Substrate processing device

Abstract

The objective of this invention is to properly peel the second substrate from the first substrate in an overlapping substrate formed by bonding the first substrate and the second substrate. As a technical means to solve the above-mentioned problems, the present invention provides a substrate processing apparatus for processing an overlapping substrate formed by bonding a first substrate and a second substrate of a silicon-based substrate, comprising: a program storage unit for storing a program; a computer for reading the program from the program storage unit and running the program; a laser irradiation unit; and a peeling unit; wherein the program is a program that runs on the computer to cause the substrate processing apparatus to execute a substrate processing method; on the second substrate, a peeling promotion layer and a laser absorption layer are sequentially stacked from the second substrate side; the substrate processing method includes the following steps: in the laser irradiation unit, stress is generated at the interface between the laser absorption layer and the peeling promotion layer by irradiating the laser absorption layer with far-infrared wavelength from the second substrate side, thereby reducing the bonding strength between the laser absorption layer and the peeling promotion layer; and in the peeling unit, the second substrate is peeled from the first substrate along the boundary between the laser absorption layer and the peeling promotion layer.

Description

Technical Field

[0001] This invention relates to a substrate processing apparatus. Prior Technology

[0002] Patent Document 1 discloses a method for manufacturing a semiconductor device. The method for manufacturing a semiconductor device includes: a heating step in which a CO2 laser is irradiated on the back side of a semiconductor substrate to locally heat a stripping oxide film; and a transfer step in which stripping occurs in the stripping oxide film and / or at the interface between the stripping oxide film and the semiconductor substrate, thereby transferring a semiconductor element to a transfer target substrate. [Known Technical Documents] [Patent Literature]

[0003] Patent Document 1: Japanese Patent Application Publication No. 2007-220749 Summary of the Invention

[0004] [Problem to be solved by the present invention] The technology disclosed in the present invention properly peels the second substrate from the first substrate in an overlapping substrate formed by bonding the first substrate and the second substrate. [Technical means to solve the problem]

[0005] One aspect of the present invention is a substrate processing apparatus for processing an overlapping substrate formed by bonding a first substrate and a second substrate of a silicon substrate, comprising: a program storage unit for storing a program; a computer for reading the program from the program storage unit and running the program; a laser irradiation unit; and a peeling unit; wherein the program is a program that runs on the computer to cause the substrate processing apparatus to execute a substrate processing method; on the second substrate, a peeling promotion layer and a laser absorption layer are sequentially stacked from the second substrate side; the substrate processing method includes the following steps: in the laser irradiation unit, stress is generated at the interface between the laser absorption layer and the peeling promotion layer by irradiating the laser absorption layer with far-infrared wavelength from the second substrate side, thereby reducing the bonding strength between the laser absorption layer and the peeling promotion layer; and in the peeling unit, the second substrate is peeled from the first substrate along the boundary between the laser absorption layer and the peeling promotion layer. [Effects of the Invention]

[0006] According to the present invention, the second substrate can be appropriately peeled off from the first substrate in an overlapping substrate formed by bonding the first substrate and the second substrate. Simple Explanation of the Diagram

[0007] Figure 1 is a side view showing an example of an overlapping wafer processed by a wafer processing system. Figure 2 is a top view illustrating the general structure of a wafer processing system. Figure 3 is a side view of the general structure of the laser irradiation device for displaying the interface. Figure 4 is a top view showing the general structure of a laser irradiation device for displaying interfaces. Figure 5 is an explanatory diagram showing the appearance of the stripped modified layer forming this embodiment. Figure 6 is a top view showing an example of the formation of the stripped modified layer in this embodiment. Figures 7(a) and (b) are explanatory diagrams showing the flow of gas inside the overlapping wafer during wafer processing in this embodiment. Figure 8 is a top view showing another example of the stripped modified layer of this embodiment. Figures 9(a) and (b) are explanatory diagrams showing the peeling of the second wafer in this embodiment. Figure 10 is an explanatory diagram showing the peeling of the second wafer in this embodiment. Figures 11(a) and (b) are explanatory diagrams showing the pushing motion of the second wafer. Figures 12(a) and (b) are explanatory diagrams showing the pushing motion of the second wafer. Figure 13 is a side view showing a structural outline of an overlay wafer in another embodiment. Figures 14(a) to (d) are explanatory diagrams showing the edge trimming process of this embodiment. Implementation

[0008] In recent years, laser lift-off has been implemented in LED manufacturing processes: using laser light to peel off the GaN (gallium nitride) compound crystalline layer (material layer) from a sapphire substrate. In this laser lift-off process, since the sapphire substrate is transmissive to short-wavelength laser light (such as UV light), short-wavelength laser light with high absorption rates in the laser absorption layer can be used, and a wide range of laser light options are available.

[0009] On the other hand, in the semiconductor device manufacturing process, a step is performed to transfer the device layer formed on the surface of one substrate (such as a silicon substrate) to another substrate. Silicon substrates are generally transmissive to NIR (near-infrared) laser light, but the laser absorption layer is also transmissive to NIR laser light, thus raising concerns about damage to the device layer. Therefore, in the semiconductor device manufacturing process, FIR (far-infrared) laser light is used for laser stripping.

