JP2010182839A - Edge beveling method for multilayer wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an edge beveling method for a multilayer wafer that facilitates alignment of the multilayer wafer when the multilayer wafer is carried to a processing stage for a postprocessing stage. <P>SOLUTION: A cup wheel type grindstone 12 which tilts at 3 to 10° to the center of the multilayer wafer mounted on a support chuck which is rotating, is fixed in a freely rotatable manner. A grindstone shaft 13 is moved to grind an upper surface, shorter than a maximum diameter, of a lower-layer wafer w<SB>1</SB>constituting the multilayer wafer to a length of 0.1 to 3 mm and to a depth ranging from 5 mm to a depth which does not reach a maximum diameter part of the lower-layer wafer, and to bevel an edge part of an upper-layer wafer w<SB>2</SB>of the multilayer wafer with a cut wheel type grindstone edge 12a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a processing method for chamfering an edge surface of a laminated wafer (SOI wafer, TSV wafer) obtained by laminating two semiconductor wafers using a cup wheel type grindstone.

As a method for manufacturing an SOI wafer, (A) a step of forming a laminated body by superposing a semiconductor wafer and a support wafer via an oxide film, and (B) by thinning the semiconductor wafer to a predetermined thickness In a method for manufacturing a bonded SOI wafer, including a step of forming a thin single-crystal silicon layer on a supporting wafer via a buried oxide film layer, (C) overlapping between the step (A) and the step (B) The oxide film formed on the peripheral edge and chamfered portion of the main surface on the mating side is removed to leave the oxide film only on the overlapping surface excluding the peripheral edge. A method characterized by encapsulating with a main surface and a single crystal silicon layer has been proposed (see, for example, Patent Document 1).

In addition, an element substrate (wafer) having a diameter of 150 mm and a support substrate are prepared, wet oxidation is performed on the element substrate, an oxide film having a thickness of 1 μm is formed, and the polishing surface side of the element substrate on which the oxide film is formed; The polished surface of the supporting substrate was superposed and adhered, and the adhered bonded substrate was subjected to heat treatment at a high temperature of 1000 ° C. to enhance the bonding force of the superimposed surfaces. Thereafter, the diameter is reduced to 125 mm, and after removing the oxide film formed during the heat treatment by hydrofluoric acid treatment, the surface is ground and subjected to primary polishing, and 2 mm from the end surface portion (outermost peripheral portion) of the bonded substrate. After generating a peripheral sag in the outer peripheral part of the range (region), the diameter is reduced to 100 mm again by chamfering, and finally, secondary polishing and finish polishing are performed to create an SOI wafer. This is also known (see, for example, Patent Document 2).

Furthermore, a method of polishing an edge portion of a laminated (SOI) wafer using an abrasive tape has also been proposed (see, for example, Patent Document 3).

On the other hand, two cylindrical polishing drums with a polishing work surface on the outer periphery are arranged at a distance smaller than the diameter of a single-layer semiconductor substrate, and these polishing drums can be tilted while rotating at a required speed. There has also been proposed a method in which a chamfered edge of a semiconductor substrate held by a semiconductor substrate holding means is pressed against both polishing drums at the same time to mirror-polish the edge at two different points (for example, Patent Document 4). reference).

Further, a chamfering means having a chamfering grindstone capable of chamfering the peripheral edge of the wafer held by the wafer holding member formed to have a diameter smaller than the diameter of the wafer is used, and the end face and the edge inclined surface of the wafer are formed by the chamfering means. An apparatus for chamfering is also known (for example, see Patent Document 5).

Furthermore, a cup wheel type grindstone for grinding a silicon substrate surface of a wafer is also known (for example, see Patent Document 6).

Edge polishing of SOI wafers with diameters of 300-450 mm is demanded as the next generation semiconductor substrate with a diameter of semiconductor substrates (wafers) expanding from 150-200 mm to 300-450 mm and thickness of 20-100 μm is required. Alternatively, flat processing obtained by chamfering the edge surface of the SOI wafer using the edge chamfering grinding wheel or polishing tape described in Patent Document 1 to Patent Document 5 for grinding, and then performing back surface grinding and back surface polishing of the SOI wafer. It has been found that many chippings and cracks can be seen at the edge of the SOI wafer.

