JP2011108680A - Method of manufacturing multilayer substrate, method of manufacturing diaphragm, and method of manufacturing pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a multilayer substrate suppressing a through-hole caused by crystal defects in a crystal substrate, to provide a method of manufacturing a diaphragm, and to provide a method of manufacturing a pressure sensor. <P>SOLUTION: The method of manufacturing the multilayer substrate 400 includes: a process for of forming a junction layer 105 between substrates by bonding first and second crystal substrates 100, 200; and a process for of forming a thin part 205 by etching the first and/or second crystal substrates 100, 200 toward the junction layer 105. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a laminated substrate, a method for manufacturing a diaphragm, and a method for manufacturing a pressure sensor, in particular, which suppress a through-hole caused by crystal defects in a quartz substrate.

  Patented as a pressure sensor comprising a diaphragm as a pressure receiving means having a flexible part that receives and deflects the pressure to be measured, and a double tuning fork vibrating piece as a pressure sensing element supported and fixed to the support part of the diaphragm Document 1 is disclosed.

  FIG. 9 is an explanatory view of a conventional pressure sensor, (A) is a cross-sectional view of the pressure sensor, and (B) is an AA arrow view of (A). In the pressure sensor 1 disclosed in Patent Document 1, when the diaphragm 2 receiving pressure is bent, a force resulting from the bending is transmitted to the double tuning fork vibrator 4 via the support portion 3, and the double tuning fork vibrator The bending of 4 also causes an expansion / contraction action in the direction of the vibrating arm (beam) 5 of the vibrator. A change occurs in the resonance frequency of the double tuning fork vibrator 4 due to the internal stress generated by the stretching action. By converting the change in the resonance frequency into the change in pressure, the pressure fluctuation can be detected.

Since the pressure sensor can detect a change in pressure as described above, the altitude can be detected by detecting a change in atmospheric pressure. By using altitude detection information by a pressure sensor in a navigation system such as PND (Personal Navigation Device), it is difficult to determine the height direction that is difficult to determine with only planar GPS information such as the floor of a building, for example, the top and bottom of a three-dimensional intersection. The accuracy with respect to the position information can be improved.
In addition, when performing human navigation, it is necessary to detect altitude with higher accuracy than a car or the like. In order to detect altitude information with high accuracy, it is necessary to detect changes in pressure with high sensitivity.

JP 2007-327922 A

  One method for improving the sensitivity of the pressure sensor is to increase the area of the diaphragm. When the area of the diaphragm is increased, the amount of displacement of the diaphragm increases, a large force is applied to the pressure-sensitive element connected to the diaphragm, and even a minute change can be detected as a large frequency change. .

  However, if the area of the diaphragm is increased, the element area is also increased. Therefore, it is not desirable in consideration of mounting on a portable terminal that is required to be downsized such as a navigation system.

  On the other hand, as another method for improving the sensitivity of the pressure sensor, there is a method of reducing the thickness of the diaphragm. When the diaphragm thickness is reduced, the amount of displacement of the diaphragm increases, so that a large force is applied to the pressure-sensitive element connected to the diaphragm, and even a minute change can be detected as a large frequency change.

Here, examples of processing methods for reducing the thickness of the diaphragm include polishing, sandblasting, and etching.
Usually, the pressure sensor has a concavo-convex structure in which a diaphragm is provided with a thin part and a thick part, and therefore processing by polishing is difficult.

  In the sandblasting process, when the diaphragm is thinned, there is a problem in that the yield of the diaphragm is reduced because the diaphragm itself is damaged by the impact of the abrasive grains colliding with the base material.

  On the other hand, the etching process is suitable for the processing of the diaphragm because it does not cause damage like sandblasting and can form irregularities. However, the etch channel existing in the material is expanded. Here, the etch channel is a region where a linear defect formed in the Z-axis direction appears on the surface of the substrate, where the chemical strength against the etchant is weak, and etching progresses preferentially and penetrates the substrate. Refers to the formed hole. For this reason, a through-hole is generated in the diaphragm, the inside and outside of the diaphragm are connected, and there is a problem that a pressure change cannot be detected.

