JP2008039664A - Multirange acceleration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a plurality of triaxial acceleration sensor having substantially different measurement ranges in a small area and at low cost and allow the directions of the acceleration detection axes of the plurality of sensors to coincide with each other with high precision. <P>SOLUTION: Within a frame section of a first triaxial acceleration sensor comprising the frame section, a weight section held by the frame section through two pairs of beam sections, and a semiconductor piezoresistive element provided on the beam sections, a second triaxial acceleration sensor is formed having a smaller output voltage per unit acceleration than that of the first triaxial acceleration sensor. Sharing the frame section can achieve downsizing, form them at once on one chip in processes such as photolithography and etching to reduce manufacturing costs, and allow the acceleration detection axes of the plurality of sensor elements to coincide with each other with high precision or with photolithographic mask precision. <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.

The applicant has filed a large number of applications regarding a 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. FIG. 11 is an exploded perspective view of the triaxial acceleration sensor, FIG. 12a) is a cross-sectional view in the hh ′ direction of FIG. 11, and FIG. 12b) is a plan view of the sensor chip. The three-axis acceleration sensor 20 has a sensor chip 2 in the case 1
The regulating plate 3 is fixed at a predetermined interval by an adhesive 16 such as a resin. The chip terminal 4 of the sensor chip 2 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 triaxial acceleration sensor element 9 is formed on the sensor chip 2. The triaxial acceleration sensor element 9 includes a beam portion 12 that forms a pair 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. 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 distance g4 between the lower surface of the weight part 11 and the inner bottom surface of the case 1 and the distance g3 between the upper surface of the weight part 11 and the regulating plate 3 are shown in FIG. 12a) when an excessive acceleration such as an impact is applied to the sensor. The amount of movement of the portion 11 is regulated to prevent the beam portion 12 from being damaged. Since the basic structure of the piezoresistive element type three-axis acceleration sensor of the present application is the same as those of these patent documents, detailed description will be 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

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. H11-228707 about a method for efficiently recording the history of impact acceleration in combination with the 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, it is difficult to obtain acceleration of several G and several hundred to several thousand G with high accuracy 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. 13 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 8 discloses a multi-range acceleration sensor that realizes downsizing and cost reduction and can eliminate the angular deviation of the detection axis. FIG. 14 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 is measured by a change in capacitance between the weight 33 and the electrode 34 arranged at a predetermined interval, and acceleration is detected. 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 8, since sensor elements having different measurement ranges are formed on a single chip, 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 8 is a uniaxial sensor element, in order to measure triaxial acceleration, it is necessary to dispose 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 using the multi-range one-axis acceleration sensor disclosed in Patent Document 8 is substantially the same as the conventional acceleration sensor device shown in FIG. 13 and the number, price, and size of the acceleration sensor. There is no big difference.

In the acceleration sensor structure of Patent Document 8, there is a risk 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 32
When acceleration is applied in the width direction, it is necessary to prevent other sensor elements and the weight 33 from colliding with each other, and it is necessary to consider such as opening the sensor elements.

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 two pairs of beams, a semiconductor piezoresistive element provided on the beam, and connecting them At least two or more triaxial acceleration sensor elements that can detect triaxial acceleration of two axes in the plane on which the beam portion is formed and an axis substantially perpendicular to the plane are formed on the same chip. A multi-range triaxial acceleration sensor having the multi-range sensor chip, wherein a plurality of triaxial acceleration sensor elements of the multirange sensor chip are output voltages per unit acceleration in order from the first to the n-th triaxial acceleration sensor element. Is preferably small.

In the three-axis acceleration sensor element, the beam part is deformed due to acceleration acting on the weight part, and stress is generated in the semiconductor piezoresistive element formed on the beam part to change the electric resistance. ) To output. The first to n-th triaxial acceleration sensor elements are formed so that the output voltage with respect to the unit acceleration decreases in order.

For example, a first triaxial acceleration sensor element with a measurement range of ± 3G has an output voltage of 1V per acceleration of 1G, and an nth triaxial acceleration sensor element with a measurement range of 300G has an output voltage of 0.01V per acceleration of 1G. Therefore, the full range of the output voltage corresponding to the measurement range of each triaxial acceleration sensor element can be adjusted to ± 3V, and if each ± 3V is detected with the same resolution, each of the different acceleration ranges is highly accurate. Detection is possible.

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 beam deformation may reach a non-linear region within the measurement range, and the linearity of the output voltage may not be maintained. There is.

