JP2006302943A - Microstructure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microstructure capable of reducing the influence of stress from the outside. <P>SOLUTION: A weight 14 is supported on a semiconductor layer 11 via a plurality of beams 111-114 to form a sensor package 1. The sensor package 1 is arranged on the bottom surface 22 of a frame member 2. The bottom surface of a supporting substrate layer 13 facing the bottom surface 22 is divided into four regions around a centroid source position of the bottom surface shape. In only one of the divided regions, the bottom surface of the substrate layer 13 is joined to the bottom surface 22 of the frame member 2 by a die bonding paste 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a microstructure, and more particularly to a support structure for a microstructure comprising an SOI substrate.

  An example of a semiconductor acceleration sensor using a semiconductor sensor chip is described in Japanese Patent Laid-Open No. 10-123166 (Patent Document 1). The semiconductor sensor chip supports a weight portion through a beam portion in the frame body, and detects acceleration by using a piezo effect of a resistance element formed on the beam portion.

  FIG. 8 shows an example of a microstructure of a conventional semiconductor acceleration sensor. In particular, FIG. 8A is a sectional view of the microstructure, and FIG. 8B is a diagram showing the back surface of the sensor package.

  As shown in FIG. 8A, the microstructure 10 includes a sensor package 1, and a frame member 2 and a lid member 3 that are storage bodies for the sensor package 1. The sensor package 1 is composed of an SOI (Silicon On Insulator) substrate, and includes a semiconductor layer (Si; SOI) 11, a buried insulating layer (SiO2) 12, a support substrate layer (Si) 13, and a weight body 14. (Si).

  The support substrate layer 13 is formed in a frame shape having a rectangle and a space in the center by etching, and a weight body 14 is provided in the center space. The weight body 14 is connected to the central portion of each side on the frame of the support substrate layer 13 through beams 111, 112, 113, and 114 that constitute a part of the semiconductor layer 11. A buried insulating layer 12 is formed between the semiconductor layer 11 and the support substrate layer 13 and the weight body 14. Although not shown, piezoresistive elements R1 to R4 are arranged in the beams 111 to 114.

  The sensor package 1 is accommodated in a recess 21 formed in a frame member 2 having an upper opening. The die bonding paste 4 is applied to the four corners of the bottom surface of the support substrate layer 13 as shown in FIG. 8B and die-bonded on the bottom surface 22 of the recess 21. A step portion 23 is formed in the frame member 2, and a metal pad 5 is disposed on the step portion 23, and the metal layer 6 is wired between the semiconductor layer 11 and the metal pad 5. The opening of the frame member 2 is covered with the lid member 3.

  FIG. 9 shows an example in which the sensor package 1 shown in FIG. 8 is mounted on a frame member via a buffer layer. In particular, FIG. 9A is a cross-sectional view of a micro structure, and FIG. FIG. In FIG. 9A, a buffer layer 8 made of silicon, glass or the like is disposed on the bottom surface 22 of the recess 21 of the frame member 2 included in the microstructure 10a with the insulating layer 7 interposed therebetween. The buffer layer 8 is disposed to absorb the stress from around the sensor package 1 described with reference to FIG. 8 and prevent the stress from affecting the sensor element 1, and as shown in FIG. 9B. The die bonding paste 4 is applied to the entire lower surface of the support substrate layer 13, and the sensor package 1 is die-bonded on the buffer layer 8.

  FIG. 10 is a circuit diagram showing a bridge circuit formed by piezoresistive elements in the acceleration sensor.

  The piezoresistive elements R1 to R4 arranged in the beams 111 to 114 of the microstructure 10 shown in FIGS. 8 and 9 are bridge-connected as shown in FIG. 10 to form a bridge circuit. A voltage + V is applied to the connection point between the piezoresistive elements R1 and R2, the connection point between the piezoresistive elements R3 and R4 is grounded, and the connection point between the piezoresistive elements R2 and R3 and the connection point between the R1 and R4 are determined according to acceleration. Signal is output.

