Composite wafer processing method

Abstract

To provide a method of processing a composite wafer in which a semiconductor wafer and a resin layer are laminated.SOLUTION: A processing method of a composite wafer W having a semiconductor wafer 10 having a plurality of streets 3 intersecting a first surface and a sealing resin layer 20 for sealing the back surface of the first surface includes: a step of attaching a tape T to the sealing resin layer side; a step of holding the composite wafer by a holding table via the tape to correct the warp; a step of imaging a first surface of the held composite wafer and detecting a position of each street; a half-cut step of forming a first groove at least deep enough to completely cut the semiconductor wafer along the street by a first cutting blade and release the warp; a step of imaging the first surface again and detecting the position of each first groove after performing the half-cut step; and a full cut step of cutting the composite wafer along the first groove with a second cutting blade 52a thinner than the width of the first groove to divide the composite wafer into individual chips.SELECTED DRAWING: Figure 12

Description

[Technical field]

[0001] The present invention relates to a method for processing a composite wafer in which the back surface of a semiconductor wafer is sealed with a resin. [Background technology]

[0002] 2. Description of the Related Art Conventionally, in processing a composite wafer having a semiconductor wafer and a resin layer, it is known to divide the wafer into chips by dicing using a step cut that cuts the semiconductor wafer and the resin layer in stages.

[0003] A cutting blade for semiconductor wafers is used to cut the semiconductor wafer portion, and a cutting blade for resin is used to cut the resin layer portion. In general, it is considered that a cutting blade with a coarser abrasive grain size than that of a cutting blade used to process semiconductor wafers is suitable for cutting the resin layer.

[0004] Furthermore, when cutting is performed by step cutting, in order to facilitate handling of the composite wafer, the composite wafer and the annular frame are attached to tape to form a wafer unit, and handling is performed in the state of the wafer unit.

[0005] On the other hand, one method for integrating multiple semiconductor devices into a single package is known as three-dimensional mounting, in which multiple semiconductor device chips are stacked vertically. Patent Document 1 discloses one such stacking method, COW (Chip On Wafer).

[0006] In the COW (Chip On Wafer) mounting method, multiple semiconductor devices are stacked and mounted on the back side of a semiconductor wafer via bumps, etc., and then sealed with resin to form a composite wafer. Then, streets (planned dividing lines) are detected for the composite wafer thus formed, and it is divided into chips by dicing using two types of cutting blades as described above. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2012-134231 A Summary of the Invention [Problem to be solved by the invention]

[0008] In the composite wafer formed by the COW mounting method described above, the thermal expansion coefficients of the semiconductor wafer and the encapsulation resin are different, so in many cases the entire wafer is warped due to heating during the resin encapsulation process.

[0009] When a warped composite wafer is attached to tape during cutting and held on a flat holding table, the warp is corrected and the wafer is flattened. However, when a cutting blade is used to cut a portion of the semiconductor wafer along the detected streets (planned dividing lines) in this flattened state to form grooves, the warp of the composite wafer is released and the grooves are positioned at locations that are displaced from the positions of the streets that were detected before cutting.

[0010] If the resin portion is fully cut with a resin cutting blade in this state, the cutting may occur at a location different from the street position detected before cutting, which may result in damage to the device portion.

[0011] In view of the above, the present invention proposes a novel technique for step processing of a composite wafer in which a semiconductor wafer and a resin layer are laminated. [Means for solving the problem]

[0012] The problem to be solved by the present invention has been described above, and the means for solving this problem will now be described.

[0013] According to one aspect of the present invention, a semiconductor wafer having a first surface on which a plurality of intersecting streets are formed; a sealing resin layer that seals a second surface side of the semiconductor wafer, which is the back surface of the first surface; A method for processing a composite wafer comprising: a tape adhering step of adhering a tape to the sealing resin layer side of the composite wafer; a holding step of holding the composite wafer on a holding table via the tape to correct warpage of the composite wafer; a street detection step of imaging the first surface of the semiconductor wafer of the composite wafer held by the holding table and detecting each position of each of the streets; a half-cut step of forming a first groove having a depth sufficient to completely cut the semiconductor wafer by a first cutting blade along each of the streets detected in the street detection step, thereby releasing the warpage; a groove detecting step of imaging the first surface again after the half-cutting step and detecting the positions of each of the first grooves; and a full cut step of cutting the composite wafer along each position of each of the first grooves detected in the groove detection step with a second cutting blade thinner than the width of the first grooves to divide the composite wafer into individual chip packages. Effect of the Invention