The first to nth triaxial acceleration sensor elements are formed in the same chip. for that reason,
A separate 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.

Since the first to nth three-axis acceleration sensor elements are formed on the same chip surface,
It is possible to easily match the detection axis (Z axis) in the direction perpendicular to the chip surface with high accuracy.
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, if acceleration exceeding the measurement range occurs, the weight part will contact the restriction plate to restrict further displacement and prevent the beam part from being destroyed. And a highly reliable multi-range acceleration sensor can be realized.

The upper and lower regulation 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 may be used instead of the lower regulation plate.

By setting the distance between the weight portion of each triaxial acceleration sensor element and the regulating plate to be the same, the regulating plate may be flat and desirable in terms of ease of manufacture. In that case, for all three-axis acceleration sensor elements, the above-mentioned distance is such that the weight part does not collide with the restricting plate in the measurement range and the beam part does not break before the weight part collides with the restricting plate. To be. 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, with respect to some three-axis acceleration sensor elements in reverse order from the n-th measurement range, the control plates are arranged above and below the beam when there is no risk of damage to the beam due to the expected acceleration. It does not have to be.

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 that second to nth triaxial acceleration sensor elements are formed therein.

The triaxial acceleration sensor element is formed in a substantially square region, and four frame sides arranged on the four peripheral sides constitute a frame portion of the sensor element. By forming the second to nth triaxial acceleration sensor elements in the frame side of the first triaxial acceleration sensor element, each triaxial acceleration sensor element shares a frame portion, and a plurality of them are arranged in a small area. A three-axis acceleration sensor element in the range can be arranged. 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 beam portions 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 beam portion changes, the output voltage with respect to the unit acceleration changes sensitively. Therefore, it is desirable to form the beam portion with high accuracy. Therefore, SOI (Si) in which a thin silicon layer and a thick silicon layer are stacked via a silicon oxide film layer.
It is desirable to process using a silicon on insulator substrate. The silicon layer is processed by etching to form a beam portion in the thin silicon layer and a weight portion from the thin silicon layer to the thick silicon layer. In the multi-range triaxial acceleration sensor of the present application, it is not necessary to form beams having different thicknesses in the thin silicon layer by making the thickness of the beam portions of all the triaxial acceleration sensor elements the same. By using this thickness as it is, the beam portions of all the three-axis acceleration sensor elements can be formed at once by a single etching, and the number of manufacturing steps can be reduced and the cost can be reduced.

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.

Similar to the beam part, the weight part has the same thickness in all three-axis acceleration sensor elements, so that the thickness part of all the three-axis acceleration sensor elements can be etched once by using the thickness of the thick silicon layer as it is. Since it can be formed in a lump, the number of manufacturing steps can be reduced and the cost can be reduced.

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.

By using the same thickness for the weight and frame, the thickness and thickness of the thick silicon layer can be used as they are to form the weight and the frame in a single etching process, reducing the number of manufacturing steps and reducing costs. Can be.

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, the length of the beam portion is preferably shortened in order from the first to the nth triaxial acceleration sensor element.

By shortening the length of the beam portion, the bending rigidity of the beam portion is increased. Therefore, the stress generated in the beam portion with respect to the unit acceleration is reduced, and the output voltage with respect to the unit acceleration can be reduced.

In the multi-range triaxial acceleration sensor of the present invention, the width of the beam portion is preferably increased in order from the first to the nth triaxial acceleration sensor element.

Since the bending rigidity of the beam portion is increased by reducing the width of the beam portion widely, the stress generated in the beam portion with respect to the unit acceleration is reduced, and the output voltage with respect to the unit acceleration can be reduced. In the multi-range three-axis acceleration sensor of the present invention, since it is desirable to make the thickness of the beam portion the same because they are collectively formed on the same chip, as described above, the length of the beam portion is shortened or the width is reduced. It is desirable to increase the bending rigidity of the beam portion.

In the multi-range triaxial acceleration sensor of the present invention, it is preferable that the distance between the end portions connected to the frame portions of the beam portions forming a pair becomes smaller in order from the first to the nth triaxial acceleration sensor element.

The distance between the ends connected to the frame portion of the beam portion forming a pair is the size of the inner region of the frame portion, in other words, the size occupied in the chip surface of the triaxial acceleration sensor element. The smaller the dimensions, the smaller the dimensions of the weight part and the shorter the length of the beam part, so the force acting on the weight part becomes smaller, the bending rigidity of the beam part becomes higher, and the output voltage per unit acceleration. Can be reduced.

