided on one main surface of the semiconductor substrate;
A strain measuring apparatus characterized in that one main surface side provided with the impurity diffusion layer is a mounting surface side attached to a measured object or a mounting member. In claim 1,
A protective layer made of a resin material provided on the one main surface;
The strain measuring apparatus, wherein the protective layer has a mounting surface to be attached to an object to be measured or a mounting member. In a strain measuring device that is attached to the object to be measured and measures strain,
A semiconductor substrate;
A strain detector having an impurity diffusion layer provided on one main surface of the semiconductor substrate;
A protective layer made of a resin material provided on the one main surface;
A wiring provided in the protective layer and electrically connected to the strain detector;
The said protective layer has a mounting surface attached to a to-be-measured object or a mounting member on the opposite side to the said semiconductor substrate, The strain measuring apparatus characterized by the above-mentioned. In claim 3,
The semiconductor substrate has a substrate pad electrically connected to the strain detector on the one main surface,
The protective layer has a larger area than the semiconductor substrate, and has a protective layer pad for electrical connection to the outside on the surface provided with the semiconductor element,
The strain measurement apparatus, wherein the wiring is electrically connected from the substrate pad to the protective layer pad. In claim 4,
The protective layer is
A first region on which the strain detection unit of the semiconductor substrate is attached;
The strain measuring apparatus, wherein the substrate pad of the semiconductor substrate is present on the upper portion and includes the protective layer pad and a second region having the wiring. In claim 3,
The protective layer is
A first region on which the strain detection unit of the semiconductor substrate is attached;
A strain measuring apparatus comprising a second region having the wiring therein. In claim 6,
The first region is attached to the object to be measured or the mounting member,
The strain measuring apparatus, wherein the second region has a gap between the object to be measured or the mounting member. In claim 6,
In the first area, the mounting surface side protrudes more than the second area. In claim 6,
The first area is attached to the object to be measured, and the second area is slidable with respect to the object to be measured. In claim 6,
The strain measuring apparatus, wherein the material of the first region has a Young's modulus smaller than that of the material of the second region. In claim 6,
The strain detection apparatus, wherein the first region is thinner than the second region, or the first region is a cavity. In claim 6,
A strain measuring apparatus, wherein an adhesive is filled between the first region and the object to be measured or the mounting member and is attached to the object to be measured or the mounting member.

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