  Accordingly, the present invention provides a method for manufacturing a laminated substrate, a method for manufacturing a diaphragm, and a method for manufacturing a pressure sensor in which the generation of through-holes due to etching of the quartz substrate is suppressed in order to solve the above-described problems of the prior art. It is aimed.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.
Application Example 1 A step of bonding the first and second quartz crystal substrates to form a bonding layer between the substrates, and etching the first or / and second quartz crystal substrate toward the bonding layer to form a thin portion And a step of forming the laminated substrate.

  According to the above method, the linear defects of the first and second crystal substrates do not overlap, and the expansion of the etch channel can be stopped by the bonding layer even if the stacked substrates are etched. Therefore, a hole penetrating the first and second quartz substrates is not formed. Further, since the first and second quartz substrates are bonded in the form of a flat plate, distortion and breakage can be prevented by the stress at the time of bonding.

Application Example 2 The method for manufacturing a laminated substrate according to Application Example 1, wherein the first and second crystal substrates are bonded by direct bonding.
By the above method, the temperature characteristics are not deteriorated due to the difference in thermal expansion coefficient between the first and second quartz crystal substrates.

Application Example 3 The method for manufacturing a laminated substrate according to Application Example 1, wherein the bonding layer is made of low-melting glass.
According to the above method, since the low-melting glass having a thermal expansion coefficient substantially equal to that of the quartz crystal is used, the temperature characteristics are not deteriorated due to the difference in thermal expansion coefficient between the first and second quartz crystal substrates.

  Application Example 4 A step of bonding the first and second quartz crystal substrates to form a bonding layer between the substrates, a step of masking regions corresponding to the frame portion and the support portion of the first and second substrates, And a step of etching the first or / and second quartz substrate toward the bonding layer to form a flexible portion. A method of manufacturing a diaphragm, comprising:

  According to the above method, the linear defects of the first and second crystal substrates do not overlap, and the expansion of the etch channel can be stopped by the bonding layer even if the stacked substrates are etched. Therefore, a hole penetrating the first and second quartz substrates is not formed. Moreover, the flexible part of a diaphragm can be easily formed in a thin film, and detection sensitivity can be improved. Further, since the first and second quartz substrates are bonded in the form of a flat plate, distortion and breakage can be prevented by the stress at the time of bonding.

Application Example 5 The method for manufacturing a diaphragm according to Application Example 4, wherein the first and second crystal substrates are bonded by direct bonding.
By the above method, the temperature characteristics are not deteriorated due to the difference in thermal expansion coefficient between the first and second quartz crystal substrates. Therefore, the sensitivity of the diaphragm can be improved.

[Application Example 6] The diaphragm manufacturing method according to Application Example 4, wherein the bonding layer is made of low-melting glass.
By the above method, the temperature characteristics are not deteriorated due to the difference in thermal expansion coefficient between the first and second quartz crystal substrates. Therefore, the sensitivity of the diaphragm can be improved.

  [Application Example 7] Manufacture of a pressure sensor characterized in that it is formed by joining a support portion of a diaphragm manufactured by the manufacturing method according to any one of Application Examples 4 to 6 and a base portion of a pressure sensitive element. Method.

  According to the above method, the linear defects of the first and second crystal substrates do not overlap, and the expansion of the etch channel can be stopped by the bonding layer even if the stacked substrates are etched. Therefore, a hole penetrating the first and second quartz substrates is not formed. Further, the flexible portion of the diaphragm can be easily formed into a thin film, and a pressure sensor with improved detection sensitivity can be obtained.

It is explanatory drawing of the manufacturing method of the multilayer substrate of this invention. It is explanatory drawing of the modification of the manufacturing method of a laminated substrate. It is explanatory drawing of the manufacturing method of the quartz substrate by the chemical etching method. It is explanatory drawing about the relationship between the number of the linear defects per unit area, and the number of overlapping. (A) is the perspective view which looked at the inner side (recessed part side) of the board | substrate of a pressure sensor from the upper direction, (B) is the perspective view which looked at the inner side (support part side) of the diaphragm from the upper direction. It is sectional drawing of a pressure sensor. It is a bottom view of a diaphragm. It is explanatory drawing of the manufacturing method of the diaphragm of this invention. It is explanatory drawing of the prior art of a pressure sensor, (A) is sectional drawing of a pressure sensor, (B) is an AA arrow directional view of (A).

