Processing system and processing method

Abstract

To properly remove a modified layer remaining on the separated surface of a substrate that has been peeled using a modified layer formed by irradiating laser light as the base point.SOLUTION: Provided is a processing system for processing the object to be processed, the processing system comprising: a modified layer position acquisition device for acquiring the position of a modified layer that remains on a separated surface of a separated body having been separated using, as the base point, the modified layer formed inside of the object to be processed; a modified layer removal device for removing the modified layer remaining on the separated surface by irradiating the separated surface with laser light; and a control device. The control device executes: exercising control in the modified layer position acquisition device to detect the position of the modified layer remaining on the separated surface; and exercising control in the modified layer removal device to execute a first removal process of irradiating the modified layer remaining on the separated surface with first laser light to remove the modified layer.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present disclosure relates to a processing system and a processing method. [Background technology]

[0002] Patent Document 1 discloses a method for processing a wafer having a plurality of devices formed on its front surface side, in which the wafer is separated and thinned using a modified layer formed inside the wafer by irradiation with laser light as a base point, and then the separated surface of the wafer is ground to remove the modified layer remaining on the separated surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO 2020 / 66492 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology according to the present disclosure appropriately removes the modified layer remaining on the peeled surface of a substrate that has been peeled off using a modified layer formed by irradiation with laser light as a base point. [Means for solving the problem]

[0005] One aspect of the present disclosure is a processing system for processing a processing object, comprising: a modified layer position acquisition device for acquiring the position of a modified layer remaining on a separation surface of a separation object separated based on a modified layer formed inside the processing object; a modified layer removal device for irradiating a laser beam onto the separation surface to remove the modified layer remaining on the separation surface; and a control device, wherein the control device controls the modified layer position acquisition device to detect the position of the modified layer remaining on the separation surface, and controls the modified layer removal device to perform a first removal process in which a first laser beam is irradiated onto the modified layer remaining on the separation surface to remove the modified layer. Effect of the Invention

[0006] According to the present disclosure, in a substrate that has been peeled off using a modified layer formed by irradiation with laser light as a base point, the modified layer remaining on the peeled surface of the substrate can be appropriately removed. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is a side view showing an outline of a configuration of an overlapping wafer. [Diagram 2] FIG. 4 is a side view showing the state after separation of the first wafer. [Diagram 3] 1 is a plan view showing a configuration example of a wafer processing system according to an embodiment of the present invention. [Figure 4] 1 is a side view showing a configuration example of a modified layer removal device according to an embodiment of the present invention. [Diagram 5] 1 is a side view showing a configuration example of a reforming separation device according to an embodiment of the present invention. [Figure 6] FIG. 2 is a flow diagram showing main steps of wafer processing according to the present embodiment. [Figure 7] 1A to 1C are explanatory diagrams of main steps of wafer processing according to the present embodiment. [Figure 8] FIG. 2 is a plan view showing a state in which an internal surface modification layer is formed on a first wafer. [Figure 9] 4 is a vertical cross-sectional view showing a state in which an internal surface modification layer is formed on a first wafer. FIG. [Figure 10] 4 is a vertical cross-sectional view showing a state of a separation surface of a separation wafer immediately after separation. FIG. [Figure 11] FIG. 4 is an explanatory diagram showing the state of removing the modified layer according to the present embodiment. [Figure 12] FIG. 11 is a flow diagram showing main steps of a wafer processing according to another embodiment. [Figure 13] FIG. 11 is an explanatory diagram showing the state of removing a modified layer according to another embodiment. [Figure 14] FIG. 11 is an explanatory diagram showing the state of removing a modified layer according to another embodiment. [Figure 15]FIG. 11 is an explanatory diagram showing the state of removing a modified layer according to another embodiment. [Figure 16] FIG. 11 is an explanatory diagram showing the state of removing a modified layer according to another embodiment. [Figure 17] FIG. 11 is an explanatory diagram showing the state of removing a modified layer according to another embodiment. [Figure 18] 10A to 10C are explanatory diagrams of main steps of a wafer processing according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] In the manufacturing process of semiconductor devices, a semiconductor wafer (hereinafter, referred to as a wafer) having a plurality of devices formed on its surface is thinned. There are various methods for thinning a wafer, such as a method of grinding the wafer by contacting a grinding wheel with the back surface of the wafer, and a method of separating the wafer using a modified layer (amorphous layer) formed by irradiating the inside of the wafer with a laser beam as a base point, as disclosed in Patent Document 1.

[0009] Here, when the wafer is thinned by separation based on the modified layer, the modified layer may remain on the separation surface of the wafer. The modified layer remaining on the separation surface may cause defects in the subsequent manufacturing steps, so it is important to remove the modified layer prior to the subsequent processing steps. As a method for removing the modified layer remaining on the separation surface, for example, as disclosed in Patent Document 1, a grinding process may be performed on the separation surface on which the modified layer remains.

[0010] However, when removing the modified layer by grinding the separation surface in this way, the modified layer may cause an increase in grinding resistance in the grinding process due to various factors such as differences in crystal structure, which may result in the modified layer not being properly removed by the grinding process. Patent Document 1 does not disclose or suggest anything about the modified layer causing an increase in grinding resistance, and therefore there is room for improvement in the conventional method for removing the modified layer.

[0011] The technology disclosed herein has been made in consideration of the above circumstances, and in a substrate that has been peeled off using a modified layer formed by irradiation with laser light as a base point, a modified layer remaining on the peeled surface of the substrate is appropriately removed. Hereinafter, a wafer processing system as a processing system according to the present embodiment and a wafer processing method as a processing method will be described with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and duplicated descriptions will be omitted.

[0012] In a wafer processing system 1 according to this embodiment, which will be described later, processing is performed on a laminated wafer T as a laminated substrate in which a first wafer W as a first substrate and a second wafer S as a second substrate are bonded together, as shown in Fig. 1. Hereinafter, in the first wafer W, the surface to be bonded to the second wafer S is referred to as the front surface Wa, and the surface opposite the front surface Wa is referred to as the back surface Wb. Similarly, in the second wafer S, the surface to be bonded to the first wafer W is referred to as the front surface Sa, and the surface opposite the front surface Sa is referred to as the back surface Sb.

[0013] The first wafer W is a semiconductor wafer such as a silicon substrate, and has a device layer Dv including a plurality of devices formed on the front surface Wa side. A surface film Fw is further formed on the front surface Wa side of the first wafer W, and the surface film Fw is bonded to a surface film Fs of the second wafer S. Examples of the surface film Fw include an oxide film (THOX film, SiO2 film, TEOS film), a SiC film, a SiCN film, or an adhesive. The peripheral portion of the first wafer W is chamfered, and the cross section of the peripheral portion has a smaller thickness toward the tip.

[0014] The second wafer S is, for example, a wafer that supports the first wafer W. A surface film Fs is formed on the surface Sa of the second wafer S. Examples of the surface film Fs include an oxide film (THOX film, SiO2 film, TEOS film), a SiC film, a SiCN film, or an adhesive. The second wafer S also functions as a protective material (support wafer) that protects the device layer Dv of the first wafer W. The second wafer S does not need to be a support wafer, and may be a device wafer in which a device layer (not shown) is formed, similar to the first wafer W.

[0015] In the drawings used in the following description, the device layer Dv and the surface films Fw and Fs may be omitted in order to avoid complication of the illustration.

