JP2007256236A - Acceleration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acceleration sensor that can reduce or prevent degradation in the detection accuracy and reduce, or prevent occurrence of interference with surrounding parts or the like. <P>SOLUTION: The x axis is set in the height method of cross sections of the first and second cantilever sections 2 and 3, x=0 is set at the upper ends of the cross sections of the cantilever sections 2 and 3; x=h is set at the lower ends of the cross sections of the cantilever sections 2 and 3, and the widths of the cross sections of the cantilever sections 2 and 3 are set to be W(x). At this time, the sectional shapes of the cantilever sections 2 and 3 are set so that W(x) ≤ W(0) or W (x) ≤ W(h) are established in the range of 0<x<h; and there exist (a) that establishes W(a) < W(0) and W(a) < W(h) which are established in the range of 0<a<h. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an acceleration sensor mainly used in a car navigation system such as an automobile, a vehicle control system, or a camera shake detection system such as a camera.

  An acceleration sensor is known in which a weight is provided at the tip of a cantilever and a piezoresistive element is formed on the upper surface of the cantilever, and the acceleration is detected by detecting a change in the resistance value of the piezoresistive element. And the thing of the structure which provided the two cantilever part and the weight part is well-known (refer patent document 1).

In addition, in an acceleration sensor that detects biaxial acceleration, the cross-sectional shape of the cantilever portion is a triangle with the surface on which the piezoresistive element is formed as the bottom surface, or the alphabet with the surface on which the piezoresistive element is formed as the upper surface. The “T” shape is also known (see Patent Document 2).
Japanese Patent Laid-Open No. 4-130276 JP-A-8-160067

  Factors that influence the performance improvement of the acceleration sensor include sensitivity and the magnitude of output change, but in order to improve the sensitivity, the rigidity of the cantilever part holding the weight part may be reduced, In this case, it is an effective method to reduce the width of the cantilever portion in the direction in which acceleration is detected.

  On the other hand, in order to increase the output change, it is only necessary to increase the distortion of the piezoresistive element even if the bending of the cantilever is the same. For this purpose, a method of reducing the rigidity of the cantilever However, other than that, it is also effective to form a piezoresistive element in a place where the strain is the largest in the cantilever portion. Among the cantilever portions, the place with the largest strain is the root portion of the cantilever portion in the length direction of the cantilever portion. Further, in the width direction of the cantilever portion, it is the portion farthest from the neutral surface of the cantilever. This corresponds to the side surface of the cantilever portion located in the acceleration detection direction. However, since it is difficult to form a piezoresistive element on this side, particularly when performing a thin film formation method, it is practical to form the piezoresistive element at the upper or lower end of the cantilever portion. It is. In this case, if the width of the cantilever portion is increased in order to increase the output change, the distortion of the piezoresistive element is increased accordingly, but if the width of the cantilever portion is increased, the rigidity is improved. Sensitivity is lowered.

  Patent Document 2 discloses a configuration in which the cross-sectional shape of the cantilever portion is a triangle, or an alphabetic “T” shape having a surface on which a piezoresistive element is formed as an upper surface, although the purpose is different. In this configuration, it is considered possible to reduce the rigidity of the cantilever portion and increase the distortion of the piezoresistive element.

  However, in the case of such a cross-sectional shape, since the rigidity of the upper surface portion of the cantilever is high and the rigidity of the lower surface portion is low, the deflection on the upper surface side is small when acceleration is applied, and the deflection on the lower surface side is small. In this way, the cantilever part not only bends in the direction in which the acceleration is applied, but also changes in the direction perpendicular to the direction in which the acceleration is applied, such as bending and twisting, resulting in a decrease in detection accuracy. It leads to inviting. In addition, since the weight portion is deformed in a direction perpendicular to the direction in which the acceleration is applied, there is a concern about interference between the weight portion and surrounding components.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide an acceleration sensor that can reduce or prevent deterioration of detection accuracy and can also reduce or prevent the occurrence of interference with surrounding components. To do.

  In order to achieve the above object, the present invention has the following configuration.

