JP2020038903A - Separation method for wafer - Google Patents

Abstract

To separate a wafer by finding a depth in which a sound pressure becomes maximum in a liquid and applying maximum ultrasonic vibration to a release layer in a method for separating an ingot by applying ultrasonic vibration.SOLUTION: The present invention relates to a method for separating a wafer from an ingot I with a release layer M defined as a border by immersing the ingot I in which the release layer M is formed planar at a position corresponding to a thickness T of the wafer that should be generated from an end face Ia of the ingot I, in a liquid L within a liquid tank 59, and applying ultrasonic vibration which is oscillated from the ultrasonic diaphragm 53 and propagated to the liquid L, to the release layer M. The separation method for the wafer includes: a liquid supply step of storing the liquid L in the liquid tank 59; a step of oscillating the ultrasonic vibration to be propagated in the liquid L from the ultrasonic diaphragm 53, and using a piezoelectric element 112 to detect a depth Z1 in which a sound pressure becomes maximum in a depth direction of the liquid L; and a step of positioning the release layer M of the ingot I in the depth which is detected in the position detection step, and separating the wafer from the ingot I with the release layer M defined as the border.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a method for separating a wafer from an ingot.

  Conventionally, a wafer is used to form a planar release layer on an ingot by laser beam irradiation, and then immerse the ingot in a liquid tank and apply ultrasonic vibration to the release layer via a liquid (water) to separate the wafer. (For example, see Patent Document 1).

JP 2018-093106 A

  In applying the ultrasonic vibration to the peeling layer, the ultrasonic vibration is oscillated from an ultrasonic vibration plate disposed on the lower surface side of the liquid tank, and the ultrasonic vibration is propagated to the liquid in the liquid tank. The ultrasonic vibration propagated to the liquid has a place where the sound pressure is large and a place where the sound pressure is small at the depth of the liquid. In the related art, it has been difficult to find a depth at which the sound pressure is large, to position a peeling layer of the ingot at the depth, and to efficiently separate the wafer from the ingot.

  Therefore, in the wafer separation method of separating the wafer from the ingot by applying ultrasonic vibration, the depth at which the sound pressure becomes maximum in the liquid is found, and the wafer is applied by applying the maximum ultrasonic vibration to the release layer. There is a problem of efficient separation.

  The present invention for solving the above-described problems is directed to submerging an ingot in which a release layer is formed in a plane at a position corresponding to the thickness of a wafer to be generated from an end face of the ingot in a liquid in a liquid tank, and an ultrasonic vibration plate. A method of separating the wafer from an ingot by applying ultrasonic vibration oscillated from the liquid and propagating to the liquid to the separation layer, and separating the wafer from the ingot at the separation layer. A position detecting step of oscillating ultrasonic vibration propagating through the liquid from the ultrasonic vibration plate and detecting a depth at which a maximum sound pressure is obtained in a depth direction of the liquid using a piezoelectric element; A separation step of positioning the release layer of the ingot at the depth detected in the detection step and separating the wafer from the ingot with the release layer as a boundary.

  In addition, the present invention for solving the above-mentioned problem is that an ingot having a planar release layer formed at a position corresponding to the thickness of a wafer to be generated from an end face of the ingot is arranged in a liquid tank, and the liquid is placed in the liquid tank. Is supplied to immerse the ingot, the ultrasonic wave is oscillated from the ultrasonic vibration plate, and the ultrasonic vibration that propagates the liquid is applied to the release layer, and the wafer is separated from the ingot at the release layer. A method for separating a wafer, comprising: providing a liquid tank with an ingot with the release layer side facing upward; and providing a piezoelectric element on an upper surface of the ingot; Ultrasonic vibration is oscillated from the plate and the liquid is supplied to the liquid tank to raise the liquid level. When the sound pressure of the ultrasonic wave received by the immersed piezoelectric element on the ingot becomes maximum, the liquid is supplied. Stop the liquid supply A step, after the liquid supplying step, a separation step of the wafer separated from the ingot bordering the release layer is a wafer separation methods consisting of.

  In the method for separating a wafer according to the present invention, the liquid supply step of storing the liquid in the liquid tank and the oscillation of the ultrasonic vibration that propagates the liquid from the ultrasonic vibration plate are oscillated, and the depth at which the maximum sound pressure is obtained in the depth direction of the liquid A position detection step of detecting the position using a piezoelectric element, and a separation step of separating the wafer from the ingot with the separation layer positioned at the separation layer of the ingot at the depth detected in the position detection step, It is possible to efficiently separate the wafer from the ingot by applying the largest ultrasonic vibration to the release layer.

  Further, in the method for separating a wafer according to the present invention, a preparatory step of disposing an ingot in a liquid tank with a release layer side facing upward and a piezoelectric element disposed on an upper surface of the ingot; A liquid that oscillates ultrasonic vibrations from the plate, supplies liquid to the liquid tank, raises the liquid level, and stops liquid supply when the sound pressure of the ultrasonic waves received by the immersed piezoelectric element on the ingot becomes maximum. After the supply step and the liquid supply step, there is a separation step to separate the wafer from the ingot at the separation layer, so that the largest ultrasonic vibration can be applied to the separation layer and the wafer can be separated from the ingot efficiently. Becomes

