JP5823908B2 - Wafer processing method - Google Patents

Description

  The present invention relates to a wafer processing method for a quartz wafer.

  Vibrating devices using crystal resonators are in widespread use. A vibration device using a crystal resonator is small in size and has stable frequency characteristics with respect to temperature changes, and is widely used as a timing source for portable information terminals such as mobile phones and many other electronic devices. As a resonator element of a crystal resonator, a resonator element using a tuning fork type resonator or a thickness-shear resonator element is used. In recent years, further downsizing, higher frequency, and stabilization of the vibration cycle have been demanded. It has been.

  An AT-cut quartz crystal resonator element has been put to practical use as a resonator element that uses thickness-shear vibration. The AT-cut quartz crystal resonator element has a relationship of t = 1670 / f between the thickness t (m) of the resonator element and the vibration frequency f (Hz). That is, to increase the frequency, the thickness is reduced. Further, in order to improve the quality of the vibration characteristics, it is necessary to form the thickness of the vibrating piece uniformly, and the allowable variation in thickness becomes smaller in inverse proportion to the frequency. For example, if the vibration frequency is 16 MHz, the thickness is 104 μm. If the allowable variation in thickness at this time is δd, the thickness of the vibration piece is 44 μm when the vibration frequency is 38 MHz. The allowable variation in thickness at this time is When the vibration frequency is 50 MHz, the thickness of the resonator element is 33 μm, and the allowable variation in thickness at this time is further reduced to δd / 3.

  Patent Document 1 describes this type of quartz wafer processing method and wafer processing apparatus 111. FIG. 7 shows the wafer processing apparatus 111 described in FIG. 1 of Patent Document 1, which is an apparatus for processing the square wafer stack S into a cylindrical wafer stack. The wafer laminate S is rotatably supported at both ends in the stacking direction by the rotation unit 112 and the fixed unit 113. The rotation unit 112 includes a first fixing jig 123 that supports one end of the wafer stack S, an output shaft 122 that transmits rotation to the first fixing jig 123, and a motor that transmits rotation to the output shaft 122. 121. The fixing unit 113 includes a second fixing jig 133 that supports the other end of the wafer stack S, a centering center part 135 that contacts the second fixing jig 133 and performs centering, and a shaft part 134. A centering part 132 and a fixed base 131 for fixing the centering part 132 are provided. Therefore, the rotation of the motor 121 is transmitted to the wafer stack S and is supported rotatably. Then, the grinding rotary grindstone 114 is installed so as to be movable from the back side to the front side of the paper, and the polishing means 115 having the bowl-shaped flange 151 is installed so as to be movable up and down.

  First, a rectangular plate-shaped quartz wafer is cut out from a rectangular quartz crystal. Next, a large number of rectangular quartz crystal wafers cut out are stacked and bonded to form a rectangular wafer stack S. The wafer laminate S is mounted between the fixed unit 113 and the rotation unit 112, and the wafer laminate S is rotated by the motor 121, and the grinding rotary grindstone 114 is moved from the back side to the front side of the paper surface. Grind S. Further, the wafer stack S is ground and processed into a cylinder while the grinding rotary grindstone 114 is reciprocated in the axial direction of the wafer stack S. Next, the grinding rotary grindstone 114 is retracted to the back side of the drawing. Next, the wafer laminate S is rotated around the cylinder axis, the polishing means 115 is moved upward, the inner surface of the flange 151 is brought into contact with the outer peripheral surface of the wafer laminate S, and the outer peripheral surface is mirror-polished. At the time of polishing, an abrasive such as cerium oxide is supplied to the flange portion 151.

  Next, the cylindrical wafer laminate S is detached from the wafer processing apparatus 111, and the adhesive is dissolved to separate the individual quartz wafers. Next, the quartz wafers are set one by one on the carrier of the double-side polishing machine and ground to the required thickness, and then mirror polishing is performed. Thereafter, driving electrodes are formed on both surfaces of the quartz wafer by sputtering or vapor deposition, electrode patterns are formed by a photo process and an etching method, and the quartz wafer is etched and divided into individual quartz crystal vibrating pieces.

JP 2011-189467 A

  When forming the crystal vibrating piece, it is necessary to manage the crystal orientation of the crystal vibrating piece. For example, the etching rate of a quartz wafer varies depending on the crystal axis direction. For this reason, when a large number of crystal vibrating pieces are formed from one crystal wafer, it is necessary to set the layout of the crystal vibrating pieces based on the crystal orientation of the crystal wafer.

