Substrate processing device, and substrate processing method

Abstract

This substrate processing device for processing a substrate includes a laser irradiation unit that irradiates the substrate with laser light, a lens that is included in the laser irradiation unit, an actuator that raises and lowers the lens, a measuring unit that measures a surface height of the substrate, and a control unit, wherein the control unit executes: control for using the measuring unit to measure the surface height of the substrate at a plurality of peripheral-direction measurement points arranged in the peripheral direction of the substrate; control for determining the height of the lens in accordance with the irradiation position of the laser light at peripheral-direction positions of the substrate on the basis of the surface height of the substrate measured at the peripheral-direction measurement points; and control for using the actuator to move the lens to the determined height, and irradiating the substrate with the laser light from the laser irradiation unit in pulses in the peripheral direction of the substrate.

Description

Substrate processing apparatus and substrate processing method

[0001] The present disclosure relates to a substrate processing apparatus and a substrate processing method.

[0002] Patent Document 1 discloses a modification device that irradiates the inside of a wafer with laser light. The modification device measures the irradiation position (irradiation height) of the laser light and adjusts the height of the laser light in real time.

[0003] International Publication No. 2020 / 184179

[0004] The technique according to the present disclosure irradiates a laser beam onto an appropriate position on a substrate.

[0005] One aspect of the present disclosure is a substrate processing apparatus for processing a substrate, comprising: a laser irradiation unit that irradiates the substrate with laser light; a lens included in the laser irradiation unit; an actuator that raises and lowers the lens; a measurement unit that measures a surface height of the substrate; and a control unit, wherein the control unit performs the following controls: using the measurement unit to measure the surface height of the substrate at a plurality of circumferential measurement points arranged around the substrate; determining a height of the lens according to an irradiation position of the laser light at a circumferential position of the substrate based on the surface height of the substrate measured at the circumferential measurement points; and using the actuator to move the lens to the determined height, and irradiating the laser light from the laser irradiation unit onto the substrate in pulses around the substrate.

[0006] According to the present disclosure, laser light can be irradiated onto an appropriate position on a substrate.

[0007] 1 is a side view showing an outline of the configuration of an overlapped wafer to be processed; FIG. 2 is a plan view showing an outline of the configuration of a wafer processing system; FIG. 3 is a side view showing an outline of the configuration of a first laser irradiation device; FIG. 4 is a plan view showing an outline of the configuration of a first laser irradiation device; FIG. 5 is an explanatory diagram showing main steps of wafer processing; FIG. 6 is a cross-sectional view showing a bonding strength reduction region and a peripheral modified layer formed on an overlapped wafer; FIG. 7 is a flow chart showing main steps of wafer processing; FIG. 8 is an explanatory diagram showing how the height of the backside of a first wafer is measured; FIG. 9 is a plan view showing an arrangement of circumferential measurement points on the peripheral portion of the first wafer; FIG. 10 is a graph showing an example of the height of the backside of the first wafer at the circumferential measurement points; FIG. 11 is a plan view showing an arrangement of radial measurement points on the peripheral portion of the first wafer; FIG. 12 is a graph showing an example of the height of the backside of the first wafer at the radial measurement points; FIG. 13 is an explanatory diagram showing how the height of a lens is adjusted when the peripheral portion of the first wafer is warped upward; FIG. 14 is an explanatory diagram showing how the height of a lens is adjusted when the peripheral portion of the first wafer is warped downward; and FIG. 15 is an explanatory diagram showing how the height of a lens is adjusted when the thickness of the peripheral portion of the first wafer is not constant. 1 is an explanatory diagram showing a state in which a back surface film on the back surface of a first wafer is removed in another embodiment; FIG. 2 is an explanatory diagram showing main steps of wafer processing in another embodiment; FIG. 3 is a plan view showing an arrangement of circumferential measurement points at the peripheral portion and central portion of a first wafer in another embodiment; FIG. 4 is a plan view showing an arrangement of circumferential measurement points at the peripheral portion and central portion of a first wafer in another embodiment;

[0008] Hereinafter, a wafer processing system including a first laser irradiation device and a second laser irradiation device as a substrate processing apparatus according to this embodiment, and a wafer processing method as a substrate processing method will be described with reference to the drawings. Note that in this specification and the drawings, elements having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0009] 1 , a wafer processing system 1 according to this embodiment, which will be described later, processes an overlapped wafer T as an overlapped substrate in which a first wafer W as a first substrate and a second wafer S as a second substrate are bonded together. Hereinafter, the surface of the first wafer W that is bonded to the second wafer S will be referred to as the front surface Wa, and the surface opposite the front surface Wa will be referred to as the back surface Wb. Similarly, the surface of the second wafer S that is bonded to the first wafer W will be referred to as the front surface Sa, and the surface opposite the front surface Sa will be referred to as the back surface Sb.

[0010] The first wafer W is a semiconductor wafer such as a silicon substrate, and at least one film is laminated on the front surface Wa side. Hereinafter, the film formed on the front surface Wa side will be referred to as a "laminated film." In this embodiment, the laminated film includes a device layer Dw and a bonding film Fw. The device layer Dw includes a plurality of devices. The device layer Dw may also include a layer (laser absorption layer) that absorbs the first laser light L1 (described later) and serves as a base point for peeling. The bonding film Fw may include, for example, an oxide film (THOX film, SiO ２ The first wafer W is bonded to the second wafer S via a bonding film Fw. The peripheral edge We of the first wafer W is chamfered, and the thickness of the cross section of the peripheral edge We decreases toward its tip. In the following description, the region of the first wafer W radially inward from the peripheral edge We to be removed may be referred to as the central region Wc.

[0011] The second wafer S has, for example, the same configuration as the first wafer W. That is, a device layer Ds and a bonding film Fs are formed as laminated films on the surface Sa side, and the peripheral portion is chamfered. Note that the second wafer S does not necessarily have to be a device wafer on which the device layer Ds is formed, and may be, for example, a support wafer that supports the first wafer W. In such a case, the second wafer S functions as a protective material that protects the device layer Dw of the first wafer W.

[0012] 1 illustrates an example in which a device layer and a bonding film are formed as laminated films on the surfaces of the first wafer W and the second wafer S. However, the type and number of laminated films are not limited to this.

