JP5324212B2 - Resin coating method and resin coating apparatus - Google Patents

Abstract

The present invention provides a resin cladding method and a resin cladding device that are capable of smoothing the tilting or bending part of a workpiece for forming a grinded workpiece that is smooth. A wafer (1) containing a tilting or bending part is loaded on a resin (P1) plate, a pressing pad (23) is used to press the resin (P1), and then the wafer (1) is absorbed and held on an adsorption part (24) of the pressing pad (23) to raise the wafer (1) together with the pressing pad (23) to a position corresponding to a deformation element, in the stage, the wafer (1) is made to generate a deformation for smoothing a tilting part and the like, after that, the pressing pad (23) is departed from the wafer (1) in a reverse direction, thereafter, the resin (P1) is solidified. Therefore, a grinded smooth wafer (1) can be obtained by making the pressed wafer (1) deformed thoroughly on the resin (P1).

Description

  The present invention relates to a method of forming one surface of a workpiece with a resin and grinding the surface of the workpiece as a reference surface for grinding the workpiece when a thin plate-like workpiece such as a semiconductor wafer is ground to a flat surface.

  Semiconductor wafers used as materials for semiconductors and electronic components include those made of a single crystal material such as silicon and those made of a compound having a plurality of elements. These wafers are formed into a cylindrical ingot and then sliced into a substrate with a wire saw or the like. Further, lapping, etching, etc. are applied to remove waviness and warpage generated during slicing, and the wafer is processed flat and thin.

  However, in order to perform the above etching, a large facility is required in which a reactive gas is supplied and retained around the wafer, and plasma is generated by applying a high voltage to the reactive gas. Further, as a gas capable of etching silicon used for a wafer, there is a fluoride gas such as SF6, for example. This kind of gas is a warming gas and is expensive. Therefore, in order to perform the etching, there is a drawback that a large amount of equipment and expensive gas are used, and a large amount of cost is required.

  Therefore, a method has been proposed in which swell and warpage of a wafer are removed by applying a resin, wax or the like to one side of the wafer and curing it to form a coating, and then grinding the wafer (Patent Document 1). 2). In these methods, the applied resin is cured to form a coating with a flat surface, and the wafer is ground using the surface of the coating as a reference surface, thereby removing the waviness and warpage of the wafer. Processed flat.

Japanese Patent Laid-Open No. 8-66850 JP 2006-269761 A

  However, in the method of Patent Document 1, the following problem may occur depending on the thickness of the coating formed on one surface of the wafer. For example, when the thickness of the coating applied to the wafer is thin, the coating cannot sufficiently absorb swell and warpage. In addition, when the thickness of the coating applied to the wafer is large, when the wafer is ground by pressing the rotated grinding wheel against the wafer using a general grinding device, the grinding stone is removed from the grinding wheel by the elastic action of the coating. The wafer escapes, and there arises a problem that it is difficult to grind the wafer to a uniform thickness even if waviness and warpage can be removed.

  On the other hand, in the method of Patent Document 2, since the coating can be controlled to an appropriate film thickness, undulation and warpage can be effectively removed. However, since the resin or the like is cured with the internal stress remaining on the wafer, if the coating is removed after the wafer is ground, the spring back such that waviness and warpage are restored again due to the internal stress remaining in the wafer. It may occur and is not always satisfactory.

  Therefore, the present invention appropriately removes the waviness and warpage of the workpiece when the resin is coated on one surface of the workpiece in order to grind and flatten the thin plate workpiece such as the wafer including deformation elements such as waviness and warpage. As a result, an object of the present invention is to provide a resin coating method and apparatus capable of forming a workpiece after grinding flat.

