Method for manufacturing quartz wafers and quartz oscillators

Abstract

To provide a crystal wafer and a crystal resonator manufacturing method that can reduce cracks that occur during handling and transportation and improve productivity.SOLUTION: A crystal wafer 10 includes a twinned region 21 in a part or all of an outer circumference 20. The twinned region is a region of at least 2 mm from the periphery to the center of the crystal wafer, and more than 80% of this region is twinned. An etching-resistant mask 13 for forming the external shapes of a large number of crystal resonators in a matrix is formed on the crystal wafer having the twinned region, and the crystal wafer is immersed in an etching solution mainly containing hydrofluoric acid to form the external shape.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a quartz wafer and a quartz oscillator that are less likely to crack during handling and transportation.

Background Art

[0002] In recent years, with the miniaturization of electronic devices and the high-frequencyization of communication frequencies, quartz oscillators are required to be smaller and thinner, and it has become difficult to manufacture quartz oscillators by mechanical processing methods. Therefore, a method is used in which a large number of quartz oscillators are formed in a matrix on a quartz wafer by photolithography technology and wet etching technology, and each quartz oscillator is folded off from the quartz wafer and fragmented. Therefore, in the photolithography process and the fragmentation process, the handling and transportation of the quartz wafer are frequently performed.

[0003] In the wet etching process, typically, an etching solution mainly containing hydrofluoric acid is used. Further, Patent Document 1 discloses that the etching rate of the BT cut (non-vibration region) that becomes a twin crystal with respect to the AT cut (vibration region) is about 2 / 7 (means for solving the problems of Patent Document 1, etc.).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, when wet etching a quartz wafer, a metal film such as Au or a resist film is deposited on areas where etching is not desired, specifically the outer periphery of the quartz wafer, i.e., the outer frame, and on the struts supporting each quartz oscillator within the wafer, to protect the outer frame and struts from the etching solution. However, when depositing the metal film or resist film, it is necessary to hold a part of the outer periphery of the quartz wafer with a jig, so this part cannot be coated with the metal film or resist film and therefore cannot be protected by it. As a result, unintended etching occurs on a part of the outer periphery of the quartz wafer. Consequently, the problem described below with reference to Figure 16 arises. Figure 16(A) is a plan view of a conventional quartz wafer 170. Figure 16(B) is a plan view of an example in which a crack 190 has occurred in a conventional quartz wafer 170. In conventional quartz wafers 170, as shown in Figure 16(A), the outer periphery of the quartz wafer 170 may be etched in an unintended manner during the wet etching process, resulting in the formation of irregularities 180. These irregularities 180 can cause cracks 190, as shown in Figure 16(B), due to the forces applied to the quartz wafer during handling and transport.

[0006] This invention has been made in view of the above points, and therefore, the object of this application is to provide a quartz wafer and a method for manufacturing quartz oscillators having a novel structure that prevents the occurrence of irregularities on the outer periphery of a quartz wafer for forming a large number of quartz oscillators in a matrix, thereby reducing cracks that occur during handling and transport. [Means for solving the problem]

[0007] To achieve this objective, the invention of the quartz wafer of this application is characterized in that a quartz wafer for forming a large number of quartz oscillators in a matrix is ​​provided with a twinning region in part or all of the outer periphery of the quartz wafer.

[0008] Furthermore, according to another invention of this application, a method for manufacturing a quartz crystal oscillator, in which the external shapes of a number of quartz crystal oscillators are formed in a matrix on a quartz wafer using photolithography technology and an etching solution mainly composed of hydrofluoric acid, the method for manufacturing a quartz crystal oscillator is characterized by comprising the steps of forming a twinning region on at least a part or all of the outer periphery of the quartz wafer, and immersing the quartz wafer on which the twinning region has been formed in the etching solution to form the external shapes. In the inventions described above, the twinning region is the region in which another crystal has penetrated the first crystal, the so-called penetration twinning region. That is, if the quartz wafer is made of right-handed quartz, the twinning region is the region of left-handed quartz, and conversely, if the quartz wafer is made of left-handed quartz, the twinning region is the region of right-handed quartz. To give a more specific example, if the quartz wafer is an AT-cut quartz wafer, it is the region that is close to a BT-cut cut region. [Effects of the Invention]

