JP4600140B2 - Method for manufacturing piezoelectric vibrating piece - Google Patents

Description

  The present invention relates to a method of manufacturing a piezoelectric vibrating piece and a piezoelectric vibrator, and more particularly, a method of manufacturing a piezoelectric vibrating piece including a vibrating portion and a frame portion, and having a through groove formed between the vibrating portion and the frame portion. The present invention also relates to a piezoelectric vibrator on which a piezoelectric vibrating piece manufactured by the manufacturing method of the present invention is mounted.

A piezoelectric vibrating piece in which a frame portion is provided around the vibrating portion and a through groove is formed between the vibrating portion and the frame portion is usually manufactured by chemical etching (see FIG. 4). When the piezoelectric vibrating piece is manufactured by chemical etching, first, a metal film that forms the corrosion-resistant film 2 when the crystal is chemically etched is formed on the surface of the piezoelectric substrate 1, and a photoresist is applied thereon. Thereafter, exposure and development are performed so as to obtain the shape of the vibration part and the frame part, and the metal film of the part from which the resist is removed is chemically etched to obtain a desired shape of corrosion resistant film (first corrosion resistant film) (S1). ). Then, the crystal portion where the first corrosion-resistant film 2 is not formed is chemically etched to form a groove 3 between the vibrating portion 6 and the frame portion 5, and finally to form a through groove 4 (S2 to S5). . Next, the first corrosion-resistant film is removed (S6), and the second corrosion-resistant film 7 is formed on the front and back surfaces of the piezoelectric substrate 1 to be the frame portion 5 in the same manner as the photolithography process described above (S7). Then, the front and back surfaces of the piezoelectric substrate 1 to be the vibrating portion 6 are chemically etched to form a predetermined thickness (S8). Thereafter, the second corrosion-resistant film 7 is removed (S9), and the excitation electrode 8 is formed on the front and back surfaces of the vibration part 6 to form the piezoelectric vibrating piece 9 (S10).
As what was disclosed about manufacturing a piezoelectric vibrating piece by an etching, patent document 1 can be mentioned, for example.
Japanese Patent Laid-Open No. 7-212171

  Various piezoelectric materials including quartz are used for the piezoelectric vibrator, and for example, an AT-cut piezoelectric substrate or the like is used as the substrate. This AT-cut piezoelectric substrate is cut with one side parallel to the X axis (electrical axis) and the other side inclined about 35 degrees around the X axis from the Z axis (optical axis). By the way, when the crystal is chemically etched, the etching rate varies depending on the crystal direction. That is, when the quartz is chemically etched, there is a characteristic of anisotropic etching. Therefore, as shown in FIG. 5, when the AT-cut piezoelectric substrate 1 cut out from the crystal is chemically etched, the groove 2 formed by the etching has a large inclination on one side.

  Therefore, when manufacturing a piezoelectric vibrating piece with a frame by the manufacturing process as described above, the following problems occur. First, since the width of the through groove has to be increased, the planar size of the vibration part must be reduced. Specifically, when the width of the through groove is narrowed, the groove formed from the front surface side and the back surface side of the piezoelectric substrate is displaced in the horizontal direction, and the groove may not penetrate. Therefore, the thicker the piezoelectric substrate, the wider the width of the through groove, so that the groove communicates. However, when there is a restriction on the size of the package on which the piezoelectric vibrating piece is mounted, if the width of the through groove is increased, the plane size of the vibrating portion must be reduced as a price. However, when the planar size of the vibration part is reduced, there arises a problem that the crystal impedance (CI) value increases.

  Secondly, in order to join the lid to the frame portion, the width of the frame portion must be widened, so the planar size of the vibrating portion must be reduced. Specifically, since the through-groove is formed obliquely in the piezoelectric substrate, the frame portion is formed so that the width on the front surface side is different from the width on the back surface side. However, in order to obtain a piezoelectric vibrator of a chip size package (CSP), the lid must be joined to the frame, so that the front and back surfaces of the frame have a width that allows the lid to be joined on each surface. Must have. That is, the frame portion must be widened in order to join the lid. Therefore, when there is a restriction on the package size for mounting the piezoelectric vibrating piece, the planar size of the vibrating part must be reduced by increasing the width of the frame part. However, when the planar size of the vibration part is reduced, there arises a problem that the crystal impedance (CI) value increases.

