JP5089115B2 - Semiconductor sensor and manufacturing method thereof - Google Patents

Description

The present invention relates to a semiconductor sensor using a piezoresistor, such as a semiconductor acceleration sensor and a semiconductor angular velocity sensor, and a method for manufacturing the same.
The semiconductor sensor is used, for example, for measurement of acceleration in a traveling direction or a lateral direction applied to a running car, or measurement of camera shake of a video camera.

  As a semiconductor sensor, there is one in which a piezoresistor is formed on the surface of a silicon single crystal wafer by a method similar to an IC (integrated circuit) manufacturing technique and used as a strain gauge (see, for example, Patent Document 1). A semiconductor sensor using a piezoresistor provides a thin flexible part by etching or the like on the back surface of the silicon wafer in the region where the piezoresistor is formed so that the flexible part is deformed by acceleration. The electrical signal corresponding to the acceleration is obtained by measuring the resistance value of the piezoresistor that changes due to the deformation.

  The semiconductor sensor is provided with a weight portion so that the flexible portion can be easily bent. A support portion is provided around the weight portion, and one end of the flexible portion is fixed to the weight portion and the other end is fixed to the support portion. A metal wiring pattern and electrode pads electrically connected to the piezoresistor are formed on the support portion.

In addition, in order to prevent the flexible portion from being damaged by a strong impact, there is a cover plate for restricting the moving distance of the weight portion that is spaced from the flexible portion and the weight portion (for example, (See Patent Document 2, Patent Document 3, and Patent Document 4.)
In the semiconductor sensor described in Patent Document 2, concave portions for fixing the cover plate are provided at a plurality of locations on the surface of the support portion, and the cover plate is fixed to the support portion by using an adhesive in the concave portion to be a flexible portion. Cover plates are arranged on the top and the weight.
Moreover, in the semiconductor sensor described in Patent Documents 3 and 4, the cover plate is fixed to the support portion surface by anodic bonding.

9A and 9B are diagrams showing an example of a conventional semiconductor sensor, where FIG. 9A is a plan view, FIG. 9B is a cross-sectional view taken along the line AA ′ in FIG. 9A, and FIG. It is sectional drawing shown.
The semiconductor sensor 1a is formed by an SOI (Silicon on Insulator) substrate 2 composed of a silicon layer 2a, an insulating layer 2b formed under the silicon layer 2a, and a silicon layer 2c formed under the insulating layer 2b. Yes.
A flexible portion 8 made of a silicon layer 2 a is formed continuously on one surface side of the SOI substrate 2 of the frame-like support portion 6 made of the SOI substrate 2. A piezoresistor 10 is formed on the silicon layer 2 a of the flexible portion 8.
On the center side of the support portion 6, the weight portion 4 is disposed with a space from the support portion 6. One surface side of the weight part 4 is formed continuously with the flexible part 8 by the silicon layer 2 a, and the weight part 4 is supported by the flexible part 8.

An insulating film 12 is formed on one surface of the SOI substrate 2. FIG. 9A shows the piezoresistor 10 for convenience. A plurality of metal wiring patterns 20 and a plurality of electrode pads 16 are formed on the insulating film 12, and are electrically connected to the piezoresistor 10 through through holes 12 a formed in the insulating film 12. Yes.
A protective film 21 (not shown in (A)) is formed on the insulating film 12 including the formation region of the metal wiring pattern 20. An opening is formed in the protective film 21 on the electrode pad 16, and the surface of the electrode pad 16 is exposed.
The glass substrate 3 is bonded to the back surface of the support portion 6 by anodic bonding. The end face of the weight part 4 and the glass substrate 3 are spaced apart.

  A cover plate fixing region 18 is provided around the surface of the support portion 6, and a cover plate 24 made of a glass substrate is fixed to the cover plate fixing region 18 by anodic bonding. The cover plate 24 is formed with a recess 24 a at the center of the lower surface, and the surface of the recess 24 a is spaced from the weight portion 4 and the flexible portion 8.

Japanese Patent No. 2670048 JP 2004-233080 A Japanese Patent Application Laid-Open No. 2004-257832 JP 2004-233072 A JP 2003-037179 A

  In the conventional semiconductor sensor described with reference to FIG. 9, the cover plate 24 is joined to the cover plate fixing region 18 provided on the support portion 6 by anodic bonding. Anodic bonding has a simpler process than bonding with an adhesive or welded glass, and can provide stable bonding strength.

  However, when the cover plate 24 is fixed to the support portion 6 by anodic bonding, an electrostatic force is generated by a direct current applied at the time of bonding, and the weight portion 4 is attracted to the cover plate 24 and sticks to the bottom of the recess 24a. There was a problem (see FIG. 9C). For example, even when the bottom surface of the concave portion 24a of the cover plate 24 is subjected to surface processing using bead blast processing, it is impossible to prevent the weight portion 4 from sticking. Further, in bead blasting, a mask having a thickness greater than the processing depth is required, and a dry film resist must be used. Therefore, there is a problem that the manufacturing cost is higher than the method of forming a mask using a liquid resist.

When the weight portion is attached to the cover plate by anodic bonding, the weight portion cannot be easily removed from the cover plate even if a reverse bias electric field is applied or static electricity is removed. Although it is possible to remove the weight from the cover plate by vibration energy from ultrasonic cleaning or fine jet treatment, this method has a problem that the flexible part is likely to be broken and the yield is lowered. It was.
Although it may be possible to prevent the weight portion from sticking to the cover plate by increasing the distance between the weight portion and the cover plate, in this case, the weight portion is attracted to the cover plate by electrostatic force at the time of joining. The problem that a part breaks arises.