[0013] 2 , wafer processing system 1 has a configuration in which a load / unload station 2 and a processing station 3 are integrally connected. In load / unload station 2, for example, a FOUP F capable of accommodating a plurality of overlapped wafers T is loaded and unloaded between the load / unload station 2 and the outside. Processing station 3 is equipped with various processing devices that perform desired processing on overlapped wafers T.

[0014] The carry-in / out station 2 is provided with a FOUP mounting table 10 on which a plurality of FOUPs F, for example, three FOUPs F, can be placed. A wafer transfer device 20 is provided on the positive X-axis side of the FOUP mounting table 10. The wafer transfer device 20 moves on a transfer path 21 extending in the Y-axis direction, and is configured to be able to transfer the overlapped wafer T between the FOUP F on the FOUP mounting table 10 and a transition stage 30, which will be described later.

[0015] A transition stage 30 is provided in the transfer station 2 on the X-axis positive side of the wafer transfer device 20. The transition stage 30 temporarily stores the overlapped wafer T for transfer to and from the processing station 3.

[0016] The processing station 3 is provided with a wafer transfer device 40, a first laser irradiation device 50, a second laser irradiation device 60, an edge removal device 70, and a cleaning device 80. The wafer transfer device 40 is disposed on the X-axis positive side of the transition stage 30. The first laser irradiation device 50 and the second laser irradiation device 60 are disposed on the Y-axis positive side of the wafer transfer device 40, and the edge removal device 70 and the cleaning device 80 are disposed on the Y-axis negative side of the wafer transfer device 40. The number and arrangement of the first laser irradiation device 50, the second laser irradiation device 60, the edge removal device 70, and the cleaning device 80 are not limited to those in this embodiment and can be determined as desired.

[0017] The wafer transport device 40 is configured to be freely movable on a transport path 41 extending in the X-axis direction, and is configured to be able to transport the overlapped wafer T to the transition stage 30, the first laser irradiation device 50, the second laser irradiation device 60, the edge removal device 70, and the cleaning device 80.

[0018] As shown in FIGS. 5A and 6, the first laser irradiation device 50 irradiates the interface between the first wafer W and the second wafer S with a first laser beam L1 (interface laser beam, for example, CO ２ The first laser irradiation device 50 irradiates the first wafer W with the first laser beam L1 at a desired interval (pulse pitch) in the circumferential direction, and also irradiates the first laser beam L1 at a desired interval (index pitch) in the radial direction, to form the bonding strength reduced region R. As shown in FIG. 1 , the first laser irradiation device 50 has a control device 51, which will be described later.

[0019] 3 and 4, the first laser irradiation device 50 has a chuck 100 that holds the overlapped wafer T on its upper surface. With the first wafer W on top and the second wafer S on the bottom, the chuck 100 suction-holds the back surface Sb of the second wafer S. The chuck 100 is provided with lifting pins (not shown) for supporting and lifting the overlapped wafer T from below. The lifting pins are inserted into through-holes (not shown) formed through the chuck 100 and are configured to be freely raised and lowered.

[0020] The chuck 100 is supported by a slider table 102 via an air bearing 101. A rotation mechanism 103 is provided on the underside of the slider table 102. The rotation mechanism 103 has a built-in motor, for example, as a drive source. The chuck 100 is configured to be rotatable about a vertical axis via the air bearing 101 by the rotation mechanism 103. The slider table 102 is configured to be movable along a rail 106 extending in the Y-axis direction on a base 105 via a movement mechanism 104 provided on the underside of the slider table 102. The drive source of the movement mechanism 104 is not particularly limited, but a linear motor, for example, is used.

[0021] A laser irradiation unit 110 is provided above the chuck 100. The laser irradiation unit 110 includes a laser head 111, an optical system 112, and a lens 113.

[0022] The laser head 111 has a laser oscillator (not shown) that oscillates the first laser light L1 in a pulsed manner. The first laser light L1 is a so-called pulse laser. As described above, the first laser light L1 is, for example, a CO ２ The laser head 111 may include other devices in addition to the laser oscillator, such as an amplifier.

[0023] The optical system 112 may include an optical element (not shown) that controls the intensity and position of the first laser light L1, and an attenuator (not shown) that attenuates the first laser light L1 to adjust the output. The optical system 112 may also be configured to be able to control the number and shape of the branches of the first laser light L1.

[0024] The lens 113 irradiates the first laser light L1 onto the interior of the overlapped wafer T held by the chuck 100, more specifically, onto the interface between the first wafer W and the second wafer S. This modifies the portion of the overlapped wafer T irradiated with the first laser light L1, forming a bonding strength reduced region R in which the bonding strength between the first wafer W and the second wafer S is reduced. Note that, in the technology disclosed herein, the "interface between the first wafer W and the second wafer S" includes the respective interfaces and interiors of the first wafer W, the device layer Dw (including the laser absorption layer for peeling included in the device layer Dw), Ds, the bonding films Fw and Fs, and the second wafer S. In other words, the position where the bonding strength reduced region R is formed is not particularly limited as long as the bonding strength between the first wafer W and the second wafer S can be reduced.

[0025] The lens 113 is configured to be movable in the horizontal direction by a movement mechanism (not shown), and is also configured to be movable up and down in the vertical direction by an actuator (elevating mechanism) 114. The actuator 114 may have any configuration, and may, for example, be a motor-driven ball screw or a piezoelectric element.

[0026] A first measurement unit 120 is provided above the chuck 100. The first measurement unit 120 is, for example, a displacement meter or an interferometer, and measures the height of the back surface Wb of the first wafer W (the surface of the overlapped wafer T) held by the chuck 100. The first measurement unit 120 measures the height of an arbitrary measurement point on the back surface Wb of the first wafer W. For example, the first measurement unit 120 may be fixed, and the chuck 100 may be moved horizontally and rotated to measure the height of the arbitrary measurement point. Alternatively, for example, the height of the arbitrary measurement point may be measured by moving the first measurement unit 120 horizontally using a movement mechanism (not shown).

[0027] The measurement result of the first measuring unit 120 is output to the control device 61 or the control device 90, which will be described later. The control device 61 or the control device 90 adjusts the height of the lens 113 (the irradiation height of the first laser light L1) based on the height of the back surface Wb measured as will be described later.