Embodiments of a method for manufacturing a laminated substrate, a method for manufacturing a diaphragm, and a method for manufacturing a pressure sensor according to the present invention will be described below in detail with reference to the accompanying drawings.
First, a mechanism for forming a through hole (etch channel) due to a linear defect when a quartz crystal substrate is etched will be described. FIG. 3 is an explanatory view of a method for manufacturing a quartz substrate by a chemical etching method. When a thin portion is formed on the flat plate-like quartz substrate 80 shown in FIG. 3A, it corresponds to a thick portion other than the thin portion on one main surface side 80a of the quartz substrate 80 as shown in FIG. A metal layer 81a is formed by metallizing the region to be formed with a Cr and Au film. Further, a metal layer 81b metallized with a Cr and Au film is formed on the entire other main surface 80b of the quartz substrate 80. Next, as shown in FIG. 3C, a region corresponding to the thin portion is etched using an etchant such as ammonium fluoride. At this time, as shown in FIG. 3 (2), when there is a linear defect 82 exposed on the surface of one main surface 80a of the quartz substrate 80, the chemical strength against the etchant is weak and etching is preferentially performed. A through hole (etch channel) 83 is formed by proceeding. When the metal film formed on both main surfaces 80a and 80b of the quartz substrate 80 as shown in FIG. 3 (3) is removed, the quartz substrate 80 has a through-hole penetrating from one principal surface 80a to the other principal surface 80b. 83 will be formed.

  Here, a quartz substrate with almost no linear defects can be manufactured by subjecting the quartz raw stones to growth conditions, or by subjecting the grown raw stones to a sweeping treatment or an annealing treatment and further selecting them. By using such a quartz substrate, a method of suppressing the through hole due to etching is also conceivable. However, there is a problem in that manufacturing such a quartz substrate is costly.

In view of this, the present invention proposes a processing method in which an etch channel is not generated by etching even for an inexpensive rough having linear defects.
FIG. 1 is an explanatory view of a method for producing a laminated substrate according to the present invention.

  First, a thin first substrate 100 as shown in FIG. 1A and a thick second substrate 200 are bonded (FIG. 1B). The first and second substrates 100 and 200 of the present invention use quartz substrates such as artificial quartz cut at an angle such as AT cut. As the bonding means, direct bonding, plasma activated bonding, siloxane bonding, or the like can be used.

  In the case of plasma activation, the bonding surface of the bonding member is subjected to surface treatment using plasma, and then the bonding member is bonded and bonded. According to such a joining technique, even when the heat treatment temperature is lowered as compared with direct joining, a high joining strength can be obtained.

  In the case of siloxane bonding, the bonding members are bonded to each other through a thin glassy material. Specifically, a bonding film 104 having a Si skeleton having a random atomic structure including a siloxane (Si—O) bond and a leaving group bonded to the Si skeleton is formed on the first substrate 100; The bonding members are bonded to each other through the bonding film 104. By applying energy such as heat and compression to the bonding film 104, the leaving group bonded to the Si skeleton is eliminated, and an active hand is generated in the Si skeleton. The bonding between the active hands generated in the bonding film 104 forms an Si—O—Si bond, and the two bonding films 104 formed on the bonding member are integrated to form a strong bonding layer 105.

  As shown in FIG. 1 (1), a plurality of linear defects 13 and 23 are present randomly on the first and second substrates 100 and 200. Here, the present inventor examined the probability that the linear defects overlap when bonding such substrates.

FIG. 4 is an explanatory diagram regarding the relationship between the number of linear defects per unit area and the number of overlaps. In the graph, the horizontal axis represents the number of linear defects per square centimeter, and the vertical axis represents the number of overlaps per square centimeter. The square mark represents the etch channel diameter of 3 to 5 μm, and the triangle mark represents the etch channel diameter of 2 to 4 μm. As shown in the figure, when the number of linear defects is 100 (pieces / cm ² ) or less, both the diameters of 2 to 4 μm and 3 to 5 μm indicate zero overlap. Therefore, it can be seen that when the substrates are joined together, the linear defects overlap and there is almost no possibility of a through-hole due to the etching process. Therefore, it is desirable to use a quartz substrate having a linear defect of 100 (pieces / cm ² ) or less.

