JP7550018B2 - Processing method and processing system - Google Patents

Description

This disclosure relates to a substrate processing method and processing system.

Patent Document 1 discloses a method for processing a bonded wafer. This method for processing a bonded wafer includes a step of detecting the outer edge position of the bonded wafer, and a step of cutting a rotating cutting blade into a desired position of the bonded wafer and rotating the chuck table to cut the wafer.

JP 2017-188599 A

The technology disclosed herein appropriately removes the peripheral portion of the first substrate to be removed in a laminated substrate in which a first substrate and a second substrate are bonded together, while suppressing damage to the second substrate during removal of the peripheral portion.

One aspect of the present disclosure is a method for treating a laminated substrate in which a first substrate and a second substrate are bonded together, the method including: preparing the laminated substrate with the first substrate, a target substrate for removing a peripheral portion, on an upper side; cutting the peripheral portion of the first substrate from the upper surface side while rotating the laminated substrate to a thickness less than a total thickness of the first substrate so as to leave a cutting remainder; after cutting so as to leave the cutting remainder, irradiating a laser beam onto the first substrate remaining in the thickness direction of the peripheral portion to remove the cutting remainder over the entire circumference of the peripheral portion ; and after removing the cutting remainder, grinding the first substrate from the upper side of the first substrate to a final finishing thickness, wherein the thickness of the cutting remainder is greater than the final finishing thickness of the first substrate after the full grinding .

According to the present disclosure, in a laminated substrate in which a first substrate and a second substrate are bonded together, it is possible to appropriately remove the peripheral portion of the first substrate to be removed, while suppressing damage to the second substrate during removal of the peripheral portion.

1 is a vertical cross-sectional view showing an example of a laminated wafer processed in a wafer processing system. 1 is a plan view illustrating a schematic configuration of a wafer processing system. FIG. 2 is a vertical cross-sectional view showing a schematic outline of the configuration of a cutting device. 1 is a vertical cross-sectional view showing a schematic outline of a configuration of a laser irradiation device. 1A to 1C are explanatory views showing main steps of a wafer processing according to the present embodiment. FIG. 2 is a flow chart showing main steps of wafer processing according to the present embodiment. FIG. 11 is a plan view showing an example of an irradiation position of laser light on a cutting remaining portion. 13 is a plan view showing another example of the irradiation position of the laser light on the cutting remaining portion. FIG. 13 is a plan view showing another example of the irradiation position of the laser light on the cutting remaining portion. FIG. FIG. 4 is an explanatory diagram showing details of a cutting remaining portion. 11A to 11C are plan views showing an example of an order of irradiation of laser light to a cutting remaining portion. 13A and 13B are explanatory views showing another example of removing the cutting remaining portion.

In recent years, in the manufacturing process of semiconductor devices, a semiconductor substrate having a plurality of electronic circuits or other devices formed on its surface and a supporting substrate are laminated together to form a laminated substrate, and the semiconductor substrate that forms the laminated substrate is thinned. In the following explanation, the substrate may be referred to as a "wafer."

Usually, the peripheral edge of a wafer is chamfered, but as described above, when a semiconductor wafer is thinned, the peripheral edge of the thinned semiconductor wafer may become sharply pointed (so-called knife-edge shape). This may cause chipping at the peripheral edge of the semiconductor wafer, which may damage the semiconductor wafers and support wafers that form the laminated wafer. Therefore, before the thinning process is performed, a process must be performed in advance to prevent the peripheral edge of the semiconductor wafer from becoming knife-edge-shaped, such as the edge trim disclosed in Patent Document 1.

However, when performing edge trimming of a semiconductor wafer using the method described in Patent Document 1, the entire thickness of the semiconductor wafer, which is the target for removing the peripheral portion, must be removed by the cutting blade, which places a large load on the edge trim and reduces the processing quality. Specifically, since the entire thickness of the semiconductor wafer is removed by cutting, in other words, the amount of cutting is large, the processing speed may be slow, which may cause a decrease in throughput, or the processing may require a large cost. In addition, in this case, it is necessary to use a cutting blade with a coarse surface grain size in order to suppress the decrease in throughput due to the edge trimming, but in such a case, the processed surface of the semiconductor wafer after the edge trimming (cutting process) becomes rough, which may lead to a decrease in processing quality.