  Third, since the piezoelectric vibrating piece is formed by being immersed in an etching solution, the frequency temperature characteristics of the piezoelectric vibrating piece are deteriorated. Specifically, since the vibration part has a finite size, spurious vibrations exist in addition to the main vibration. For example, if the vibration part is an AT-cut quartz plate, spurious vibrations exist in the vicinity of the frequency of the main vibration in addition to the vibration whose thickness vibration is the main vibration. For this reason, the processing accuracy of the outer dimensions of the vibrating part is determined so that the main vibration and the spurious vibration are not coupled. However, if the piezoelectric substrate is immersed in an etching solution for a long time in order to form the through groove, an error occurs in the external dimensions due to side etching. As a location where side etching is likely to occur, a location corresponding to a corner portion formed in the direction along the X axis, particularly in the + X direction can be exemplified. As described above, when the processing accuracy of the vibrating portion is deteriorated by side etching, there is a problem that the frequency temperature characteristic of the piezoelectric vibrating piece is deteriorated.

The present invention has been made in order to solve the above-described problems. The width of the through groove formed between the vibrating portion and the frame portion is reduced, and the influence of side etching generated during chemical etching is reduced. Another object of the present invention is to provide a method of manufacturing a piezoelectric vibrating piece that can improve the processing accuracy of the vibrating portion.
Another object of the present invention is to obtain a piezoelectric vibrator from a piezoelectric vibrating piece manufactured using the above method.