  Next, as shown in FIG. 1 (3), a region not to be etched, that is, one main surface 100a of the first substrate 100 and a region corresponding to the thick portion of the second substrate 200 are formed by sputtering, vapor deposition, or the like. A Cr film and a metal layer 102 coated with an Au film on the Cr film are formed.

  Then, as shown in FIG. 1 (4), a process corresponding to the thin portion 205 of the laminated substrate 400 is etched to form the thick portion 204. At this time, since the bonding layer 105 is formed between the first and second substrates 100 and 200, the bonding layer is used even if the etching progresses preferentially with respect to the linear defect of the second substrate 200. 105 functions as an etching stop layer, and the expansion of the etch channel does not occur, and the through-hole penetrating the first and second substrates 100 and 200 is not formed. Further, since the linear defects 13 and 23 of the first and second substrates 100 and 200 are in positions that do not overlap each other at the time of bonding, the etching can be stopped on the opposing substrates even if etching progresses preferentially. Therefore, the expansion of the etch channel does not occur.

  Next, a process of removing the exposed metal layer 102 of the multilayer substrate 400 shown in FIG. 1 (4) with potassium iodide, nitric acid, or the like is performed. Thereby, the thin part 205 can be formed in the laminated substrate 400 (FIG. 1 (5)).

  According to the above method, the linear defects of the first and second substrates do not overlap, and the expansion of the etch channel can be stopped by the bonding layer even when the stacked substrates are etched. Further, there is no deterioration in temperature characteristics due to the difference in thermal expansion coefficient between the first and second substrates.

  FIG. 2 is an explanatory view of a modified example of the method for manufacturing a laminated substrate. As in the bonding method of the first and second substrates shown in FIG. 1, the bonding layer is a bonding method that does not cause deterioration of temperature characteristics due to the difference in thermal expansion coefficient between the first and second substrates. There is a method using a low-melting glass layer.

  As shown in FIG. 2 (1), first and second substrates 101, 201 having substantially the same thickness are prepared, and lead, bismuth, which becomes a bonding layer 105a on one main surface of the first substrate 101, A low-melting glass layer 106 made of silver, vanadium oxide or the like is formed by screen printing or the like. The bonding layer may be any material that has the same thermal expansion coefficient as that of the quartz substrate such as the first and second substrates 101 and 201 and can be firmly fixed without transmitting stress after bonding.

  As shown in FIG. 2B, the first and second substrates 101 and 201 are heated and melted and bonded to form a bonded substrate 401. The bonding substrate 401 has a configuration in which a low-melting glass layer 106 serving as the bonding layer 105 a is sandwiched between the first and second substrates 101 and 201.

  As shown in FIG. 2 (3), a Cr film and a metal layer 102 coated with an Au film on a Cr film and a Cr film coated on a region corresponding to the thick part on the second substrate 201 by sputtering or vapor deposition are formed. Form. The metal layer 102 is formed by forming a metal layer entirely on one main surface of the second substrate 201 and then removing the metal layer by masking with a resist film, or by previously masking the metal layer other than the formation position. It may be a method of forming.

  As shown in FIG. 2 (4), a process for etching a region to be the thin portion 205 of the multilayer substrate 401 is performed to form the thick portion 204. At this time, since the bonding layer 105a is formed between the first and second substrates 101 and 201, etching progresses preferentially with respect to the linear defects of the first or second substrate 101 and 201. Even in this case, the bonding layer 105a functions as an etching stop layer, and the expansion of the etch channel does not occur, and the through hole penetrating the first and second substrates 101 and 201 is not formed. Further, since the linear defects 13 and 23 of the first and second substrates 101 and 201 are in positions that do not overlap each other at the time of bonding, the etching can be stopped on the opposing substrates even if the etching progresses preferentially. Therefore, the expansion of the etch channel does not occur.

