JP2011249652A - Planarization method of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To planarize a wafer obtained by slicing an ingot, by removing warpage caused by distortion of the wafer and swells occurring in the surface layer on both sides of the wafer.SOLUTION: In a primary grinding process (ST11), both sides (first side, second side) of a wafer obtained by slicing an ingot are ground in order to remove processing strain thus reducing warpage caused by difference in the magnitude of processing strain. In a resin coating process, a swelling shape reset process and a resin curing process (ST12-ST14), surface layer on both sides of the wafer is shaped and cured by UV-curing resin in a state where the shape of swells in the surface layer on both sides of the wafer is maintained. In the first side, second side swell removing process (ST15, ST17), swells occurring in the surface layer of the wafer cured by the UV-curing resin are removed.

Description

  The present invention relates to a wafer flattening method, and more particularly to a flattening method for flattening the surface of a wafer obtained by cutting out from an ingot.

  2. Description of the Related Art Conventionally, semiconductor wafers such as silicon, SiC, GaAs, and sapphire are cut out as a sliced wafer (hereinafter simply referred to as “wafer”) from a cylindrical ingot by a cutting device such as a blade saw or a wire saw in a manufacturing process. . Thereafter, both surfaces of the wafer are flattened by a grinding device such as a double-head grinding device, a lapping device, a polishing device, or a polishing device. A plurality of devices are formed on the front surface, formed to a predetermined thickness by grinding the back surface, and divided into individual devices by a dicing apparatus or the like.

  However, a wafer cut out from an ingot has a size of distortion (processing distortion) generated on one surface (front surface) and two surfaces (back surface) due to cutting operation such as a blade saw or a wire saw. It has warpage due to the difference and undulation generated in the surface layer of one surface and two surfaces. When such warpage and waviness are ground with a lapping apparatus, fine irregularities can be removed, but it is difficult to completely remove the warpage and waviness.

  In order to cope with the problems of warping and waviness, the present applicant applies a resin coating process in which an ultraviolet curable resin is applied to two surfaces of a wafer, and an ultraviolet curable resin is applied instead of a wrapping process by a wrapping apparatus. A wafer holding step of holding the wafer so that one surface of the wafer is exposed on a holding surface of a stage having a substantially horizontal holding surface, and the wafer held on the holding surface of the stage is By a resin coating method comprising at least a pressing step of pressing in the stage direction from the surface side and a resin curing step of irradiating the ultraviolet curable resin with ultraviolet rays and curing the ultraviolet curable resin by separating the pressing means from the wafer. Proposes a method of grinding one surface flatly until the wafer is fixed with UV curable resin and the warpage and waviness are removed And it is (for example, see Patent Document 1). According to this method, since one surface of the wafer is ground flat while the shape of the warp and waviness of the wafer is maintained by the ultraviolet curable resin, the warp and waviness can be satisfactorily removed.

JP 2009-148866 A

  However, when warping due to non-equivalent (different size) distortion generated in the vicinity of the surface of the first surface and the second surface due to the cutting of the wafer is severe, the shape of warpage and waviness is caused by the ultraviolet curable resin. There is a problem that warping and waviness cannot be sufficiently removed even by a method of performing grinding while maintaining the above.

  The present invention has been made in view of such a situation, and effectively removes the warpage caused by the distortion of the wafer obtained by cutting out from the ingot and the undulation generated on the surface layers of both surfaces of the wafer, thereby flattening. An object of the present invention is to provide a method for flattening a wafer.

  The wafer flat processing method according to the present invention includes a warpage caused by a difference in magnitude of distortion generated on one surface of a wafer obtained by cutting from an ingot and two surfaces opposite to the one surface. A flat processing method for processing both surfaces of the wafer having the undulation generated on the surface of the one surface and the second surface by cutting, wherein the one surface of the wafer is a horizontal holding surface of a chuck table. The second surface of the wafer is ground until the distortion of the second surface of the wafer that is exposed in a state where the undulation is corrected and leveled by suction is removed. Grinding until the distortion of the one surface of the wafer exposed in a state where the waviness is corrected and leveled by suction holding on the holding surface is removed, and the one surface and A grinding process for forming an equivalent grinding distortion on the surface of the film and a UV curable resin was dropped on a film placed on a stage having a horizontal holding surface, and the grinding process was completed on the UV curable resin. The second surface of the wafer is placed, and the entire surface of the second surface of the wafer is coated with the ultraviolet curable resin by applying a uniform pressing force from the exposed surface to the stage. A resin coating step, and after applying the ultraviolet curable resin, release the pressing force in the direction of the stage from the one surface side, and return the waviness shape returning step to return the waviness shape of the wafer; and the waviness After the shape restoration step, the ultraviolet curing resin is irradiated with ultraviolet rays to cure the resin, and after the resin curing step, the waviness on the surface layer of the one surface is removed. A first surface waviness removing step for grinding, and a second surface waviness removing step for grinding until the waviness on the surface layer of the second surface is removed, with the first surface flattened by removing the waviness as a reference surface; It is characterized by comprising.

