JP2011103379A - Flat processing method of wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat processing method of a wafer that can efficiently remove waviness of a surface of the wafer in a manufacturing step of the wafer for a semiconductor device. <P>SOLUTION: The wafer 1 which has flat curable materials 2A and 2B laminated on both surfaces respectively is formed, and subjected to both-side simultaneous grinding to remove the curable materials 2A and 2B and also to grind both surfaces of the wafer 1. During the both-side simultaneous grinding, pressing force of upper and lower grindstones 6 and 7 pressed against both surfaces of the wafer 1 is preferably 100 to 250 gf/cm<SP>2</SP>. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for grinding the surface of a wafer for semiconductor devices, and more particularly, a wafer employing double-sided simultaneous grinding to efficiently remove waviness and warpage (hereinafter collectively referred to as “waviness”) on the wafer surface. The present invention relates to a flattening method.

  Generally, a wafer such as silicon is used for a substrate of a semiconductor device. The silicon wafer is manufactured from a silicon single crystal ingot grown by the Czochralski method or the like. Usually, a single crystal ingot is processed into a cylindrical shape by grinding the outer periphery and sliced into a disk-shaped wafer using an inner peripheral saw or a wire saw. The sliced wafer is chamfered at the outer periphery and finished to a predetermined diameter, and the wafer surface is ground, the surface irregularities and parallelism are adjusted, and the wafer surface is subjected to mechanochemical polishing in the polishing process. One or both sides can be mirror finished.

  At that time, since the surface of the wafer sliced from the single crystal ingot is often undulated, the following problems arise.

  FIG. 1 is a schematic diagram for explaining the behavior of waviness on a wafer surface in a conventional grinding process. FIG. 1 (a) shows a state before grinding, and FIG. 1 (b) shows a state where a wafer is chucked during grinding. FIG. 4C shows a state during grinding, and FIG. 4D shows a state after grinding.

  As shown in FIG. 1A, when grinding a wafer 1 after slicing in which waviness is generated on the surface, the wafer 1 is placed on a turntable 10 as shown in FIG. The suction is performed by a suction mechanism (not shown). At this time, since the wafer 1 is thin, the wafer 1 is elastically deformed along the upper surface of the turntable 10 and is chucked in a state of being in close contact with the turntable 10.

  Next, as shown in FIG. 1C, the wafer 1 held on the turntable 10 is rotated around the central axis as the turntable 10 is rotated, and a diamond grindstone is attached as a grinding tool from above. The ground grinding head 11 is pressed while being rotationally driven, and one surface on the upper surface side is ground. When the suction to the wafer 1 is released after the grinding, the elastic deformation of the wafer 1 is released as shown in FIG. 1D, and the waviness is restored to the surface by the spring back. The other surface of the wafer 1 is ground in the same manner, and the waviness is restored and remains on the surface after the grinding.

  Thereafter, when a wafer having undulations remaining on the surface is polished, the wafer is sucked to the lower surface of the rotary head and is elastically deformed and held in the same manner as in the above grinding step. The wafer held by the rotary head is pressed against a polishing pad on a rotary table onto which polishing slurry is dropped, and the surface on the lower surface side is polished by mechanochemical polishing. When the suction to the wafer is released after polishing, the surface of the wafer is restored to the undulation due to the spring back that accompanies the release of the elastic deformation, as in the above-described grinding step. For this reason, waviness remains on the surface of the polished wafer.

  Thus, the undulation generated on the wafer surface due to slicing of the single crystal ingot remains on the wafer surface after grinding and also on the wafer surface after polishing. When waviness remains on the wafer surface after polishing, the flatness of the wafer surface is lowered, which hinders the subsequent semiconductor device manufacturing process.

  For this reason, in the wafer manufacturing process, a technique capable of removing the waviness on the wafer surface is strongly desired.

  For example, in Patent Documents 1 to 3, when a wafer sliced from a single crystal ingot is ground with a diamond grindstone, a curable material is applied in advance to only one surface of the wafer surface where waviness is generated. A technique is disclosed in which a wafer is placed on a rotary table so that the flat curable material surface comes into contact with the surface and held by suction to grind the wafer surface on which the curable material is not laminated. ing. In this technique, after grinding the wafer surface on which the curable material is not laminated, the wafer is further placed on the rotary table so that the ground wafer surface comes into contact and held by suction. It is assumed that the surface of an unground wafer on which is stacked is ground.

  According to the techniques disclosed in Patent Documents 1 to 3, the wafer is elastically deformed because the wafer is held on the rotary table by sucking the flat curable material surface and further the ground wafer surface. Even if the suction to the wafer is released after grinding, the occurrence of waviness on the wafer surface is suppressed.