  Therefore, the present invention prevents the weight part and the cover plate from sticking to each other due to electrostatic force during anodic bonding for attaching the cover plate to the support part in the semiconductor sensor and the manufacturing method thereof, and can be easily peeled off even if attached. An object of the present invention is to provide a semiconductor sensor and a method for manufacturing the same.

  The semiconductor sensor according to the present invention is provided around the weight part, the support part having at least a silicon layer, and provided on one surface side of the support part between the weight part and the support part. A flexible portion for supporting the weight portion; a piezoresistor provided in the flexible portion; and formed on at least the one surface of the support portion and electrically connected to the piezoresistor. The metal wiring pattern and the electrode pad, and the weight part and the flexible part are disposed on the one surface side of the support part with a space between the weight part and the flexible part. A semiconductor sensor including a cover plate fixed to a cover plate fixing region provided on one surface, wherein one or a plurality of weight side protrusions provided on the surface of the weight portion on one surface side, The weight side on the inner surface of the cover plate facing the weight portion Those that have one or more of the cover-side projections provided opposite to the electromotive unit.

An example is given in which the height of the cover-side protrusion from the inner surface of the cover plate is lower than the height from the inner surface of the cover plate portion corresponding to the cover plate fixing region. it can.
Moreover, the weight side protrusion part can give the example arrange | positioned at the said one surface of the weight part vicinity just above the weight part seeing from the upper direction.

Further, only one set of the weight side protrusion and the cover side protrusion may be provided.
A plurality of sets of the weight side protrusions and the cover side protrusions may be provided.

Moreover, the cover plate is transparent to such an extent that it can transmit laser light, and the weight side projection may include a metal material.
Furthermore, the metal material of the weight side protrusion may be the same metal material as the metal wiring pattern, and the weight side protrusion may be formed simultaneously with the metal wiring pattern.

  The cover plate is transparent enough to transmit laser light, and the weight side protrusion includes a silicon film.

  The method for manufacturing a semiconductor sensor according to the present invention is a method for manufacturing a semiconductor sensor according to the present invention, wherein the cover plate is transparent enough to transmit laser light, and the weight side protrusion includes a metal material or a silicon film. In the manufacturing process of the semiconductor sensor according to the present invention, after the cover plate is fixed to the support portion by anodic bonding, the cover side protrusion and the weight side protrusion are irradiated with laser light through the cover plate. Including.

  In the semiconductor sensor of the present invention, one or a plurality of weight side protrusions provided on the surface of the weight part, and 1 provided on the inner side surface of the cover plate facing the weight part so as to face the weight side protrusion part. Since one or a plurality of cover-side projections are provided, both projections come into contact when the weight is attracted to the cover plate by electrostatic force during anodic bonding. Here, when an insulating film is formed on the weight side protrusion, the insulating film on the weight side protrusion and the cover side protrusion are in contact with each other. Therefore, the area where the weight part and the cover plate come into contact with each other can be reduced as compared with the case where both protrusion parts are not provided, and the weight part and the cover plate are prevented from sticking due to electrostatic force. It can be easily removed by applying an impact or the like.

  In the semiconductor sensor of the present invention, the height of the cover side protrusion from the inner surface of the cover plate is set to be lower than the height from the inner surface of the cover plate portion corresponding to the cover plate fixing region. For example, a predetermined interval can be formed between the cover-side protrusion and the weight-side protrusion in a state where the cover plate is fixed to the support portion.

  Further, if the weight-side protrusion is arranged on the one surface near the center of gravity of the weight as viewed from above, the one surface just above the center of gravity of the weight as viewed from above is Since it is the portion that is most easily attracted to the cover plate side during anodic bonding, it is possible to reliably prevent the weight portion and the cover plate from sticking.

  In addition, if only one set of the weight side protrusion and the cover side protrusion is provided, the weight side protrusion at the time of anodic bonding is compared to the case where a plurality of sets of the weight side protrusion and the cover side protrusion are provided. It is possible to reduce the contact area between the cover portion and the cover-side protrusion, prevent the weight portion and the cover plate from sticking, and easily peel off even if they stick.

  Further, if a plurality of sets of weight side protrusions and cover side protrusions are provided, it is possible to prevent the weight portion and the cover plate from sticking at a plurality of locations during anodic bonding.

  Also, if the cover plate is transparent enough to transmit laser light and the weight side protrusion includes a metal material, the weight side protrusion and the cover side protrusion stick to each other during anodic bonding. Even in this case, the cover-side protrusion and the weight-side protrusion may be peeled off by irradiating the cover-side protrusion and the weight-side protrusion with laser light through the cover plate to destroy the weight-side protrusion. it can.

  Furthermore, if the metal material of the weight side protrusion is the same metal material as the metal wiring pattern and the weight side protrusion is formed at the same time as the metal wiring pattern, the weight can be increased without increasing the manufacturing process. Side protrusions can be formed.

  Also, if the cover plate is transparent enough to transmit laser light and the weight side protrusion includes a silicon film, the weight side protrusion and the cover side protrusion will stick together during anodic bonding. Even in this case, the cover-side protrusion and the weight-side protrusion may be peeled off by irradiating the cover-side protrusion and the weight-side protrusion with laser light through the cover plate to destroy the weight-side protrusion. it can.