In the multi-range triaxial acceleration sensor of the present invention, at least one of the second to nth triaxial acceleration sensor elements includes a frame portion and a weight portion held by the frame portion with a pair of beam portions, A semiconductor piezoresistive element provided in the beam section and wiring connecting them, and detecting the acceleration of the first axis in the plane where the beam section is formed and the second axis approximately perpendicular to the plane Two possible biaxial acceleration sensor elements are preferably arranged such that the first axes are orthogonal to each other.

The two-axis acceleration sensor element is different from the three-axis acceleration sensor element in that a pair of beam portions form a pair. The semiconductor piezoresistive element formed on the beam portion can detect the acceleration of the first axis (X axis) which is the longitudinal direction of the beam portion and the second axis (Z axis) perpendicular to the chip surface. By arranging the two biaxial acceleration sensor elements so that the first axes are orthogonal to each other, two axes (X and Y axes) which are the first axial directions of the two elements 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. On the other hand, the triaxial acceleration sensor element has two pairs of beam portions orthogonal to each other, two axes (X and Y axes) which are the longitudinal directions of the respective beam portions, and an axis (Z axis) perpendicular to the chip surface. ) Acceleration can be detected. The detection of the Z axis may be performed by either one of the two beam pairs or both.

Since the biaxial acceleration sensor element has a pair of beam portions, the total bending rigidity of the beam portion is smaller than that of the triaxial acceleration sensor element having two pairs of beam portions, so that the output voltage per unit acceleration is the same. The size of the weight portion can be reduced. Since the beam portion also extends in only one direction, it can be accommodated in a smaller frame portion. The total of the two elements has a larger area than the triaxial acceleration sensor element, but the second and subsequent acceleration sensor elements are two biaxial elements and are arranged around the first triaxial acceleration sensor having the largest dimension. Thus, the overall dimensions of the multi-range acceleration sensor element can be reduced. That is, the first three-axis acceleration sensor element has one element for three axes, and the second and subsequent three-axis acceleration sensor elements have one element for three axes or two biaxial acceleration sensor elements. Is possible.

Each beam portion of the two 2-axis acceleration sensor elements is the same as that of the other 3-axis acceleration sensor elements.
By arranging them in parallel with the two beam portions, it is possible to detect accelerations in different ranges without misalignment.

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

Even in the above-described configuration using the biaxial acceleration sensor element, by making the beam portions of all the triaxial acceleration sensor elements and the biaxial acceleration sensor elements have the same thickness, beams having different thicknesses can be formed on the thin silicon layer. Since there is no need to form, the thickness of the thin silicon layer can be used as it is, and the beam portions of all the elements can be formed in one batch by one etching, and the number of manufacturing steps can be reduced and the cost can be reduced.

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

Like the beam part, the weight part has the same thickness in all three-axis acceleration sensor elements and two-axis acceleration sensor elements, so that the thickness of the thick silicon layer can be used as it is, and the weight parts of all the elements are Since it can be formed collectively by etching, the number of manufacturing steps can be reduced and the cost can be reduced.

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

By using the same thickness for the weight and frame, the thickness and thickness of the thick silicon layer can be used as they are to form the weight and the frame in a single etching process, reducing the number of manufacturing steps and reducing costs. Can be.

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, it is possible to easily make the distance between the lower surface of the weight and the regulating plate the same for all three-axis acceleration sensor elements and two-axis acceleration sensor elements.

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.

The multi-range acceleration sensor according to the first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a development view of the multi-range acceleration sensor of the first embodiment, and FIG. 2 is an enlarged view of the multi-range sensor chip. 3 is a cross-sectional view taken along the line hh ′ of FIG. In FIG. 1, a multi-range acceleration sensor 40 includes a multi-range sensor chip 41 in which sensor elements are formed, and an IC regulation plate 42 in which a detection circuit is formed and serves to regulate the movement of the sensor elements. 1 and was sealed with an alumina case lid 8. The chip terminal 4 of the multi-range sensor chip 41 and 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 are connected by the wire 5, so that the detection signal of the sensor is taken out from the external terminal 7.

