JP2008070312A - Multi-range acceleration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a plurality of three-axis acceleration sensors of significantly different measurement ranges in small area at low cost, and to accurately align the directions of the acceleration detection axes of the plurality of sensors. <P>SOLUTION: A first three-axis acceleration sensor element comprises a frame section, a weight section held in the frame section via a flexible section, and a semiconductor piezo resistance element disposed in the flexible section. In the frame section of the first three-axis acceleration sensor element, a second three-axis acceleration sensor element having an output voltage per unit acceleration smaller than that of the first three-axis acceleration sensor element is formed. The miniaturization is allowed by sharing the frame section, the manufacturing cost is low because collective formation on one chip is allowed by a process of photolithography, etching or the like, and the acceleration detection axes of the plurality of sensor elements are aligned at a high photolithography mask accuracy. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a semiconductor acceleration sensor for detecting acceleration used in portable terminal devices, toys, automobiles, airplanes and the like.

The acceleration sensor is often used for the operation of an air bag of an automobile, and captures the impact of the collision of the automobile as acceleration. In automobiles, a one-axis or two-axis function is sufficient to measure the X-axis and Y-axis accelerations. Further, since the acceleration to be measured is very large, an acceleration sensor element for detecting the acceleration is also sturdily manufactured. Recently, acceleration sensors are increasingly used for portable terminal devices and robots. In order to detect movement in a three-dimensional space, a three-axis acceleration sensor capable of measuring X, Y, and Z-axis acceleration has been required. In these applications, not only detection of a small acceleration of several G to several tens of G is required, but also high resolution is required.

Accelerometers are roughly classified into a beam type and a diaphragm type according to the structure of a flexible portion, and a piezoresistive type and a capacitance type according to a displacement detection method.

The applicant has filed a large number of applications regarding a beam-type piezoresistive element type three-axis acceleration sensor. Patent Document 1 to Patent Document 6 clarify the shape of the weight portion, the shape of the beam portion, the arrangement of the piezoresistive elements, the connection method of the piezoresistive elements, the shape of the joint between the beam portion and the frame portion, and the like. 9 is an exploded perspective view of the triaxial acceleration sensor, FIG. 10a) is a cross-sectional view in the hh ′ direction of FIG. 9, and FIG. 10b) is a plan view of the sensor chip. In the triaxial acceleration sensor 20, the sensor chip 2 and the regulating plate 3 are fixed to the case 1 with an adhesive 16 such as resin at a predetermined interval. Sensor chip 2
The chip terminal 4 is connected to the case terminal 6 by a wire 5, and the sensor signal is taken out from the external terminal 7. A case lid 8 is fixed to the case 1 with an adhesive 17 such as AuSu solder and sealed. A beam-type triaxial acceleration sensor element 9 is formed on the sensor chip 2. The beam-type triaxial acceleration sensor element 9 includes a beam portion 12 that is paired with a rectangular frame portion 10 and a weight portion 11, and the weight portion 11 is held at the center of the frame portion 10 by two pairs of beam portions 12. Yes. A piezoresistive element is formed on the beam portion 12. An X-axis piezo 13 and a Z-axis piezo 15 are formed on a pair of beams, and a Y-axis piezo 14 is formed on the other pair of beams. The lower surface of the weight part 11 and the case 1 in FIG.
The distance g4 between the inner bottom surface and the distance g3 between the upper surface of the weight portion 11 and the regulating plate 3 regulates the amount of movement of the weight portion 11 when an excessive acceleration such as an impact is applied to the sensor. This is to prevent damage. Since the basic structure of the beam-type three-axis acceleration sensor element of the present application is the same as those of these patent documents, detailed description is omitted unless otherwise specified.

JP 2003-172745 A Japanese Patent Laid-Open No. 2003-279592 JP 2004-184373 A JP 2006-098323 A JP 2006-098321 A WO2005 / 062060 A1

Patent Documents 7 to 9 disclose a diaphragm structure of a diaphragm type three-axis acceleration sensor element, an arrangement method of a piezoresistive element, and the like. The outer edge of the circular or polygonal diaphragm is supported by a support frame, and a weight is arranged at the center of the diaphragm. When the weight is displaced by an external force, the piezoresistive element provided on the diaphragm is deformed and an electric signal is obtained. There is an advantage that the degree of freedom of arrangement of the piezoresistive elements is higher than that of the beam type triaxial acceleration sensor element. FIG. 10c) shows a plan view of a diaphragm type triaxial acceleration sensor element 9 ′. A rectangular frame portion 10, a weight portion 11, and a diaphragm 19 serving as a flexible portion, and the weight portion 11 is the diaphragm 1.
9 is held in the center. The diaphragm 19 is formed with a piezoresistive element, an X-axis piezo 13, a Y-axis piezo 14, and a Z-axis piezo 15. Since the basic structure of the diaphragm type piezoresistive element type triaxial acceleration sensor and the diaphragm type triaxial acceleration sensor element of the present application is substantially the same as those of these patent documents, detailed description will be omitted unless otherwise specified.

Japanese Patent Laid-Open No. 3-2535 JP-A-6-174571 Japanese Patent Laid-Open No. 7-191053

It is several G level for applications such as detecting the fall state of portable small devices and user interfaces such as shaking and operating, but for applications such as impact detection, the value is several hundred to several thousand G. For example, in a portable device incorporating a magnetic disk, there is a use in which the head is retracted when a drop is detected so that the magnetic disk is not destroyed by an impact at the time of dropping, thereby preventing destruction at the time of the impact. In addition, when repairing a damaged product, there is a need to know the history of how the product was impacted. The applicant also clarifies in Japanese Patent Application Laid-Open No. H10-228707 about a method for efficiently recording the history of impact acceleration in combination with fall detection. As described above, there is a demand to detect a drop of several G level and an impact detection of several hundred to several thousand G levels with one product. In that case, in order to obtain acceleration of several G and several hundred to several thousand G with high accuracy,
It is difficult with one acceleration sensor. This is because the resolution (accuracy) of detection cannot be obtained when an acceleration of several G is detected by an acceleration sensor that measures acceleration of several hundred to several thousand G.

