JP2010071850A - Acceleration sensor element, acceleration sensor device and method for manufacturing acceleration sensor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a miniaturizable acceleration sensor element while maintaining sensitivity. <P>SOLUTION: The sensor element 20 is provided with: a weight unit 11 having a recessed part 11a; a frame-shaped fixing part 13 surrounding the weight unit 11; a beam 12 with one end connected to the fixing part 13 and the other end connected to the weight unit 11; a resistor element 15 arranged at the beam 12; and a weight member 22 that consists of a material with greater specific gravity than the material of the weight unit 11, buried in the recessed part 11a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an acceleration sensor element, an acceleration sensor device, and a method for manufacturing the acceleration sensor element.

An acceleration sensor device that detects acceleration using a piezoresistance effect is known (for example, Patent Document 1). The acceleration sensor device of Patent Document 1 includes a weight portion, a beam portion that supports the weight portion, a fixing portion that supports the beam portion, and a piezoresistive element provided in the beam portion. When an external force proportional to the acceleration is applied to the acceleration sensor device, the weight portion is displaced with respect to the fixed portion, and bending deformation occurs in the beam portion. Then, the acceleration is detected by detecting a change in the resistance value of the piezoresistive element in which the bending deformation occurs together with the beam portion.
JP 2003-172745 A

  In the acceleration sensor device described above, the larger the weight portion, the heavier the weight portion, the greater the deflection of the beam portion with respect to the acceleration, and the higher the acceleration detection sensitivity. However, in this case, since the weight portion becomes large, it is difficult to reduce the size of the acceleration sensor device.

  An object of the present invention is to provide an acceleration sensor element and an acceleration sensor device that can be miniaturized while maintaining sensitivity, and a method of manufacturing such an acceleration sensor element.

  The acceleration sensor element according to the present invention includes a weight portion having a recess, a frame-shaped fixing portion surrounding the weight portion, a beam having one end connected to the fixing portion and the other end connected to the weight portion. Part, a resistance element that is provided in the beam part and has a resistance value that changes in accordance with the bending of the beam part, a weight member that is made of a material having a specific gravity greater than that of the weight part, and is embedded in the recess, Have

  The acceleration sensor device of the present invention includes any one of the acceleration sensor elements described above and an IC chip that performs signal processing on an output signal of the acceleration sensor element.

  The acceleration sensor element manufacturing method of the present invention includes a step A for forming a resistor element on one principal surface of a substrate, a beam portion in which the resistor element is disposed by processing the substrate, and one end of the beam portion. And a step B of forming a weight part having a recess that is open on one main surface side, and a fixing part that is connected to the other end of the beam part and surrounds the weight part, and the material of the substrate in the recess And a step C of filling a weight member made of a material having a higher specific gravity.

  According to the acceleration sensor element of the present invention, the weight portion has the concave portion, and the weight member made of a material having a specific gravity greater than that of the weight portion material is embedded in the concave portion. Therefore, the weight portion has the same size. When compared with the conventional one, the weight portion of the acceleration sensor element of the present invention is heavier, so that the detection sensitivity can be improved without increasing the size of the acceleration sensor element. Alternatively, when compared with the conventional sensor that has the same detection sensitivity according to the size of the weight part, the acceleration sensor element of the present invention can make the weight part small, and thus can be downsized while maintaining the detection sensitivity. An acceleration sensor element can be provided.

  According to the acceleration sensor device of the present invention using such an acceleration sensor element of the present invention, the overall structure of the device can be reduced in size while maintaining detection sensitivity.

  Further, according to the method for manufacturing an acceleration sensor element of the present invention, it is possible to manufacture an acceleration sensor element with improved detection sensitivity without increasing the size or an acceleration sensor element reduced in size while maintaining the detection sensitivity.

  Exemplary embodiments of an acceleration sensor device and a method for manufacturing the acceleration sensor device according to the present invention will be described below in detail with reference to the drawings. Note that the drawings used in the following embodiments are schematic, and the dimensional ratios in the drawings do not necessarily match the actual ones. Further, the present invention is not limited to the following embodiments, and various changes and improvements can be made without departing from the gist of the present invention. In this embodiment, a three-dimensional acceleration sensor device using the piezoresistance effect will be described as an example.

<Acceleration sensor device>
1 is a perspective view of the acceleration sensor device according to the present embodiment, FIG. 2 is a plan view of the acceleration sensor device of FIG. 1 with the lid 10 removed, and FIG. 3 is a cross-sectional view of the acceleration sensor device shown in FIG. 3A corresponds to a cross section taken along the line AA ′ in FIG. 2, and FIG. 3B corresponds to a cross section taken along the line BB ′ in FIG. As shown in these drawings, the acceleration sensor device according to the present embodiment is mainly composed of a substrate 1 and a sensor element 20.