[0009] According to the quartz wafer of this invention, since a twinning region is provided on the outer periphery of the quartz wafer, it is possible to prevent (reduce) unintended etching of the outer periphery from a direction perpendicular to the main surface of the quartz wafer during the wet etching process, thereby reducing the occurrence of irregularities on the outer periphery of the quartz wafer. Consequently, cracks that occur during the handling and transport of the quartz wafer can be reduced, improving productivity by reducing defects during the manufacturing of quartz oscillators. Furthermore, when depositing a metal film or resist film in areas where etching is not desired, even if an unprotected area occurs on the outer periphery due to the influence of a fixing jig, providing the twinning region on that outer periphery prevents or reduces unintended etching. Therefore, productivity can be improved by reducing defects during the manufacturing of quartz oscillators, and there is no need to consider the influence of the fixing jig, thus increasing the freedom of the shape of the fixing jig. Furthermore, according to the method for manufacturing a quartz crystal oscillator of this invention, a twinning region is formed in a predetermined part of the quartz wafer before the process using an etching solution mainly composed of hydrofluoric acid, and then the etching is performed. This prevents the outer periphery from being etched in an unintended manner during the wet etching process. Consequently, cracks that occur during the handling and transport of the quartz wafer can be reduced, allowing for the production of quartz crystal oscillators with high productivity. [Brief explanation of the drawing]

[0010] [Figure 1] This is a plan view of a quartz wafer according to the first embodiment. [Figure 2] This is a plan view of an example of a quartz wafer according to the first embodiment. [Figure 3] This is a plan view of an example of a quartz wafer according to the first embodiment. [Figure 4] This is a plan view of an example of a quartz wafer according to the first embodiment. [Figure 5] This is a plan view of an example of a quartz wafer according to the first embodiment. [Figure 6] This is a plan view of a quartz wafer according to the second embodiment. [Figure 7] This is a plan view of a quartz wafer according to the third embodiment. [Figure 8] This is an explanatory diagram illustrating an embodiment of the manufacturing method for a quartz crystal oscillator according to the present invention. [Figure 9] Figure 8 is an explanatory diagram illustrating an example of the manufacturing process. [Figure 10] This is an explanatory diagram of a manufacturing example, following Figure 9. [Figure 11] This is an explanatory diagram of a manufacturing method example, following Figure 10. [Figure 12] This is an explanatory diagram of a manufacturing method example, following Figure 11. [Figure 13] This is an explanatory diagram of a manufacturing method example, following Figure 12. [Figure 14] This is an explanatory diagram of a manufacturing example, following Figure 13. [Figure 15] This is an explanatory diagram of a manufacturing example, following Figure 14. [Figure 16]FIG. 16(A) is a plan view of a conventional quartz wafer. FIG. 16(B) is a plan view of an example in which a crack has occurred in a conventional wafer.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the method for manufacturing a quartz wafer and a quartz oscillator of this invention will be described with reference to the drawings. Note that each drawing used in the description only schematically shows the inventions to such an extent that they can be understood. Also, in each drawing used in the description, the same components are denoted by the same numbers, and the description thereof may be omitted. Further, the shapes, materials, etc. described in the following description are merely preferred examples within the scope of this invention. Therefore, the present invention is not limited to only the following embodiments.

[0012] 1. Structure of Quartz Wafer FIG. 1 is a plan view of a quartz wafer 10 according to the first embodiment. In the case of this embodiment, the quartz wafer 10 has a circular planar shape and is of the AT cut type in terms of the type of cutting (cutting) from the quartz raw material. However, the planar shape is not limited to a circle and may be rectangular, and the cutting cut is not limited to the AT cut and may be of other cuts such as a two-rotation cut like the Z cut or SC cut. The quartz wafer 10 of the first embodiment includes a frame formation planned region 20 that is not a formation planned region of a quartz oscillator. The frame formation planned region 20 is typically a region composed of an outer frame 20a and a bar 20b to which each quartz oscillator is connected. In this embodiment, the outer frame 20a is called the outer peripheral portion. The example shown in FIG. 1 is an example in which the entire outer peripheral portion 20a is a twinning region 21. By twinning the outer peripheral portion 20a, it is possible to prevent the outer peripheral portion 20a of the quartz wafer 10 from being etched in an unintended state even when wet etching mainly using hydrofluoric acid is performed, and to reduce the degree of unevenness occurring in the outer peripheral portion 20a of the quartz wafer 10. Therefore, it is possible to reduce cracks generated during handling and conveyance of the quartz wafer 10.