As shown in FIG. 3, the multi-range sensor chip 41 was fixed to the inner bottom of the case 1 using the first adhesive 16. The first adhesive 16 is kneaded with plastic balls, and a certain distance is formed between the weight portion of the sensor element and the inner bottom of the case 3. Similarly, the IC restricting plate 42 is adhered onto the multi-range sensor chip 41 by the first adhesive 16 in which plastic balls are kneaded, so that a certain distance is formed between the weight portion of the sensor element and the IC restricting plate 42. I made it. The case lid 8 was fixed to the case 1 with the second adhesive 17 and sealed to form the 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 includes a first 3-axis acceleration sensor element 44 and a second 3-axis acceleration sensor element 45.
Is formed. The first triaxial acceleration sensor element 44 includes a first element first beam portion 48 and a first element second beam portion, each of which includes a first element weight portion 47 formed of two beams in a first element frame portion 46. 49. When the X-axis and Y-axis are set in the plane direction of the multi-range sensor chip 41 and the Z-axis is set in the vertical direction, the piezoelectric element for detecting the acceleration in the X-axis direction is formed on the first element first beam portion 48 formed along the X-axis. The Y-axis piezo 14 for detecting the acceleration in the Y-axis direction was formed on the first element second beam portion 49 in which the X-axis piezo 13 as the resistance element was formed along the Y-axis. The Z-axis piezo 15 for detecting the Z-axis acceleration may be on either beam portion, but here the first element first beam portion 48 is used.
Formed on top. Four piezoresistive elements were formed for each axis and connected by wiring not shown to constitute a bridge circuit. By applying force to the weight part due to acceleration and displacing it, the beam part is deformed, 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.

Similarly, the second triaxial acceleration sensor element 45 has a second element weight portion 51 in the second element frame portion 50.
Are supported by a second element first beam portion 52 and a second element second beam portion 53 each consisting of two beams. An X-axis piezo and a Z-axis piezo were formed on the second element first beam portion 52 along the X axis, and a Y-axis piezo was formed on the second element second beam portion 53 along the Y axis.

The second triaxial acceleration sensor element 45 has a smaller output voltage per unit acceleration than the first triaxial acceleration sensor element 44. That is, the measurement range of the second triaxial acceleration sensor element 45 is wider than the full scale of the output voltage. For example, the measurement range of the first 3-axis acceleration sensor element 44 is set to ± several G, and is used for drop detection.
The measurement range of the axial acceleration sensor element 45 can be set to ± several hundred G and used for impact detection. A plurality of chip terminals 4 are formed on the multi-range sensor chip.

The manufacturing method and dimensional relationship of the acceleration sensor element will be briefly described. An SOI (Silicon having a silicon oxide layer of several μm and a silicon layer of 6 μm on a silicon plate having a thickness of about 400 μm.
on Insulator) 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 layer and the silicon plate were processed using a photolithography and dry etching apparatus, and the shape of the beam portion formed in the silicon layer and the weight portion formed from the silicon layer to the silicon plate were created. 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 three-axis acceleration sensor element 44
Further, the second triaxial acceleration sensor element 45 can be collectively formed on one multi-range sensor chip 41. 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, since the second three-axis acceleration sensor element 45 is formed on one of the four frame sides constituting the frame part 46 of the first three-axis acceleration sensor element 44, the frame parts of the two sensor elements are shared. Can be accommodated in a small area, and the multi-range acceleration sensor can be miniaturized. Further, 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.

The schematic dimension of the multi-range sensor chip 41 of the first embodiment is shown. In the first triaxial acceleration sensor element 44, the length of one beam of the beam portion is 400 μm, the width is 40 μm, and the weight portion has an outer dimension of 900 × 900 μm. In order to keep the weight part and the beam part in a small area, the weight part was formed in a shape in which the connection part of the beam part was hollowed out. As a result, the weight portion has a clover shape as shown in FIG. The second triaxial acceleration sensor element 45 has a beam length of 120 μm and a width of 100 μm.
The external dimensions of the weight portion were 200 × 200 μm. For the second 3-axis acceleration sensor element,
Since the area reduction effect by making the weight into a clover shape is small, the weight was made square. The thickness of the beam is the thickness of the silicon layer of the SOI wafer for both the two sensor elements.
The weight of the two sensor elements was the total thickness of the SOI wafer, and was 407 μm because the silicon oxide film layer was 1 μm.