[0016] In addition, in a wafer processing system 1 of this embodiment described later, as shown in FIG. 2, the first wafer W of the overlapped wafer T is separated and thinned. In the following description, the first wafer W on the separated front surface Wa side is referred to as the first separated wafer W1, and the first wafer W on the separated back surface Wb side is referred to as the second separated wafer W2. Note that the first separated wafer W1 refers to the first wafer W supported by the second wafer S, and may be referred to as the first separated wafer W1 including the second wafer S. Furthermore, the surfaces of the first separated wafer W1 and the second separated wafer W2 on the separated side may be referred to as the separated surfaces W1a and W2a, respectively.

[0017] In the following embodiments, the laminated substrate corresponds to a "processing target" according to the technology of the present disclosure, and the separated wafers W1 and W2 correspond to a "separated object" according to the technology of the present disclosure.

[0018] As shown in Fig. 3, the wafer processing system 1 has a configuration in which a loading / unloading station 2 and a processing station 3 are integrally connected. The loading / unloading station 2 and the processing station 3 are arranged side by side from the positive side to the negative side of the X-axis. The loading / unloading station 2 loads / unloads cassettes Ct, Cw1, and Cw2, each capable of accommodating a plurality of overlapped wafers T, a plurality of first separated wafers W1, and a plurality of second separated wafers W2, between the loading / unloading station 2 and the outside, for example. The processing station 3 is equipped with various processing devices that perform desired processing on the overlapped wafer T and the separated wafers W1 and W2.

[0019] The loading / unloading station 2 is provided with a cassette mounting table 10. In the illustrated example, a plurality of cassettes, for example, three cassettes Ct, Cw1, and Cw2, can be freely mounted in a row in the Y-axis direction on the cassette mounting table 10. Note that the number of cassettes Ct, Cw1, and Cw2 mounted on the cassette mounting table 10 is not limited to this embodiment and can be determined arbitrarily.

[0020] In the loading / unloading station 2, a wafer transfer area 20 is provided adjacent to the cassette mounting table 10 on the negative side of the X-axis of the cassette mounting table 10. A wafer transfer device 22 is provided in the wafer transfer area 20, which is movable on a transfer path 21 extending in the Y-axis direction. The wafer transfer device 22 has two transfer arms 23, 23 for holding and transferring the overlapped wafer T and the separated wafers W1, W2. Each transfer arm 23 is configured to be movable in the horizontal direction (X-axis direction and Y-axis direction), the vertical direction, around the horizontal axis, and around the vertical axis. The configuration of the transfer arm 23 is not limited to this embodiment, and any configuration may be used.

[0021] The processing station 3 is provided with, for example, three processing blocks G1 to G3 and a wafer transfer area 30. The first processing block G1, the second processing block G2, and the third processing block G3 are arranged in this order from the positive side of the X-axis (the load / unload station 2 side) to the negative side. The first processing block G1 is arranged on the positive side of the X-axis of the wafer transfer area 30, and the second processing block G2 and the third processing block G3 are each arranged on the positive side of the Y-axis of the wafer transfer area 30.

[0022] The wafer transport area 30 is provided with a wafer transport device 32 that is movable on a transport path 31 extending in the X-axis direction. The wafer transport device 32 is configured to be capable of transporting the overlapped wafer T and the separated wafers W1 and W2 to each of the processing devices in the processing blocks G1 to G3. The wafer transport device 32 also has two transport arms 33, 33 that hold and transport the overlapped wafer T and the separated wafers W1 and W2. Each transport arm 33 is supported by an articulated arm member 34 and is configured to be movable in the horizontal direction, the vertical direction, around a horizontal axis, and around a vertical axis. The configuration of the transport arm 33 is not limited to this embodiment, and any configuration may be used.

[0023] The first processing block G1 is provided with two wet etching apparatuses 40, 40, two cleaning apparatuses 50, 50, a buffer apparatus 60, and a modified separation apparatus 70. The wet etching apparatus 40, the cleaning apparatus 50, and the buffer apparatus 60 are arranged in this order from the positive side to the negative side of the Y axis. The two wet etching apparatuses 40, 40 are arranged in a stacked manner. The two cleaning apparatuses 50, 50 are arranged in a stacked manner. In addition, the buffer apparatus 60 and the modified separation apparatus 70 are arranged in a stacked manner.

[0024] In the second processing block G2, a reversing device 80 and a modified layer removing device 90 are stacked in this order from above.

[0025] In the third processing block G3, a processing device 100 is provided.

[0026] The two wet etching devices 40 etch the separation surfaces W1a and W2a of the separated wafers W1 and W2 ground by the processing device 100. For example, a chemical solution (etching solution) is supplied to the separation surfaces W1a and W2a of the separated wafers W1 and W2. For example, HF, HNO3, H3PO4, TMAH, Choline, KOH, etc. are used as the chemical solution.

[0027] The two cleaning devices 50 respectively clean the separation surfaces W1a, W2a of the separated wafers W1, W2 ground by the processing device 100. For example, a brush is brought into contact with the separation surfaces W1a, W2a to scrub the separation surfaces W1a, W2a. Note that a pressurized cleaning liquid may be used to clean the separation surfaces W1a, W2a.

[0028] The buffer device 60 temporarily holds the unprocessed overlapped wafer T transferred from the wafer transfer region 20 to the wafer transfer region 30. The buffer device 60 may be configured to adjust the horizontal orientation of the overlapped wafer T by detecting the position of a notch portion of the first wafer W with a detection unit (not shown) while rotating the overlapped wafer T held by a chuck (not shown), for example. Furthermore, the buffer device 60 may be configured to detect the surface state by imaging the separation surfaces W1a, W2a of the separated wafers W1, W2 separated by the modified separation device 70, as described later. In such a case, the buffer device 60 functions as a modified layer position acquisition device according to the technology of the present disclosure.

[0029] The modification separation apparatus 70, which functions as a separation apparatus, irradiates laser light into the inside of the first wafer W to form an internal surface modification layer, which will be described later, and further separates the first wafer W into a first separated wafer W1 and a second separated wafer W2 based on the internal surface modification layer.

[0030] The modified separation apparatus 70 has a chuck 71 that holds the overlapped wafers T with the first wafer W placed on top and the second wafer S placed on the bottom as shown in Fig. 4. The chuck 71 is configured to be movable in the X-axis direction and / or the Y-axis direction by a moving unit 72. The moving unit 72 is configured as a precision XY stage, for example. The chuck 71 is also configured to be rotatable around a vertical axis by a rotating unit 73.

[0031] A laser head 74 is provided above the chuck 71, which irradiates the inside of the first wafer W with laser light. The laser head 74 irradiates a desired position inside the first wafer W with a high-frequency pulsed laser light (e.g., YAG laser) oscillated from a laser light oscillator (not shown) and having a wavelength that is transparent to the first wafer W. As a result, the portion inside the first wafer W where the laser light is focused is modified, and an internal surface modified layer is formed. The laser head 74 is configured to be movable in the X-axis direction and / or the Y-axis direction by a moving unit 75. The moving unit 75 is configured, for example, as a precision XY stage. The laser head 74 is also configured to be movable in the Z-axis direction by a lifting unit 76.

[0032] In addition, a suction pad 77 that suction-holds the back surface Wb of the first wafer W is provided above the chuck 71. The suction pad 77 is configured to be rotatable about a vertical axis by a rotating unit 78. The suction pad 77 is configured to be movable in the Z-axis direction by a lifting unit 79.