  In the method for manufacturing a semiconductor sensor of the present invention, the cover plate is transparent to the extent that it transmits laser light, and the weight side protrusion includes a metal material or a silicon film. Is attached to the support portion by anodic bonding, and then includes a step of irradiating the cover-side protrusion and the weight-side protrusion through the cover plate with laser light, so that the weight-side protrusion and the cover-side protrusion at the time of anodic bonding are included. Even if the part is stuck, the cover-side protrusion and the weight are destroyed by irradiating the cover-side protrusion and the weight-side protrusion through the cover plate with laser light to destroy the weight-side protrusion. The side protrusion can be peeled off.

  1A and 1B are diagrams showing an embodiment of a semiconductor sensor, in which FIG. 1A is a plan view, FIG. 1B is a sectional view taken along the line AA ′ in FIG. 1A, and FIG. It is sectional drawing in a B 'position. FIG. 2 is an enlarged sectional view showing the vicinity of the impurity diffusion layer 28 used as wiring in the semiconductor sensor of FIG. This embodiment will be described with reference to FIGS.

  The semiconductor sensor 1 is configured by an SOI substrate 2 having a planar size of 2.0 × 2.5 mm (millimeters) and a thickness of 400 μm (micrometers), for example. The SOI substrate 2 includes a silicon layer 2a located on the upper surface side, an insulating layer 2b formed under the silicon layer 2a, and a silicon layer 2c formed under the insulating layer 2b. The silicon layer 2a is N-type by introducing N-type impurity ions such as phosphorus.

A weight 4 is formed at the center of the SOI substrate 2 as viewed from above, which is displaced when acceleration is applied. The weight portion 4 is formed of a silicon layer 2a, an insulating layer 2b, and a silicon layer 2c.
A frame-like support portion 6 is formed around the weight portion 4 so as to be spaced from the weight portion 4 and support the weight portion 4. The support portion 6 is formed by the silicon layer 2a, the insulating layer 2b, and the silicon layer 2c.
A pedestal 7 made of a glass substrate is joined to the lower surface of the silicon layer 2b of the support 6 by anodic bonding with a distance from the lower surface of the weight 4.

A flexible portion 8 having one end connected to the weight portion 4 and the other end connected to the support portion 6 is formed on one surface side of the SOI substrate 2. The flexible part 8 is formed by the silicon layer 2a.
In the flexible part 8, a piezoresistor 10 whose resistance value changes according to the strain of the flexible part 8 is formed in the silicon layer 2a. The piezoresistor 10 is formed by a P-type diffusion layer formed by introducing, for example, boron, which is a P-type impurity ion.

  The weight part 4, the support part 6, and the flexible part 8 are connected by the silicon layer 2a. Thereby, the weight part 4 is supported by the support part 6 via the flexible part 8. When the weight portion 4 is displaced with respect to the support portion 6, the flexible portion 8 is deformed and the resistance value of the piezoresistor 10 changes.

  On the surface of the silicon layer 2a, an insulating film 12 made of, for example, an NSG (non-doped silicon glass) film or a BPSG (boron phosphorus silicon glass) film having a film thickness of 0.8 μm is formed. On the insulating film 12, a plurality of metal wiring patterns 14 and a plurality of electrode pads 16 made of, for example, aluminum having a film thickness of 1.0 μm are formed. The electrode pads 16 are arranged side by side in the vicinity of the peripheral edge at one end of the support portion 6. The metal wiring pattern 14 has, for example, a line width of 1.4 μm and a pitch of 1.5 μm, and the planar size of the electrode pad 16 is, for example, 70 × 70 μm to 100 × 100 μm.

  Here, the electrode pad 16 having a square shape in plan view is shown, but the electrode pad 16 may be larger than that shown in FIG. It may be rectangular. Further, the arrangement of the electrode pads 16 is not limited to that arranged in the vicinity of the peripheral edge at one end of the support portion 6. For example, the arrangement of the electrode pads 16 is arbitrary, such as being arranged in the vicinity of a plurality of sides of the support portion 6.

  Through holes 12 a are formed in the insulating film 12 corresponding to both ends of the piezoresistor 10. The metal wiring pattern 14 is electrically connected to the piezoresistor 10 through the through hole 12a. Although illustration is omitted, boron, which is a P-type impurity ion, is introduced at a high concentration into a portion corresponding to the through hole 12a of the piezoresistor 10 to reduce the contact resistance with the metal wiring pattern 14.

A cover plate fixing region 18 is provided on the support portion 6 so as to surround the formation region of the weight portion 4 and the flexible portion 8.
Dummy patterns 20, 20 a and 20 b are formed on the insulating film 12 in regions different from the metal wiring pattern 14 and the electrode pad 16. The dummy patterns 20, 20 a, and 20 b are formed simultaneously with the metal wiring pattern 14 and the electrode pad 16.
The dummy pattern 20 a is disposed in the cover plate fixing region 18 so as to surround the weight portion 4 and the flexible portion 8.

  The dummy pattern 20 b is formed in the flexible portion 8 and has substantially the same line width as the metal wiring pattern 14. The arrangement area and the line width of the dummy pattern 20b are set so that the strength of the flexible portion 8 is approximately the same as the longitudinal center line of the flexible portion 8 and is twisted in the short direction of the flexible portion 8 in a stationary state. It is set so as not to cause deformation. Here, the stationary state refers to a state where the semiconductor sensor is stationary with the upper surface of the semiconductor sensor being horizontally disposed. Further, the symmetry of multi-axis sensitivity means the detection sensitivity with respect to one direction and the symmetry of detection sensitivity with respect to a direction opposite to that direction by 180 degrees. For example, a horizontally disposed semiconductor sensor is expressed as X This is the symmetry of the detection sensitivity in the Y-axis direction when rotated 90 degrees to the right about the axial direction and the detection sensitivity in the Y-axis direction when rotated 90 degrees to the left.