It is a perspective view explaining the state where the release layer is formed in the ingot. It is sectional drawing explaining the state which has formed the peeling layer in an ingot. FIG. 6 is a cross-sectional view illustrating a state in which the depth at which the maximum sound pressure is obtained in the depth direction of the liquid is detected using the piezoelectric element in the method for separating a wafer according to the first embodiment. It is sectional drawing which shows an example of an ultrasonic sound pressure meter. FIG. 9 is a cross-sectional view illustrating a state in which a release layer of the ingot is positioned at the depth detected in the position detection step and the wafer is separated from the ingot at the release layer. FIG. 9 is a cross-sectional view for describing a liquid supply step, a position detection step, and a separation step in the wafer separation method according to the second embodiment. FIG. 10 is a cross-sectional view for explaining a liquid supply step, a position detection step, and a separation step in the wafer separation method according to the third embodiment. FIG. 13 is a cross-sectional view for explaining a liquid supply step and a position detection step in the wafer separation method according to the fourth embodiment. FIG. 13 is a cross-sectional view for explaining a separation step in the wafer separation method according to the fourth embodiment. FIG. 15 is a cross-sectional view for describing a preparation step in the wafer separation method of the fifth embodiment. FIG. 14 is a cross-sectional view for describing a liquid supply step and a separation step in a wafer separation method according to a fifth embodiment.

  The ingot I shown in FIGS. 1 and 2 is, for example, a cylindrical Si single crystal ingot, a SiC single crystal ingot, a GaN single crystal ingot, or the like, and has a circular first surface Ia as an upper end surface and a first surface Ia. And a cylindrical outer surface Ic located between the first surface Ia and the second surface Ib, the second surface Ib having a circular shape which is located on the opposite side of the first surface Ia and is substantially parallel to the first surface Ia. And The first surface Ia of the ingot I is polished to a mirror surface to serve as a laser beam irradiation surface. For example, in the ingot I, the separation plane direction is set based on the vertical (Z-axis) crystal axis and the horizontal crystal axis detected using X-ray diffraction or the like.

Hereinafter, a brief description will be given of a case where a release layer is formed in a plane at a position corresponding to the thickness T of a wafer to be generated from the first surface Ia of the ingot I.
As shown in FIGS. 1 and 2, the focal point FP of the laser beam LB irradiated from the laser beam irradiation head 30 is positioned at a predetermined height inside the ingot I held by the chuck table 31, The ingot I is irradiated with a laser beam LB having a wavelength having transparency to the first surface Ia of the ingot I which is a flat surface, and a modified region serving as a starting point of separation is formed inside the ingot I.

For example, while irradiating the first surface Ia of the ingot I with the laser beam LB, the ingot I held by the chuck table 31 is processed and fed at a predetermined processing feed speed in the X-axis direction, and separated into the ingot I. The modified region as a starting point is formed in a linear shape extending in the X-axis direction. Further, after the chuck table 31 holding the ingot I is indexed and fed in the Y-axis direction, the same irradiation of the laser beam LB is performed, so that the ingot I includes the modified region and extends along the separation surface direction. The release layer M is formed. The release layer M is formed, for example, substantially parallel to the first surface Ia and the second surface Ib, and has a lower strength than other regions in the ingot I.
The formation of the release layer M is not limited to this example.

(Embodiment 1 of wafer separation method)
Hereinafter, the wafer separation method according to the present invention (referred to as the wafer separation method of the first embodiment) is performed, and the wafer to be generated from the end surface (first surface Ia) of the ingot I shown in FIG. Each step of separating a wafer from an ingot I having a planar release layer M at a position corresponding to the thickness T will be described.

(1) Liquid Supply Step The ingot I is transported, for example, to the wafer separation apparatus 5 shown in FIG. The liquid tank 59 of the wafer separation apparatus 5 shown in FIG. 3 includes a side wall 51 and a bottom plate 50 integrally connected to a lower portion of the side wall 51. An ultrasonic vibration plate 53 is provided on the lower surface of the bottom plate 50 of the liquid tank 59. The ultrasonic vibration plate 53 may be provided in the liquid tank 59. A terminal (not shown) is connected to the ultrasonic vibration plate 53, and a power supply 55 for applying an AC voltage to supply the high-frequency power to the ultrasonic vibration plate 53 via the terminal and the wiring 54 is connected.

In the liquid tank 59, a liquid supply means 57 for supplying the liquid L (water) into the liquid tank 59 is provided. The liquid supply means 57 includes, for example, a supply pipe 571 for supplying the liquid L into the liquid tank 59, and the supply pipe 571 communicates with a liquid supply source 570 such as a pump via an opening / closing valve 572. .
The liquid L (water) is supplied from the liquid supply source 570 to the supply pipe 571, and the liquid L is accumulated in the liquid tank 59. Then, the liquid supply step is completed by the liquid L being accumulated in the liquid tank 59 until the liquid L reaches a predetermined water level.

(2) Position Detection Step The ultrasonic sound pressure gauge 1 shown in FIG. 3 is provided with a rod 10 made of a metal such as SUS or a hard plastic or the like and extending a predetermined length in the Z-axis direction. The shape of the rod 10 may be cylindrical or prismatic.
On the side surface 10a in the longitudinal direction (Z-axis direction) of the rod 10, a detection unit 11 capable of measuring the sound pressure of ultrasonic vibration propagating to the liquid L (water) accumulated in the liquid tank 59 of the wafer separation device 5 is provided. However, a plurality (for example, 11 in FIG. 3) are arranged in the longitudinal direction.

  The detection unit 11 includes a vibration insulator 111 disposed on the side surface 10 a side of the rod 10, a piezoelectric element 112 supported by the vibration insulator 111, and a vibration receiving plate 113 that is in close contact with the piezoelectric element 112.