In addition, it is generally difficult to properly control the movement of a cutting blade used to cut the peripheral portion of a semiconductor wafer in the thickness direction of the wafer. For this reason, in order to reliably remove the peripheral portion of the semiconductor wafer, it is necessary to cut below the bonding surface between the semiconductor wafer and the support wafer, i.e., the peripheral portion of the support wafer. In such cases, there are concerns about increased contamination caused by edge trimming, and the support wafer cannot be reused, which increases the cost of processing. Furthermore, when a laminated substrate is formed by bonding two semiconductor substrates together, cutting below the bonding surface in this way may damage devices formed on the semiconductor substrates.

The technology disclosed herein has been made in consideration of the above circumstances, and in a laminated substrate in which a first substrate and a second substrate are bonded together, the peripheral portion of the first substrate to be removed is appropriately removed, while suppressing damage to the second substrate during removal of the peripheral portion. Below, a wafer processing system as a processing system according to this embodiment, and a wafer processing method as a processing method, will be described with reference to the drawings. Note that in this specification and the drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and duplicated description will be omitted.

In the wafer processing system 1 according to this embodiment, which will be described later, a process is performed on a laminated wafer T, which is 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. In the wafer processing system 1, the peripheral portion We of the first wafer W is removed, and then the first wafer W is thinned by grinding. Hereinafter, in the first wafer W, the surface that is 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 that is 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. In addition, in the first wafer W, the region radially inward of the peripheral portion We to be removed is referred to as the center portion Wc.

The first wafer W is a semiconductor wafer such as a silicon substrate, and a device layer D including a plurality of devices is formed on the surface Wa. A bonding film Fw is further formed on the device layer D, and the device layer D is bonded to a bonding film Fs of the second wafer S through the bonding film Fw. Examples of the bonding film Fw include an oxide film (SiO ₂ film, TEOS film), a SiC film, a SiCN film, or an adhesive. The peripheral portion We of the first wafer W is chamfered, and the cross section of the peripheral portion We becomes thinner toward its tip. The peripheral portion We is a portion to be removed in edge trimming described later, and is, for example, in the range of 0.5 mm to 3 mm in the radial direction from the outer end of the first wafer W.

The second wafer S is, for example, a wafer supporting the first wafer W. A bonding film Fs is formed on the surface Sa of the second wafer S, and the peripheral portion is chamfered. Examples of the bonding film Fs include an oxide film (SiO ₂ 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 D of the first wafer W. The second wafer S does not need to be a support wafer, and may be a device wafer on which a device layer is formed similarly to the first wafer W. In this case, a bonding film Fs is formed on the surface Sa of the second wafer S via the device layer.

As shown in FIG. 2, the wafer processing system 1 has a configuration in which a loading/unloading station 2 and a processing station 3 are integrally connected. In the loading/unloading station 2, for example, a cassette C capable of housing multiple laminated wafers T is loaded and unloaded between the loading/unloading station 2 and the outside. The processing station 3 is equipped with various processing systems that perform the desired processing on the laminated wafers T.

The loading/unloading station 2 is provided with a cassette mounting table 10 on which a cassette C capable of storing multiple overlapping wafers T is mounted. In addition, a wafer transport device 20 is provided adjacent to the cassette mounting table 10 on the negative side of the X-axis of the cassette mounting table 10. The wafer transport device 20 moves on a transport path 21 extending in the Y-axis direction, and is configured to be able to transport overlapping wafers T between the cassette C on the cassette mounting table 10 and a transition device 30 described below.

In the loading/unloading station 2, a transition device 30 is provided adjacent to the wafer transport device 20 on the negative X-axis side of the wafer transport device 20 for transferring the laminated wafer T between the processing station 3 and the wafer transport device 20.

The processing station 3 is provided with, for example, three processing blocks B1 to B3. The first processing block B1, the second processing block B2, and the third processing block B3 are arranged in this order from the positive side of the X-axis (the loading/unloading station 2 side) to the negative side.

The first processing block B1 is provided with a cutting device 40 that cuts the peripheral portion We of the first wafer W, a cleaning device 50 that cleans the overlapped wafer T, and a wafer transport device 60. The cutting device 40 and the cleaning device 50 are arranged in a stacked manner. The wafer transport device 60 is arranged, for example, on the negative Y-axis side of the cutting device 40 and the cleaning device 50, and is configured to be able to transport the overlapped wafer T to the transition device 30, the cutting device 40, the cleaning device 50, and the laser irradiation device 70 described below.

As shown in FIG. 3, the cutting device 40 has a chuck 41 that holds the overlapped wafer T on its upper surface. The chuck 41 adsorbs and holds the back surface Sb of the second wafer S in a state in which the first wafer W is placed on the upper side and the second wafer S is placed on the lower side. The chuck 41 is also configured to be rotatable around a vertical axis by a rotation mechanism 42.