  According to the first aspect of the present invention, there is provided a fixed portion, a cantilever portion connected to the fixed portion, a weight portion formed at a tip of the cantilever portion, and the cantilever portion. An acceleration sensor that includes a piezoresistive element formed on an upper surface, and detects acceleration by bending the cantilever portion to the left and right, and sets an x-axis in a height direction of a cross section of the cantilever portion; When the upper end of the cross section of the cantilever portion is x = 0, the lower end of the cross section of the cantilever portion is x = h, and the width of the cross section of the cantilever portion is W (x), the piece When the cross-sectional shape of the cantilever portion is 0 <x <h, W (x) ≦ W (0) or W (x) ≦ W (h) is established, and W (a) <W (0) and W ( a) <W (h) is satisfied and 0 <a <h is present, and according to this configuration, the cross-sectional shape of the cantilever portion , 0 <x <h, W (x) ≦ W (0) or W (x) ≦ W (h) holds, and W (a) <W (0) and W (a) <W (h) Since the shape of a <0 <a <h exists, the width of the upper surface of the cantilever portion can be increased, thereby increasing the distortion of the piezoresistive element and changing the output. Since there is a portion between the upper surface and the lower surface of the cantilever portion that is narrower than the width of the upper surface and the width of the lower surface, the rigidity of that portion will be reduced. , The sensitivity can be improved, and the lower surface width is wider than the narrowest part of the cross-sectional width of the cantilever part, so that the rigidity of the lower surface part can be improved, thereby reducing the decrease in detection accuracy. It has the effect that it can aim at.

  In the invention according to claim 2 of the present invention, in particular, the cross-sectional shape of the cantilever portion is configured to be vertically symmetrical. According to this configuration, the rigidity of the cantilever portion is vertically symmetrical. When acceleration is applied in the direction, it is theoretically no longer that the cantilever part bends or twists in the direction perpendicular to the applied direction, thereby preventing the detection accuracy from being lowered. It is what has.

  The invention according to claim 3 of the present invention is particularly configured such that the cross-sectional shape of the cantilever portion is symmetrical, and according to this configuration, when acceleration in a direction perpendicular to the detection direction is applied. Since the cantilever portion does not bend in the detection direction, there is an effect that it is possible to prevent erroneous detection in such a case.

  In the invention according to claim 4 of the present invention, in particular, the cross section of the weight portion has a rectangular parallelepiped shape. According to this configuration, the width is narrower than the upper end and the lower end at the center of the cross section of the cantilever portion. Since the cross section of the weight part has a rectangular parallelepiped shape, the rigidity of the cantilever part can be reduced without reducing the mass of the weight part. The effect is that the sensitivity can be improved.

  In the invention according to claim 5 of the present invention, in particular, a plurality of cantilever portions and weight portions are connected to the fixed portion, and according to this configuration, a full bridge circuit can be configured. This has the effect of being able to obtain a large output change.

  As described above, the acceleration sensor according to the present invention includes the fixed portion, the cantilever portion connected to the fixed portion, the weight portion formed at the tip of the cantilever portion, and the upper surface of the cantilever portion. An acceleration sensor that detects acceleration by bending the cantilever portion to the left and right, and sets the x-axis in the height direction of the cross section of the cantilever portion, When the upper end of the cross section of the cantilever portion is x = 0, the lower end of the cross section of the cantilever portion is x = h, and the width of the cross section of the cantilever portion is W (x), the cantilever When the cross-sectional shape of the beam portion is 0 <x <h, W (x) ≦ W (0) or W (x) ≦ W (h) is established, and W (a) <W (0) and W (a ) <W (h) is satisfied so that 0 <a <h exists so that the output change becomes large and the sensitivity is improved. It is intended to achieve the excellent effect that can be, and it is possible to reduce the lowering of detection accuracy.

(Embodiment 1)
Hereinafter, the invention described in the first, third, fourth, and fifth aspects of the present invention will be described using the first embodiment.

  FIG. 1 is a plan view of an acceleration sensor according to Embodiment 1 of the present invention, and FIG. 2 is a cross-sectional view of a cantilever portion of the acceleration sensor.

  In FIG. 1, reference numeral 1 denotes a fixing portion, and the fixing portion 1 is formed from a substrate made of Si. Reference numeral 2 denotes a first cantilever part formed on the fixed part 1, and reference numeral 3 denotes a second cantilever part formed on the fixed part 1 so as to be aligned with the first cantilever part 2. Reference numeral 4 denotes a first weight portion formed at the tip of the first cantilever portion 2, and reference numeral 5 denotes a second weight portion formed at the tip of the second cantilever portion 3. The part 5 is formed so as to be aligned with the first weight part 4. The cross sections of the first weight portion 4 and the second weight portion 5 are each a rectangular parallelepiped shape.