That is, when no acceleration is applied, the resistance values of the piezoresistive elements R1 to R4 are equal, and the bridge circuit is balanced. When acceleration is applied to the sensor package 1, an external force acts on the weight body 14 due to the acceleration, the weight body 14 is displaced from a fixed position, and mechanical distortion caused by this displacement is caused by the machine of the beams 111 to 114. Absorbed by mechanical deformation. Due to the mechanical displacement of the beams 111 to 114, the resistance value of the piezoresistive element changes, and the bridge circuit is unbalanced and a signal corresponding to the acceleration is output.
JP-A-10-123166

  In the semiconductor acceleration sensor shown in FIG. 8, there is a problem in that the beams 111 to 114 are affected by stress from the surroundings. That is, since the die bonding paste 4 is applied to the four corners of the bottom surface of the support substrate layer 13 of the sensor package 1 and mounted on the bottom surface 22 of the frame member 2, the stress affects the beams 111 to 114. . This is because the support substrate layer 13 of the sensor package 1 is made of, for example, silicon, whereas the frame member 2 is made of metal, so that residual stress is generated due to the difference in linear expansion coefficient between the two. Because.

  In the semiconductor acceleration sensor shown in FIG. 9, the buffer layer 8 is provided between the sensor package 1 and the frame member 2 to prevent the influence of stress from the surroundings. However, there is no effect on the residual stress received from the circuit board on which the semiconductor acceleration sensor is mounted. Such residual stress causes manufacturing variations in the offset and sensitivity of the acceleration sensor, and further, the residual stress state changes depending on the temperature. Further, since the buffer layer 8 is provided, there arises a problem that the height of the package after assembly is increased. This problem occurs not only in the semiconductor acceleration sensor but also in the semiconductor pressure sensor.

  Therefore, the present invention is to provide a microstructure that can reduce the influence of external stress.

  The present invention provides a microstructure having a support part, a sensor element having a movable part supported by the support part, and a pedestal for mounting the sensor element, wherein the bottom surface of the support part facing the pedestal is provided. In addition, it is divided into four regions with the center of gravity of the bottom shape as the center, and only one of the regions is provided with a joint for joining the bottom of the support and the pedestal.

  By joining the bottom surface of the support portion and the pedestal only in one region, the influence of external stress received from the pedestal can be reduced.

  Preferably, the joining portion includes an adhesive that joins between one region between the bottom surface of the support portion and the pedestal. By bonding one region between the bottom surface of the support portion and the pedestal with an adhesive, the support portion can be stably supported on the pedestal.

  Preferably, the other areas except for one area are in contact with each other among the surfaces of the support section where the bottom surface and the pedestal face each other. Accordingly, the four corners of the support portion can be brought into contact with the pedestal, so that the sensor element can be supported horizontally. For example, wire bonding can be performed when metal wiring is provided on the sensor element.

  In one embodiment, the joining portion includes a recess formed in one of the bottom surface of the support portion and the pedestal corresponding to one region, and the adhesive is formed on the surface where the bottom surface of the support portion and the pedestal are in contact with each other. The concave part formed in one of them and the other of the surfaces where the bottom surface of the support part and the pedestal are in contact are joined. By applying and bonding an adhesive to the recess corresponding to one region, the support portion and the pedestal are in contact with each other in the other three regions, so that the sensor element can be supported horizontally.

  Preferably, the pedestal includes a base, and a buffer member provided on the base, on which the support portion is placed and absorbs stress applied from the periphery, and the joint portion is a bottom surface of the support portion. The surface where the shock-absorbing member contacts is divided into four regions, and one of the regions is joined. By supporting the support member on the pedestal via the buffer member, it is possible to prevent the influence of stress from around the sensor element.

  In another embodiment, the joint portion includes a recess formed in one of the bottom surface of the support portion and the buffer member corresponding to one region, and the adhesive is either of the bottom surface of the support portion or the buffer member. The recessed part formed in one side and the other side of the bottom face of a support part, and a buffer member are joined. By applying an adhesive to the recess and bonding the support member to the buffer member, it is possible to prevent the influence of stress from around the sensor element in a state where the sensor element is horizontally supported.