  First, the sensor element 20 will be described. FIG. 4 is a perspective view of the sensor element 20. As shown in FIG. 4, the sensor element 20 includes a weight portion 11, a frame-shaped fixing portion 13 surrounding the weight portion 11, one end connected to the fixing portion 13, and the other end connected to the weight portion 11. It has a beam portion 12, an element-side electrode pad 14 formed on the fixed portion 13, and a resistance element 15 formed on the beam portion 12.

  When acceleration is applied to the sensor element 20, a force corresponding to the acceleration acts on the weight part 11, and the beam part 12 is bent as the weight part 11 moves. The weight part 11 in the present embodiment is provided with four attached weight parts 21 connected to the four corners thereof. The attached weight portion 21 is formed integrally with the weight portion 11, and by providing the attached weight portion 21, the bending of the beam portion 12 with respect to acceleration increases, and the detection sensitivity of acceleration can be improved. In addition, the weight part 11 and the attached weight part 21 whole may be regarded as a weight part. Moreover, since the structure, function, and formation method of the weight part 11 and the attached weight part 21 are the same or similar, description of the attached weight part 21 may be abbreviate | omitted below.

  The weight portion 11 has a substantially square planar shape, and the length of one side thereof is set to, for example, 0.25 mm to 0.5 mm. Moreover, the thickness of the weight part 11 is set to 0.2 mm-0.625 mm, for example. The attached weight portion 21 has a substantially square shape in the same manner as the weight portion 11, and the length of one side thereof is set to 0.1 mm to 0.4 mm, for example. Moreover, the thickness of the attached weight part 21 is set to 0.2 mm-0.625 mm so that it may have the same thickness as the weight part 11, for example. In addition, the thickness of the attached weight part 21 may be thinner than the thickness of the weight part 11, for example, may be 5 to 10 μm thinner than the thickness of the weight part 11. The planar shape of the weight part 11 and the attached weight part 21 is not limited to a square, and can be any shape such as a circle or a rectangle. The weight part 11 and the attached weight part 21 are integrally formed by processing an SOI (Silicon on Insulator) substrate 27, for example.

  A frame-shaped fixing portion 13 is formed so as to surround the weight portion 11 and the attached weight portion 21. The fixed portion 13 has a substantially square opening, and has a substantially square opening slightly larger than the weight portion 11 and the attached weight portion 21 at the center portion. One side of the fixing portion 13 is set to, for example, 0.8 mm to 3.0 mm, and the width of the arm constituting the fixing portion 13 (the width in the direction orthogonal to the longitudinal direction of the arm; w in FIG. 5) is, for example, 0. It is set to 1 mm to 1.8 mm. Moreover, the thickness (t of FIG. 5) of the fixing | fixed part 13 is set to 0.2 mm-0.625 mm, for example. The sensor element 20 is fixed to the substrate 1 by bonding the lower surface of the fixing portion 13 to the main surface 1A of the substrate 1 with the adhesive 8 (FIG. 3B).

  FIG. 5 is a perspective view when the sensor element 20 is viewed from the lower surface side. A concave portion 11a is formed in the weight portion 11, and a weight member 22 is provided in the concave portion 11a (see also FIGS. 3A and 6D). The weight member 22 is made of a material having a specific gravity greater than that of the weight portion 11. For example, while the weight portion 11 is made of silicon, the weight member 22 is made of iridium, osmium, platinum, rhenium, gold, tungsten, uranium, tantalum, palladium, ruthenium, thallium, lead, silver, molybdenum, lutetium. , Formed by bismuth.

  The shape and size of the weight member 22 (recess 11a) may be set as appropriate. In FIG. 5, the weight member 22 formed in the same shape as the shape of the weight part 11, that is, a rectangular parallelepiped shape is illustrated. The thickness of the weight member 22 (depth of the recess 11a) is set to be equal to the thickness of the support layer 26 (FIG. 6D) of the SOI substrate 27, for example. Moreover, the inner peripheral surface of the recessed part 11a is a rough surface (FIG.7 (c)).

  Similarly, a concave portion 21 a is formed in the attached weight portion 21, and an attached weight member 23 made of a material having a specific gravity larger than that of the attached weight member 23 is provided in the recessed portion 21 a. The shape and size of the attached weight member 23 (recess 21a) may also be set as appropriate. In FIG. 5, the attached weight member 23 formed in the same shape as the attached weight portion 21, that is, a rectangular parallelepiped shape is illustrated. The attached weight member 23 may be formed integrally with the weight member 22 by connecting the recess 11a and the recess 21a.

  As shown in FIG. 5, the fixing portion 13 is provided with a hole portion 7 having an opening 7a on the lower surface thereof. Four holes 7 are provided at portions corresponding to the application position of the adhesive 8, for example, at the four corners of the fixing portion 13. The hole 7 is for accommodating extra adhesive 8 when the sensor element 20 is bonded to the substrate 1 with the adhesive 8. As a result, the adhesive 8 can be prevented from spreading along the lower surface of the fixing portion 13, and the adhesive area of the adhesive 8 does not vary greatly. As a result, it is possible to suppress the generation of non-uniform residual stress in the sensor element 20 and to provide an acceleration sensor device having excellent electrical characteristics. Further, since the sensor element 20 and the substrate 1 are joined in a state where a part of the adhesive 8 is embedded in the hole 7, when an impact is applied to the sensor element 20 from the lateral direction, Since the embedded adhesive 8 absorbs the impact, there is an advantage that the impact resistance in the lateral direction is improved. Furthermore, since the sensor element 20 is reduced in weight by providing the hole portion 7, the adhesive 8 and the sensor element 20 are difficult to peel off, which also improves the impact resistance.