  The fixed portion 1, the first cantilever portion 2, the second cantilever portion 3, the first weight portion 4 and the second weight portion 5 are integrally formed on the same plane. It is. Further, the first cantilever part 2 and the first weight part 4, and the second cantilever part 3 and the second weight part 5 are arranged in the same direction. The one cantilever part 2 and the second cantilever part 3, and the first weight part 4 and the second weight part 5 are configured to have the same shape.

  Reference numerals 6 and 7 respectively denote a first piezoresistive element and a second piezoresistive element formed on the upper surface of the first cantilever part 2, and 8 and 9 denote an upper surface of the second cantilever part 3. A third piezoresistive element and a fourth piezoresistive element. The first piezoresistive element 6, the second piezoresistive element 7, the third piezoresistive element 8 and the fourth piezoresistive element 9 all have a characteristic that the resistance value changes when distortion occurs. It is what.

  Reference numeral 10 denotes a first application electrode formed on the fixed part 1, 11 denotes a first intermediate electrode formed on the fixed part 1, and 12 denotes a first ground electrode formed on the fixed part 1. The first piezoresistive element 6 is electrically connected between the first application electrode 10 and the first intermediate electrode 11, and the second piezoresistive element 7 is connected to the first intermediate electrode 11 and the first intermediate electrode 11. It is electrically connected to one ground electrode 12.

  Reference numeral 13 denotes a second application electrode formed on the fixed part 1, reference numeral 14 denotes a second intermediate electrode formed on the fixed part 1, and reference numeral 15 denotes a second ground electrode formed on the fixed part 1. The third piezoresistive element 8 is electrically connected between the second ground electrode 15 and the second intermediate electrode 14, and the fourth piezoresistive element 9 is connected to the second intermediate electrode 14 and the second intermediate electrode 14. And the application electrode 13 are electrically connected.

  Reference numeral 16 denotes a conductor that electrically connects the piezoresistive elements of the first piezoresistive element 6 to the fourth piezoresistive element 9 and the electrodes of the first application electrode 10 to the second ground electrode 15. Wiring.

  In the acceleration sensor according to the first embodiment of the present invention described above, the first application electrode 10 and the second application electrode 13 are set to the same potential, and the first ground electrode 12 and the second ground electrode 15 are set to the same potential. The full-bridge circuit is configured, and the circuit configuration is performed so as to detect the differential output between the first intermediate electrode 11 and the second intermediate electrode 14, and the first piezo in the state where no acceleration is applied. The resistance values of the resistive element 6 to the fourth piezoresistive element 9 are made equal.

  FIG. 2 shows only a cross section of the first cantilever portion 2, but the first cantilever portion 2 and the second cantilever portion 3 have the same cross-sectional shape.

  In FIG. 2, the X axis is a coordinate axis in which the upper end of the cross section of the first cantilever part 2 and the second cantilever part 3 is 0 and the vertical downward direction is positive. Therefore, the upper ends of the cross sections of the first cantilever part 2 and the second cantilever part 3 are X = 0. The lower end of the cross section of the first cantilever part 2 and the second cantilever part 3 is X = h.

  W (X) is the width of the cross section of the first cantilever part 2 and the second cantilever part 3 at the point X on the X coordinate. Therefore, the width of the upper end of the cross section of the first cantilever portion 2 and the second cantilever portion 3 is W (0), and the width of the lower surface portion is W (h). a is a point where 0 <a <h on the X-axis, and W (a) indicates the width of the cross section at point a.

  In the cross-sectional view shown in FIG. 2, as shown, the bottom surface of the triangle is the upper end of the cross section of the first cantilever part 2 and the second cantilever part 3, and a rectangle is attached to the apex part of the triangle. The configuration of the shape. In other words, the first cantilever part 2 and the second cantilever part 3 have a configuration in which the width of the upper surface and the lower surface of the cross section is widened and a portion having a narrow cross section width is provided between the upper surface and the lower surface. It has become.

When the cross-sectional view shown in FIG.
For 0 <x <h,
W (x) ≦ W (0) or W (x) ≦ W (h) holds,
In a <0 <a <h,
W (a) <W (0) and W (a) <W (h)
Is a.