JP-A-2005-241503

In order to detect acceleration of a large value of several hundred to several thousand G and acceleration of a small value of about several G with the same resolution, an acceleration sensor that measures several hundred to several thousand G and an acceleration sensor that measures several G are separated. There was a need to prepare. FIG. 11 shows that acceleration sensors 21, 22, and 23 each having a measurement range of several G, several tens of G, and several hundred G are mounted on a circuit board 24, and acceleration of several G to several hundred G is achieved with high resolution. This is an acceleration sensor device 25 that can be measured. Since three acceleration sensors are used, it can be easily understood that at least the price of the acceleration sensor device is several times that of the acceleration sensor. It is also easy to understand that miniaturization is difficult.

In the acceleration sensor device 25 using a plurality of acceleration sensors, it is very difficult to align the detection axis directions between the acceleration sensors. When connecting the acceleration sensor to the circuit board with solder, it is difficult to make the angular deviation of the detection axis of the acceleration sensor element between the acceleration sensors substantially zero. Even if a part of the outer shape of the acceleration sensor is assembled as a reference, if the outer shape reference and the axis of the acceleration sensor element do not coincide with each other, an axis deviation occurs. If there is an angular shift of the detection axis between the acceleration sensors, for example, a measurement value of several G acceleration sensors and a measurement value of several tens of G acceleration sensors cannot be measured as accelerations in the same axial direction.

Patent Document 11 discloses a multi-range acceleration sensor that realizes downsizing and cost reduction and can eliminate the angular deviation of the detection axis. FIG. 12 shows the structure. The multi-range acceleration sensor 30 has a structure in which two or more sensor elements are provided in a frame 31, and the sensor element is connected to one end of a beam 32 to the frame 31 and the other to a weight 33. The beam 32 has a cantilever structure in which the weight 33 serves as a power point with a connection point with the frame 31 as a fulcrum. The movement of the weight 33
The acceleration is measured by measuring the capacitance change between the weight 33 and the electrode 34 arranged at a predetermined interval. The sensor element determines the range of acceleration to be measured by changing the length of the beam and the mass of the weight.

JP-A-8-136574

In the acceleration sensor of Patent Document 11, sensor elements having different measurement ranges are formed on a single chip, so that it is possible to eliminate axial misalignment between the sensor elements. Axial misalignment occurs due to errors in photolithographic photomasks and photolithography, but it is almost negligible and no misalignment. However, since Patent Document 11 is a uniaxial sensor element, in order to measure triaxial acceleration, it is necessary to arrange the three sensor elements at positions different from each other by 90 degrees. It can be understood that it is very difficult to accurately arrange the X, Y, and Z axes and arrange the three sensor elements. Moreover, since it is necessary to combine three sensor elements, it can be easily understood that miniaturization is difficult. The multi-range three-axis acceleration sensor is obtained by using the multi-range one-axis acceleration sensor disclosed in Patent Document 11. The conventional acceleration sensor device shown in FIG. 11 and the number, price, and size of the acceleration sensor are substantially the same. There is no big difference.

In the acceleration sensor structure of Patent Document 11, there is a possibility of interference between sensor elements, and countermeasures are also required. Since the plurality of beams 32 are formed on one side of the frame 31, the movement of one sensor element tends to affect the measurement of the other sensor element. Beam 3
When acceleration is applied in the width direction 2, it is necessary to prevent other sensor elements and the weight 33 from colliding with each other, and consideration such as opening the sensor elements is also necessary.

An object of the present invention is to provide a high-precision and small-sized multi-range three-axis acceleration sensor at low cost by forming sensor elements having different measurement ranges on one chip and causing no deviation of each axis between sensor elements having different measurement ranges. Is.

The multi-range triaxial acceleration sensor of the present invention includes a frame, a weight held by the frame via the flexible part, a semiconductor piezoresistive element provided in the flexible part, and a wiring connecting them. Two or more diaphragm-type three-axis acceleration sensor elements that can detect acceleration in three axes, that is, two axes in the plane where the flexible part is formed and an axis substantially perpendicular to the plane, are formed on the same chip. A multi-range triaxial acceleration sensor having a multi-range sensor chip, wherein a plurality of diaphragm type triaxial acceleration sensor elements of the multirange sensor chip are per unit acceleration in order from the first to the nth diaphragm type triaxial acceleration sensor element. The output voltage is preferably small.

In the diaphragm type three-axis acceleration sensor element, the flexible part is deformed due to the acceleration acting on the weight part, and stress is generated in the semiconductor piezoresistive element formed on the beam part, and the electric resistance is changed. This is a mechanism for converting to (output voltage) and outputting. The first to nth diaphragm type triaxial acceleration sensor elements are formed so that the output voltage with respect to the unit acceleration decreases in order.

For example, the first diaphragm type three-axis acceleration sensor element having a measurement range of ± 3 G has an acceleration of 1
The output voltage per G is set to 1V, and the nth diaphragm type triaxial acceleration sensor element of the measurement range 300G sets the output voltage per acceleration 1G to 0.01V, thereby measuring each diaphragm type triaxial acceleration sensor element. The full range of the output voltage corresponding to the range can be adjusted to ± 3 V, and if each ± 3 V is detected with the same resolution, highly accurate detection can be performed in each of the different acceleration ranges.