  The hole portion 7 is preferably formed so as not to penetrate in the thickness direction of the fixed portion 13, in other words, the bottom surface of the hole portion 7 does not reach the upper surface of the fixed portion 13. By forming the hole portion 7 in this manner, the degree of freedom in routing the wiring formed on the upper surface side of the fixed portion 13 is not lowered. In addition, there is an advantage that pick-up by suction collet can be performed from the upper surface side of the sensor element 20 when the sensor element 20 is mounted on the substrate 1. On the other hand, when the hole portion 7 is formed so as not to penetrate in the thickness direction of the fixing portion 13 and the sensor element 20 is fixed to the substrate 1, the opening portion 7 a of the hole portion 7 is blocked, so that the inside of the hole portion 7 is formed. The gas tends to be sealed. When the gas is sealed inside the hole 7, the sealed gas expands or contracts due to a change in ambient temperature, thereby applying unnecessary pressure to the sensor element 20 and degrading the electrical characteristics of the acceleration sensor device. There is a fear. Therefore, it is preferable to provide the fixed portion 13 with a communicating portion 16 that communicates the inner wall surface of the hole 7 and the side surface of the fixed portion 13 so that the gas is not sealed. By providing the communication portion 16, even if the gas existing inside the hole portion 7 expands or contracts, the gas enters and exits through the communication portion 16, thereby preventing unnecessary pressure from being applied to the sensor element 20. It is possible to suppress the deterioration of the electrical characteristics of the acceleration sensor device. Moreover, it is preferable that the communication part 16 is connected to the inner peripheral surface 13 a side of the fixed part 13. By connecting the communication portion 16 to the inner peripheral surface 13a side of the fixed portion 13, when an external impact is applied to the outer peripheral surface of the fixed portion 13, for example, when the sensor element 20 is cut into individual pieces from the wafer. Further, it is possible to reduce the damage of the fixing portion 13.

  For example, the hole 7 is formed in a columnar shape, and the diameter φ and the depth d of the opening 7 a are set mainly in consideration of the relationship with the adhesive 8. Specifically, the area of the application surface (contact surface with the substrate 1) of the bonding member when the adhesive 8 is applied to the main surface 1A (FIG. 3) of the substrate 1 is measured in advance. The diameter φ of the opening 7a is set so as to be smaller. On the other hand, the depth d of the hole 7 is set so that the height of the adhesive 8 when applied to the main surface 1A of the substrate 1 is measured in advance and becomes larger than the height. When the spacer 8 is included in the adhesive 8 (FIG. 3B), the diameter φ of the opening 7 a is preferably larger than the diameter size of the spacer member 17 by 5 times or more. This makes it easy for excess adhesive 8 to enter the hole 7. Furthermore, considering the impact resistance when cutting the sensor element 20 from the wafer state into individual pieces, the distance from the flange of the opening 7a (the inner wall surface of the hole 7) to the outer peripheral surface of the fixed portion 13 should be 100 μm or more. Is preferred. When the sensor element 20 is manufactured using an SOI substrate, the difference value obtained by subtracting the depth d of the hole 7 from the thickness t of the fixed portion 13 is the same as the thickness of the semiconductor layer 25 (FIG. 6) of the SOI substrate 27. Or it is better to make it the same as the thickness of the semiconductor layer 25 and the insulating layer 24 (FIG. 6). As a result, the number of processes for making holes does not increase, and the fixing portion 13 is not easily broken.

  The shape of the hole 7 is not limited to a cylindrical shape, and may be any shape such as a quadrangular prism or a triangular prism.

  A beam portion 12 is provided between the fixed portion 13 and the weight portion 11 as shown in FIG. The beam portion 12 has one end connected to the center portion on the upper surface side of each side of the weight portion 11 and the other end connected to the center portion on the upper surface side of each side in the inner periphery of the fixed portion 13. In the sensor element 20, four beam portions 12 are provided.

  The beam portion 12 has flexibility. When acceleration is applied to the sensor element 20, the weight portion 11 moves, and the beam portion 12 bends as the weight portion 11 moves. For example, the beam portion 12 has a length in the longitudinal direction set to 0.1 mm to 0.8 mm, a width (a length in a direction perpendicular to the longitudinal direction) set to 0.01 mm to 0.2 mm, and a thickness of 5 μm. It is set to ˜20 μm. Thus, flexibility is expressed by forming the beam portion 12 to be elongated and thin.