  According to the above-described method for flattening a wafer, one surface and two surfaces of a wafer obtained by cutting out from an ingot are ground (primary grinding) to equalize the distortion on both surfaces of the wafer and reduce warpage. After that, the shape of the undulation generated on the surface layer of the first surface and the second surface is maintained with an ultraviolet curable resin, and grinding (secondary grinding) is performed until the undulation is removed. Since the warpage due to the distortion of the wafer and the waviness of the surface layer on both surfaces of the wafer can be effectively removed, a wafer with high flatness can be obtained.

  According to the present invention, it is possible to effectively remove the warpage caused by the distortion of the wafer when cutting out from the ingot and the waviness of the surface layer on both surfaces of the wafer, so that a wafer with high flatness can be obtained.

In the wafer flat processing method which concerns on one embodiment of this invention, it is a schematic diagram of the wafer used as a process target. It is a figure for demonstrating the schematic process of the flat processing method of the wafer which concerns on the said embodiment. It is an external appearance perspective view which shows an example of the grinding device utilized for the primary grinding process of the flat processing method of the wafer which concerns on the said embodiment. It is a schematic diagram for demonstrating the state of the wafer in a primary grinding process. It is a schematic diagram for demonstrating the state of the wafer after grinding by the primary grinding process. It is an external appearance perspective view which shows an example of the resin coating apparatus utilized for the resin application | coating process etc. of the flat processing method of the wafer which concerns on the said embodiment. It is a schematic diagram which shows the principal part of the resin coating apparatus shown in FIG. It is a schematic diagram for demonstrating the state of the wafer in a resin application | coating process. It is a schematic diagram for demonstrating the state of the wafer in a resin application | coating process. It is a schematic diagram for demonstrating the state of the wafer in a wavy shape return process. It is a schematic diagram for demonstrating the state of the wafer in a resin hardening process. It is a schematic diagram for demonstrating the state of the wafer in the one surface waviness removal process. It is a schematic diagram for demonstrating the state of the wafer in a resin peeling process. It is a schematic diagram for demonstrating the state of the wafer in a 2nd surface waviness removal process.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, before describing the wafer flat processing method according to the present embodiment, the configuration of a wafer to be processed will be described. FIG. 1 is a schematic diagram of a wafer to be processed in the wafer flat processing method according to the present embodiment. In the wafer flat processing method according to the present embodiment, a wafer (as-sliced wafer) cut from an ingot by a cutting device such as a wire saw is used as a processing target.

  As shown in FIG. 1, the wafer 1 to be processed has two surfaces constituting the upper surface shown in FIG. 1 and the lower surface shown in FIG. Strain (fracture layer) (hereinafter referred to as “processing strain” as appropriate) 11a, 12a and undulations (fine irregularities on the surface layer) 11b, 12b formed on the surface of the first surface 11 and the second surface 12 are formed on the surface 12. Has been. The processing strains 11a and 12a formed on the first surface 11 and the second surface 12 are generally different in size, and the wafer 1 has a difference in the size of these processing strains 11a and 12a. As a result, warpage occurs. When the processing strain 11a formed on the first surface 11 is larger than the processing strain 12a formed on the second surface 12, as shown in FIG. 1, the warping is performed so that the first surface 11 side has a convex shape. Will occur. For example, in the wafer 1, undulations 11a and 12a of about 0.1 to 1 [mu] m indicated by L1 are formed, and warpage of about 10 to 20 [mu] m shown by L2 occurs.

  In the flat processing method of the wafer 1 according to the present embodiment, a primary grinding step (ST11) using a grinding device and a resin coating device are used for such a wafer 1 as shown in FIG. Resin application step (ST12), waviness shape return step (ST13) and resin curing step (ST14), one surface waviness removal step (ST15) using a grinding apparatus, and resin peeling step carried out from the grinding apparatus (ST16) and the second surface waviness removing step (ST17) using a grinding apparatus are performed, thereby causing warpage due to processing distortions 11a and 12a of the wafer 1 and surface waviness 11b on both surfaces of the wafer 1. , 12b are effectively removed to obtain a wafer 1 with high flatness. FIG. 2 is a view for explaining a schematic process of the flat processing method of the wafer 1 according to the present embodiment. Hereinafter, each process in the flat processing method of the wafer 1 which concerns on this Embodiment is demonstrated.

