JP2010074257A - Method of manufacturing piezoelectric vibration piece - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a piezoelectric vibration piece by which an outer shape of a grooved piezoelectric vibration piece can be formed with high accuracy. <P>SOLUTION: When manufacturing the grooved piezoelectric vibration piece, only a surface metal layer (second metal layer 13: Au) of an area (formation-planned area) corresponding to grooves 3 in the first stage of a manufacturing process is first removed, a resist pattern (second resist pattern 24) is formed on the surface of the surface metal layer (second metal layer 13: Au) so as to cover a base metal layer (first metal layer 12: Cr) exposed by the removal of the surface metal layer to thereby prevent side etching of the base metal layer (first metal layer 13: Cr) due to the effect of electrical corrosion in the preceding stage of forming the outer shape of the piezoelectric vibration piece. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a piezoelectric vibrating piece.

  2. Description of the Related Art Conventionally, a so-called grooved piezoelectric vibrating piece in which a groove for improving vibration characteristics is formed on a surface is known as one of piezoelectric vibrating pieces made of a piezoelectric material such as quartz.

  FIG. 2 is a top view showing a grooved piezoelectric vibrating piece and an AA cross-sectional view thereof. The grooved piezoelectric vibrating piece shown here is made of a piezoelectric material made of quartz, and has a base 1 serving as a fixing portion to an external mounting substrate (package substrate or the like), and from the base 1 along its main surface. This is a so-called grooved tuning-fork type piezoelectric vibrating piece provided with two protruding branch portions 2 and box-shaped groove portions 3 formed on both main surfaces of the two branch portions 2.

  3A, 3B, and 3C are cross-sectional views taken along line AA showing a conventional method for manufacturing the piezoelectric vibrating piece shown in FIG. When the piezoelectric vibrating piece shown in FIG. 2 is manufactured, first, as shown in FIG. 3B, on both main surfaces of the flat plate-like quartz substrate 11 as shown in FIG. In this way, a first metal layer 12 made of Cr (chromium) and a second metal layer 13 made of Au (gold) are sequentially formed, and then, as shown in FIG. A photoresist layer 14 made of a positive or negative photoresist material is formed on the entire surface of the metal layer (Au) 13 and then exposed and developed, as shown in FIG. A first resist pattern 15 corresponding to the outer shape of the piezoelectric vibrating piece is formed on the surface of the second metal layer (Au) 12.

  Thereafter, as shown in FIG. 3E, the first resist pattern 15 is used as an etching mask, and the second metal layer (Au) 13 in the exposed region is used as an etching solution containing iodine as a main component (iodine-based etching). Then, as shown in FIG. 3-2 (f), the first resist pattern 15 that has been used once is exposed and developed again, so that the groove portion 3 is removed. A second resist pattern 16 having an opening corresponding to the outer shape (formation planned region) is formed, and the second resist pattern 16 and the second metal layer (Au) 13 exposed from the second resist pattern 16 are etched. As shown in FIG. 3-2 (g), wet etching using an etching solution (nitric acid-based etching solution) containing nitric acid as a main component is used for the first metal layer (Cr) 12 in the exposed region. As shown in FIG. 3-2 (h), the quartz substrate 11 exposed by the etching is removed by using an etching solution containing hydrofluoric acid as a main component (hydrofluoric acid-based etching solution), and the piezoelectric vibration is removed. Form the outer shape of the piece.

Thereafter, as shown in FIG. 3-2 (i), the second metal layer (Au) 13 and the first metal layer (in the region where the groove 3 is to be formed) and the first metal layer ( Cr) 12 is sequentially removed by wet etching using an iodine-based etching solution and a nitric acid-based etching solution, respectively, and then the second resist pattern 16 is removed by a stripping solution as shown in FIG. 3-2 (j). Then, as shown in FIG. 3-3 (k), the quartz substrate 11 in the exposed region is partially etched by wet etching using a hydrofluoric acid-based etching solution using the second metal layer (Au) 13 as an etching mask. As shown in FIG. 3L, finally, the second metal layer (Au) 13 and the first metal layer (Cr) 12 remaining at this point are respectively removed. Iodine etching Sequentially removing the tuning fork type piezoelectric vibrating piece with a groove is completed by wet etching using nitric acid-based etching solution as. (For example, see Patent Document 1)
JP 2006-86925 A

  In the conventional method of manufacturing a piezoelectric vibrating piece described above, when the first metal layer (Cr) 12 is removed by etching in the step shown in FIG. 3-2 (g), the second laminated on the second metal layer (Cr) 12 is removed. The contact effect caused by the difference in ionization tendency with the metal layer (Au) 13 occurs, and the etching of the first metal layer (Cr) 12 is promoted unnecessarily, so that the first metal layer (Cr) 12 However, there is a problem in that so-called side etching occurs in which etching occurs more than necessary.