In a predetermined region of the silicon layer 2a under the dummy pattern 20a, an impurity diffusion layer 28 used as a wiring for guiding the potential of the metal wiring pattern 14 to the outside of the region surrounded by the dummy pattern 20a is formed (FIG. 1 (A) and FIG. 2).
A through hole 12c is formed in the insulating film 12 on the end portion of the impurity diffusion layer 28 on the region side surrounded by the dummy pattern 20a. The metal wiring pattern 14 is electrically connected to one end of the impurity diffusion layer 28 through the through hole 12b.
A through hole 12c is formed in the insulating film 12 on the end portion of the impurity diffusion layer 28 outside the region surrounded by the dummy pattern 20a. Outside the region surrounded by the dummy pattern 20a, the metal wiring pattern 14a is electrically connected to the other end of the impurity diffusion layer 28 through the through hole 12c. The other end of the metal wiring pattern 14 a is connected to the electrode pad 16.

The potential of the metal wiring pattern 14 is guided to the metal wiring pattern 14a through the through hole 12b, the impurity diffusion layer 28, and the through hole 12c.
The dummy patterns 20 and 20a are electrically connected to the silicon layer 2a through the through hole 12a in a region different from the region where the impurity diffusion layer 28 is formed, and have the same potential as the silicon layer 2a. No through hole is formed under the dummy pattern 20b.

  On the insulating film 12 on the weight 4, a weight side protrusion 21 made of a metal material is provided. The weight side protrusion 21 is formed of the same material as the metal wiring pattern 14, the electrode pad 16, and the dummy pattern 20 at the same time, and has a thickness of, for example, 1.0 μm. A through hole is not formed in the insulating film 12 below the weight side protrusion 21, and the weight side protrusion 21 is electrically independent. In this embodiment, a total of 13 weight sides, one at the center of the weight part 4 (just above the center of gravity of the weight part 4) and three near each of the four corners of the weight part 4 when viewed from above. The protrusion 21 is arranged.

  The planar shape of the weight side protrusion 21 is, for example, a square having a side of 6 to 8 μm. In the semiconductor sensor of the present invention, the formation area of one weight side protrusion is larger than the laser spot size and has a single laser beam when the spot size of the laser beam at the time of laser irradiation described later is 4 to 5 μm. The size is preferably 4 to 12 μm × 4 to 12 μm, and more preferably 6 to 8 μm × 6 to 8 μm so that it can be blown by irradiation. In the semiconductor sensor of the present invention, the planar shape of the weight side protrusion may be other shapes such as a rectangle other than a square, an H shape, a cross shape, and the like.

  An insulating film 22 (not shown in (A)) is formed as a final protective film on the insulating film 12 so as to cover the metal wiring pattern 14, the dummy pattern 20, and the weight side protrusion 21. The insulating film 22 has an opening on the electrode pad 16, and the surface of the electrode pad 16 is exposed. The insulating film 22 on the metal wiring pattern 14, the dummy pattern 20, and the weight side protrusion 21 protrudes more than the insulating film 22 on the weight 4 other than the area where the weight side protrusion 21 is formed.

  A cover plate 24 is disposed above the weight part 4 and the flexible part 8 with a distance from the weight part 4 and the flexible part 8. The cover plate 24 is, for example, a Pyrex glass 7740 with a thickness of about 300 μm (a product of Corning (USA), a Pyrex is a registered trademark) or a borofloat 33 (a product of Schott (Germany), and a borofloat is a registered trademark of Schott. ).

The cover glass 24 includes a recess 24 a on the inner surface so that a surface (inner surface) facing the weight portion 4 and the flexible portion 8 has a predetermined distance from the weight portion 4 and the flexible portion 8. The depth of the recess 24 a is, for example, 15 μm and is adjusted according to the length of the flexible portion 8.
The peripheral edge of the cover plate 24 (the portion where the recess 24a is not formed) is joined to the cover plate fixing region 18 by anodic bonding.

  A cover-side protrusion 24b is formed on the surface of the recess 24a at a position facing the weight-side protrusion 21. The cover side protrusions 24b are provided corresponding to the respective weight side protrusions 21, and in this embodiment, 13 cover side protrusions 24b are provided. For example, the cover side protrusion 24b is formed of a substantially quadrangular pyramid, and the dimensions of the bottom surface of the cover side protrusion 24b are 7 μm × 7 μm and the height is 15 μm. Since the height of the peripheral edge of the cover plate 24 (portion joined to the cover plate fixing region 18) is the same as the depth (15 μm) of the recess 24a, the cover-side protrusion 24b with respect to the inner surface of the recess 24a. Is formed lower than the peripheral edge of the cover plate 24.

  The cover plate 24 is preferably made of a material having a linear expansion coefficient close to that of silicon, for example, Pyrex glass (Pyrex is a registered trademark) or Borofloat 33 (Borofloat is a registered trademark of Schott). Thereby, the deformation of the flexible portion 8 due to the residual stress after anodic bonding can be prevented, and the offset voltage of the piezoresistor 10 can be reduced. Furthermore, since the support 6 is hardly distorted even if the ambient temperature varies, it is possible to form a high-performance semiconductor sensor with little variation in characteristics due to a change in ambient temperature.

