JP6195483B2 - Laminated wafer processing method - Google Patents

Description

  The present invention relates to a method for processing a laminated wafer in which a plurality of wafers are laminated.

  In recent years, a wiring technique called a TSV process that realizes electrical connection using a through silicon via (TSV: Through Silicon Via) formed so as to penetrate a silicon wafer has been put into practical use (for example, Patent Document 1, Patent Reference 2).

  In the TSV process, for example, a device wafer on which a through electrode is formed together with a device such as an IC is bonded to a support wafer serving as a support member, and then the device wafer is ground to expose the through electrode. The exposed through electrode is used for device connection and the like.

  As described above, the TSV process uses the through electrode formed integrally with the device wafer for electrical connection, so it is advantageous for downsizing the apparatus as compared with a method such as wire bonding in which wiring is formed outside. is there.

JP 2001-53218 A JP 2005-136187 A

  By the way, in the above-mentioned TSV process, a film may be formed by spin coating on the ground surface of a ground device wafer. However, since spin coating diffuses a chemical (for example, resist material) by the centrifugal force generated by the rotation of the device wafer, there is a problem that the chemical accumulates on the outer peripheral edge of the device wafer and a thick film tends to be formed locally. It was.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a method for processing a laminated wafer that can prevent a film formed by spin coating from becoming thicker at the outer periphery. is there.

According to the present invention, there is provided a method for processing a laminated wafer in which a first wafer is laminated on a second wafer, wherein the second wafer side of the laminated wafer is held, and the first wafer is ground by a grinding means. A thinning step for thinning to a thickness, a processing step for performing processing on the ground surface of the first wafer after performing the thinning step, and before or after performing the thinning step A step of forming a truncated cone on the outer peripheral side surface of the laminated wafer before the step is formed with a truncated cone having a diameter-increasing inclined portion that increases in diameter from the first wafer toward the second wafer; in the processing step, the resist coating is performed by spin-coating onto the ground surface of the first wafer, the said truncated cone forming step, One was cut with a cutting blade which rotates on the outer periphery of said first wafer Processing method of a multilayer wafer, comprising forming a increased in diameter inclined portion by rotating the laminated wafer moves the said cutting blade radially outwardly of the first wafer is provided.

  In the method for processing a laminated wafer according to the present invention, a cutting blade is cut into the laminated wafer, and a truncated cone having an enlarged diameter inclined portion is formed on the outer peripheral side surface. It can be actively removed through the enlarged diameter inclined part.

  That is, since it is difficult for the chemical solution to accumulate on the outer peripheral edge of the wafer, the formed film does not have to be thick at the outer peripheral edge. Thus, according to the present invention, the film formed by spin coating can be prevented from becoming thick at the outer peripheral edge.

FIG. 1A is a perspective view schematically showing a configuration example of a device wafer constituting a laminated wafer, and FIG. 1B is a perspective view schematically showing a state in which the laminated wafer is formed. . It is a partial cross section side view which shows a thinning step typically. FIG. 3A is a partial cross-sectional side view schematically showing the truncated cone forming step, and FIG. 3B is a plan view schematically showing the truncated cone forming step. It is a partial cross section side view which shows typically the shape of the laminated wafer processed by the truncated cone formation step. It is a partial cross section side view which shows a processing step typically.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. The laminated wafer processing method according to the present embodiment includes a thinning step (see FIG. 2), a truncated cone forming step (see FIGS. 3 and 4), and a processing step (see FIG. 5).

  In the thinning step, the device wafer side of the laminated wafer in which the device wafer (first wafer) and the support wafer (second wafer) are laminated is ground. In the truncated cone forming step, a cutting blade is cut into the laminated wafer to form an enlarged inclined portion on the outer peripheral side surface, and the laminated wafer is processed into a truncated cone shape.

  In the processing step, a resist film is formed by spin coating on the surface to be ground of the device wafer ground in the thinning step. Hereinafter, the processing method of the laminated wafer according to the present embodiment will be described in detail.