The angle of the inclined surface generated when the piezoelectric substrate is chemically etched is a substantially constant numerical value depending on the cut angle of the piezoelectric substrate to be used. Therefore, in order to reduce the width of the through groove between the vibrating portion and the frame portion, the thickness of the piezoelectric substrate in the portion constituting the through groove may be reduced.
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.
A method of manufacturing a piezoelectric vibrating piece according to a first aspect is a method of manufacturing a piezoelectric vibrating piece including a vibrating portion and a frame portion surrounding the vibrating portion, and providing a through groove between the vibrating portion and the frame portion. Then, the thickness of the piezoelectric substrate corresponding to the part constituting the vibrating portion and the through groove is adjusted to a predetermined thickness by chemical etching, and the chemical etching is performed again on the piezoelectric substrate whose thickness is adjusted. A method of manufacturing a piezoelectric vibrating piece, characterized in that a through groove is formed. According to such a method, since the thickness of the piezoelectric substrate is adjusted before the through groove is formed, the thickness of the portion where the through groove is formed can be reduced. Since the through groove is formed in the piezoelectric substrate having a reduced thickness, the width necessary for forming the through groove can be reduced. Further, since the through groove is formed after adjusting the thickness of the piezoelectric substrate, the time during which the end portion of the portion that becomes the vibration portion is exposed to the etching solution is shortened. For this reason, the side etching which arises in the edge part (side surface) of a vibration part decreases, and it becomes possible to improve the processing precision of a vibration part.
A method of manufacturing a piezoelectric vibrating piece according to a second aspect is a method of manufacturing a piezoelectric vibrating piece including a vibrating portion and a frame portion surrounding the vibrating portion, and providing a through groove between the vibrating portion and the frame portion. And forming a first corrosion-resistant film corresponding to the shape of the frame portion on the piezoelectric substrate, and chemically etching a portion constituting the vibrating portion and the through groove to have a thickness corresponding to the oscillation frequency. And a step of forming a second corrosion-resistant film on a portion of the piezoelectric substrate other than the portion constituting the through groove and forming the through groove by chemical etching. Manufacturing method. Even in such a method, the thickness of the piezoelectric substrate in the portion where the through groove is formed can be reduced in advance. Since the through groove is formed in the piezoelectric substrate having a reduced thickness, the width necessary for forming the through groove can be reduced. Further, since the through groove is formed after adjusting the thickness of the piezoelectric substrate, the time during which the end portion of the portion that becomes the vibration portion is exposed to the etching solution is shortened. For this reason, the side etching which arises in the edge part (side surface) of a vibration part decreases, and it becomes possible to improve the processing precision of a vibration part.
The method for manufacturing a piezoelectric vibrating piece according to the second embodiment is characterized in that an electrode pattern of the piezoelectric vibrating piece is formed using the second corrosion-resistant film. .
A piezoelectric vibrator as a fourth embodiment is a piezoelectric vibrator in which the piezoelectric vibrating piece manufactured by using the method according to any one of the first to third embodiments is sandwiched between lids, The piezoelectric vibrating piece includes a vibrating portion and a frame portion surrounding the vibrating portion, a protrusion having a one-side inclined surface on the frame portion of the piezoelectric vibrating piece, and an extraction electrode formed on the inclined surface, A piezoelectric vibrator characterized in that an actually measured through groove width is narrower than a through groove width calculated from a thickness of a frame portion and an inclination angle of the one-side inclined surface. The piezoelectric vibrator having such a configuration can be formed into a chip size package because the lid is directly joined to the frame portion of the piezoelectric vibrating piece and this is used as the piezoelectric vibrator. And since the thickness of a vibration part is made thinner than the thickness of a frame part, a plane-shaped lid can be used. Therefore, the piezoelectric vibrator can be reduced in size and thickness, and the number of components is reduced, leading to a reduction in manufacturing cost. In addition, since the piezoelectric vibrator has a through groove formed in the piezoelectric vibrating piece, stress applied to the piezoelectric vibrator is not propagated to the vibrating portion, and a constant oscillation frequency can be output. Further, by forming the electrode on the inclined surface, disconnection of the extraction electrode can be prevented.
In addition, as an application example for achieving the above object, a method of manufacturing a piezoelectric vibrating piece including a vibrating part and a frame part surrounding the vibrating part, and providing a through groove between the vibrating part and the frame part In this case, the thickness of the piezoelectric substrate corresponding to the portion constituting the vibration part and the through groove is adjusted to a predetermined thickness by chemical etching, and the chemical etching is performed again on the piezoelectric substrate whose thickness is adjusted. To form a through groove.

  According to such a method, since the thickness of the piezoelectric substrate is adjusted before the through groove is formed, the thickness of the portion where the through groove is formed can be reduced. Since the through groove is formed in the piezoelectric substrate having a reduced thickness, the width necessary for forming the through groove can be reduced. Further, since the through groove is formed after adjusting the thickness of the piezoelectric substrate, the time during which the end portion of the portion that becomes the vibration portion is exposed to the etching solution is shortened. For this reason, the side etching which arises in the edge part (side surface) of a vibration part decreases, and it becomes possible to improve the processing precision of a vibration part.

  More specifically, it is a method of manufacturing a piezoelectric vibrating piece comprising a vibrating part and a frame part surrounding the vibrating part, and providing a through groove between the vibrating part and the frame part. Forming a first corrosion-resistant film in accordance with the shape of the frame portion, chemically etching a portion constituting the vibrating portion and the through groove to obtain a thickness corresponding to the oscillation frequency, A step of forming a second corrosion-resistant film in a portion other than the portion constituting the through groove and forming the through groove by chemical etching.

  Even in such a method, the thickness of the piezoelectric substrate in the portion where the through groove is formed can be reduced in advance. Since the through groove is formed in the piezoelectric substrate having a reduced thickness, the width necessary for forming the through groove can be reduced. Further, since the through groove is formed after adjusting the thickness of the piezoelectric substrate, the time during which the end portion of the portion that becomes the vibration portion is exposed to the etching solution is shortened. For this reason, the side etching which arises in the edge part (side surface) of a vibration part decreases, and it becomes possible to improve the processing precision of a vibration part.