Further, in an SOI wafer in which the end surface of the SOI wafer is chamfered vertically or obliquely using the tiltable chamfering grindstone described in Patent Document 5, the wafer core in the back grinding process, the polishing process, or the wafer peeling process in the post-processing process It is difficult to perform the alignment, and a SOI wafer substrate processing manufacturer has requested that a part of the edge surface be left so that the lower wafer on the stacked wafer can be centered.

JP 2005-79109 A JP 2006-100406 A US Pat. No. 6,641,464 US Pat. No. 6,159,081 JP-A-11-48109 JP 2000-94342 A

The present invention provides a chamfered edge portion of a laminated wafer that does not cause cracks or chipping in the laminated wafer obtained by back-grinding or polishing, and enables centering when transferring the laminated wafer to these subsequent processes. A grinding method is provided.

In the present invention, a grindstone shaft for rotatably fixing a cup wheel type grindstone is rotatable, and can be moved back and forth in the direction of the center point of a laminated wafer placed on a support chuck, and provided in a column so as to be able to move up and down. In the method of chamfering the edge portion of the laminated wafer supported by the rotating support chuck using the chamfering device, first, the inclination angle of the cutting edge of the cup wheel type grindstone is 3 to 10 with respect to the vertical axis of the surface of the laminated wafer. The grindstone shaft is rotated to adjust the grindstone shaft position, and then the grindstone shaft is moved forward to the center point of the laminated wafer placed on the support chuck while rotating the grindstone shaft. If the upper surface shorter than the diameter of the lower wafer is ground with a cutting edge of a rotating grinding wheel to a length of 0.1 to 3 mm, a depth of 5 mm to a depth not reaching the maximum diameter of the lower wafer After chamfering the edge of the upper wafer of the laminated wafer, the rotating grindstone shaft is retracted to a position where the cutting edge of the cup wheel grindstone does not contact the laminated wafer. A method of chamfering and grinding a wafer edge portion is provided.

The chamfering grinding method of the edge portion of the laminated wafer of the present invention can be chamfered so that the maximum diameter portion of the lower wafer of the laminated wafer remains so that the laminated wafer can be centered in the subsequent process, and the upper stage. Since the end of the wafer is chamfered with an inclination of 3 to 10 degrees with respect to the wafer plane, chipping and cracking do not occur in the laminated wafer in the back surface grinding, back surface polishing, and transporting steps in the subsequent steps.

FIG. 1 is a side view of a chamfering device for an edge portion of a laminated wafer. FIG. 2 is an explanatory view showing an execution procedure of the chamfering process of the edge portion of the laminated wafer.

A chamfering apparatus 1 shown in FIG. 1 includes a chamfering tool stage 10, a support chuck 20, and a grindstone dresser 30. The chamfering tool stage 10 raises a column 12 on the upper surface of a tool table 11 composed of a guide way 11a and a slide way 11b provided on a frame 40, and a grindstone shaft lifting device 50 is suspended from the upper front of the column. A grinding wheel shaft fixing swivel device 60 is provided on the side surface of the grinding wheel shaft mounting plate 55 of the grinding wheel shaft lifting device, and the fixed base 15 of the grinding wheel head 14 with the cup wheel type grinding wheel 12 fixed to the grinding wheel shaft 13 is mounted on the grinding wheel shaft fixing swivel. The device 60 is swingably mounted around the pin 19. The grindstone shaft 13 is rotated by a built-in motor.

The tool table 11 is slidable on the guide way 11 a and slides on the center point o of the laminated wafer placed on the support chuck 20. The ball screw 21d receives the rotational drive of the servo motor 21c, and the slide way 11b is moved forward to the center point position side of the laminated wafer placed on the support chuck 20, or retracted from the center point position of the laminated wafer. The forward / backward movement of the slide way 11b may be linear actuator drive or linear motor drive.