Japanese Patent Laid-Open No. 11-111653 JP 2006-261527 A JP 2006-269761 A

  However, in the techniques disclosed in Patent Documents 1 to 3, in order to grind both surfaces of the wafer, first, the wafer surface on which the curable material is not laminated is ground, and then the curable material is laminated. It is necessary to go through a two-step grinding process of grinding the unground wafer surface. For this reason, waviness on the wafer surface cannot be efficiently removed, and the productivity of the wafer deteriorates.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a wafer flattening method that can efficiently remove waviness on the wafer surface in the manufacturing process of a wafer for semiconductor devices. And

  In order to achieve the above object, the present inventors have studied in detail the manufacturing process of a wafer for semiconductor devices. As a result, in order to efficiently remove waviness on the wafer surface, the wafer sliced from a single crystal ingot is ground. In this case, it has been found that it is effective to apply a curable material to the surface of the wafer where the undulation is applied and harden it flatly, and to apply a flattening process on both sides of the wafer at the same time, thereby completing the present invention. It was.

  The gist of the present invention resides in a wafer flattening method described below. That is, a method for flattening the surface of a wafer for semiconductor devices, in which a curable material is applied and cured only on one side of the wafer surface, and a flat curable material is laminated only on one side. A curable material laminating step to be formed, and a planarization step of performing double-side simultaneous grinding on the wafer formed through the curable material laminating step to remove the curable material and planarize both sides of the wafer. This is a method for planarizing a wafer.

Also, the wafer planarization method of the present invention is a method for planarizing the surface of a wafer for a semiconductor device, and a curable material is applied to both sides of the surface of the wafer and cured, so that both sides are flattened. Curable material laminating process to form a wafer laminated with various curable materials, and the wafer formed through this curable material laminating process is simultaneously ground on both sides to remove the curable material and flatten both sides of the wafer And a flattening process to be realized. In the case where a wafer having a curable material laminated on each side is to be ground, it is preferable that the pressing force of a grinding tool pressed on both sides of the wafer is 100 to 250 gf / cm ^{2 in the} planarization process.

  According to the planarization processing method of a wafer of the present invention, by performing double-sided simultaneous grinding on a wafer having a flat curable material laminated on the surface, the wafer does not undergo elastic deformation during grinding. The occurrence of the undulation is suppressed, and both surfaces of the wafer can be ground simultaneously in one process, so that the undulation on the wafer surface can be efficiently removed.

It is a schematic diagram explaining the behavior of the waviness of the wafer surface in the conventional grinding process. It is a schematic diagram which shows an example of the process of laminating | stacking a curable material only to the single side | surface of a wafer in the planarization processing method of the wafer of this invention. It is a schematic diagram which shows an example of the process which laminates | stacks a curable material on each both surfaces of a wafer in the planarization processing method of the wafer of this invention. It is a schematic diagram explaining the grinding process of the wafer by which the flat curable material was laminated | stacked in the planarization processing method of the wafer of this invention.

  Below, the embodiment is explained in full detail about the planarization processing method of the wafer of this invention. The wafer flattening method of the present invention is a method applied when grinding a wafer for a semiconductor device sliced from a single crystal ingot. The surface of the wafer is cured by applying a curable material to the surface. A curable material laminating process for forming a wafer on which a flat curable material is laminated, and the wafer formed through this curable material laminating process are simultaneously ground on both sides to remove the curable material and to remove both surfaces of the wafer. And a flattening process step for flattening. Here, the curable material may be configured to be laminated on only one side of the surface of the wafer, or may be configured to be laminated on both sides.

1. Curable Material Laminating Step FIG. 2 is a schematic view showing an example of a step of laminating a curable material only on one side of the wafer in the wafer flattening method of the present invention. When laminating the curable material only on one side of the wafer, the curable material 2A is applied to the upper surface of the glass surface plate 3 as shown in FIG. Subsequently, as shown in FIG. 2B, the wafer 1 on which the undulation is generated is placed on the curable material 2 </ b> A applied to the glass surface plate 3.

  The curable material is not particularly limited as long as it is fluid at the time of application and can be cured thereafter, and a thermosetting resin such as a phenol resin, a urea resin, or an epoxy resin can be employed. In addition, an ultraviolet curable resin that is cured by ultraviolet irradiation such as black light, wax, gypsum, or the like may be employed.

  After the curable material 2 </ b> A is cured, the curable material 2 </ b> A is peeled off from the glass surface plate 3 integrally with the wafer 1. Thereby, as shown in FIG.2 (c), the wafer 1 by which the flat curable material 2A was laminated | stacked only on one side is obtained. This wafer 1 is in a state in which undulations remain on the surface, and no elastic deformation has occurred.