The output per unit acceleration of each acceleration sensor element is set so that the output voltage is in a region where the linearity is maintained in the measurement range. If the output voltage per unit acceleration is set too high for a sensor element with a wide measurement range, the deformation of the flexible part reaches a non-linear region within the measurement range, and the linearity of the output voltage cannot be maintained. There is a fear.

The first to nth diaphragm type triaxial acceleration sensor elements are formed in the same chip. Therefore, an individual process is not required for forming each element, and the shape of each element is drawn on a photomask and can be formed at a low cost by using a photolithographic process or an etching process.

In addition, since the first to nth diaphragm type triaxial acceleration sensor elements are formed on the same chip surface, it is easy to match the detection axis (Z axis) in the direction perpendicular to the chip surface with high accuracy. Is possible. Furthermore, two detection axes (X and Y axes) parallel to the chip surface can be easily matched with high accuracy according to the photolithography mask accuracy.

By arranging the restriction plates above and below the multi-range sensor chip, when acceleration exceeding the measurement range occurs, the weight part hits the restriction plate to restrict further displacement and prevent destruction of the flexible part It is possible to realize a highly reliable multi-range acceleration sensor.

The upper and lower regulating plates are preferably made of a material having a thermal expansion coefficient close to that of the multi-range sensor chip, and for example, a material such as glass, silicon, ceramic, or FeNi alloy can be used. Bonding is performed using an adhesive or metal bonding so as to form a gap between the three-axis acceleration sensor element.

Further, an IC chip used as a detection circuit may be used for the upper regulating plate. In addition, when the multi-range acceleration sensor is installed in a case and housed in a package with a lid on the top, the inner bottom of the case can be used instead of the lower regulating plate.

By making the distance between the weight portion of each diaphragm type triaxial acceleration sensor element and the restriction plate the same, the restriction plate is flat and desirable in terms of ease of manufacture. In that case, all diaphragm type 3
With respect to the axial acceleration sensor element, the interval is set such that the weight portion does not collide with the restricting plate in the measurement range and the flexible portion is not damaged before the weight portion collides with the restricting plate. In addition, when the interval satisfying the above cannot be obtained or when more importance is attached to the reliability, the restriction plate is arranged so that the distance between the weight part and the restriction plate becomes narrower as the measurement range is larger. In that case, it is realizable by forming the cavity part from which a depth differs, for example in a control board. In addition, for some diaphragm type triaxial acceleration sensor elements in reverse order from the nth measurement range having a large measurement range, when there is no possibility that the flexible part is damaged due to the acceleration that is expected to occur, the restriction plates are vertically May not be arranged.

In the multi-range triaxial acceleration sensor of the present invention, at least one triaxial acceleration sensor element of the first to nth diaphragm type triaxial acceleration sensor elements has a frame portion and a pair of beam portions that form a pair. It can be replaced with a beam type triaxial acceleration sensor element having a weight part held by the part, a semiconductor piezoresistive element provided on the beam part, and a wiring connecting them.

Which of the diaphragm type triaxial acceleration sensor element and the beam type triaxial acceleration sensor element is used can be determined from the measurement range of the acceleration, the external dimensions of the sensor element, the ease of manufacture, and the like. The first is a diaphragm type, the second is a beam type, the third is a combination like a diaphragm type,
A combination in which the first is a beam type and the second and third are diaphragm types is also possible. The beam-type triaxial acceleration sensor element forms a beam portion by etching a thin silicon layer. Although the machining process is increased, the bending rigidity of the beam portion can be reduced and the output per unit acceleration can be increased as compared with the diaphragm-shaped flexible portion of the diaphragm type triaxial acceleration sensor element that is not processed. By applying a beam shape to the first triaxial acceleration sensor element, the size of the first triaxial acceleration sensor element can be reduced, and the size of the entire multi-range acceleration sensor chip can be reduced. Hereinafter, unless otherwise specified, the diaphragm type triaxial acceleration sensor element and the beam type triaxial acceleration sensor element are collectively referred to as a triaxial acceleration sensor element.

In the multi-range triaxial acceleration sensor of the present invention, the first to n-th triaxial acceleration sensor elements of the multi-range sensor chip are at least one frame side of the frame portion constituting the first triaxial acceleration sensor element. It is preferable to form the second to nth triaxial acceleration sensor elements.

By forming the second to nth triaxial acceleration sensor elements in the frame side of the frame portion of the first triaxial acceleration sensor element, each triaxial acceleration sensor element shares the frame portion and has a small area. A plurality of ranges of three-axis acceleration sensor elements can be disposed therein. In addition, each triaxial acceleration sensor element is separated by a respective frame portion, so that each vibration does not affect other triaxial acceleration sensor elements, and the weight portion is the weight portion of the other acceleration sensor element. There is no interference.

In the multi-range triaxial acceleration sensor of the present invention, it is preferable that the thickness of the flexible portion of all the triaxial acceleration sensor elements is the same.

In the triaxial acceleration sensor element of the present application, when the thickness of the flexible portion changes, the output voltage with respect to the unit acceleration changes sensitively. Therefore, it is desirable to form the thickness of the flexible portion with high accuracy. Therefore, SOI (a thin silicon layer and a thick silicon layer stacked via a silicon oxide film layer)
It is desirable to process using a silicon on insulator substrate. A thick silicon layer is processed to form a weight portion, and a thin silicon layer remains in a portion where the silicon layer is removed by processing, thereby forming a flexible portion. In the multi-range triaxial acceleration sensor of the present application, it is not necessary to form flexible portions having different thicknesses in a thin silicon layer by making the thicknesses of the flexible portions of all the triaxial acceleration sensor elements the same. Using the thickness of the thin silicon layer as it is,
The flexible portions of all the three-axis acceleration sensor elements can be formed at once, and the number of manufacturing steps can be reduced, so that it can be manufactured at low cost.