  Next, a process of removing the metal layer 102 from the exposed metal layer 102 of the multilayer substrate 401 as shown in FIG. 2D with potassium iodide, nitric acid, or the like is performed. Thereby, the thin part 205 can be formed in the laminated substrate 401 (FIG. 2 (5)).

  According to the method of the above-described modification, the linear defects of the first and second substrates do not overlap, and the expansion of the etch channel can be stopped by the bonding layer even when the stacked substrates are etched. Further, there is no deterioration in temperature characteristics due to the difference in thermal expansion coefficient between the first and second substrates.

  Note that the low-melting glass layer shown in FIG. 2 can also be applied to the bonding layer of the first and second substrates 100 and 200 shown in FIG. Further, direct bonding, plasma activated bonding, siloxane bonding, or the like shown in FIG. 1 can be applied to the bonding method of the first and second substrates 101 and 201 shown in FIG.

Next, the manufacturing method of the diaphragm and the manufacturing method of the pressure sensor of the present invention will be described below.
FIG. 5 is an exploded perspective view of the pressure sensor of the present invention. (A) is the perspective view which looked at the inner side (recess side) of the board | substrate from the upper direction, (B) is the perspective view which looked at the inner side (support part side) of the diaphragm from the upper direction. FIG. 6 is a cross-sectional view of the pressure sensor. FIG. 7 is a bottom view of the diaphragm. As shown in the figure, the pressure sensor 10 of the present invention includes a substrate 20, a vibrator 30 with a frame, and a diaphragm (pressure receiving means) 40.

  The substrate 20, the framed vibrator 30, and the diaphragm (pressure receiving means) 40 of this embodiment use a quartz substrate made of a homogeneous material in consideration of deterioration of temperature characteristics due to a difference in thermal expansion coefficient.

  The substrate 20 is a member that serves as a package or lid for sealing the internal space S that houses the piezoelectric vibrating piece 31 of the framed vibrator 30. As shown in FIG. 5 or FIG. 6, the substrate 20 has a recess 22 formed on the inner side thereof, and an end surface 24 serving as an annular surrounding portion on the peripheral side on the opening side of the recess 22 has a frame of the framed vibrator 30. By stacking and joining the shape portion 32 and the frame portion 42 of the diaphragm 40 in order, the inner space S in which the inside of the recess 22 is sealed is formed.

  The main surface outline of the substrate 20 shown in FIG. 5 is a substantially square shape composed of two sides extending in parallel with the X-axis direction of the crystal crystal axis and two sides extending in parallel with the Y-direction of the crystal crystal axis. The shape (ie, substantially rectangular).

  Although not shown, an electrode terminal is provided on the surface exposed to the outside of the substrate 20, and this electrode terminal inputs / outputs a signal to / from the piezoelectric vibrating piece 31 via a conductive pattern (not shown). To do.

  The framed vibrator 30 constituting the pressure sensitive element includes a frame-shaped portion 32 and a double tuning fork type piezoelectric vibrating piece 31 connected to the frame-shaped portion 32. The vibrator 30 with a frame is formed by etching, for example, quartz as a piezoelectric material. The outer shape of the frame-shaped portion 32 shown in FIG. 5 is a substantially rectangular shape including two sides extending in parallel with the X-axis direction and two sides extending in the Y-axis direction.

  In the case of this embodiment, the piezoelectric vibrating piece 31 uses a double tuning fork vibrating piece that has a large frequency change with respect to an applied force and can detect pressure with high sensitivity. That is, the double tuning fork vibrating piece is a vibrating piece having a bending vibration mode, and has a structure in which the end faces on the free end sides of two tuning fork type vibrating pieces are opposed to each other as shown in FIG. Two vibrating arms 34 and 35 extending in the longitudinal direction in the Y-axis direction in parallel to each other, and two bases connected to both ends in the longitudinal direction of the vibrating arms 34 and 35 and aligned with the vibrating arms 34 and 35 36. The vibrating arms 34 and 35 extend from one base portion 36 toward the other base portion 36. When a tensile stress (extension stress) or a compressive stress is applied to the two vibrating arms 34 and 35, which are pressure-sensitive portions (vibrating arms 34 and 35) of the double tuning fork vibrator, the resonance frequency is applied. It has a characteristic that it changes almost in proportion to the stress.