  For example, the plate-shaped vibration insulator 111 is made of a material (rubber, urethane, or the like) that absorbs vibration, and is fixed to the side surface 10a of the rod 10 with an adhesive member (not shown) or the like. The piezoelectric element 112 is fixed on the vibration insulator 111 with an adhesive member (not shown), and the vibration receiving plate 113 is fixed on the piezoelectric element 112 with an adhesive member (not shown). Generally, measurement of sound pressure by an ultrasonic sound pressure meter is realized by sealing one surface of a piezoelectric element and applying sound pressure to the other surface. Also in the ultrasonic sound pressure gauge 1 according to the present invention, one surface (the surface on the −X direction side) of the piezoelectric element 112 is sealed by the vibration insulator 111 so that ultrasonic vibration is not transmitted from the rod 10. The other surface (the surface on the + X direction side) of the piezoelectric element 112 is configured to transmit ultrasonic vibration via the vibration receiving plate 113.

For example, the piezoelectric element 112 formed in a plate shape is made of quartz, ceramics, or the like, and is electrically connected to the inside of the rod 10 and the wiring 12 passed through the vibration insulator 111. Although the wiring 12 shown by a broken line in FIG. 1 is shown to be branched from one wiring 12 and connected to each of the piezoelectric elements 112, actually, separate independent measuring circuits are provided for each of the piezoelectric elements 112. Eleven wires 12 are electrically connected individually. Each of the wirings 12 individually connected to each of the piezoelectric elements 112 is individually connected to a water depth judging means 19 for judging a water depth at which the ultrasonic vibration becomes maximum.
For example, the vibration receiving plate 113 formed in a plate shape and in close contact with the piezoelectric element 112 is made of a predetermined metal (for example, copper or nickel), and serves as an amplifier that amplifies the received ultrasonic vibration and transmits the amplified ultrasonic vibration to the piezoelectric element 112. Fulfill.

  The ultrasonic sound pressure gauge used in this step may be, for example, the ultrasonic sound pressure meter 1A shown in FIG. The ultrasonic sound pressure meter 1A shown in FIG. 4 is another form of the ultrasonic sound pressure meter 1 shown in FIG. 3, and a plurality of (for example, 11) wirings 12 are passed through like the ultrasonic sound pressure meter 1. It includes a rod 10, a piezoelectric element 112 constituting the detection unit 15, and a vibration receiving plate 113. In FIG. 4, for example, a total of 11 detectors 15 are arranged on the side surface 10a of the rod 10 in the longitudinal direction (Z-axis direction).

  The side surface 10a of the rod 10 is cut out stepwise from the side surface 10a toward the inner side. For example, a first chamber 114 into which a vibration insulator 116 formed in an annular shape is fitted, and a first chamber 114 A plurality of second chambers 115 are provided along the longitudinal direction of the rod 10 so as to be located on the inner side of the rod 10 and large enough to allow the piezoelectric element 112 to expand and contract.

  An annular vibration insulator 116 fitted into the first chamber 114 is fixed to the rod 10 with an adhesive member or the like (not shown), and a plate-like vibration receiving plate 113 is fitted into an opening on the inside thereof. Adhered and fixed in shape. That is, the vibration receiving plate 113 is supported on the side surface 10 a of the rod 10 by the vibration insulator 116.

The piezoelectric element 112 housed in the second room 115 is bonded and fixed to the vibration receiving plate 113, and is supported by the vibration insulator 116 via the vibration receiving plate 113. Independent wirings 12 are electrically connected to the respective piezoelectric elements 112. Each of the wirings 12 is individually connected to a water depth judging means 19 for judging the water depth at which the ultrasonic vibration becomes maximum.
Generally, measurement of sound pressure by an ultrasonic sound pressure meter is realized by sealing one surface of a piezoelectric element and applying sound pressure to the other surface. Also in the ultrasonic sound pressure meter 1A, one surface (the surface on the −X direction side) of the piezoelectric element 112 is not in contact with the rod 10, so that ultrasonic vibration is not transmitted from the rod 10. The other surface (the surface on the + X side) of the piezoelectric element 112 is configured to transmit ultrasonic vibration via the vibration receiving plate 113.

As shown in FIG. 3, in the position detection step, the ultrasonic sound pressure gauge 1 is inserted into the liquid L of the liquid tank 59 from above, and, for example, the detection unit 11 is configured to detect the liquid from slightly above the bottom plate 50 of the liquid tank 59. A plurality of surfaces are arranged in the Z-axis direction up to the plane.
A high frequency power is supplied at a predetermined output from the power supply 55 to the ultrasonic vibration plate 53, and the ultrasonic vibration plate 53 converts the high frequency power into mechanical vibration mainly in a vertical direction, so that a predetermined vibration frequency is obtained. Oscillates ultrasonic waves. Then, the oscillated ultrasonic waves propagate to the liquid L via the bottom plate 50 of the liquid tank 59.
The ultrasonic vibration propagated to the liquid L advances toward the liquid surface in the + Z direction (vertical direction), reaches the liquid surface, is totally reflected by the liquid surface, and returns to the bottom plate 50 side. As a result, the ultrasonic waves (incident waves) traveling toward the liquid surface and the ultrasonic waves (reflected waves) reflected from the liquid surface and returning to the bottom plate 50 overlap each other, and the depth of the sound pressure is high and low in the liquid L. And arise. Note that, depending on the frequency of the ultrasonic wave, the depth at which the sound pressure is highest in the liquid L exists at a constant interval in the Z-axis direction from the bottom plate 50 that is the vibration surface.