[0013] When twinning the outer periphery 20a of a quartz wafer 10, ideally, as shown in Figure 1, it is desirable that the entire outer periphery of the quartz wafer 10 be twinned. However, as shown in Figures 2 and 3, even when a non-twinned region 30 is formed where a portion of the entire area of ​​the outer periphery 20a is not twinned, this is still an embodiment of the present invention. Even in this case, the effect of reducing cracking that occurs during handling and transport of the quartz wafer can be obtained. Furthermore, even if a non-twinned region 30 is formed in a portion of the outer periphery 20a in the wafer thickness direction, the same effect can be obtained. Also, as shown in Figure 4, if a non-twinned region 30 is formed from the outermost periphery of the quartz wafer 10 toward the center, and the twinned region of the outer periphery is interrupted, the possibility of damage to the quartz wafer may be higher compared to when it is not interrupted. However, even in this case, the effect of the twinned region existing in other areas can reduce the risk of damage to the quartz wafer.

[0014] Furthermore, as shown in Figure 5(A), the present invention also includes a case where twinning regions 21 are provided in separate areas 20aa of the outer peripheral portion 20a of the quartz wafer 10. A specific example of this embodiment is, for example, when a metal film as a protective film is deposited on the quartz wafer, or when a resist is applied, a portion of the quartz wafer is held by the jig for depositing the metal film or the jig for applying the resist, and the metal film or resist is not formed in that area. In the example of Figure 5(A), since only the area where the probability of unintended etching is extremely high because it is not covered by the protective film of the quartz wafer is designated as the twinning region, the twinning process time can be shortened compared to the case where the entire outer peripheral portion 20a is twinned. Moreover, the effects of the present invention can be obtained. In the example of Figure 5(A), two partial regions 20aa are provided near the orientation tension flat of the quartz wafer, but the position and number of partial regions 20aa are not limited to the example in Figure 5(A) and can be changed to an appropriate one depending on the purpose. It is perfectly acceptable for some regions, such as region 20aa, to contain only one element.

[0015] Even when a portion of the outer peripheral region 20aa 20aa is designated as a twinned region 21, the edge of the quartz wafer may become a non-twinned region 30, as shown in Figure 5(B). When such a quartz wafer is immersed in a hydrofluoric acid-based wet etching solution for a predetermined time, the edge, being a non-twinned region 30, is etched more than the twinned region. Figure 5(C) shows the results of this observation. Specifically, Figure 5(C) shows the results of observing a cross-section of the quartz wafer after etching, along the A-B line in Figure 5(B). In Figure 5(C), the horizontal axis represents the scanning distance along the A-B line (unit: mm), and the vertical axis represents the change in height caused by etching in the corresponding region (unit: μm). In Figure 5(C), it can be seen that the twinned region 20aa(21) shows no change in height after etching, while the non-twinned region 30 at the edge of the quartz wafer shows a decrease in height due to etching. However, even if the edges of the quartz wafer are etched, the presence of twinning regions in the adjacent area reduces the degree to which etching-induced irregularities occur towards the center of the quartz wafer in the diametrical direction.

[0016] In other words, in the configuration shown in Figure 5, metal films or resist films are present in areas where etching is not desired, while twinning regions exist in areas where there is a high risk of unintended etching, such as areas where protective films such as metal films or resist films cannot be formed due to jigs used during film formation. Therefore, the effect of the twinning regions can reduce the occurrence of irregularities from the edges of the quartz wafer.