A cutting blade 43 is provided above the chuck 41, which performs a cutting process on the peripheral portion We of the first wafer W to remove it. The cutting blade 43 is configured to be movable in the horizontal and vertical directions by a moving mechanism (not shown), and cuts and removes the peripheral portion We by pressing it from the top surface (front surface Wa) side against the peripheral portion We of the first wafer W held by suction on the chuck 41.

In the cutting device 40, as described below, the peripheral edge portion We of the first wafer W is removed from the upper surface (front surface Wa) side with a cutting thickness smaller than the total thickness of the first wafer W. In other words, in the cutting device 40, the peripheral edge portion We of the first wafer W is not completely removed, but a cutting remainder Wer (see FIG. 5) of the desired thickness is left behind, and only a portion of the peripheral edge portion We is removed.

In this embodiment, the peripheral portion We of the first wafer W is removed using the cutting blade 43 in the cutting device 40. However, instead of such a cutting process, the peripheral portion We may be removed by a grinding process using, for example, a grinding wheel (not shown). In such a case, the peripheral portion We of the first wafer W is removed by grinding so as to leave a cutting remaining portion Wer of a desired thickness. In the following description, the "cutting process" includes such a grinding process using a grinding wheel (not shown). In other words, in the technology disclosed herein, "cutting" includes grinding performed using a grinding wheel.

The second processing block B2 is provided with a laser irradiation device 70 that irradiates a laser onto the peripheral portion We of the first wafer W cut by the cutting device 40, and a wafer transport device 80. The wafer transport device 80 is disposed, for example, on the positive Y-axis side of the laser irradiation device 70, and is configured to be able to transport the overlapped wafer T to the cutting device 40, the cleaning device 50, the laser irradiation device 70, and the processing device 90 described below.

As shown in FIG. 4, the laser irradiation device 70 has a chuck 71 that holds the overlapped wafer T on its upper surface. The chuck 71 adsorbs and holds the back surface Sb of the second wafer S in a state in which the first wafer W is placed on the upper side and the second wafer S is placed on the lower side. The chuck 71 is also configured to be rotatable around a vertical axis by a rotation mechanism 72.

A laser head 73 is provided above the chuck 71. The laser head 73 has a lens 74. The lens 74 is a cylindrical member provided on the underside of the laser head 73, and irradiates laser light Lr (e.g., a UV femtosecond laser) to the cutting remaining portion We remaining on the peripheral portion We of the first wafer W cut by the cutting device 40. The laser head 73 is configured to be movable in the horizontal and vertical directions by a moving mechanism (not shown), and is configured to be able to arbitrarily adjust the irradiation position of the laser light Lr on the cutting remaining portion Wer by, for example, a galvano scanner.

In the laser irradiation device 70, as described below, the cutting remaining portion We of the first wafer W is irradiated with laser light Lr, thereby removing the cutting remaining portion We by laser ablation. In other words, the cutting remaining portion We remaining in the cutting device 40 is removed, and the peripheral portion We of the first wafer W is completely removed.

The third processing block B3 is provided with a processing device 90.

The processing device 90 is provided with a rotating table 91. The rotating table 91 is configured to be freely rotatable around a vertical rotation center axis 92 by a rotation mechanism (not shown). Four chucks 93 are provided on the rotating table 91 for suction-holding the underside of the overlapped wafer T (the back surface Sb of the second wafer S). The four chucks 93 can be moved to the transfer position A0 and processing positions A1 to A3 by the rotation of the rotating table 91 around the rotation center axis 92. Each of the four chucks 93 is configured to be rotatable around a vertical axis by a rotation mechanism (not shown).

At the transfer position A0, the overlapped wafer T is transferred by the wafer transport device 80. At the processing position A1, a rough grinding unit 94 is disposed and performs rough grinding of the first wafer W. At the processing position A2, a medium grinding unit 95 is disposed and performs medium grinding of the first wafer W. At the processing position A3, a finish grinding unit 96 is disposed and performs finish grinding of the first wafer W to the final finishing thickness.

The wafer processing system 1 described above is provided with a control device 100. The control device 100 is, for example, a computer equipped with a CPU, memory, etc., 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 above program may be recorded on a computer-readable storage medium H and installed from the storage medium H into the control device 100.

Next, we will explain the wafer processing performed using the wafer processing system 1 configured as described above. In this embodiment, the first wafer W and the second wafer S are bonded together in a bonding device (not shown) external to the wafer processing system 1 to form a laminated wafer T in advance.