[0010] Generally, for example, a CO2 laser can be used, employing FIR wavelength laser light. In the method described in Patent Document 1 above, a CO2 laser is used to irradiate the release oxide film, which serves as a laser absorption layer, thereby causing release at the interface between the release oxide film and the substrate.

[0011] However, after repeated and careful review by the inventors of this case, it was discovered that in the laser lift-off method, the peeling of the substrate and the laser absorption layer did not occur properly, that is, the transfer could not be performed properly. Specifically, in areas where laser light was not irradiated in-plane with the laser absorption layer, there were areas where the bonding strength between the laser absorption layer and the substrate was not reduced, raising the following concerns: In areas where the laser light was not irradiated, the wafer W was peeled off from the inside, and a portion of the wafer W (silicon wafer) and the component layer were transferred together to the surface of the laser absorption layer after the transfer process.

[0012] The technology disclosed in this invention involves appropriately peeling the second substrate from the first substrate in an overlapping substrate formed by bonding the first substrate and the second substrate. Hereinafter, a wafer processing system as a substrate processing apparatus and a wafer processing method as a substrate processing method according to this embodiment will be described with reference to the drawings. Furthermore, in this specification and the drawings, elements having substantially the same functional configuration are given the same reference numerals to avoid redundant descriptions.

[0013] As shown in Figure 1, the overlapping wafer T processed as an overlapping substrate in this embodiment is formed by bonding a first wafer W1, which serves as a first substrate, and a second wafer W2, which serves as a second substrate. Hereinafter, in the first wafer W1, the side bonded to the second wafer W2 is referred to as the front side W1a, and the side opposite to the front side W1a is referred to as the back side W1b. Similarly, in the second wafer W2, the side bonded to the first wafer W1 is referred to as the front side W2a, and the side opposite to the front side W2a is referred to as the back side W2b.

[0014] The first wafer W1 is, for example, a semiconductor wafer such as a silicon substrate. A device layer D1 containing a plurality of devices is formed on the front side W1a of the first wafer W1. A surface film F1 is further formed on the device layer D1, and the wafer W2 is bonded to the second wafer through the surface film F1. Examples of the surface film F1 include oxide films (SiO2 films, TEOS films), SiC films, SiCN films, or adhesives. Alternatively, the device layer D1 and the surface film F1 may not be formed on the front side W1a.

[0015] The second wafer W2 is, for example, a semiconductor wafer such as a silicon substrate. On the front side W2a of the second wafer W2, a release facilitator layer P2, a laser absorption layer P, a device layer D2, and a surface film F2 are stacked sequentially from the front side W2a, and bonded to the first wafer W1 through the surface film F2. The device layer D2 and the surface film F2 are the same as the device layer D1 and the surface film F1 of the first wafer W1, respectively. As a laser absorption layer P, examples include those that can absorb laser light (e.g., CO2 laser) as described later, such as oxide films (SiO2 films, TEOS films). The release facilitator layer P2 is formed to facilitate the release (transfer) of the second wafer W2 from the first wafer W1, and is formed of a material with lower adhesion to the second wafer W2 (silicon) than to the laser absorption layer P, such as silicon nitride (SiN). Alternatively, on the front side W2a, there may be cases where the release facilitator layer P2, laser absorption layer P, element layer D2, and surface film F2 are not formed. In this case, the release facilitator layer P2 and laser absorption layer P are formed on the front side W1a of the first wafer W1 where the element layer D1 and surface film F1 are formed, and the element layer D1 is transferred to the side of the second wafer W2.

[0016] The edge portion We of the second wafer W2 is chamfered, and the thickness of the edge portion We decreases as its cross-section faces its leading edge. In semiconductor device manufacturing processes, there are instances where the back side of the second wafer W2, thus formed, is removed for thinning. During this thinning process, there is a concern that the edge portion We may become a sharp shape (a so-called cutting edge). This could lead to peeling off the edge portion We of the second wafer W2, potentially damaging the second wafer W2. Therefore, there are cases where the edge portion We of the second wafer W2 is removed before this thinning process, followed by the edge trimming described below. The edge portion We is the portion removed during this edge trimming, for example, a radial distance of 0.5 mm to 3 mm from the outer end of the second wafer W2.

[0017] The wafer processing system 1 described later in this embodiment performs: the aforementioned laser stripping process as wafer processing, namely the transfer process of the element layer D2 to the side of the first wafer W1; or the aforementioned edge trimming process as wafer processing, namely the removal process of the edge portion We of the second wafer W2.

[0018] As shown in Figure 2, the wafer processing system 1 has a configuration that integrates the infeed block G1, the transport block G2, and the processing block G3. The infeed block G1, the transport block G2, and the processing block G3 are arranged side by side in this order, starting from the negative X-axis direction.

[0019] The wafer cassettes Ct, Cw1, and Cw2, which can respectively hold multiple overlapping wafers T, multiple first wafers W1, and multiple second wafers W2, are moved in and out of the loading / unloading block G1. A wafer cassette mounting stage 10 is provided in the loading / unloading block G1. In the illustrated example, multiple, for example, three wafer cassettes Ct, Cw1, and Cw2 are arbitrarily mounted in a row along the Y-axis direction on the wafer cassette mounting stage 10. Furthermore, the number of wafer cassettes Ct, Cw1, and Cw2 mounted on the wafer cassette mounting stage 10 is not limited in this embodiment and can be arbitrarily determined.