  FIG. 3 is an external perspective view showing an example of a grinding apparatus 100 used in the primary grinding process of the flattening method of the wafer 1 according to the present embodiment. In the following, for convenience of explanation, the lower left side shown in FIG. 3 is called the front side of the grinding apparatus 100, and the upper right side shown in FIG. 3 is called the rear side of the grinding apparatus 100. In the following, for convenience of explanation, the vertical direction shown in FIG. 3 is referred to as the vertical direction of the grinding apparatus 100.

  As shown in FIG. 3, the grinding apparatus 100 has a base 101 having a generally rectangular parallelepiped shape. On the front side of the upper surface of the base 101, an operation panel 102 that receives instructions for the grinding apparatus 100 is provided. On the rear side of the operation panel 102, a table support base 103 that supports the chuck table 103a is provided. A column portion 104 is provided on the rear side of the table support base 103. A grinding unit 105 is supported on the front surface of the support column 104 so as to be movable in the vertical direction.

  With such a configuration, the grinding apparatus 100 is configured to process the wafer 1 by relatively rotating the grinding unit 105 and the chuck table 103 a holding the wafer 1.

  The table support base 103 is provided in a square shape and rotatably supports the chuck table 103a. The table support base 103 is connected to a drive mechanism (not shown), and is slid in the front-rear direction within an opening 101 a formed on the upper surface of the base 101 by a drive force supplied from the drive mechanism. As a result, the chuck table 103a is separated from the grinding position where the wafer 1 faces the grinding unit 105 and the front side from the grinding position, and the unprocessed wafer 1 is supplied, while the processed wafer 1 is recovered. It is slid to and from the repositioning position.

  Before and after the table support table 103, a dustproof cover 106 is provided to prevent intrusion of grinding scraps and the like generated during grinding of the wafer 1 into the base 101. The dust cover 106 is attached to the front surface and the rear surface of the table support base 103 and is provided so as to be expandable and contractable according to the movement position thereof, and is configured to cover the opening 101 a of the base 101.

  The chuck table 103a is formed in a disk shape, and a holding surface 103b is formed as a horizontal holding surface on which the wafer 1 is held horizontally. The holding surface 103b has a suction surface made of, for example, a porous ceramic material. The chuck table 103a is connected to a suction source (not shown) disposed in the base 101 and sucks and holds the wafer 1 with the suction surface of the holding surface 103b. The chuck table 103a is connected to a rotation driving mechanism (not shown), and is rotated while the wafer 1 is held on the holding surface 103b by the rotation driving mechanism. The wafer 1 is placed, for example, by the operator of the grinding apparatus 100 with the center of the wafer 1 aligned with the rotation center of the holding surface 103b of the chuck table 103a as indicated by an arrow A.

  The support column 104 is provided in a rectangular parallelepiped shape, and a grinding unit moving mechanism 104a for moving the grinding unit 105 above the chuck table 103a is provided on the front surface thereof. The grinding unit moving mechanism 104a has a Z-axis table 104b that moves up and down with respect to the support column 104 by a ball screw type moving mechanism. The grinding unit 105 is supported on the Z-axis table 104b via a support portion 104c attached to the front side thereof.

  The grinding unit 105 has a grinding wheel 105a that is detachably attached to the lower end of a spindle (not shown). The grinding wheel 105a is composed of, for example, a diamond grindstone in which diamond abrasive grains are hardened with a binder such as metal bond or resin bond.

  In the primary grinding process using the grinding apparatus 100 having such a configuration, the wafer 1 is placed on the chuck table 103a disposed at the replacement position, and is sucked and held on the holding surface 103b. Moved. Then, the grinding unit 105 is moved downward and is driven to rotate, whereby the processing surface of the wafer 1 exposed on the chuck table 103a is ground by the grinding wheel 105a.

  First, in the primary grinding process, one surface 11 of the wafer 1 is sucked and held by the holding surface 103b of the chuck table 103a. FIG. 4 is a schematic diagram for explaining the state of the wafer 1 in the primary grinding process. As shown in FIG. 4, the undulations 11b and 12b and the warpage of the wafer 1 are corrected in accordance with the holding surface 103b, and the wafer 1 becomes horizontal. Then, the chuck table 103a and the grinding unit 105 rotate relative to each other while the wafer 1 is held in this manner until the processing strain 12a of the second surface 12 of the wafer 1 disposed opposite to the grinding unit 105 is removed. To be ground.