[0028] A second measurement unit 130 is provided on the side of the chuck 100. The second measurement unit 130 is, for example, a displacement meter or an interferometer, and measures the distance between the second measurement unit 130 and the outer edge of the overlapped wafer T. Specifically, while the chuck 100 is rotating, the distance between the second measurement unit 130 and the outer edge of the overlapped wafer T is measured at a plurality of measurement points in the circumferential direction of the overlapped wafer T.

[0029] The measurement results of the second measuring unit 130 are output to the control device 61 or the control device 90, which will be described later. Based on the measured distance, the control device 61 or the control device 90 acquires the amount of eccentricity between the chuck 100 and the overlapped wafer T, i.e., the amount of misalignment between the center of rotation of the chuck 100 and the center of the overlapped wafer T. The control device 61 or the control device 90 also performs eccentricity correction by moving the chuck 100 horizontally along the Y-axis direction so as to correct the acquired amount of eccentricity.

[0030] 5(b) and 6, the second laser irradiation device 60 irradiates the inside of the first wafer W with second laser light L2 (internal laser light, for example, a YAG laser or a fiber laser) to form a peripheral modified layer M and form a peripheral modified region N that serves as a base point for peeling off the peripheral portion We. As shown in FIG. 1, the second laser irradiation device 60 has a control device 61, which will be described later.

[0031] The configuration of the second laser irradiation device 60 is not particularly limited, but in one example, the second laser irradiation device 60 has the same configuration as the first laser irradiation device 50 .

[0032] As shown in FIG. 5C , the edge removal device 70 removes the edge portion We of the first wafer W, i.e., performs edge trimming, using the bonding strength reduced region R and the edge modified region N as base points. Any edge trimming method can be selected. In one example, the edge removal device 70 may insert, for example, a wedge-shaped blade B. Alternatively, for example, an impact may be applied to the edge portion We by spraying air or a water jet toward the edge portion We.

[0033] The cleaning device 80 performs a cleaning process on the first wafer W and the second wafer S after the edge trimming by the edge removal device 70, thereby removing particles from these wafers. Any cleaning method can be selected.

[0034] 1, the wafer processing system 1 is provided with a control device 51, a control device 61, and at least one control device 90. The control device 51 individually controls the operation of the first laser irradiation device 50. The control device 61 individually controls the operation of the second laser irradiation device 60. The control device 90 controls the entire series of wafer processing in the wafer processing system 1.

[0035] The control devices 51, 61, and 90 each process computer-executable instructions that cause the first laser irradiation device 50, the second laser irradiation device 60, and the wafer processing system 1 to perform the various steps described in this disclosure. The control devices 51, 61, and 90 can each be configured to control each element of the first laser irradiation device 50, the second laser irradiation device 60, and the wafer processing system 1 to perform the various steps described herein. In one embodiment, some or all of the control device 51 may be included in the first laser irradiation device 50, some or all of the control device 61 may be included in the second laser irradiation device 60, and some or all of the control device 90 may be included in the wafer processing system 1.

[0036] The control devices 51, 61, and 90 may each include a processing unit, a storage unit, and a communication interface. The control devices 51, 61, and 90 may each be realized by, for example, a computer. The processing unit may be configured to read a program providing logic or routines that enable various control operations from the storage unit and execute the read program to perform various control operations. This program may be stored in the storage unit in advance or may be acquired via a medium when needed. The acquired program is stored in the storage unit and read from the storage unit and executed by the processing unit. The medium may be various computer-readable storage media or a communication line connected to the communication interface. The storage medium may be temporary or non-temporary. The processing unit may be a CPU (Central Processing Unit) or one or more circuits. The storage unit may include a RAM (Random Access Memory), a ROM (Read Only Memory), a HDD (Hard Disk Drive), a SSD (Solid State Drive), or a combination thereof. The communication interface may communicate between the first laser irradiation device 50, the second laser irradiation device 60, and the wafer processing system 1 via a communication line such as a LAN (Local Area Network).

[0037] In this embodiment, the control device 51 and the control device 61 are installed separately for the first laser irradiation device 50 and the second laser irradiation device 60, respectively, but these control devices 51 and 61 may be configured integrally with the control device 90. In other words, the operations of the first laser irradiation device 50 and the second laser irradiation device 60 may be controlled by the control device 90.

[0038] Next, a description will be given of wafer processing performed using the wafer processing system 1 configured as described above. In this embodiment, the first wafer W and the second wafer S are bonded together to form an overlapping wafer T in advance.

[0039] First, a FOUP F containing a plurality of overlapping wafers T is placed on the FOUP placement table 10 of the carry-in / out station 2 .

[0040] Next, the overlapped wafer T is removed from the FOUP F by the wafer transfer device 20 and transferred to the transition stage 30. Subsequently, the overlapped wafer T is transferred to the first laser irradiation device 50 by the wafer transfer device 40.

[0041] The overlapped wafer T transferred to the first laser irradiation device 50 is first sucked and held by the chuck 100. The chuck 100 sucks and holds the back surface Sb of the second wafer S of the overlapped wafer T.

[0042] Next, the second measurement unit 130 is used to measure the distance between the second measurement unit 130 and the outer edge of the overlapped wafer T. At this time, the chuck 100 is rotated while measuring the distance at a plurality of measurement points in the circumferential direction of the overlapped wafer T. The measurement results of the second measurement unit 130 are output to, for example, the control device 61. Based on the measured distance, the control device 61 obtains the amount of eccentricity between the chuck 100 and the overlapped wafer T, i.e., the amount of misalignment between the center of rotation of the chuck 100 and the center of the overlapped wafer T (Step 1 in FIG. 7 ).

[0043] Next, the height of the back surface Wb of the first wafer W is measured using the first measurement unit 120 (St2 in FIG. 7 ). In St2, the height of the back surface Wb of the first wafer W is measured while performing eccentricity correction, taking into account the amount of eccentricity between the chuck 100 and the overlapped wafer T. That is, the height of the back surface Wb of the first wafer W is measured while rotating the chuck 100 (overlapping wafer T) and moving the chuck 100 horizontally along the Y-axis direction so as to correct the amount of eccentricity obtained in St1.