[0020] In the transport block G2, a wafer transport device 20 is installed adjacent to the wafer cassette stage 10 on the positive X-axis side. The wafer transport device 20 is configured to move freely along the transport path 21 extending along the Y-axis. Furthermore, the wafer transport device 20 includes, for example, two transport arms 22, which hold and transport overlapping wafers T, the first wafer W1, and the second wafer W2. Each transport arm 22 is configured to move freely in the horizontal direction, the vertical direction, around the horizontal axis, and around the vertical axis. The configuration of the transport arms 22 is not limited to this embodiment and can be any configuration. The wafer transport device 20 is configured to transport overlapping wafer T, first wafer W1, and second wafer W2 to the wafer cassettes Ct, Cw1, and Cw2 of the wafer cassette mounting stage 10 and the transport device 30 described later.

[0021] In the transport block G2, on the positive X-axis side of the wafer transport device 20, a transport device 30 is provided adjacent to the wafer transport device 20. It is used to transport the overlapping wafer T, the first wafer W1, and the second wafer W2.

[0022] The processing block G3 includes a wafer transfer device 40, an edge removal device 50, a cleaning device 60, an internal laser irradiation device 70, and an interface laser irradiation device 80.

[0023] The wafer transport device 40 is configured to move arbitrarily along the transport path 41 extending along the X-axis. Furthermore, the wafer transport device 40 includes, for example, two transport arms 42, which hold and transport the overlapping wafer T, the first wafer W1, and the second wafer W2. Each transport arm 42 is configured to move arbitrarily in the horizontal direction, the vertical direction, around the horizontal axis, and around the vertical axis. The configuration of the transport arms 42 is not limited to this embodiment and can be any configuration. The wafer transport device 40 is configured to transport the overlapping wafer T, the first wafer W1, and the second wafer W2 to the transport device 30, the edge removal device 50, the cleaning device 60, the internal laser irradiation device 70, and the interface laser irradiation device 80.

[0024] An edge removal device 50 is provided on the positive Y-axis side of the wafer transport device 40 to remove the edge portion We of the second wafer W2, i.e., to perform edge trimming. A cleaning device 60 is provided on the negative Y-axis side of the wafer transport device 40 to clean the overlapping wafer T after peeling or after the removal of the edge portion We. An internal laser irradiation device 70, which serves as the second laser irradiation unit, is provided on the positive Y-axis side of the wafer transport device 40 to irradiate the interior of the second wafer W2 with laser light (internal laser light, such as YAG laser), forming the edge modification layer M2, which will be described later, as the base point for the peeling of the edge portion We. An interface laser irradiation device 80 is provided on the negative Y-axis side of the wafer transport device 40 to irradiate the laser absorption layer P formed on the front surface W2a of the second wafer W2 with laser light (interface laser light, such as CO2 laser). The configuration of the interface laser irradiation device 80 will be described later.

[0025] In the aforementioned wafer processing system 1, a control device 90 is provided as a control unit. The control device 90, for example, is a computer, and includes a program storage unit (not shown). The program storage unit stores a program for controlling the processing of the overlapping wafer T in the wafer processing system 1. Furthermore, the program storage unit also stores a program for controlling the operation of the drive systems such as the various processing devices or conveying devices, to realize the wafer processing described later in the wafer processing system 1. Alternatively, the aforementioned program can be recorded on a computer-readable recording medium H, and installed from the recording medium H onto the control device 90.

[0026] The wafer processing system 1, configured as described above, can perform the laser stripping process of the overlapping wafer T, namely the transfer process of the device layer D2 to the first wafer W1, and the edge trimming process of the second wafer W2. Alternatively, if the edge trimming process of the second wafer W2 is not performed in the wafer processing system 1, the edge removal device 50 and the internal laser irradiation device 70 can be omitted.

[0027] Furthermore, in this embodiment, the second wafer W2 is stripped from the first wafer W1 in the interface laser irradiation apparatus 80 as described later, but a stripping device as a stripping section may also be further provided in the wafer processing system 1.

[0028] Next, the laser irradiation device 80 will be used to describe the interface described above.

[0029] As shown in Figures 3 and 4, the interface laser irradiation device 80 includes a suction cup 100 that holds the overlapping wafer T on its top surface. The suction cup 100 adsorbs and holds a portion or the entire surface of the back side W1b of the first wafer W1. A lifting pin (not shown) is provided on the suction cup 100 for transferring the overlapping wafer T between it and the transfer arm 42. The lifting pin is configured to move freely up and down through a through hole (not shown) formed in the suction cup 100, supporting the overlapping wafer T from below and causing it to move up and down.

[0030] A suction cup 100 is supported on a slide table 102 via an air bearing 101. A rotating mechanism 103 is provided on the bottom surface of the slide table 102. The rotating mechanism 103 serves as a drive source, for example, by incorporating a motor. The suction cup 100 is configured to rotate arbitrarily around the θ-axis (vertical axis) via the rotating mechanism 103 and the air bearing 101. The slide table 102 is configured to move along a track 105 extending in the Y-axis direction from a base 106 via a moving mechanism 104 provided on its bottom surface. Furthermore, the drive source of the moving mechanism 104 is not particularly limited; for example, a linear motor can be used.