  In the liquid L, each vibration receiving plate 113 receives ultrasonic vibration from the liquid L, and the ultrasonic vibration is further transmitted to each piezoelectric element 112. Then, each piezoelectric element 112 takes out an electric output proportional to the sound pressure, converts it into a voltage, and sends the voltage signal to the water depth judging means 19 through the wiring 12. The water depth judging means 19, which monitors the voltage signals individually sent from the respective piezoelectric elements 112, sets the height position of the piezoelectric element 112, which has sent the largest voltage signal, on the rod 10, that is, the liquid level to 0, for example. By specifying the depth Z1 from the liquid level in the case of the position, the depth Z1 in the liquid L at which the sound pressure becomes maximum in the Z-axis direction is measured. The depth at which the sound pressure in the liquid L is maximized in the Z-axis direction is not limited to one, and may be plural.

(3) Separation Step As shown in FIG. 5, the wafer separation apparatus 5 includes an ingot holding means 60 for holding the ingot I. The ingot holding means 60 includes, for example, a suction pad 600 that suctions and holds the ingot I on its lower surface (suction surface), and an arm 601 that supports the suction pad 600 and is connected to the lifting / lowering means 61. Note that the ingot holding means 60 is not limited to this example, and may be configured by a clamp or the like that clamps the outer surface Ic of the ingot I. As shown in FIG. 5, the second surface Ib of the ingot I is sucked and held by the ingot holding means 60, so that the first surface Ia of the ingot I faces downward.
The elevating means 61 for elevating and lowering the ingot holding means 60 in the vertical direction (Z-axis direction) is a mechanism including, for example, an electric cylinder or a motor and a ball screw.

  As shown in FIG. 5, the wafer separation apparatus 5 includes control means 9 for controlling the entire apparatus. The control means 9 including a CPU and a storage element such as a memory is electrically connected to the water depth judging means 19 and the elevating means 61. After the information is transmitted from the water depth judging means 19 to the control means 9, Under the control means 9, the raising / lowering operation of the ingot holding means 60 holding the ingot I by the raising / lowering means 61 is controlled.

  The water depth judging means 19 transmits to the control means 9 information about the depth Z1 at which the sound pressure becomes maximum in the Z-axis direction in the liquid L. Then, for example, the ingot holding means 60 for holding the ingot I is sent in the −Z direction by the elevating means 61, and under the control of the elevating means 61 by the control means 9, the first surface Ia of the ingot I At the height of From this state, under the control of the elevating means 61 by the control means 9, the elevating means 61 further lowers the ingot holding means 60 in the -Z direction by a distance obtained by adding the thickness T of the wafer to be generated to the depth Z1. . Thereby, the release layer M of the ingot I is positioned at the depth Z1 detected in the position detection step.

Then, the largest ultrasonic vibration is applied to the peeling layer M in the ingot I located at the depth Z1 where the sound pressure becomes largest in the Z-axis direction in the liquid L, and the wafer is moved from the ingot I at the border of the peeling layer M. Separated.
By lowering the ingot I into the liquid L in the separation step, the depth Z1 at which the sound pressure becomes maximum in the Z-axis direction in the liquid L may slightly change upward or downward. . In this case, after the information sent from the water depth judging means 19 is placed under the control of the control means 9, the exfoliation layer M of the ingot I is positioned at the depth Z1 detected in the position detecting step, and then moved up and down. The means 61 may further slightly move the ingot holding means 60 upward or downward so as to follow the change.

(Embodiment 2 of wafer separation method)
Hereinafter, the wafer separation method according to the present invention (referred to as the wafer separation method of Embodiment 2) will be described, and the wafer to be generated from the end surface (first surface Ia) of the ingot I shown in FIG. Each step of separating a wafer from an ingot I having a planar release layer M at a position corresponding to the thickness T will be described.

(1) Liquid Supply Step The wafer separation apparatus 5A shown in FIG. 6 is a modification of the wafer separation apparatus 5 shown in FIG. In the wafer separating apparatus 5A, an ultrasonic vibration plate 53 connected to a power source 55 via a wiring 54 is disposed above a liquid tank 59.
A table 56 on which the ingot I is placed is disposed on the bottom plate 50 of the liquid tank 59, and the table 56 can be moved up and down in the Z-axis direction by table elevating means 58. For example, the table lifting / lowering means 58 includes a lifting / lowering shaft 581 that is inserted into the bottom plate 50 via a seal ring 580 and a bearing (not shown) so as to be movable up and down, and is connected to the lower surface of the table 56, and a driving source such as a motor that raises / lowers the lifting / lowering shaft 581. 582. The table elevating means 58 is not limited to this configuration.

  As shown in FIG. 6, the wafer separation apparatus 5A includes control means 9 for controlling the entire apparatus. The control means 9 is electrically connected to the water depth determination means 19 and the table elevating means 58 connected to the ultrasonic sound pressure gauge 1 shown in FIG. 6, and information is transmitted from the water depth determination means 19 to the control means 9. Thereafter, under the control means 9, the lifting operation of the table 56 on which the ingot I is placed by the table lifting means 58 is controlled.

In this step, the ingot I is transferred to the wafer separation device 5A shown in FIG. Then, the ingot I is placed on the table 56, for example, with the first surface Ia facing upward.
The liquid L is supplied from the liquid supply source 570 to the supply pipe 571, and the liquid L is accumulated in the liquid tank 59. Then, the liquid supply step is completed by the liquid L being accumulated in the liquid tank 59 until the liquid L reaches a predetermined water level. Further, the lower surface side of the ultrasonic vibration plate 53 is in a state of being immersed in the liquid L.