At this time, the output voltage for the acceleration 1G when the input voltage is 3 V is about 2.0 mV for the X, Y, and Z axes in the first three-axis acceleration sensor element 44, and the X and Y axes in the second three-axis acceleration sensor element 45. Was about 0.015 mV, and the Z-axis was about 0.01 mV. Comparing the output voltages, the first three-axis acceleration sensor element 44 is about 200 times larger than the Z-axis having a large difference. When amplification is performed with the same amplification factor by the amplifier circuit and the full-scale output voltage is the same, the measurement range of the first 3-axis acceleration sensor element 44 is the second 3-axis acceleration sensor element 4.
1/20 of 5 For example, amplification factor is 150 times, full-scale output voltage is ± 900mV
Then, the measurement range is ± 3G for the first 3-axis acceleration sensor element 44, and ± 600G for the second 3-axis acceleration sensor element 45. With the multi-range acceleration sensor as described above, 1
When measuring accelerations of various intensities from small accelerations below G to large accelerations of several hundred G, the ± 3G range is the first triaxial acceleration sensor element 44, and the ± 600G range is the second triaxial acceleration. Each sensor element 45 could be measured with good linearity.

In order to reduce the output voltage per unit acceleration of the second triaxial acceleration sensor element 45 as compared to the first triaxial acceleration sensor element 44 as in the above dimension example, the length of the beam is shortened.
It is desirable to increase the beam rigidity by increasing the beam width. It is also desirable to reduce the external dimensions of the weight and reduce the weight of the weight. Accordingly, it is desirable that the second triaxial acceleration sensor element 45 is smaller in the region where the weight portion and the beam portion are arranged. That is, it is desirable that the space area inside the frame portion is reduced, that is, the distance connecting the connection points of the two beams of the beam portion with the frame portion is reduced.

Further, the resonance frequency when the sensor element having the above dimensions is about 1.5 kHz for the first triaxial acceleration sensor element 44 and about 25 kHz for the second triaxial acceleration sensor element 45. In the case of detection of impact acceleration, if vibration near the resonance frequency of the acceleration sensor is applied to the acceleration sensor due to the impact of the collision of the device equipped with the sensor, the vibration at the resonance frequency remains without being attenuated. There is a risk of problems in the waveform. Therefore, it is necessary to increase the resonance frequency in impact detection. Second triaxial acceleration sensor element 4 for measuring the high acceleration range
No. 5 has a feature that it is easy to use for impact detection since the bending frequency of the beam is high and the weight of the weight is reduced, so that the resonance frequency of the sensor element is also high.

If the first triaxial acceleration sensor element 44 that measures the low acceleration range is given acceleration that greatly exceeds the measurement range, an excessive stress is applied to the beam, and the beam may be damaged. Therefore, the restriction plates are arranged above and below the weight portion of the sensor element with a certain interval. In this example,
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. The thickness of the entire sensor can be reduced as compared with the case where an independent restriction plate is provided separately from the IC restriction plate 42 and the case 1. 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 beam is deformed so that the beam is damaged. To do. In this embodiment, the thickness is 15 μm. In order to form the interval with high accuracy, a plastic ball having a substantially constant outer diameter is kneaded in the first adhesive 16 so that the interval can be regulated by using the plastic ball as a spacer. The second triaxial acceleration sensor element 45 having a large measurement range may not cause the beam to be broken even when the assumed maximum acceleration is applied. There may be no board. That is, the IC regulation plate 42 covers the upper part of the first triaxial acceleration sensor element 44,
The upper part of the second triaxial acceleration sensor element 45 may be arranged in a region not covered.

A multi-range triaxial acceleration sensor according to the second embodiment of the present invention will be described below. FIG. 4 shows the structure of the multi-range sensor chip 41 of the second embodiment. Second 3 in the first embodiment
The difference is that the axial acceleration sensor element 45 is composed of two biaxial acceleration sensor elements.
As in the first embodiment, the multi-range sensor chip 41 includes a first element weight portion 47, a first element first beam portion 48 made up of two beams, and a first element frame portion 46 in the first element frame portion 46. The first triaxial acceleration sensor element 44 having a structure supported by the element second beam portion 49 is included. On the other hand, the second triaxial acceleration sensor element 45 includes a second element first weight part 57 in the second element first frame part 56,
In the first biaxial acceleration sensor element 54 having a structure supported by the second element first beam portion 58 composed of two beams, and the second element second weight portion 60 in the second element second frame portion 59, It comprised from the 2nd 2-axis acceleration sensor element 55 of the structure supported by the 2nd element 2nd beam part 61 which consists of two beams.