  Preferably, the joining portion joins the bottom surface of the support portion and the buffer layer or the pedestal at one or more locations in the four divided regions. The support of the sensor element is further stabilized by joining at one or more places.

  Preferably, the support part includes a frame member having a space in the center and supporting the movable part via the beam member. Acceleration and pressure can be detected by detecting the displacement of the movable part.

  In one embodiment, a plurality of beam parts which support a movable part with a support part are included, and in another embodiment, a movable part is constituted by a vibration part.

  As a specific embodiment, the sensor element is any one of an acceleration sensor, an angular velocity sensor, a pressure sensor, and a microphone.

  According to the present invention, the bottom surface of the support portion facing the pedestal is divided into four regions centered on the center-of-gravity position of the bottom surface shape, and the bottom surface of the support portion and the pedestal are joined to only one of the regions. By providing the joining portion, the influence of external stress can be reduced, so that variations in offset and sensitivity can be suppressed, and temperature characteristics can be improved.

  FIG. 1 is a view showing a microstructure in one embodiment of the present invention, in particular, (A) is a cross-sectional view of the microstructure, and (B) is a view of a semiconductor layer as viewed from above. (C) is a figure which shows the back surface of a sensor package.

  1A, a microstructure 10b includes a sensor package 1, a frame member 2, and a lid member 3 in the same manner as the conventional example shown in FIG. 8, and the sensor package 1 includes a semiconductor layer 11, A buried insulating layer 12 and a supporting substrate layer 13 as a supporting portion are included. The support substrate layer 13 has an opening at the center, and a weight body 14 as a movable part is disposed in the opening.

  A semiconductor layer 11 shown in FIG. 1B includes a region 115 corresponding to the upper surface of the support substrate layer 13, a region 116 corresponding to the upper surface of the weight body 14, and a beam portion connecting the regions 115 and 116. And the beams 111-114. The beams 111 to 114 are provided to support the weight body 14 with the support substrate layer 13. Although not shown, the piezoresistive elements R1 to R4 shown in FIG. 10 are arranged in the beams 111 to 114.

  The frame member 2 includes a bottom surface 22 serving as a base of the concave portion 21 and a step portion 23 for arranging the metal pad 5. Although the sensor package 1 is disposed on the bottom surface 22, in the conventional example shown in FIG. 8, the die bonding paste 4 is applied to the four corners of the bottom surface of the support substrate layer 13 of the sensor package 1 and die-bonded on the bottom surface 22. .

  On the other hand, in this embodiment, a region where the bottom surface of the support substrate layer 13 faces the bottom surface 22 of the frame member 2 is a region indicated by a dotted line in FIG. The die bonding paste 4 is applied as an adhesive material to only one of the regions, and the support substrate layer 13 and the bottom surface 22 are die-bonded. Thus, by joining the bottom surface of the support substrate layer 13 and the bottom surface 22 of the frame member 2 only in one of the four regions, the influence of external stress received from the circuit board or the like can be reduced. The reason will be described with reference to FIG.

  FIG. 2 is a view for explaining the principle for reducing the influence of external stress on the microstructure according to one embodiment of the present invention, and FIG. 2 (A) faces the frame member of the support substrate layer. The example which has joined in four places in the whole region is shown, (B) and (C) in the field which divided the field which meets the frame member of a support substrate layer into four centering on the gravity center position of the bottom face shape An example of joining at four locations within one region is shown.

  As shown in FIG. 2A, if the frame member 2 and the support substrate layer 13 having different thermal expansion coefficients are joined at four locations indicated by circles by the die bonding paste 4, the X direction is It is constrained by the length L1, the Y direction is constrained by the length L2, and the oblique direction is constrained by the length L3. Residual stress resulting from the difference in thermal expansion coefficient according to each length Has occurred.