  However, in the wafer processing method described in Patent Document 1, since the quadrangular columnar wafer stack S is processed into a cylinder, a reference plane representing a crystal orientation does not remain in the processed wafer stack S. Therefore, the crystal orientation of the crystal wafer from which the wafer stack S is individually separated becomes unknown. As a method for avoiding this, the wafer laminate S is formed by aligning the crystal orientations of the quartz wafer cut out from the quartz crystal. Then, crystal orientation is imprinted on the wafer or glass at both ends of the wafer laminate S, and an orientation flat representing the crystal orientation is formed on the outer periphery of the wafer laminate S based on the imprint after processing into a cylinder, or a crystal A method of writing a mark indicating the direction can be considered. However, an error occurs between the wafer or glass stamps at both ends and the orientation flats or marks formed on the outer periphery of the cylinder, and it is difficult to accurately display the crystal orientation of each crystal wafer.

  Therefore, when the wafer stack S is processed into a cylindrical shape by the wafer processing apparatus 111, the wafer stack S is decentered from the central axis of the prism and rotated, and a reference for defining a specific side, for example, a crystal axis after grinding. It is conceivable to process the cylinder so that the side remains. However, it is difficult to rotate the wafer stack S by decentering it from the central axis of the wafer stack S.

  In addition, in the case of a rectangular plate-shaped quartz wafer from which a quartz crystal is cut, the crystal orientation is specified by one side of the rectangular shape. In view of this, it is conceivable to grind and polish a rectangular plate-shaped crystal wafer cut out from a raw quartz crystal without processing it into a circular crystal wafer as described in Patent Document 1, using a double-side polishing machine. FIG. 8 is a partial plan view schematically illustrating the double-side polishing machine 100 with the upper polishing surface plate removed. An opening 104 is formed in the carrier 103, and a rectangular plate-shaped crystal wafer U is mounted in each opening 104. For each crystal wafer U, for example, the inner side of the carrier 103 is set as a reference side on which the crystal orientation is determined. The carrier 103 revolves while rotating between the inner sun gear 101 and the outer internal gear 102.

  However, since the carrier 103 revolves while rotating, the traveling distance of the carrier 103 with respect to the upper and lower polishing surface plates is longer on the outer peripheral side than on the center side of the carrier 103. Therefore, the quartz wafer U has a large amount of grinding on the outer peripheral side of the carrier 103 and a small amount of grinding on the center side, and cannot be uniformly ground. On the other hand, if the crystal wafer U is formed in a circular shape and the crystal wafer U is mounted in the circular opening 104 of the carrier 103, the crystal wafer U rotates in the opening 104, and the surface of the crystal wafer U The amount of grinding inside becomes uniform.

  In view of the above problems, the present invention has been made with the object of providing a wafer processing method in which the crystal orientation of a quartz wafer can be specified and grinding can be performed uniformly.

  In the wafer processing method of the present invention, a plurality of the quartz crystal wafers having a reference side and a plurality of the reference sides are aligned and stacked, and a laminate composed of quadrangular columns having a side surface constituted by the reference sides as a reference surface is formed. A stacking step, a mounting step of mounting the laminate on the mounting jig such that corners of adjacent side faces of the quadrangular prism protrude from the outer surface of the mounting jig, and grinding and removing the protruding corners. The grinding step and the chamfering step of chamfering the corners remaining on the outer periphery of the laminate, leaving the reference surface, and processing the laminate into a cylinder having a pseudo-circular cross section are provided.

  Further, the mounting jig has an L shape having an opening window on each side surface, and the mounting step is a step of fixing each of the stacked bodies by projecting each corner from the opening window. It was.

  Further, the mounting jig has an opening window, and the mounting step is a step of fixing the laminated body to the mounting jig by projecting the corner portion from the opening window.

  Further, the grinding step is a step of forming the length of the reference surface around the column axis in the four planes of the side surface of the square column longer than the length of the other plane around the column axis. It was supposed to be.

  In addition, a separation step of separating the laminated body into individual quartz wafers and a polishing step of attaching the separated quartz wafers to a circular opening of a carrier and polishing both sides are provided.

  The quartz wafer is an AT cut quartz wafer.