[0031] A laser head 110, serving as a laser irradiation unit, is disposed above the chuck 100. The laser head 110 includes a lens 111. The lens 111 is a cylindrical member disposed on the bottom surface of the laser head 110, irradiating laser light onto the overlapping wafer T held on the chuck 100. In this embodiment, the laser light is pulsed CO2 laser light, emitted from the laser head 110, which passes through the second wafer W2 and irradiates the laser absorption layer P. The wavelength of the CO2 laser light is, for example, 8.9 μm to 11 μm. Furthermore, the laser head 110 is configured to be arbitrarily raised and lowered by a lifting mechanism (not shown). The laser light source is disposed at a location outside the laser head 110, away from it.

[0032] Furthermore, a transfer pad 120 serving as a stripping section is provided above the suction cup 100. The transfer pad 120 has an adsorption surface on its bottom surface for adsorbing and holding the back side W2b of the second wafer W2. The transfer pad 120 is configured to be arbitrarily raised and lowered by a lifting mechanism (not shown). The transfer pad 120 transports the second wafer W2 between the suction cup 100 and the transfer arm 42. Specifically, after the suction cup 100 is moved to a position below the transfer pad 120 (the transfer position with the transfer arm 42), the transfer pad 120 is lowered to adsorb and hold the back side W2b of the second wafer W2. Then, the transfer pad 120 is raised again to peel the second wafer W2 from the first wafer W1. The peeled second wafer W2 is transferred from the transfer pad 120 to the transfer arm 42 and removed from the interface laser irradiation device 80. Alternatively, the transfer pad 120 can also be configured to reverse the front and back sides of the wafer via a reversing mechanism (not shown).

[0033] Next, the wafer processing performed using the wafer processing system 1 configured as described above will be explained. Furthermore, the following explanation will describe the case where laser stripping is performed in the wafer processing system 1, that is, the transfer of the device layer D2 of the second wafer W2 to the first wafer W1. In this embodiment, the first wafer W1 and the second wafer W2 are bonded together in a bonding device (not shown) outside the wafer processing system 1 to pre-form an overlapping wafer T.

[0034] First, a wafer cassette Ct containing multiple overlapping wafers T is placed on the wafer cassette mounting stage 10 in the transport block G1. Next, the overlapping wafers T are removed from the wafer cassette Ct by the wafer transport device 20. The overlapping wafers T removed from the wafer cassette Ct are then transferred to the wafer transport device 40 via the transfer device 30, and then transported to the interface laser irradiation device 80. At the interface laser irradiation device 80, the second wafer W2 is peeled off from the first wafer W1 (laser peeling process).

[0035] Specifically, the overlapping wafer T, held by the lifting pin and held by the suction cup 100, is first moved to the processing position by the moving mechanism 104 from the conveying arm 42. This processing position is the position where laser light can be irradiated onto the overlapping wafer T (laser absorption layer P) from the laser head 110.

[0036] Next, as shown in Figures 5 and 6, laser light L (CO2 laser light) is pulsedly irradiated onto the back surface W2b of the second wafer W2 from the laser head 110. At this time, the laser light L passes through the second wafer W2 and the lift-off promoting layer P2 from the back surface W2b side of the second wafer W2 and is absorbed in the laser absorption layer P. As shown in Figure 7(a), stress is generated inside the laser absorption layer P that has absorbed the laser light L. Hereinafter, the stress accumulation layer formed by laser light irradiation, which becomes the base point for the lift-off of the second wafer W2 (the base point for the transfer of the element layer D2), is called the "lift-off modifier layer M1". Furthermore, the laser light L irradiating the laser absorption layer P absorbs almost all of its energy due to the formation of the lift-off modifier layer M1 and does not reach the element layer D2. Therefore, damage to the element layer D2 can be suppressed.

[0037] Here, the laser light L irradiating the laser absorption layer P is controlled to output such that the peeling promotion layer P2 and the laser absorption layer P do not peel off due to the stress generated by the irradiation of the laser light L.

[0038] Thus, by irradiation with laser light L, stress is accumulated inside the laser absorption layer P without causing peeling between the peeling-promoting layer P2 and the laser absorption layer P, thereby forming the peeling-modified layer M1. More specifically, for example, by irradiation with laser light, the laser absorption layer P is gasified, and by eliminating the space for gas to escape as described above, compressive stress is accumulated to form the peeling-modified layer M1. Furthermore, for example, by absorption of laser light, heat is generated in the laser absorption layer P, and by the difference in the coefficients of thermal expansion between the peeling-promoting layer P2 and the laser absorption layer P, shear stress is accumulated to form the peeling-modified layer M1.

[0039] The stress generated by the irradiation of laser light L typically remains at the irradiation location of laser light L (inside the laser absorption layer P), as described above, forming a release modifier layer M1. However, in this embodiment, a release promoting layer P2 is formed between the front side W2a of the second wafer W2 and the laser absorption layer P, and the adhesion between the release promoting layer P2 and the second wafer W2 is less than that between the release promoting layer P2 and the laser absorption layer P. Therefore, as shown in FIG7(b), the stress generated inside the laser absorption layer P is accumulated at the interface between the release promoting layer P2 and the second wafer W2 through the release promoting layer P2. In other words, the stress generated by the irradiation of laser light L moves to the interface between the release promoting layer P2 and the second wafer W2, where it can be more stably retained. Subsequently, if the stress is accumulated at the interface between the release promoting layer P2 and the second wafer W2 in this way, the bonding strength between the release promoting layer P2 and the second wafer W2 is reduced.