[0044] In St2, as shown in FIG. 8 , the distance H between the back surface Wb and the first measurement unit 120 is measured as the height of the back surface Wb of the first wafer W. For example, when the lower end of the first measurement unit 120 and the lower end of the lens 113 are at the same height, the distance H is, in other words, the distance between the back surface Wb and the lens 113. Furthermore, for example, the lens 113 is positioned so that the target focal position of the first laser light L1 irradiated from the lens 113 is located at the interface between the first wafer W and the second wafer S where the bonding strength reduced region R is formed (in the illustrated example, the interface between the first wafer W and the laminated film). Note that, for example, if the height positional relationship between the lower end of the first measurement unit 120 and the lower end of the lens 113 is known, the distance between the back surface Wb and the lens 113 can be calculated as the distance H, and changes in the distance H can be understood.

[0045] In St2, the height of the backside Wb is measured at multiple, e.g., eight, circumferential measurement points P1 to P8 arranged circumferentially on the peripheral edge We of the first wafer W, as shown in FIG. 9 . For example, the circumferential measurement points P1 to P8 are arranged at equal intervals in the circumferential direction, and the circumferential interval between the circumferential measurement points P1 to P8 is greater than the circumferential interval (pulse pitch) of the first laser beam L1. FIG. 10 shows an example of plotting the height of the backside Wb at the circumferential measurement points P1 to P8. In the following description, these circumferential measurement points P1 to P8 may be collectively referred to as circumferential measurement points P. Note that the number and arrangement of the circumferential measurement points P are not limited to those in this embodiment; for example, the circumferential measurement points P may be located radially inward of the peripheral edge We.

[0046] In St2, the height of the backside Wb is measured at a plurality of, for example, five, radial measurement points Q1 to Q5 arranged radially on the peripheral edge We of the first wafer W, as shown in FIG. 11 . For example, the radial measurement points Q1 to Q5 are arranged at equal intervals in the radial direction, and the radial interval between the radial measurement points Q1 to Q5 is greater than the radial interval (index pitch) of the first laser beam L1. FIG. 12 shows an example of plotting the height of the backside Wb at the radial measurement points Q1 to Q5. In the following description, these radial measurement points Q1 to Q5 may be collectively referred to as radial measurement points Q. Note that the number and arrangement of the radial measurement points Q are not limited to those in this embodiment; for example, the radial measurement points Q may be located radially inside the peripheral edge We.

[0047] In this embodiment, it is preferable that the radial measurement points Q1 to Q5 among the circumferential measurement points P1 to P8 are located at the same radial position from the center or outer periphery of the first wafer W. Then, in St2, the height of the backside Wb is measured at a number obtained by multiplying the number of circumferential measurement points P by the number of radial measurement points Q, which is 8 x 5 points in this embodiment, for a total of 40 measurement points. The measurement results of the first measurement unit 120 are output to, for example, the control device 61. The control device 61 creates a table of the height of the backside Wb, with the circumferential measurement points P and the radial measurement points Q as labels (headings) (St3 in FIG. 7). Note that the radial measurement points Q1 to Q5 among the circumferential measurement points P1 to P8 may be located at different radial positions from the center or outer periphery of the first wafer W.

[0048] Based on the table of heights of the back surface Wb created in St3, the control device 61 adjusts and determines the height of the lens 113 using the actuator 114 in accordance with the irradiation position of the first laser light L1 in the circumferential and radial directions of the first wafer W (St4 in FIG. 7). Note that in St4, a table of heights of the lens 113 may be created, with the circumferential measurement point P and the radial measurement point Q as labels (headings). In such a case, in St5 described later, the height of the lens 113 is adjusted based on the table.

[0049] 13( a), for example, when the overlapped wafer T is flat, the first laser light L1 from the lens 113 is irradiated onto the interface between the first wafer W and the second wafer S (the interface between the first wafer W and the laminated film in the illustrated example), which is the target focal position. On the other hand, when the peripheral portion of the overlapped wafer T is warped upward as shown in FIG. 13( b), when the first laser light L1 is irradiated from the same height as the lens 113 shown in FIG. 13( a), the focal position of the first laser light L1 deviates from the target focal position. Note that, although FIG. 13( b) illustrates a case where the peripheral portion of the overlapped wafer T is warped upward, there is also a case where only the peripheral portion We of the first wafer W is warped upward.

[0050] Therefore, in St4, as shown in Fig. 13(c), the lens 113 (the irradiation height of the first laser light L1) is raised to align the focal position of the first laser light L1 with the target focal position. If the amount of variation in the height of the back surface Wb of the overlapped wafer T due to warping of the overlapped wafer T from the height of the back surface Wb when the overlapped wafer T is flat as shown in Fig. 13(a) is denoted as ΔH, the movement amount G of the lens 113 is the same as the amount of variation ΔH. Note that the amount of variation ΔH is derived based on the height of the back surface Wb measured by the first measurement unit 120.

[0051] Furthermore, as shown in FIG. 14( b), for example, the peripheral edge of the second wafer S may be rolled off in a previous process (e.g., CMP), causing the peripheral edge We of the first wafer W to warp downward. In such a case, if the first laser beam L1 is irradiated from the same height as the lens 113 when the overlapped wafer T is flat as shown in FIG. 14( a), the focal position of the first laser beam L1 will deviate from the target focal position as shown in FIG. 14( b). Therefore, in St4, as shown in FIG. 14( c), the lens 113 (the irradiation height of the first laser beam L1) is lowered by a movement amount G equal to the fluctuation amount ΔH to align the focal position of the first laser beam L1 with the target focal position. Note that while FIG. 14( b) illustrates a case in which the peripheral edge of the overlapped wafer T warps downward, there is also a case in which only the peripheral edge We of the first wafer W warps downward. The fluctuation amount ΔH is derived based on the height of the back surface Wb measured by the first measurement unit 120.

[0052] In St4, the height of the back surface Wb is measured at circumferential measurement points P1 to P8 as shown in Fig. 10. Then, the amount of fluctuation ΔH can be calculated to determine the amount of movement G of the lens 113. In addition, the height of the back surface Wb is linearly interpolated between the circumferential measurement points P1 to P8 (solid line in Fig. 10), and the amount of fluctuation ΔH can be calculated to determine the amount of movement G of the lens 113.

[0053] For example, the height of the lens 113 at the first circumferential measurement point P1 is determined as the first height, and the height of the lens 113 at the second circumferential measurement point P2 is determined as the second height. In this case, the height of the lens 113 between the first circumferential measurement point P1 and the second circumferential measurement point P2 is determined as a height obtained by linearly interpolating from the first height to the second height.