[0014] According to one aspect of the present invention, after performing a half-cut step of completely cutting the semiconductor wafer to form a first groove and release the warp of the composite wafer, the actual position of the first groove is detected, and the composite wafer is fully cut along the detected first groove. This allows the full cut to be performed accurately at a position that coincides with the position of the first groove corresponding to the actual street position, and allows the wafer to be divided into chip packages without damaging the device portion due to misalignment. [Brief description of the drawings]

[0015] [Figure 1]1A is a diagram showing an example of a composite wafer, and FIG. 1B is a diagram showing a state in which the composite wafer is warped. [Diagram 2] FIG. 2 is a diagram showing a cross section of a composite wafer. [Diagram 3] FIG. 2 is a diagram showing an example of a cutting device used for cutting the composite wafer. [Figure 4] 1 is a flowchart showing a flow of an embodiment of a processing method of the present invention. [Diagram 5] FIG. 2 is a diagram showing a configuration of a wafer unit. [Figure 6] 13 is a diagram showing a state in which the composite wafer is held on the holding table. FIG. [Figure 7] 1A and 1B are diagrams for explaining detection of streets extending in a first direction, and 1C and 1D are diagrams for explaining detection of streets extending in a second direction. [Figure 8] 10A and 10B are diagrams illustrating registration of target patterns for street detection, etc.; [Figure 9] FIG. 11 is a diagram illustrating a half-cut step. [Figure 10] 11A to 11C are diagrams illustrating how the semiconductor wafer is cut in the half-cut step. [Figure 11] 1A and 1B are diagrams illustrating detection of a first groove extending in a first direction, and 1C and 1D are diagrams illustrating detection of a first groove extending in a second direction. [Figure 12] 11A to 11C are diagrams illustrating how the resin is cut to form a second groove in a full-cut step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] FIG. 1(A) is a diagram showing a composite wafer W to be processed in the present invention. The composite wafer W is composed of a semiconductor wafer 10 having a first surface 10a, which is the front surface, on which a plurality of intersecting streets 3 are set, and a sealing resin layer 20 that seals the second surface 10b side of the semiconductor wafer 10, which is the back surface of the first surface 10a.

[0017] 1(B), warping occurs in the composite wafer W due to the difference in thermal expansion coefficient between the semiconductor wafer 10 and the encapsulating resin layer 20. In this example, the larger thermal expansion coefficient of the encapsulating resin layer 20 causes the lower encapsulating resin layer 20 to expand and the upper semiconductor wafer 10 to shrink, resulting in a warpage such that the center of the wafer as a whole bulges downward.

[0018] 2 is a cross-sectional view of the composite wafer W, showing a state where mounting has been performed in the form of COW (Chip On Wafer). A device D is formed on a semiconductor wafer 10, and a bump B is disposed on the front side of the device D. In addition, a plurality of device chips C are stacked on the back side of the device D via the bumps. Each stacked device chip C is sealed with resin R, and a sealing resin layer 20 is formed.

[0019] FIG. 3 is a diagram showing an example of a cutting device used for cutting the composite wafer W. As shown in FIG. The cutting device 50 has two cutting units 51 and 52 and is configured as a dual dicer, and can perform two-stage step cuts as described below. Note that step cuts may also be performed by using two cutting devices each equipped with one cutting unit and cutting with each cutting device in turn.

[0020] A holding table 60 is disposed on a base 55 of the cutting device 50. The holding table 60 is configured to move back and forth in the X-axis direction, which is the processing feed direction, by a moving mechanism (not shown), and is also configured to rotate within a horizontal plane by a rotating mechanism (not shown).

[0021] Wafer units U, each having a composite wafer W attached to a tape T, are successively supplied to the holding table 60, and the composite wafer W is suction-held via the tape T on the holding surface 62a of the holding table 60.

[0022] A gate-shaped column 56 is erected on a base 55, and the column 56 is provided with movement mechanisms 57, 58 that support the first cutting unit 51 and the second cutting unit 52 so that they can move in the Y-axis direction and the Z-axis direction, respectively. Each of the cutting units 51, 52 is provided with a cutting blade 51a, 52a that is rotationally driven by a motor (not shown).