[0040] In this embodiment, the irradiation of the laser absorption layer P with laser light L, i.e., the separation of the peeling promotion layer P2 from the second wafer W2, is performed on the entire surface of the laser absorption layer P in top view. Specifically, when irradiating the laser absorption layer P with laser light L, the chuck 100 (overlapping wafer T) is rotated by the rotation mechanism 103, and the chuck 100 is moved along the Y-axis by the moving mechanism 104. In this way, the laser absorption layer P is irradiated with laser light L, for example, from the radially outer side to the inner side, resulting in spiral irradiation on the entire surface of the laser absorption layer P from the outer side to the inner side. Furthermore, the blackened arrows in Figure 6 indicate the rotation direction of the chuck 100. Additionally, the formation direction of the peeling modification layer M1 can also be from the radially inner side to the outer side.

[0041] Here, the formation interval of adjacent stripping and remodeling layers M1, in other words, the pulse interval (frequency) of the laser light L, is controlled to a distance that prevents stripping from occurring in adjacent stripping and remodeling layers M1 due to the impact generated during the formation of the stripping and remodeling layer M1. Specifically, for example, it is preferable to form adjacent stripping and remodeling layers M1 such that they do not overlap when viewed from above. Furthermore, it is preferable to form adjacent stripping and remodeling layers M1 close to each other.

[0042] Alternatively, as shown in Figure 8, laser light L can be irradiated in a concentric ring shape within the laser absorption layer P. However, in this case, the rotation of the suction cup 100 and the movement of the suction cup 100 in the Y direction are performed alternately. Therefore, the method of irradiating laser light L in a spiral shape as described above can shorten the irradiation time and improve the processing capacity.

[0043] Furthermore, in this embodiment, when the laser absorption layer P is irradiated with laser light L, the chuck 100 is rotated, but the laser head 110 can also be moved, causing the laser head 110 to rotate relative to the chuck 100. Additionally, although the chuck 100 is moved along the Y-axis, the laser head 110 can also be moved along the Y-axis.

[0044] If laser light L is applied to the entire surface of the laser absorption layer P, then the chuck 100 is moved to a transfer position below the transfer pad 120 by the moving mechanism 104. In the transfer position, as shown in FIG9(a), the back surface W2b of the second wafer W2 is held by the transfer pad 120. Then, as shown in FIG9(b), the transfer pad 120 is raised to peel the second wafer W2 from the release facilitator layer P2 (the first wafer W1). This transfers the element layer D2 formed on the front surface of the second wafer W2 to the first wafer W1. At this time, as described above, stress generated by laser light L accumulates at the interface between the release facilitator layer P2 and the second wafer W2, reducing the bonding strength. Therefore, the second wafer W2 can be peeled from the release facilitator layer P2 without applying a large load.

[0045] Furthermore, as described above, the stripping modifier layers M1 are formed so that they do not overlap. The stress accumulated due to the formation of the stripping modifier layers M1 is released externally when the second wafer W2 peels off from the stripping facilitator layer P2 at the location where the stripping modifier layers M1 are formed. In this embodiment, as described above, the stripping modifier layers M1 are formed close to each other. Therefore, when peeling occurs at the location where adjacent stripping modifier layers M1 are formed, that is, when stress is released externally at the adjacent location, it is released in a chain reaction. That is, if a portion of the interface between the stripping facilitator layer P2 and the second wafer W2 is peeled off by raising the transport pad 120, then the entire surface of the second wafer W2 is peeled off in a chain reaction starting from that peeling point. In other words, the second wafer W2 can be peeled off from the stripping facilitator layer P2 more appropriately without applying a huge load.

[0046] However, for example, due to factors such as the frequency of the laser light L or the rotation speed of the chuck 100, the laser absorption layer P may not be irradiated by the laser light L, resulting in areas where the peeling promotion layer P2 and the second wafer W2 do not peel off (unpeeled areas). However, in this embodiment, since the peeling promotion layer P2 is formed of a material with low adhesion to the second wafer W2 (silicon), even if an unpeeled area is formed, the peeling of the peeling promotion layer P2 and the second wafer W2 can still be easily performed. Because the peeling promotion layer P2 and the second wafer W2 are properly peeled off in this way, the transfer of a portion of the second wafer W2 (silicon wafer) to the surface of the peeling promotion layer P2 after the second wafer W2 has been peeled off can be appropriately suppressed. Furthermore, damage to the second wafer W2 after peeling can be suppressed.