  The electric contact effect is that a potential difference (electromotive force) is generated between different kinds of metals immersed directly in an electrolyte solution according to the principle of the battery, and a current is generated from a metal with a low ionization tendency toward a higher metal among the different kinds of metals. In the step shown in FIG. 3-2 (g), when the first metal layer (Cr) 12 is etched, the etching solution is the electrolyte solution, the first metal layer (Cr) 12 is the negative electrode, and the second metal. A pseudo battery having the layer (Au) 13 as the positive electrode is configured, and the second metal layer (Au) 13 having a relatively low ionization tendency is directed toward the first metal layer (Cr) 12 that is higher than the second metal layer (Au) 13. Current is generated, which accelerates ion exchange in the etchant, thereby speeding up the etching of the first metal layer (Cr) 12.

  FIG. 4 is a cross-sectional view schematically showing a state in which side etching has occurred in the first metal layer. As shown here, the first metal layer (Cr) in the step shown in FIG. When side etching occurs in the second metal layer (Au) 13, the outer shape of the first metal layer (Cr) 12 becomes smaller than the outer shape of the second metal layer (Au) 13 that is an upper layer. When a gap 17 is formed between the quartz substrate 11 and the outer shape of the piezoelectric vibrating piece is formed by etching the quartz substrate 11 in the subsequent step shown in FIG. As the erosion of the substrate 11 progresses, the outer dimensions of the piezoelectric vibrating piece change (decrease), and the vibration characteristics of the piezoelectric vibrating piece change. Note that it is difficult to control the etching in consideration of the electric contact effect.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing a piezoelectric vibrating piece capable of forming the outer shape of the piezoelectric vibrating piece with high accuracy.

  A method for manufacturing a piezoelectric vibrating piece having a groove formed on a surface thereof, comprising: forming a first metal layer on at least a surface of a substrate made of a piezoelectric material; and forming the first metal layer on the surface of the first metal layer. Forming a second metal layer having a smaller ionization tendency than the metal layer, forming a first resist pattern in which a region corresponding to the outer shape of the groove is opened on the surface of the second metal layer; A first etching step for removing the second metal layer exposed from the opening of the first resist pattern by etching, a step for removing the first resist pattern, and an exposure by the first etching step. Forming a second resist pattern corresponding to the outer shape of the piezoelectric vibrating reed on the surface of the second metal layer so as to cover the first metal layer, and exposing the second metal layer from the second resist pattern. A second etching step for removing the second metal layer by etching; a third etching step for removing the first metal layer exposed by the second etching step by etching; The substrate exposed by the etching process is removed by etching to form an outer shape of the piezoelectric vibrating piece, the fourth resist pattern is removed, and the second resist pattern is removed. A fifth etching step for removing the exposed first metal layer by etching, and a sixth etching step for removing a part of the substrate exposed by the fifth etching step to form a groove. And an etching process.

  The step of removing the second resist pattern immediately after the third etching step may be a method for manufacturing a row piezoelectric vibrating piece.

  The piezoelectric vibrating piece manufacturing method may include a step of removing the second resist pattern immediately after the fourth etching step.

  The first metal layer may be made of Cr, and the second metal layer may be a method of manufacturing a piezoelectric vibrating piece made of Au.

  According to the present invention, only the surface metal layer (second metal layer: Au) in the region corresponding to the groove is removed in the first stage of the manufacturing process, and the underlying metal layer (first metal layer) exposed thereby is removed. : Cr) is covered with a resist (second resist pattern), so that the outer side of the piezoelectric vibrating reed of the base metal layer (Cr) due to the electric contact effect is formed before the outer shape of the piezoelectric vibrating reed is formed. Since the etching is prevented, the outer shape of the piezoelectric vibrating piece can be accurately formed in the subsequent crystal substrate etching step (outer shape forming step).

  1-1, FIG. 1-2, and FIG. 1-3 are AA cross-sectional views showing the manufacturing method of the present invention for the piezoelectric vibrating piece shown in FIG. When the piezoelectric vibrating piece shown in FIG. 2 is manufactured by using the manufacturing method of the present invention, first, on both main surfaces of the plate-like quartz substrate 11 as shown in FIG. As shown in 1-1 (b), a first metal layer 12 made of Cr (chromium) and a second metal layer 13 made of Au (gold) are sequentially formed by sputtering or the like.

  Thereafter, as shown in FIG. 1-1C, a positive photoresist material is uniformly applied to the entire surface of the second metal layer (Au) 13 to form a photoresist layer 21. Subsequently, As shown in FIG. 1-1 (d), an area corresponding to the outer shape of the groove 3 (formation planned area) is exposed using a photomask among the areas where the photoresist layer 21 is formed, and the exposed areas are exposed. The photoresist layer 21 is removed with a developing solution, thereby forming a first resist pattern 22 in which a region where the groove 3 is to be formed is opened. The first resist pattern 22 can also be formed using a negative photoresist material.