[0054] In St4, when the height of the lens 113 at the first circumferential measurement point P1 is determined as the first height and the height of the lens 113 at the second circumferential measurement point P2 is determined as the second height, the height of the lens 113 between the first circumferential measurement point P1 and the second circumferential measurement point P2 may be determined as the first height. Then, the height of the lens 113 when it is positioned at the second circumferential measurement point P2 may be determined as the second height.

[0055] Furthermore, in this embodiment, the circumferential measurement points P1 to P8 and the irradiation position (circumferential position) of the first laser beam L1 from the lens 113 coincide with each other, and the height of the lens 113 is determined between the measurements of the circumferential measurement points P1 to P8. However, even if the circumferential measurement points P1 to P8 and the irradiation position of the first laser beam L1 do not coincide with each other, the height of the lens 113 can be determined as long as the irradiation position of the first laser beam L1 is a position that linearly interpolates the circumferential measurement points P1 to P8.

[0056] In St4, the height of the back surface Wb is measured at radial measurement points Q1 to Q5 as shown in Fig. 12. Then, the amount of fluctuation ΔH can be calculated to determine the amount of movement G of the lens 113. In addition, the height of the back surface Wb is linearly interpolated between the radial measurement points Q1 to Q5 (solid line in Fig. 12), and the amount of fluctuation ΔH can be calculated to determine the amount of movement G of the lens 113.

[0057] For example, the height of the lens 113 at the first radial measurement point Q1 is determined as the first height, and the height of the lens 113 at the second radial measurement point Q2 is determined as the second height. In this case, the height of the lens 113 between the first radial measurement point Q1 and the second radial measurement point Q2 is determined as a height obtained by linearly interpolating from the first height to the second height.

[0058] Furthermore, in this embodiment, the radial measurement points Q1 to Q5 and the irradiation position (radial position) of the first laser light L1 from the lens 113 coincide with each other, and the height of the lens 113 is determined between the measurements of the radial measurement points Q1 to Q5. However, even if the radial measurement points Q1 to Q5 and the irradiation position of the first laser light L1 do not coincide with each other, the height of the lens 113 can be determined as long as the irradiation position of the first laser light L1 is a position that linearly interpolates the radial measurement points Q1 to Q5.

[0059] Next, as shown in FIG. 5A , a first laser beam L1 is irradiated along the interface between the first wafer W and the second wafer S (the interface between the first wafer W and the laminated film in the illustrated example) to form a bonding strength reduced region R where the first wafer W and the second wafer S are separated from each other at the peripheral edge We to be removed ( St5 in FIG. 7 ). At this time, the first laser beam L1 is irradiated in pulses in the circumferential direction while the chuck 100 is rotated, and then the chuck 100 is moved in the radial direction to irradiate the first laser beam L1 in pulses in the radial direction. The first laser beam L1 may be irradiated in multiple circular rings or in a spiral pattern. Thus, a ring-shaped bonding strength reduced region R is formed. The radial width of the bonding strength reduced region R is set to a width that allows the peripheral edge We of the first wafer W to be removed to be appropriately removed.

[0060] In St5, the height of the lens 113 is adjusted to the height determined in St4 according to the irradiation position of the first laser light L1 in the circumferential and radial positions of the first wafer W, and the first laser light L1 is irradiated. Therefore, even if the peripheral edge of the overlapped wafer T is warped or the height of the back surface Wb within the surface of the first wafer W varies as shown in FIGS. 13 and 14 , for example, the focal position of the first laser light L1 can be appropriately aligned with the target focal position. As a result, the bonding strength reduced region R can be appropriately formed.

[0061] Next, the overlapped wafer T with the bond strength reduced region R formed thereon is transferred by the wafer transfer device 40 to the second laser irradiation device 60 .

[0062] The overlapped wafer T transferred to the second laser irradiation device 60 is first sucked and held by the chuck 100. The chuck 100 sucks and holds the back surface Sb of the second wafer S of the overlapped wafer T.

[0063] Next, the second measurement unit 130 is used to measure the distance between the second measurement unit 130 and the outer edge of the overlapped wafer T, and the control device 61 acquires the amount of eccentricity between the chuck 100 and the overlapped wafer T. The method for acquiring the amount of eccentricity between the chuck 100 and the overlapped wafer T is the same as in St1 described above. Next, eccentricity correction is performed while moving the chuck 100 horizontally along the Y-axis direction so as to correct the amount of eccentricity between the chuck 100 and the overlapped wafer T.

[0064] Next, as shown in FIG. 5B , the second laser beam L2 is irradiated into the first wafer W along the boundary between the peripheral edge portion We and the central portion We of the first wafer W. The boundary between the peripheral edge portion We and the central portion We extends, for example, in the thickness direction of the first wafer W. At this time, the second laser beam L2 is irradiated in pulses in the circumferential direction while the chuck 100 is rotated, forming an annular peripheral modified layer M. Once the peripheral modified layer M is formed, a crack C extends from the peripheral modified layer M along the boundary between the peripheral edge portion We and the central portion We. A peripheral modified region N including the peripheral modified layer M and the crack C is then formed (Step 6 in FIG. 7 ). The crack C connects to the bonding strength reduced region R, and the peripheral modified region N extends between the back surface Wb of the first wafer W and the bonding strength reduced region R. The first laser beam L1 is irradiated while the chuck 100 is rotated, and the peripheral modified region N is formed in a ring shape in a plan view.

[0065] In this embodiment, the peripheral modified region N extends in the thickness direction, but the shape of the peripheral modified region N is not limited to this. For example, the lower portion of the peripheral modified region N may be curved, or the entire peripheral modified region N may have a curved shape that is convex downward. Furthermore, for example, the peripheral modified region N may have a linear shape that slopes from the inner side to the outer side in the radial direction of the first wafer W from the back surface Wb to the front surface Wa of the first wafer W.

[0066] In St6, the height of the lens 113 is adjusted to the height determined in St4 according to the irradiation position of the second laser beam L2 in the circumferential direction of the first wafer W, and the second laser beam L2 is irradiated. At this time, the height of the lens 113 may be adjusted to the height determined in St4 in the first laser irradiation device 50. However, it is preferable to determine the height of the lens 113 by performing St2 to St4 in the second laser irradiation device 60 between St5 and St6. That is, in the second laser irradiation device 60, the first measurement unit 120 measures the height of the back surface Wb (St2), creates a table of the height of the back surface Wb (St3), and determines the height of the lens 113 (St4). In this way, even when the peripheral edge of the overlapped wafer T is warped or the height of the back surface Wb varies within the plane of the first wafer W, as shown in FIGS. 13 and 14 , the focal position of the second laser beam L2 can be appropriately aligned with the target focal position. As a result, the peripheral modified region N can be appropriately formed.