[0047] Furthermore, for proper separation of the release facilitator layer P2 from the interface of the second wafer W2, the stress generated by laser light L irradiation must pass through the release facilitator layer P2. Specifically, for example, when the laser absorption layer P is vaporized, the generated gas must pass through the release facilitator layer P2. Additionally, for example, when separation of the release facilitator layer P2 from the second wafer W2 is performed based on the difference in thermal expansion coefficients, the heat generated by laser light irradiation must be properly transferred to the interface between the release facilitator layer P2 and the second wafer W2. However, if the release facilitator layer P2 is thick, the generated stress may not pass through it properly and may remain at the interface between the release facilitator layer P2 and the laser absorption layer P. Therefore, in order to properly perform separation at the interface between the release facilitator layer P2 and the second wafer W2, the thickness of the release facilitator layer P2 should be reduced relative to the laser absorption layer P, specifically, for example, to one-tenth the thickness of the laser absorption layer P. By reducing the thickness of the release facilitator layer P2 in this way, the generated stress can be properly transmitted through the release facilitator layer P2, reducing the bonding strength between the second wafer W2 and the release facilitator layer P2. That is, the second wafer W2 can be properly peeled off from the release facilitator layer P2.

[0048] However, even if the thickness of the release accelerator layer P2 increases, and the resulting stress does not properly pass through the release accelerator layer P2 and remains at the interface between the release accelerator layer P2 and the laser absorption layer P, the release accelerator layer P2 can still function as a protective film for the second wafer W2. That is, it can appropriately suppress the situation where the silicon wafer and the device layer D2 are transferred together to the interface after the second wafer W2 is peeled off from the inside.

[0049] Specifically, a release modifier layer M1 is formed by the stress generated at the interface between the release promoting layer P2 and the laser absorption layer P. With stress remaining at this interface, the second wafer W2, as shown in Figure 10, is peeled off from the first wafer W1, using the release promoting layer P2 and the laser absorption layer P as the boundary. At this time, the second wafer W2 is peeled off from the laser absorption layer P via the release promoting layer P2, thus leaving no second wafer W2 at the peeling interface. That is, this protects the front surface W2a of the second wafer W2 and suppresses damage to the peeling surface.

[0050] The second wafer W2, stripped from the first wafer W1, is transferred from the transfer pad 120 to the transfer arm 42 of the wafer transfer device 40 and then transported to the wafer cassette Cw2 on the wafer cassette stage 10. Alternatively, the second wafer W2, removed from the interface laser irradiation device 80, can be cleaned in the cleaning device 60 on its front side W2a before being transported to the wafer cassette Cw2.

[0051] On the other hand, the first wafer W1, held in the suction cup 100, is transferred to the transport arm 42 of the wafer transport device 40 via the lifting pin and then transported to the cleaning device 60. In the cleaning device 60, the surface of the release surface, i.e., the release promoting layer P2, is brushed and cleaned. Alternatively, in the cleaning device 60, the back surface W1b of the first wafer W1 and the surface of the release promoting layer P2 can also be cleaned together.

[0052] Subsequently, the first wafer W1, which has undergone all the transfer processing of the component layer D2 to the first wafer W1, is transported via the transfer device 30 and the wafer transport device 20 to the wafer cassette Cw1 of the wafer cassette platform 1. In this way, a series of wafer processing steps in the wafer processing system 1 is completed.

[0053] According to the above embodiment, by forming a release promoting layer P2 between the second wafer W2 and the laser absorption layer P, the second wafer W2 can be appropriately peeled from the first wafer W1, that is, the transfer process of the element layer D2 can be appropriately performed. Specifically, the stress generated in the laser absorption layer P by laser irradiation is moved to the boundary between the second wafer W2 and the release promoting layer P2, thereby reducing the bonding strength at the boundary between the second wafer W2 and the release promoting layer P2, so the second wafer W2 can be appropriately peeled from the release promoting layer P2. Furthermore, at this time, the release promoting layer P2 is formed of a material with low adhesion to the second wafer W2 (e.g., SiN), so the second wafer W2 can be more appropriately peeled from the release promoting layer P2.

[0054] Furthermore, in the above embodiment, although a material with low adhesion to the second wafer W2 (silicon) is used as the release facilitator layer P2, the material used for the release facilitator layer P2 is not limited to such materials. For example, a material with a different coefficient of thermal expansion than the second wafer W2 (silicon) can also be used. In this case, because the amount of deformation caused by the heat generated by the irradiation of the laser light L of the laser absorption layer P differs between the second wafer W2 and the release facilitator layer P2, shear force is generated at the interface between the second wafer W2 and the release facilitator layer P2, which can peel the second wafer W2 from the release facilitator layer P2. In particular, as described above, shear stress is generated and accumulated at the interface between the second wafer W2 and the release facilitator layer P2 as the release modifier layer M1. By using a material with a different coefficient of thermal expansion as the release facilitator layer P2, the peeling of the second wafer W2 from the release facilitator layer P2 can be performed more appropriately.

[0055] Furthermore, in the above embodiment, the second wafer W2 is peeled from the peeling promotion layer P2 by irradiation with laser light L. However, during the peeling of the second wafer W2, the overlapping wafer T warps. This warping of the overlapping wafer T raises concerns that wafer processing in the wafer processing system 1 may not be properly performed. Therefore, to suppress this warping of the overlapping wafer T, the overlapping wafer T can be pushed from above during irradiation of the laser absorption layer P with laser light L.