In the multi-range triaxial acceleration sensor of the present invention, it is preferable that the thicknesses of the weight portions of all the triaxial acceleration sensor elements are the same.

In the multi-range triaxial acceleration sensor of the present invention, it is preferable that the thicknesses and the frame portions of all the triaxial acceleration sensor elements have the same thickness.

Like the flexible part, the frame part and the weight part have the same thickness in all the three-axis acceleration sensor elements, and the weight part of all the three-axis acceleration sensor elements is used by using the thickness of the thick silicon layer as it is. It can be formed all at once with a single etching. Thereby, since a manufacturing man-hour can be reduced, it can manufacture at low cost.

In addition, since the positions of the lower surface of the frame portion and the weight portion are aligned within the same plane, the multi-range acceleration sensor chip and the lower regulating plate are disposed via spacers of the same height in at least three positions of the frame portion. Thus, the distance between the lower surface of the weight and the regulating plate can be easily made the same for all the three-axis acceleration sensor elements.

In the multi-range triaxial acceleration sensor of the present invention, it is preferable that the mass of the weight portion decreases in order from the first to the nth triaxial acceleration sensor element.

By reducing the mass of the weight portion, the force acting on the weight portion with respect to the unit acceleration is reduced, so that the output voltage per unit acceleration can be reduced. In the multi-range three-axis acceleration sensor of the present invention, it is desirable that the thickness of the weight part is the same as described above. Therefore, it is desirable to reduce the mass of the weight part by reducing the dimensions in the chip surface. .

In the multi-range triaxial acceleration sensor of the present invention, it is preferable that the distance between the weight portion and the frame portion becomes shorter in order from the first to the nth triaxial acceleration sensor element.

By shortening the distance between the weight part and the frame part, the bending rigidity of the flexible part connecting the two parts increases, so the stress generated in the flexible part with respect to unit acceleration decreases. The output voltage per unit acceleration can be reduced.

In the multi-range triaxial acceleration sensor of the present invention, it is preferable that the area surrounded by the connection portion between the flexible portion and the frame portion is reduced in order from the first to the nth triaxial acceleration sensor element.

The area surrounded by the connection portion between the flexible portion and the frame portion is the size of the inner region of the frame portion, and 3
In other words, the dimension occupying the chip surface of the axial acceleration sensor element. The smaller the dimension, the smaller the dimension of the weight part, and the shorter the distance between the weight part and the frame part, the smaller the force acting on the weight part, and the higher the bending rigidity of the flexible part, The output voltage per unit acceleration can be reduced.

The multi-range triaxial acceleration sensor according to the present invention includes at least one triaxial acceleration sensor element from the second to the nth, a frame portion, a weight portion held by the frame portion by a pair of beam portions, and a beam portion The semiconductor piezoresistive element provided on the substrate and the wiring connecting them can detect the acceleration of the first axis in the plane where the beam portion is formed and the second axis substantially perpendicular to the plane. It is preferable that two beam-type two-axis acceleration sensor elements are constituted by a three-axis acceleration sensor element in which the first axes are arranged so as to be orthogonal to each other.

Compared with a beam-type triaxial acceleration sensor element having two beam pairs, the beam-type biaxial acceleration sensor element has a smaller bending rigidity in order to obtain the same output since the bending rigidity of the entire beam portion is reduced.
Further, the dimension in the direction where there is no beam pair is reduced. For example, the size of the multi-range acceleration sensor chip can be reduced by arranging it around the first three-axis acceleration sensor element having the largest outer dimension.

In the multi-range triaxial acceleration sensor of the present invention, it is preferable that the beam portions of all the beam type biaxial acceleration sensor elements and the flexible portions of the triaxial acceleration sensor elements have the same thickness.

All the beam-type 2-axis acceleration sensor elements and 3-axis acceleration sensor elements have the same thickness, so that it is not necessary to form flexible parts having different thicknesses in a thin silicon layer. By using the thickness of the silicon layer as it is, the flexible portions of all the biaxial and triaxial acceleration sensor elements can be formed in a lump, so that the number of manufacturing steps can be reduced and the production can be performed at low cost.

In the multi-range triaxial acceleration sensor of the present invention, it is preferable that the thicknesses of the weight portions of all the beam type biaxial acceleration sensor elements and the triaxial acceleration sensor elements are the same.

Like the flexible part, the frame part and the weight part have the same thickness in all beam-type biaxial acceleration sensor elements and triaxial acceleration sensor elements, so that the thickness of the thick silicon layer is used as it is. Since the beam-shaped two-axis acceleration sensor element and the weight part of the three-axis acceleration sensor element can be formed at a time by one etching, the number of manufacturing steps can be reduced, so that it can be manufactured at low cost.

In the multi-range triaxial acceleration sensor of the present invention, it is preferable that the thicknesses of the weight portion and the frame portion of all the beam type biaxial acceleration sensor elements and the triaxial acceleration sensor elements are the same.

Like the flexible part, the frame part and the weight part have the same thickness for all beam-type two-axis acceleration sensor elements and three-axis acceleration sensor elements. Since the weight portions of the mold 2-axis acceleration sensor element and the 3-axis acceleration sensor element can be formed all at once by a single etching, the number of manufacturing steps can be reduced and the manufacturing can be performed at low cost.

According to the multi-range acceleration sensor of the present invention, since a plurality of three-axis acceleration sensor elements can be collectively formed on the same chip, individual processing steps are not required for each element, and the frame portion can also be shared, A multi-range acceleration sensor capable of detecting three-axis acceleration can be provided in a small and inexpensive manner.

Hereinafter, the present invention will be described in detail based on examples with reference to the drawings. In order to make the explanation easy to understand, the same reference numerals are used for the same parts and parts.