  On the other hand, as shown in FIG. 2 (B), the region facing the frame member 2 of the support substrate layer 13 is centered at the center of gravity of the facing shape in the X direction and the Y direction. Assuming that the middle points are divided into four parts and joined at four points indicated by circles in one of the four divided parts, the length of the restraint portion in the X direction, the Y direction, Since the direction length is L1 / 2, L2 / 2, and L3 / 2 as compared with the example of FIG. 2A, the influence caused by the difference in the thermal expansion coefficient as a whole can be reduced to about half. it can.

  As shown in FIG. 2C, with the center of gravity of the facing shape as the center o, the area is divided into four lines connecting the corners of the area, and the four areas indicated by circles in one divided area are shown. When bonded, the length in the X direction is L1 / 2 and the length in the Y direction is L2 / 2 and L2 / 2. Therefore, the effect of the residual stress is smaller than that in the example shown in FIG. Can be halved.

  Therefore, by joining the region of the bottom surface of the frame member 2 with respect to the support substrate layer 13 only in one region of the region divided into four with the center of gravity of the bottom surface shape as the center, the residual stress received from the outside such as the circuit board The impact can be reduced.

  Therefore, in this embodiment, since the influence of the residual stress from the outside can be reduced, variations in offset and sensitivity can be suppressed, and temperature characteristics can be improved. Further, by directly bonding the support substrate layer 13 to the bottom surface 22 of the frame member 2, the height of the microstructure 10b can be reduced.

  FIG. 3 is a view showing a microstructure in another embodiment of the present invention. In particular, FIG. 3A is a sectional view of the microstructure, and FIG. 3B is a view showing the back surface of the sensor package.

  In the microstructure 10c of this embodiment, the buffer layer 8 is disposed on the bottom surface 22 of the frame member 2 shown in FIG. 3A via the insulating layer 7, and the sensor package 1 is disposed on the buffer layer 8. Is. And in this embodiment, the area | region which faces the buffer layer 8 of the bottom face of the support substrate layer 13 of the sensor package 1 is divided into four by the line which connects each corner of the area | region shown by the dotted line of FIG. Only in one region, the bottom surface of the supporting substrate layer 13 is die-bonded on the buffer layer 8 with the die-bonding paste 4. The other three regions of the four divided regions on the bottom surface of the support substrate layer 13 have a predetermined gap with respect to the buffer layer 8 and are not in contact with each other.

  Also in this embodiment, the region where the bottom surface of the support substrate layer 13 and the buffer layer 8 face each other is divided into four, and the bottom surface of the support substrate layer 1 and the buffer layer 8 are joined only in one of the regions. The influence of external stress received from a circuit board or the like can be reduced. Furthermore, since the sensor package 1 is disposed on the buffer layer 8, the height is slightly higher than that of the microstructure 10b shown in FIG. 1, but the influence of stress from around the sensor package 1 is prevented. can do.

  4A and 4B are diagrams showing a microstructure in another embodiment of the present invention. In particular, FIG. 4A is a cross-sectional view of the microstructure, and FIG. 4B is a diagram showing the back surface of the sensor package.

  The microstructure 10d of this embodiment has a corner portion including one of the four regions divided into the bottom surface of the support substrate layer 13 in the sensor package 1 shown in FIG. ), A recess 131 is formed with a depth of 10 to 30 μm, for example, and the die bonding paste 4 is applied with a thickness of 10 to 30 μm, for example, to the recess 131 and bonded to the bottom surface 22 of the frame member 2.

  Also in this embodiment, the region facing the buffer layer 8 of the support substrate layer 13 is divided into four parts, and the bottom surface of the support substrate layer 13 and the buffer layer 8 are joined only in one region of the circuit substrate. Can reduce the influence of external stress.

  Further, in this embodiment, the recess 131 is formed only in one of the four regions divided into the bottom surface of the support substrate layer 13 to form a joint, and the recess is formed in the other three regions. Since it does not exist, it contacts the bottom face 22 as a non-joining part. Accordingly, there is no gap between the other three regions on the bottom surface of the support substrate layer 13 and the bottom surface 22 of the frame member 2, so that the sensor package 1 can be disposed horizontally in the recess 21 of the frame member 2. It becomes possible. In addition, since all the four corners of the bottom surface of the support substrate layer 13 are in contact with the bottom surface 22, the support substrate layer 13 does not bend downward when the metal wire 6 is wire bonded to the surface of the semiconductor layer 11. The work will not be hindered.