[0023] Next, an embodiment of the method for processing a composite wafer according to the present invention will be described. Fig. 4 is a flow chart showing the flow of one embodiment of the processing method. Each step will be described in order below.

[0024] <Tape application step> As shown in FIG. 5, this is a step of attaching a tape T to the sealing resin layer 20 side of the composite wafer W.

[0025] In this embodiment, the sealing resin layer 20 of the composite wafer W is attached to the adhesive layer of the tape T. In addition, an annular frame F is attached to the tape T so as to surround the periphery of the composite wafer W, and a wafer unit U is formed in which the composite wafer W and the frame F are integrated.

[0026] <Retention step> As shown in FIG. 6, this is a step in which the composite wafer W is held on a holding table 60 via a tape T, and warpage of the composite wafer W is corrected.

[0027] As shown in FIG. 6, the holding table 60 is configured to include a porous plate 62 that forms a flat holding surface 62 a on its surface, and a clamp mechanism 64 .

[0028] The porous plate 62 is connected to a suction source 67 via a suction passage 65 and a control valve 66, and negative pressure is generated on the holding surface 62a by opening the control valve 66.

[0029] The clamp mechanism 64 clamps the frame F of the wafer unit U, so that the entire wafer unit U is held by the holding table 60 .

[0030] In the above configuration, when negative pressure is generated on the holding surface 62a, the composite wafer W is pulled toward the holding surface 62a via the tape T and is flattened along the flat holding surface 62a. This corrects the warpage that existed in the composite wafer W.

[0031] <Street detection step> As shown in FIGS. 6 and 7, this is a step of imaging the first surface 10a of the semiconductor wafer 10 of the composite wafer W held on the holding table 60 and detecting each position of each street 3.

[0032] In order to perform this street detection step, a target pattern for street detection and the positional relationship from the target pattern to the street are registered in advance in the controller 100 of the cutting device 50 shown in FIG.

[0033] 8, the target pattern Pt is the same pattern as the characteristic key pattern Pk formed on each device D, and during street detection, the key pattern Pk of each device D is detected by pattern matching with the registered target pattern Pt. In addition, a specified distance d1 from the key pattern Pk to the center of the street 3 extending in the first direction F1 (the planned division line) and a specified distance d2 from the key pattern Pk to the center of the street 3 extending in the second direction F2 (the planned division line) are also registered.

[0034] 6, in the street detection step, an image of the first surface 10a of the semiconductor wafer 10 is captured by an imaging camera 70 from above the holding table 60. Based on the captured image, a key pattern Pk (FIG. 8) is detected by pattern matching, and the position of street 3 (the position of the center of street 3) is detected from specified distances d1, d2 (FIG. 8).

[0035] As shown in Fig. 7(A)(B), the position of the street 3 is detected for all the streets extending in the first direction F1 and all the streets extending in the second direction F2. Specifically, as shown in Fig. 7(A), for example, for the street 3a extending in the first direction F1, one end side in the X-axis direction is imaged by the imaging camera 70, and then, as shown in Fig. 7(B), the composite wafer W is moved in the X-axis direction to image the other end side. In each image taken at a plurality of locations, a key pattern is detected by pattern matching, and the Y-axis direction coordinate of the street is determined by connecting points at a specified distance from each key pattern, and stored in the controller 100 (Fig. 3). Note that, if the determined street is not parallel to the X-axis direction, which is the processing feed direction, but is shifted, the deviation angle may also be stored.

[0036] After the position (Y-axis coordinate) and deviation angle of street 3a extending in first direction F1 are detected as described above, imaging camera 70 is moved in the Y-axis direction, and the position and deviation angle of adjacent street 3b are detected in a similar manner. After the positions, etc. of all streets extending in first direction F1 are detected, composite wafer W is rotated 90 degrees, and the positions, etc. of streets 3c, 3d, etc. extending in second direction F2 are detected in a similar manner, as shown in Figures 7(C) and (D).

[0037] In this manner, the positions and deviation angles of all the streets extending in the first direction F1 and the second direction F2 are detected and stored individually.

[0038] <Half cut step> As shown in Figures 9 and 10, this is a step in which a first groove M1 of a depth sufficient to completely cut at least the semiconductor wafer 10 is formed with the first cutting blade 51a along each street 3 detected in the street detection step, thereby releasing the warp of the composite wafer W.