  When the processing distortion 12a of the second surface 12 is removed, the chuck table 103a is moved from the grinding position to the transfer position, and then the suction holding by the holding surface 103b is released, and the front and back of the wafer 1 are reversed by an operator or the like. Is done. That is, the second surface 12 is placed on the chuck table 103a and sucked and held by the holding surface 103b. At this time, similarly to the case where the first surface 11 is sucked and held, the undulations 11b and 12b and the warp of the wafer 1 are corrected in accordance with the holding surface 103b, and the wafer 1 becomes horizontal. Then, the chuck table 103a and the grinding unit 105 rotate relative to each other while the wafer 1 is held in this manner until the processing distortion 11a of the one surface 11 of the wafer 1 disposed to face the grinding unit 105 is removed. To be ground.

  When the processing distortion 11a of one surface 11 is removed, the chuck table 103a is moved from the grinding position to the transfer position, and then the suction and holding by the holding surface 103b is released, and the wafer 1 is picked up by an operator or the like. This completes the primary grinding process. In the primary grinding process, the processing strains 11a and 12a formed on the one surface 11 and the second surface 12 of the wafer 1 are removed as described above, and equivalent grinding strains 11c and 12c are formed as will be described later. It is intended.

  FIG. 5 is a schematic diagram for explaining the state of the wafer 1 after being ground by the primary grinding process. As shown in FIG. 5, in the wafer 1 after the primary grinding, the processing strains 11a and 12a formed on the first surface 11 and the second surface 12 are removed. Instead, grinding distortions 11c and 12c associated with the primary grinding process are formed on the first surface 11 and the second surface 12. Unlike the processing strains 11a and 12a, these grinding strains 11c and 12c are formed in a substantially uniform size from the surfaces of the first surface 11 and the second surface 12. For this reason, the warp of the wafer 1 based on the difference in size is reduced as in the case where the processing strains 11a and 12a are formed.

  In the primary grinding process, grinding is performed in a state where the undulations 11b and 12b are corrected by suction holding by the holding surface 103b of the chuck table 103a. For this reason, in the wafer 1 in a state where such suction holding is released, the undulations 11b and 12b and the warpage generated on the surface layer of the first surface 11 and the second surface 12 cannot be removed. By changing the processing strains 11a and 12a having different sizes to the substantially equivalent grinding strains 11c and 12c, only the warp generated in the wafer 1 is reduced. And the resin application | coating process, a wavy shape return process, and the resin hardening process are implemented with respect to the wafer 1 which the primary grinding process using the grinding device 100 was complete | finished in this way.

  FIG. 6 is an external perspective view showing an example of a resin coating apparatus 200 used in a resin coating process or the like of the flattening method for the wafer 1 according to the present embodiment. FIG. 7 is a schematic view showing a main part of the resin coating apparatus 200 shown in FIG. In FIG. 6, for convenience of explanation, a part of the resin coating apparatus 200 is shown. In the following, for convenience of explanation, the lower right side shown in FIG. 6 is called the front side of the resin coating apparatus 200, and the upper left side shown in FIG. 6 is called the rear side of the resin coating apparatus 200. Furthermore, in the following, for convenience of explanation, the vertical direction shown in FIG. 6 is referred to as the vertical direction of the resin coating apparatus 200.

  As shown in FIG. 6, the resin coating apparatus 200 has a base 201 whose inside is hollow. A rectangular stage 202 having a horizontal holding surface 202 a is disposed on the upper part of the base 201. The stage 202 is made of, for example, borosilicate glass or quartz glass that transmits ultraviolet rays, and the lower surface thereof is in a state of facing the hollow in the base 201. A plurality of UV lamps 203 for irradiating ultraviolet rays toward the stage 202 are arranged in parallel at the bottom of the base 201.

  In addition, the base 201 is provided with a rectangular plate-like shutter 205 that is advanced and retracted above the UV lamp 203 by the drive mechanism 204 and blocks an ultraviolet irradiation light path from the UV lamp 203 to the upper side when advanced. Although only one shutter 205 is shown in FIG. 6, a pair of left and right shutters are provided as shown in FIG. 7, and a drive mechanism 204 is connected to each shutter 205. The drive mechanism 204 is controlled so that these shutters 205 can be opened and closed. Opening these shutters 205 irradiates the stage 202 with ultraviolet rays from the UV lamp 203, while closing the shutters 205 blocks the ultraviolet irradiation from the UV lamps 203.