  Thereafter, as shown in FIG. 1-1 (e), the first resist pattern 22 is used as an etching mask, and the second metal layer (Au) 13 in the exposed region is used as an etching solution containing iodine as a main component (iodine-based etching solution). Then, as shown in FIG. 1-2 (f), the first resist pattern 22 after use is removed with a stripping solution, and then, as shown in FIG. 1-2 (g). As shown in FIG. 5, a positive photoresist material is uniformly applied to the entire surface of the second metal layer (Au) 13 so as to cover the first metal layer (Cr) 12 exposed from the region where the groove 3 is to be formed. Then, a photoresist layer 23 is formed, and an unnecessary region outside the region corresponding to the outer shape of the piezoelectric vibrating piece to be formed (outer shape planned region) is removed from the region where the photoresist layer 23 is formed using a photomask. make use of The photoresist layer 23 in the exposed area is exposed to light and removed with a developer, thereby forming a second resist pattern 24 that covers a predetermined outer area of the piezoelectric vibrating piece, as shown in FIG. To do. Note that the second resist pattern 24 can also be formed using a negative photoresist material.

  Thereafter, as shown in FIG. 1-2 (i), the second metal layer (Au) 13 in the exposed region is removed by wet etching using an iodine-based etchant using the second resist pattern 24 as an etching mask, Subsequently, as shown in FIG. 1-2 (j), the first metal layer (Cr) 12 exposed thereby is etched with ceric ammonium nitrate as a main component (cerium ammonium nitrate system). It is removed by wet etching using an etching solution.

  Here, in the case of the conventional manufacturing method, the second metal layer (Au) 13 is formed from the region where the groove 3 is to be formed in the step shown in FIG. 3-2 (f) (corresponding to FIG. 1-2 (i)). When the first metal layer (Cr) 12 is removed by etching in the subsequent step (corresponding to FIG. 1-2 (j)) shown in FIG. Although an electric contact effect has occurred between the metal layer (Cr) 12 and the second metal layer (Au) 13, in the manufacturing method of the present invention, the groove 3 is formed in the step shown in FIG. The second metal layer (Au) 13 itself does not exist in the region where the film is to be formed, and the surface and inner surface of the remaining second metal layer (Au) 13 are covered with the second resist pattern 24. Because it is not exposed to the outside and is not in direct contact with the etching solution that is the electrolyte solution, it continues Even when the first metal layer (Cr) 12 is etched in the step shown in 1-2 (j), the electric current is generated between the first metal layer (Cr) 12 and the second metal layer (Au) 13. A tactile effect does not occur, and side etching of the first metal layer (Cr) 12 is prevented. However, strictly speaking, since only the outer surface of the second metal layer (Au) 13 is exposed from the second resist pattern 24 at this time, theoretically, the first metal layer (Cr) 12 and An electric contact effect occurs between the two, but since the region is extremely narrow, it has a negligible influence.

  Thereafter, the quartz substrate 11 exposed by removing the first metal layer (Cr) 12 is, as shown in FIG. 1-3 (k), a buffer that is hydrofluoric acid or a mixture of hydrofluoric acid and ammonium fluoride. The outer shape of the piezoelectric vibrating piece is formed by removing by wet etching using dofluoric acid (hydrofluoric acid-based etching solution).

  At this time, since the second resist pattern 24 covering the region where the groove 3 is to be formed has low resistance to the hydrofluoric acid-based etching solution for etching the crystal substrate 11, the hydrofluoric acid-based etching solution is The resist pattern 24 is gradually eroded and permeated, and the first metal layer (Cr) 12 underneath is eroded, but the first metal layer (Cr) 12 has a thickness sufficient to withstand it (for example, If there is about 500cm), there is no problem.

  Considering the above, the second resist pattern 24 is not necessarily required when the quartz substrate 11 is etched in the process shown in FIG. It may be removed at the stage where the role of the etching mask for one metal layer (Cr) 12 is finished (immediately after the step shown in FIG. However, in this case, since the thickness of the first metal layer (Cr) 12 needs to be increased more than usual because there is no second resist pattern 24, the second until the quartz crystal substrate 11 is etched. It is preferable to leave the resist pattern 24.

  After the etching of the quartz substrate 11 is completed as described above, the second resist pattern 24 after use is removed with a stripping solution as shown in FIG. As shown in (m), using the second metal layer (Au) 13 as an etching mask, the exposed first metal layer (Cr) 12 is removed by wet etching using a ceric ammonium nitrate-based etchant. To do.