  When the curable material 2A is peeled off from the glass surface plate 3 integrally with the wafer 1, it is assumed that the glass surface plate 3 and the curable material 2A are bonded to each other and peeling becomes difficult. In this case, the glass surface plate 3 is cooled or heated to cause a thermal shrinkage difference or a thermal expansion difference between the glass surface plate 3 and the curable material 2A, thereby curable material from the glass surface plate 3. 2A can be easily peeled off. It is also effective to perform a release treatment on the upper surface of the glass surface plate 3 in advance with a release agent such as Teflon (registered trademark) or silicon.

  FIG. 3 is a schematic diagram showing an example of a process of laminating a curable material on each side of the wafer in the wafer planarization method of the present invention. When laminating a curable material on each side of the wafer, the procedure shown in FIGS. 2 (a) to 2 (c) is repeated.

  That is, after forming the wafer 1 in which the flat curable material 2A is laminated on one side through the procedure shown in FIGS. 3A to 3C, the glass surface plate 3 is formed as shown in FIG. A curable material 2B is applied to the upper surface of the substrate. Subsequently, as shown in FIG. 3E, the wafer 1 is mounted on the curable material 2B applied to the glass surface plate 3 so that the exposed surface is contacted without the curable material 2A being laminated. Put.

  After the curable material 2B on the glass surface plate 3 is cured, the curable material 2B is peeled from the glass surface plate 3 integrally with the wafer 1 on which the curable material 2A is laminated. Thereby, as shown in FIG.3 (f), the wafer 1 by which flat curable material 2A, 2B was laminated | stacked on both surfaces is obtained. This wafer 1 is also in a state in which undulations remain on the surface, and no elastic deformation occurs.

  In FIGS. 2 and 3, a method of transferring a curable material applied on a glass surface plate to the wafer surface is used as a method of laminating a flat curable material on the wafer surface. A spin coating method in which a curable material is dropped on the wafer surface while rotating the substrate, a method of brushing the curable material on the wafer surface, or the like can also be employed.

2. Grinding Step A wafer having a flat curable material laminated on the surface through the curable material laminating step is subjected to double-sided simultaneous grinding using a double-side grinding apparatus. As the double-side grinding device, a lapping device, a double-head surface grinding device, or the like can be used. As a lapping device, for example, the carrier plate is engaged with the sun gear and the internal gear, the wafer is set in the holder of the carrier plate, both surfaces of the wafer are held between the upper surface plate and the lower surface plate, and the abrasive is used. In addition to supplying, the carrier plate is planetarily moved by the sun gear and the internal gear, and at the same time, the upper surface plate and the lower surface plate are rotated in the relative direction, whereby both surfaces of the wafer can be simultaneously wrapped.

  In addition, as a double-sided surface grinding apparatus, for example, the wafer is stored and held in a circular hole formed in a disk-shaped carrier thinner than the wafer, and the wafer held on the carrier is rotated and driven as a grinding tool from above and below. The wafer is sandwiched between a pair of grindstones (or a surface plate to which abrasive grains are fixed), and the upper and lower grindstones are pressed against both surfaces of the wafer, thereby simultaneously polishing both surfaces of the wafer. When performing grinding while holding the wafer with a carrier, if one carrier is used, the carrier can be configured to give a swivel motion in a horizontal plane. If a plurality of carriers are used side by side, the horizontal plane is used for each carrier. It is possible to adopt a configuration that imparts a motion like a planetary gear that revolves while rotating inside.

  FIG. 4 is a schematic diagram for explaining a grinding process of a wafer laminated with a flat curable material in the wafer planarizing method of the present invention. FIG. 4 (a) shows a state before grinding. (b) shows the state during grinding, and (b) shows the state after grinding. In the figure, the grinding state of a wafer in which a curable material is laminated on each side is illustrated.

  As shown in FIG. 4A, the wafer 1 in which the curable materials 2A and 2B are laminated on both surfaces is accommodated in a circular hole 5 formed in the carrier 4, and the lower surface side is supported by the lower grindstone 7. Is done. In the case of a wafer in which a curable material is laminated only on one side, either side may be directed to the lower grindstone 7.

  Next, as shown in FIG. 4B, the wafer 1 held by the carrier 4 is sandwiched between an upper grindstone 6 and a lower grindstone 7 lowered from above, and flat curable materials 2A, 2B. The upper and lower grindstones 6 and 7 that are rotationally driven are pressed against the surface of the steel. Thereby, since the pressing target of the upper and lower grindstones 6 and 7 is a flat surface of the curable materials 2A and 2B, the wafer 1 is further elastically deformed and is further rotated by the upper and lower grindstones 6 and 7 that are rotationally driven. Then, the curable materials 2A and 2B are gradually removed, and both surfaces are ground in advance with the wavy convex portions. During grinding, a motion in a horizontal plane is imparted to the carrier 4 by a mechanism (not shown), and the wafer 1 is swung in the horizontal plane accordingly.