  The vibrating arms 34 and 35 are elongated in the Y-axis direction, and are portions that are flexibly oscillated by applying a driving voltage by an excitation electrode 39a provided on the surface thereof, and are extended and / or compressed in this direction in the Y-axis direction. This is the part where the frequency changes when stress or tension is applied. Therefore, a pressure change can be detected by detecting the frequency change.

  The piezoelectric vibrating piece 31 sets the detection direction of force as a detection axis, and the direction in which the pair of base portions 36 of the piezoelectric vibrating piece 31 are arranged is parallel to the detection axis. In the case of a double tuning fork type piezoelectric vibrator, the beam extending direction and the detection axis are in parallel relation.

  The base portion 36 is both end portions for fixing the piezoelectric vibrating piece 31 to the diaphragm 40. Further, in the case of this embodiment, the base portion 36 is a relay for inputting and outputting signals between the vibrating arms 34 and 35 and the outside. It is also a portion having the electrode 39b.

  The surface of the diaphragm 40, which will be described later, on the support portion 45 side has an extraction electrode 39c that is electrically connected to the above-described relay electrode 39b. The extraction electrode 39c is described above via the input / output electrode 39d. It is electrically connected to terminals provided on the substrate 20.

  The frame portion 32 is a member that forms an internal space S that accommodates the piezoelectric vibrating reed 31 together with the concave portion of the substrate 20, and is a member that is stacked and fixed on the frame portion 42 of the diaphragm 40. Specifically, the frame-shaped portion 32 has a space between at least the vibrating arms 34 and 35, and is connected to the base portions 36 at both ends of the piezoelectric vibrating piece 31 via the connecting portions 38, and the piezoelectric vibration. It is formed integrally with the piece 31 and the connecting portion 38. That is, in the case of this embodiment, the frame-shaped part 32, the connection part 38, and the piezoelectric vibrating piece 31 are formed from one crystal wafer using, for example, a photolithography technique and an etching technique.

  The connecting portion (beam) 38 is thinner than the base portion 36. That is, it is preferable that the connecting portion 38 does not exist after the base portion 36 and the support portion 45 of the diaphragm 40 are joined, because the connecting portion 38 hinders the flexure of the vibrating arms 34 and 35. When the child 30 and the diaphragm 40 are joined, the base portion 36 and the support portion 45 are formed so thin that they can be aligned and joined.

  And the connection part 38 is between the direction (Y-axis direction) which a pair of base part 36 connects, ie, the part which consists of the connection part 38 and the base part 36, and the frame edge extended in the X-axis direction of the frame-shaped part 32. A through hole 38a penetrating in the thickness direction is provided. By thus configuring the connecting portion 38 to be thin and providing the through hole 38a, when the pressure P to be measured is received by the pressure receiving surface 43 of the diaphragm 40 as shown in FIG. The vibrating arms 34 and 35 of the vibrating piece 31 can be easily expanded and contracted in the direction in which the pair of base portions 36 are arranged (Y-axis direction), and the situation where the connecting portion 38 hinders the expansion and contraction in the Y-axis direction can be prevented. it can.

  The connecting portions 38 are formed so as to extend away from each other along the width direction from both ends in the width direction of each base portion 36 (that is, the X-axis direction orthogonal to the Y-axis direction connecting the base portions in the drawing). It is a beam. This beam intersects the frame in the Y-axis direction so as not to hinder the deflection in the Y-axis direction (FIG. 5 shows a connecting portion 38 that is orthogonal).

  With such a beam configuration, the configuration (rigidity) of the framed vibrator 30 is symmetric with respect to the center line along the Y-axis direction. With such a symmetric configuration, the amount of bending of the piezoelectric vibrator becomes equal to the left and right with respect to the center line along the Y-axis direction, so that the force transmitted from the diaphragm 40 to the piezoelectric vibrating piece 31 is reduced to two. The vibration arms 34 and 35 can be equally distributed.