[0033] In addition, the modification separation apparatus 70 may be configured to be able to acquire the position of an internal surface modification layer formed inside the first wafer W, or the position of an internal surface modification layer remaining on the separation surfaces of the separated wafers W1 and W2, for example, by imaging the polymerized wafer T held on the chuck 71 with an imaging mechanism (not shown), such as a CCD camera.

[0034] The reversing device 80 reverses the front and back surfaces of the second separated wafer W2 separated by the modified separation device 70. The reversing device 80 may have any configuration.

[0035] The two modified layer removal devices 90 each irradiate laser light onto the separation surfaces W1a, W2a of the separated wafers W1, W2 separated by the modified separation device 70, and remove the internal surface modified layers described below that remain on the separation surfaces W1a, W2a prior to the grinding process in the processing device 100.

[0036] The modified layer removing device 90 has a chuck 91 that holds the first separated wafer W1 with the separation surface W1a on the upper side and the back surface Sb of the second wafer S on the lower side, as shown in FIG. 5. The chuck 91 is configured to be movable in the X-axis direction and / or the Y-axis direction by a moving unit 92. The moving unit 92 is configured as a precision XY stage, for example. The chuck 91 is also configured to be rotatable about a vertical axis by a rotating unit 93. When removing the modified layer remaining on the separation surface W2a of the second separated wafer W2 in the modified layer removing device 90, the chuck 91 holds the second separated wafer W2 with the separation surface W2a on the upper side and the back surface Wb of the first wafer W on the lower side.

[0037] A laser head 94 is provided above the chuck 91, which irradiates the separation surfaces W1a, W2a of the separation wafers W1, W2 with laser light. The laser head 94 irradiates a high-frequency pulsed laser light (for example, an ultrashort pulse laser such as a picosecond laser or a femtosecond laser) oscillated from a laser light oscillator (not shown) to a desired position (a remaining position of the modified layer) of the separation surfaces W1a, W2a of the separation wafers W1, W2. This removes the modified layer remaining in the portion where the laser light is focused on the separation surfaces W1a, W2a of the separation wafers W1, W2 by ablation processing. The laser head 94 is configured to be movable in the X-axis direction and / or the Y-axis direction by a moving unit 95, and is configured to be able to arbitrarily adjust the irradiation position of the laser light on the separation surfaces W1a, W2a by, for example, a galvano scanner. The moving unit 95 is configured as a precision XY stage, for example. The laser head 94 is also configured to be movable in the Z-axis direction by an elevator unit 96.

[0038] The laser head 94 may further include a spatial light modulator (not shown). The spatial light modulator modulates and outputs the laser light. Specifically, the spatial light modulator can control the focal position and phase of the laser light, and can adjust the shape and number (number of branches) of the irradiated laser light. At this time, the branched and irradiated laser light is configured so that the output, etc., of each branch can be adjusted. As the spatial light modulator, for example, LCOS (Liquid Crystal Silicon) can be selected.

[0039] The modified layer removal device 90 also has an imaging mechanism 97 that captures images of the separation surfaces W1a, W2a of the separated first wafer W (separated wafers W1, W2) to detect the surface condition. For example, a CCD camera or the like can be used as the imaging mechanism 97. Then, based on the surface condition of the separation surfaces W1a, W2a obtained from the imaging results by the imaging mechanism 97, for example, the position of the internal surface modified layer remaining on the separation surfaces W1a, W2a, the amount of displacement of the separation surfaces W1a, W2a, etc., which will be described later, can be obtained.

[0040] 3, the processing apparatus 100 grinds the separated surface W1a of the first separated wafer W1 and the separated surface W2a of the second separated wafer W2. The processing apparatus 100 includes a rotary table 110, a first grinding unit 120, and a second grinding unit .

[0041] The turntable 110 is configured to be freely rotatable about a vertical rotation center line 111 by a rotation mechanism (not shown). Four chucks 112 for suction-holding the separated wafers W1, W2 are provided on the turntable 110. The chucks 112 are arranged evenly on the same circumference as the turntable 110, i.e., at 90 degree intervals. The four chucks 112 are movable to delivery positions A1, A2 and processing positions B1, B2 by the rotation of the turntable 110. Each chuck 112 is held by a chuck base (not shown) and configured to be rotatable by a rotation mechanism (not shown).

[0042] In this embodiment, the first transfer position A1 is a position on the negative X-axis and negative Y-axis sides of the turntable 110, where the first separated wafer W1 is transferred. The second transfer position A2 is a position on the positive X-axis and negative Y-axis sides of the turntable 110, where the second separated wafer W2 is transferred. The first processing position B1 is a position on the positive X-axis and positive Y-axis sides of the turntable 110, where the first grinding unit 120 is disposed. The second processing position B2 is a position on the negative X-axis and positive Y-axis sides of the turntable 110, where the second grinding unit 130 is disposed.

[0043] In the first grinding unit 120, the separation surface W1a of the first separated wafer W1 is ground. The first grinding unit 120 has a first grinding section 121 equipped with a grinding wheel (not shown) that is annular and rotatable. The first grinding section 121 is configured to be movable in the vertical direction along a support 122. Then, while the separation surface W1a of the first separated wafer W1 held by the chuck 112 is in contact with the grinding wheel, the chuck 112 and the grinding wheel are rotated, and the grinding wheel is lowered to grind the separation surface W1a of the first separated wafer W1. This reduces the thickness of the first separated wafer W1 to a preset thickness, and flattens the separation surface W1a of the first separated wafer W1.

[0044] In the second grinding unit 130, the separation surface W2a of the second separated wafer W2 is ground. The second grinding unit 130 has a second grinding section 131 equipped with a grinding wheel (not shown) that is annular and rotatable. The second grinding section 131 is configured to be movable in the vertical direction along a support 132. Then, while the separation surface W2a of the second separated wafer W2 held by the chuck 112 is in contact with the grinding wheel, the chuck 112 and the grinding wheel are rotated, and the grinding wheel is lowered to grind the separation surface W2a of the second separated wafer W2. This reduces the thickness of the second separated wafer W2 to a preset thickness, and flattens the separation surface W2a of the second separated wafer W2.

[0045] The above-described wafer processing system 1 is provided with a control device 140. The control device 140 is, for example, a computer, and has a program storage unit (not shown). The program storage unit stores a program for controlling the processing of the laminated wafer T in the wafer processing system 1. The program storage unit also stores a program for controlling the operation of the drive systems of the above-described various processing devices and transport devices, and for realizing wafer processing, which will be described later, in the wafer processing system 1. The above-described program may be recorded in a computer-readable storage medium and installed in the control device 140 from the storage medium. The above-described storage medium may be temporary or non-temporary.

[0046] Next, a description will be given of wafer processing performed using the wafer processing system 1 configured as above. In this embodiment, the first wafer W and the second wafer S are bonded together to form an overlapped wafer T in advance.

[0047] First, a cassette Ct storing a plurality of overlapped wafers T is placed on the cassette placement stage 10 of the carry-in / out station 2. Next, the overlapped wafers T in the cassette Ct are taken out by the wafer transfer device 22 and transferred to the buffer device 60. In the buffer device 60, the horizontal orientation of the overlapped wafers T (first wafer W) may be adjusted.

[0048] Next, the laminated wafer T is transported to the modified separation apparatus 70 by the wafer transport device 32. In the modified separation apparatus 70, an internal surface modified layer M1 is formed inside the first wafer W as shown in Fig. 7(a) (step P1 in Fig. 6). The internal surface modified layer M1 serves as a base point when the first wafer W is separated into a first separated wafer W1 and a second separated wafer W2.