  The wafer processing method of the present invention is a lamination process in which a plurality of reference sides of a quartz crystal wafer made of a quadrangle having a reference side are aligned and laminated to form a laminate made of a quadrangular column with a side surface constituted by the reference side as a reference surface. A mounting step of mounting the laminate on the mounting jig such that corners of adjacent side faces of the quadrangular prism protrude from the outer surface of the mounting jig, a grinding step of grinding and removing the protruding corners, and a reference surface And chamfering the corners remaining on the outer periphery of the laminated body, and chamfering the laminated body into a cylinder having a pseudo-circular cross section. Thereby, the crystal orientation of the quartz wafer can be specified, and the thickness in the wafer plane can be processed uniformly.

It is process drawing showing the wafer processing method which concerns on the basic composition of this invention. It is a figure for demonstrating the wafer processing method which concerns on embodiment of this invention. It is a figure for demonstrating the wafer processing method which concerns on embodiment of this invention. It is a figure for demonstrating the wafer processing method which concerns on embodiment of this invention. It is a figure for demonstrating the wafer processing method which concerns on embodiment of this invention. It is a figure for demonstrating the wafer processing method which concerns on embodiment of this invention. 1 shows a conventionally known wafer processing apparatus for quartz wafers. It is a partial plane schematic diagram of a conventionally well-known double-side polisher.

(Basic configuration)
FIG. 1 is a process diagram showing a wafer processing method according to the basic configuration of the present invention. First, in the laminating step S1, a plurality of quadrangular quartz crystal wafers having a reference side are aligned and stacked, and a laminate composed of quadrangular columns having a side surface constituted by the reference side as a reference surface is formed. Since the crystal orientation of the single crystal quartz ore is specified, the reference side of the quartz wafer can be easily specified when cutting from the original stone. Next, in the mounting step S2, the stacked body is mounted on the mounting jig so that the corners of the adjacent side surfaces of the quadrangular prism protrude from the outer surface of the mounting jig.

  Next, in the grinding step S3, the corners protruding from the outer surface of the mounting jig are removed by grinding. This is done for the four corners formed by the four side surfaces of the wafer stack. If necessary, the process is performed for eight more corners. Next, in the chamfering step S4, the corners remaining on the outer periphery of the laminated body are chamfered while leaving the reference surface, and the laminated body is processed into a cylinder whose section has a pseudo circle. Next, in the separation step S5, the laminate having a cross section of a pseudo circle is separated into individual quartz wafers. The reference sides that constitute the reference plane of the laminate remain on the individually separated quartz wafers, and the crystal orientation is determined by the reference sides. Next, in the polishing step S6, the quartz wafer is ground to a required thickness and the surface is flattened.

  Thereby, since the reference side remains in each crystal wafer, the crystal orientation can be easily determined. In addition, since the quartz wafer is pseudo-circular, the quartz wafer can be rotatably mounted in the carrier opening of the double-side polishing machine. For this reason, it is possible to perform grinding and polishing with little thickness unevenness in the polishing step S6.

  Thus, according to the wafer processing method of the present invention, each crystal wafer has a pseudo-circular shape, so that the thickness can be uniformly ground and polished by a double-side polishing machine, and the crystal orientation is adjusted to the crystal wafer. It is possible to specify an accurate crystal orientation while leaving a reference side to be expressed. Hereinafter, it demonstrates in detail based on embodiment.

(Embodiment)
2 to 6 are views for explaining the wafer processing method according to the embodiment of the present invention. FIG. 2 is an explanatory diagram of the stacking step S1. FIG. 2A shows a state in which a single crystal quartz ore is cut into a square quartz wafer 1. The quartz crystal is cut into AT cuts with a wire saw to form a quartz wafer 1. The reference side KH of the quartz crystal wafer 1 is formed from the + X plane perpendicular to the x-axis of the raw quartz stone. The quartz wafer 1 has a thickness of 0.1 mm to 0.5 mm and a side of 25 mm to 55 mm. FIG. 2B shows a state in which the crystal wafer 1 is laminated and bonded to form a laminate 2. The laminate 2 has a quadrangular prism shape, and a reference plane KM is formed by the reference side KH of each crystal wafer 1. Dummy glasses 7a and 7b are bonded to both ends of the quadrangular column to protect the surface of the crystal wafer 1 at both ends.