Further, in order to reduce vibration leakage, the connecting portion 38 is preferably formed at a position as far away from the vibrating arms 34 and 35 as possible, and as shown in FIG. Are connected to both ends in the width direction of the portion.
Excitation electrodes 39a formed on the vibrating arms 34 and 35 of the piezoelectric vibrator are electrically connected to terminal electrodes formed on the outer frame via lead electrodes 39c formed on connection portions (beams).

The diaphragm 40 is a member that partitions the outside and the internal space S and transmits the pressure P received from the outside to the piezoelectric vibrating piece 31. The diaphragm 40 has a thin film-like flexible part 41 and a frame part 42 surrounding the flexible part 41 so that a fine pressure P can be transmitted. The diaphragm 40 has a support portion 45 on the main surface (the other main surface) 44 on the side opposite to the pressure receiving surface 43 of the flexible portion 41.
The frame portion 42 is formed to be thicker than the thin flexible portion 41, and the frame-like portion 32 of the above-described framed vibrator 30 and the substrate 20 are sequentially laminated and bonded.

The diaphragm 40 is configured such that the frame portion 42 is fixedly bonded to the end surface 24 on the opening side of the substrate 20 via the frame-shaped portion 32 of the vibrator 30 with the frame, so that the thermal expansion of the frame-shaped portion 32 is performed. It is made of a material having a thermal expansion coefficient similar to that of the coefficient.
Here, in the diaphragm 40 of the present invention, as shown in FIG. 7, the position where the displacement amount is the largest in the flexible portion 41 is the center C of the main surface 44 on the sealed side.

  A pair of support portions 45a and 45b is formed on the main surface 44 on the sealed side of the flexible portion 41 that serves as a pressure receiving surface so as to sandwich the center C of the main surface 44 on the sealed side. The support portions 45 a and 45 b serve as a pedestal for joining the base portion 36 of the piezoelectric vibrating piece 31. By placing the piezoelectric vibrating reed 31 supported and fixed by the supporting portions 45a and 45b so as to straddle the center C of the main surface 44 on the sealed side, the greatest stress acts on the vibrating arms 34 and 35 as pressure-sensitive portions. The detection sensitivity of pressure fluctuation can be improved.

A method for manufacturing the diaphragm having the above configuration will be described below. FIG. 8 is an explanatory diagram of the diaphragm manufacturing method of the present invention.
First, the thin film first substrate 103 constituting the diaphragm as shown in FIG. 8A and the thick second substrate 203 are bonded (FIG. 8B). As the bonding means, direct bonding, plasma activated bonding, siloxane bonding, or the like can be used.

As shown in FIG. 8A, the first and second substrates 103 and 203 have a plurality of linear defects 13 and 23 at random, but the etch channel is 100 (pieces / cm ² ) or less. When a quartz substrate is used, the number of overlapping linear defects becomes 0, and when the substrates are joined together, the linear defects overlap and there is almost no possibility of forming a through hole due to the etching process.

  Next, as shown in FIG. 8 (3), sputtering or vapor deposition is performed in a region that is not etched, that is, one main surface 100 a of the first substrate 103 and a region corresponding to the frame portion and the support portion of the second substrate 200. Then, a Cr film and a metal layer 102 coated with an Au film on the Cr film are formed.

  Then, as shown in FIG. 8 (4), the frame portion 42 and the support portion 45 are formed by performing a process of etching a region corresponding to the flexible portion 41 that is a thin portion of the multilayer substrate 403. At this time, since the bonding layer 105 is formed between the first and second substrates 103 and 203, the bonding layer can be used even if etching progresses preferentially to the linear defects of the second substrate 203. 105 functions as an etching stop layer, and the expansion of the etch channel does not occur, and a through-hole penetrating the first and second substrates 103 and 203 is not formed. Further, since the linear defects 13 and 23 of the first and second substrates 103 and 203 are in positions that do not overlap each other at the time of bonding, the etching can be stopped on the opposing substrates even if the etching proceeds preferentially. Therefore, the expansion of the etch channel does not occur.

  Next, a process of removing the exposed metal layer 102 of the multilayer substrate 403 shown in FIG. 8D with potassium iodide, nitric acid, or the like is performed. Thereby, the thin flexible part 41 can be formed in the diaphragm 40 (FIG. 8 (5)).