  A plurality of resistance elements 15 are formed on the upper surface of the beam portion 12. More specifically, the resistance element 15 is a piezoresistance element formed by implanting boron into an n-type SOI substrate 27. In the present embodiment, these resistances are placed at predetermined positions on the beam portion 12 so that the acceleration in the three-axis directions (X-axis direction, Y-axis direction, and Z-axis direction in the three-dimensional orthogonal coordinate system shown in FIG. 4) can be detected. An element 15 is formed. For example, two resistance elements 15 for detecting acceleration in the X-axis direction are provided on the two beam parts 12 extending in the X-axis direction, and two resistance elements 15 are arranged on each beam part 12. . Among these four resistance elements 15, the resistance elements arranged on the fixed portion 13 side are connected in series, the resistance elements arranged on the weight portion 11 side are connected in series, and these are connected in parallel. This constitutes a bridge circuit. The two beam portions 12 extending in the Y-axis direction are provided with four resistance elements 15 for detecting acceleration in the Y-axis direction. These resistance elements 15 are used for detecting acceleration in the X-axis direction. The resistor circuit 15 is arranged in the same manner, and a bridge circuit is configured by connecting the resistor elements. Although not shown, the four resistance elements 15 for detecting acceleration in the Z-axis direction are provided with four beam elements 12 for detecting acceleration in the X-axis direction on the two beam portions 12 extending in the X-axis direction. It is formed so as to be aligned with each of the resistance elements 15. The resistance element 15 for acceleration detection in the Z-axis direction is different from the resistance element 15 for acceleration detection in the X-axis direction in the way of connecting the resistance elements, and in this embodiment, extends in the X-axis direction. A resistance element 15 on the fixed part 13 side provided in one of the two beam parts 12 and a resistance element 15 on the weight part 11 side provided in the other beam part 12 are connected in series. A bridge circuit is configured. When acceleration is applied to the sensor element 20 in which such a bridge circuit is assembled, the beam portion 12 is bent as described above, and the resistance element 15 is deformed in accordance with the bending, so that the output voltage detected by the bridge circuit changes. To do. The direction and magnitude of the applied acceleration can be detected by taking out the change in the output voltage based on the change in the resistance value as an electrical signal and processing it with an external IC. The resistance element 15 for detecting the acceleration in the Z-axis direction may be provided on the two beam portions 12 extending in the Y-axis direction in the same manner as that provided in the beam portion 12 extending in the X-axis direction.

  An element-side electrode pad 14 that is electrically connected to the resistance element 15 is provided on the upper surface of the fixed portion 13, and the resistance elements 15 are connected to each other and the electric power from the resistance element 15 is connected via the element-side electrode pad 14. The signal is taken out.

  The sensor element 20 is mounted on the substrate 1 as shown in FIG. The substrate 1 has a function of protecting the sensor element 20, and a cavity 5 that houses the sensor element 20 is provided inside. The substrate 1 is formed by laminating a plurality of insulating layers made of a ceramic material or the like, and is configured by three insulating layers 1a to 1c in the present embodiment. The insulating layer 1a is made of a flat member, and the sensor element 20 is placed on the main surface 1A. The insulating layer 1b is a frame-like member having an opening that is slightly larger than the sensor element 20, and is joined to the insulating layer 1a. The insulating layer 1c is a frame-like member having an opening wider than the opening of the insulating layer 1b, and is joined to the insulating layer 1b so that a part of the main surface of the insulating layer 1b is exposed. A plurality of substrate-side electrode pads 4 are formed on the main surface of the insulating layer 1b exposed from the opening of the insulating layer 1c. The substrate-side electrode pad 4 is electrically connected to the element-side electrode pad 14 provided on the upper surface of the fixed portion of the sensor element 20 by the fine metal wire 6. A plurality of external terminals 2 are provided on the lower surface of the substrate 1, and the external terminals 2 are connected to the substrate-side electrode pads 4 via via-hole conductors 3 provided inside the substrate 1. That is, the electrical signal of the sensor element 20 is extracted to the outside through the element side electrode pad 14, the fine metal wire 6, the substrate side electrode pad 4, the via hole conductor 3, the external terminal 2, and the like.

  The sensor element 20 placed on the main surface 1 </ b> A of the substrate 1 is bonded to the substrate 1 with an adhesive 8. As described above, the hole 7 is provided in the fixing portion 13 of the sensor element 20 at a position corresponding to the application position of the adhesive 8, so that a part of the adhesive 8 enters the hole 7 and remains. The adhesive 8 is interposed between the periphery of the opening 7 a of the hole 7 and the main surface 1 A of the substrate 1. Therefore, the sensor element 20 and the substrate 1 are joined by the adhesive 8 interposed between the periphery of the opening 7 a of the hole 7 and the main surface of the substrate 1. As the adhesive 8, for example, a silicone resin or an epoxy resin can be used. In particular, it is preferable to use a silicone resin from the viewpoint of relaxing the residual stress during bonding.