  Thus, since the area | region which can form the 1st piezoresistive element 6-the 4th piezoresistive element 9 can be enlarged by the width | variety of an upper surface, arrangement | positioning of these resistive elements is easy. Furthermore, since the displacement in the first cantilever portion 2 and the second cantilever portion 3 is small at the center of the width of the upper surface and the displacement at the end is the largest, each of these resistance elements has The generated distortion can also be increased. As a result, the resistance value change of each resistance element becomes large, so that a large output change can be obtained.

  In addition, since the width of the central portion in the vertical direction is narrowed, the rigidity is lowered and the film is easily bent, thereby improving the sensitivity.

  In addition, since the width of the end portion of the lower surface is increased, the balance of the vertical direction of the cross section can be improved compared to the case where the end portion of the lower surface is as narrow as the central portion, and thereby the lateral direction of the paper surface Since it is possible to reduce vertical deflection and torsion of the first cantilever beam portion 2 and the second cantilever beam portion 3 due to acceleration with respect to the acceleration, it is useful for preventing a decrease in detection accuracy of the acceleration sensor. .

  A method for manufacturing the acceleration sensor configured as described above will be briefly described below.

  A resistance layer constituting each of the first to fourth piezoresistive elements 6 to 9 is formed on the upper surface of the substrate made of Si by a thin film method such as sputtering, and then the first applied electrode 10 is formed. A metal layer constituting each electrode of the second ground electrode 15 and the wiring 16 is formed by a thin film method such as sputtering, and the metal layer is formed into a predetermined shape by etching. Each electrode of the ground electrode 15 and the wiring 16 can be formed. Finally, by processing the substrate into a predetermined shape by etching, the fixed portion 1, the first cantilever portion 2, the second cantilever portion 3, the first weight portion 4 and the second weight of the predetermined shape An acceleration sensor having the part 5 is obtained.

  In addition, the cross-sectional shape of the 1st cantilever part 2 and the 2nd cantilever part 3 which are shown in FIG. 2 can be obtained by performing an etching from both surfaces of a surface side and a back surface side. FIG. 2 shows the characteristics of the cross-sectional shape of the first cantilever portion 2 in an easy-to-understand manner, and the corners and corners in FIG. 2 are actually curved. Also, the vertical and horizontal lines in FIG. 2 are actually not vertical or horizontal lines but inclined.

  The operation of the acceleration sensor configured and manufactured as described above will be described below.

  In FIG. 1, for example, when a positive acceleration is applied in the right direction on the paper surface, the first cantilever portion 2 and the first weight portion 4 and the second weight portion 5 are inclined so that the first weight portion 4 and the second weight portion 5 are inclined leftward. The second cantilever part 3 bends. At this time, the first piezoresistive element 6 and the third piezoresistive element 8 are distorted in the compression direction, and the second piezoresistive element 7 and the fourth piezoresistive element 9 are distorted in the tensile direction. . Here, since the first cantilever part 2 and the second cantilever part 3 and the first weight part 4 and the second weight part 5 are formed in the same shape, the first cantilever part The distortion of the beam part 2 and the second cantilever part 3 is the same. As a result, the resistors at the diagonal positions constituting the full bridge circuit have the same resistance value, so that the differential output of the first intermediate electrode 11 and the second intermediate electrode 14 is twice that of the half bridge circuit. Output change.

  As described above, the acceleration sensor according to the first embodiment of the present invention includes the fixed portion 1, the first cantilever portion 2 and the second cantilever portion 3 connected to the fixed portion 1, and the first A first weight part 4 and a second weight part 5 formed at the ends of one cantilever part 2 and a second cantilever part 3, and the first and second cantilever parts 2 and 2 A first piezoresistive element 6 to a fourth piezoresistive element 9 formed on the upper surface of the cantilever part 3, and the first cantilever part 2 and the second cantilever part 3 are In the acceleration sensor for detecting the acceleration by bending the first cantilever part 2 and the second cantilever part 3, the x-axis is set in the height direction of the cross section of the first cantilever part 2 and the first cantilever part 3. The upper ends of the cross sections of the beam portion 2 and the second cantilever beam portion 3 are x = 0, and the first cantilever beam portion 2 and the second cantilever beam portion 3 are disconnected. X = h and the width of the cross section of the first cantilever part 2 and the second cantilever part 3 is W (x), the first cantilever part 2 and When the cross-sectional shape of the second cantilever portion 3 is 0 <x <h, W (x) ≦ W (0) or W (x) ≦ W (h) is established, and W (a) <W ( 0) and W (a) <W (h) is satisfied, and the shape is such that 0 <a <h exists, so the first cantilever part 2 and the second cantilever part 3 The width of the upper surface of the cross section of the first piezoresistive element 6 to the fourth piezoresistive element 9 can be increased to increase the output change. Since the upper surface and the lower surface of the cantilever part 2 and the second cantilever part 3 have a portion narrower than the width of the upper surface and the lower surface, the rigidity of the portion decreases. Thus, the sensitivity can be improved, and the width of the lower surface is wider than the narrowest portion of the cross-sectional width of the first cantilever portion 2 and the second cantilever portion 3, It is possible to improve the rigidity of the lower surface portion, thereby reducing the decrease in detection accuracy.

