JP2006186847A - Crystal piece aggregate, its manufacturing method, photomask, and crystal oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystal piece aggregate which is easy to manufacture even if the plate is thick and high in frequency, each of which is easily separable in a crystal substrate for forming a plurality of crystal pieces by etching a crystal substrate with a metal film as a protection film. <P>SOLUTION: The crystal substrate has a cut surface which is parallel to an X axis (electric axis) of the crystal and is tilted against a Z axis (an optical axis), and is provided with: a frame part extended in a direction orthogonal to the X axis on the surface of the crystal substrate; a plurality of crystals formed along the frame part; a first arm part extended in the direction parallel to the X axis from the frame part; and a second arm part extended in the direction parallel to the X axis from an edge part of the first arm part and connected to the crystal piece. The second arm part is characterized by being narrower in width than the first arm part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a structure of a crystal piece assembly formed on a crystal substrate and a manufacturing method thereof.

  Due to the recent demand for miniaturization of electronic devices and communication devices, a crystal resonator that is a key device has been put into practical use with a crystal piece having a size of about 1.2 mm. As a method of manufacturing such an ultra-small crystal resonator, for example, as shown in FIG. 8, a plurality of crystal resonator elements are collectively formed by a photolithographic technique on a circular (or square) crystal substrate, a dicing saw or the like The method of cutting into individual pieces using is generally used.

On the other hand, Japanese Laid-Open Patent Publication No. 11-509052 discloses a method of individually separating crystal pieces from a crystal wafer (one having a plurality of crystal pieces arranged) using a photolithography technique without using a dicing saw. .
FIG. 9 shows the structure of a conventional quartz wafer disclosed in JP-T-11-509052. FIG. 9A illustrates a part of a crystal wafer, and includes a frame 1 extending in a direction parallel to the X-axis (electric axis) of the crystal, and a plurality of electrodes having electrodes arranged along the frame 1. The crystal piece 2 and a groove portion 3 for connecting the frame 1 and the crystal piece 2 are provided.
FIG. 9B shows a cross section of the groove 3 as viewed from the A direction. Z of the wavy arrow in the figure indicates the direction of the Z axis (optical axis) of the crystal.

  The crystal wafer shown in FIG. 9 has a structure in which a pattern of a predetermined protective film (etching resistant film) is formed on the surface of a crystal substrate, and a plurality of crystal pieces 2 are penetrated by chemical etching. have. In addition, a boundary portion between the frame 1 and the plurality of crystal pieces 2 is chemically etched to be in a state before the penetration (groove portion 3), and the crystal piece 2 is held on the frame 1. Here, it should be noted that the cross section of the groove 3 shown in FIG. 9B is slanted. This is because the crystal is provided with anisotropic etching characteristics, and the etching easily proceeds along the Z-axis direction of the crystal axis. Therefore, for example, when the wafer surface (Z ′ direction) is inclined with respect to the Z axis (optical axis) of the crystal as in the AT cut, the cross section of the groove 3 is inclined as shown in FIG. 9B. . When a mechanical force is applied to the groove portion 3, the crystal piece 2 can be easily broken and separated from the frame 1 and divided into individual pieces.

On the other hand, the change in the etching cross section when the portion B in FIG. 9A is viewed from the A direction is shown in FIG. As described above, quartz has anisotropic etching characteristics, but in practice, etching progresses from the state shown in FIG. 10 (a) to the state shown in FIG. 10 (b). Burr occurs at the end of the crystal. When the etching further proceeds from the state of FIG. 10C, a burr is removed as shown in FIG. 10D, and the etching is completed in this state.
Therefore, in the etching, it is necessary to consider over-etching in the Z ′ direction (left and right direction in FIG. 10) and to take a sufficient etching time so that no burrs are left at the end of the crystal.
Japanese National Patent Publication No. 11-509052

However, the conventional method for manufacturing a quartz wafer has the following problems.
That is, when manufacturing a quartz wafer, a sufficient etching time must be taken so that no burr remains at the end of the quartz piece 2 as described above. However, if the etching time is lengthened, the groove portion 3 becomes deeper. In the worst case, the groove portion 3 penetrates to the opposite side, and the crystal piece 2 falls off the frame portion 1. Further, since the depth of the groove portion 3 is greatly influenced by the slit width (“C” portion in FIG. 9) of the etching resistant film (protective film), the groove portion 3 having an appropriate depth can be formed without variation. Therefore, it is necessary to form an etching resistant film (protective film) with high accuracy and to delicately manage the etching conditions.