The two-axis acceleration sensor element is different from the three-axis acceleration sensor element in that a pair of beam portions form a pair. The semiconductor piezoresistive element formed on the beam portion can detect the acceleration of the first axis (X axis) which is the longitudinal direction of the beam portion and the second axis (Z axis) perpendicular to the chip surface. By arranging the two biaxial acceleration sensor elements so that the first axes are orthogonal to each other, two axes (X axis and Y axis) which are the first axial directions of the two elements, and three of the Z axis An 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 the present embodiment, the second element first beam portion 58 of the first biaxial acceleration sensor element 54 is disposed along the X axis to form an X axis piezo and a Z axis piezo. And the 2nd element 2nd beam part 61 of the 2nd biaxial acceleration sensor element 55 was arrange | positioned along the Y-axis, and the Y-axis piezo was formed.

Since the biaxial acceleration sensor element has a pair of beam portions, the total bending rigidity of the beam portion is smaller than that of the triaxial acceleration sensor element having two pairs of beam portions, so that the output voltage per unit acceleration is the same. The size of the weight portion can be reduced. Since the beam portion extends only in one direction, it can be accommodated in a smaller frame portion. The total of the two elements has a larger area than the triaxial acceleration sensor element, but the second and subsequent acceleration sensor elements are two biaxial elements, and the first 3 having the largest dimension.
By disposing within the frame side of the axial acceleration sensor, the overall dimensions of the multi-range acceleration sensor element can be reduced. That is, the first three-axis acceleration sensor element has one element for three axes, and the second and subsequent three-axis acceleration sensor elements have one element for three axes or two biaxial acceleration sensor elements. Is possible.

The schematic dimension of the multi-range sensor chip of 2nd Example is shown. The first triaxial acceleration sensor element 44 is the same as that of the first embodiment. The first biaxial acceleration sensor element 54 and the second biaxial acceleration sensor element 55 have the same dimensions, the beam length is 120 μm, the width is 100 μm, and the external dimensions of the weight portion are 150 × 150 μm. At this time, the acceleration is 1G when the input voltage is 3V.
The output voltage for is about 2.0 mV for X, Y and Z in the first triaxial acceleration sensor element.
In the first and second biaxial acceleration sensor elements, X, Y, and Z were about 0.01 mV.
The first and second biaxial acceleration sensor elements have a weight shape smaller than the weight shape of the first triaxial acceleration sensor element of the first embodiment, and the output voltages per unit acceleration can be made equal.
According to the first embodiment, the first and second biaxial acceleration sensor elements having the above dimensions are arranged in one frame side of the frame portion of the first triaxial acceleration sensor element as shown in FIG. Even the size of the entire multi-range sensor chip could be reduced.

As shown in FIG. 5, the third embodiment uses first and second biaxial acceleration sensor elements 54 and 55 similar to those of the second embodiment, and the frame side of the frame portion of the first triaxial acceleration sensor element 44. Two of them were arranged respectively. The first biaxial acceleration sensor element 54 in which the beam portion is arranged in the X direction is a second biaxial acceleration sensor in which the beam portion is arranged in the Y direction within the frame side parallel to the X axis of the first three axis acceleration sensor 44. The element 55 is arranged in a frame side parallel to the Y axis of the first triaxial acceleration sensor element 54. In the first and second biaxial acceleration sensor elements, the overall dimension of the first and second biaxial acceleration sensor elements becomes longer in the longitudinal direction of the beam portion. This configuration is desirable for this purpose. In other words, when the multi-range sensor chip is formed in a substantially square shape, it can be arranged in the minimum area in this embodiment.

In the fourth embodiment, an acceleration detection range is further added to form a multi-range acceleration sensor that can detect triaxial acceleration in three different ranges. A schematic structure of the multi-range sensor chip is shown in FIG. The second 3-axis acceleration sensor element 45 and the third 3-axis acceleration sensor element 62 are arranged in the frame side of the frame portion of the first 3-axis acceleration sensor element 44 similar to the first embodiment. From the first to the third, the output voltage per unit acceleration was made smaller. Then, the acceleration measurement range is increased in the order from the first to the third. For example, the first is ±
3G, second is ± 30G, third is ± 600G. In order to reduce the output voltage per unit acceleration in order from the first to the third, the dimension of the weight part is made to decrease in order from the first to the third, and the length of the beam part is shortened and the width is increased. I did it.