[0049] Specifically, as shown in FIG. 8, the chuck 71 (overlapped wafer T) is rotated by the rotating unit 73, and the overlapped wafer T and the laser head 74 are moved horizontally relative to each other to form a plurality of inner surface modified layers M1, for example, in a spiral shape in a cross-sectional view, inside the first wafer W. These inner surface modified layers M1 are formed at the same height inside the first wafer W. Then, the inner surface modified layers M1 are formed on the entire inner surface of the first wafer W. Here, the inner surface modified layers M1 are formed at a circumferential interval P (pulse pitch) and a radial interval Q (index pitch). The circumferential interval P (pulse pitch) and the radial interval Q (index pitch) may be changed midway, that is, the circumferential interval P (pulse pitch) and / or the radial interval Q (index pitch) may be different between the outer circumference and the inner circumference of the first wafer W.

[0050] In FIG. 8, the dashed arrow indicates the movement trajectory of the position of the laser head 74 relative to the first wafer W (the irradiation position of the laser light L), and the open circle within the surface of the first wafer W indicates the formed internal surface modified layer M1.

[0051] The internal surface modified layer M1 is formed by irradiating the inside of the first wafer W with laser light L from the laser head 74 as shown in Fig. 9. The lower end of the internal surface modified layer M1 is located above the target surface (dotted line in Fig. 9) of the first wafer W after grinding in the processing apparatus 100. In addition, a crack C1 propagates from the internal surface modified layer M1 in the surface direction.

[0052] After the internal surface modification layer M1 is formed inside the first wafer W, the first wafer W is subsequently separated into a first separated wafer W1 and a second separated wafer W2 using the internal surface modification layer M1 as a base point, as shown in FIG. 7(b) (step P2 in FIG. 6). Specifically, in the modification separation device 70, the back surface Wb of the first wafer W is suction-held by an adsorption pad 77. Thereafter, the adsorption pad 77 is raised to separate the second separated wafer W2 from the first separated wafer W1. At this time, the adsorption pad 77 may be rotated to separate the first separated wafer W1 and the second separated wafer W2 at the internal surface modification layer M1 as a boundary.

[0053] As shown in FIG. 7(b) and FIG. 10, an inner surface modification layer M1 remains on the separation surface W1a of the first separated wafer W1 and the separation surface W2a of the second separated wafer W2, respectively.

[0054] Here, the processing apparatus 100 performs a grinding process on the separation surfaces W1a, W2a, but if an internal surface modification layer M1 remains on the separation surfaces W1a, W2a in this manner, the internal surface modification layer M1 may cause an increase in grinding resistance in the grinding process, and there is a risk that the grinding process may not be performed properly. 8 and 9, modified (amorphous) parts directly irradiated with the laser light L and non-modified (single crystal) parts not irradiated with the laser light L are mixed in the surface of the first wafer W after it is irradiated with the laser light L. In this case, a difference in grinding resistance occurs between the modified and non-modified parts due to the difference in crystal structure, and from this viewpoint, there is a risk that the grinding process cannot be performed appropriately.

[0055] Therefore, in the wafer processing system 1 according to the present embodiment, the internal surface modified layer M1 remaining on the separation surfaces W1a, W2a is removed in this manner prior to the grinding process in the processing device 100. Specifically, the internal surface modified layer M1 to be removed is irradiated with an ultrashort pulse laser (for example, a picosecond laser or a femtosecond laser), thereby removing the internal surface modified layer M1 by ablation processing.

[0056] After the first wafer W is separated into the first separated wafer W1 and the second separated wafer W2, the first separated wafer W1 is then transported to the modified layer removing device 90 by the wafer transport device 32. In the modified layer removing device 90, the separation surface W1a of the first separated wafer W1 is first imaged, and the remaining position of the inner surface modified layer M1 on the separation surface W1a is detected (step P3 in FIG. 6). At this time, the chuck 91 may be rotated to adjust the horizontal orientation of the first separated wafer W1.

[0057] In parallel with step P3, the second separated wafer W2 is transferred to the reversing device 80 by the wafer transfer device 32. In the reversing device 80, the front and back surfaces of the second separated wafer W2 are reversed (step P4 in FIG. 6).

[0058] The second separated wafer W2 with the front and back sides inverted is transferred to the modified layer removing device 90 by the wafer transfer device 32. In the modified layer removing device 90, the separation surface W2a of the second separated wafer W2 is first imaged, and the remaining position of the inner surface modified layer M1 on the separation surface W2a is detected (step P5 in FIG. 6). At this time, the chuck 91 may be rotated to adjust the horizontal orientation of the second separated wafer W2.

[0059] In this embodiment, the remaining position of the internal surface modified layer M1 is detected based on the imaging results of the separation surfaces W1a, W2a by the imaging mechanism 97 as shown in steps P3 and P5, but the remaining position of the internal surface modified layer M1 can be obtained by any method. Specifically, for example, instead of imaging the separation surfaces W1a, W2a of the separation wafers W1, W2, the formation position of the internal surface modified layer M1 may be detected by imaging the back surface Wb of the first wafer W before separation. Also, for example, instead of imaging by the imaging mechanism 97, the formation position of the internal surface modified layer M1 may be obtained by prediction based on the process recipe (formation conditions of the internal surface modified layer M1) in the modification separation device 70. Furthermore, the detection position for the remaining position of the internal surface modified layer M1 is not limited to the modified layer removal device 90, and the remaining position may be detected by the modified separation device 70, the inversion device 80, or the buffer device 60, or an independent modified layer position acquisition device (not shown) may be arranged in the wafer processing system 1.

[0060] After the separation surfaces W1a and W2a of the separated wafers W1 and W2 are imaged, the internal surface modification layer M1 remaining on the separation surfaces W1a and W2a of the separated wafers W1 and W2 is removed (step P6 in FIG. 6) as shown in FIG. 7(c) and FIG. 7(d). Specifically, as shown in FIG. 11, the internal surface modification layer M1 remaining on the separation surfaces W1a and W2a is irradiated with laser light L to remove the internal surface modification layer M1 by ablation processing.

[0061] Here, when the internal surface modified layer M1 remaining on the separation surfaces W1a and W2a is removed by irradiating the laser light, a new modified layer (damaged layer) may be formed by the irradiation of the laser light, and the newly formed modified layer may prevent the grinding process from being properly performed in the processing device 100. For this reason, in this embodiment, in order to suppress the formation of a new modified layer by the laser light irradiated to remove the internal surface modified layer M1, the laser light is irradiated under processing conditions with small thermal effects so that a new modified layer is not formed, or even if it is formed, it can be properly removed by the grinding process.

[0062] In addition, in order to properly remove the remaining internal surface modified layer M1 without forming a new modified layer on the separation surfaces W1a and W2a, the modified layer removal device 90 may repeatedly irradiate the laser light L under the processing conditions with small thermal effects described above until the desired amount of removal of the internal surface modified layer M1 is obtained.

[0063] In addition, in the internal surface modification layer M1 (amorphous layer) remaining on the separation surfaces W1a and W2a, the crystal structure of the internal surface modification layer M1 may change due to changes in the irradiation conditions of the laser light (e.g., the frequency and output of the laser light) during the formation of the internal surface modification layer M1 in step P1. If the crystal structure of the internal surface modification layer M1 changes in this way, this may cause a change in the irradiation conditions of the laser light required to remove the internal surface modification layer M1.