  The adhesive 8 is mixed with a spherical spacer member 17 having a predetermined diameter so that a gap of a predetermined size is formed between the lower surface of the weight portion 11 and the main surface 1A of the substrate 1. . That is, the size of the gap between the lower surface of the weight portion 11 and the main surface 1 </ b> A of the substrate 1 can be controlled by the spacer member 17. The spacer member 17 is a spherical member having a predetermined hardness such as silica, silicon, divinylbenzene, and the diameter thereof is, for example, 2 to 20 μm. In the conventional acceleration sensor device, when a spacer member is mixed with the adhesive 8, it is necessary to make the inner diameter of the nozzle relatively large so that the nozzle for applying the adhesive is not clogged by the spacer member. It was difficult to control the amount small, and an excessive amount of adhesive was often applied. In this case, the adhesive protrudes from the fixed portion to the outside, and the protruding adhesive causes the deterioration of the electrical characteristics of the acceleration sensor device by narrowing the movable range of the weight portion. In particular, as the acceleration sensor device is reduced in size and height, the sensor element 20 is inevitably reduced in height and size, so that it is more difficult to control the amount of adhesive applied, which is excessive. The above problem due to the amount of adhesive tends to become significant. On the other hand, according to the acceleration sensor device of this embodiment, even if the application amount of the adhesive 8 increases, most of the excess adhesive 8 is accommodated in the hole 7, so that the adhesive 8 is fixed to the fixing portion 13. It is less likely to protrude outside. Therefore, it is possible to prevent the electrical characteristics of the acceleration sensor device from being deteriorated due to the excessively applied adhesive 8, and it is possible to cope with a reduction in the size of the acceleration sensor device.

  When the beam portion 12 is connected to the center of the four upper sides of the weight portion 11 as in the present embodiment, the sensor element 20 and the substrate 1 are preferably joined at the four corners of the fixing portion 13. As a result, the distance between the joint portion of the sensor element 20 to the substrate 1 and the beam portion 12 is increased, so that the influence exerted on the beam portion 12 by the residual stress that may be generated due to the bonding by the adhesive 8 is reduced. It is possible to suppress deterioration of the electrical characteristics of the acceleration sensor device.

  Thus, the lid 10 is fixed to the upper surface of the substrate 1 so as to close the opening of the cavity of the substrate 1 to which the sensor element 20 is bonded, and the sensor element 20 is hermetically sealed in the cavity 5. . The lid 10 is made of, for example, a metal plate such as 42 alloy or stainless steel, and is bonded to the substrate 1 by a thermosetting resin 9 such as an epoxy resin.

<Method for manufacturing sensor element>
FIG. 6 is a cross-sectional view illustrating a method for manufacturing the sensor element 20.

(Process A; formation of resistance element 15)
As shown in FIG. 6A, surface processing is performed on the SOI substrate 27. The SOI substrate 27 includes an insulating layer 24, a semiconductor layer 25 stacked on one side of the insulating layer 24, and a support layer 26 stacked on the other side of the insulating layer 24. Insulating layer 24 is formed, for example by SiO _2. The semiconductor layer 25 is made of, for example, silicon. The support layer 26 is made of, for example, a semiconductor such as silicon. The surface processing is processing on the semiconductor layer 25.

  Specifically, the resistance element 15 made of piezoresistance is formed by implanting impurities into the semiconductor layer 25 by ion implantation. Examples of the impurities include B (boron) when an n-type SOI substrate is used, and P (phosphorus) and As (arsenic) when a p-type SOI substrate is used. After the resistor element 15 is formed, a wiring connected to the piezoresistive element is formed. The wiring is formed by forming a metal material such as aluminum by metal sputtering, CVD, vapor deposition or the like and then patterning the formed metal material by dry etching, wet etching, or the like.

(Process B; formation of weight part 11, beam part 12, and fixing part 13)
Next, as shown in FIG. 6B, an SOI substrate is formed by a well-known semiconductor microfabrication technique such as photolithography or inductively coupled plasma reactive ion etching (ICP-RIE). 27, the weight part 11, the beam part 12, and the fixing part 13 are formed by processing from the semiconductor layer 25 side and the support layer 26 side.

  Specifically, first, the semiconductor layer 25 is removed in a region corresponding to a groove portion that separates the weight portion 11 and the fixing portion 13. Next, the support layer 26 is removed in a region corresponding to the groove and the recess 11a. Further, the insulating layer 24 is removed in a region corresponding to the groove. As described above, a groove portion penetrating the semiconductor layer 25, the insulating layer 24, and the support layer 26 is formed, and the SOI substrate 27 is divided into an inner peripheral side and an outer peripheral side by the groove portion, and the weight portion 11 and the fixing portion 13 are separated. And are formed. Further, the beam portion 12 is formed by the semiconductor layer 25 in the intermittent portion of the groove portion (the portion where the groove portion is interrupted). Furthermore, a recess 11 a is formed in which the bottom surface is constituted by the insulating layer 24 and the inner peripheral surface is constituted by the support layer 26.