A multi-range acceleration sensor according to a first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a developed perspective view of the multi-range acceleration sensor according to the first embodiment, and FIG. 2 is a perspective view of the multi-range sensor chip. 3 is a cross-sectional view taken along the line j ′ of FIG. In FIG. 1, a multi-range acceleration sensor 40 includes a multi-range sensor chip 41 in which a diaphragm type triaxial acceleration sensor element is formed, and an IC regulation plate 42 in which a detection circuit is formed and also serves to regulate the movement of the sensor element. It was set in the case 1 made of alumina and sealed with the case lid 8 made of alumina. Chip terminal 4 of multi-range sensor chip 41
And the IC terminal 43 between the IC terminal 43 of the IC regulation plate and the case terminal 6 connected to the external terminal 7 of the case 1 and the IC terminal 43, the detection signal of the sensor It can be taken out from the external terminal 7.

As shown in FIG. 3, the multi-range sensor chip 41 is attached to the inner bottom of the case 1 with an adhesive 16.
It was fixed using. Plastic balls are kneaded in the adhesive 16, and a constant interval is formed between the weight 47 of the sensor element and the inner bottom of the case 3. Similarly, the IC restricting plate 42 is adhered on the multi-range sensor chip 41 with the adhesive 16 in which plastic balls are kneaded so that a constant distance is formed between the weight portion of the sensor element and the IC restricting plate 42. . Case lid 8
Was fixed to the case 1 with an adhesive 17 and sealed to form a multi-range triaxial acceleration sensor 40.

The structure of the multi-range sensor chip 41 will be described with reference to FIG. The multi-range sensor chip 41 is formed with a first diaphragm type triaxial acceleration sensor element 44 and a second diaphragm type triaxial acceleration sensor element 44 '. In the diaphragm type triaxial acceleration sensor element 44, a weight portion 47 is supported in a frame portion 46 by a diaphragm-like flexible portion 48 formed thinner than the frame portion 46 and the weight portion 47. Multi-range sensor chip 4
When the X-axis and Y-axis are set in the plane direction 1 and the Z-axis is set in the vertical direction, the X-axis piezo 13 that is a piezoresistive element for X-axis direction acceleration detection is placed on the flexible portion 48 along the X-axis. The Y-axis piezo 14 for detecting the Y-axis direction acceleration was formed along the Y-axis. The Z-axis piezo 15 for detecting the Z-axis acceleration may be in either axial direction, but here it is formed along the X-axis. Four piezoresistive elements were formed for each axis and connected by wiring not shown to constitute a bridge circuit. By applying a force to the weight part due to acceleration and displacing it, and deforming the flexible part, the electrical resistance of the piezoresistive element changes, and the potential difference due to the difference in resistance change of the four piezoresistive elements is taken out by the bridge circuit. , Acceleration can be detected.

The second diaphragm type triaxial acceleration sensor element 44 ′ has the same configuration, but the second diaphragm type triaxial acceleration sensor element 44 ′ is a frame portion 46 of the first diaphragm type triaxial acceleration sensor element 44. It is formed on one frame side.

The second diaphragm type triaxial acceleration sensor element 44 ′ has a smaller output voltage per unit acceleration than the first diaphragm type triaxial acceleration sensor element 44.
That is, the second diaphragm type triaxial acceleration sensor element 44 ′ has a wider measurement range than the full scale of the output voltage. For example, the measurement range of the first diaphragm type triaxial acceleration sensor element 44 is used for drop detection as ± several G, and the measurement range of the second diaphragm type triaxial acceleration sensor element 44 ′ is set to ± several hundreds G for impact detection. Can be used. A plurality of chip terminals 4 were formed on the multi-range sensor chip.

A method for manufacturing the acceleration sensor element will be briefly described. Several microns on a silicon plate with a thickness of about 400
SOI (Silicon on In) having a silicon oxide layer of m and a silicon layer of 6 μm
sulator) wafers were used. Patterning was performed with a photoresist, boron was implanted into the silicon layer at 1 to ³ × 10 ¹⁸ atoms / cm ³ to form a piezoresistor, and a wiring connected to the piezoresistor was formed using a metal sputtering and dry etching apparatus. The silicon plate was processed using photolithography and a dry etching apparatus to create the shape of the weight portion. The removed portion of the silicon plate retains the thickness of the silicon layer, and this portion becomes a flexible portion. The silicon oxide layer functions as an etching stopper during dry etching of silicon. A large number of chips were produced on one wafer and separated into single chips by dry etching or dicing.

In the multi-range acceleration sensor of the present embodiment, the first diaphragm type triaxial acceleration sensor element 44 and the second diaphragm type triaxial acceleration sensor element 44 ′ can be collectively formed on one multirange sensor chip 41. It is. By forming both shapes into a silicon dry etching mask and processing them simultaneously, two sensor elements having different measurement ranges can be formed without adding a process, and the manufacturing cost can be reduced. Further, in order to form the second diaphragm type triaxial acceleration sensor element 44 ′ in the frame part 46 of the first diaphragm type triaxial acceleration sensor element 44, the frame parts of the two sensor elements are made common and have a small area. The multi-range acceleration sensor can be downsized. In addition, since the beam portions of the two sensor elements can be aligned by the mask pattern, the acceleration detection axes of the two sensor elements can be matched with high accuracy. Of the first diaphragm type triaxial acceleration sensor element 44 and the second diaphragm type triaxial acceleration sensor element 44 ',
The frame portion 46, the weight portion 47, and the flexible portion 48 have the same thickness.