However, since the high-frequency crystal piece has a very thin plate thickness, a slight variation in the dimensional accuracy of the etching resistant film (protective film) and a slight difference in etching conditions affect the depth of the groove 3, so that the groove 3 is broken. Significantly affects strength. Therefore, it is difficult for the conventional quartz wafer manufacturing method to form a groove 3 having an appropriate depth with high accuracy without variation, and a quartz wafer for high frequency with a constant breaking strength of the quartz piece can be stably produced. It was extremely difficult to manufacture.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method of manufacturing a crystal piece assembly that can be easily manufactured even with a high-frequency one having a thin plate thickness. .

  In order to solve the above-mentioned problem, in the invention described in claim 1, a quartz substrate having a cut surface parallel to the X axis (electric axis) of the quartz and inclined with respect to the Z axis (optical axis). A frame portion extending in a direction perpendicular to the X-axis on the surface of the quartz substrate, a plurality of crystal pieces formed along the frame portion, and a direction parallel to the X-axis from the frame portion A first arm portion extended; and a second arm portion extending from an end of the first arm portion in a direction parallel to the X axis and connected to the crystal piece, the second arm portion Is narrower than the first arm portion.

According to a second aspect of the present invention, in the first aspect, when the thickness of the quartz crystal substrate is t, the length of the second arm portion in the direction parallel to the X axis is 0.05 t to 1.. 0t.
According to a third aspect of the present invention, in the first or second aspect, when the thickness of the quartz substrate is t, the length of the second arm portion in the direction perpendicular to the X axis is 0. .08t to 0.7t.
Moreover, in invention of Claim 4, in Claim 1, Claim 2, or Claim 3,
The second arm portion is thinner than the other portions.

According to a fifth aspect of the present invention, in the first, second, third, or fourth aspect, the quartz substrate is an AT-cut quartz.
According to a sixth aspect of the present invention, in the first, second, third, fourth, or fifth aspect, an electrode is formed on each of the crystal pieces.
According to a seventh aspect of the present invention, in the sixth aspect, the second arm portion is broken to separate the crystal piece into individual pieces, which are housed in a package and sealed.

  According to an eighth aspect of the invention, there is provided a method for producing a crystal piece assembly according to any one of the first, second, third, fourth, or fifth aspect of the invention, which is a parallel plate. Forming a metal film on the main surface of the quartz substrate, applying a photoresist on the metal film, covering the photoresist with a photomask, and exposing and developing the photoresist to obtain a predetermined photo Forming a resist pattern; etching the metal film using the photoresist pattern as a protective film to form a metal film pattern; and etching the quartz substrate using the metal film pattern and the photoresist pattern as a protective film Etching and integrally forming the frame part, the crystal piece, the first arm part, and the second arm part; and the photoresist pattern It is obtained by a step of peeling ting and the metal film pattern.

  The invention according to claim 9 is the method of manufacturing the crystal piece assembly according to claim 6, wherein a step of forming a metal film on a main surface of a parallel plate crystal substrate; Applying a photoresist to the substrate, covering the photoresist with a photomask, exposing and developing the photoresist to form a predetermined photoresist pattern, and forming the metal film with the photoresist pattern as a protective film Etching to form a metal film pattern; and etching the crystal substrate using the metal film pattern and the photoresist pattern as a protective film to etch the frame part, the crystal piece, the first arm part, and the second arm part. A step of separating the photoresist pattern and the metal film pattern, and a predetermined electrode on the crystal piece It is obtained by a step of depositing a turn at deposition.

  According to a tenth aspect of the present invention, there is provided a method for producing a crystal piece assembly according to the sixth aspect, wherein a step of forming a metal film on a main surface of a parallel plate crystal substrate, Applying a photoresist to the substrate, covering the photoresist with a photomask, exposing and developing the photoresist to form a predetermined photoresist pattern, and forming the metal film with the photoresist pattern as a protective film Etching to form a metal film pattern; and etching the crystal substrate using the metal film pattern and the photoresist pattern as a protective film to etch the frame part, the crystal piece, the first arm part, and the second arm part. A step of stripping the photoresist pattern to expose the metal film pattern, and the exposed metal film A step of applying a photoresist on the turn; a step of exposing and developing the photoresist to form a photoresist pattern for an electrode; and etching the metal film pattern using the photoresist pattern for the electrode as a protective film. And a step of forming a predetermined electrode pattern on the crystal piece.