  Above the shutter 205, a rectangular plate-shaped filter 206 that blocks light other than ultraviolet rays is disposed. As shown in FIG. 7, the filter 206 is held on the side wall portion of the base 201. The filter 206 divides the space in the base 201 up and down. An exhaust duct 207 communicating with the space above the filter 206 in the base 201 is provided on the side wall of the base 201. The exhaust duct 207 is connected to an exhaust mechanism (not shown) and is configured to be able to exhaust the air in the base 201. By discharging the air in the base 201 whose temperature has increased with the irradiation of the UV lamp 203 through the exhaust duct 207, it is possible to prevent the flatness of the holding surface 202a from being lowered.

  A wall 208 is provided on the rear side of the stage 202 in the base 201. At the upper end portion of the wall portion 208, a flange portion 209 (shown in FIG. 6) that extends forward in parallel with the stage 202 is provided. The flange 209 is provided with holding means 210 configured to suck and hold the wafer 1 horizontally and to move the wafer 1 in the vertical direction.

  The holding means 210 includes a main rod 210a extending from the vicinity of the center of the flange portion 209 toward the stage 202, and a plurality of (four in this embodiment) sub-rods 210b (in the present embodiment) disposed around the main rod 210a (see FIG. 6) and a disc-shaped pressing pad 210c fixed horizontally to the lower ends of the main rod 210a and the sub rod 210b. The main rod 210a and the sub rod 210b are provided with driving parts 210d and 210e, respectively, and these driving parts 210d and 210e are fixed to the flange part 209. When these drive units 210d and 210e are driven, the main rod 210a and the sub rod 210b extend downward, while operating so as to shrink upward, and the pressing pad 210c is raised and lowered.

  As shown in FIG. 7, a holding portion 211 for sucking and holding the wafer 1 is provided on the lower surface of the pressing pad 210c. The holding portion 211 has a suction surface 211a made of, for example, a porous ceramic material. The holding unit 211 is connected to a suction source (not shown), and sucks and holds the wafer 1 with the suction surface 211a. Similar to the case where the chuck table 103a of the grinding apparatus 100 described above is sucked and held, the wafer 1 is sucked and held by the holding unit 211 with the undulations 11b and 12b and the warp corrected.

  A resin coating process, a wavy shape restoration process, and a resin curing process are performed using the resin coating apparatus 200 having such a configuration. In the resin coating process, an ultraviolet curable resin is applied to the entire surface of the second surface 12 of the wafer 1 so as to maintain the wafer 1 in a state where the undulations 11b and 12b are restored in the resin curing process described later. . In the resin coating process, the wafer 1 that has finished the primary grinding process is carried into the stage 202 and placed at a predetermined position on the holding surface 202a. At this time, the wafer 1 is loaded so that the second surface 12 is placed on the holding surface 202a and the first surface 11 is exposed. For example, the wafer 1 is loaded onto the stage 202 while being placed on a film that is transported from the left side to the right side of the resin coating apparatus 200.

  The pressing pad 210c of the holding unit 210 is moved downward, and the pressing pad 210c is moved upward to a standby position separated from the stage 202 by a certain distance while the wafer 1 is sucked and held by the holding unit 211. Then, an appropriate amount of ultraviolet curable resin is dropped onto the film that has transported the wafer 1. Thereafter, the pressing pad 210c of the holding means 210 is moved downward, and the second surface 12 of the held wafer 1 is pressed with a uniform pressing force on the entire surface in the direction of the stage 202 where the ultraviolet curable resin is dropped.

  8 and 9 are schematic views for explaining the state of the wafer 1 in the resin coating process. FIG. 8 shows a state before the wafer 1 is pressed against the stage 202 onto which the ultraviolet curable resin 212 is dropped, and FIG. 9 shows a state after the wafer 1 is pressed. 8 and 9, only a part of the film 213 corresponding to the wafer 1 is shown for convenience of explanation. As shown in FIGS. 8 and 9, in the resin coating process, the wafer 1 is held by suction with the one surface 11 held by the holding portion 211 of the holding means 210. At this time, the wafer 1 is sucked and held in a state in which the undulations 11b and 12b and the warp are corrected following the suction surface 211a.