The second diaphragm type three-axis acceleration sensor element 44 'is the first diaphragm type 3
In order to make the output voltage per unit acceleration smaller than that of the axial acceleration sensor element 44, it is possible to shorten the width of the flexible portion, that is, the distance between the weight portion and the frame portion, thereby increasing the bending rigidity of the flexible portion. desirable. It is also desirable to reduce the external dimensions of the weight and reduce the weight of the weight. Thereby, the area where the weight part and the beam part are arranged is the second diaphragm type triaxial acceleration sensor element 44.
It is desirable that 'is smaller. That is, it is desirable that the space area inside the frame portion is small.

In the case of impact acceleration detection, if vibration near the resonance frequency of the acceleration sensor is applied to the acceleration sensor due to the impact of a collision of a device equipped with the acceleration sensor, the vibration at the resonance frequency remains without being attenuated. As a result, there is a risk of malfunction in the detected waveform. Therefore, it is necessary to increase the resonance frequency in impact detection. The second three-axis acceleration sensor element 44 ′ for measuring the high acceleration range is used for impact detection because the flexural rigidity of the flexible part is high and the weight of the weight is reduced, so that the resonance frequency of the sensor element is also high. The characteristic that it was easy was obtained.

In the first diaphragm type triaxial acceleration sensor element 44 for measuring the low acceleration range, if the acceleration greatly exceeds the measurement range, excessive stress is applied to the diaphragm-like flexible portion, and the flexible portion may be damaged. There is. Therefore, the regulating plate is arranged with a predetermined interval above and below the weight portion of the sensor element. In this embodiment, an IC regulation plate 42, which is an IC chip on which a detection circuit is formed, is disposed above the weight portion, and the inner bottom of the case 1 is used as a regulation plate below the weight portion.
By using the IC regulation plate 42 and the inner bottom of the case 1, the thickness of the entire sensor can be made thinner than installing an independent regulation plate. The interval between the restriction plate and the weight portion is such that the weight portion does not collide with the restriction plate within the measurement range, and the weight portion collides with the restriction plate before the flexible portion is deformed so that the flexible portion is damaged. The intervals are as follows. In order to form the intervals with high accuracy, plastic balls having a substantially constant outer diameter are kneaded in the adhesive 16 so that the intervals can be regulated by using the plastic balls as spacers. Second diaphragm type triaxial acceleration sensor element 44 having a large measurement range
'May cause the flexible part not to be destroyed even when the assumed maximum acceleration is applied, in which case there is no restriction plate above and below the second diaphragm type triaxial acceleration sensor element 44'. Good. That is, the IC regulation plate 42 may be disposed in a region that covers the upper part of the first diaphragm type triaxial acceleration sensor element 44 and does not cover the upper part of the second diaphragm type triaxial acceleration sensor element 44 '.

A multi-range triaxial acceleration sensor according to the second embodiment of the present invention will be described below. FIG.
These show the structure of the multi-range sensor chip 51 of the second embodiment. The first diaphragm type triaxial acceleration sensor element 44 for measuring the low acceleration range of the first embodiment is changed to a beam type triaxial acceleration sensor element 45. The multi-range sensor chip 51 has a beam type triaxial acceleration sensor element 45 that measures a low acceleration range and a diaphragm type triaxial acceleration sensor element 44 that measures a high acceleration range. The diaphragm type triaxial acceleration sensor element 44 is
In the structure in which the weight portion 47 is supported by the flexible portion 48 in the frame portion 46, the beam-type triaxial acceleration sensor element 44 has the weight portion 11 in the frame portion 46 and the beam portion 12 including two pairs of two beams. Supported by.
An X-axis piezo 13, a Y-axis piezo 14, and a Z-axis piezo 15 were formed on the beam 12 as shown in FIG. The diaphragm type triaxial acceleration sensor element 44 is formed on one frame side of the frame portion 46 of the beam type triaxial acceleration sensor element 45. The frame portion 46, the weight portions 11 and 47, and the flexible portions 12 and 48 of the beam type triaxial acceleration sensor element 45 that measures the low acceleration range and the diaphragm type triaxial acceleration sensor element 44 that measures the high acceleration range are the same. The thickness was taken.

By making the flexible part of the triaxial acceleration sensor element into a beam shape, the bending rigidity of the flexible part was lowered, and the output per unit acceleration could be increased. Therefore, the output ratio per unit acceleration of the beam type triaxial acceleration sensor element 45 that measures the low acceleration range and the diaphragm type triaxial acceleration sensor element 44 that measures the high acceleration range is larger than that of the first embodiment. We were able to.

The third embodiment of the present invention is a multi-range acceleration sensor capable of detecting triaxial acceleration in three different acceleration ranges by further adding an acceleration detection range. A schematic structure of the multi-range sensor chip 52 is shown in FIG. In addition to the second diaphragm type triaxial acceleration sensor element 44 ′, a third diaphragm type triaxial acceleration sensor element 44 ″ is provided in the frame side of the frame portion 46 of the first diaphragm type triaxial acceleration sensor element 44. The first to third diaphragm type triaxial acceleration sensor elements 44, 44 ′, 44 ″ are arranged from the first to the third,
The output voltage with respect to the unit acceleration was decreased, and the acceleration measurement range was increased from the first to the third. For example, the first diaphragm type triaxial acceleration sensor element is ± 3G, the second diaphragm type triaxial acceleration sensor element is ± 30G, and the third diaphragm type triaxial acceleration sensor element is ± 600G. In order to reduce the output voltage with respect to the unit acceleration in order from the first to the third, the dimension of the weight portion was made smaller in order from the first to the third, and the length of the flexible portion was also made shorter.

In this embodiment, the first diaphragm type triaxial acceleration sensor element is square, the second diaphragm type triaxial acceleration sensor element 44 'is polygonal, and the third diaphragm type triaxial acceleration sensor element 44 "is circular. The shape of the frame portion 46 and the weight portion 47 is changed in accordance with the flexible portion, and the shape is not limited to a square shape, and a polygon or a circle can be selected. The diaphragm 46, the weight 47, and the flexible part 48 of the diaphragm type triaxial acceleration sensor element have the same thickness.