  The invention according to claim 11 is the photomask described in the method for manufacturing a crystal piece assembly according to any one of claim 8, claim 9, or claim 10, and corresponds to the crystal piece. A crystal piece forming pattern, a first arm portion forming pattern corresponding to the first arm portion, a second arm portion forming pattern corresponding to the second arm portion, which is narrower than the first arm portion forming pattern, and A frame portion forming pattern corresponding to the frame portion, and when the thickness of the quartz substrate is t, the length ranges of two sides perpendicular to each other of the second arm portion forming pattern are each 0.05 t. -1.0t and 0.2t-1.0t.

  The present invention extends on a surface of a quartz substrate having a cut surface parallel to the X axis (electric axis) of the quartz crystal and inclined with respect to the Z axis (optical axis) in a direction perpendicular to the X axis. A frame portion, a plurality of crystal pieces formed along the frame portion, a first arm portion extending from the frame portion in a direction parallel to the X axis, and an end portion of the first arm portion A narrow second arm portion extending in a direction parallel to the X axis and connected to the crystal piece, and the frame portion, the crystal piece, the first arm portion, and the second arm portion are chemically It is formed integrally by etching. Therefore, the present invention provides a crystal piece assembly in which the second arm portion can be manufactured with high accuracy and can be applied to a high-frequency crystal having a very thin plate thickness, and a crystal piece assembly having a constant breaking strength of the crystal piece and a method for manufacturing the same It is effective in providing.

The present invention will be described based on the embodiments shown in the drawings.
FIG. 1 shows the appearance (part) of a crystal piece assembly according to the present invention.
The crystal piece assembly of the present invention is, for example, on the surface of a crystal substrate having a cut surface that is parallel to the X axis (electric axis) and tilted with respect to the Z axis (optical axis), such as AT cut, A frame portion 4 extending in a direction orthogonal to the X axis (Z ′ direction), a plurality of crystal pieces 5 (only one is displayed) arranged in the Z ′ direction along the frame portion 4, and A first arm portion 6 extending from the frame portion 4 in a direction parallel to the X axis, and an end portion of the first arm portion 6 extending in a direction parallel to the X axis and connected to the crystal piece 5 The second arm portion 7 is provided. Note that an electrode (not shown) is formed on the crystal piece 5.

The most characteristic feature of the present invention is that the frame portion 4 extends in the Z ′ direction, a plurality of crystal pieces 5 are arranged along the frame portion 4, and the frame portion 4 is held in order to hold the crystal pieces 5 on the crystal substrate. The first arm portion 6 and the second arm portion 7 are integrally formed with the crystal piece 5.
The reason why the first arm portion 6 that is wider and longer than the second arm portion 7 is provided between the second arm portion 7 and the frame portion 4 is that the area of the region indicated by C in FIG. This region is considered so as to be easily penetrated by etching.

Here, the manufacturing method of the crystal | crystallization piece aggregate | assembly of this invention is demonstrated.
FIG. 2 illustrates the steps of the method for producing a crystal piece assembly according to the present invention.
First, a metal film of Au (gold) is vapor-deposited on a quartz substrate with Cr (chrome) as a base. (Fig. 2 (a) (b))
Next, a photoresist is applied on the metal film (FIG. 2C), and a photomask (not shown) is covered thereon, and the photoresist is exposed and developed to form a predetermined photoresist pattern. (Fig. 2 (d))
Next, the metal film is etched using the photoresist pattern as a protective film to form an external pattern (metal film pattern) of the crystal piece 2, the first arm portion 6, the second arm portion 7, and the frame portion 4. (FIG. 2 (e)) Next, the exposed quartz crystal is chemically etched using the photoresist pattern and the metal film pattern as a protective film, so that the crystal piece 2, the first arm portion 6, the second arm portion 7, and the frame portion are etched. 4 are formed together. (FIG. 2 (f)) Next, the photoresist pattern and the metal film pattern are peeled off (FIG. 2 (g)), and a metal mask is placed thereon to deposit an electrode on the crystal piece 5. FIG. (FIG. 2 (h)) This state is the crystal piece aggregate shown in FIG.
Next, the second arm portion 7 is mechanically broken to separate the crystal piece 5 into individual pieces. (FIG. 2 (i)) Then, if this is housed in a predetermined package and sealed, a crystal resonator is completed.