[0067] Next, the overlapped wafer T with the peripheral modified region N formed thereon is transferred by the wafer transfer device 40 to the peripheral removal device 70. In the peripheral removal device 70, a blade B is inserted between the first wafer W and the second wafer S as shown in FIG. 5(c), and the peripheral portion We is removed from the first wafer W (St7 in FIG. 7). At this time, the peripheral portion We is peeled and removed from the central portion We of the first wafer W, using the peripheral modified region N and the bonding strength reduced region R as base points.

[0068] Next, the overlapped wafer T from which the peripheral edge portion We has been removed is transferred by the wafer transfer device 40 to the cleaning device 80. In the cleaning device 80, the first wafer W and the second wafer S are cleaned (St8 in FIG. 7).

[0069] Thereafter, the laminated wafer T that has been subjected to all the processes is transferred to the transition stage 30 by the wafer transfer device 40, and further transferred to the FOUP F on the FOUP mounting table 10 by the wafer transfer device 20. In this way, the series of wafer processes in the wafer processing system 1 is completed.

[0070] According to the above embodiment, in St2, the height of the backside Wb of the first wafer W is measured at a plurality of circumferential measurement points P and a plurality of radial measurement points Q, and in St4, the height of the lens 113 is determined according to the circumferential and radial positions of the first wafer W. Then, in St5, the height of the lens 113 is adjusted according to the irradiation position of the first laser light L1 at the circumferential and radial positions of the first wafer W, and the first laser light L1 is irradiated. Therefore, even if the peripheral edge of the overlapped wafer T is warped, the focal position of the first laser light L1 can be appropriately aligned with the target focal position. As a result, the bonding strength reduced region R can be appropriately formed.

[0071] Also in St6, the height of the lens 113 is adjusted according to the irradiation position of the second laser beam L2 in the circumferential direction of the first wafer W, and the second laser beam L2 is irradiated, so that the focal position of the second laser beam L2 can be appropriately aligned with the target focal position, thereby allowing the peripheral modified region N to be appropriately formed.

[0072] As described above, in this embodiment, the laser processing using the first laser beam L1 and the laser processing using the second laser beam L2 can be performed appropriately, thereby improving the quality of the laser processing. Furthermore, the reduced bonding strength region R and the peripheral modified region N can be appropriately formed, thereby appropriately removing (edge ​​trimming) the peripheral portion We of the first wafer W.

[0073] In a conventional modification device, for example, disclosed in Patent Document 1, the irradiation position of the laser beam is measured and the height of the laser beam is adjusted in real time. However, in this embodiment, even if the first measurement unit 120 cannot be provided in the optical paths of the first laser beam L1 and the second laser beam L2, the focal positions of the first laser beam L1 and the second laser beam L2 can be appropriately adjusted.

[0074] In the above embodiment, the case where the peripheral edge portion of the overlapped wafer T is warped as shown in FIGS. 13 and 14 has been described, but the technology of the present disclosure can also be applied to cases where the overlapped wafer T has other shapes.

[0075] 15(b), the technology of the present disclosure can also be applied to a case where the thickness of the peripheral edge portion We of the first wafer W is not constant and the back surface Wb is inclined. In such a case, if the first laser light L1 is irradiated from the same height as the lens 113 when the overlapped wafer T shown in FIG. 15(a) is flat, the focal position of the first laser light L1 will be shifted from the target focal position as shown in FIG.

[0076] 15(a) and 15(b), when the thickness of the first wafer W at the peripheral portion We is different and the height of the lens 113 is the same, i.e., when the distance between the back surface Wb and the lens 113 is different, the refraction state of the first laser light L1 changes when the first laser light L1 passes through the first wafer W. For example, compared to the focal position of the first laser light L1 at a position where the thickness of the first wafer W is large (see FIG. 15(a)), the focal position of the first laser light L1 at a position where the thickness of the first wafer W is small is higher (see FIG. 15(b)).

[0077] 15( a), the height of the lens 113 at a position where the thickness of the first wafer W is small is made higher or lower as shown in Fig. 15( c). In this case, the refraction state of the first laser light L1 when the first laser light L1 passes through the first wafer W can be made the same, and the focal position of the first laser light L1 can be made the same.

[0078] 15C, in St4 of the present embodiment, the vertical movement amount G of the lens 113 is determined based on the height of the back surface Wb of the first wafer W measured in St2 described above and the thickness of the first wafer W. The thickness of the first wafer W is determined in advance before St4 is performed. In this way, the focal position of the first laser light L1 can be aligned with the target focal position.

[0079] In addition, in St4 of this embodiment, whether the lens 113 is raised or lowered is arbitrarily set depending on the refraction state of the first laser light L1.

[0080] In this embodiment, the same effects as those of the above embodiment can be obtained, that is, the focal position of the first laser beam L1 can be aligned with the target focal position to appropriately form the reduced bonding strength region R. Similarly, the focal position of the second laser beam L2 can be aligned with the target focal position to appropriately form the peripheral modified region N.

[0081] In the above embodiment, the overlapped wafer T may have a back surface film (e.g., an oxide film) formed on the back surface Wb (upper surface) of the first wafer W before the wafer processing steps St1 to St8 are performed in the wafer processing system 1. If such a back surface film is formed, the first laser beam L1 and the second laser beam L2 may be obstructed by the back surface film and may not be irradiated to appropriate positions in St5 and St6. Therefore, the back surface film is removed before the irradiation process of the first laser beam L1 in St5 and the irradiation process of the second laser beam L2 in St6 are performed.

[0082] For example, removal of the back surface film is performed by a third laser irradiation device (not shown) provided in the wafer processing system 1. The configuration of the third laser irradiation device is not particularly limited, but in one example, the third laser irradiation device has a configuration similar to that of the first laser irradiation device 50. In such a case, the third laser irradiation device is configured to be able to irradiate the laminated wafer T (first wafer W) on the chuck 100 with a third laser light (removal laser light, for example, a UV femtosecond laser) instead of the first laser light L1 for the interface.