(2) Position Detection Step In the position detection step, the ultrasonic sound pressure gauge 1 is inserted into the liquid L in the liquid tank 59, and the detection unit 11 is moved from slightly above the bottom plate 50 of the liquid tank 59 to the liquid surface in the Z-axis direction. Will be in a state of being plurally arranged. In addition, high frequency power is supplied from the power supply 55 to the ultrasonic vibration plate 53 at a predetermined output, and the ultrasonic vibration plate 53 oscillates ultrasonic waves having a predetermined vibration frequency, and the ultrasonic waves are applied to the liquid L in the liquid tank 59. Propagate.
The ultrasonic vibration propagated to the liquid L proceeds in the −Z direction toward the bottom plate 50 side of the liquid tank 59, reaches the bottom plate 50 and the first surface Ia of the ingot I, is totally reflected, and returns to the liquid surface. come. As a result, the incident wave and the reflected wave overlap each other, and a deep sound pressure and a weak sound pressure are generated in the liquid L. Note that, depending on the frequency of the ultrasonic wave, the depth at which the sound pressure is highest in the liquid L exists at a constant interval in the Z-axis direction from the lower surface of the ultrasonic vibration plate 53 that is the vibration surface.

  In the liquid L, each vibration receiving plate 113 receives ultrasonic vibration from the liquid L, and the ultrasonic vibration is transmitted to each piezoelectric element 112. Then, each piezoelectric element 112 sends a voltage signal proportional to the sound pressure to the water depth judging means 19. The height position of the piezoelectric element 112, which has sent the largest voltage signal, on the rod 10, ie, in the liquid L, is determined by the water depth judging means 19 which monitors the voltage signal individually sent from each piezoelectric element 112. The depth Z2 at which the sound pressure becomes maximum in the Z-axis direction is measured. The depth at which the sound pressure in the liquid L is maximized in the Z-axis direction is not limited to one, and may be plural.

(3) Separation Step The water depth judging means 19 transmits to the control means 9 information on the depth Z2 in the liquid L at which the sound pressure becomes maximum in the Z-axis direction.
Here, the thickness of the ingot I is known information, and the position of the release layer M in the thickness direction (Z-axis direction) of the ingot I is also known information. Therefore, for example, the information on the height position in the Z-axis direction of the release layer M of the ingot I when the table 56 is on the bottom plate 50 of the liquid tank 59 at the origin position is grasped by the control means 9 in advance. Then, under the control of the table elevating means 58 by the control means 9, the table elevating means 58 elevates the table 56 at the origin position by a predetermined distance in the + Z direction. Thus, the release layer M of the ingot I is positioned at the depth Z2 detected in the position detection step.

Then, the largest ultrasonic vibration is applied to the release layer M in the ingot I located at the depth Z2 where the sound pressure becomes maximum in the Z-axis direction in the liquid L, and the wafer W is moved from the ingot I to the release layer M as a boundary. Are separated.
Note that, for example, by raising the ingot I in the liquid L in the separation step, the depth Z2 at which the sound pressure becomes largest in the Z-axis direction in the liquid L may slightly change upward or downward. is there. In this case, the information sent from the water depth judging means 19 is placed below, and under the control of the control means 9, the exfoliation layer M of the ingot I is positioned at the depth Z2 detected in the position detecting step. The elevating means 58 may further slightly move the table 56 upward or downward so as to follow the change.

(Embodiment 3 of wafer separation method)
Hereinafter, the wafer separating method according to the present invention (referred to as the wafer separating method of the third embodiment) is performed, and the wafer to be generated from the end surface (first surface Ia) of the ingot I shown in FIG. Each step of separating a wafer from an ingot I having a planar release layer M at a position corresponding to the thickness T will be described. In the wafer separation method according to the present embodiment, the following (1) liquid supply step, (2) position detection step, and (3) separation step are performed, for example, in parallel.

(1) Liquid Supply Step In the present embodiment, the ingot I is transported, for example, to the wafer separation apparatus 5B shown in FIG.
The wafer separation apparatus 5B shown in FIG. 7 is a modification of the wafer separation apparatus 5A shown in FIG. 6 and is different from the wafer separation apparatus 5A in that the wafer separation apparatus 5B does not include the table 56 and the table elevating means 58 shown in FIG. It has a configuration.
As shown in FIG. 7, the wafer separation apparatus 5B includes control means 9 for controlling the entire apparatus. The control means 9 is electrically connected, for example, to the water depth determination means 19 connected to the ultrasonic sound pressure gauge 1 shown in FIG. After the information is transmitted from the means 19 to the control means 9, the opening / closing operation of the opening / closing valve 572 is controlled under the control means 9.

  The ingot I is placed, for example, on the bottom plate 50 of the liquid tank 59 with the first surface Ia facing upward. In addition, the ultrasonic sound pressure gauge 1 is inserted into the liquid L in the liquid tank 59, and a plurality of the detecting units 11 are arranged in the Z-axis direction from slightly above the bottom plate 50 of the liquid tank 59 to the liquid surface. Here, the thickness of the ingot I is known information, and the position of the release layer M in the thickness direction (Z-axis direction) of the ingot I is also known information. Then, information on the height position in the Z-axis direction of the peeling layer M of the ingot I placed on the bottom plate 50, and the ultrasonic sound pressure meter corresponding to the height position in the Z-axis direction of the peeling layer M of the ingot I Information about the depth position Z3 of one piezoelectric element 112 is stored in the control means 9 in advance.