Here, a process of etching the second arm portion 7 will be described. FIG. 3 shows how the cross section AA ′ changes as etching progresses. (The photoresist pattern on the Au film is not shown.)
In FIG. 3, etching proceeds sequentially along the direction of the Z-axis (optical axis) of the crystal. In the middle, burrs are generated at the end of the crystal (FIG. 3C), but if the etching is further advanced, the burrs disappear and the etching is completed in the state of FIG.
On the other hand, FIG. 4 shows an etching cross section of BB ′ in FIG. Due to the anisotropic etching characteristics of quartz, it is hardly etched in the X-axis direction compared to the Z-axis direction.
Therefore, for the metal film pattern (Au film, Cr film) on the second arm portion 7, if the amount of overetching in the Z ′ direction is anticipated in advance and the dimensional accuracy of Z′2 is sufficiently formed, the etching time, etc. Even if the etching conditions change slightly, the second arm portion 7 does not fall off due to etching.

The inventors made two types of crystal piece assemblies according to the present invention. Both prototypes confirm that the second arm portion 7 is stably held without dropping from the quartz substrate during the work after the etching process. In addition, it was confirmed that the crystal piece 5 was easily broken from the second arm portion 7 with a constant force, and crystal chips were hardly generated from the broken portion. Note that the dimensions of a photomask pattern for forming a photoresist pattern (metal film pattern) are X1≈100 μm, Z′1≈100 μm, X2≈20 μm, and Z′2 = 20 μm (or 40 μm). At this time, the thickness of the crystal piece 5 is 63 μm.
Examining the results of trial production, etc., regarding the pattern size of the photomask, assuming that the thickness t excluding the electrode portion of the crystal piece 5 is about 30 to 100 μm, 0.05 t ≦ X2 ≦ 1.0 t, 0.2 t ≦ It has been found that a range of Z′2 ≦ 1.0 t is appropriate. Further, with respect to the dimension of the second arm portion in the Z ′ direction, a width of at least 5 μm is necessary to physically hold the crystal piece 5, and considering the amount of overetching in this direction, Z ′ It has been found that the direction dimension (Z′2) is suitably in the range of 0.08 t (5 μm) to 0.7 t.

In the embodiment described above, the metal film pattern (Au film, Cr film) on the second arm portion 7 is arranged symmetrically on both surfaces with the quartz substrate interposed therebetween as shown in FIG. However, the present invention is not limited to this. For example, as shown in FIG. 5, the metal film patterns on both sides may be displaced in the Z ′ direction with the quartz crystal substrate interposed therebetween. In this case, although the cross section of the second arm portion 7 is slanted, the crystal piece 5 is not dropped during the work after the etching step, and the second arm portion 7 can be easily broken only by applying a predetermined force. Can do.
Further, as shown in FIG. 6, the widths of the metal film patterns on both sides may be different. In this case, a part of the upper side of the second arm part 7 is penetrated by etching and the thickness is thinner than the other part, but the second arm part 7 is not dropped. Alternatively, a metal film pattern as shown in FIG. 7 may be used.

Further, in the method of manufacturing the crystal piece aggregate, the steps shown in FIGS. 2G and 2H may be changed as follows. That is, only the photoresist pattern is peeled off from the state of FIG. Next, a photoresist is applied again from above. Next, a photomask for electrodes (different from the photomask in FIG. 2D) is put on, exposed and developed to form a photoresist pattern for electrodes. Then, the metal film pattern is etched using the electrode photoresist pattern as a protective film to form an electrode on the crystal piece 5, and the electrode photoresist pattern is peeled off.
As described above, the present invention provides a manufacturing method effective for stably manufacturing a crystal piece assembly having a thin plate thickness and a high frequency, and its applicability is extremely high.

External view of quartz crystal aggregate according to the present invention Process drawing of manufacturing method of crystal piece aggregate according to the present invention Phase diagram of etching of quartz crystal aggregate according to the present invention (first embodiment) Phase diagram of etching of quartz crystal aggregate according to the present invention (first embodiment) State diagram of etching of quartz crystal aggregate according to the present invention (second embodiment) State diagram of etching of quartz crystal aggregate according to the present invention (third embodiment) State diagram of etching of quartz crystal aggregate according to the present invention (fourth embodiment) External view of conventional quartz wafer (first conventional example) External view of a conventional quartz wafer (second conventional example) State diagram of conventional quartz wafer etching (second conventional example)

Explanation of symbols

1, 4 ·· Frame portion 2, 5 ·· Crystal piece 3 · · Groove portion 6 · · First arm portion 7 · · Second arm portion