The semiconductor sensor 1 is formed by etching an SOI substrate 2. The manufacturing process will be briefly described.
An SOI in which a piezoresistor 10 is formed on a silicon layer 2a, and an insulating film 12, a through hole 12a, a metal wiring pattern 14, an electrode pad 16, dummy patterns 20, 20a, 20b, and an insulating film 22 are formed on the silicon layer 2a. The silicon layer 2c, the insulating layer 2b, the silicon layer 2a, and the insulating film 22 of the substrate 2 are etched from the silicon layer 2c side to form the weight portion 4, the support portion 6, and the flexible portion 8. The etching process is performed, for example, in two stages.

  First, a resist pattern having openings in the region between the weight portion 4 and the support portion 6 and the region corresponding to the flexible portion 8 is formed on the back surface of the SOI substrate 2 (the surface on the silicon layer 2c side). The silicon layer 2c is etched using the resist pattern as a mask. At that time, the insulating layer 2b functions as an etching stopper layer, and the silicon layer 2c is etched to a depth where the insulating layer 2b is formed. After removing the resist pattern, the exposed region of the insulating layer 2b is removed. Therefore, in FIG. 1, the insulating layer 2 b does not exist under the silicon layer 2 a of the flexible portion 8.

  Thereafter, in order to separate the weight portion 4 from the support portion 6, the silicon layer 2a and the insulating film 22 in a predetermined region excluding the region where the flexible portion 8 is to be formed are etched away from the back surface side by photolithography and etching technology. The Thereby, the weight part 4, the support part 6, and the flexible part 8 are formed.

After the etching process is completed, the cover plate 24 is bonded to the cover plate fixing region 18 of the support portion 6 by anodic bonding.
3A and 3B are views showing a state at the time of anodic bonding, where FIG. 3A is a cross-sectional view at the position AA ′ in FIG. 1A, and FIG. It is sectional drawing which expands and shows the vicinity of a side projection part and a cover side projection part.

  In the anodic bonding process, a positive electric potential is applied to the N-type silicon layer 2a and a negative electric potential is applied to the cover plate 24 to apply a DC electric field. Since the dummy patterns 20 and 20a have the same potential as the silicon layer 2a, the portions where the dummy patterns 20 and 20a are in contact with the cover plate 24 are joined. At this time, as shown in FIG. 3, the weight part 4 and the flexible part 8 are attracted to the cover plate 24 side by electrostatic force.

When the weight part 4 and the flexible part 8 are sucked toward the cover plate 24, the insulating film 22 on the weight side protrusion 21 and the cover side protrusion 24b come into contact with each other as shown in FIG. 3, the insulating film 22 on the weight side protrusion 21 and the cover side protrusion 24b are also in contact with each other at the periphery of the weight 4 which is not shown in FIG.
Thereby, compared with the case where both the protrusion parts 21 and 24b do not exist, the area which the weight part 4 and the cover board 24 contact can be made small, and it can prevent that the weight part 4 and the cover board 24 stick. . Further, even if the insulating film 22 on the weight side protrusion 21 and the cover side protrusion 24b are attached, they can be easily peeled off by applying a light vibration or impact.

In this embodiment, the weight side protrusion 21 is formed of the same metal material as that of the metal wiring pattern 14 and the dummy pattern 20 at the same time. Therefore, a dedicated process for forming the weight side protrusion 21 is not required. Cost reduction can be achieved.
Furthermore, since the weight side protrusion 21 is electrically independent of the metal wiring pattern 14, the dummy pattern 20, and the silicon layer 2a, even if the weight side protrusion 21 contacts the cover plate 24 during anodic bonding, silicon No current flows from the layer 2 a through the weight side protrusion 21 to the cover plate 24, and the weight side protrusion 21 can be prevented from sticking to the cover plate 24.

By the way, even if the area where the weight part 4 and the cover plate 24 are brought into contact with each other is reduced by the weight side protrusion part 21 and the cover side protrusion part 24b, the insulating film 22 on the weight side protrusion part 21 and the cover side protrusion part 24b are adhered. It may not peel off even when subjected to light vibration or impact.
Therefore, the method for manufacturing a semiconductor sensor according to the present invention includes a step of irradiating the weight-side protrusion and the cover-side protrusion with laser light to peel off the weight-side protrusion and the cover-side protrusion.

  FIG. 4 is a process sectional view for explaining an embodiment of the manufacturing method. FIG. 4 corresponds to the position of FIG. The parenthesized numbers in FIG. 4 correspond to the steps described below.

(1) In the anodic bonding process for bonding the cover plate 24 to the cover plate fixing region 18 of the support portion 6, the weight portion 4 and the flexible portion 8 are attracted to the cover plate 24 side, and on the weight side projection portion 21. The insulating film 22 and the cover-side protrusion 24b come into contact with each other. Even after the voltage application is stopped, the insulating film 22 on the weight side protrusion 21 and the cover side protrusion 24b may be adhered.

(2) The cover-side protrusion 24b, the insulating film 22, and the weight-side protrusion 21 are irradiated with laser light 26 through the cover plate 24. As a result, the weight side protrusion 21 and the insulating film 22 on the weight side protrusion 21 are destroyed. Here, the laser beam 26 having a wavelength near 1300 kHz and a spot system of 4 to 5 μm was used.

(3) The irradiation of the laser beam 26 is stopped. When the weight-side protrusion 21 and the insulating film 22 on the weight-side protrusion 21 are broken, the weight 4 moves to the side opposite to the cover plate 24 and stops at the position of the stationary state.