  The cross sections of the first weight part 4 and the second weight part 5 have a rectangular parallelepiped shape. In this case, the center of the cross section of the first cantilever part 2 and the second cantilever part 3 is used. Since the first weight part 4 and the second weight part 5 have a rectangular parallelepiped shape, the first weight part has a rectangular parallelepiped shape while lowering the rigidity by providing portions with a width narrower than the upper end and the lower end. The rigidity of the first cantilever part 2 and the second cantilever part 3 can be reduced without reducing the mass of the 4 and second weight parts 5, thereby improving the sensitivity. It is something that can be done.

  In addition, the cantilever portion has a plurality of first cantilever portions 2 and second cantilever portions 3, and the weight portion has a plurality of first weight portions 4 and second weight portions 5. Therefore, a full bridge circuit can be configured, and thereby a large output change can be obtained.

  Furthermore, since the cross-sectional shapes of the first cantilever part 2 and the second cantilever part 3 are configured to be bilaterally symmetric, acceleration is applied in a direction perpendicular to the detection direction, that is, the vertical direction in FIG. In this case, it is theoretically no longer that the first cantilever part 2 and the second cantilever part 3 are bent or twisted in the direction perpendicular to the application direction, that is, in the left-right direction in FIG. Thereby, it is possible to prevent a decrease in detection accuracy.

  Furthermore, the first piezoresistive element 6 and the second piezoresistive element 7 are formed at the same distance and opposite to the neutral surface of the first cantilever portion 2, and the second piezoresistive element 7 is formed in the same manner. Since the third piezoresistive element 8 and the fourth piezoresistive element 9 are formed equidistantly and oppositely to the neutral surface of the cantilever part 3 of the cantilever part 3, the neutrality is obtained when acceleration is applied. The absolute value of the expansion of one piezoresistive element and the shrinkage of the other piezoresistive element with respect to the surface are equal, and the absolute value of each change in resistance value is also equal. By adopting the circuit configuration to be taken out, the output change can be increased.

  Since the first cantilever part 2, the second cantilever part 3, the first weight part 4 and the second weight part 5 are arranged in the same direction on the same plane, Thus, the formation positions of the piezoresistive elements 6 to 9 are close to each other, whereby the variation in characteristics of the piezoresistive elements 6 to 9 can be reduced.

  Further, the first cantilever part 2 and the second cantilever part 3 and the first weight part 4 and the second weight part 5 are formed in the same shape. Since the beam portion 2 and the second cantilever beam portion 3 are subjected to the same deformation, and these components are arranged in the same direction on the same plane, the first weight portion 4 and the second cantilever portion 3 The weight parts 5 do not contact and do not interfere with each other. In this case, in reality, the first cantilever portion 2 and the second cantilever portion 3 do not undergo the same deformation due to variation in manufacturing shape, variation in internal composition, and the like. Therefore, if the distance between the first weight part 4 and the second weight part 5 is narrow in a state where no acceleration is applied, the first weight part 4 and the second weight part 5 may come into contact with each other. . However, in the case of the acceleration sensor according to Embodiment 1 of the present invention, as described above, the first weight portion 4 and the second weight portion 5 are less likely to come into contact with each other and interfere with each other. The distance between the 4 and the second weight portion 5 can be narrowed, whereby the acceleration sensor as a whole can be reduced in size.

  In the acceleration sensor according to Embodiment 1 of the present invention described above, the first piezoresistive element 6 to the fourth piezoresistive element 9 having the same resistance value have been described. Of the first piezoresistive element 6 and the second piezoresistive element 7 so that the potential of the first piezoresistive element 6 and the potential of the second intermediate electrode 14 change in opposite directions with respect to the respective reference potentials. The ratio between the resistance value and the ratio between the resistance value of the fourth piezoresistive element 9 and the resistance value of the third piezoresistive element 8 may be made equal.