Claims (11)

  A quartz substrate having a cut surface parallel to the X axis (electrical axis) of the quartz crystal and inclined with respect to the Z axis (optical axis), and extending in a direction perpendicular to the X axis of the surface of the quartz substrate. A frame portion provided, a plurality of crystal pieces formed along the frame portion, a first arm portion extending from the frame portion in a direction parallel to the X-axis, and the first arm portion A second arm portion extending in a direction parallel to the X-axis from an end portion and connected to the crystal piece, wherein the second arm portion is narrower than the first arm portion. Crystal piece aggregate.   2. The crystal piece set according to claim 1, wherein a length of the second arm portion in a direction parallel to the X axis is 0.05 t to 1.0 t, where t is a thickness of the crystal substrate. body.   The length in the direction orthogonal to the X axis of the second arm part is 0.08 t to 0.7 t, where t is the thickness of the quartz crystal substrate, or claim 2. The crystal piece aggregate according to any one of the above.   4. The crystal piece assembly according to claim 1, wherein the second arm portion is thinner than other portions. 5.   5. The quartz piece assembly according to claim 1, wherein the quartz substrate is an AT-cut quartz crystal.   6. The crystal piece aggregate according to claim 1, wherein an electrode is formed on each of the crystal pieces.   The quartz crystal manufactured from the crystal piece assembly according to claim 6, wherein the second arm portion is broken to separate the crystal piece into individual pieces, which are housed in a package and sealed. Vibrator.   A method of manufacturing the crystal piece assembly, the step of forming a metal film on a main surface of a parallel plate crystal substrate, the step of applying a photoresist on the metal film, and the top of the photoresist Covering the photomask and exposing and developing the photoresist to form a predetermined photoresist pattern; etching the metal film using the photoresist pattern as a protective film to form a metal film pattern; and the metal film pattern And etching the crystal substrate using the photoresist pattern as a protective film to integrally form the frame portion, the crystal piece, the first arm portion, and the second arm portion, and the photoresist pattern A step of peeling the metal film pattern from the metal film pattern. The claim 1, the claim 2, the claim 3, the claim 4, or Method for manufacturing a quartz piece assembly as claimed in any one of Motomeko 5. A method of manufacturing the crystal piece assembly, the step of forming a metal film on a main surface of a parallel plate crystal substrate, the step of applying a photoresist on the metal film, and the top of the photoresist Covering the photomask and exposing and developing the photoresist to form a predetermined photoresist pattern; etching the metal film using the photoresist pattern as a protective film to form a metal film pattern; and the metal film pattern And etching the crystal substrate using the photoresist pattern as a protective film to integrally form the frame portion, the crystal piece, the first arm portion, and the second arm portion, and the photoresist pattern Peeling the metal film pattern;
The method for producing a crystal piece assembly according to claim 6, further comprising: attaching a predetermined electrode pattern to the crystal piece by vapor deposition.   A method of manufacturing the crystal piece assembly, the step of forming a metal film on a main surface of a parallel plate crystal substrate, the step of applying a photoresist on the metal film, and the top of the photoresist Covering the photomask and exposing and developing the photoresist to form a predetermined photoresist pattern; etching the metal film using the photoresist pattern as a protective film to form a metal film pattern; and the metal film pattern And etching the quartz substrate using the photoresist pattern as a protective film to integrally form the frame portion, the quartz piece, the first arm portion, and the second arm portion, and the photoresist pattern Peeling and exposing the metal film pattern; applying a photoresist on the exposed metal film pattern; Exposing and developing a photoresist to form a photoresist pattern for an electrode, and etching the metal film pattern using the photoresist pattern for the electrode as a protective film to form a predetermined electrode pattern on the crystal piece. The method for producing a crystal piece assembly according to claim 6, wherein the crystal piece aggregate is provided. The photomask has a crystal piece forming pattern corresponding to the crystal piece, a first arm portion forming pattern corresponding to the first arm portion, and a width narrower than the first arm portion forming pattern on the second arm portion. A second arm portion forming pattern corresponding to the frame portion, and a frame portion forming pattern corresponding to the frame portion, wherein two sides of the second arm portion forming pattern orthogonal to each other when the thickness of the quartz substrate is t. The length range of each is 0.05t-1.0t and 0.2t-1.0t, respectively, The crystal piece aggregate | assembly of any one of Claim 8, Claim 9, or Claim 10 characterized by the above-mentioned The photomask described in the manufacturing method.

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