The resin coating method of the present invention is a resin coating method in which one surface of a thin plate workpiece including deformation elements such as waviness and warpage is ground and processed to be flat so that the other surface of the workpiece is coated with resin. A workpiece placing step of placing the workpiece on the curable resin supplied in a predetermined state in a lump state on the workpiece placement surface of the stage, and placing the other surface in accordance with the resin, and the workpiece by the pressing means Corresponding to at least the deformation element in the direction from the other surface to the one surface in a state where the workpiece is held by the pressing means with the workpiece pressing step of pressing toward the block-shaped resin from the one surface side A workpiece moving step for moving to a position to be moved, a pressing unit separating step for separating the pressing unit from one surface of the workpiece, and a resin curing step for curing the resin by applying a stimulus to the curable resin by an external stimulus applying unit. And at least It is characterized in that to obtain.

  In the resin coating method of the present invention, by moving the workpiece to a position corresponding to at least the deformable element in the workpiece moving step, the workpiece that has been flattened by pressing has the original shape while flowing the resin by internal stress, Or it returns to the state close to the original shape. The “position corresponding to the deformation element” in the present invention means a position where the workpiece deformed in the pressing step can return to the original shape. By performing this work movement process, the work can be reproduced in a deformed state before pressing on the resin. As a result, when the resin is removed from the workpiece after grinding one surface of the workpiece after the resin is cured, the workpiece is less likely to be deformed, and the flatly ground workpiece can be held in a flat state as it is. .

  Examples of the curable resin used in the resin coating method of the present invention include an ultraviolet curable resin that is cured by ultraviolet irradiation. In this case, the external stimulus imparting unit is an ultraviolet irradiation unit that irradiates ultraviolet rays.

  Examples of the other curable resin include a thermosetting resin that is cured by being heated, and a thermoplastic resin that is liquefied by being heated and is cured by being cooled. The external stimulus applying means in the case of a thermosetting resin is a heating means for heating, and the external stimulus applying means in the case of a thermoplastic resin is a cooling means for cooling.

Next, the resin coating apparatus of the present invention can suitably carry out the resin coating method of the present invention, and a work holding means for detachably holding the work in a state where the other surface is exposed, A stage having a workpiece placement surface opposed to the workpiece holding means, to which a predetermined amount of a lump of curable resin is supplied to the workpiece placement surface, and the workpiece on the workpiece placement surface of the stage ; A pressing unit that presses the curable resin supplied in a predetermined amount in a state, and a workpiece moving unit that moves the workpiece pressed toward the curable resin by the pressing unit in a direction from one surface to the other surface. And an external stimulus applying means for applying an external stimulus to the curable resin supplied to the work placement surface of the stage.

  In addition, although the workpiece | work said by this invention is not specifically limited, For example, the semiconductor wafer which consists of silicon, gallium arsenide, etc., the wafer which consists of inorganic compounds, such as sapphire (aluminum oxide), etc. are mentioned.

  According to the present invention, by moving the workpiece pressed against the resin applied to the stage in a direction away from the stage at least to a position corresponding to the deformation element, the workpiece can be reproduced in the original deformation state. Even if the resin is removed from the workpiece after grinding, the workpiece is not deformed, and a flat workpiece can be obtained.

Hereinafter, an embodiment according to the present invention will be described with reference to the drawings.
[1] Semiconductor Wafer FIG. 1 shows a semiconductor wafer (hereinafter referred to as a wafer) which is a work in one embodiment. The wafer 1 is in a material stage obtained by slicing a cylindrical material ingot made of silicon or the like to a predetermined thickness with a wire saw. The wafer 1 is wavy and warped due to resistance generated at the time of cutting. The wafer 1 is coated with an ultraviolet curable resin on the back surface 1b and cured, and then the front surface 1a is ground, and then the back surface 1b is ground and flattened, and then the electronic circuit is applied to the ground surface. A pattern composed of a plurality of devices having the above is formed.

[2] Configuration of Resin Coating Apparatus FIG. 2 shows a resin coating apparatus 10 according to an embodiment that supplies a resin to the back surface 1b of the wafer 1 and cures the resin. In FIG. 2, reference numeral 11 denotes a hollow base, and a rectangular plate-like stage 12 having a flat upper surface and a horizontal workpiece placement surface 12 a is disposed on the base 11. The stage 12 is made of borosilicate glass, quartz glass, or the like that transmits ultraviolet rays, and the lower surface of the stage 12 faces the hollow inside the base 11.