First, a cassette C containing multiple overlapping wafers T is placed on the cassette placement table 10 of the loading/unloading station 2. Next, the overlapping wafers T in the cassette C are removed by the wafer transfer device 20. The overlapping wafers T removed from the cassette C are transferred to the cutting device 40 via the transition device 30.

As shown in FIG. 5(a), the cutting device 40 rotates the overlapped wafer T (first wafer W) while abutting the cutting blade 43 against the peripheral portion We of the first wafer W from the top side, thereby cutting and removing the peripheral portion We from the top side (step P1 in FIG. 6).

Here, in this cutting process, it is desirable to completely remove the peripheral portion We of the first wafer W without damaging the second wafer S, i.e., to remove the peripheral portion We with a cutting thickness equal to the total thickness of the first wafer W. However, as described above, it is difficult to properly control the movement of the cutting blade 43 in the thickness direction (height direction) of the wafer, i.e., it is difficult to properly remove the peripheral portion We with a cutting thickness equal to the total thickness of the first wafer W.

Therefore, in the cutting process (step P1) of this embodiment, the peripheral portion We of the first wafer W is not completely removed, but rather a portion of the peripheral portion We is removed so as to leave a cutting remainder Wer of the desired thickness as shown in FIG. 5(a).

Here, the thickness of the cutting remainder We left on the peripheral portion We of the first wafer W is preferably greater than the final finishing thickness of the first wafer W after thinning by the processing device 90 (see the dashed line in FIG. 5) and is a thickness that can be appropriately removed by laser ablation, which will be described later. Specifically, taking into consideration the accuracy of the movement control in the height direction of the cutting blade 43 described above, it is desirable to leave the cutting remainder Wer with a thickness of, for example, about 10 μm to 50 μm.

As described above, the processed surface of the first wafer W becomes rough after the cutting process by the cutting blade 43, and therefore it is necessary to prevent this processed surface from remaining on the semiconductor wafer as a product. In this respect, in this embodiment, the upper surface of the cutting remnant Wer as the processed surface is removed together with the cutting remnant Wer by laser ablation in the laser irradiation device 70 described below. In addition, the side surface of the first wafer W as the processed surface that has been roughened by the cutting process by the cutting blade 43 is appropriately removed by the thinning process in the processing device 90 described below, since the cutting remnant Wer is formed to a thickness greater than the final finished thickness of the first wafer W.

The laminated wafer T, in which the peripheral portion We of the first wafer W has been cut, is then transferred to the cleaning device 50, where at least the peripheral portion We of the first wafer W (the portion cut in the cutting device 40) is cleaned (step P2 in FIG. 6). At this time, for example, the front surface Wa of the first wafer W and the back surface Sb of the second wafer S may also be cleaned.

The polymerized wafer T cleaned in the cleaning device 50 is then transported to the laser irradiation device 70.

As shown in FIG. 5(b), the laser irradiation device 70 aims at the surface of the cutting remainder We remaining on the peripheral portion We of the first wafer W, and irradiates the overlapped wafer T (first wafer W) with laser light Lr while rotating the overlapped wafer T (first wafer W). As a result, the cutting remainder We irradiated with the laser light Lr is removed by laser ablation (step P3 in FIG. 6).

In the laser ablation process of step P3, as described above, in order to completely remove the peripheral portion We of the first wafer W, the entire surface of the cutting remainder We remaining on the peripheral portion We is irradiated with laser light Lr.

Specifically, the overlapped wafer T (first wafer W) is rotated, and the laser head 73 periodically irradiates the laser light Lr while moving the irradiation position of the laser light Lr in the radial direction by a galvano scan (not shown). This allows the laser light Lr to be irradiated onto the entire surface of the remaining cutting portion Wer, i.e., the remaining cutting portion Wer (periphery We) can be completely removed from the first wafer W.

In addition, at this time, adjustment of the irradiation position of the laser light Lr in the height direction is easier than adjusting the position of the cutting blade 43 in the height direction described above, and the peripheral portion We can be appropriately removed to a thickness equal to the total thickness of the first wafer W. Therefore, damage to the second wafer S during removal of the peripheral portion We, as in the conventional method, is suppressed.