  FIG. 5 is a view showing a microstructure in another embodiment of the present invention. In particular, FIG. 5A is a sectional view of the microstructure, and FIG. 5B is a view showing the back surface of the sensor package.

  The microstructure 10e of this embodiment is similar to the embodiment of FIG. 4 in that each corner portion of four regions among the four regions divided into the bottom surface of the support substrate layer 13 shown in FIG. 5B is formed, and only one of the recesses 131 is used as a bonding portion, and the bottom surface of the support substrate layer 13 is bonded onto the buffer layer 8 by the die bonding paste 4. Also in this embodiment, the side portions in the other three regions divided into the four bottom surfaces of the support substrate layer 13 are not bonded to the buffer layer 8 but are in contact with each other.

  Therefore, also in this embodiment, the influence of the external stress received from the circuit board or the like can be reduced, and the influence of the stress from around the sensor package 1 can be prevented by arranging the sensor package 1 on the buffer layer 8. it can. In addition, the sensor package 1 can be horizontally disposed in the recess 21 of the frame member 2 via the buffer layer 8. In addition, since all four sides of the bottom surface of the support substrate layer 13 are in contact with each other on the buffer layer 8, the metal wire 6 can be wire-bonded to the surface of the semiconductor layer 11.

  FIG. 6 is a view showing a microstructure in another embodiment of the present invention, in particular, (A) is a cross-sectional view of the microstructure, and (B) is a view showing the back surface of the sensor package. C) is a view of the frame member as viewed from above with the sensor package shown in FIG.

  In the embodiment shown in FIG. 4 described above, the recess 131 is formed on the bottom surface of the support substrate layer 13, whereas the microstructure 10f of this embodiment has the support substrate layer 13 shown in FIG. Corresponding to one region obtained by dividing the region facing the frame member 2 into four regions, a recess 24 is formed on the bottom surface 22 of the frame member 2 as shown in FIG. 6C. Is applied to the bottom surface 22 of the frame member 2, and the other three regions are not bonded.

  Also in this embodiment, the influence of external stress received from a circuit board or the like can be reduced. In addition, the sensor package 1 can be horizontally disposed in the concave portion 21 of the frame member 2, and in the region of the bottom surface of the support substrate layer 13, all the other three regions are in contact with the bottom surface 22 of the frame member 2. Therefore, the metal wire 6 can be wire bonded to the surface of the semiconductor layer 11.

  FIG. 7 is a view showing a microstructure in another embodiment of the present invention, in particular, (A) is a sectional view of the microstructure, (B) is a view showing the back surface of the sensor package, C) is a view of the buffer layer and the frame member as viewed from above with the sensor package removed from (A).

  In the embodiment shown in FIG. 5 described above, the concave portion 131 is formed on the bottom surface of the support substrate layer 13, whereas the microstructure 10 g of this embodiment is formed of the support substrate layer 13 shown in FIG. A recess 81 shown in FIG. 7C is formed on the buffer layer 8 corresponding to one region obtained by dividing the region facing the buffer layer 8 into four regions. Then, the die bonding paste 4 shown in FIG. 7B is applied to the recess 81 and the bottom surface of the support substrate layer 13 is die-bonded on the buffer layer 8 so that the other three regions are not bonded.

  Also in this embodiment, the influence of the external stress received from the circuit board or the like can be reduced, and the influence of the stress from around the sensor package 1 can be prevented by the buffer layer 8. Further, since the sensor package 1 is horizontally disposed in the concave portion 21 of the frame member 2 through the buffer layer 8 and all four corners of the bottom surface of the sensor package 1 are in contact with each other on the buffer layer 8, the metal wire 6 Can be wire-bonded to the surface of the semiconductor layer 11.