[0064] Therefore, in removing the internal surface modified layer M1 in step P6, the irradiation conditions of the laser light from the laser head 74 may be changed in accordance with the irradiation conditions of the laser light when the internal surface modified layer M1 is formed in step P1. In other words, the irradiation conditions of the laser light when the internal surface modified layer M1 is formed may be fed forward to the irradiation conditions of the laser light when the internal surface modified layer M1 is removed, and the irradiation conditions of the laser light in the removal process of the internal surface modified layer M1 may be changed.

[0065] The modified layer removal process according to the embodiment is performed as described above. Next, the first separated wafer W1 having undergone the modified layer removal process is transferred to the processing apparatus 100 by the wafer transfer device 32 and delivered to the chuck 112 at the first delivery position A1. At the same time, the second separated wafer W2 is inverted in the inversion device 80, and then transferred to the processing apparatus 100 by the wafer transfer device 32 and delivered to the chuck 112 at the second delivery position A2.

[0066] Next, the turntable 110 is rotated 180° about the vertical axis to move the first separated wafer W1 to the first processing position B1, and the second separated wafer W2 to the second processing position B2.

[0067] Next, at the first processing position B1, the separation surface W1a of the first separated wafer W1 is ground to flatten the separation surface W1a and reduce the thickness of the first separated wafer W1 to a target thickness (step P7 in FIG. 6), as shown in FIG. 7(e) and FIG. 11(c). At the same time, at the second processing position B2, the separation surface W2a of the second separated wafer W2 is ground to flatten the separation surface W2a. According to this embodiment, the inner surface modified layer M1 remaining on the separation surfaces W1a, W2a of the separated wafers W1, W2 is removed by the modified layer removal process in step P6. This suppresses an increase in grinding resistance caused by the remaining inner surface modified layer M1, and allows the grinding units 120, 130 to appropriately grind the separation surfaces W1a, W2a.

[0068] Next, the turntable 110 is rotated 180° around the vertical axis to move the first separated wafer W1 to the first transfer position A1, and the second separated wafer W2 to the second transfer position A2. At the first transfer position A1, the separated surface W1a of the first separated wafer W1 may be cleaned with a cleaning liquid using a cleaning liquid nozzle (not shown). At the second transfer position A2, the separated surface W2a of the second separated wafer W2 may be cleaned with a cleaning liquid using a cleaning liquid nozzle (not shown).

[0069] Next, the first separated wafer W1 is transferred to one cleaning apparatus 50 by the wafer transfer apparatus 32, and the second separated wafer W2 is transferred to the other cleaning apparatus 50 by the wafer transfer apparatus 32. In the cleaning apparatus 50, the separated surfaces W1a and W2a of the separated wafers W1 and W2 are scrubbed and cleaned, respectively (step P8 in FIG. 6).

[0070] Next, the first separated wafer W1 is transferred by the wafer transfer device 22 to one wet etching device 40, and the second separated wafer W2 is transferred by the wafer transfer device 22 to the other wet etching device 40. In the wet etching device 40, the separated surfaces W1a, W2a of the separated wafers W1, W2 are wet etched with a chemical solution (step P9 in FIG. 6). Grinding marks may be formed on the separated surfaces W1a, W2a ground by the above-mentioned processing device 100. In this step P9, the grinding marks can be removed by wet etching, and the separated surfaces W1a, W2a can be smoothed.

[0071] Thereafter, the first separated wafer W1 and the second separated wafer W2 that have been subjected to all the processes are respectively transferred by the wafer transfer device 22 to the cassettes Cw1 and Cw2 on the cassette mounting table 10. In this manner, a series of wafer processes in the wafer processing system 1 is completed. The first separated wafer W1 having the device layer Dv is commercialized. The second separated wafer W2 is, for example, reused.

[0072] According to the above embodiment, prior to grinding the separation surfaces W1a, W2a of the separated wafers W1, W2, the inner surface modified layer M1 remaining on the separation surfaces W1a, W2a is removed by irradiating the inner surface modified layer M1 with a laser beam, thereby suppressing an increase in grinding resistance caused by the inner surface modified layer M1, and allowing the separation surfaces W1a, W2a to be appropriately ground.

[0073] In addition, by removing the internal surface modification layer M1 at this time, the crystal structure of the separation surfaces W1a, W2a to be ground is prevented from being a mixture of single crystal parts and amorphous parts, and the grinding of the separation surfaces W1a, W2a can be carried out more appropriately.

[0074] In addition, when the internal surface modification layer M1 is removed by irradiating the laser light as shown in the above embodiment, as shown in FIG. 11(b), unevenness may be formed on the separation surfaces W1a, W2a after the removal of the internal surface modification layer M1, and the surface accuracy may be reduced. If the surface accuracy of the separation surfaces W1a, W2a is reduced in this way, the grinding resistance may increase, and even if the internal surface modification layer M1 is properly removed, the grinding process in the processing device 100 may not be properly performed. Therefore, in the wafer processing system 1 according to this embodiment, in addition to removing the internal surface modification layer M1 described above, a flattening process may be performed on the separation surfaces W1a, W2a whose surface accuracy has been reduced by irradiating the laser light. In the following description, "planarization" refers to a process of improving the surface precision (surface roughness) of the separation surfaces W1a, W2a of the first wafer W (separated wafers W1, W2) after separation in the modified separation apparatus 70, thereby reducing the grinding resistance during the grinding process in the processing apparatus 100 described below.

[0075] Hereinafter, a wafer processing method for planarizing the separation surfaces W1a and W2a in addition to removing the inner surface modification layer M1 will be described. In the following description, detailed descriptions of steps in which substantially the same processing as in the above embodiment is performed will be omitted.

[0076] First, in a manner similar to steps P1 and P2 of FIG. 6 described above, an internal surface modification layer M1 is formed inside the first wafer W, and the first wafer W is separated using the internal surface modification layer M1 as a base point (steps Q1 and Q2 of FIG. 12).

[0077] After the first wafer W is separated into the first separated wafer W1 and the second separated wafer W2, the first separated wafer W1 is then transported to the modified layer removing device 90 by the wafer transport device 32. In the modified layer removing device 90, the separation surface W1a of the first separated wafer W1 is first imaged, and the remaining position of the inner surface modified layer M1 on the separation surface W1a is detected (step Q3 in FIG. 12). At this time, the chuck 91 may be rotated to adjust the horizontal orientation of the first separated wafer W1.

[0078] In step Q3, in addition to detecting the remaining positions of the internal surface modification layer M1, the displacement amount H of the uneven portion formed on the separation surface W1a by the irradiation of the laser light is calculated. The convex portion in the uneven portion corresponds to the non-modified portion not irradiated with the laser light in step Q1. The concave portion in the uneven portion corresponds to the modified portion irradiated with the laser light in step Q1. The displacement amount H of the convex portion can be calculated based on the distance between adjacent concave portions (the radial distance Q of the internal surface modification layer M1 shown in FIG. 8) obtained by imaging the separation surfaces W1a, W2a of the separation wafers W1, W2, for example.

[0079] In parallel with this, the second separated wafer W2 is transferred to the reversing device 80 by the wafer transfer device 32. In the reversing device 80, the front and back surfaces of the second separated wafer W2 are reversed (Step Q4 in FIG. 12).

[0080] The second separated wafer W2, whose front and back sides have been inverted, is transferred to the modified layer removing device 90 by the wafer transfer device 32. The modified layer removing device 90 first captures an image of the separated surface W2a of the second separated wafer W2 and detects the remaining position of the inner surface modified layer M1 on the separated surface W2a. The modified layer removing device 90 further acquires the displacement amount H of the uneven portion of the separated surface W2a (step Q5 in FIG. 12). At this time, the chuck 91 may be rotated to adjust the horizontal orientation of the second separated wafer W2.