(Process C; filling of weight member 22)
Next, as shown in FIG. 6C, the weight member 22 is formed by filling the concave portion 11 a with the material 22 ′ to be the weight member 22. The material 22 ′ is obtained by adding a solvent to a material such as a metal that becomes the weight member 22 to form a slurry. Filling the recess 11a with the material 22 'is performed by printing. Specifically, the screen 501 is disposed opposite to the support layer 26 side of the SOI substrate 27, and the material 22 ′ is poured into the recess 11a from the opening 501a of the screen 501. The opening 501a has the same shape and size as the opening shape on the surface of the support layer 26 of the recess 11a. However, the opening 501a may be different from the opening shape of the recess 11a or smaller than the opening shape of the recess 11a.

(Process D: Baking of SOI substrate 27)
Next, as shown in FIG. 6D, the SOI substrate 27 is fired to solidify the material to be the weight member 22, and the SOI substrate 27 and the weight member 22 are sintered. As described above, the sensor element 20 is formed by the processes A to D.

  In addition, when the material used as the weight member 22 is baked, the solvent evaporates, so that the material used as the weight member 22 contracts more than when it is filled. As a result, the surface of the weight member 22 has a concave shape and is positioned lower than the opening of the concave portion 11a. Therefore, the filling of the material to be the weight member 22 into the concave portion 11a and the firing may be repeated a plurality of times so that the surface of the weight member 22 and the opening surface of the weight portion 11 are accurately matched.

  The SOI substrate 27 has a larger area than the plurality of sensor elements 20, and the plurality of sensor elements 20 are formed from one SOI substrate 27 in steps A to D. Steps A to D are basically performed in parallel on a plurality of sensor elements 20 on one SOI substrate 27. For example, the screen 501 has a size extending over a plurality of sensor elements 20, and the plurality of sensor elements 20 are simultaneously printed. Then, after the process D, the SOI substrate 27 is divided into a plurality of sensor elements 20.

  FIG. 7 is a cross-sectional view illustrating the formation of the recess 11a in the process B. The recess 11a is formed by, for example, ICP-RIE. More specifically, it is formed by a Bosch process.

  In the Bosch process, as shown in FIG. 7A, first, a first recess 28A shallower than the depth of the recess 11a is formed by etching. The shape of the first recess 28A is a trapezoid with a large area on the opening side due to an etching accuracy error. Next, a protective film for protecting the side surface of the first recess 28A is formed.

  Next, as shown in FIG. 7B, a second recess 28B having the same diameter and depth as the first recess 28A is formed on the bottom surface of the first recess 28A. Similarly to the first concave portion 28A, the second concave portion 28B has a trapezoidal shape with a large area on the opening side due to an error in etching accuracy. And the protective film which protects the side surface of the 2nd recessed part 28B is formed.

  Here, since the side surface of the first recess 28A is protected by the protective film, the area of the bottom surface side of the first recess 28A is not increased by etching the second recess 28B, and the first recess 28A and the second recess 28A are not enlarged. There is a step at the boundary of 28B.

  Thereafter, similarly to the formation of the first recess 28A and the second recess 28B, the etching and the formation of the protective film are repeated to form the recess 11a. The insulating layer 24 functions as an etching stopper. The inner peripheral surface of the recess 11a becomes a rough surface due to a step generated at the boundary of each etching.

  In addition, the magnitude | size of the level | step difference formed by a Bosch process is about 0.01 micrometer-10 micrometers. Moreover, in this application, a rough surface means the surface where the unevenness | corrugation is larger than the side surface of the hole part at the time of performing only an etching, without forming a protective film. Therefore, when the Bosch process is performed, the side surface of the hole is rough. Moreover, even if the formation method of a hole part is not specified, if there is a level difference of 0.01 μm or more, it can be said that the surface is rough.

<Method for manufacturing acceleration sensor device>
While preparing the sensor element 20 as mentioned above, the board | substrate 1 which has 1 A of main surfaces in which the sensor element 20 is mounted is prepared.

  The substrate 1 is formed by laminating a plurality of insulating layers made of a ceramic material such as alumina. Specifically, the substrate 1 having the cavity 5 by sequentially laminating a flat insulating layer 1a, an insulating layer 1b having a rectangular opening, and an insulating layer 1c having an opening larger than the opening of the insulating layer 1b. Is produced.

  Next, the adhesive 8 is applied to a position corresponding to the opening 7 a when the sensor element 20 is placed on the main surface 1 </ b> A of the substrate 1. Next, the sensor element 20 is placed on the main surface 1 </ b> A of the substrate 1, and the adhesive 8 is cured to bond the sensor element 20 and the substrate 1.

  After the sensor element 20 is bonded to the substrate 1, the element-side electrode pad 14 provided on the sensor element 20 and the substrate-side electrode pad 4 provided on the substrate 1 are connected by a thin metal wire 6 made of gold, copper, aluminum or the like. Finally, a metal lid 10 made of 42 alloy or the like is joined to the upper surface of the substrate 1 (the upper surface of the insulating layer 1d) by a thermosetting resin 9 such as an epoxy resin, thereby completing an acceleration sensor device as a product.