[0056] For example, if the superimposed wafer T warps by deforming into a convex shape, as shown in Figure 11, the center of the superimposed wafer T can be pressed by the pressing member 200. Specifically, when peeling off the second wafer W2, firstly, a peeling modifier layer M1 is pre-formed in the center of the laser absorption layer P, which is within the pressing range of the pressing member 200. The radial direction of the peeling modifier layer M1 is not particularly limited. If the peeling modifier layer M1 is formed in the center of the laser absorption layer P, then the center of the superimposed wafer T with the peeling modifier layer M1 formed is pressed by the pressing member 200. Subsequently, while the center is being pressed by the pressing member 200, the peeling modifier layer M1 is formed on the outer periphery of the laser absorption layer P, and then the second wafer W2 is peeled off. At this time, since the center of the superimposed wafer T is pressed by the pressing member 200, the formation of the peeling modifier layer M1 to the outer periphery of the laser absorption layer P is suppressed, and the warping of the superimposed wafer T during the peeling of the second wafer W2 is suppressed.

[0057] In addition, in order to rotate the superimposed wafer T when irradiated by laser light L, the end of the pressing member 200 should be configured to rotate together with the superimposed wafer T.

[0058] Furthermore, for example, if the overlapping wafer T warps by deforming into a convex shape, as shown in Figure 12, the edge portion We of the overlapping wafer T can be pressed by the pressing member 200. Specifically, when peeling off the second wafer W2, firstly, a peeling modifier layer M1 is pre-formed on the outer periphery of the laser absorption layer P within the pressing range of the pressing member 200. If the peeling modifier layer M1 is formed on the outer periphery of the laser absorption layer P, then the outer periphery of the overlapping wafer T with the peeling modifier layer M1 formed is pressed by the pressing member 200. Subsequently, while the outer periphery is being pressed by the pressing member 200, the peeling modifier layer M1 is formed on the center portion of the laser absorption layer P, and then the second wafer W2 is peeled off. At this time, since the outer periphery of the superimposed wafer T is pressed by the pressing member 200, the formation of the peeling modifier layer M1 towards the center of the laser absorption layer P and the warping of the superimposed wafer T during the peeling of the second wafer W2 are suppressed.

[0059] Alternatively, in the superimposed wafer T subjected to the above-described morphological processing, as shown in Figure 13, a reflective film R can be provided between the laser absorption layer P and the element layer D2. That is, the reflective film R is formed in the laser absorption layer P on the side opposite to the incident surface of the laser light L. A material with high reflectivity and a high melting point for the laser light L, such as a metal film, is used for the reflective film R. Furthermore, the element layer D2 is a functional layer and is a different layer from the reflective film R.

[0060] In this situation, the laser light L emitted from the laser head 110 passes through the second wafer W2 and is almost completely absorbed in the laser absorption layer P. Even if there is any unabsorbed laser light L, it is reflected by the reflective film R. As a result, the laser light L does not reach the element layer D2, effectively suppressing damage to the element layer D2.

[0061] Furthermore, the laser light L reflected by the reflective film R is absorbed in the laser absorption layer P. Therefore, the stripping efficiency of the second wafer W2 can be improved.

[0062] Furthermore, in the above embodiment, although the laser stripping process of the overlapping wafer T, i.e., the transfer process of the device layer D2 to the first wafer W1, is described, as mentioned above, the edge trimming process of the second wafer W2 can also be performed in the wafer processing system 1. The edge trimming of the second wafer W2 in the wafer processing system 1 will be described below.

[0063] First, the wafer cassette Ct placed on the wafer cassette placement stage 10 in the transport block G1 is removed from the overlapping wafer T by the wafer transport device 20, and then transferred to the wafer transport device 40 via the transport device 30 before being transported inside by the laser irradiation device 70.

[0064] As shown in FIG14(a), the interior of the second wafer W2 is irradiated with laser light L2 (YAG laser light) using an internal laser irradiation device 70, forming an edge modification layer M2 that serves as the base point for removing the edge portion We during edge trimming, as described later. Cracks C2 extend from the edge modification layer M2 in the thickness direction of the second wafer W2. The upper and lower ends of the cracks C2 reach, for example, the back side W2b and the front side W2a of the second wafer W2, respectively. The overlapping wafer T, in which the edge modification layer M2 is formed inside the second wafer W2, is then transported to the interface laser irradiation device 80 by a wafer transport device 40.

[0065] In the interface laser irradiation apparatus 80, wafer T is overlapped, and the bonding strength between the peeling promotion layer P2 in the edge portion We of the second wafer W2, which is the target of removal, and the second wafer W2 is reduced. Specifically, as shown in FIG14(b), laser light L (CO2 laser) is irradiated onto the laser absorption layer P, and stress is generated inside the laser absorption layer P closer to the radially outer side than the edge modification layer M2 formed by the internal laser irradiation apparatus 70. Furthermore, the generated stress, as shown in FIG14(c), is transmitted through the peeling promotion layer P2, thereby accumulating stress at the boundary between the second wafer W2 and the peeling promotion layer P2.

[0066] A peeling modification layer M1 is formed on the entire surface of the edge portion We, and the overlap wafer T with reduced bonding strength between the peeling promotion layer P2 and the second wafer W2 is then transported to the edge removal device 50 by the wafer transport device 40.