  In the above description, die bonding is performed on the bottom surface 22 of the frame member 2 or the buffer layer 8 in only one place in one divided region of the bottom surface of the support substrate layer 13. If it exists, the support substrate layer 13 can be supported more stably by die bonding at two or more locations.

  In the above description, the example in which the present invention is applied to the acceleration sensor has been described. However, the present invention may be applied to other angular velocity sensors, pressure sensors, and microphones. For example, instead of the weight body 14, a diaphragm that is a diaphragm may be supported by the support substrate layer 13.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to the thing of embodiment shown in figure. Various modifications and variations can be made to the illustrated embodiment within the same range or equivalent range as the present invention.

  The present invention can be used for a micro structure such as an acceleration sensor, an angular velocity sensor, a pressure sensor, and a microphone.

It is a figure which shows the microstructure in one Embodiment of this invention. It is a figure for demonstrating the principle which makes small the influence of the stress by this invention. It is a figure which shows the microstructure in other embodiment of this invention. It is a figure which shows the microstructure in other embodiment of this invention. It is a figure which shows the microstructure in other embodiment of this invention. It is a figure which shows the microstructure in other embodiment of this invention. It is a figure which shows the microstructure in other embodiment of this invention. It is a figure which shows the conventional microstructure. It is a figure which shows the other example of the conventional microstructure. It is a circuit diagram which shows the bridge circuit formed by the piezoresistive element in an acceleration sensor.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Sensor package, 2 Frame member, 3 Lid member, 4 Die bonding paste, 5 Metal pad, 6 Metal wire, 7 Insulating layer, 8 Buffer layer, 10, 10a-10g Micro structure, 11 Semiconductor layer, 12 Embedded insulating layer , 13 Support substrate layer, 14 weight body, 21, 24, 81, 131 recess, 22 bottom surface, 23 stepped portion, 111-114 beam.

Claims (11)

A sensor element having a support part and a movable part supported by the support part;
In a microstructure having a pedestal for mounting the sensor element,
The bottom surface of the support portion facing the pedestal is divided into four regions centered on the position of the center of gravity of the bottom surface shape, and the bottom surface of the support portion and the pedestal are joined to only one of the regions. A microstructure having a portion.   The microstructure according to claim 1, wherein the joint includes an adhesive that joins the one region between a bottom surface of the support and the pedestal.   3. The microstructure according to claim 1, wherein other regions except for the one region out of the surfaces of the support unit facing the bottom surface and the pedestal are in contact with each other. The joint includes a recess formed on one of the bottom surface of the support and the pedestal corresponding to the one region,
The adhesive joins a concave portion formed on one of the surfaces in contact with the bottom surface of the support portion and the pedestal, and one of the surfaces in contact with the bottom surface of the support portion and the pedestal. The microstructure according to claim 3. The pedestal includes a base and a buffer member that is provided on the base and absorbs stress applied from the periphery on which the support is placed,
The microstructure according to any one of claims 1 to 4, wherein the joining portion divides a surface where the bottom surface of the support portion and the buffer member are in contact with each other into four regions, and joins one of the regions. . The joint includes a recess formed in one of the bottom surface of the support and the buffer member corresponding to the one region,
6. The micro of claim 5, wherein the adhesive joins a recess formed in one of the bottom surface of the support portion and the buffer member and a bottom surface of the support portion and one of the buffer members. Structure.   The microstructure according to any one of claims 1 to 6, wherein the joining portion joins the bottom surface of the support portion and the buffer member or the pedestal at one or more places in the four divided regions.   The microstructure according to claim 1, wherein the support part includes a frame member having a space in the center and supporting the movable part via the beam member.   The microstructure according to any one of claims 1 to 8, further comprising a plurality of beam portions that support the movable portion by the support portion.   The microstructure according to claim 1, wherein the movable part is a vibrating part.   The micro structure according to claim 1, wherein the sensor element is any one of an acceleration sensor, an angular velocity sensor, a pressure sensor, and a microphone.

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