The position at which the laser light Lr is irradiated onto the cutting remaining portion Wer can be determined arbitrarily as long as the entire surface of the cutting remaining portion Wer can be irradiated with the laser light Lr.
For example, by moving the irradiation position of the laser light Lr in the radial direction (width direction) of the cutting remaining portion Wer as the overlapping wafer T rotates, the irradiation position of the laser light Lr on the cutting remaining portion Wer may be arranged in a spiral shape in a planar view, as shown in Figure 7A.
Furthermore, for example, by repeatedly rotating the overlapped wafer T once and then moving the irradiation position of the laser light Lr in the radial direction, the irradiation position of the laser light Lr on the cutting remaining portion Wer may be arranged concentrically in a planar view, as shown in Figure 7B.
Furthermore, for example, as shown in FIG. 7C, the irradiation position of the laser light Lr may be moved so as to reciprocate (scan) many times in the radial direction while the laminated wafer T makes one rotation.

As shown in FIG. 1, the peripheral portion We of the first wafer W has been chamfered, so when the peripheral portion We is cut from the top surface side in step P1, the cross section of the cutting remaining portion Wer becomes thinner toward its tip. Specifically, as shown in FIG. 8, the thickness H1 of the cutting remaining portion Wer on the radially inner side (the central portion Wc side) is greater than the thickness H2 on the radially outer side (the outer end side). For this reason, if the entire surface of the cutting remaining portion Wer is irradiated with laser light Lr under the same conditions, there is a risk that the cutting remaining portion Wer may not be properly removed, especially on the radially inner side.

Therefore, in the edge trimming process according to this embodiment, the irradiation conditions of the laser light Lr are adjusted according to the thickness (volume) of the cutting remnant Wer at the irradiation position of the laser light Lr, and the cutting remnant Wer is appropriately removed. Specifically, for example, the output of the laser light Lr is increased on the radially inner side where the cutting remnant Wer is thicker, and the output of the laser light Lr is decreased on the radially outer side where the cutting remnant Wer is thinner. As a result, even if the thickness of the cutting remnant Wer varies in the radial direction as shown in FIG. 8, the cutting remnant Wer can be appropriately removed.

The thickness of the cutting remainder Wer may be measured, for example, inside the cutting device 40 after the cutting process, or may be measured before irradiation with the laser light Lr in the laser irradiation device 70.

In the above example, the output of the laser light Lr was adjusted according to the thickness of the cutting remaining portion Wer, but in addition to or instead of adjusting the output, for example, the irradiation time of the laser light Lr may be further adjusted according to the thickness of the cutting remaining portion Wer. That is, the irradiation time of the laser light Lr may be longer on the radially inner side where the cutting remaining portion Wer is thicker, and the irradiation time of the laser light Lr may be shorter on the radially outer side where the cutting remaining portion Wer is thinner.

For example, the number of times the laser light Lr is irradiated may be further adjusted according to the thickness of the cutting remaining portion Wer. That is, by rotating the overlapped wafer T, the number of times the laser light Lr is irradiated may be increased on the radially inner side where the cutting remaining portion Wer is thicker, and the number of times the laser light Lr is irradiated may be decreased on the radially outer side where the cutting remaining portion Wer is thinner.

Here, when the cutting remnant Wer is removed by laser ablation, debris d is generated, which is mainly composed of the cutting remnant Wer that was removed when the laser light Lr was irradiated, as shown in FIG. 5(b). If the debris d thus generated adheres to the laminated wafer T, it may scatter during processing or transportation of the laminated wafer T, which may cause malfunctions in wafer processing or contamination within the system.

Here, the debris d generated by irradiation with the laser light Lr tends to diffuse toward the open space near the irradiation position of the laser light Lr. That is, for example, when the first laser light Lr is irradiated near the center in the width direction of the cutting remaining portion Wer, the debris d diffuses in the entire circumferential direction centered on the irradiation position of the laser light Lr. On the other hand, when the first laser light lr is irradiated near the outer edge of the cutting remaining portion Wer, the debris d tends to diffuse toward the outside in the circumferential direction of the overlapped wafer T, which is the open space.

In view of the above trends, it is preferable to remove the cutting remaining portion Wer by laser ablation sequentially from the radial outer side to the radial inner side of the cutting remaining portion Wer as shown in FIG. 9.

Specifically, when removing the cutting remaining portion Wer with the laser light Lr, the laser light Lr is first irradiated to an irradiation position Pt(1) of the laser light Lr located near the outer end of the cutting remaining portion Wer, and the cutting remaining portion Wer at the irradiation position Pt(1) is removed. At this time, since the cutting remaining portion Wer where the irradiation position Pt(1) is located faces an open space on the outer side in the peripheral direction of the overlapped wafer T, the generated debris d is diffused into the open space.