  Further, when the piezoelectric vibrating piece is manufactured by the method as described above, the electrode of the piezoelectric vibrating piece is preferably formed by the second corrosion-resistant film. By doing so, the step of removing the second corrosion-resistant film and the step of forming the electrode pattern on the piezoelectric substrate can be omitted. For this reason, it becomes possible to improve productivity.

  The piezoelectric vibrator of the present invention is characterized in that the piezoelectric vibrating piece manufactured by the above method is sandwiched between lids. The piezoelectric vibrator having such a configuration can be formed into a chip size package because the lid is directly joined to the frame portion of the piezoelectric vibrating piece and this is used as the piezoelectric vibrator. And since the thickness of a vibration part is made thinner than the thickness of a frame part, a plane-shaped lid can be used. Therefore, the piezoelectric vibrator can be reduced in size and thickness, and the number of components is reduced, leading to a reduction in manufacturing cost. In addition, since the piezoelectric vibrator has a through groove formed in the piezoelectric vibrating piece, stress applied to the piezoelectric vibrator is not propagated to the vibrating portion, and a constant oscillation frequency can be output.

  Hereinafter, embodiments of a method for manufacturing a piezoelectric vibrating piece and a piezoelectric vibrator according to the present invention will be described. FIG. 1 is an explanatory view of a piezoelectric vibrating piece, FIG. 1 (A) is a schematic plan view, FIG. 1 (B) is a schematic cross-sectional view taken along line AA in FIG. 1 (A), and FIG. The schematic sectional drawing in the BB line of figure (A) is shown, respectively.

  The piezoelectric vibrating piece 10 has a vibrating portion 14 that serves as an excitation portion. A support portion 24 protrudes from the center portion of the opposing side surface of the vibration portion 14, and the tip of the support portion 24 is connected to the inner surface of the frame portion 16 surrounding the vibration portion 14. That is, the piezoelectric vibrating piece 10 has a shape in which the vibrating portion 14 and the frame portion 16 are formed in the XZ plane shown in FIG. 1A, and the through groove 26 is provided between the vibrating portion 14 and the frame portion 16. . The vibrating portion 14 is set to a predetermined thickness, specifically, a thickness determined according to the oscillation frequency, and excitation electrodes 18 are formed on the front and back surfaces thereof. Further, the piezoelectric substrate 12 constituting the frame portion 16 is formed thicker than the piezoelectric substrate 12 constituting the vibration portion 14. Furthermore, a lead electrode 22 and a connection electrode 20 that are electrically connected to the excitation electrode 18 formed on the vibrating portion 14 are formed on the frame portion 16.

  Next, a method for manufacturing the piezoelectric vibrating piece 10 will be described. FIG. 2 is a diagram illustrating a manufacturing process of the piezoelectric vibrating piece 10. First, on the surface of the piezoelectric substrate (piezoelectric wafer) 12, the first corrosion-resistant film 30 is formed at a site that becomes the frame portion 16. As the corrosion resistant film in this step, it is preferable to employ a thin film of metal, metal oxide or the like. As an example of a method for forming a corrosion-resistant film (film formation), a film formation method by the following steps can be given. First, the surface of the piezoelectric substrate 12 is mirror-polished. Next, a corrosion resistant film material is formed on the front and back surfaces (entire surface) of the piezoelectric substrate 12 by vacuum deposition, sputtering, or the like. Next, a photoresist is coated on the top surface of the corrosion-resistant film material. The photoresist coating may be performed by spin coating, roll coating, dip coating, or the like. Next, baking is performed to remove the solvent in the resist. Next, it exposes using the photomask according to the shape (pattern) of the corrosion-resistant film | membrane to form. Thereafter, development is performed, baking for removing solvent water and the like is performed, and the corrosion-resistant film is etched into a desired shape with an etching solution. After the etching is completed, the photoresist can be removed to obtain a corrosion-resistant film having a desired shape (S100).