  Thus, even when the insulating film 22 on the weight side protrusion 21 and the cover side protrusion 24b are adhered to each other during the anodic bonding, the cover side protrusion 24b and the insulating film 22 are interposed via the cover plate 24. The cover-side protrusion 24b and the weight-side protrusion are formed by irradiating the weight-side protrusion 21 with the laser beam 26 to destroy the weight-side protrusion 21 and the insulating film 22 on the weight-side protrusion 21. 21 can be peeled off.

  FIG. 5 is a process cross-sectional view for explaining an example of the manufacturing method of the cover plate. The numbers in parentheses in FIG. 4 correspond to the steps described below.

(1) A photosensitive liquid resist is applied on one surface of the cover plate 24, and the photosensitive liquid resist is subjected to exposure processing, development processing, and cleaning processing to form resist patterns 28a and 28b. The resist pattern 28a is arranged corresponding to the peripheral edge of the cover plate 24, and has an opening corresponding to the recess 24a (see FIG. 1) of the cover plate 24. The resist pattern 28b is arranged corresponding to the cover-side protrusion 24b (see FIG. 1) formed in the recess 24a of the cover plate 24. The resist pattern 28b is removed during the etching process on the cover plate 24, and the planar area and thickness are adjusted so that a desired cover-side protrusion 24b is obtained.

(2) The cover plate 24 is etched using the resist patterns 28a and 28b as a mask by an anisotropic etching technique. As the etching progresses, a recess 24 a and a cover-side protrusion 24 b are formed in the cover plate 24. The resist patterns 28a and 28b are also etched from the upper surface side at an etching rate smaller than that of the cover plate 24. The resist pattern 28b has a smaller plane area than the resist pattern 28a, and the plane area is adjusted so as to be removed during the etching process, so that the film thickness becomes faster than the resist pattern 28a.

(3) When etching further proceeds, the recess 24a is formed deeper. Then, the resist pattern 28b is removed. The cover-side protruding portion 24b is formed in a quadrangular pyramid having a substantially square bottom surface.

(4) When the etching further proceeds, the recess 24a is formed deeper. The upper part of the cover side protrusion 24 b is also etched, and the position of the tip becomes lower than the peripheral edge of the cover plate 24. After performing the etching process for a predetermined time,

(5) After performing the etching process for a predetermined time, the resist pattern 28a is removed.
Thereby, the cover plate 24 in which the height of the cover-side protrusion 24 b is lower than the peripheral edge of the cover plate 24 can be formed.
Further, when the concave portion is formed by the bead blasting process, it is difficult to visually observe the inside of the semiconductor sensor through the cover plate, but the cover plate 24 formed by the etching process can visually observe the inside of the semiconductor sensor.

Here, the method of forming the recess 24a and the cover-side protrusion 24b by the anisotropic etching technique has been described, but the recess and the cover-side protrusion may be formed by isotropic etching.
In the semiconductor sensor of the present invention, the cover plate is not limited to one formed by an etching technique.

  Further, the resist pattern 28b corresponding to the cover-side protrusion 24b is removed during the etching process so that the position of the tip of the cover-side protrusion 24b is lower than the peripheral edge of the cover plate 24. The position of the tip of the cover-side protrusion 24b may be lower than the peripheral edge of the cover plate 24 by other methods.

  For example, a resist pattern that covers the peripheral portion and has an opening in a region where the concave portion 24 and the cover-side protrusion 24b are to be formed is formed. After the concave portion 24 is formed to a certain depth, the resist pattern is temporarily removed and the cover side An etching process may be performed by re-forming a resist pattern that covers the region where the projection 24b is to be formed and the peripheral edge and has an opening in the recess 24.

  Also, after the formation region and peripheral edge of the cover-side protrusion 24b are covered, a resist pattern having an opening is formed in the recess 24, the recess 24 is formed to a certain depth, and the cover-side protrusion 24b is formed Alternatively, the resist pattern may be temporarily removed, and the etching process may be performed by re-forming a resist pattern that covers the peripheral edge and has an opening in a region where the recess 24 and the cover-side protrusion 24b are to be formed.

  6A and 6B are diagrams showing another embodiment of the semiconductor sensor, in which FIG. 6A is a plan view, FIG. 6B is a cross-sectional view taken along the line AA ′ in FIG. It is sectional drawing in position -B '. In FIG. 6, the same parts as those in FIG.

This embodiment is different from the embodiment described with reference to FIG. 1 in that only one weight side projection 21 is arranged near the center of gravity of the weight 4 as viewed from above, and the cover side projection Only one portion 24b is disposed to face the weight side protrusion 21.
According to this embodiment, since the portion directly above the center of gravity of the weight portion 4 when viewed from above is the portion that is most likely to be sucked toward the cover plate 24 during anodic bonding, the weight portion 4 and the cover plate 24 are reliably attached. Can be prevented.

  Furthermore, since only one set of the weight side protrusion 21 and the cover side protrusion 24b is provided, the weight side protrusion 21 and the cover side protrusion 24b are provided on the weight side during anodic bonding, as compared with the case where a plurality of sets of the weight side protrusion 21 and the cover side protrusion 24b are provided. The area where the protrusion 21 and the cover-side protrusion 24b come into contact can be reduced, and the weight 4 and the cover plate 21 can be prevented from sticking and can be easily peeled off even if they stick.

  However, the arrangement of the weight side protrusion 21 and the cover side protrusion 24b is not limited to the embodiment shown in FIG. 1 and the embodiment shown in FIG. The number and arrangement of the weight-side protrusions and cover-side protrusions are arbitrary, such as arranging a plurality of sets of weight-side protrusions and cover-side protrusions directly above the portion.