The grindstone shaft raising / lowering device 50 receives the rotational drive of the servo motor 52 by the ball screw 51 and raises / lowers the grindstone shaft mounting plate 54 in the vertical direction via the threaded body 54. The screw 54 slides on the guide rail 53. The up and down movement of the grindstone shaft mounting plate 55 may be driven by a linear actuator or a linear motor.

The fixed base 15 incorporating the built-in motor is fixed to a fan-shaped mounting plate 63 that constitutes the wheel shaft fixing swivel device 60, and this fan-shaped mounting plate 63 is mounted on the wheel shaft of the wheel shaft lifting device via a pin 19 indicated by a broken line. It is supported on the side of the plate 55 so as to be able to turn (swing). A rack 64 is engraved on the arc-shaped outer peripheral surface of the fan-shaped mounting plate 63, and a pinion 66 of the motor 65 fixed to the side surface of the grindstone shaft mounting plate 55 is engaged. Therefore, when the pinion 66 is rotated by the rotation of the motor shaft of the motor 65, the fan-shaped mounting plate 63 is turned around the pin 19 and the inclination angle of the grindstone shaft can be adjusted. The inclination angle (θ) of the grindstone axis is determined by the desired deletion width 0.2 to 3 mm in the diameter direction of the laminated wafer w and the edge inclination angle 80 to 87 degrees of the laminated wafer. The blade edge 12a is turned so that the inclination angle (θ) of the blade edge 12a is 3 to 10 degrees with respect to the vertical axis of the surface of the laminated wafer.

The cup wheel-type grindstone 12 is, for example, the cup wheel-type grindstone described in Patent Document 6, and the bottom wall of the peripheral wall of the cup-shaped base metal provided with an annular peripheral wall and a bottom wall provided at one end thereof. A cup wheel type grindstone 12 in which an arcuate grindstone cutting edge 12a is fixed in an annular shape on the upper surface of the opposite surface, wherein the base metal is supplied to the outer surface of the bottom wall and an annular groove concentric with the peripheral wall. In order to introduce the grinding fluid to the inside of the peripheral wall, it is provided through the bottom wall from the bottom surface of the annular groove, is inclined to the outer peripheral side to the other end side of the peripheral wall, and is concentric with the peripheral wall An annular grindstone that has a large number of grinding fluid introduction holes provided at equal intervals and is fixed to the upper surface of the peripheral wall opposite to the bottom wall is shared by the peripheral wall and the annular groove at a portion protruding from the top surface of the peripheral wall. The shaft center side with respect to the shaft and the rising surface of the annular grindstone orthogonal to the shaft center A large number of grinding liquid discharge slits inclined at 30 to 60 degrees toward the outer side of the grindstone are provided at equal intervals, the slit height is 3 to 10 mm, the grindstone width is 2 to 7 mm, and the annular grindstone blade is divided by the slits. Is a cup wheel type grindstone having a length of 10 to 50 mm. The diameter of the grindstone blades 12a arranged in a ring shape of the cup wheel grindstone 12 is preferably 0.5 to 1.5 times the diameter of the laminated wafer. The grindstone blade 12a is preferably a diamond vitrified bond grindstone blade or a diamond resin bond grindstone blade having a grinding number of 3,000 to 8,000 when the wafer substrate is a silicon substrate.

The cup wheel type grindstone 12 can use a commercially available cup wheel type grindstone in addition to the grinding liquid center supply type cup wheel grindstone described in Patent Document 6.

The support chuck 20 is preferably a vacuum chuck in which a porous ceramic chuck table 21 is rotatably supported by a hollow shaft 22, and the diameter of the porous ceramic chuck table 21 is 0.5 to 3 mm smaller than the diameter of the laminated wafer. preferable. A decompression pipe, a pure water supply pipe, and a compressed air supply pipe are provided in the hollow shaft 22 pipe.

  The grindstone dresser 30 is installed at a position where the grindstone shaft 13 retracts from the support chuck 20 side, and is used to mold the grindstone edge 12a of the cup wheel grindstone before, during or after edge chamfering of the laminated wafer. Is done.