  FIG. 3 is an explanatory diagram of the mounting step S2. FIG. 3A shows a state in which the laminated body 2 is sandwiched between two L-shaped mounting jigs 4a and 4b each having an opening window 8 on each side surface. Each corner 3 is protruded from each opening window 8 of the two mounting jigs 4a and 4b, and the laminate 2 is sandwiched and fixed. FIG. 3B shows a state in which the laminate 2 is mounted on a mounting jig 4c having an opening window 8 at the bottom of a V-shaped groove, unlike the L-shaped mounting jigs 4a and 4b. The laminated body 2 is mounted on the mounting jig 4c with the corner 3 protruding from the opening window 8. One side surface of the outer periphery of the laminate 2 is a reference surface KM, and is marked with ink or the like to distinguish it from the other side surfaces.

  4 and 5 are explanatory diagrams of the grinding step S3 and the chamfering step S4. The first grinding method will be described with reference to FIG. FIG. 4A shows a cross section in a direction perpendicular to the quadrangular prism axis of the laminate 2. One side surface of the stacked body 2 forms a reference surface KM. FIG. 4B shows a state in which the laminate 2 is fixed by being sandwiched between two mounting jigs 4a and 4b. Each corner 3 on the outer surface of the laminate 2 is projected from each opening window 8 of the mounting jigs 4a and 4b. That is, the corners 3 on the adjacent side surfaces of the quadrangular prism laminate 2 are projected from the outer surfaces of the mounting jigs 4a and 4b. FIG. 4C shows a state where the corners 3 protruding from the respective opening windows 8 of the mounting jigs 4a and 4b are ground to the outer surfaces of the mounting jigs 4a and 4b and deleted. FIG. 4D shows a cross section of the laminate 2 from which the laminate 2 has been removed from the mounting jigs 4a and 4b. The laminate 2 is an octagonal column, and one side of the laminate 2 forms a reference plane KM.

  FIG. 4E shows a cross section obtained by further grinding and removing each corner portion 9 on the adjacent side surface of the laminate 2 composed of octagonal columns. Similarly to the case shown in FIG. 4 (b), the corner portion 9 of the laminate 2 is projected from the opening window 8 of the L-shaped mounting jigs 4a and 4b, and this protruding portion is pressed against a grinding surface plate for grinding. It removes and the laminated body 2 is processed into a hexagonal prism. In this case, in order to make the reference surface KM have a predetermined length, the grinding amount of both corners sandwiching the reference surface KM is adjusted.

  FIG. 4F shows a cross section of the laminate 2 after the chamfering step S4. The corners of the outer periphery of the laminate 2 are chamfered except for both corners of the reference surface KM, and the cross section is made a pseudo circle. Next, in the separation step S <b> 5, the adhesive is dissolved and separated into individual crystal wafers 1. Each crystal wafer has a pseudo-circular shape, and a part of the reference surface KM is left on the outer periphery. A part of the remaining reference surface KM is a part of the reference side KH in one crystal wafer, and this becomes an orientation flat. Therefore, the crystal orientation of each quartz wafer can be accurately specified by this orientation flat. Note that the chamfering step S4 may be performed after the octagonal column without grinding the quadrangular laminate 2 to the hexagonal column. In the present embodiment, the AT-cut quartz wafer has been described. However, the present invention is not limited to this, and may be, for example, a BT-cut, or may be applied to a quartz wafer cut out by other cuts. Needless to say, you can.

  The second grinding method will be described with reference to FIG. FIG. 5A shows a cross section of the laminate 2. One side of the quadrangle is a reference plane KM. FIG. 5B shows a state in which the laminate 2 is fixed by being sandwiched between two mounting jigs 4a and 4b. Here, for convenience of explanation, the respective opening windows 8 of the two mounting jigs 4a and 4b are referred to as opening windows 8a, 8b, 8c and 8d counterclockwise from the lower surface side. The mounting jig 4a is formed by moving the opening window 8d upward so that the opening diameter is enlarged, and the opening window 8a is formed by moving the opening window 8d to the left so that the opening diameter is smaller than that of the opening window 8d. Similarly, the mounting jig 4b is formed by moving the opening window 8c to the left so that the opening diameter is enlarged, and the opening window 8b is formed by moving upward so that the opening diameter is smaller than the opening window 8c. . Thereby, the laminated body 2 is fixed in the -x direction with respect to the center P of the mounting jigs 4a and 4b.