  FIG. 1A is a perspective view schematically showing a configuration example of a device wafer constituting a laminated wafer, and FIG. 1B is a perspective view schematically showing a state in which the laminated wafer is formed. .

  As shown in FIG. 1A, the device wafer (first wafer) 11 is a disk-shaped semiconductor wafer, and on the surface 11a side, a central device region 13 and an outer peripheral surplus region 15 surrounding the device region 13 are provided. And are provided.

  The device region 13 is divided into a plurality of regions by streets (division planned lines) 17 arranged in a lattice pattern, and a device 19 such as an IC is formed in each region. The outer peripheral portion 11c of the wafer 11 is chamfered, and the cross-sectional shape is an arc shape (see FIG. 2).

  As shown in FIG. 1B, the support wafer (second wafer) 21 is a disk-shaped plate having an outer diameter equivalent to that of the device wafer 11, and is a resin (not shown) that functions as an adhesive. It adheres to the device wafer 11 via

  Specifically, the device wafer 11 and the support wafer 21 are overlapped and bonded so that the surface 11a side of the device wafer 11 and the surface 21a side of the support wafer 21 face each other. Thereby, a laminated wafer 23 in which the device wafer 11 and the support wafer 21 are laminated is formed.

  Note that the laminated wafer 23 may be formed by a method such as bonding without using an adhesive. For example, after hydrophilizing the surfaces related to the bonding of the device wafer 11 and the support wafer 21, the surfaces are brought into contact with each other and pressed. Thereby, the hydrogen bond can be advanced from the contact part, and the device wafer 11 and the support wafer 21 can be joined.

  As the support wafer 21, a semiconductor wafer similar to the device wafer 11 can be used. However, any plate-like object that can appropriately support the device wafer 11 can be used as the support wafer 21. For example, a glass substrate, a metal substrate, a resin substrate, or the like may be used as the support wafer 21.

  In the laminated wafer processing method according to the present embodiment, first, a thinning step for thinly processing the device wafer 11 of the laminated wafer 23 described above is performed. FIG. 2 is a partial cross-sectional side view schematically showing the thinning step. This thinning step is performed by, for example, the grinding apparatus 2 shown in FIG.

  The grinding device 2 includes a spindle 4 that rotates around a rotation axis C1 extending in the vertical direction. The spindle 4 is lifted and lowered by a lifting mechanism (not shown). A disc-shaped wheel mount 6 is provided on the lower end side of the spindle 4, and a grinding wheel (grinding means) 8 is fixed to the wheel mount 6.

  The grinding wheel 8 includes a wheel base 8a formed of a metal material such as aluminum or stainless steel. A plurality of grinding wheels 8b are fixed to the entire annular lower surface of the wheel base 8a.

  A chuck table 10 is disposed below the grinding wheel 8. The chuck table 10 is connected to a rotation mechanism (not shown) such as a motor and rotates around a rotation axis C <b> 2 extending in the vertical direction like the spindle 4.

  The surface of the chuck table 10 is a holding surface for sucking and holding the laminated wafer 23. A negative pressure of a suction source (not shown) acts on the holding surface through a flow path (not shown) formed inside the chuck table 10 to generate a suction force for sucking the laminated wafer 23.

  In the thinning step, first, the back surface 21b side of the support wafer 21 is brought into contact with the holding surface of the chuck table 10 to apply a negative pressure of the suction source. Thereby, the laminated wafer 23 is sucked and held on the chuck table 10.

  Next, the spindle 4 is lowered while rotating the spindle 4 and the chuck table 10 in predetermined rotation directions R1 and R2, respectively, and the grinding wheel 8b is brought into contact with the back surface 11b of the device wafer 11.

  The rotation speed of the spindle 4 is set to, for example, 6000 rpm, and the rotation speed of the chuck table 10 is set to, for example, 300 rpm. However, the rotation speeds of the spindle 4 and the chuck table 10 are not limited to these.