  In the above embodiment, the weight side protrusion 21 is formed at the same time as the metal wiring pattern 20, but the present invention is not limited to this, and the protrusion is formed in a separate process from the metal wiring pattern. It may be made of a metal material, for example, a metal material generally used for a wiring pattern or a metal material used for a resistance element, or may be formed of a silicon film.

  7A and 7B are diagrams showing still another embodiment of the semiconductor sensor, where FIG. 7A is a plan view, FIG. 7B is a cross-sectional view taken along the line AA ′ in FIG. It is sectional drawing in a BB 'position. In FIG. 6, the same parts as those in FIG.

This embodiment differs from the embodiment described with reference to FIG. 1 in that a weight side protrusion 30 made of a polysilicon film is formed instead of the weight side protrusion 21 made of a metal material. . The thickness of the weight side protrusion 30 is, for example, 1.0 μm. Moreover, the planar shape of the weight side projection part 30 is a square whose one side is 6 to 8 μm, for example. The weight side protrusion 30 is formed on the silicon layer 2 a via an insulating film (not shown) and is covered with the insulating film 12.
In this embodiment as well, as in the embodiment shown in FIG. 1, it is possible to reliably prevent the weight portion 4 and the cover plate 24 from sticking, and even if they stick, they can be easily peeled off.

In the embodiment shown in FIG. 7, polysilicon is used as the material of the weight side protrusion 30, but the material of the weight side protrusion may be amorphous silicon.
Similarly to the embodiment shown in FIG. 3, only one set of the weight side protrusion 30 and the cover side protrusion 24b may be provided.

  Further, when the weight side protrusion 30 made of the polysilicon film is destroyed by laser light irradiation as in the embodiment of the manufacturing method described with reference to FIG. 4, the laser light used for irradiation is, for example, around 1042 kHz, a spot A system of 4 to 5 μm can be used.

  FIG. 8 is a sectional view showing still another embodiment of the semiconductor sensor. In FIG. 8, the same parts as those in FIG. Since the semiconductor sensor is the same as that shown in FIG.

  In this embodiment, a MOS transistor, a resistance element 34, and a fuse element 36 are provided on the silicon layer 2a of the support portion 6 at a position different from that of the semiconductor sensor 1.

  The MOS transistor includes a P-type source diffusion layer 32s and a P-type drain diffusion layer 32d formed at intervals in an N-type well (not shown) formed in the N-type silicon layer 2a, a diffusion layer 32s, and a diffusion layer 32d. It is of the P channel type provided with a gate electrode 32g made of a polysilicon film formed on a silicon layer 2a between them via a gate insulating film (not shown). Although not shown, a through hole is formed in the insulating film 12 on the gate electrode 32g and the diffusion layers 32s and 32d, and the gate electrode 32g and the diffusion layers 32s and 32d are electrically connected to the signal wiring pattern 14. Yes. In other regions, a P-type well is formed in the N-type silicon layer 2a, and an N-channel MOS transistor is formed in the P-type well.

  The resistance element 34 is formed of a polysilicon film formed on the silicon layer 2a via an element isolation insulating film (not shown). Although illustration is omitted, through holes are formed in the insulating film 12 on both ends of the resistance element 34, and both ends of the resistance element 34 are electrically connected to the signal wiring pattern 14. A plurality of resistance elements 34 are formed in other regions.

  The fuse element 36 is also formed of a polysilicon film formed on the silicon layer 2a via an element isolation insulating film (not shown). An opening is formed in the insulating films 12 and 22 on the fuse element 36 to form a trimming opening 38. Although not shown, through holes are formed in the insulating film 12 on both ends of the fuse element 36, and both ends of the resistance element 34 are electrically connected to the signal wiring pattern 14. A plurality of fuse elements 36 and trimming openings 38 are formed in other regions.

  The MOS transistor, the resistance element 34, and the fuse element 36 constitute an IC unit. For example, a signal processing circuit is formed by MOS transistors. A resistance circuit (see, for example, Patent Document 5) capable of adjusting the resistance value is formed by the resistance element 34 and the fuse element 36.

Another embodiment of the manufacturing method will be described with reference to FIG.
(1) A quality test of the semiconductor sensor 1 is performed in a wafer state on the formation region of the semiconductor sensor 1. The quality test of the semiconductor sensor 1 is performed by bringing a probe needle into contact with the pad electrode 16 connected to the piezoresistive element 10 and applying a voltage to the piezoresistive element 10. Examples of the test item include measurement of a diffusion resistance value of the piezoresistive element 10 and measurement of an offset voltage of a Wheatstone bridge of the piezoresistive element 10. By giving vibration at the time of measurement, the weight part 4 and the flexible part 8 are vibrated, and pass / fail judgment is performed based on the fluctuation of the offset voltage.

(2) In the pass / fail test of the semiconductor sensor 1, there is a possibility that the cover plate 24 and the weight portion 4 are stuck in the semiconductor sensor 1 that is out of the management standard by measuring the offset voltage of the Wheatstone bridge of the piezoresistive element 10. high. Therefore, using the laser trimming apparatus, as described with reference to FIG. 4, the cover side protrusion 24b and the weight side protrusion 21 are irradiated with laser light to destroy the weight side protrusion 21, so that the cover plate 24 and the weight The sticking of the part 4 is peeled off. Thereby, the yield of the semiconductor sensor 1 can be improved.

(3) A characteristic test of a semiconductor sensor device comprising a set of the semiconductor sensor 1 and the IC unit is performed. In the characteristic test of the semiconductor sensor device, the probe needle is brought into contact with the pad electrode 16 to measure the electric characteristic, and the characteristic is stored for each semiconductor sensor device. As a result, the fuse element 36 to be cut through the trimming opening 38 in the IC portion is determined for each semiconductor sensor device, and data is stored for each semiconductor sensor device.