As shown in FIG. 2, the edge chamfering of the laminated wafer w is first performed so that the inclination angle (θ) of the cutting edge 12a of the cup wheel type grindstone 12 is 3 to 10 degrees with respect to the vertical axis of the surface of the laminated wafer w. The axis of the grindstone is adjusted by turning the axis (see FIG. 2a), and then the grindstone axis is advanced in the direction of the center point o of the laminated wafer w placed on the support chuck 20 while rotating the grindstone axis 13. length 0.1~3mm at the cutting edge 12a of the rotating grinding wheel the upper surface of the shorter diameter portion than the lower wafer w ₁ diameter constituting the laminated wafer w, ground to a depth that does not lead to a depth of 5mm to lower wafer w ₁ maximum diameter section after lamination I wafer went upper of the wafer w ₂ chamfering of the edge portion (see FIG. 2b), the rotation to which the wheel spindle 13 to the cutting edge 12a of the cup wheel type grinding wheel laminate I Parkway that while Retracted made to a position not in contact with the w, stops the rotation of the grinding wheel shaft 13 (see FIG. 2c).

The edge chamfering time of the 300 mm diameter laminated wafer is about 5 to 20 seconds, although it depends on whether the material of the laminated wafer base is silicon, sapphire, or glass. The rotational speed of the hollow shaft 22 that supports the porous ceramic chuck table 21 is 50 to 150 rpm, and the rotational speed of the grindstone shaft 13 is 2,000 to 3,000 rpm.

A chamfering apparatus 1 shown in FIG. 1 is used as an object to be ground by using an SOI wafer w in which two printed wiring surfaces of a semiconductor wafer in which an electronic circuit is printed and wired on the surface of a silicon substrate having a diameter of 300 mm and a thickness of 750 μm. The laminated wafer was chamfered.

First, the grindstone shaft 13 is swiveled by the swivel device 60 so that the inclination angle (θ) of the cutting edge 12a of the diamond vitrified cup wheel type grindstone 12 having a grinding number of 3,000 is 5 degrees with respect to the vertical axis of the surface of the laminated wafer w. The position of the grinding wheel shaft was adjusted.

Next, the grindstone shaft 13 rotating at 2,000 rpm is advanced in the direction of the center point o of the laminated wafer w placed on the porous ceramic chuck table 21 of the support chuck 20 that rotates at 120 rpm to form the laminated wafer w. Lower wafer w ₁ The upper surface of the diameter portion shorter than 300 mm is ground with a cutting edge 12a of a rotating grinding wheel at a length of 1.5 mm and a depth of 200 μm, and the edge portion of the upper wafer w ₂ of the laminated I wafer is chamfered ( Then, the rotating grindstone shaft 13 was retracted to a standby position where the cutting edge 12a of the cup wheel grindstone would not contact the laminated I wafer w, and the rotation of the grindstone shaft 13 was stopped.

After the rotation of the porous ceramic chuck table 21 of the support chuck 20 is stopped, the surface of the laminated wafer w is blown with pressurized water and brush-washed, and then pressurized water is supplied to the lower surface of the porous ceramic chuck table 21 to thereby porous the laminated wafer w. Peeling from the ceramic chuck table 21 was facilitated.

Using a semiconductor substrate planarization apparatus GDM300II (trade name, manufactured by Okamoto Machine Tool Co., Ltd.) described in Japanese Patent Application No. 2008-183398, an edge chamfered laminated wafer on the support chuck 20 is articulated. Adsorbed to the robot's suction pad and transferred to the back grinding stage.

Rough grinding of the silicon substrate surface of the laminated wafer using a rough grinding cup wheel type diamond resin bond grinding wheel with grinding number 600 on the coarse grinding stage (substrate rotation speed is 300 rpm, grinding wheel axis rotation speed is 1,800 rpm) Then, the silicon substrate surface was scraped 670 μm.

The silicon substrate surface of the roughly ground semiconductor substrate is subjected to finish grinding on the finish grinding stage using a cup wheel type diamond vitrified bond grindstone with an abrasive number of 8,000. Was rotated at 300 rpm and the grinding wheel shaft was rotated at 1,800 rpm), the silicon substrate surface was scraped by 30 μm, and the thickness of the silicon substrate was reduced to 20 μm. Next, brush cleaning was performed while supplying pure water to the ground silicon substrate surface, and then dried by blowing dry air. Grinding marks were observed on the obtained silicon substrate surface.