After the cutting remnant Wer is removed at irradiation position Pt(1), the overlapped wafer T rotates and the laser light Lr is irradiated to irradiation position Pt(2). Irradiation position Pt(2) is set adjacent to irradiation position Pt(1). At this time, irradiation position Pt(2) faces irradiation position Pt(1) where the cutting remnant Wer has already been removed, which prevents the debris d from diffusing radially inward of the overlapped wafer T. By repeating this series of irradiation operations of the laser light Lr and rotation operations of the overlapped wafer T, the cutting remnant Wer can be removed over the entire circumference of the peripheral portion We without the debris d adhering to the overlapped wafer T.

The laser irradiation device 70 may further be provided with an exhaust mechanism (e.g., a vacuum pump) (not shown) for sucking and collecting the generated debris d. By operating the exhaust mechanism when irradiating the cutting remaining portion Wer with laser light, the adhesion of debris d to the overlapped wafer T can be further appropriately suppressed.

In the above description, the entire surface of the cutting remaining portion Wer is irradiated with the laser light Lr, but the entire surface of the cutting remaining portion Wer does not necessarily need to be irradiated with the laser light Lr. Specifically, as shown in FIG. 8, the thickness H1 of the cutting remaining portion Wer on the radial inner side (the central portion Wc side) is greater than the thickness H2 on the radial outer side (the outer end side). As a result, the cutting remaining portion Wer has a bonding region R1 (see FIG. 8) that is actually bonded to the second wafer S via the device layer D and the bonding film F, and an unbonded region R2 (see FIG. 8) that is separated from the second wafer S on the radial outer side of the bonding region R1.

When removing the cutting remnant Wer by laser ablation, if the cutting remnant Wer is removed at least in the bonding region R1, the cutting remnant Wer in the non-bonded region R2 located on the outer periphery can be removed by dropping it under its own weight, as shown in FIG. 10. In this way, by controlling the irradiation of the laser light Lr only to the bonding region R1, the throughput of the laser ablation can be improved.

Returning to the explanation of Figures 5 and 6, the laminated wafer T from which the cutting residue Wer has been completely removed by laser ablation is then transferred to the cleaning device 50, where the back surface Wb of the first wafer W and the back surface Sb of the second wafer S are cleaned (step P4 in Figure 6).

The laminated wafer T cleaned in the cleaning device 50 is then transported to the transfer position A0 of the processing device 90. Next, the turntable 91 is rotated to move the laminated wafer T held by the chuck 93 sequentially to the processing positions A1 to A3. In the processing device 90, as shown in FIG. 5(c), various grinding processes are performed on the first wafer W to thin the first wafer W to a final finishing thickness.

At processing position A1, the rough grinding unit 94 roughly grinds the back surface Wb of the first wafer W (step P5 in FIG. 6). At processing position A2, the medium grinding unit 95 medium grinds the back surface Wb of the first wafer W (step P6 in FIG. 6). At processing position A3, the finish grinding unit 96 finishes the back surface Wb of the first wafer W (step P7 in FIG. 6).

The first wafer W is then thinned to its final finishing thickness, resulting in a laminated wafer T, which is then moved to the transfer position A0 by rotating the rotary table 91.

The overlapped wafer T that has been moved to the transfer position A0 is then transferred to the cleaning device 50, where the back surface Wb of the first wafer W and the back surface Sb of the second wafer S are cleaned (step P8 in FIG. 6).

The laminated wafer T cleaned in the cleaning device 50 is then transferred to the cassette C via the transition device 30, thus completing the series of wafer processing steps in the wafer processing system 1.

When the second wafer S is a support wafer as in this embodiment, the laminated wafer T, which has been subjected to all wafer processing in the wafer processing system 1, is then separated into the first wafer W and the second wafer S in a separation device (not shown) provided outside the wafer processing system 1. The separated first wafer W is transported to the next process in the semiconductor device manufacturing process. The separated second wafer S is, for example, bonded to another first wafer W before the peripheral portion We is removed, that is, reused as a support wafer for the other first wafer W.

According to the above embodiment, the cutting device 40 does not completely remove the peripheral portion We, but leaves a part of it as a cutting remainder Wer of a desired thickness. Then, the cutting remainder Wer is removed by irradiating the laser light Lr in the laser irradiation device 70, thereby completely removing the peripheral portion We of the first wafer W, i.e., the formation of a knife-edge shape on the peripheral portion of the first wafer W is suppressed.

Furthermore, according to this embodiment, the final removal of the peripheral portion We is performed by irradiating the laser light Lr instead of using a cutting blade, so that the side surface of the first wafer W and the surface Sa of the second wafer S are prevented from becoming rough after the peripheral portion We is removed, which means that deterioration of the processing quality can be prevented.