  By lowering the spindle 4 at a predetermined feed rate, the back surface 11b of the device wafer 11 is ground. This grinding is performed while measuring the thickness of the device wafer 11 with a contact-type or non-contact-type thickness measurement sensor. When the device wafer 11 has a predetermined thickness (for example, 100 μm), the thinning step ends.

  After performing the thinning step, a truncated cone forming step for processing the laminated wafer 23 into a truncated cone shape is performed. 3A is a partial sectional side view schematically showing the truncated cone forming step, FIG. 3B is a plan view schematically showing the truncated cone forming step, and FIG. It is a partial cross section side view which shows typically the shape of the lamination | stacking wafer 23 processed by the base formation step. This thinning step is performed by, for example, the cutting device 12 shown in FIG.

  The cutting device 12 includes a spindle 14 that rotates around a rotation axis C3 that extends in the horizontal direction. The spindle 14 is moved up and down by an elevating mechanism (not shown) and is moved in an indexing and feeding direction parallel to the rotation axis C3 by a moving mechanism (not shown). An annular cutting blade 16 is attached to one end side of the spindle 4.

  A chuck table 18 is disposed below the cutting blade 16. The chuck table 18 is connected to a rotation mechanism (not shown) such as a motor, and rotates around a rotation axis C4 extending in the vertical direction. The chuck table 18 is connected to a moving mechanism (not shown) and is moved in a machining feed direction perpendicular to the index feed direction.

  The surface of the chuck table 18 is a holding surface for sucking and holding the laminated wafer 23. A negative pressure of a suction source (not shown) acts on the holding surface through a flow path (not shown) formed inside the chuck table 18 to generate a suction force for sucking the laminated wafer 23. A rotary joint or the like is used for the flow path of the chuck table 18. Thereby, the chuck table 18 can be rotated in a predetermined direction without limitation.

  In the truncated cone forming step, first, the back surface 21b side of the support wafer 21 is brought into contact with the holding surface of the chuck table 18 to apply a negative pressure of the suction source. Thereby, the laminated wafer 23 is sucked and held on the chuck table 18.

  Next, the spindle 14 is lowered while rotating the spindle 14 and the chuck table 18 in predetermined rotation directions R3 and R4, respectively, and the cutting blade 16 is moved from the back surface 11b side of the device wafer 11 to the vicinity of the outer peripheral portion 11c. Cut it. At the same time, the cutting blade 16 is moved in the index feed direction so that the cutting blade 16 moves outward in the radial direction of the device wafer 11.

  That is, the cutting blade 16 cuts the laminated wafer 23 while relatively moving in the movement direction D1 shown in FIG. Thus, by cutting the cutting blade 16 while moving it radially outward of the device wafer 11, the laminated wafer 23 is processed into a truncated cone shape as shown in FIG. Note that the cutting depth of the cutting blade 16 is set such that at least the support wafer 21 is cut into the cutting blade 16.

  On the outer peripheral side surface of the laminated wafer 23, a diameter-increasing inclined portion 23a is formed so that the diameter of the laminated wafer 23 increases from the device wafer 11 side toward the support wafer 21 side. The diameter-increasing inclined portion 23a is gently inclined with respect to the back surface 11b of the device wafer 11, and is excellent in liquid material dischargeability.

  After performing the truncated cone forming step, a processing step of forming a resist film by spin coating on the back surface 11b which is the surface to be ground of the device wafer 11 is performed. FIG. 5 is a partial cross-sectional side view schematically showing processing steps. This processing step is performed by, for example, the spin coater 20 shown in FIG.

  The spin coater 20 includes a nozzle 24 that drops a chemical solution 22 such as a resist material onto the back surface 11 b of the device wafer 11. A spinner table 26 is disposed below the nozzle 24. The spinner table 26 is connected to a rotation mechanism (not shown) such as a motor, and rotates around a rotation axis C5 extending in the vertical direction.

  The surface of the spinner table 26 is a holding surface for sucking and holding the laminated wafer 23. A negative pressure of a suction source (not shown) acts on the holding surface through a flow path (not shown) formed inside the spinner table 26, and a suction force for sucking the laminated wafer 23 is generated.