  After the first corrosion-resistant film 30 is formed on the portion to be the frame portion 16 as described above, the front and back surfaces of the piezoelectric substrate 12 are chemically etched and etched until the piezoelectric substrate 12 has a predetermined thickness. The thickness of the piezoelectric substrate 12 is set according to the oscillation frequency required for the piezoelectric vibrating piece 10. The thicker the thickness, the lower the oscillation frequency, and the thinner, the higher the oscillation frequency. In order to make the piezoelectric substrate 12 have a predetermined thickness, an etching rate of the piezoelectric substrate 12 is obtained in advance, and etching is performed based on this etching rate (S110).

After etching the piezoelectric substrate 12 leaving the frame portion 16, the corrosion-resistant film 30 formed on the frame portion 16 is removed (S120).
Thereafter, the second corrosion-resistant film 40 is formed on the parts constituting the frame part 16 and the vibration part 14 (S130). Then, a portion of the piezoelectric substrate 12 where the second corrosion-resistant film 40 is not formed is chemically etched to form the vibrating portion 14 in the piezoelectric substrate 12. By this etching, a through groove 26 that separates the vibrating portion 14 and the frame portion 16 and the vibrating portion 14 and the frame portion 16 is formed in the piezoelectric substrate 12. In consideration of the etching rate, it is preferable to leave the protruding portion 25 having a one-side inclined surface on the frame portion 16. By setting it as such a shape, it becomes possible to form an electrode pattern using the inclined surface of the projection part 25. FIG. By forming the electrode on the inclined surface, disconnection of the extraction electrode can be prevented (S140).

  After the piezoelectric substrate 12 is formed in a desired shape, the second corrosion-resistant film 40 is removed (S150), and the excitation electrode 18, the extraction electrode 22, the connection electrode 20 (see FIG. 1) and the like are formed on the front and back surfaces of the piezoelectric substrate 12. An electrode pattern is formed (S160).

When the piezoelectric vibrating piece 10 is manufactured by the above-described process, the width of the through groove 26 formed between the vibrating portion 14 and the frame portion 16 is smaller than that of the piezoelectric vibrating piece manufactured by the conventional manufacturing method. Can be narrowed. This is due to the fact that the thickness of the piezoelectric substrate 12 on which the through-groove is formed is relatively reduced by etching. That is, the width L is required as the groove width for penetrating the piezoelectric substrate 12 having the thickness H. On the other hand, as shown in S100, by first adjusting the thickness of the vibrating portion 14 including the through groove 26, the thickness of the piezoelectric substrate 12 that forms the through groove 26 is simulated to a thickness h. It is possible to make it thinner. By doing so, it is possible to suppress the width L of the through groove 26 that required the width L. Therefore, the surface size (width) of the vibration part 14 can be formed larger than the conventional one by the amount corresponding to Equation 1. Therefore, the CI value of the piezoelectric vibrating piece 10 can be reduced.

  In addition, when the piezoelectric vibrating piece 10 is formed by the method as described above, when the through groove 26 is formed, the time during which the vibrating portion 14 is exposed to the etching solution is shortened. For this reason, the side etching with respect to the vibration part 14 decreases, and the processing accuracy of the vibration part 14 improves. Therefore, the frequency temperature characteristic of the piezoelectric vibrating piece 10 can be improved.

  In the method for manufacturing the piezoelectric vibrating piece described above, the second corrosion-resistant film 40 is removed after the step S140, and then the electrode pattern is formed. However, the second corrosion-resistant film 40 is formed in a place other than the part that becomes the through groove 26, and the second corrosion-resistant film 40 is used as an electrode pattern as it is, or an electrode pattern using the second corrosion-resistant film 40 is used. May be formed. By adopting such a technique, steps such as removal of the corrosion-resistant film and formation of the electrode pattern can be omitted, and productivity can be improved.

  In addition, the above-described method for manufacturing a piezoelectric vibrating piece has been described by taking a quartz substrate as an example of a piezoelectric material and an AT-cut piezoelectric substrate as an example. However, the method for manufacturing the piezoelectric vibrating piece described above can be applied even when another piezoelectric material such as lead zirconate titanate is used. It is also considered effective for other cut piezoelectric substrates such as BT cut.