[0039] Specifically, for the street to be cut, the position and deviation angle of the street (deviation angle from the X-axis direction, which is the processing feed direction) are referenced, and the first cutting blade 51a and the holding table 60 are appropriately moved to align the center position of the first cutting blade 51a in the thickness direction with the position of the street (Y-axis coordinate). and At the same time, the holding table 60 is rotated so that the direction of the street and the processing feed direction (X-axis direction) become parallel.

[0040] Next, the first cutting blade 51a is positioned at a height position for completely cutting the semiconductor wafer 10 and rotated at high speed, and the holding table 60 is processed and fed, thereby forming a first groove M1 (FIG. 10) along the street 3.

[0041] At the stage where the above-mentioned street detection step is completed, the streets extending in the second direction F2 in the composite wafer W are parallel to the X-axis direction, and first, first grooves M1 are formed in the streets extending in the second direction F2.

[0042] Specifically, after forming a first groove M1 for a certain street 3 extending in the second direction F2, the position and offset angle of the adjacent street 3 in the Y-axis direction is referenced, and a first groove M1 is formed in the same manner. After forming the first grooves M1 for all streets 3 extending in the second direction F2, the holding table is rotated 90 degrees, and first grooves M1 are formed in the same manner for all streets 3 extending in the first direction F1.

[0043] After completing the street detection step, the composite wafer W may be rotated 90 degrees, and the first groove may be formed first for the streets extending in the first direction F1, and then the first groove may be formed for the streets extending in the second direction F2.

[0044] As described above, by performing cutting processing by referring to the position and deviation angle for each street individually, even if the composite wafer W is warped, grooves can be accurately processed at positions that correspond to the actual positions of each street.

[0045] Then, by completely cutting the semiconductor wafer 10 by the first groove M1, the internal stress caused by the warping of the semiconductor wafer 10 is released, and it is possible to eliminate the warping that has occurred in the entire composite wafer W. When the first cutting blade 51a reaches the sealing resin layer 20, a part of the resin R is cut.

[0046] <Grove detection step> This is a step in which, after the half-cut step is performed, the first surface 10a of the semiconductor wafer 10 is imaged again to detect the positions of the first grooves M1.

[0047] Specifically, an imaging camera 70 (FIG. 6) captures images of the first grooves M1 formed on the first surface 10a of the semiconductor wafer 10, and as shown in FIGS. 11(A) to (D), the position and deviation angle (deviation angle from the X-axis direction, which is the processing feed direction) of each of the first grooves M1 extending in the first direction F1 and the second direction F2 are detected.

[0048] At the stage where the above-mentioned half-cut step is completed, the streets extending in the first direction F1 in the composite wafer W are parallel to the X-axis direction, and first, the first grooves M1 are detected on the streets extending in the first direction F1.

[0049] For this detection, first, a target pattern for detecting the first groove is registered in the controller 100 of the cutting device 50 shown in Fig. 2. Specifically, as shown in Fig. 11(A), an image of an area where the first groove M1 intersects is captured, and an image including a cross-shaped shadow is registered as the target pattern Pm.

[0050] Next, for example, as shown in FIG. 11(A), one end side in the X-axis direction of the first groove M1a extending in the first direction F1 is imaged by the imaging camera 70, and then, as shown in FIG. 11(B), the composite wafer W is moved in the X-axis direction to image the other end side. imageIn the above, the coordinates of the intersections of the first grooves are detected by pattern matching, and the Y-axis coordinate of the first groove M1a is determined by connecting the coordinates, and stored in the controller 100 (FIG. 2). Note that, if the determined first groove M1a is not parallel to the X-axis direction, which is the processing feed direction, but is shifted, the deviation angle may also be stored.

[0051] After the position (Y-axis coordinate) and deviation angle of the first groove M1a are detected as described above, the imaging camera 70 is moved and the position and deviation angle of the adjacent first groove M1b are detected in a similar manner. After the positions, etc. of all the first grooves extending in the first direction F1 are detected, the composite wafer W is rotated 90 degrees and the positions, etc. of the first grooves M1c, M1d, etc. extending in the second direction F2 are detected in a similar manner, as shown in Figures 11(C) and (D).

[0052] In this manner, the positions and deviation angles of all the first grooves extending in the first direction F1 and the second direction F2 are detected and stored individually.