  Since the wafer 1 subjected to the double-side simultaneous grinding in the grinding step does not undergo elastic deformation during grinding, the occurrence of surface waviness after grinding is suppressed as shown in FIG. In addition, since both surfaces of the wafer 1 can be ground simultaneously in one process, waviness on the wafer surface can be efficiently removed, and as a result, the productivity of the wafer can be improved.

In the above grinding process, when a wafer having a curable material laminated on each side is to be ground, the upper and lower grindstones to be pressed against both sides of the wafer, that is, the pressing force of the grinding tool is set to 100 to 250 gf / cm ² . Is preferred. Since the pressing force of the grinding tool corresponds to the grinding rate, by setting the pressing force of the grinding tool to 100 to 250 gf / cm ² as shown in the examples described later, sufficient waviness of the wafer surface can be achieved in a short time. Grinding that can be removed easily. When a wafer with a curable material laminated on only one surface is to be ground, if the pressing force of the grinding tool is too high, the swell of the wafer surface cannot be removed, so the pressing force is 100 to 150 gf / cm. ² is preferable.

  In order to confirm the effect of the wafer flattening method of the present invention, the following tests were conducted. As a test wafer, a single crystal ingot was sliced with a wire saw, and a wafer with a chamfered outer periphery was used. A flat curable material was laminated only on one side of the wafer, and flat on each side of the wafer. A plurality of laminated curable materials were prepared. At this time, a phenol resin-based thermosetting resin was employed as the curable material, and a wafer was formed by laminating a curable material having a thickness of 20 μm by the method shown in FIGS. For comparison, a plurality of wafers in which a curable material was not laminated on both sides were also prepared.

  By changing the pressing force of the upper and lower grindstones variously by the method shown in FIG. 4, each wafer was subjected to double-sided simultaneous grinding, and then the surface of each wafer was confirmed with a magic mirror to evaluate the remaining state of undulation. The evaluation is good when the undulation is completely removed, good when most of the undulation is removed and the undulation remains on a part of the wafer surface, and not when the undulation remains on the entire surface of the wafer. It was. The results are shown in Table 1.

As shown in the table, it became clear that when the curable material was laminated on the wafer surface, the surface waviness could be removed by double-sided simultaneous grinding. In particular, in a wafer in which curable materials are laminated on both sides, waviness can be completely removed even if the pressing force of the grindstone is increased, so that the grinding rate can be increased and the grinding time can be increased. Shortening can be expected. In addition, in the wafer in which the curable material is laminated only on one side, when the pressing force of the grindstone exceeds 150 gf / cm ² , the undulation is insufficiently removed. It is considered that the wafer is elastically deformed during grinding as the pressing force increases due to the exposure without being laminated.

  On the other hand, when the curable material was not laminated on either side of the wafer, the surface waviness could not be removed even if both sides were ground simultaneously. This is considered to be due to the fact that the grindstone is pressed directly on both sides of the wafer during grinding, so that the wafer is significantly elastically deformed, and waviness is restored to the surface by springback after grinding.

  According to the planarization processing method of a wafer of the present invention, by performing double-sided simultaneous grinding on a wafer having a flat curable material laminated on the surface, the wafer does not undergo elastic deformation during grinding. The occurrence of the undulation is suppressed, and both surfaces of the wafer can be ground simultaneously in one process, so that the undulation on the wafer surface can be efficiently removed. Therefore, the wafer flattening method of the present invention is extremely useful in that the productivity of the wafer can be improved.

1: wafer, 2A, 2B: curable material, 3: glass surface plate,
4: Carrier, 5: Circular hole, 6: Upper grindstone, 7: Lower grindstone

Claims (3)

A method for planarizing a surface of a wafer for a semiconductor device,
A curable material laminating step in which a curable material is applied and cured only on one side of the surface of the wafer to form a wafer in which a flat curable material is laminated only on one side;
The wafer formed through the curable material laminating process is subjected to double-sided simultaneous grinding to remove the curable material and to planarize both sides of the wafer. Processing method. A method for planarizing a surface of a wafer for a semiconductor device,
A curable material laminating step for forming a wafer in which a curable material is applied and cured on each side of the wafer surface, and a flat curable material is laminated on each side,
The wafer formed through the curable material laminating process is subjected to double-sided simultaneous grinding to remove the curable material and to planarize both sides of the wafer. Processing method. 3. The wafer planarization method according to claim 2, wherein in the planarization process, a pressing force of a grinding tool that is pressed against both surfaces of the wafer is 100 to 250 gf / cm ² .

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