  The wafer 1 sucked and held by the holding unit 211 is moved downward as indicated by an arrow A in FIG. 8 and placed on the stage 202 (more precisely, the film 213 disposed on the stage 202). Then, as shown by an arrow B in FIG. 9, the entire surface is pressed from the side of one surface 11 toward the stage 202 with a uniform pressing force. As a result, the ultraviolet curable resin 212 is spread out below the second surface 12 of the wafer 1, and the ultraviolet curable resin 212 is applied to the entire surface of the second surface 12. In this way, the resin coating process is completed, and the process proceeds to the waviness shape restoration process.

  In the waviness shape restoration step, the suction holding by the holding portion 211 is released, and the pressing force applied in the resin coating step by the pressing pad 210c is released, whereby the one surface 11 and the second surface 12 of the wafer 1 are released. This is a step of returning the undulations 11b and 12b. FIG. 10 is a schematic diagram for explaining the state of the wafer 1 in the waviness shape restoration process. When the suction holding by the holding unit 211 is released and the pressing pad 210c is moved upward as indicated by an arrow C in FIG. 10, the wafer 1 is staged with the second surface 12 placed on the ultraviolet curable resin 212. 202 is left. At this time, the undulations 11 b and 12 b return to the first surface 11 and the second surface 12 due to the internal stress of the wafer 1.

  Note that the resin coating step and the waviness shape return step are performed with the pair of shutters 205 closed as shown in FIG. That is, since the UV curable resin 212 dropped on the film 213 of the stage 202 is not cured, the undulations 11b are applied to both surfaces of the wafer 1 or on both surfaces of the wafer 1 when applied to the entire surface of the second surface 12 of the wafer 1. It does not hinder the operation when 12b returns. In this way, the swell shape return process is completed, and the process proceeds to the resin curing process.

  The resin curing step is a step of curing the ultraviolet curable resin 212 so as to maintain the shape of the undulations 11b and 12b restored in the undulation shape restoration step. In the resin curing step, the ultraviolet curable resin 212 on which the wafer 1 is placed is irradiated with the ultraviolet rays from the UV lamp 203 and cured. FIG. 11 is a schematic diagram for explaining the state of the wafer 1 in the resin curing step. The resin curing process is performed with the shutter 205 shown in FIG. 7 in an open state. By opening the shutter 205, the ultraviolet rays from the UV lamp 203 are irradiated through the stage 202 and the film 213, and the ultraviolet curable resin 212 is cured.

  By irradiating the ultraviolet rays in this way, the wafer 1 is fixed on the film 213 in a state where the shapes of the undulations 11b and 12b are maintained. Since the ultraviolet curable resin 212 is cured on the film 213 placed on the horizontal holding surface 202a, a flat surface 212a based on the holding surface 202a is formed on the lower surface thereof. ing. If the ultraviolet curable resin 212 is cured in this way, the resin curing process is completed.

  And the one surface waviness removal process, the resin peeling process, and the second surface waviness removal process are performed with respect to the wafer 1 in which the resin coating process, the waviness shape restoration process, and the resin curing process using the resin coating apparatus 200 are completed. To be implemented. For example, the grinding apparatus 100 shown in FIG. 3 used in the primary grinding process is used in the first surface waviness removing process and the second surface waviness removing process. Note that these one surface waviness removing step and second surface waviness removing step can be referred to as a secondary grinding step.

  The one surface waviness removing step is a step of grinding and removing the waviness 11b formed on one surface 11 of the wafer 1 in the resin curing step. FIG. 12 is a schematic diagram for explaining the state of the wafer 1 in one surface waviness removal process. Note that FIG. 12 shows a state in which the undulation 11b of one surface 11 is removed by grinding of the grinding unit 105. As shown in FIG. 12, in the wafer 1, the flat surface 212a of the ultraviolet curable resin 212 is sucked and held by the holding surface 103b through the film 213. At this time, the shape of the undulation 11b is maintained on one surface 11 of the wafer 1 (the state shown in FIG. 11). Grinding by the grinding unit 105 is performed in the state of being sucked and held in this way.

  Thus, in the one surface waviness removing step, since the grinding by the grinding unit 105 is performed while maintaining the shape of the waviness 11b of the one surface 11, the waviness 11b of the first surface 11 is effectively removed. It has become something that can be. And as shown in FIG. 12, when the wave | undulation 11b of the one surface 11 is removed, the one surface wave | undulation removal process will be completed and it will transfer to a resin peeling process.