  At this time, since the second metal layer (Au) 13 is exposed to the outside, an electric contact effect is generated between the first metal layer (Cr) 12 and the first metal layer (Cr) 12. Although side etching occurs, the frequency variation with respect to the outer dimension of the branch 2 of the tuning-fork type piezoelectric vibrating piece is 10,000 ppm / μm, whereas the frequency variation with respect to the width of the groove 3 is 2000 ppm / μm. The amount of frequency change with respect to the width dimension is about 1/5 of that with respect to the outer dimension of the branch part 2. Even if the size changes by the same amount due to the galvanic effect, the amount of change in frequency is acceptable for normal design. Can be small.

  Thereafter, the quartz substrate 11 exposed from the region where the groove 3 is to be formed is removed by a certain amount by wet etching using a hydrofluoric acid-based etchant to form the groove 3 as shown in FIG. Subsequently, as shown in FIG. 1-3 (o), the second metal layer (Au) 13 and the first metal layer (Cr) 12 remaining at this time are respectively converted into an iodine-based etching solution and ceric nitrate. By sequentially removing by wet etching using an ammonium-based etching solution, the grooved tuning-fork type piezoelectric vibrating piece shown in FIG. 2 is completed.

  As mentioned above, although one Embodiment of this invention was described, the 1st metal layer 12 and the 2nd metal layer 13 are not limited to the combination of Cr and Au, The ionization tendency of the 2nd metal layer 13 Is a combination of metals that satisfies the condition that is smaller than that of the first metal layer 12, any combination is possible without departing from the gist of the present invention, for example, the first metal As a combination of the layer 12 and the second metal layer 13, Ni and Au, Ti and Pd, or the like can be selected.

  If the second metal layer 13 is made of a material having the same or higher ionization tendency as that of the first metal layer 12, theoretically, no contact effect will occur. In consideration of the original role of the metal layer 13 as a corrosion-resistant layer, compatibility with the first metal layer 12, and material costs, a material that satisfies all of these conditions within an allowable range must be selected. The materials that can be used are extremely limited.

  In the above description, the tuning fork type piezoelectric vibrating piece is exemplified as the grooved piezoelectric vibrating piece. However, the present invention can also be applied to a piezoelectric vibrating piece having a rectangular shape in plan view.

AA sectional view showing the manufacturing method of the present invention of a piezoelectric vibrating piece AA sectional view showing the manufacturing method of the present invention of a piezoelectric vibrating piece AA sectional view showing the manufacturing method of the present invention of a piezoelectric vibrating piece A top view showing a grooved piezoelectric vibrating piece and a sectional view taken along the line AA AA sectional view showing a conventional method of manufacturing a piezoelectric vibrating piece AA sectional view showing a conventional method of manufacturing a piezoelectric vibrating piece AA sectional view showing a conventional method of manufacturing a piezoelectric vibrating piece Sectional drawing which shows the state which side etching produced in the 1st metal layer typically

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base part 2 Branch part 3 Groove part 11 Quartz substrate 12 1st metal layer 13 2nd metal layer 14 Resist layer 15 1st resist pattern 16 2nd resist pattern 17 Crevice 21 Resist layer 22 1st resist pattern 23 Resist Layer 24 Second resist pattern

Claims (4)

A method of manufacturing a piezoelectric vibrating piece having a groove formed on a surface, at least,
Forming a first metal layer on a surface of a substrate made of a piezoelectric material;
Forming a second metal layer having a smaller ionization tendency than the first metal layer on the surface of the first metal layer;
Forming a first resist pattern in which a region corresponding to the outer shape of the groove is opened on the surface of the second metal layer;
A first etching step of removing the second metal layer exposed from the opening of the first resist pattern by etching;
Removing the first resist pattern;
Forming a second resist pattern corresponding to the outer shape of the piezoelectric vibrating piece on the surface of the second metal layer so as to cover the first metal layer exposed by the first etching step;
A second etching step of removing the second metal layer exposed from the second resist pattern by etching;
A third etching step for removing the first metal layer exposed by the second etching step by etching;
A fourth etching step of removing the substrate exposed by the third etching step by etching to form an outer shape of the piezoelectric vibrating piece;
Removing the second resist pattern;
A fifth etching step of removing the first metal layer exposed by removing the second resist pattern by etching;
A sixth etching step of forming a groove by partially removing the substrate exposed by the fifth etching step by etching;
A method of manufacturing a piezoelectric vibrating piece, comprising:   2. The method of manufacturing a piezoelectric vibrating piece according to claim 1, wherein a step of removing the second resist pattern is performed immediately after the third etching step.   2. The method for manufacturing a piezoelectric vibrating piece according to claim 1, wherein a step of removing the second resist pattern is performed immediately after the fourth etching step.   The method of manufacturing a piezoelectric vibrating piece according to claim 1, wherein the first metal layer is made of Cr, and the second metal layer is made of Au.

Images