The second and third triaxial acceleration sensor elements 45 and 63 may be composed of two biaxial acceleration sensor elements. For example, in the fifth embodiment, as shown in FIG. 7, the third triaxial acceleration sensor element 62 includes a first biaxial acceleration sensor element 54 that detects X and Z axis accelerations, and Y
The second acceleration sensor element 55 is configured to detect axial acceleration. Together with the second triaxial acceleration sensor element 45, the first biaxial acceleration sensor element 54 is disposed within the frame side along the X axis of the frame portion of the first triaxial acceleration sensor element 55. Was placed in another frame side along the Y axis.

In the sixth embodiment shown in FIG. 8, the second 3-axis acceleration sensor element 45 includes a first 2-axis acceleration sensor element 54 that detects X and Z-axis accelerations, and a second 2-axis acceleration that detects Y-axis acceleration. Similarly, the sensor device 55 includes a third 3-axis acceleration sensor element 62, a third 2-axis acceleration sensor element 63 for detecting X and Z-axis accelerations, and a fourth 2-axis acceleration sensor for detecting Y-axis acceleration. The element 64 is configured. First and third biaxial acceleration sensor elements 54
And 63 in the frame side along the X-axis of the frame portion of the first triaxial acceleration sensor element 44, and the second and fourth biaxial acceleration sensor elements 45 and 64 in the first triaxial acceleration sensor element 44. It arrange | positioned in the frame side along the Y-axis of a frame part.

The multi-range acceleration sensor of the second to sixth embodiments also uses a three-axis acceleration sensor element suitable for the acceleration intensity for various intensity accelerations from 1G or less to several hundreds G, and within the measurement range. It was possible to measure well.

The overall configuration of the multi-range acceleration sensor of the present invention is not limited to the configuration shown in the first embodiment. A seventh embodiment in which wafer level packaging is applied to the multi-range sensor chip 41 will be described using the cross-sectional views of FIGS. 9 and 10. As shown in FIG. 9, the first cap 70 and the second cap 71 are joined to the top and bottom of the multi-range sensor chip 41. The first cap 70 and the second cap 71 have a cavity 72 in the center, and are joined to the multi-range sensor chip 41 at the periphery. The joint is disposed outside the sensor element formation region of the multi-range sensor chip 41, and thus the sensor element is protected in an airtight package surrounded by the first cap 70 and the second cap 71, and is affected by humidity, foreign matter, and the like. The characteristics of the sensor element were not changed.

In addition, there is an appropriate distance between the weight part of the sensor element and the first cap 70 and the second cap 71, and when excessive acceleration is applied, the displacement of the weight part is restricted and the beam part is damaged. It acts as a regulation board to prevent. A chip protection film 73 is formed on the surface of the multi-range sensor chip 41, and the wiring 74 that connects the chip terminal 6 disposed outside the hermetic package and the piezoresistive element is provided under the chip protection film 73 from the outside of the hermetic package. To be pulled out. For the first cap 70 and the second cap 71, a silicon wafer was used, and the cavity 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 and eutectic bonding of various metals, surface activated bonding, anodic bonding, low melting point glass bonding, and the like can be used. Since it is necessary to expose the chip electrode at the time of singulation, a cavity is formed in the upper region of the chip electrode in the first cap, and only the first cap 70 is formed by the first dicing portion 76. By cutting, the chip electrode 6
Exposed. Thereafter, the multi-range sensor chip 41 and the second cap 71 were cut into pieces by the second dicing part 77.

Since the sensor element is protected in an airtight package, an inexpensive plastic package that is generally used can be applied to the entire sensor package. A configuration example using a metal lead frame and resin sealing is shown in FIG. The IC chip 80 was bonded to the chip support plate 78 of the metal lead frame 85 with a first adhesive 79 made of resin, and the sensor chip package 75 was bonded to the IC chip 80 with a second adhesive 81 made of resin. And after connecting between the chip terminal 6 of the sensor chip package 75, the IC terminal 82 of the IC chip 80, and the IC terminal 82 and the external terminal 83 of the metal lead frame 85 by the Au wire 5, Sealed with a sealing resin 84.