[0017] Even if a non-twined region 30 occurs at the edge of the quartz wafer, as shown in Figure 5(B), if it is too large, the effect of the present invention will be reduced. Therefore, if a non-twined region 30 occurs at the edge of the quartz wafer, the width (depth dimension) h1 of the non-twined region 30 from the edge of the quartz wafer toward the center should be within 2 mm, preferably within 1 mm, and more preferably within 0.5 mm. The width (depth dimension) h2 of the twinned region 21 itself from the edge of the quartz wafer toward the center, and the dimensions W1 and W2 in the direction perpendicular to it, should be determined considering the size of the jig used when depositing protective films such as metal films or resist films. However, W1 and W2 may be the same or different. Although not limited to this, it is preferable that each of the above dimensions h2, W1, and W2 be at least 2 mm. If the quartz wafer is, for example, a circular quartz wafer with a diameter of 4 inches, the h2 of the twinned region from the outer circumference toward the center is preferably, for example, 2 mm or more and 12.5 mm or less. More preferably, h2 should be, for example, 3 mm or more and 12.5 mm or less. Expressed as a ratio to the diameter of a 4-inch wafer, this is 2 / 101.6 ≈ 0.02 or more and 12.5 / 101.6 ≈ 0.213 or less, which is 2% or more and 12% or less. Also, W1 and W2 should be 3 mm or more and 16 mm or less, more preferably 4 mm or more and 16 mm or less. This is because, as mentioned above, if the twinning region is too narrow, the effect of preventing etching to an unintended state will not be sufficiently obtained, and it will not be possible to reduce cracks that occur during the handling and transport of the quartz wafer. On the other hand, if the twinning region is too wide, the area where the quartz oscillator is to be formed will be narrowed, and the productivity of the quartz oscillator will be impaired.

[0018] Furthermore, within the twinning region, the twinning rate is not limited to this, but preferably 80% or higher. This is because, as shown in Figure 3, a non-twinned region 30 may occur in a part of the outer periphery of the quartz wafer where twinning does not occur. If the twinning region is too small, the effect of preventing unintended etching will not be sufficiently obtained, and it will not be possible to reduce cracking that occurs during the handling and transport of the quartz wafer.

[0019] Figure 6 is a plan view of the quartz wafer 40 of the second embodiment. The quartz wafer 40 of the second embodiment has a twinned region 50 on its outer periphery, and a twinned region 70 on part or all of the struts connecting each quartz oscillator 60. By twinning part or all of the struts, it is possible to prevent the connecting parts of each quartz oscillator from being etched in an unintended manner, maintain strength, and reduce the occurrence of cracks in the connecting parts of each quartz oscillator.

[0020] Figure 7 is a plan view of the quartz wafer 80 of the third embodiment. The quartz wafer 80 of the third embodiment has a twinning region 90 on its outer periphery, and a twinning region 110 only in the connecting portion where each quartz oscillator 100 is connected to the strut. Even when only the connecting portion is twinned, as in the second embodiment, it is possible to prevent unintended etching of the connecting portion of each quartz oscillator and reduce the occurrence of cracks in the connecting portion of each quartz oscillator.

[0021] 2. Method for manufacturing a quartz crystal oscillator Next, an embodiment of the manufacturing method for the quartz oscillator of the present invention will be described with reference to Figures 8 to 15. The manufacturing method of the present invention is a manufacturing method using photolithography technology and wet etching technology, and includes a special process called twinning. Therefore, Figures 9 to 15 show a plan view of a quartz wafer and an enlarged plan view of a portion Q thereof. Furthermore, some of the drawings in Figures 9 to 15 also include a cross-sectional view along the RR line of a portion Q of the quartz wafer.

[0022] In this manufacturing method, first, as shown in Figure 8, a quartz wafer 11 is prepared, and the quartz wafer 11 is locally heated, for example, with a laser 120, to twinn a part or all of the outer periphery. Note that the means of twinning is not limited to local heating with a laser, but may also be other means such as a spot heater. Furthermore, in this embodiment of the manufacturing method, since the quartz wafer shown in Figure 1 is considered, an example is shown in which the outer periphery 20a and the crossbar 20b of the quartz wafer are twinned. Subsequently, a metal film (not shown) is formed on the quartz wafer 11 to create an etching-resistant mask.