  The relationship between W (0) and W (h) is W (0) = W (h), but it may be W (0)> W (h). On the other hand, W (0) <W (h) may be satisfied, but W (0) ≧ W (h) is preferable in that the width of the upper surface for forming the piezoresistive element can be increased. .

  In addition, the cross sections of the first weight part 4 and the second weight part 5 are formed in a rectangular parallelepiped shape, but the side surfaces of the first weight part 4 and the second weight part 5, that is, the first weight part 5. The shape of the side end in the cross section of the weight part 4 and the second weight part 5 can be the same as that of the first cantilever part 2 and the second cantilever part 3. In this case, the masses of the first weight part 4 and the second weight part 5 are reduced, and the sensitivity is reduced accordingly. However, the first weight part 4, the second weight part 5, the first weight are reduced by etching. Since the process of forming the cantilever part 2 and the second cantilever part 3 can be formed in one process, the manufacturing is simplified.

(Embodiment 2)
Hereinafter, the invention described in the second to fourth aspects of the present invention will be described using the second embodiment.

  FIG. 3 is a cross-sectional view of the cantilever portion of the acceleration sensor according to Embodiment 2 of the present invention. 4 to 7 are cross-sectional views showing variations of the cantilever portion of the acceleration sensor.

  The acceleration sensor according to the second embodiment of the present invention is different from the acceleration sensor according to the first embodiment of the present invention described above in that the cross-sectional shape of the cantilever is further symmetrically configured. As shown in FIGS. 3 to 7, the acceleration sensor according to the second embodiment of the present invention is configured such that the cross-sectional shape of the first cantilever portion 2 is vertically symmetrical. 3 to 7, only the first cantilever part 2 is shown, but the cross-sectional shape of the second cantilever part 3 is the same as the cross-sectional shape of the first cantilever part 2. It is what has become.

  In the acceleration sensor according to the second embodiment of the present invention described above, the cross-sectional shapes of the first cantilever part 2 and the second cantilever part 3 are configured to be symmetrical in the vertical direction. As a result, it is possible to theoretically eliminate the vertical bending and twisting of the first cantilever part 2 and the second cantilever part 3 due to the acceleration in the lateral direction of the paper. A decrease in detection accuracy of the sensor can be prevented.

  In addition, the manufacturing method of the acceleration sensor in Embodiment 2 of this invention is the same as the manufacturing method of the acceleration sensor in Embodiment 1 of the said invention, The 1st cantilever part 2 and the 2nd cantilever The cross-sectional shape of the portion 3 can be obtained by performing etching from both the front surface side and the back surface side, and can be changed to each shape by changing the etching conditions. is there.

(Embodiment 3)
FIG. 8 is a plan view of the acceleration sensor according to Embodiment 3 of the present invention.

  In the third embodiment of the present invention, the same components as those of the first embodiment of the present invention described above are denoted by the same reference numerals, description thereof will be omitted, and only different points will be described.

  The acceleration sensor according to the third embodiment of the present invention is different from the acceleration sensor according to the first embodiment of the present invention described above in that the first cantilever portion 2, the second cantilever portion 3, and the first weight. The first stopper portion 17, the second stopper portion 18, and the connecting portion 19 that surround the periphery of the portion 4 and the second weight portion 5 together with the fixing portion 1 are formed.

  In FIG. 8, reference numeral 17 denotes a first stopper portion formed on the outer side of the fixed portion 1 where the first cantilever portion 2 is formed so as to face the first weight portion 4 with a space in between. The first stopper portion 17 is formed integrally with the fixed portion 1. Reference numeral 18 denotes a second stopper portion formed outside the portion of the fixed portion 1 where the second cantilever portion 3 is formed so as to face the second weight portion 5 with a space in between. The two stopper portions 18 are formed integrally with the fixed portion 1. Reference numeral 19 denotes a connecting portion that connects the first stopper portion 17 and the second stopper portion 18. The first stopper portion 17, the second stopper portion 18 and the connecting portion 19 are obtained when the substrate made of Si is etched.