  Then, under the control of the control means 9, the open / close valve 572 of the liquid supply means 57 is opened, and the liquid L (water) is supplied from the liquid supply source 570 to the supply pipe 571, and The liquid L is accumulated.

(2) Position Detection Step A high frequency power is supplied at a predetermined output from the power supply 55 to the ultrasonic vibration plate 53, and the ultrasonic vibration plate 53 oscillates an ultrasonic wave having a predetermined vibration frequency. To the liquid L. Then, the incident wave and the reflected wave overlap in the liquid L, and a strong sound pressure depth and a weak sound pressure depth are generated in the liquid L.

  In the liquid L, the ultrasonic vibration is transmitted to each piezoelectric element 112 via each vibration receiving plate 113. Then, each piezoelectric element 112 sends a voltage signal proportional to the sound pressure to the water depth judging means 19. The water depth judging means 19 starts monitoring, for example, a voltage signal sent from the piezoelectric element 112 located at the depth position Z3 in each piezoelectric element 112.

(3) Separation Step The liquid L is supplied from the liquid supply source 570 to the supply pipe 571, and the liquid L is accumulated in the liquid tank 59 and the liquid level rises. Then, when the voltage signal transmitted from the piezoelectric element 112 located at the monitored depth position Z3 becomes maximum, the water depth determining means 19 reduces the sound pressure of the ultrasonic wave received by the piezoelectric element 112. The control unit 9 is notified of the information indicating that it has become the largest.
Then, under the control of the control means 9, the open / close valve 572 of the liquid supply means 57 is closed. As a result, the release layer M of the ingot I is positioned at a depth Z3 where the sound pressure is maximized in the Z-axis direction in the liquid L.
In addition, for example, when the depth at which the maximum sound pressure in the liquid L is obtained is not known after performing the respective steps as described above, once the liquid L is filled in the liquid tank 59, the supply of the liquid L is stopped. After that, while the drain valve 591 shown in FIG. 7 is opened to drain the liquid from the drain port 590 of the liquid tank 59, the ultrasonic sound pressure meter 1 also uses the measurement data acquired when the liquid L is supplied. May be measured, and the peeling layer M of the ingot I may be positioned at the water depth at which the maximum sound pressure is reached.

  Then, the largest ultrasonic vibration is applied to the release layer M in the ingot I located at the depth Z3 where the sound pressure becomes maximum in the Z-axis direction in the liquid L, and the wafer W Are separated.

(Embodiment 4 of wafer separation method)
In the following, the wafer separation method according to the present invention (referred to as the wafer separation method of Embodiment 4) is carried out, and the wafer to be generated from the end surface (first surface Ia) of ingot I shown in FIG. Each step of separating a wafer from an ingot I having a planar release layer M at a position corresponding to the thickness T will be described.

(1) Liquid Supply Step In the present embodiment, the ingot I is transported, for example, to the wafer separation apparatus 5C shown in FIG. Further, the liquid L (water) is supplied from the liquid supply source 570 to the supply pipe 571, and the liquid L is accumulated in the liquid tank 59. Then, the liquid supply step is completed by the liquid L being accumulated in the liquid tank 59 until the liquid L reaches a predetermined water level.

(2) Position Detection Step In the present embodiment, the ultrasonic sound pressure meter 2 shown in FIG. 8 is used to detect the depth at which the liquid L has the largest sound pressure in the depth direction (Z-axis direction). The ultrasonic sound pressure gauge 2 includes a detection unit 21 at the end of a rod-shaped main body 20 extending in the Z-axis direction.

  The bottom surface of the main body 20 is notched in a stepwise upward direction. For example, a first room 201 into which the vibration insulator 211 formed in an annular shape is fitted, and the main body 20 is larger than the first room 201. A second room 202, which is located higher inside and has a size that allows the piezoelectric element 212 to expand and contract, is formed.

  An annular vibration insulator 211 fitted into the first chamber 201 is fixed to the main body 20 by an adhesive member or the like (not shown), and a plate-like vibration receiving plate 213 is fitted into an opening on the inside thereof. It is adhesively fixed in the form of

  The piezoelectric element 212 housed in the second room 202 is bonded and fixed to the vibration receiving plate 213, and is supported by the vibration insulator 211 via the vibration receiving plate 213. The wiring 22 is electrically connected to the piezoelectric element 212. In addition, the wiring 22 is connected to a voltage monitoring unit 29 that determines a water depth at which the ultrasonic vibration becomes maximum based on a voltage signal sent from the piezoelectric element.

  The ultrasonic sound pressure gauge 2 can be moved up and down in the Z-axis direction by an ultrasonic sound pressure meter elevating means 27 having a mechanism composed of, for example, an electric cylinder or a motor and a ball screw.

  The wafer separating apparatus 5C includes an ingot holding unit 60 that holds the ingot I described in the first embodiment, and a lifting unit 61 that moves the ingot holding unit 60 up and down in the vertical direction (Z-axis direction). A control means 9 for performing overall control is provided. The control means 9 is electrically connected to the voltage monitoring means 29, the ultrasonic sound pressure gauge elevating means 27, and the elevating means 61.

  In the position detecting step, high-frequency power is supplied from the power supply 55 to the ultrasonic vibration plate 53, the ultrasonic vibration plate 53 oscillates an ultrasonic wave having a predetermined vibration frequency, and the oscillated ultrasonic wave is The light L propagates through the bottom plate 50 of the liquid 59. Then, the ultrasonic wave (incident wave) heading toward the liquid surface and the ultrasonic wave (reflected wave) reflected from the liquid surface and returning to the bottom plate 50 overlap each other, and the depth of the sound pressure in the liquid L is high and low. And arise.