[0081] Next, in the same modified layer removal device 90, the inner surface modified layer M1 remaining on the separation surfaces W1a, W2a of the separated wafers W1, W2 is removed, and the separation surfaces W1a, W2a, the surface accuracy of which has been reduced by the irradiation of the laser beam, are flattened.

[0082] Specifically, first, as shown in Fig. 13(a), the first laser light L is irradiated toward the inner surface modified layer M1 remaining on the separation surfaces W1a and W2a, and the inner surface modified layer M1 is removed by ablation processing as shown in Fig. 13(b) (Step Q6 in Fig. 12: first removal processing). At this time, the irradiation conditions of the first laser light L are set to processing conditions with small thermal effects so that a new modified layer is not formed, or even if it is formed, it can be appropriately removed by grinding processing.

[0083] Next, the second laser light L is irradiated to the convex portion D (corresponding to the single crystal portion that is the non-irradiated position of the laser light in step Q1) having a large displacement amount H among the uneven portions formed on the separation surfaces W1a, W2a after removing the internal surface modification layer M1 (step Q7 in FIG. 12). As a result, the displacement amount H1 in the convex portion D is made to substantially coincide with the displacement amount H2 of the separation surfaces W1a, W2a in the portion where the internal surface modification layer M1 has been removed as shown in FIG. 13(c), that is, the surface accuracy of the separation surfaces W1a, W2a is improved (second removal process). Note that the displacement amount H1 substantially coincides with the displacement amount H2 refers to a state in which the surface accuracy is improved (flattened) so that an increase in grinding resistance caused by the formation of the uneven portions in the processing device 100 can be at least suppressed.

[0084] As in the first removal process, it is desirable to set the irradiation conditions of the second laser beam L to processing conditions that have a small thermal effect so as not to form a new modified layer. However, when the amount of removal of the convex portion D is particularly large, that is, when the difference between the displacement amount H1 and the displacement amount H2 is large, the convex portion needs to be irradiated with a high-power laser beam, and as shown in FIG. 13(c), a new modified layer may be formed on the separation surfaces W1a and W2a after the removal of the convex portion D.

[0085] Next, the first separated wafer W1 and the second separated wafer W2 are transported to the processing apparatus 100 by the wafer transport device 32. In the processing apparatus 100, the separation surface W1a of the first separated wafer W1 is ground to reduce the separation surfaces W1a and W2a to the target surfaces as shown in FIG. 13(d), and the surface accuracy of the separation surfaces W1a and W2a is further improved (step Q8 in FIG. 12). Furthermore, if the internal surface modification layer M1 on the separation surfaces W1a and W2a has not been completely removed as shown in FIG. 13(c), the internal surface modification layer M1 is completely removed by grinding.

[0086] According to this embodiment, prior to the grinding process in the processing apparatus 100, the internal surface modified layer M1 remaining on the separation surfaces W1a, W2a is removed in step Q6, and the separation surfaces W1a, W2a are planarized in step Q7. That is, prior to the grinding process, factors that cause an increase in grinding resistance in the grinding process are removed, so that the grinding process on the separation surfaces W1a, W2a can be appropriately performed.

[0087] The subsequent processes are the same as those in the above embodiment (steps P8 and P9 in FIG. 6). That is, the ground separated wafers W1 and W2 are sequentially cleaned in the cleaning apparatus 50 and etched in the wet etching apparatus 40 (steps Q9 and Q10 in FIG. 12).

[0088] In this embodiment, the same effects as those of the above embodiment can be obtained. Moreover, according to this embodiment, the separation surfaces W1a, W2a are planarized prior to the grinding process, so that the grinding process of the separation surfaces W1a, W2a in the processing apparatus 100 can be more appropriately performed.

[0089] In the example shown in Figures 12 and 13, the removal of the internal surface modification layer M1 (step Q6) was performed as the first removal process, followed by the removal of the convex portion D (step Q7) as the second removal process, but the second removal process (step Q7) may be performed prior to the first removal process (step Q6).

[0090] In the above description, the case has been described where, after the internal surface modification layer M1 remaining on the separation surfaces W1a, W2a is removed, the displacement amount H of the separation surfaces W1a, W2a is reduced to the target surface by a grinding process in the processing device 100. However, the displacement amount H of the separation surfaces W1a, W2a may be reduced to the target surface by irradiation with laser light (ablation processing) instead of the grinding process.

[0091] Specifically, for example, an ultrashort pulse laser (e.g., a picosecond laser or a femtosecond laser) is irradiated onto the separation surfaces W1a, W2a after removal of the internal surface modification layer M1 and the uneven portion shown in Figure 13(c), and the separation surfaces W1a, W2a are removed down to the target surface by ablation processing. At this time, in order to omit the grinding process for the separation surfaces W1a, W2a, it is desirable to irradiate the separation surfaces W1a, W2a with the laser light L under processing conditions that have a small thermal effect so that a new damaged layer is not formed by the irradiation of the laser light L.

[0092] Even in the case where the displacement amount H is reduced to the target surface by irradiating laser light instead of grinding, the removal of the convex portion D (step Q7) can be performed prior to the removal of the internal surface modification layer M1 (step Q6).

[0093] Specifically, first, as shown in Fig. 14(a), for example, a laser beam L is irradiated onto the convex portion D formed on the separation surfaces W1a and W2a, and as shown in Fig. 14(b), the displacement amount H1 at the convex portion D is made to substantially coincide with the displacement amount H3 at the concave portion (between adjacent convex portions D and D). Next, a first laser beam L is irradiated onto the internal surface modification layer M1 remaining on the separation surfaces W1a and W2a, and as shown in Fig. 14(c), the displacement amount H over the entire surface of the separation surfaces W1a and W2a is reduced to the target surface, and the remaining internal surface modification layer M1 is removed.

[0094] In the example shown in Fig. 13 or 14, the displacement amount H of the separation surfaces W1a and W2a was approximately equal to the displacement amount H2 after the removal of the internal surface modification layer M1 (see Fig. 13) or the displacement amount H3 in the recess (see Fig. 14), and then the laser light was further irradiated to reduce the displacement amount H to the target surface. In other words, in the example shown in Fig. 13 or 14, a removal process for making the displacement amounts H of the separation surfaces W1a and W2a equal to each other and a removal process for reducing the displacement amount H to the target surface were performed in sequence. However, the method of the removal process for the separation surfaces W1a and W2a is not limited to this, and any method can be used.

[0095] Specifically, for example, laser light L may be irradiated onto the convex portions D of the separation surfaces W1a and W2a as shown in FIG. 15(a), and the displacement amount H1 at the convex portions D may be reduced to the target surface as shown in FIG. 15(b), and then laser light L may be irradiated onto the concave portions (internal surface modification layer M1) to reduce the displacement amount H3 at the concave portions to the target surface as shown in FIG. 15(c). Naturally, the displacement amount H3 in the recessed portion may be reduced to the target surface, and then the displacement amount H1 in the protruding portion D may be reduced to the target surface.

[0096] Furthermore, when the displacement amount H is reduced to the target surface by irradiating the laser light in this manner, in order to make the displacement amount H reach the target surface without forming a new modified layer on the separation surfaces W1a and W2a, the irradiation of the laser light L under the irradiation conditions with small thermal effects described above may be repeatedly performed until the displacement amount H reaches the target surface.