At this time, adjusting the irradiation position of the laser light Lr in the height direction is easier than adjusting the position in the height direction of a conventional cutting blade, so the peripheral portion We can be appropriately removed to a thickness equal to the total thickness of the first wafer W. This prevents damage to the second wafer S when removing the peripheral portion We as in the conventional case, and thus prevents contamination caused by cutting the second wafer S.

Furthermore, when the second wafer S is a support wafer as in this embodiment, damage to the second wafer S is suppressed in this manner, and the second wafer S can be reused by rebonding it to another first wafer W, thereby reducing the cost of processing.

The thickness of the cutting remainder We left on the peripheral portion We of the first wafer W varies depending on the position in the width direction (radial direction) of the cutting remainder We. In this embodiment, the irradiation conditions of the laser light Lr (e.g., at least one of the output of the laser light Lr, the irradiation time, or the number of irradiations) are adjusted according to the thickness (volume) of the cutting remainder Wer. This makes it possible to appropriately remove the cutting remainder Wer from the first wafer W even if the thickness of the cutting remainder Wer to be removed varies.

In addition, in this embodiment, in the irradiation of the laser light Lr, the laser light Lr is sequentially irradiated from the radial outside to the radial inside of the cutting remaining portion Wer, thereby preventing debris d generated by the irradiation of the laser light Lr from adhering to the overlapped wafer T. This prevents contamination of the overlapped wafer T or the inside of the wafer processing system 1 during processing or transportation of the overlapped wafer T in the subsequent process, and allows wafer processing in the wafer processing system 1 to be performed appropriately.

In order to properly remove the cutting remnant Wer, it is desirable to calculate the amount of eccentricity of the cutting remnant Wer formed on the first wafer W or the amount of eccentricity of the holding position of the overlapped wafer T relative to the chuck 71 in the laser irradiation device 70 prior to irradiating the cutting remnant Wer with laser light (step P3 in FIG. 6), and then irradiate the cutting remnant Wer with laser light (step P3 in FIG. 6) in accordance with the calculated amount of eccentricity.

When calculating the amount of eccentricity, first, a camera for imaging the amount of eccentricity (hereinafter simply referred to as the "imaging camera") that is separately provided inside the laser irradiation device 70 is moved above the overlapped wafer T held by the chuck 71. The imaging camera is positioned above the boundary (hereinafter sometimes simply referred to as the "boundary") between the center portion Wc and the peripheral portion We of the first wafer W, i.e., above the radially inner end of the cutting remainder Wer formed by the cutting device 40.

Next, the imaging camera captures an image of the boundary portion in the circumferential direction of the first wafer W at 360 degrees. The captured image is output from the imaging camera to the control device 100. The control device 100 calculates, from the image captured by the imaging camera, the amount of eccentricity of the boundary portion relative to the rotation axis of the chuck 71, in other words, the amount of eccentricity of the cutting remaining portion Wer relative to the rotation axis of the chuck 71, over the entire circumference of the first wafer W.

Then, when the laser light Lr is irradiated onto the remaining cutting portion Wer in step P3, eccentricity correction is performed based on the amount of eccentricity calculated in this manner. The method of eccentricity correction is not particularly limited, and for example, the chuck 71 may be moved horizontally based on the calculated amount of eccentricity, or the laser head 73 may be moved horizontally. Also, for example, only the irradiation position of the laser light Lr may be moved in the width direction (radial direction) of the remaining cutting portion Wer by galvano scanning.

In this way, when the laser light Lr is irradiated onto the cutting remaining portion Wer, eccentricity correction is performed based on the calculated amount of eccentricity, thereby enabling the cutting remaining portion Wer to be removed more appropriately.

The method of calculating the amount of eccentricity is not limited to imaging using an imaging camera as described above, and any method can be used as long as it can properly calculate the amount of eccentricity of the cutting remaining part Wer relative to the rotation axis of the chuck 71. In the above explanation, the amount of eccentricity is calculated in the laser irradiation device 70, but the amount of eccentricity may be calculated outside the laser irradiation device 70, for example, in the cutting device 40. However, even if the peripheral part We is properly cut in the cutting device 40 as described above, the overlapped wafer T may be held eccentrically relative to the chuck 71 in the laser irradiation device 70. From this point of view, it is preferable that the amount of eccentricity is calculated in the laser irradiation device 70.