  In the above-described third embodiment of the present invention, the first stopper portion 17 and the second stopper portion 18 are provided so as to face the first weight portion 4 and the second weight portion 5 with a space in between. Therefore, when an excessive acceleration is applied, the first weight portion 4 comes into contact with the first stopper portion 17 or the second weight portion 5 comes into contact with the second stopper portion 18 and the first weight portion 4 comes into contact with the first stopper portion 17. Since the cantilever portion 2 or the second cantilever portion 3 can be prevented from being excessively bent, the acceleration sensor can be prevented from being damaged when an excessive acceleration is applied. It is.

  In Embodiment 3 of the present invention, since the first stopper portion 17 and the second stopper portion 18 are connected by the connecting portion 19, the first stopper portion 17 and the second stopper portion 18 are connected. Accordingly, the deformation of the first stopper portion 17 and the second stopper portion 18 due to the contact of the first weight portion 4 or the second weight portion 5 can be reduced. Therefore, the first stopper portion 17 and the second stopper portion 18 can efficiently exhibit the stopper function.

(Embodiment 4)
FIG. 9 is a plan view of an acceleration sensor according to Embodiment 4 of the present invention.

  In the fourth embodiment of the present invention, the same components as those in the third embodiment of the present invention described above are denoted by the same reference numerals, description thereof will be omitted, and only different points will be described.

  The difference between the acceleration sensor according to the fourth embodiment of the present invention and the acceleration sensor according to the third embodiment of the present invention described above is that an extending portion is added.

  In FIG. 9, reference numeral 20 denotes an extending part formed so as to face the first cantilever part 2 or the second cantilever part 3 with a space in between, and this extending part 20 is a first weight. It is formed so as to be integral with the part 4 or the second weight part 5 and to extend to the fixed part 1 side. In addition, the extended portion 20 is formed at two locations on the first weight portion 4 and at two locations on the second weight portion 5, and the shape of these four extended portions 20 is the target. It is configured in the shape or the same shape.

  In addition, the extended portion 20 is spaced from the first cantilever portion 2, spaced from the second cantilever portion 3, spaced from the fixed portion 1, and spaced from the first stopper portion 17. In addition, the intervals between the second stopper portion 18 and the second stopper portion 18 are all equal, the interval between the first weight portion 4 and the first stopper portion 17, and the second weight portion 5 and the second stopper portion 18. The distance between the first weight part 4 and the connecting part 19, the distance between the first weight part 4 and the connecting part 19, and the distance between the first weight part 4 and the second weight part 5 as well. All are configured to be equal. That is, the distances of the space portions surrounded by the fixed portion 1, the first stopper portion 17, the second stopper portion 18, and the extending portion 20 are all configured to be equal.

  As described above, in the fourth embodiment of the present invention, the extending portion 20 is formed so as to face the first cantilever portion 2 or the second cantilever portion 3 across the space, and this Since the extending portion 20 is formed so as to extend integrally from the first weight portion 4 or the second weight portion 5 to the fixed portion 1 side, the presence of the extending portion 20 causes the first portion Since the mass of the first weight part 4 and the second weight part 5 connected to the cantilever part 2 and the second cantilever part 3 increases, the first piece is applied when the same acceleration is applied. The bend of the cantilever portion 2 and the second cantilever portion 3 is increased, thereby improving the sensitivity of the acceleration sensor.

  Further, in order to increase the mass of the first weight part 4 and the second weight part 5 while reducing the external dimensions, the first cantilever is used in order not to provide the extension part 20. Although it becomes necessary to shorten the length of the part 2 and the 2nd cantilever part 3, when the extension part 20 is provided, the necessity does not arise. In the acceleration sensor having such a configuration, if the masses of the first weight part 4 and the second weight part 5 are the same, the lengths of the first cantilever part 2 and the second cantilever part 3 are the same. The longer the length, the greater the distortion in the base portion of the first cantilever portion 2 and the second cantilever portion 3, that is, in the vicinity of the connection portion with the fixed portion 1, thereby improving the sensitivity as an acceleration sensor. To do. Therefore, the acceleration sensor according to Embodiment 4 of the present invention can also improve sensitivity from this point.

  In Embodiment 4 of the present invention, the distances of the space portions surrounded by the fixing portion 1, the first stopper portion 17, the second stopper portion 18 and the extending portion 20 are all made equal. Therefore, the fixing portion 1, the first cantilever portion 2, the second cantilever portion 3, the first weight portion 4, the second weight portion 5, the first stopper portion 17, and the second stopper are provided. When the substrate made of Si is processed by etching in order to form the portion 18, the connecting portion 19 and the extending portion 20 in a predetermined shape, the substrate 18 can be processed with high accuracy, thereby improving the detection accuracy of the acceleration sensor. It is possible to improve.