(4) Based on the result of the characteristic test of the semiconductor sensor device in the step (3), the predetermined fuse element 36 is irradiated with laser light through the trimming opening 38 for each semiconductor sensor device to perform the trimming process. . By adjusting the output characteristics of the semiconductor sensor device, the reliability of the output of the semiconductor sensor device can be improved.

  As mentioned above, although the Example of this invention was described, material, a dimension, a shape, arrangement | positioning, etc. are examples, and this invention can be variously changed within the range described in the claim.

For example, the above embodiment is a semiconductor sensor made of an SOI substrate, but the semiconductor sensor may be made of another substrate material such as a bulk silicon substrate. Further, the insulating layer 2 b may remain in the flexible portion 8.
Moreover, although the insulating film 22 is formed on the weight part 4, the support part 6, and the flexible part 8, the insulating film 22 does not need to be formed.
The present invention can also be applied to a semiconductor sensor having a multilayer metal wiring structure.

In the above embodiment, the semiconductor sensor 1 is provided with a piezoresistive semiconductor sensor in which the flexible portion 8 is exposed on the surface of the semiconductor sensor 1, but the present invention is not limited to this. However, the semiconductor sensor of the present invention may be one in which a flexible portion such as a diaphragm or a cantilever is not exposed on the surface of the semiconductor sensor, or one using a piezoelectric element or two electrode plates. It may be one that utilizes the capacitance between them.
The semiconductor sensor is not limited to a triaxial semiconductor acceleration sensor, and may be a semiconductor pressure sensor or a semiconductor speed sensor.

It is a figure which shows one Example of a semiconductor sensor, (A) is a top view, (B) is sectional drawing in the AA 'position of (A), (C) is a BB' position of (A). FIG. 3 is an enlarged cross-sectional view showing the vicinity of an impurity diffusion layer 28 used as a wiring in the same embodiment. FIG. It is a figure which shows the state at the time of anodic bonding of the Example, (A) is sectional drawing in the AA 'position of FIG. 1 (A), (B) is on the center part of the weight part of (A). It is sectional drawing which expands and shows the vicinity of the weight side projection part and the cover side projection part. It is process sectional drawing for demonstrating one Example of a manufacturing method. It is process sectional drawing for demonstrating an example of the manufacturing method of a cover board. It is a figure which shows the other Example of a semiconductor sensor, (A) is a top view, (B) is sectional drawing in the AA 'position of (A), (C) is BB' of (A). It is sectional drawing in a position. It is a figure which shows other Example of a semiconductor sensor, (A) is a top view, (B) is sectional drawing in the AA 'position of (A), (C) is BB of (A). It is sectional drawing in a 'position. It is sectional drawing which shows other Example of a semiconductor sensor. It is a figure which shows an example of the conventional semiconductor sensor, (A) is a top view, (B) is sectional drawing in the AA 'position of (A), (C) is sectional drawing which shows the state at the time of anodic bonding It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 SOI substrate 2a, 2c Silicon layer 2b Insulating layer 4 Weight part 6 Support part 7 Base 8 Flexible part 10 Piezoresistor 14 Metal wiring pattern 16 Electrode pad 18 Cover board fixing area 21 Weight side protrusion part 24 Cover board 24a Cover board Recess (inside surface)
24b Projection on the cover side

Claims (4)

A weight part, a support part provided around the weight part, having at least a silicon layer, and provided on one surface side of the support part between the weight part and the support part to support the weight part A flexible part, a piezoresistor provided in the flexible part, a metal wiring pattern and an electrode pad formed on at least the one surface of the support part and electrically connected to the piezoresistor A cover plate disposed on the one surface side of the support portion above the weight portion and the flexible portion and spaced from the weight portion and the flexible portion on the one surface side of the support portion. In a semiconductor sensor having a cover plate fixed to a fixed region,
One or more weight side protrusions provided on the surface of the weight portion on the one surface side;
One or more cover side protrusions provided on the inner side surface of the cover plate facing the weight part so as to face the weight side protrusion ,
The weight-side projection includes a metal material , and the metal material is electrically independent . The semiconductor sensor according to claim 1, wherein the cover plate and the cover side protrusion are transparent to the extent that laser light is transmitted. The semiconductor sensor according to claim 1, wherein an insulating film is formed on the weight side protrusion. A weight part, a support part provided around the weight part, having at least a silicon layer, and provided on one surface side of the support part between the weight part and the support part to support the weight part A flexible part, a piezoresistor provided in the flexible part, a metal wiring pattern and an electrode pad formed on at least the one surface of the support part and electrically connected to the piezoresistor A cover plate disposed on the one surface side of the support portion above the weight portion and the flexible portion and spaced from the weight portion and the flexible portion on the one surface side of the support portion. A cover plate fixed to the fixing area;
One or more weight side protrusions provided on the surface of the weight portion on the one surface side;
One or more cover side protrusions provided on the inner side surface of the cover plate facing the weight part so as to face the weight side protrusion,
The cover plate and the cover side protrusion are transparent to the extent that laser light is transmitted,
The weight side protrusion is a method of manufacturing a semiconductor sensor including a metal material or a silicon film ,
A method of manufacturing a semiconductor sensor, comprising: irradiating the cover-side protrusion and the weight-side protrusion through the cover plate after the cover plate is fixed to the support portion by anodic bonding.

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