[0023] As shown in Figure 9, the metal film formed on the quartz wafer 11 is processed using a well-known photolithography technique to form an etching-resistant mask 13 on both the front and back surfaces of the quartz wafer 11, which is used to form the outline of the quartz piece 12. In this embodiment, the etching-resistant mask 13 is composed of a portion corresponding to the outer shape of the quartz crystal 12, a strut portion that holds each quartz crystal, and a portion that connects the quartz crystal and the strut portion (connecting portion 14 in Figure 9). Furthermore, the etching-resistant mask 13 is formed so that it faces the front and back sides of the quartz wafer 11.

[0024] Next, the quartz wafer 11, on which the etching-resistant mask 13 has been formed, is immersed in an etching solution mainly composed of hydrofluoric acid for a predetermined time. This process dissolves the parts of the quartz wafer 11 that are not covered by the etching-resistant mask 13, and the rough outline of the quartz piece is obtained, as shown in Figure 10. Since the outer periphery and struts of the quartz wafer 11 are twinned, it is possible to prevent the outer periphery and struts from being etched in an unintended manner during the etching process that forms the outline of the quartz piece.

[0025] Next, the etching-resistant mask 13 is removed from the quartz wafer 11. In this process, as shown in Figure 11, in the manufacturing method of the present invention, only the portion of the etching-resistant mask 13 corresponding to the quartz piece 12 is removed, while the portions corresponding to the struts and connecting parts are left intact. This is to maintain the strength of the struts and connecting parts. Of course, depending on the design, some or all of the etching-resistant mask in the portions corresponding to the struts and connecting parts may be removed.

[0026] Next, the quartz wafer 11 is immersed again in an etching solution mainly composed of hydrofluoric acid for a predetermined time. Here, the predetermined time is the time until the thickness of the area to be formed in the quartz piece 12 reaches a thickness that satisfies the required oscillation frequency specification. Figure 12(B) shows the quartz piece that has achieved the aforementioned thickness. Since the outer periphery and ribs of the quartz wafer 11 are twinned, it is possible to prevent the outer periphery and ribs from being etched in an unintended manner. In this embodiment, an etching step is provided to reduce the thickness of the area where the crystal piece 12 is to be formed. However, if the crystal wafer itself is already of a thickness that can obtain a predetermined oscillation frequency, this step is unnecessary.

[0027] Next, as shown in Figure 13, the etching-resistant mask 13 is removed from the quartz wafer 11 after the etching process is complete, exposing the quartz surface. Subsequently, a metal film (not shown) for forming the excitation and extraction electrodes of the quartz oscillator is formed on the entire surface of the quartz wafer 11 using a well-known film deposition method.

[0028] Next, as shown in Figure 14, this metal film is patterned into an electrode shape using well-known photolithography and metal etching techniques to form an excitation electrode 15a and an extraction electrode 15b on the quartz wafer 11. This makes it possible to obtain a quartz oscillator 16 comprising a quartz crystal 12, an excitation electrode 15a, and an extraction electrode 15b.

[0029] Generally, a structure in which a quartz oscillator 16 is mounted in a suitable container is often referred to as a quartz oscillator. A typical example is described below using Figure 15. Figure 15 shows the procedure for mounting the quartz oscillator 16 in the container 140, using a plan view and a cross-sectional view along the SS line.

[0030] In the state shown in Figure 14, the quartz oscillator 16 is coupled to the quartz wafer 11 via a connecting portion 14. First, an appropriate external force is applied to the connecting portion 14 to separate the quartz oscillator 16 from the quartz wafer 11, and it is broken down into individual pieces as shown in Figure 15(A). On the other hand, as a container, for example, a well-known ceramic package 140 (hereinafter also referred to as package 140) is prepared. In this case, as shown in Figures 15(B) and (C), package 140 has a recess 140a for housing the crystal oscillator 17, a bump 140b for fixing the crystal oscillator provided on the bottom surface of the recess 140a, and mounting terminals 140c provided on the back surface of package 140. The bump 140b and mounting terminals 140c are electrically connected by via wiring (not shown).