  In the acceleration sensor according to Embodiment 4 of the present invention, the first stopper portion 17, the second stopper portion 18 and the connecting portion 19 are provided together with the extending portion 20, but the extending portion Even when only 20 is provided and the first stopper part 17, the second stopper part 18 and the connecting part 19 are not provided, the sensitivity of the acceleration sensor can be improved.

  Each of the above-described acceleration sensors according to the first to fourth embodiments of the present invention has a configuration including two cantilever portions and two weight portions. The acceleration sensor having such a configuration has superior effects in terms of strength and output as compared with a configuration having only one weight portion and one cantilever portion. That is, increasing the strain at the cantilever portion is an effective method for increasing the output, but if the strain becomes too large, the cantilever portion may be damaged. On the other hand, in the configuration with two cantilever parts and two weight parts, the output from each cantilever part is doubled by taking the differential of each output by a full bridge circuit etc. Therefore, even if the distortion at the cantilever part is half, the final output can be equivalent to one with one weight part and one cantilever part. The output can be improved while maintaining a sufficient strength. In this case, if the variation in characteristics such as resistance values of the piezoresistive elements formed on the two cantilever portions increases, the detection accuracy decreases. However, in the acceleration sensor of the present invention, the two cantilevers are Since the beam portions are arranged in the same direction on the same plane, the distance between the two is short, thereby making it possible to reduce variations in the characteristics of the piezoresistive elements, thereby improving detection accuracy. .

  In the acceleration sensor according to the present invention, the x-axis is set in the height direction of the cross section of the cantilever part connected to the fixed part, the upper end of the cross section of the cantilever part is x = 0, and the cantilever part When the lower end of the cross section is x = h and the width of the cross section of the cantilever part is W (x), the cross-sectional shape of the cantilever part is W (x) when 0 <x <h. ≦ W (0) or W (x) ≦ W (h) is satisfied, and there is a where 0 <a <h where W (a) <W (0) and W (a) <W (h) are satisfied Therefore, it is possible to obtain an acceleration sensor capable of improving detection accuracy, such as a car navigation system such as an automobile, a vehicle control system, or a camera shake detection system such as a camera. It is useful when applied to an acceleration sensor used in the above.

The top view of the acceleration sensor in Embodiment 1 of this invention Cross section of the cantilever part of the acceleration sensor Sectional drawing of the cantilever part of the acceleration sensor in Embodiment 2 of this invention Cross section of variation of cantilever part of the same acceleration sensor Cross section of variation of cantilever part of the same acceleration sensor Cross section of variation of cantilever part of the same acceleration sensor Cross section of variation of cantilever part of the same acceleration sensor Plan view of acceleration sensor according to Embodiment 3 of the present invention Plan view of acceleration sensor according to Embodiment 4 of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixed part 2 1st cantilever part 3 2nd cantilever part 4 1st weight part 5 2nd weight part 6 1st piezoresistive element 7 2nd piezoresistive element 8 3rd piezo Resistive element 9 Fourth piezoresistive element

Claims (5)

A fixed portion; a cantilever portion connected to the fixed portion; a weight portion formed at a tip of the cantilever portion; and a piezoresistive element formed on the cantilever portion. In an acceleration sensor that detects acceleration by bending the cantilever part to the left and right, an x axis is set in the height direction of the cross section of the cantilever part, and the upper end of the cross section of the cantilever part is x = 0, When the lower end of the cross section of the cantilever portion is x = h and the width of the cross section of the cantilever portion is W (x), the cross-sectional shape of the cantilever portion is 0 <x <h , W (x) ≦ W (0) or W (x) ≦ W (h) holds, and W (a) <W (0) and W (a) <W (h) hold 0 <a < An acceleration sensor having a shape such that h is a. The acceleration sensor according to claim 1, wherein the cross-sectional shape of the cantilever portion is vertically symmetrical. The acceleration sensor according to claim 1 or 2, wherein the cross-sectional shape of the cantilever portion is symmetrical. The acceleration sensor according to any one of claims 1 to 3, wherein a cross section of the weight portion is formed in a rectangular parallelepiped shape. The acceleration sensor according to any one of claims 1 to 4, wherein a plurality of cantilever portions and weight portions are connected to the fixed portion.

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