  In the resin peeling step, the ultraviolet curable resin 212 covering the second surface 12 of the wafer 1 is peeled off. The resin peeling step is performed, for example, by an operator or the like when shifting from the one surface waviness removing step to the second surface waviness removing step. FIG. 13 is a schematic diagram for explaining the state of the wafer 1 in the resin peeling step. FIG. 13 shows the state of the process of peeling the cured ultraviolet curable resin 212 from the wafer 1. As shown in FIG. 13, in the resin peeling process, the ultraviolet curable resin 212 covering the second surface 12 of the wafer 1 is peeled off together with the film 213. On the second surface 12 from which the ultraviolet curable resin 212 has been peeled off, the shape of the undulation 12b is maintained. By removing all the cured UV curable resin 212 from the wafer 1, the resin peeling process is completed, and the process proceeds to the second surface waviness removing process.

  In the second surface waviness removing step, waviness 12b formed on the second surface 12 of the wafer 1 exposed in the resin peeling step is ground and removed. FIG. 14 is a schematic diagram for explaining the state of the wafer 1 in the second surface waviness removal process. FIG. 14 shows a state in which the waviness 12b of the second surface 12 is removed by grinding of the grinding unit 105. As shown in FIG. 14, in the wafer 1, the undulation 11b is removed in one surface undulation removal process, and the flattened one surface 11 is sucked and held by the holding surface 103b. At this time, the waviness 12b is maintained on the second surface 12 of the wafer 1 (the state where the front and back of the wafer 1 shown in FIG. 13 are reversed). Grinding by the grinding unit 105 is performed in a state in which the flattened one surface 11 is sucked and held as a reference surface.

  Thus, in the second surface waviness removal step, since the flattened one surface 11 is used as a reference surface, grinding by the grinding unit 105 is performed in a state where the shape of the waviness 11b of the first surface 11 is maintained. The waviness 11b on the second surface 12 can be effectively removed. Then, as shown in FIG. 14, when the undulation 12b of the second surface 12 is removed, the second undulation removal process is completed, and the flat processing method of the wafer 1 according to the present embodiment is completed.

  Thus, in the flat processing method of the wafer 1 according to the present embodiment, in the primary grinding step, the processing distortion 11a is obtained by grinding the one surface 11 and the second surface 12 of the wafer 1 obtained by cutting out from the ingot. , 12a is removed, the warpage due to the difference in the size of the processing strains 11a, 12a is reduced. And in the resin application process, the waviness shape restoration process, and the resin curing process, the mold 1 is cured and cured with the ultraviolet curing resin 212 while maintaining the waviness 11b and 12b of the wafer 1 for the wafer 1 with reduced warpage. is doing. Further, the waviness 11b and 12b generated on the surface layer of the wafer 1 is removed in the secondary grinding step (first surface, second surface waviness removing step) in a state of being cured with the ultraviolet curable resin 212 in this way. Therefore, since the warpage caused by the distortion of the wafer when cutting from the ingot and the waviness of the surface layer on both surfaces of the wafer can be effectively removed, a wafer with high flatness can be obtained.

  Next, an example that demonstrates the effect obtained by the flat processing method of the wafer 1 according to the present invention will be described. In the following embodiment, a verification result in the case where a 12-inch wafer 1 cut out from an ingot by a cutting device is a processing target is shown.

  In the example, whether or not the waviness of the wafer 1 can be removed based on whether or not the grinding process (primary grinding process, secondary grinding process) is performed, and the influence on the removal rate of the warp were verified. Table 1 shows verification results when only the primary grinding process is performed, when only the secondary grinding process is performed, and when both the primary grinding process and the secondary grinding process are performed. As described above, the secondary grinding step is composed of one surface waviness removing step and second surface waviness removing step, and includes a resin peeling step. Further, the other steps (resin application step, waviness shape return step, resin curing step) in the method of flattening the wafer 1 according to the present invention are carried out in the same manner in any of the verification results.