[0083] 16 , the third laser irradiation device irradiates a back surface film (not shown) on the back surface Wb of the first wafer W with a third laser beam L3. The third laser beam L3 removes the back surface film of the first wafer W by laser ablation.

[0084] In this embodiment, the technology of the present disclosure can also be applied when irradiating the third laser beam L3. That is, the focal position of the third laser beam L3 can be adjusted to the target focal position depending on the irradiation position of the third laser beam L3, and the back surface film can be appropriately removed.

[0085] In the above embodiment, the peripheral portion We is removed from the first wafer W using the peripheral modified region N and the bonding strength reduced region R as base points, but the base points for removing the peripheral portion We are not limited to these. For example, as shown in FIG. 17 , the peripheral portion We may be removed using the first peripheral modified region N1 and the second peripheral modified region N2 as base points.

[0086] First, in the second laser irradiation device 60, a first peripheral modified region N1 and a second peripheral modified region N2 are formed inside the first wafer W.

[0087] 17( a), when forming the first peripheral modified region N1, the second laser beam L2 is irradiated in a substantially vertical direction into the interior of the first wafer W. When the first peripheral modified layer M1 is formed by the second laser beam L2, a first crack C1 extends from the first peripheral modified layer M1 along the boundary between the peripheral portion We and the central portion Wc. Then, the first peripheral modified region N1 including the first peripheral modified layer M1 and the first crack C1 is formed.

[0088] 17( b), when forming the second peripheral modified layer M2, the inside of the first wafer W is irradiated with a second laser beam L2 in a horizontal direction. When the second peripheral modified layer M2 is formed by the second laser beam L2, a second crack C2 extends horizontally from the second peripheral modified layer M2. A second peripheral modified region N2 including the second peripheral modified layer M2 and the second crack C2 is then formed. The second peripheral modified layer M2 is formed by extending horizontally in a straight line radially outward from the lower end of the first peripheral modified region N1.

[0089] 17( c), in the peripheral edge removal device 70, a blade B is inserted between the first wafer W and the second wafer S, and the peripheral edge We is removed from the first wafer W. Note that the first wafer W remaining on the second wafer S may be removed by laser ablation, for example, by irradiating it with the third laser light L3 described above.

[0090] In this embodiment, the technology disclosed herein can also be applied when irradiating the second laser beam L2. That is, the focal position of the second laser beam L2 can be adjusted to a target focal position depending on the irradiation position of the second laser beam L2, and the first peripheral modified layer M1 and the second peripheral modified layer M2 can be appropriately formed.

[0091] The technology disclosed herein can also be applied to a case where, for example, a peeled region is formed in the surface direction by irradiating the first laser light L1 onto the entire interface between the first wafer W and the second wafer S. In such a case, the first wafer W is separated from the second wafer S using the peeled region as a base point, thereby performing so-called laser lift-off.

[0092] The technology of the present disclosure can also be applied to a case where a modified region is formed in the planar direction by irradiating the entire surface of the inside of the first wafer W with the second laser light L2. In such a case, the upper first wafer W is separated from the lower first wafer W using the modified region as a base point, and the first wafer W is thinned.

[0093] The technology of the present disclosure can also be applied to a case where, for example, an internal modified region is formed by irradiating the inside of the first wafer W with the second laser light L2 in a planar direction, and then irradiating the second laser light L2 from the edge of the internal modified region along the boundary between the peripheral portion We and the central portion Wc. In such a case, the upper first wafer W is separated from the lower first wafer W using the internal modified region as a base point to thin the first wafer W, and the peripheral portion We of the first wafer W is removed using the internal modified region as a base point.

[0094] In either of the above cases, the first laser light L1 or the second laser light L2 is irradiated in the surface direction of the overlapped wafer T, and the technology disclosed herein can also be applied to the irradiation of this first laser light L1 or the second laser light L2.

[0095] 13 and 14, or when the thickness of the peripheral portion We of the first wafer W is not constant as shown in Fig. 15, the height of the back surface Wb at the peripheral portion We of the first wafer W is measured in the same manner as in St2 described above. That is, the height of the back surface Wb is measured at a plurality of circumferential measurement points P, and the height of the back surface Wb is measured at a plurality of radial measurement points Q.

[0096] In this case, the same effect as in the above embodiment can be obtained in the peripheral portion We, that is, the focal position of the first laser light L1 or the second laser light L2 can be adjusted to the target focal position.

[0097] On the other hand, in the central portion Wc of the first wafer W, the thickness of the first wafer W is constant, and the height of the backside Wb is measured at the central measurement point Pc, for example, as shown in Fig. 18. Alternatively, in the central portion Wc, the height of the backside Wb is measured at a plurality of, for example, four circumferential measurement points P11 to P14, for example, as shown in Fig. 19. The circumferential spacing between these circumferential measurement points P11 to P14 in the central portion Wc is greater than the circumferential spacing between the circumferential measurement points P1 to P8 in the peripheral portion We.

[0098] In this case, the height of the back surface Wb is measured at the central measurement point Pc or the circumferential measurement points P11 to P14 in the central portion Wc, and the height of the lens 113 can be adjusted based on the measurement results. As a result, the focal position of the first laser beam L1 or the second laser beam L2 can be adjusted to the target focal position depending on the irradiation position of the first laser beam L1 or the second laser beam L2.

[0099] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims. For example, the components of the above-described embodiments may be arbitrarily combined. Such an arbitrary combination naturally provides the functions and effects of each of the components involved in the combination, and also provides other functions and effects that are apparent to those skilled in the art from the description of this specification.

[0100] Furthermore, the effects described in this specification are merely descriptive or exemplary and are not limiting. In other words, the technology according to the present disclosure may achieve other effects that are apparent to those skilled in the art from the description of this specification, in addition to or in place of the above-described effects.

[0101] 50 First laser irradiation device 51 Control device 60 Second laser irradiation device 61 Control device 90 Control device 110 Laser irradiation section 113 Lens 120 First measurement section L1 First laser beam L2 Second laser beam P Circumferential measurement point S Second wafer T Overlapped wafer W First wafer

Claims

1. A substrate processing apparatus for processing a substrate, comprising: a laser irradiation unit that irradiates the substrate with laser light; a lens included in the laser irradiation unit; an actuator that raises and lowers the lens; a measurement unit that measures a surface height of the substrate; and a control unit, wherein the control unit performs the following controls: using the measurement unit to measure the surface height of the substrate at a plurality of circumferential measurement points arranged around the substrate; determining the height of the lens in accordance with the irradiation position of the laser light at a circumferential position of the substrate based on the surface height of the substrate measured at the circumferential measurement points; and using the actuator to move the lens to the determined height, and controlling the laser irradiation unit to irradiate the substrate with the laser light in pulses around the substrate.