[0097] In order to properly remove the inner surface modification layer M1 remaining on the separation surfaces W1a and W2a and to flatten the separation surfaces W1a and W2a (removal of uneven parts), it is necessary to adjust the energy amount of the irradiated laser light according to the crystal structure and profile of the separation surfaces W1a and W2a. That is, it is necessary to irradiate the laser light with high output to the parts where the crystal structure is single crystal or the parts where the displacement amount H is large (convex parts), and with low output to the parts where the crystal structure is amorphous or the parts where the displacement amount H is small (concave parts). However, since it takes time (about 0.5 to 1.0 seconds) to change the output of the laser light irradiated from the laser head 94, if the output is changed sequentially according to the profile of the separation surfaces W1a and W2a, it takes a long time to flatten the entire surface of the separation surfaces W1a and W2a.

[0098] Therefore, in this embodiment, in order to reduce the number of times the laser light output is changed and thereby shorten the time required to remove and flatten the internal surface modification layer M1 of the separation surfaces W1a and W2a, if the laser head 94 has the above-mentioned spatial light modulator (e.g., LCOS), the laser light may be split into multiple beams.

[0099] Specifically, as shown in Fig. 16, a spatial light modulator splits the laser light L into multiple beams (two beams in the illustrated example), and the laser light L is irradiated simultaneously to multiple points on the separation surfaces W1a and W2a. More specifically, a first laser light is irradiated simultaneously to multiple convex portions D to perform the first removal process described above, and then a second laser light is irradiated simultaneously to multiple points on the separation surfaces W1a and W2a to perform the second removal process described above. This makes it possible to increase the area over which the inner surface modification layer M1 can be removed or planarized at one time, and to shorten the time required for these processes.

[0100] In addition, in Figure 16, an example is shown in which multiple first laser beams L branched by a spatial light modulator are irradiated simultaneously onto multiple convex portions D, and multiple second laser beams are irradiated simultaneously onto separation surfaces W1a and W2a. However, as shown in Figure 17, laser beam L may be irradiated simultaneously onto convex portion D and adjacent concave portion (internal surface modification layer M1), thereby simultaneously removing the above-mentioned convex portion (first removal process) and removing the remaining internal surface modification layer M1 (second removal process).

[0101] More specifically, as shown in Fig. 17, the first laser light is irradiated onto the convex portion D while moving the laser head 94, and the second laser light is irradiated onto the separation surfaces W1a and W2a so as to follow the irradiation of the first laser light onto the convex portion D. That is, in the example shown in Fig. 16, after the first laser light L is irradiated onto the convex portion D, the output of the laser light is changed, and then the second laser light is irradiated onto the separation surfaces W1a and W2a (internal surface modification layer M1), but in the example shown in Fig. 17, the second laser light is irradiated onto the separation surfaces W1a and W2a immediately after the irradiation of the first laser light onto the convex portion D. As a result, the first removal process and the second removal process are performed approximately simultaneously without changing the output of the laser light L.

[0102] In this case, it is preferable to independently control the output of the first laser light L to the protrusion D and the output of the second laser light L to the internal surface modification layer M1. This allows the first and second removal processes to be performed simultaneously as described above, so that the entire separation surfaces W1a and W2a can be treated without changing the output of the laser light, which means that the time required for these processes can be further appropriately shortened.

[0103] Here, the peripheral portion of the first wafer W is usually chamfered, but if an internal surface modification layer M1 is formed on the entire surface of the first wafer W and then separation is performed as shown in Fig. 7, the peripheral portion of the first wafer W will have a sharply pointed shape (a so-called knife edge shape). This may cause chipping at the peripheral portion of the first wafer W, which may damage the first wafer W. Therefore, a so-called edge trim may be performed to remove the peripheral portion of the first wafer W before the grinding process.

[0104] Therefore, edge trimming may be performed in the wafer processing system 1 of the above embodiment. Hereinafter, a description will be given of wafer processing according to another embodiment, which is performed using the wafer processing system 1. Note that in this embodiment, detailed description of processing similar to that in the above embodiment will be omitted.

[0105] The overlapped wafer T is transported to the modified separation apparatus 70 by the wafer transport apparatus 32. In the modified separation apparatus 70, a peripheral modified layer M2 and an inner surface modified layer M1 are sequentially formed inside the first wafer W, as shown in Fig. 18(b) and Fig. 18(c).

[0106] The peripheral modified layer serves as a base point for removing the peripheral portion We in edge trimming, and is formed in a ring shape along the boundary between the peripheral portion We and the central portion Wc to be removed in the first wafer W. Furthermore, inside the first wafer W, a crack C2 has developed from the peripheral modified layer M2 and reached the front surface Wa. However, the crack C2 has not yet reached the back surface Wb.

[0107] The inner surface modified layer M1 is formed in the surface direction from the center to the peripheral modified layer M2, that is, in the central portion Wc. The inner surface modified layer M1 is formed in the same manner as in the above embodiment (step P1 in FIG. 6).

[0108] Next, in the same modified separation apparatus 70, the first wafer W is separated into a first separated wafer W1 and a second separated wafer W2 using the inner surface modified layer M1 and the peripheral modified layer M2 as base points, as shown in Fig. 18(d). At this time, the second separated wafer W2 is separated together with the peripheral portion We. The method of separating the first wafer W is the same as that of the above embodiment (step P2 in Fig. 6).

[0109] Next, the first separated wafer W1 is transported to the modified layer removing device 90 by the wafer transport device 32. In the modified layer removing device 90, first, an image of the separated surface W1a of the first separated wafer W1 is captured, and the remaining position of the inner surface modified layer M1 is obtained. At this time, the horizontal orientation of the first separated wafer W1 may be adjusted.

[0110] In parallel with this, the second separated wafer W2 is transferred to the reversing device 80 by the wafer transfer device 32. In the reversing device 80, the front and back surfaces of the second separated wafer W2 are reversed.

[0111] The second separated wafer W2 with the front and back sides inverted is transferred to the modified layer removing device 90 by the wafer transfer device 32. In the modified layer removing device 90, first, an image of the separated surface W2a of the second separated wafer W2 is captured, and the remaining position of the inner surface modified layer M1 is obtained. At this time, the horizontal orientation of the second separated wafer W2 may be adjusted.

[0112] Next, in the modified layer removal device 90, the inner surface modified layer M1 and the peripheral modified layer M2 remaining on the separation surfaces W1a and W2a of the separated wafers W1 and W2 are removed, respectively, as shown in Figures 18(e) and 18(f). Specifically, the inner surface modified layer M1 and the peripheral modified layer M2 remaining on the separation surfaces W1a and W2a are irradiated with laser light to remove the inner surface modified layer M1 by ablation processing. The method of removing the inner surface modified layer M1 is the same as in the above embodiment (step P6 in Figure 6).

[0113] Next, the first separated wafer W1 and the second separated wafer W2 are each transported to the processing apparatus 100 by the wafer transport device 32. In the processing apparatus 100, the separation surface W1a of the first separated wafer W1 is ground as shown in FIG. 18(g), the separation surface W1a is flattened, and the displacement amount H of the separation surface W1a is reduced to the target surface. If the peripheral modified layer M2 has not been completely removed, the peripheral modified layer M2 is completely removed by grinding. At the same time, the separation surface W2a of the second separated wafer W2 is ground as shown in FIG. 18(h), the separation surface W2a is flattened, and the peripheral modified layer M2 is completely removed. The method of grinding the separation surfaces W1a and W2a is the same as that of the above embodiment (step P7 in FIG. 6).