  In the processing step, first, the back surface 21b side of the support wafer 21 is brought into contact with the holding surface of the spinner table 26, and the negative pressure of the suction source is applied. Thereby, the laminated wafer 23 is sucked and held by the spinner table 26.

  Next, a chemical solution 22 as a resist film material is dropped from the nozzle 24 to the vicinity of the center of the back surface 11b of the device wafer 11, and the spinner table 26 is rotated in a predetermined rotation direction R5. The chemical liquid 22 is diffused by the centrifugal force due to this rotation, and a thin resist film (not shown) is formed on the back surface 11 b of the device wafer 11. Note that after the resist application, a drying process or the like for drying the formed resist film may be performed.

  In the present embodiment, since the enlarged diameter inclined portion 23a that is gently inclined with respect to the back surface 11b is formed in the above-described truncated cone forming step, excess chemical liquid 22 is appropriately supplied through the enlarged diameter inclined portion 23a. Removed. That is, since the chemical liquid 22 does not easily accumulate on the outer peripheral edge of the device wafer 11, the formed resist film does not have to be thick at the outer peripheral edge.

  Thus, according to the laminated wafer processing method of the present embodiment, it is possible to prevent the resist film formed by spin coating from becoming thick at the outer peripheral edge of the device wafer 11.

  In addition, this invention is not limited to description of the said embodiment, A various change can be implemented. For example, in the above embodiment, the truncated cone forming step is performed after the thinning step is performed. However, the truncated cone forming step may be performed before the thinning step is performed. That is, you may implement in order of a truncated cone formation step, a thinning step, and a processing step.

  Moreover, in the said embodiment, although the resist film is formed in the process step, you may form insulating films other than a resist film. Further, the processing step may include a process such as a CMP process or a wet etching process. For example, the resist film can be formed after performing a CMP process or a wet etching process.

  In the above embodiment, the thinning step, the truncated cone forming step, and the processing step are performed by the grinding device 2, the cutting device 12, and the spin coater 20, respectively, but the present invention is not limited to this. For example, you may implement all the steps using the composite apparatus provided with the function of the grinding device 2, the cutting device 12, and the spin coater 20.

  In addition, the configurations, methods, and the like according to the above-described embodiments can be changed as appropriate without departing from the scope of the object of the present invention. For example, the laminated wafer processing method according to the present invention is useful also in a manufacturing process for manufacturing a BSI (Back Side Illumination) type CMOS image sensor.

11 Device wafer (first wafer)
11a Front surface 11b Back surface 11c Outer peripheral part 13 Device area 15 Peripheral surplus area 17 Street (division planned line)
19 Device 21 Support wafer (second wafer)
21a Front surface 21b Back surface 23 Laminated wafer 23a Diameter-increasing inclined part 2 Grinding device 4 Spindle 6 Wheel mount 8 Grinding wheel (grinding means)
8a Wheel base 8b Grinding wheel 10 Chuck table 12 Cutting device 14 Spindle 16 Cutting blade 18 Chuck table 20 Spin coater 22 Chemical liquid 24 Nozzle 26 Spinner table

Claims (1)

A method for processing a laminated wafer in which a first wafer is laminated on a second wafer,
A thinning step of holding the second wafer side of the laminated wafer and grinding the first wafer with a grinding means to a predetermined thickness;
After performing the thinning step, a processing step for processing the ground surface of the first wafer;
Before or after carrying out the thinning step, and before carrying out the processing step, a diameter-increasing inclined portion whose diameter increases from the first wafer toward the second wafer is formed on the outer peripheral side surface of the laminated wafer. A truncated cone forming step to form a truncated cone having
In the processing step, resist coating by spin coating is performed on the surface to be ground of the first wafer,
In the truncated cone forming step, the cutting blade is moved to the outer side in the radial direction of the first wafer while cutting the rotating blade on the outer peripheral portion of the first wafer, and the expansion is performed by rotating the laminated wafer. A method for processing a laminated wafer, comprising forming a diameter inclined portion.

Images