It is a perspective view which shows the whole structure of the multi-range acceleration sensor of a 1st Example. It is a perspective view which shows the structure of the multi-range sensor chip of a 1st Example. It is h-h 'sectional drawing of FIG. It is a perspective view which shows the structure of the multi-range sensor chip of 2nd Example. It is a perspective view which shows the structure of the multi-range sensor chip of 3rd Example. It is a perspective view which shows the structure of the multi-range sensor chip of 4th Example. It is a perspective view which shows the structure of the multi-range sensor chip of 5th Example. It is a perspective view which shows the structure of the multi-range sensor chip of 6th Example. It is sectional drawing which shows the structure of the sensor chip package of 7th Example. It is sectional drawing which shows the whole structure of the multi-range acceleration sensor of 7th Example. It is a perspective view which shows the whole structure of the conventional triaxial acceleration sensor. It is h-h 'sectional drawing of FIG. 11, and the top view of a 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 3-axis acceleration sensor element, 10 frame part,
11 weight, 12 beam,
13 X-axis piezo, 14 Y-axis piezo,
15 Z-axis piezo, 16 First adhesive,
17 Second adhesive, 20 3-axis acceleration sensor,
21 acceleration sensor for several G, 22 acceleration sensor for several 10G,
23 Accelerometer for hundreds of G, 24 circuit board,
25 acceleration sensor device, 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 first triaxial acceleration sensor element,
45 second triaxial acceleration sensor element, 46 first element frame,
47 1st element weight part, 48 1st element 1st beam part,
49 1st element 2nd beam part, 50 2nd element frame part,
51 2nd element weight part, 52 2nd element 1st beam part,
53 2nd element 2nd beam part, 54 1st biaxial acceleration sensor element,
55 2nd axis acceleration sensor element, 56 2nd element 1st frame part,
57 second element first weight part, 58 second element first beam part,
59 second element second frame part, 60 second element second weight part,
61 2nd element 2nd beam part, 62 3rd triaxial acceleration sensor element,
63 third biaxial acceleration sensor element, 64 fourth biaxial acceleration sensor element,
70 first cap, 71 second cap,
72 cavity, 73 chip protective film,
74 wiring, 75 sensor chip package,
76 1st dicing part, 77 2nd dicing part,
78 Chip support plate, 79 First adhesive,
80 IC chip, 81 second adhesive,
82 IC terminals, 83 external terminals,
84 Sealing resin, 85 Metal lead frame.

Claims (13)

The beam portion is formed by having a frame portion, a weight portion held by the frame portion via two pairs of beam portions forming a pair, a semiconductor piezoresistive element provided in the beam portion, and wiring connecting them. Multi-range triaxial acceleration having a multi-range sensor chip in which two or more triaxial acceleration sensor elements capable of detecting triaxial acceleration of two axes in the plane and an axis substantially perpendicular to the plane are formed on the same chip A plurality of three-axis acceleration sensor elements of the multi-range sensor chip;
The multi-range triaxial acceleration sensor is characterized in that the output voltage per unit acceleration decreases in order up to the triaxial acceleration sensor element. 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. The multi-range triaxial acceleration sensor according to claim 1 or 2, wherein all the triaxial acceleration sensor elements have the same thickness of the beam portion. The multi-range triaxial acceleration sensor according to claim 1 or 2, wherein all the triaxial acceleration sensor elements have the same thickness of the weight portion. 3. The multi-range triaxial acceleration sensor according to claim 1, wherein the thicknesses of the weight portion and the frame portion of all the triaxial acceleration sensor elements are the same. 3. 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 three-axis acceleration sensor element. 3. The multi-range acceleration sensor according to claim 1, wherein the length of the beam portion decreases in order from the first to the n-th three-axis acceleration sensor element. 3. The multi-range acceleration sensor according to claim 1, wherein the width of the beam portion increases in order from the first to the n-th three-axis acceleration sensor element. 3. The multi-range acceleration sensor according to claim 1, wherein the distance between the end portions connected to the frame portions of the beam portions forming a pair decreases in order from the first to the n-th 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 biaxial acceleration sensor elements capable of detecting acceleration of a first axis in a plane on which a beam portion is formed and a second axis substantially perpendicular to the plane. 3. The multi-range triaxial acceleration sensor according to claim 1, wherein the multirange triaxial acceleration sensor is configured by a triaxial acceleration sensor element that is arranged so that the axes thereof are orthogonal to each other. The multi-range three-axis acceleration sensor according to claim 10, wherein all the biaxial acceleration sensor elements and the three-axis acceleration sensor elements have the same beam thickness. 11. The multi-range triaxial acceleration sensor according to claim 10, wherein the thicknesses of the weight portions of all the biaxial acceleration sensor elements and the triaxial acceleration sensor elements are the same. 11. The multi-range triaxial acceleration sensor according to claim 10, wherein all the biaxial acceleration sensor elements and the triaxial acceleration sensor elements have the same thickness and frame thickness.

Images