2. The substrate processing apparatus of claim 1, wherein the plurality of circumferential measurement points include a first circumferential measurement point and a second circumferential measurement point that are adjacent in the circumferential direction, and the control unit executes the following controls: determining the height of the lens at the first circumferential measurement point to a first height; determining the height of the lens at the second circumferential measurement point to a second height; and determining the height of the lens between the first circumferential measurement point and the second circumferential measurement point to a height linearly interpolated from the first height to the second height.

3. The substrate processing apparatus of claim 1, wherein the plurality of circumferential measurement points include a first circumferential measurement point and a second circumferential measurement point that are adjacent in the circumferential direction, and the control unit executes the following controls: determining the height of the lens to a first height at the first circumferential measurement point; determining the height of the lens to a second height at the second circumferential measurement point; and determining the height of the lens to the first height between the first circumferential measurement point and the second circumferential measurement point.

4. The substrate processing apparatus of claim 1, wherein the substrate is divided into a central portion and a peripheral portion in a planar view, and the control unit performs control to measure the surface height of the substrate at a plurality of circumferential measurement points in the peripheral portion, and control to measure the surface height of the substrate at a central measurement point in the central portion.

5. The substrate processing apparatus of claim 1, wherein the substrate is divided into a central portion and a peripheral portion in a planar view, and the control unit executes control to make the interval between adjacent circumferential measurement points in the peripheral portion smaller than the interval between adjacent circumferential measurement points in the central portion.

6. The substrate processing apparatus according to claim 1, wherein the control unit executes control to determine the height of the lens so that the lens is raised and lowered by a distance equal to the amount of variation in the surface height of the substrate at the irradiation position of the laser light.

7. The substrate processing apparatus of claim 1, wherein the control unit performs the following controls: using the measurement unit to measure the surface height of the substrate at a plurality of radial measurement points arranged radially of the substrate; determining the height of the lens according to the irradiation position of the laser light at the radial position of the substrate based on the surface height of the substrate measured at the radial measurement points; and using the actuator to move the lens to the determined height and irradiate the laser light from the laser irradiation unit onto the substrate in pulses radially of the substrate.

8. The substrate processing apparatus of claim 7, wherein the plurality of radial measurement points include a first radial measurement point and a second radial measurement point that are adjacent in the radial direction, and the control unit executes the following controls: determining the height of the lens to a first height at the first radial measurement point; determining the height of the lens to a second height at the second radial measurement point; and determining the height of the lens between the first radial measurement point and the second radial measurement point to a height linearly interpolated from the first height to the second height.

9. The substrate processing apparatus of claim 7, wherein the control unit performs control to create a table of the surface heights of the substrate measured at the plurality of circumferential measurement points and the plurality of radial measurement points, and control to determine the height of the laser irradiation unit based on the table.

10. A substrate processing method for processing a substrate, comprising: using a measurement unit to measure a surface height of the substrate at a plurality of circumferential measurement points arranged around the circumference of the substrate; determining the height of a lens included in a laser irradiation unit according to the irradiation position of laser light at the circumferential position of the substrate based on the surface height of the substrate measured at the circumferential measurement points; and using an actuator to move the lens to the determined height, and irradiating the substrate with laser light in pulses from the laser irradiation unit around the circumference of the substrate.

11. The substrate processing method of claim 10, wherein the plurality of circumferential measurement points include a first circumferential measurement point and a second circumferential measurement point that are adjacent in the circumferential direction, and the substrate processing method includes: determining the height of the lens at the first circumferential measurement point to be a first height; determining the height of the lens at the second circumferential measurement point to be a second height; and determining the height of the lens between the first circumferential measurement point and the second circumferential measurement point to be a height obtained by linearly interpolating from the first height to the second height.

12. The substrate processing method of claim 10, wherein the plurality of circumferential measurement points include a first circumferential measurement point and a second circumferential measurement point that are adjacent to each other in the circumferential direction, and the substrate processing method includes: determining the height of the lens at the first circumferential measurement point to be a first height; determining the height of the lens at the second circumferential measurement point to be a second height; and determining the height of the lens between the first circumferential measurement point and the second circumferential measurement point to be the first height.

13. The substrate processing method according to claim 10, wherein the substrate is divided into a central portion and a peripheral portion in a planar view, and the substrate processing method includes measuring the surface height of the substrate at a plurality of circumferential measurement points in the peripheral portion, and measuring the surface height of the substrate at a central measurement point in the central portion.

14. A substrate processing method as described in claim 10, wherein the substrate is divided into a central portion and a peripheral portion when viewed in a plane, and the substrate processing method includes making the interval between adjacent circumferential measurement points in the peripheral portion smaller than the interval between adjacent circumferential measurement points in the central portion.

15. The substrate processing method according to claim 10, further comprising determining the height of the lens so that the lens is raised and lowered by a distance equal to the amount of variation in the surface height of the substrate at the irradiation position of the laser light.

16. A substrate processing method as described in claim 10, comprising: using the measurement unit to measure the surface height of the substrate at a plurality of radial measurement points arranged radially of the substrate; determining the height of the lens according to the irradiation position of the laser light at the radial position of the substrate based on the surface height of the substrate measured at the radial measurement points; and using the actuator to move the lens to the determined height and irradiate the laser light from the laser irradiation unit onto the substrate in pulses in the radial direction of the substrate.

17. The substrate processing method described in claim 16, wherein the plurality of radial measurement points include a first radial measurement point and a second radial measurement point that are adjacent to each other in the radial direction, and the substrate processing method includes: determining the height of the lens at the first radial measurement point to be a first height; determining the height of the front lens at the second radial measurement point to be a second height; and determining the height of the lens between the first radial measurement point and the second radial measurement point to be a height obtained by linearly interpolating from the first height to the second height.

18. A substrate processing method according to claim 16, comprising: creating a table of the surface heights of the substrate measured at a plurality of the circumferential measurement points and a plurality of the radial measurement points; and determining the height of the laser irradiation portion based on the table.

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