A multi-range triaxial acceleration sensor according to the fourth embodiment of the present invention will be described below. FIG.
The structure of the multi-range sensor chip 53 of Example 4 is shown. In this embodiment, a beam type triaxial acceleration sensor element 45 that measures a low acceleration range, two beam type biaxial acceleration sensors 61 that measure a medium acceleration range, and a diaphragm type triaxial acceleration that measures a 61 'high acceleration range. This is a configuration of the sensor element 44. The beam-type biaxial acceleration sensors 61 and 61 ′ connect the weight portion 62 and the frame portion 64 with a pair of beam portions 63. An X-axis piezo and a Z-axis piezo are formed on the beam portion 63 of the beam-type biaxial acceleration sensor 61, and a Y-axis piezo is formed on the beam portion 63 of the beam-type biaxial acceleration sensor 61 ′. The diaphragm type triaxial acceleration sensor element 44 and the two beam type biaxial acceleration sensor elements 61 and 61 ′ are formed on two frame sides of the frame portion 46 of the beam type triaxial acceleration sensor element 45.

The beam-type two-axis acceleration sensor elements 61 and 61 ′ are different from the beam-type three-axis acceleration sensor element 45 in that the pair of beam portions 63 is a pair. By a semiconductor piezoresistive element (not shown) formed in the beam portion 63, a first axis (X axis) which is the longitudinal direction of the beam portion 63 and a second axis (Z axis perpendicular to the chip surface) ) Acceleration can be detected. By arranging the two biaxial acceleration sensor elements so that the first axes are orthogonal to each other, the two axial directions of the two elements are 2
An axis (X axis and Y axis) and three axes of the Z axis can be detected. The detection of the Z axis may be performed by either one of the two elements, or both elements may be used. In this embodiment, the beam portion 62 of the first beam-type biaxial acceleration sensor element 61 is disposed along the X axis, and the X axis piezo and Z
An axial piezo was formed. Then, the beam portion 63 of the second beam-type biaxial acceleration sensor element 61 ′ is set to Y
A Y axis piezo was formed along the axis.

Since the beam type biaxial acceleration sensor element has a pair of beam portions, the total bending rigidity of the beam portion is smaller than that of the beam type triaxial acceleration sensor element having two pairs of beam portions, and the output voltage per unit acceleration is the same. The dimension of the weight part for making can be reduced. Since the beam also extends in only one direction, it could fit within a smaller frame.

A fifth embodiment of the present invention will be described. The overall configuration of the multi-range acceleration sensor is
The configuration is not limited to that shown in the first embodiment. An embodiment in which the wafer level packaging technology is applied to the multi-range sensor chip 41 will be described with reference to cross-sectional views of FIGS. As shown in FIG. 7, the first cap 7 is formed above and below the multi-range sensor chip 41.
0 and the second cap 71 were joined. The first cap 70 and the second cap 71 have a cavity 72 at the center, and joined to the multi-range sensor chip 41 at the periphery to obtain a sensor chip package 75. The joining portion was disposed on the frame portion 46 outside the sensor element portion forming region of the multi-range sensor chip 41. The sensor element portion is protected in an airtight package surrounded by the first cap 70 and the second cap 71, and suppresses fluctuations in the characteristics of the sensor element due to the influence of humidity and foreign matter.

The first cap 70 and the second cap 71 have an appropriate distance between the weight portion of the sensor element portion and the first cap 70 and the second cap 71, and when the excessive acceleration is applied, It acts as a regulating plate that regulates the amount of displacement and prevents the flexible part from being damaged. A chip protective film 73 is formed on the surface of the multi-range sensor chip 41, and the wiring 74 that connects the chip terminals 4 arranged outside the hermetic package and the piezoresistive element is provided under the chip protective film 73 from the outside of the hermetic package. To be pulled out. A silicon wafer was used for the first cap 70 and the second cap 71, and the cavity 72 was processed by anisotropic etching or dry etching of silicon. The multi-range sensor chip 41 and the first cap 70 and the second cap 71 were joined at the wafer level, and after the joining, the individual sensor chip packages 75 were separated. As a joining method, Au / Sn solder joining was used. In addition, solder bonding, eutectic bonding, surface activation bonding, anodic bonding, low melting point glass bonding, and the like of various metals can be used. Since it is necessary to expose the chip terminal 4 at the time of separation, a cavity 72 is formed in the upper region of the chip electrode in the first cap 70, and only the first cap 70 is indicated by an arrow. The chip terminal 4 was exposed by cutting at the first dicing section 76. Thereafter, the multi-range sensor chip 41 and the second cap 71 are connected to the second dicing unit 7.
7 was cut into individual pieces, and a sensor chip package 75 was obtained.

Since the sensor element part is protected in an airtight package, an inexpensive plastic package that is generally used is applied to the entire sensor package. An embodiment using a metal lead frame and resin sealing is shown in FIG. Chip support plate 7 of metal lead frame 85
The IC chip 80 was bonded onto the IC chip 80 with a resin adhesive 79, and the sensor chip package 75 was bonded onto the IC chip 80 with a resin adhesive 81. After the chip terminal 4 of the sensor chip package 75 and the IC terminal 82 of the IC chip 80 and between the IC terminal 82 and the external terminal 83 of the metal lead frame 85 are connected by the Au wire 5, an epoxy sealing resin is used. A multi-range acceleration sensor 88 was obtained.