  For example, the ultrasonic sound pressure gauge 2 is sent in the −Z direction by the ultrasonic sound pressure gauge elevating means 27, and under the control of the ultrasonic sound pressure gauge elevating means 27 by the control means 9, the detection unit 21 The liquid L is positioned at the level of the liquid surface. From this state, under the control of the ultrasonic sound pressure gauge elevating means 27 by the control means 9, the ultrasonic sound pressure meter elevating means 27 further lowers the ultrasonic sound pressure meter 2 in the -Z direction, and the detecting section 21 Sinking inside. In addition, the control unit 9 counts the amount of drop of the detection unit 21 from the liquid level.

  In the liquid L, the vibration receiving plate 213 receives the ultrasonic vibration from the liquid L, and the ultrasonic vibration is further transmitted to the piezoelectric element 212. Then, the descending piezoelectric element 212 extracts an electric output proportional to the sound pressure, converts the electric output into a voltage, and sequentially sends the voltage signal to the voltage monitoring means 29 through the wiring 22. When the voltage signal transmitted from the piezoelectric element 212 reaches a maximum, the voltage monitoring unit 29 that monitors the voltage signal transmitted from the piezoelectric element 212 detects the sound pressure of the ultrasonic wave received by the piezoelectric element 212. Is notified to the control means 9 to the effect that has become the largest.

  The control means 9 for controlling the ultrasonic sound pressure gauge elevating means 27 includes, for example, a depth Z4 from the liquid level of the detection unit 21 in the liquid L at the time when the sound pressure of the ultrasonic wave received by the piezoelectric element 212 becomes maximum. Figure out.

(3) Separation Step Next, as shown in FIG. 9, the ingot holding means 60 holding the ingot I is sent in the −Z direction by the lifting / lowering means 61, and the ingot is controlled by the control means 9 under the control of the lifting / lowering means 61. The first surface Ia of I is positioned at the level of the liquid level. From this state, under the control of the elevating means 61 by the control means 9, the elevating means 61 further lowers the ingot holding means 60 in the −Z direction by a distance obtained by adding the thickness T of the wafer to be generated to the depth Z4. . Thus, the release layer M of the ingot I is positioned at the depth Z4 detected in the position detection step.

Thereby, the largest ultrasonic vibration is applied to the peeling layer M in the ingot I located at the depth Z4 where the sound pressure becomes highest in the Z-axis direction in the liquid L, and the wafer is moved from the ingot I to the wafer with the peeling layer M as a boundary. W is separated.
By lowering the ingot I in the liquid L in the separation step, the depth Z4 of the liquid L at which the sound pressure becomes maximum in the Z-axis direction may slightly change upward or downward. . In this case, the release layer M of the ingot I is positioned at the depth Z4 detected in the position detection step under the control of the control unit 9 under the information sent from the voltage monitoring unit 29, and then moved up and down. The means 61 may further slightly move the ingot holding means 60 upward or downward so as to follow the change.

(Embodiment 5 of wafer separation method)
Hereinafter, the wafer separation method according to the present invention (referred to as the wafer separation method of the fifth embodiment) is performed, and the wafer to be generated from the end surface (first surface Ia) of the ingot I shown in FIG. Each step of separating a wafer from an ingot I having a planar release layer M at a position corresponding to the thickness T will be described.

(1) Preparation Step The ingot I is transported, for example, to the wafer separation device 5D shown in FIG. 10 and the first surface Ia is directed upward on the bottom plate 50 of the liquid tank 59, that is, the release layer M side is It is placed with its upper side. Wafer separation device 5D is a modification of the configuration of wafer separation device 5 shown in FIG.

  Further, on the first surface Ia (upper surface) of the ingot I, the detection unit 11 including the piezoelectric element 112 is provided. The detection unit 11 is the same as that shown in FIG. 3 described in the first embodiment. The detection unit 11 is disposed on the first surface Ia of the ingot I with the vibration insulator 111 side down.

The wiring 12 is electrically connected to the piezoelectric element 112 of the detection unit 11. In addition, the wiring 12 is connected to a voltage monitoring unit 29 that determines a water depth at which the ultrasonic vibration becomes maximum.
As shown in FIG. 10, the wafer separation apparatus 5D includes control means 9 for controlling the entire apparatus. The control unit 9 is electrically connected to, for example, the voltage monitoring unit 29 connected to the detection unit 11 shown in FIG. 10 and the opening / closing valve 572 (for example, an electromagnetic valve) of the liquid supply unit 57. After the information is transmitted from the control unit 9 to the control unit 9, the opening / closing operation of the opening / closing valve 572 is controlled under the control unit 9.

(2) Liquid Supply Step After the preparation step, as shown in FIG. 11, under the control of the control means 9, the open / close valve 572 of the liquid supply means 57 is opened, and the liquid supply source 570 supplies the supply pipe 571. The liquid L (water) is supplied to the liquid tank 59, and the liquid L is accumulated in the liquid tank 59.
In addition, high frequency power is supplied from the power supply 55 to the ultrasonic vibration plate 53 at a predetermined output, and the ultrasonic vibration plate 53 oscillates ultrasonic waves having a predetermined vibration frequency, and the ultrasonic waves are applied to the liquid L in the liquid tank 59. Propagate. Then, the incident wave and the reflected wave overlap in the liquid L, and a strong sound pressure depth and a weak sound pressure depth are generated in the liquid L.