After the ground semiconductor substrate is transferred to the polishing stage, the silica-based particle-dispersed aqueous abrasive slurry “SR300” (trade name) of ヅ Pon Air Products Co., Ltd. is 100 cc / min on the ground silicon substrate surface. A buff polishing process is performed for 6 minutes to remove grinding streaks by rubbing at a polishing pad pressure of 230 g / cm ² , a polishing pad rotation speed of 250 rpm, and a semiconductor substrate rotation speed of 150 rpm while supplying a quantity. went. The thickness of the silicon substrate surface was reduced by 3 μm.

The pressure of the polishing pad over the silicon substrate surface is 50 g / cm ² while supplying 300 cc / min of silica-based particle-dispersed aqueous slurry “SR300” (trade name) to the buffed silicon substrate surface. A second buffing process was performed for 4 minutes, in which the pad was rubbed at a rotation speed of 20 rpm and the rotation speed of the semiconductor substrate was 20 rpm. The thickness of the silicon substrate surface was further reduced by 0.1 μm. The number of particles adhering to the silicon substrate surface was 5,043 particles having a diameter of 0.2 μm or less, and 204 particles having a diameter of 1.0 μm or more.

Thereafter, this grinding and buffing silicon base surface was subjected to alkali cleaning for 2 minutes to supply the chemical SC1 in an amount of 500 cc / min, and then acid cleaning with hydrofluoric acid-containing ozone water for 1 minute. Wash the silicon substrate surface with water, spin dry, and apply a silicon substrate mirror surface with 2 particles of foreign particles (grinding debris and polishing debris) with a diameter of 0.2 μm or less and surface average roughness (Ra) of 0.002 μm. A laminated wafer having the above was obtained. No chipping or cracking was found on the laminated wafer.

In the same way as in Example 1, 25 edge chamfering, back grinding, back polishing, and cleaning were performed on 24 laminated wafers. No chipping or cracking was observed on 24 laminated wafers, only 1 Only one chip with a length of about 3 mm was found from the edge of the mirror silicon substrate of the laminated wafer.

In the post-processing step, the edge chamfering of the laminated wafer can be performed without causing cracking or chipping in the laminated wafer. Since the edge chamfered laminated wafer retains the maximum diameter portion of the lower wafer, it is easy to center the laminated wafer when the laminated wafer is transferred to a processing stage in a post-processing step.

DESCRIPTION OF SYMBOLS 1 Chamfering device 10 Chamfering tool stage 11 Tool table 12 Cup wheel type grindstone 13 Grinding wheel shaft 20 Support chuck 30 Grinding wheel dresser 50 Grinding wheel shaft lifting device 60 Grinding wheel shaft fixed swivel device w Laminated wafer

Claims (1)

Uses a chamfering device provided on the column so that the grindstone shaft that rotatably fixes the cup wheel grindstone can rotate, can move back and forth in the direction of the center point of the laminated wafer placed on the support chuck, and can be raised and lowered In the method of chamfering the edge portion of the laminated wafer supported by the rotating support chuck, first, the inclination angle of the cutting edge of the cup wheel type grindstone is 3 to 10 degrees with respect to the vertical axis of the surface of the laminated wafer. The wheel axis position is adjusted by turning the wheel axis, and then the lower wafer diameter constituting the laminated wafer by advancing the wheel axis in the direction of the center point of the laminated wafer placed on the support chuck while rotating the grinding wheel axis. The shorter upper surface is ground with a cutting edge of a rotating grinding wheel to a length of 0.1 to 3 mm, a depth of 5 mm to a depth that does not reach the maximum diameter of the lower wafer and is laminated. After chamfering the edge portion of the upper wafer of the wafer, the rotating grinding wheel shaft is retracted to a position where the cutting edge of the cup wheel type grinding wheel is not in contact with the laminated wafer. Chamfering grinding method.

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