  According to the above embodiment, since the sensor element 20 includes the weight member 22 made of a material having a specific gravity larger than that of the weight portion 11 and embedded in the concave portion 11a of the weight portion 11, the weight member 22 and The density of the weight part as the whole weight part 11 can be made high. As a result, it is possible to reduce the size of the sensor element 20 while maintaining sensitivity. Further, since the weight member 22 is fixed to the weight portion 11 by embedding the weight member 22 in the concave portion 11a, the accuracy is higher than the case where the weight member is fixed to the tip of the weight portion 11. The weight member 22 can be positioned and fixed to the weight portion 11 well. For example, when the recess 11a is formed by photolithography, the weight member 22 can be positioned with an accuracy equivalent to the accuracy of photolithography.

  Furthermore, since the concave portion 11a is formed by removing the support layer 26 in the step of forming the weight portion 11, the beam portion 12, and the fixing portion 13, the number of steps due to the formation of the concave portion 11a does not occur. .

  Further, since the weight member 22 is filled in the concave portion 11a by printing, the weight member 22 can be filled simultaneously with respect to a plurality of sensor elements 20 formed on one wafer, and productivity is improved.

  Since the inner peripheral surface of the recess 11a is a rough surface, the weight member 22 is suppressed from falling out of the recess 11a. Further, the process of partially removing the SOI substrate 27 to form the recess 11a is performed in a plurality of times in the depth direction of the recess 11a, and the inside of the recess 11a is caused by the step generated at the boundary of the plurality of removal processes. Since the peripheral surface is a rough surface, the rough surface can be formed while realizing a high-precision deep pit.

  Since the recess 11 a is provided in the support layer 26, the weight member 22 hardly affects the semiconductor layer 25 even when a conductive material is used as the weight member 22. Therefore, the range of selection of the material of the weight member 22 can be expanded. Further, unlike the case where the recess is formed in the semiconductor layer 25, the wiring design of the semiconductor layer 25 is not forced to change.

(Modification 1)
FIG. 8 is a cross-sectional view showing a modification of the acceleration sensor device according to the above-described embodiment. The cross-sectional view of FIG. 8 corresponds to the cross section taken along the line AA ′ in FIG. The acceleration sensor device according to this modification further includes an IC chip 30 that performs arithmetic processing on the output signal of the sensor element 20. In the acceleration sensor device shown in FIG. 8, an IC chip 30 is accommodated in a cavity provided on the lower surface side of the substrate 1, and the sensor element 20 and the external terminal 2 are connected via the via-hole conductor 3 and the wiring conductor provided on the substrate 1. And are electrically connected. The IC chip 30 is, for example, an integrated circuit including an amplifier circuit that amplifies the output signal of the sensor element 20, a temperature compensation circuit that corrects temperature characteristics of the sensor element 20, and a noise removal circuit that removes noise. By providing such an IC chip 30, acceleration can be detected with high accuracy.

(Modification 2)
Fig.9 (a) is sectional drawing which shows the modification of an acceleration sensor element. The cross-sectional shape of the concave portion 111a of the weight portion 111 (the cross-sectional shape of the weight member 122) is such that the opening side of the concave portion 111a is wider than the bottom surface side of the concave portion 111a. In this case, the weight member 122 is easily filled in the recess 111a. Moreover, since the opening side may be widened due to an error in etching accuracy, it is not necessary to use an etching technique capable of forming a vertical wall. 9A illustrates the case where the recess 111a has a trapezoidal cross section, the recess 111a may have a triangular diameter, or the bottom surface of the recess 111a may be arcuate. Good.

(Modification 3)
FIG. 9B is a cross-sectional view showing a modified example of the sensor element. The cross-sectional shape of the concave portion 211a of the weight portion 211 (the cross-sectional shape of the weight member 222) is such that the bottom surface side of the concave portion 211a is wider than the opening side of the concave portion 211a. In this case, the weight member 222 is difficult to come off from the recess 211a. Therefore, the durability of the sensor element is increased. 9B illustrates the case where the recess 211a has a trapezoidal cross section, the recess 211a may have a triangular diameter, or the bottom surface of the recess 211a may be arcuate. Good.

(Modification 4)
FIG. 9C is a cross-sectional view showing a modification of the sensor element. The weight member 322 includes a first weight member 322a on the bottom surface side of the recess 11a and a second weight member 322b on the opening side of the recess 11a. The first weight member 322a and the second weight member 322b are made of different materials. For example, the first weight member 322a is made of a material having a specific gravity larger than that of the weight portion 11, and the second weight member 322b is smaller in specific gravity than the first weight member 322a, but the weight portion 11 is more than the first weight member 322a. And made of a material that is easy to sinter. Accordingly, it is possible to prevent the weight member 322 from coming off while increasing the density of the weight portion. The second weight member 322b may be larger or smaller in specific gravity than the weight portion 11, but the weight member 322 as a whole needs to have a larger specific gravity than the weight portion 11.