It is a disassembled perspective view of the multi-range triaxial acceleration sensor of Example 1 of this invention. It is a perspective view of the multi-range sensor chip of Example 1 of the present invention. It is j-j 'sectional drawing of FIG. 1 of Example 1 of this invention. It is a perspective view of the multi-range sensor chip of Example 2 of this invention. It is a perspective view of the multi-range sensor chip of Example 3 of this invention. It is a perspective view of the multi-range sensor chip of Example 4 of the present invention. It is sectional drawing of the sensor chip package of Example 5 of this invention. It is sectional drawing of the multi-range acceleration sensor of Example 5 of this invention. It is a disassembled perspective view of the conventional triaxial acceleration sensor. FIG. 10 is a cross-sectional view of the conventional triaxial acceleration sensor taken along the line h-h ′ of FIG. 9 and a plan view of the sensor chip. It is a perspective view which shows the structure of the conventional multi-range acceleration sensor. It is a perspective view which shows the structure of the conventional multi-range acceleration sensor.

Explanation of symbols

1 case, 2 sensor chip,
3 Regulatory plate, 4 chip terminal,
5 wires, 6 case terminals,
7 External terminal, 8 Case lid,
9 Beam type triaxial acceleration sensor element, 9 'Diaphragm type triaxial acceleration sensor element,
10 frame, 11 weight,
12 beam, 13 X-axis piezo,
14 Y-axis piezo, 15 Z-axis piezo,
16, 17 Adhesive, 19 Diaphragm,
20 3-axis acceleration sensor, 21, 22, 23 acceleration sensor,
24 circuit board, 25 acceleration sensor device,
30 multi-range acceleration sensor, 31 frame,
32 beams, 33 weights,
34 electrodes, 40 multi-range acceleration sensors,
41 Multi-range sensor chip, 42 IC regulation plate,
43 IC terminal, 44, 44 ', 44 "diaphragm type triaxial acceleration sensor element,
45 Beam type triaxial acceleration sensor element, 46 Frame part,
47 weight parts, 48 flexible parts,
51, 52, 53 Multi-range sensor chip,
61, 61 'beam type biaxial acceleration sensor element, 62 weight part,
63 Beam, 64 Frame,
70 first cap, 71 second cap,
72 cavity, 73 chip protection film,
74 wiring, 75 sensor chip package,
76 1st dicing part, 77 2nd dicing part,
78 Chip support plate, 79 Adhesive,
80 IC chips, 81 adhesives,
82 IC terminals, 83 external terminals,
84 sealing resin, 85 metal lead frame,
88 Multi-range acceleration sensor.

Claims (13)

A surface having a frame, a weight portion held by the frame via the flexible portion, a semiconductor piezoresistive element provided in the flexible portion, and a wiring connecting them, on which the flexible portion is formed Multi-range triaxial acceleration having a multi-range sensor chip in which two or more diaphragm type triaxial acceleration sensor elements capable of detecting triaxial acceleration of an axis substantially perpendicular to the surface are formed on the same chip. The plurality of diaphragm type triaxial acceleration sensor elements of the multi-range sensor chip are characterized in that the output voltage per unit acceleration decreases in order from the first to the nth diaphragm type triaxial acceleration sensor element. Multi-range triaxial acceleration sensor. At least one triaxial acceleration sensor element of the first to nth diaphragm type triaxial acceleration sensor elements includes a frame portion, a weight portion held by the frame portion via two pairs of beam portions, and a beam portion. A multi-range triaxial acceleration sensor, which is replaced with a beam type triaxial acceleration sensor element having a semiconductor piezoresistive element provided on the substrate and wiring for connecting them. The first to n-th three-axis acceleration sensor elements of the multi-range sensor chip have second to n-th three in the at least one frame side of the frame part constituting the first three-axis acceleration sensor element. The multi-range triaxial acceleration sensor according to claim 1, wherein an axial acceleration sensor element is formed. 2. The thickness of the flexible part of all three-axis acceleration sensor elements is the same.
The multi-range triaxial acceleration sensor according to any one of 3 to 3. The multi-range triaxial acceleration sensor according to any one of claims 1 to 3, wherein all the triaxial acceleration sensor elements have the same thickness of the weight portion. The multi-range triaxial acceleration sensor according to any one of claims 1 to 3, wherein all the triaxial acceleration sensor elements have the same thickness and frame thickness. 4. The multi-range acceleration sensor according to claim 1, wherein the mass of the weight portion decreases in order from the first to the n-th diaphragm type triaxial acceleration sensor element. 4. The multi-range acceleration sensor according to claim 1, wherein a distance between the weight portion and the frame portion becomes shorter in order from the first to the n-th diaphragm type triaxial acceleration sensor element. 4. The multi-range acceleration sensor according to claim 1, wherein an area surrounded by a connection portion between the flexible portion and the frame portion decreases in order from the first to the n-th diaphragm type triaxial acceleration sensor element. . At least one of the second to n-th three-axis acceleration sensor elements includes a frame part, a weight part held by the frame part in a pair of beam parts, a semiconductor piezoresistive element provided in the beam part, and Two beam-type two-axis acceleration sensor elements capable of detecting the acceleration of the first axis in the plane on which the beam portion is formed and the second axis substantially perpendicular to the plane, 2. A three-axis acceleration sensor element formed by arranging the first axes so as to be orthogonal to each other.
Or the multi-range triaxial acceleration sensor of 2. 11. The multi-range triaxial acceleration sensor according to claim 10, wherein the thicknesses of the beam portions of all the beam type biaxial acceleration sensor elements and the flexible portions of the triaxial acceleration sensor elements are the same. The multi-range three-axis acceleration sensor according to claim 10, wherein the thicknesses of the weight portions of all the beam-type two-axis acceleration sensor elements and the three-axis acceleration sensor elements are the same. 11. The multi-range triaxial acceleration sensor according to claim 10, wherein the thicknesses of the weight portion and the frame portion of all the beam type biaxial acceleration sensor elements and the triaxial acceleration sensor elements are the same.

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