[0031] As shown in Figure 15(D), a crystal oscillator 17 is mounted in the recess 140a of the package 140. More specifically, as shown in Figure 15(E), a conductive adhesive 150 is applied to the bump 140b, and the crystal oscillator 17 is fixed to the bump 140b at the location of the lead electrode 15b using this conductive adhesive 150. Subsequently, the oscillation frequency of the crystal quartz 12 is adjusted to a predetermined value using a well-known method. Then, the recess 140a of the package 140 is subjected to a suitable vacuum or inert gas atmosphere, and the recess 140a is sealed with the lid 160 using a well-known method. In this way, a quartz oscillator is obtained in which the quartz oscillator 17 is housed in the package 140.

[0032] In the above embodiment of the manufacturing method, an example was described in which the outer periphery 20a and the struts 20b of the quartz wafer are twinned. However, as explained with reference to Figure 5, a case in which twinning regions 21 are provided in separate areas 20aa of the outer periphery 20a of the quartz wafer 10 is also an embodiment of the manufacturing method of this application. A specific example of this embodiment is, for example, when a metal film as a protective film is formed on a quartz wafer or when a resist is applied, a portion of the quartz wafer is held by a jig for metal film formation or a jig for resist application, and the metal film or resist is not formed in that area. When twinning regions 21 are provided in separate areas 20aa of the outer periphery 20a of the quartz wafer 10 that are covered by the jig, the time required for the twinning process can be shortened compared to twinning the entire outer periphery 20a, which is preferable from the viewpoint of manufacturing throughput. [Explanation of Symbols]

[0033] 10: Quartz wafer of the first embodiment 11: Quartz wafer 12: Crystal piece 13: Etching-resistant mask 14: Connection part 15a: Excitation electrode 15b: Extraction electrode 16: Crystal resonator 20: Area where frame formation is planned 20a: Outer frame 20b: Slats 21: Twinning region 30: Non-twined region 40: Quartz wafer of the second embodiment 50: Twinned region 60: Crystal oscillator 70: Twinned region 80: Quartz wafer of the third embodiment 90: Twinned region 100: Crystal piece 110: Twinned region 120: Heat source 130: Laser 140: Ceramic package 140a: recess 140b: bump 140c: Mounting terminals 150: Conductive adhesive 160: Lid 170: Conventional quartz wafer 180: Unevenness 190: Cracks

Claims

1. In a quartz wafer for forming a large number of quartz oscillators in a matrix, A quartz wafer characterized by having a twinning region in part or all of the outer periphery of the quartz wafer.

2. The quartz wafer according to claim 1, characterized in that a portion of the outer periphery of the quartz wafer is a region where the etching-resistant film cannot be formed by a fixing jig used when forming the etching-resistant film during wet etching of the quartz wafer.

3. The quartz wafer according to claim 1 or 2, characterized in that the twinning region is a region having a width of at least 2 mm from the outer edge of the quartz wafer toward the center.

4. The quartz wafer according to claim 1 or 2, characterized in that the twinning region is a region having a width of 2% to 12% of the diameter from the outer edge of the quartz wafer toward the center.

5. The quartz wafer according to claim 1 or 2, characterized in that the twinning rate within the twinning region is 80% or more.

6. The quartz wafer according to claim 1, comprising struts for connecting the numerous quartz oscillators, wherein part or all of the struts are twinned regions.

7. The quartz wafer according to claim 6, comprising a connecting portion that connects the numerous quartz oscillators and the struts, wherein the connecting portion is a twinned region.

8. In a method for manufacturing a quartz crystal oscillator, in which the outlines of numerous quartz crystal oscillators are formed in a matrix on a quartz wafer using photolithography technology and an etching solution mainly composed of hydrofluoric acid, A step of forming a twinning region on at least a part or all of the outer periphery of the quartz wafer, A step of immersing the quartz wafer on which the twinned region has been formed in the etching solution to form the outer shape, A method for manufacturing a quartz crystal oscillator, characterized by including the following:

9. The method for manufacturing a quartz oscillator according to claim 8, characterized in that the part of the outer periphery is a region in which a metal film or resist is not formed when a protective film against the etching solution is formed on the front and back surfaces of the quartz wafer in order to form the outer shape of the quartz oscillator, and a part of the quartz wafer is held by the jig for film formation or the jig for resist application.

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