[0053] <Full cut step> As shown in FIG. 12, this is a step in which the composite wafer W is cut along each position of each first groove M1 detected in the groove detection step with a second cutting blade 52a that is thinner than the width of the first groove M1 to divide it into individual chips Cp.

[0054] Specifically, for the first groove M1 to be cut, the position and deviation angle of the first groove (deviation angle from the X-axis direction, which is the processing feed direction) is referred to, and the second cutting blade 52a and the holding table 60 are moved appropriately to align the center position in the thickness direction of the second cutting blade 52a with the first groove, and the holding table 60 is rotated so that the direction of the first groove is parallel to the processing feed direction (X-axis direction).

[0055] Next, the second cutting blade 52a is positioned at a height position that reaches the tape T and rotated at high speed, and the holding table is processed and fed to cut the resin R of the sealing resin layer 20 along the first groove M1, thereby forming the second groove M2.

[0056] At the stage where the above-mentioned groove detection step is completed, the first groove extending in the second direction F2 in the composite wafer W is parallel to the X-axis direction, and first, a second groove M2 is formed on the street extending in the second direction F2.

[0057] Specifically, after forming a second groove M2 for a certain first groove M1 extending in the second direction F2, the position and deviation angle of the adjacent first groove M1 in the Y-axis direction is referenced and a second groove M2 is formed in the same manner. After forming the second grooves M2 for all first grooves M1 extending in the second direction F2, the holding table is rotated 90 degrees and the second grooves M2 are formed in the same manner for all first grooves M1 extending in the first direction F1.

[0058] After completing the groove detection step, the composite wafer W may be rotated 90 degrees, and a second groove may be formed first for the first groove extending in the first direction F1, and then a second groove may be formed for the first groove extending in the second direction F2.

[0059] As described above, by performing cutting processing while referring to the position and deviation angle for each first groove M1 individually, it is possible to perform groove processing accurately at a position that coincides with the actual position of each first groove M1.

[0060] Then, the composite wafer W is completely cut by the second grooves M2, so that it can be divided into individual chip packages Cp.

[0061] According to the processing method described above, after the half-cut step of completely cutting the semiconductor wafer 10 is performed to form the first grooves M1 and release the warp of the composite wafer W, the actual positions of the first grooves M1 are detected, and the composite wafer W is fully cut along the detected first grooves M1. This allows the full cut to be performed accurately at the positions that coincide with the positions of the first grooves M1 corresponding to the actual street positions, and allows the wafer to be divided into chip packages without damaging the device portion due to misalignment. [Explanation of symbols]

[0062] 3 Street 10. Semiconductor Wafers 10a 1st page 10b 2nd side 20 Sealing resin layer 50 Cutting equipment 51 Cutting unit 51a Cutting blade 52 Second cutting unit 52a Cutting blade 60 Holding Table 62 Porous Plate 62a Holding surface 70 Imaging camera 100 Controller B Bump C Device Chip Cp Chip Package D Device F Frame F1 1st direction F2 2nd direction M1 First Groove M2 Second Groove Pk key pattern Pm target pattern Pt target pattern R resin T-Tape U Wafer Unit W Composite wafer

Claims

1. a semiconductor wafer having a first surface on which a plurality of intersecting streets are defined; a sealing resin layer that seals a second surface side of the semiconductor wafer, which is the back surface of the first surface; A method for processing a composite wafer comprising: a tape adhering step of adhering a tape to the sealing resin layer side of the composite wafer; a holding step of holding the composite wafer on a holding table via the tape to correct warpage of the composite wafer; a street detection step of imaging the first surface of the semiconductor wafer of the composite wafer held by the holding table and detecting each position of each of the streets; a half-cut step of forming a first groove having a depth sufficient to completely cut the semiconductor wafer by a first cutting blade along each of the streets detected in the street detection step, thereby releasing the warpage; a groove detection step of imaging the first surface again after the half-cut step and detecting the positions of each of the first grooves by pattern matching using the image of the groove; a full cut step of cutting the composite wafer along each position of each of the first grooves detected in the groove detection step with a second cutting blade thinner than the width of the first grooves to divide the composite wafer into individual chip packages.

2. The groove detection step comprises: taking an image of an area where the first grooves intersect and registering an image including a cross-shaped shadow as a target pattern; performing pattern matching between each of the captured images captured at a plurality of locations and the target pattern, and detecting coordinates of locations where the first grooves intersect; 2. The method for processing a composite wafer according to claim 1, comprising:

Images