In the liquid L, the ultrasonic vibration is transmitted to the piezoelectric element 112 via the vibration receiving plate 113. Then, the piezoelectric element 112 sends a voltage signal proportional to the sound pressure to the voltage monitoring means 29, and the voltage monitoring means 29 starts monitoring the voltage signal sent from the piezoelectric element 112.
The liquid L is supplied from the liquid supply source 570 to the supply pipe 571, and the liquid L is accumulated in the liquid tank 59 and the liquid level rises, so that the immersed piezoelectric element 112 on the ingot I receives vibration. The sound pressure of the generated ultrasonic wave is the largest. Then, when the voltage signal sent from the piezoelectric element 112 becomes maximum, the voltage monitoring means 29 sends to the control means 9 information indicating that the sound pressure of the ultrasonic wave received by the piezoelectric element 112 has become maximum. Notice.

Then, under the control of the control means 9, the open / close valve 572 of the liquid supply means 57 is closed. Thereby, the release layer M of the ingot I is positioned at the depth Z5 where the sound pressure becomes maximum in the Z-axis direction in the liquid L. Although the height position of the peeling layer M of the ingot I and the depth position of the piezoelectric element 112 are illustrated in FIG. 11 so as to have a slight difference, the thickness T of the wafer is very small, for example, 1000 μm. Because of the thinness, the difference is a very small difference that can be ignored.
In addition, for example, when the depth at which the maximum sound pressure in the liquid L is obtained is not known after performing the respective steps as described above, once the liquid L is filled in the liquid tank 59, the supply of the liquid L is stopped. After that, while the drain valve 591 shown in FIG. 11 is opened to drain the liquid from the drain port 590 of the liquid tank 59, the detection unit 11 also uses the measurement data acquired at the time of supplying the liquid L to make the maximum sound. The depth at which the pressure becomes the pressure may be measured, and the peeling layer M of the ingot I may be positioned at the depth at which the sound pressure becomes the maximum.

(3) Separation Step By performing the liquid supply step, the largest ultrasonic vibration is applied to the peeling layer M in the ingot I located at the depth Z5 where the sound pressure is greatest in the Z-axis direction in the liquid L. The wafer W is separated from the ingot I at the boundary of the release layer M.

  It goes without saying that the method of separating a wafer according to the present invention is not limited to the above-described first to fifth embodiments, and may be implemented in various different forms within the scope of the technical idea. Further, the configurations of the respective wafer separation devices, the respective ultrasonic sound pressure meters, and the like illustrated in the accompanying drawings are not limited thereto, and can be appropriately changed within a range where the effects of the present invention can be exhibited.

I: ingot Ia: first surface of ingot Ib: second surface of ingot M: release layer 30: laser beam irradiation head 31: chuck table 5: wafer separation device 59: liquid tank 50: bottom plate 51: side wall 53: Ultrasonic vibration plate
55: power supply 57: liquid supply means 571: supply pipe 570: liquid supply source 572: open / close valve 1: ultrasonic sound pressure gauge 10: rod 10a: side surface of rod 12: wiring 11: detection unit 111: vibration insulator 112: piezoelectric Element 113: Vibration receiving plate 19: Water depth judging means 1A: Ultrasonic sound pressure gauge 15: Detection unit 114: First room 115: Second room
116: Vibration insulator 60: Ingot holding means 600: Suction pad 601: Arm section 61: Elevating means 9: Control means 5A: Wafer separating device 56: Table 58: Table elevating means 5B: Wafer separating device
5C: Wafer separation apparatus 2: Ultrasonic sound pressure gauge 20: Main body 21: Detecting unit 22: Wiring 29: Voltage monitoring means 27: Ultrasonic sound pressure gauge elevating means 5D: Wafer separation apparatus

Claims (2)

An ingot having a planar release layer formed at a position corresponding to the thickness of a wafer to be generated from an end face of the ingot is submerged in a liquid in a liquid tank, and ultrasonic vibration oscillated from an ultrasonic vibration plate and propagated to the liquid. Imparted to the release layer, a separation method of a wafer to separate the wafer from the ingot at the boundary of the release layer,
A liquid supply step of storing the liquid in the liquid tank;
A position detecting step of oscillating ultrasonic vibration propagating through the liquid from the ultrasonic vibration plate and detecting a depth at which a maximum sound pressure is obtained in the depth direction of the liquid using a piezoelectric element,
A separating step of positioning the release layer of the ingot at the depth detected in the position detection step and separating the wafer from the ingot with the release layer as a boundary. An ingot having a planar release layer formed at a position corresponding to the thickness of a wafer to be generated from the end face of the ingot is placed in a liquid tank, and liquid is supplied to the liquid tank to submerge the ingot, and ultrasonic waves are applied. A method of separating a wafer, in which ultrasonic waves are oscillated from a vibration plate to impart ultrasonic vibration, which propagates the liquid, to the release layer, and a wafer is separated from an ingot at the boundary of the release layer,
A preparation step of disposing an ingot with the release layer side facing upward in the liquid tank, and disposing a piezoelectric element on an upper surface of the ingot,
After the preparation step, the ultrasonic vibration is oscillated from the ultrasonic vibration plate and the liquid is supplied to the liquid tank to raise the liquid level, and the sound of the ultrasonic wave received by the piezoelectric element immersed in the ingot is received. A liquid supply step of stopping supply of the liquid when the pressure becomes maximum,
A separation step of separating the wafer from the ingot at the separation layer after the liquid supply step.

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