[0067] In the edge removal apparatus 50, the overlapping wafer T, as shown in Figure 14(d), uses the edge modifier layer M2 and the crack C2 as reference points to remove the edge portion We of the second wafer W2 (edge ​​trimming). Furthermore, the edge trimming method of the edge removal apparatus 50 can be arbitrarily selected. At this time, when removing the edge portion We, the bonding strength between the second wafer W2 and the release promoting layer P2 is reduced by the formation of the release modifier layer M1, thus simplifying the removal of the edge portion We.

[0068] The overlapping wafer T, whose edge We of the second wafer W2 has been removed, is then transported to the cleaning unit 60 by the wafer transport device 40. In the cleaning unit 60, the overlapping wafer T is brushed and cleaned. Afterwards, the fully processed overlapping wafer T is removed from the cleaning unit 60 by the wafer transport device 40, and then transported via the transfer device 30 and the wafer transport device 20 to the wafer cassette Ct of the wafer cassette platform 1. This completes one series of wafer processing steps in the wafer processing system 1.

[0069] As described above, according to the technology of the present invention, the bonding strength between the second wafer W2 and the peeling promotion layer P2 in the edge portion We can be reduced in the interface laser irradiation device 80, thereby allowing the edge portion We to be appropriately removed, i.e., edge trimming, in the edge removal device 50.

[0070] Furthermore, the processing sequence of the overlapping wafer T performed by the internal laser irradiation device 70 and the interface laser irradiation device 80 is not limited to the above-described embodiment. Alternatively, the edge portion We can be peeled off in the interface laser irradiation device 80, and then the edge modification layer M2 can be formed in the internal laser irradiation device 70.

[0071] It should be understood that the embodiments disclosed herein are illustrative and not restrictive. The aforementioned embodiments may also be omitted, replaced, or modified in various ways without departing from the scope and intent of the appended invention application.

[0072] 1: Wafer Processing System 10: Wafer cassette stage 20,40:Wafer transfer device 21,41:Conveyor Road 22,42:Conveying arm 30: Conveying device 50: Edge Removal Device 60: Cleaning device 70: Internal laser irradiation device 80: Interface laser irradiation device 90: Control device 100: Suction Cup 101: Air Bearing 102:Slide 103: Rotating mechanism 104: Mobile mechanism 105: Track 106:Abutment 110: Laser Head 111: Lens 120: Transport mat 200: Push-press component C2: Crack Ct, Cw1, Cw2: Wafer cassette D1, D2: Component Layer F1, F2: Surface film G1: Moving blocks in and out G2: Transfer Block G3: Process Blocks H: Recording Media L, L2: Laser light M1: Stripping the modified layer M2: Edge Modification Layer P: Laser absorption layer P2: Peeling Promotion Layer R: Reflective film R1: Unpeeled area T: Overlapping wafer W: Wafer W1: First wafer W2: Second wafer W1a, W2a: Front W1b, W2b: Back side We: Edge

Claims

1. A substrate processing apparatus for processing an overlay substrate formed by bonding a first substrate and a second substrate of a silicon-based substrate; the substrate processing apparatus comprising: a program storage unit for storing a program; a computer for reading the program from the program storage unit and running the program; a laser irradiation unit; and a peeling unit; wherein the program is a program that runs on the computer to cause the substrate processing apparatus to execute a substrate processing method; and a peeling promoting layer and a laser absorption layer are sequentially stacked on the second substrate from the second substrate side; the substrate processing method comprises the following steps: in the laser irradiation unit, stress is generated at the interface between the laser absorption layer and the peeling promoting layer by irradiating the laser absorption layer with laser light of a far-infrared wavelength from the second substrate side, thereby reducing the bonding strength between the laser absorption layer and the peeling promoting layer; and in the peeling unit, the second substrate is peeled from the first substrate along the boundary between the laser absorption layer and the peeling promoting layer.

2. The substrate processing apparatus as described in claim 1, wherein, On the second substrate, the release promoting layer, the laser absorption layer, the element layer, and the surface film bonded to the first substrate are stacked sequentially from the second substrate side.

3. The substrate processing apparatus as described in claim 2, wherein, A reflective film is formed between the laser absorption layer and the element layer on the second substrate.

4. The substrate processing apparatus as described in claim 2, wherein, A component layer comprising a plurality of components is formed on the first substrate.

5. The substrate processing apparatus as described in claim 4, wherein, A bonding surface film is further formed on the element layer of the first substrate, and the bonding surface film of the second substrate is bonded to the element layer of the first substrate via the bonding surface film.

6. The substrate processing apparatus as described in claim 5, wherein, The surface film of the first substrate and the second substrate is an oxide film.

7. The substrate processing apparatus as described in claim 5, wherein, The surface film of the first substrate is an adhesive.

8. The substrate processing apparatus as claimed in claim 1, wherein, The step of reducing the bonding strength between the laser absorption layer and the release promoting layer includes the following steps: forming a release modifier layer by irradiating the laser light in a pulsed manner; the release modifier layer leaves the stress at the interface between the laser absorption layer and the release promoting layer.

9. The substrate processing apparatus as claimed in claim 1, wherein, The thickness of the release-promoting layer is the residual film thickness due to the stress accumulated at the interface between the laser absorption layer and the release-promoting layer when the laser light is irradiated.

10. The substrate processing apparatus as claimed in claim 1, wherein, The laser absorption layer is composed of TEOS.

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