  FIG.5 (c) represents the state which grinded and removed each corner | angular part 3 which protrudes from the opening windows 8a-8d. The quadrangular prism laminate 2 was fixed to the center P of the mounting jigs 4a and 4b in the 10:30 direction (−x direction). As a result, among the eight side surfaces of the octagonal column from which the corner portion 3 has been removed by grinding, the length in the direction around the axis of the octagonal column is the longest reference surface KM located in the 4:30 direction (+ x direction). Accordingly, in the subsequent grinding step S3 and chamfering step S4, even when the mark such as ink attached to the reference surface KM is peeled off, the reference surface KM can be easily confirmed.

  FIG.5 (d) represents the cross section which removed the laminated body 2 from mounting jig 4a, 4b. The side surface with the longest length in the direction around the axis of the octagonal prism is the reference surface KM. FIG. 5 (e) shows a cross section obtained by further grinding and removing each corner of the octagonal prism laminate 2. FIG. 5F shows a cross section of the laminate 2 after the chamfering step S4. The corners of the outer periphery of the laminate 2 are chamfered except for both corners of the reference surface KM, and the cross section is made a pseudo circle.

  Next, in the separation step S <b> 5, the adhesive is dissolved and separated into individual crystal wafers 1. Each crystal wafer 1 has a pseudo-circular shape, and a part of the reference surface KM is left on the outer periphery. A part of the remaining reference surface KM is a part of the reference side KH in one crystal wafer, and this becomes an orientation flat of the crystal wafer. With this orientation flat, the crystal orientation can be specified accurately.

  FIG. 6 is a diagram for explaining the polishing step S6, and is a schematic partial plan view of the double-side polishing machine 10 with the upper polishing platen removed. The carrier 13 is meshed between the inner sun gear 11 and the outer internal gear 12. A plurality of circular openings 14 are formed in the carrier 13, and the crystal wafer 1 is inserted into the openings 14. An orientation flat 6 is formed on the outer periphery of the quartz wafer 1. The carrier 13 is formed thinner than the target thickness of the quartz wafer 1. The carrier 13 and the quartz wafer 1 are sandwiched between upper and lower polishing surface plates (not shown) and revolve around the sun gear 11 while rotating. Abrasive grains are supplied to the polishing surface plate and polished to a predetermined thickness. Since the quartz wafer 1 rotates within the opening 14, it is possible to polish the thickness unevenness with a small amount.

DESCRIPTION OF SYMBOLS 1 Quartz wafer 2 Laminated body 3 Corner | angular part 4, 4a, 4b, 4c Mounting jig 6 Orientation flat 7a, 7b Dummy glass 8, 8a, 8b, 8c, 8d Opening window 9 Corner | angular part 10 Double-side polisher KH Reference | standard side KM Reference | standard surface

Claims (6)

Laminating step of aligning a plurality of the reference sides of a quartz crystal wafer made of a quadrangle having a reference side, and forming a laminate made of a quadrangular prism having a side surface constituted by the reference side as a reference surface;
A mounting step of mounting the laminate on the mounting jig such that corners of adjacent side surfaces of the quadrangular prism protrude from the outer surface of the mounting jig;
A grinding step of grinding and removing the protruding corners;
A wafer processing method comprising: a chamfering step of chamfering corner portions remaining on the outer periphery of the stacked body while leaving the reference surface, and processing the stacked body into a cylinder having a pseudo-circular cross section. The mounting jig has an L shape having an opening window on each side surface,
2. The wafer processing method according to claim 1, wherein the attaching step is a step of fixing each of the stacked bodies by protruding each corner from the opening window. The mounting jig has an opening window,
2. The wafer processing method according to claim 1, wherein the mounting step is a step of fixing the stacked body to the mounting jig by causing the corner portion to protrude from the opening window.   The grinding step is a step of forming, in the four planes on the side surface of the quadrangular column, the length of the reference plane in the direction around the column axis to be longer than the length of the other plane in the direction around the column axis. Item 4. The wafer processing method according to any one of Items 1 to 3. A separation step of separating the laminate into individual quartz wafers;
A wafer processing method according to any one of claims 1 to 4, further comprising: a polishing step in which the separated crystal wafer is mounted on a circular opening of a carrier and polished on both sides.   The wafer processing method according to claim 1, wherein the quartz wafer is an AT-cut quartz wafer.

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