[0114] The subsequent processes are the same as those in the above embodiment (steps P8 and P9 in FIG. 6). That is, the separated wafers W1 and W2 that have been subjected to the grinding process are sequentially cleaned in the cleaning device 50 and etched in the wet etching device 40.

[0115] In this embodiment, the same effects as those of the above embodiment can be obtained. Moreover, according to this embodiment, the peripheral portion We of the first wafer W is removed by edge trimming, so that the formation of a so-called knife edge shape in the peripheral portion We is suppressed.

[0116] In the above embodiment, the modified layer removal process is performed in the modified layer removal device 90 disposed independently inside the wafer processing system 1, but the modified layer removal process may be performed, for example, in the modified separation device 70. In this case, since the laser light (e.g., YAG laser) for forming the inner surface modified layer M1 and the laser light (e.g., picosecond laser) for performing the modified layer removal process are different, it is preferable that the laser heads for irradiating the respective laser lights are disposed independently.

[0117] In the above embodiment, the inner surface modified layer M1, which is the base point for separating the first wafer W, and the peripheral modified layer M2, which is the base point for removing the peripheral portion We, are formed in the modified separation device 70, but the positions at which these modified layers are formed are not limited to this. Specifically, for example, a separation device (not shown) for separating the first wafer W and a modification device (not shown) for forming the inner surface modified layer M1 and the peripheral modified layer M2 may be independently arranged inside the wafer processing system 1, and these modified layers may be formed inside the modification device.

[0118] In the above embodiment, the processing object is a silicon wafer, but the type of processing object is not limited to this. For example, instead of a silicon substrate, a glass substrate, a single crystal substrate, a polycrystalline substrate, or an amorphous substrate may be selected as the processing object. Also, instead of a circular substrate, an ingot, a base, or a thin plate may be selected.

[0119] In the above embodiment, the case where the first wafer W in the overlapped wafer T is thinned has been described, but the above embodiment can also be applied to the case where one wafer is thinned.

[0120] The embodiments disclosed herein should be considered as illustrative and not restrictive in all respects. The above-described embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0121] 1. Wafer Processing System 70 Modified layer removal device 140 Control device L Laser light M1 Internal surface modification layer S 2nd wafer T Polymerized Wafer W First wafer W1 First separation wafer W1a separation plane W2 Second separation wafer W2a Separation surface

Claims

1. A processing system for processing an object to be processed, comprising: a modified layer position acquisition device that acquires the position of the modified layer remaining on the separation surface of the separated object separated from the modified layer formed inside the processing object as a base point; a modified layer removing device that irradiates the separation surface with a laser beam to remove the modified layer remaining on the separation surface; A control device, The control device includes: performing control for acquiring the position of the modified layer remaining on the separation surface in the modified layer position acquisition device; and performing control in the modified layer removal device to perform a first removal process in which the modified layer remaining on the separation surface is irradiated with a first laser light to remove the modified layer.

2. The control device includes: The processing system according to claim 1 , wherein the modified layer removal device controls the first laser light to be irradiated onto the separation surface with an output that does not cause a new modified layer to be formed on the separation surface by irradiation of the first laser light.

3. 3. The processing system according to claim 1, further comprising a separation device that separates the object to be processed into a plurality of separated bodies using the modified layer as a base point.

4. The control device includes: and performing control to perform a second removal process in which a second laser beam is irradiated onto a convex portion, which is a non-remaining position of the modified layer on the separation surface, in the modified layer removal device; 4. The processing system according to claim 1, wherein an amount of displacement of the separation surface after irradiation with the first laser light is made equal to an amount of displacement of the separation surface after irradiation with the second laser light.

5. the modified layer removal device is configured to be capable of simultaneously irradiating a plurality of the laser beams to different positions on the separation surface; The control device includes: In the first removal process, a control is performed in which a plurality of the first laser beams are simultaneously irradiated onto different modified layers remaining on the separation surface; The processing system according to claim 4 , wherein in the second removal process, control is executed such that different convex portions are simultaneously irradiated with a plurality of the second laser beams.

6. the modified layer removal device is configured to be capable of simultaneously irradiating a plurality of the laser beams to different positions on the separation surface; The control device includes: The processing system of claim 4, further comprising control for simultaneously executing the first removal process and the second removal process by simultaneously irradiating the modified layer with the first laser light and the convex portion with the second laser light.

7. The processing system according to claim 6 , wherein the control device performs control to independently adjust outputs of the first laser light and the second laser light that are simultaneously irradiated.

8. The control device includes: The processing system of claim 4, wherein in the modified layer removal device, the first laser light is irradiated onto the modified layer, and the second laser light is irradiated onto the convex portion in accordance with the first laser light without changing the output of the laser light irradiated in the modified layer removal device.

9. the processing object is a laminated substrate in which a front surface side of a first substrate and a front surface side of a second substrate are bonded together, The processing object is separated into a first separation substrate on a front side and a second separation substrate on a back side of the first substrate, using the modified layer formed inside the first substrate as a base point; 9. The processing system according to claim 1, wherein the modified layer removal device removes at least the modified layer remaining on the separation surface of the first separation substrate.

10. 10. The processing system according to claim 1, further comprising a processing device for grinding the separation surface after the modified layer has been removed.

11. A method for processing an object to be processed, comprising the steps of: acquiring a position of the modified layer remaining on a separation surface of a separated object separated from the modified layer formed inside the processing object as a base point; and performing a first removal process by irradiating the modified layer remaining on the separation surface with a first laser beam to remove the modified layer.

12. The processing method according to claim 11 , wherein the separation surface is irradiated with the first laser light at an output that does not cause a new modified layer to be formed on the separation surface by irradiation with the first laser light.

13. The processing method according to claim 11 or 12, further comprising separating the object to be processed into a plurality of separate bodies using the modified layer as a base point.

14. performing a second removal process of irradiating a convex portion, which is a non-remaining portion of the modified layer on the separation surface, with a second laser beam; The processing method according to any one of claims 11 to 13, wherein an amount of displacement of the separation surface after irradiation with the first laser light and an amount of displacement of the separation surface after irradiation with the second laser light are made to coincide with each other.

15. In the first removal process, a plurality of the first laser beams are simultaneously irradiated onto different modified layers remaining on the separation surface; The processing method according to claim 14 , further comprising: simultaneously irradiating different convex portions with a plurality of the second laser beams in the second removal process.

16. The processing method according to claim 14 , wherein the first removal process and the second removal process are performed simultaneously by simultaneously irradiating the modified layer with the first laser light and irradiating the convex portion with the second laser light.

17. The processing method according to claim 16 , wherein outputs of the first laser light and the second laser light which are simultaneously irradiated are adjusted independently of each other.

18. The processing method according to claim 14, further comprising irradiating the modified layer with the first laser light, and then irradiating the convex portion with the second laser light in accordance with the first laser light without changing the output of the irradiated laser light.

19. the processing object is a laminated substrate in which a front surface side of a first substrate and a front surface side of a second substrate are bonded together, The processing object is separated into a first separation substrate on a front side and a second separation substrate on a back side of the first substrate, using the modified layer formed inside the first substrate as a base point; The processing method according to any one of claims 11 to 18, further comprising removing the modified layer remaining at least on the separation surface of the first separation substrate.

20. The method according to any one of claims 11 to 19, further comprising grinding the separation surface after removal of the modified layer.

Images