(Modification 5)
FIG. 9D is a cross-sectional view showing a modified example of the sensor element. The thickness of the weight member 422 is smaller than the depth of the concave portion 11 a of the weight portion 11. That is, the weight member 422 is filled in part of the bottom surface side of the recess 11a. As the amount of the weight member 422 filled in the recess 11a increases, the sensitivity increases while the material cost of the weight member 422 increases. Therefore, the amount of the weight member 422 filled in the recess 11a may be adjusted according to the required sensitivity. FIG. 9D shows a case where the weight member 422 is not filled up to the opening of the recess 11a as a result of such adjustment.

  The present invention is not limited to the above-described embodiments and modifications, and may be implemented in various aspects.

  The acceleration sensor element is not limited to the one that measures the acceleration in the triaxial direction. For example, the acceleration sensor element may measure acceleration in one axis direction. The weight part may not have an attached weight part.

  In the above-described embodiment, the acceleration sensor element in which the hole 7 is provided in the fixed portion 13 has been described. However, the hole 7 may not be provided and the lower surface of the fixed portion 13 may be flat throughout.

  The weight member is not limited to a member formed by solidifying a liquid material filled in the recess. For example, a solid weight member may be fitted into the concave portion and fixed to the weight portion with an adhesive. Further, for example, the weight member may be formed by vapor-depositing a metal inside the recess. A weight part formed with a plurality of recesses or a weight part formed of a porous body may be immersed in a slurry-like material, and the weight member may be embedded in the recesses. When the weight member is formed by filling the liquid material into the recess, the filling method is not limited to printing. For example, the recess may be filled with a liquid material by a dispenser.

1 is a perspective view of an acceleration sensor device according to an embodiment of the present invention. The top view of the state which removed the cover of the acceleration sensor apparatus shown in FIG. Sectional drawing of the acceleration sensor apparatus shown in FIG. The perspective view of the sensor element mounted in the acceleration sensor apparatus shown in FIG. It is a perspective view when the sensor element shown in FIG. 4 is seen from the lower surface side. Sectional drawing explaining the manufacturing method of the sensor element shown in FIG. Sectional drawing explaining the formation method of the recessed part of the weight part in the manufacturing method of FIG. It is sectional drawing which shows the modification of the acceleration sensor apparatus which concerns on embodiment of this invention. It is sectional drawing which shows the modification of the sensor element which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Board | substrate 2 ... External terminal 3 ... Via-hole conductor 4 ... Board | substrate side electrode pad 5 ... Cavity 6 ... Metal fine wire 7 ... Hole part 8 ... Adhesive 11. .... Weight part 11a ... Concave part 12 ... Beam part 13 ... Fixed part 14 ... Element side electrode pad 15 ... Resistance element 20 ... Sensor element 22 ... Weight member

Claims (9)

A weight portion having a recess;
A frame-shaped fixing portion surrounding the weight portion;
A beam portion having one end connected to the fixed portion and the other end connected to the weight portion;
A resistance element provided in the beam portion, the resistance value of which changes with bending of the beam portion;
A weight member made of a material having a specific gravity greater than that of the weight portion and embedded in the recess;
An acceleration sensor element. The acceleration sensor element according to claim 1, wherein a cross-sectional shape of the concave portion is such that an opening side of the concave portion is wider than a bottom surface side of the concave portion. The acceleration sensor element according to claim 1, wherein an inner peripheral surface of the recess is a rough surface. A substrate having an insulating layer, a support layer stacked on one side of the insulating layer, and a semiconductor layer stacked on the other side of the insulating layer;
The weight portion and the fixing portion are formed by dividing the substrate into the weight portion and the fixing portion by a groove penetrating the insulating layer, the support layer, and the semiconductor layer,
The beam portion is formed by the semiconductor layer of the intermittent portion of the groove,
The recess is provided in the support layer;
The acceleration sensor element according to any one of claims 1 to 3, wherein the weight member is formed of a conductive member. The acceleration sensor element according to any one of claims 1 to 4,
An acceleration sensor device comprising: an IC chip that processes an output signal of the acceleration sensor element. Forming a resistance element on one principal surface of the substrate; and
By processing the substrate, a beam portion in which the resistance element is arranged, a weight portion having one end of the beam portion connected and having a recess opened on one main surface side, and the other end of the beam portion are connected. And a step B of forming a fixing portion surrounding the weight portion;
Filling the concave portion with a weight member made of a material having a specific gravity greater than that of the substrate; and
A method for manufacturing an acceleration sensor element including: The acceleration sensor element manufacturing method according to claim 6, wherein the weight member is filled by printing. The method of manufacturing an acceleration sensor element according to claim 6, wherein a cross-sectional shape of the concave portion is a shape in which an opening side of the concave portion is wider than a bottom surface side of the concave portion. In the step B, the process of partially removing the substrate to form the recesses is performed in a plurality of times in the depth direction of the recesses, and the recesses are formed by steps generated at the boundaries of the multiple removal processes. The manufacturing method of the acceleration sensor element of any one of Claims 6 thru | or 8.

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