  According to the above method, the linear defects of the first and second substrates do not overlap, and the expansion of the etch channel can be stopped by the bonding layer even when the stacked substrates are etched. Further, there is no deterioration in temperature characteristics due to the difference in thermal expansion coefficient between the first and second substrates.

  Next, in the manufacturing method of the pressure sensor 10 having the above-described configuration, the support portion 45 of the diaphragm 40 and the base portion 36 of the framed vibrator 30 serving as a pressure-sensitive element are bonded with a bonding member such as an adhesive. Further, the frame-like portion 32 of the vibrator 30 with the frame is sandwiched between the substrate 20 and the diaphragm 40 and joined by a joining member such as an adhesive to form a three-layer structure. Specifically, the pressure sensor 10 is a material of a diaphragm 40, a vibrator 30 with a frame, and a substrate 20 matched to the cut angle of a piezoelectric vibrating piece, for example, a Z-plate quartz crystal cut perpendicularly to the Z axis. A material having substantially the same thermal expansion coefficient α is used. As shown in FIG. 6, an inorganic adhesive is used as an adhesive member 60 between the diaphragm 40 and the framed vibrator 30 and between the framed vibrator 30 and the substrate 20. As a result, a predetermined hardness is obtained after curing, so that the CI value is good. In addition, the stress at the bonded portion is less relaxed and the deterioration over time is small. Alternatively, an adhesive having a thermal expansion coefficient α combined with a material such as a diaphragm may be used as the adhesive member 60. Thereby, temperature characteristics can be improved.

  According to such a pressure sensor manufacturing method of the present invention, the linear defects of the first and second substrates do not overlap, and the expansion of the etch channel is stopped by the bonding layer even when the stacked substrates are etched. be able to. Therefore, a hole penetrating the first and second substrates is not formed. Further, the flexible portion of the diaphragm can be easily formed into a thin film, and a pressure sensor with improved detection sensitivity can be obtained.

DESCRIPTION OF SYMBOLS 1 ......... Pressure sensor, 2 ......... Diaphragm, 3 ......... Support part, 4 ......... Double tuning fork vibrator, 5 ......... Vibrating arm, 10 ...... Pressure sensor, 13 ......... Linear defect 20 ......... Substrate, 22 ......... Recess, 23 ......... Linear defect, 24 ......... End face, 30 ......... Framed vibrator, 31 ......... Piezoelectric vibrating piece, 32 ......... Frame shape 34, 35 ......... vibrating arm, 36 ......... base, 38 ......... connecting part, 40 ......... diaphragm, 41 ......... flexible part, 42 ......... frame, 43 ......... pressure receiving , 44... Main surface on the sealed side, 45... Support, 60... Adhesive member, 80... Quartz substrate, 82 ... Linear defects, 83. 101, 103 ......... First substrate, 102 ......... Metal layer, 105 ......... Joint layer, 106 ......... Low melting point glass layer, 200, 201, 203 ......... No. Substrate, 204 ......... thick portion, 205 ......... thin portion, 400 and 401 ......... laminated substrate.

Claims (7)

Bonding the first and second quartz substrates and forming a bonding layer between the substrates;
Etching the first or / and second quartz substrate toward the bonding layer to form a thin portion;
A method for producing a laminated substrate comprising:   The method for manufacturing a laminated substrate according to claim 1, wherein the first and second crystal substrates are bonded by direct bonding.   The method for manufacturing a laminated substrate according to claim 1, wherein the bonding layer is made of low-melting glass. Bonding the first and second quartz substrates and forming a bonding layer between the substrates;
Masking areas corresponding to the frame and support portions of the first and second substrates;
Etching the first or / and second quartz substrate toward the bonding layer to form a flexible portion;
A process for producing a diaphragm, comprising:   The diaphragm manufacturing method according to claim 4, wherein the first and second quartz substrates are joined by direct joining.   The diaphragm manufacturing method according to claim 4, wherein the bonding layer is made of low-melting glass.   A method for manufacturing a pressure sensor, comprising: a diaphragm supporting portion manufactured by the manufacturing method according to any one of claims 4 to 6; and a base portion of a pressure sensitive element.

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