  As shown in Table 1, when only the primary grinding process is performed, the undulations formed on the wafer 1 cannot be removed, and the removal rate of the warp generated on the wafer 1 is also the verification result of performing another grinding process. It was low compared to. In addition, when only the secondary grinding process was performed, the waviness formed on the wafer 1 could be removed, but the removal rate of the warp generated on the wafer 1 was verified by performing the primary grinding process and the secondary grinding process. It was lower than the result. On the other hand, when the primary grinding process and the secondary grinding process are performed, the waviness formed on the wafer 1 can be removed, and the removal rate of the warp generated on the wafer 1 is also compared with the verification results obtained by performing other grinding processes. It was expensive. From the above results, by performing the primary grinding process and the secondary grinding process, the waviness of the wafer 1 formed when cutting out from the ingot and the warp generated in the wafer 1 can be effectively removed, and the wafer with high flatness 1 could be obtained.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  For example, in the above-described embodiment, the case where the ultraviolet curable resin 212 is dropped on the film 213 in the resin coating apparatus 200 that performs the resin coating process, the wavy shape restoration process, and the resin curing process has been described. The object to which the cured resin 212 is dropped is not limited to this, and can be changed as appropriate. For example, the ultraviolet curable resin 212 may be dropped directly on the holding surface 202a of the stage 202. However, considering the operation of transporting the wafer 1 that has undergone the resin curing step and the operation of peeling the ultraviolet curable resin 21 from the wafer 1 that has undergone the one surface waviness removing step, the ultraviolet curable resin 212 is dropped on the film 213. This is preferable as an embodiment.

  In the above embodiment, in the resin coating apparatus 200, the wafer 1 conveyed to the stage 202 by the film 213 is sucked and held by the holding means 210 and moved upward, and then the ultraviolet curable resin 212 is dropped. Explains. However, the method of disposing the ultraviolet curable resin 212 between the wafer 1 and the film 213 is not limited to this and can be appropriately changed. For example, the ultraviolet curable resin 212 may be disposed between the wafer 1 and the film 213 in the process of transporting the film 213 to the stage 202. Even in this case, a wafer with high flatness can be obtained as in the above embodiment.

  Furthermore, in the said embodiment, although the case where the wafer 1 which the primary grinding process was complete | finished is demonstrated to the stage 202 of the resin coating apparatus 200 with the film 213, about the conveyance means which conveys the wafer 1, it is a film. It is not limited to 213 and can be changed as appropriate. For example, you may make it convey to the stage 202 with the conveyance arm which has a suction holding | maintenance function. Even in this case, a wafer with high flatness can be obtained as in the above embodiment.

  As described above, according to the present invention, one surface and two surfaces of a wafer obtained by cutting out from an ingot are ground (primary grinding) to equalize the distortion on both surfaces of the wafer and reduce warpage. After that, the undulation generated on the surface layer of the first surface and the second surface is ground (secondary grinding) so as to remove these undulations while maintaining the shape of the undulation with the ultraviolet curable resin. It is possible to effectively remove the warpage caused by wafer distortion (processing distortion) during cutting and surface waviness on both surfaces of the wafer, and the effect that the wafer can be processed flatly. This is useful for a grinding apparatus that requires flatness.

1 wafer (as-sliced wafer)
DESCRIPTION OF SYMBOLS 100 Grinding apparatus 101 Base 103a Chuck table 103b Holding surface 105 Grinding unit 105a Grinding wheel 200 Resin coating apparatus 201 Base 202 Stage 202a Holding surface 203 UV lamp 205 Shutter 206 Filter 210 Holding means 210c Press pad 211 Holding part 212 UV curable resin 213 film

Claims (1)

The wafer obtained by cutting out from the ingot, warping due to the difference in the magnitude of distortion generated on one surface by cutting and the two surfaces opposite to the one surface, and the one surface and the second surface by cutting A flat processing method of processing both surfaces of the wafer having waviness generated on a surface layer of the surface,
Until the distortion of the second surface of the wafer, which is exposed in a state where the waviness is corrected and leveled by sucking and holding the one surface of the wafer to the horizontal holding surface of the chuck table, is removed. While grinding, the two surfaces of the wafer are sucked and held on the horizontal holding surface, thereby correcting the waviness and removing the distortion of the one surface of the wafer exposed in a horizontal state. A UV curable resin is dropped onto a film placed on a stage having a horizontal holding surface, and a grinding process for forming an equivalent grinding strain on the one surface and the second surface. The two surfaces of the wafer having been subjected to the grinding step are placed on a cured resin, and a uniform pressing force is applied to the entire surface from the exposed one surface side toward the stage. A resin coating step of coating the entire surface of the second surface with the ultraviolet curable resin, and after applying the ultraviolet curable resin, the pressing force in the direction of the stage from the one surface side is released, and the waviness of the wafer After the wavy shape return step for restoring the shape, a resin curing step for curing the resin by irradiating the ultraviolet curable resin with ultraviolet rays, and after the resin curing step, Grinding until the undulation of the surface layer of the second surface is removed with the one surface undulation removing step of grinding until the undulation of the surface layer is removed, and the one surface flattened with the undulation removed. A method for flattening a wafer, comprising: a second surface waviness removing step.

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