  Further, the piezoelectric vibrating piece manufactured by the manufacturing method of the present invention is specified from the thickness H of the frame portion 16 in the piezoelectric vibrating piece 10, the inclination angle θ of the inclined surface in etching, and the width L of the through groove 26. be able to. That is, the width L of the through groove 26 can be calculated from the thickness H of the frame portion 16 and the angle θ of the inclined surface. If the measured through groove width is smaller than the calculated width L of the through groove 26 by an amount corresponding to l, the piezoelectric vibrating piece is manufactured by the method of the present invention. Become.

  Next, the piezoelectric vibrator of the present invention will be described with reference to FIG. The piezoelectric vibrator of this embodiment is a CSP (Chip Size Package) piezoelectric vibrator 100 in which the piezoelectric vibrating piece 10 manufactured by the processes of S100 to S160 is sandwiched between flat lid bodies 50 and 52. is there. In the piezoelectric vibrator 100 having such a configuration, the connection electrode 20 is appropriately routed and electrically connected to the mounting electrode 54 provided on the lid 52.

  By the way, the conventional CSP piezoelectric vibrator has formed a concave portion in the lid body to avoid the lid body from coming into contact with the vibrating portion. However, since the piezoelectric vibrator 100 having the above-described configuration has the vibrating portion 14 of the piezoelectric vibrating piece 10 thinner than the frame portion 16, the flat lid bodies 50 and 52 are directly joined to the frame portion 16. Also, the excitation of the vibration part 14 is not hindered. Therefore, the lid itself can be thinned to the extent that it is not necessary to form the recesses in the lids 50 and 52, and the piezoelectric vibrator 100 itself is also thinned.

  Further, by forming a through groove 26 (see FIG. 1) between the vibrating portion 14 and the frame portion 16 of the piezoelectric vibrating piece 10, a difference in thermal expansion coefficient between the lid bodies 50 and 52 and the piezoelectric vibrating piece 10, etc. It is possible to avoid the stress caused by the propagation to the vibration part 14. Therefore, the vibration part 14 becomes less susceptible to the stress generated in the package due to the temperature change, and the temperature characteristics can be kept good.

It is explanatory drawing of a piezoelectric vibrating piece. It is explanatory drawing which concerns on the manufacturing method of the piezoelectric vibrating piece of this invention. It is a schematic sectional drawing concerning the piezoelectric vibrator of the present invention. It is explanatory drawing which concerns on the manufacturing method of the conventional piezoelectric vibrating piece. It is explanatory drawing at the time of carrying out the chemical etching of the quartz substrate.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ......... Piezoelectric vibration piece, 12 ......... Piezoelectric substrate, 14 ......... Vibration part, 16 ......... Frame part, 18 ......... Excitation electrode, 20 ...... Connection electrode, 22 ...... Extraction electrode, 24... Support part, 26.

Claims (3)

A method of manufacturing a piezoelectric vibrating piece comprising a vibrating part and a frame part surrounding the vibrating part, and providing a through groove between the vibrating part and the frame part,
Adjusting the thickness of the piezoelectric substrate corresponding to the portion constituting the vibrating portion and the through groove to a predetermined thickness by chemical etching;
A method of manufacturing a piezoelectric vibrating piece, comprising subjecting the piezoelectric substrate having the adjusted thickness to chemical etching again to form a through groove. A method of manufacturing a piezoelectric vibrating piece comprising a vibrating part and a frame part surrounding the vibrating part, and providing a through groove between the vibrating part and the frame part,
Forming a first corrosion-resistant film corresponding to the shape of the frame portion on the piezoelectric substrate, and chemically etching a portion constituting the vibrating portion and the through groove to have a thickness corresponding to the oscillation frequency; ,
Forming a second corrosion-resistant film in a portion other than the portion constituting the through groove in the piezoelectric substrate, and forming the through groove by chemical etching;
A method for manufacturing a piezoelectric vibrating piece, comprising:   3. The method of manufacturing a piezoelectric vibrating piece according to claim 2, wherein an electrode pattern of the piezoelectric vibrating piece is formed using the second corrosion-resistant film.

Images