In addition, in the above example, eccentricity correction (feedback control) was performed based on the calculated amount of eccentricity, but it is also possible to irradiate the remaining cutting portion Wer with laser light Lr while capturing an image of the boundary portion with an imaging camera without performing feedback control.

As described above, in this embodiment, the laser light is irradiated onto the cutting remaining portion Wer before the first wafer W is thinned, and the thickness of the cutting remaining portion Wer is controlled to be greater than the final finish thickness of the first wafer W. This makes it possible to obtain better processing quality on the side surface of the first wafer W after removal of the peripheral portion We and on the surface Sa of the second wafer S without leaving any cutting marks on the side surface of the first wafer W after the thinning process.

In the above embodiment, the irradiation position of the laser light Lr on the remaining cutting portion Wer is adjusted using a galvano scan or the like, but the method of adjusting the irradiation position is not limited to this. For example, the adjustment may be performed by moving the laser head 73 horizontally using a moving mechanism (not shown), or the adjustment may be performed by moving the chuck 71 horizontally.

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

REFERENCE SIGNS LIST 1 Wafer processing system 70 Laser irradiation device 73 Laser head Lr Laser light T Overlapped wafer W First wafer S Second wafer We Periphery Wer Remaining cutting portion

Claims (11)

A method for treating a laminated substrate in which a first substrate and a second substrate are bonded together, comprising the steps of:
preparing the laminated substrate with the first substrate, the first substrate being a target for removing a peripheral portion, facing up;
cutting a peripheral portion of the first substrate from an upper surface side to a thickness less than a total thickness of the first substrate while rotating the laminated substrate, so that a cutting remainder remains ;
after cutting so that the cutting remainder remains, irradiating the first substrate remaining in the thickness direction of the peripheral edge portion with a laser light to remove the cutting remainder over the entire circumference of the peripheral edge portion ;
After removing the cutting residue, grinding the entire surface of the first substrate from the upper side of the first substrate to a final finish thickness;
A processing method , wherein a thickness of the cutting remainder is greater than the final finished thickness of the first substrate after the entire surface is ground . 2. The method according to claim 1, wherein the thickness of the cutting remainder is 10 to 50 μm. After the entire surface of the first substrate is ground, the first substrate is peeled off from the second substrate;
3. The processing method according to claim 1, wherein the second substrate peeled off from the first substrate is reused by being bonded to another first substrate before the peripheral portion is removed. The processing method according to any one of claims 1 to 3 , wherein the laser light is irradiated onto the cutting remaining portion while rotating the laminated substrate so that the irradiation positions of the laser light are arranged in a spiral shape in a plan view of the peripheral portion. The processing method according to claim 4 , wherein the laser light is irradiated sequentially from a radially inner side to a radially outer side of the remaining cut portion . The processing method according to any one of claims 1 to 3, wherein the laser light is irradiated onto the remaining cutting portion by moving the irradiation position of the laser light back and forth in a radial direction in a plan view of the peripheral portion while rotating the laminated substrate once . The processing method according to any one of claims 1 to 6 , wherein at least one of an output of the laser light and an irradiation time of the laser light is adjusted according to a thickness of the remaining cutting portion at the irradiation position of the laser light. An apparatus for processing a laminated substrate in which a first substrate and a second substrate are bonded together, comprising:
The first substrate, which is the target for removing the peripheral portion, is cut so that the bonding surface side of the first substrate and the second substrate in the peripheral portion is left with a thickness less than the total thickness of the first substrate so that the first substrate remains with a desired thickness, and a cutting remainder is left from the upper surface side of the entire periphery of the first substrate,
a laser irradiation device that irradiates the first substrate remaining on the peripheral portion with a laser beam after the first substrate has been cut so that the cutting remaining portion remains , thereby removing the entire cutting remaining portion remaining on the first substrate;
a processing device that thins the first substrate from above the first substrate to a final finish thickness after removing the cutting residue,
The thickness of the cut remainder is greater than the final finish thickness . The processing system according to claim 8 , wherein the thickness of the cutting remainder is 10 to 50 μm. a cutting device including a blade for cutting a peripheral portion of the first substrate;
10. The processing system according to claim 8 or 9, wherein the cutting device prepares the laminated substrate so that the first substrate is on an upper side, contacts the blade from above the first substrate, and removes the peripheral portion until the peripheral portion has the desired thickness. A control device for controlling the operation of the laser irradiation device,
The control device includes:
The processing system according to any one of claims 8 to 10, wherein the operation of the laser irradiation device is controlled so as to adjust at least one of the output of the laser light or the irradiation time of the laser light according to the thickness of the cutting remaining portion at the irradiation position of the laser light.

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