  A plurality of UV lamps 13 for irradiating ultraviolet rays (ultraviolet light) toward the upper stage 12 are disposed at the bottom of the base 11. Further, the base 11 is provided with a rectangular plate-like shutter 15 that moves forward and backward with respect to the upper side of the UV lamp 13 by the cylinder 14 and blocks the ultraviolet irradiation light path to the upper side of the UV lamp 13 at the time of advancement. Although only one shutter 15 is shown in FIG. 2, there is a pair of left and right shutters as shown in FIG. 3, and a cylinder 14 is connected to each shutter 15.

  The cylinder 14 has a piston rod 14a that expands and contracts horizontally in the direction of the base 11, and a shutter 15 is fixed to the tip of the piston rod 14a in a horizontal state. When the piston rod 14a extends, as shown in FIG. 3, the left and right shutters 15 advance above the UV lamps 13, the tips abut against each other and close, and UV irradiation from the UV lamps 13 is blocked. Is done. Further, when the piston rod 14a is contracted, as shown in FIG. 5B, each shutter 15 is retracted from the upper side of the UV lamp 13 to be in an open state, and ultraviolet rays are irradiated from the UV lamp 13 toward the stage 12. .

  As shown in FIG. 3, a rectangular plate-like filter 16 that blocks light other than ultraviolet rays is disposed above the shutter 15 in the base 11. By this filter 16, the space in the base 11 is partitioned up and down. As shown in FIG. 2, a cylindrical duct 17 that communicates with the space above the filter 16 in the base 11 is provided on the side wall 11 a of the base 11. The duct 17 is connected to an exhaust means (not shown) for sucking and discharging the air in the base 11.

  Since the temperature inside the base 11 rises due to the ultraviolet rays emitted from the UV lamp 13, the stage 12 may thermally expand, and the flatness of the work placement surface 12a of the stage 12 may be lowered. Therefore, by discharging the air on the lower surface side of the stage 12 from the duct 17, the temperature rise of the stage 12 is suppressed and the flatness of the workpiece placement surface 12a is maintained. Further, unnecessary light components are blocked by the filter 16, and this also maintains the flatness of the work placement surface 12a.

  As shown in FIG. 2, a back plate portion 18 is erected on the back side of the stage 12 in the base 11, and a collar portion 19 extending above the stage 12 is provided at the upper end portion of the back plate portion 18. Is formed. The flange portion 19 is provided with wafer holding means 20 for horizontally holding and holding the wafer 1 and moving the held wafer 1 downward.

  The wafer holding means 20 includes a main rod 21 extending from a substantially center of the flange portion 19 to a space between the lower stage 12 and the flange portion 19, and a plurality of (in this case, 4) disposed around the main rod 21. And a disc-shaped pressing pad 23 that is horizontally fixed to the lower ends of the rods 21 and 22. The rods 21 and 22 arranged in parallel with each other are provided with drive portions 21A and 22A at the upper end portions, and these drive portions 21A and 22A are fixed to the flange portion 19. When the drive units 21A and 22A are respectively operated, the rods 21 and 22 operate so as to extend downward or contract upward, and the pressing pad 23 moves up and down as the rods 21 and 22 expand and contract.

  As shown in FIG. 3, a suction portion 24 is provided on most of the lower surface of the pressing pad 23. The suction part 24 is formed in a disk shape by a porous material, and when a connected air suction source (not shown) is operated, a negative pressure is generated on the suction surface 24a which is a flat lower surface of the suction part 24. The wafer 1 is sucked and held on the suction surface 24a.

[3] Operation of Resin Coating Device Next, the operation of the resin coating device 10 will be described. During this operation, the resin coating method of the present invention is included.

  As an initial state, as shown in FIG. 3A, the UV lamp 13 is always on and irradiates ultraviolet rays, but the shutter 15 is closed and the stage 12 is not irradiated with ultraviolet rays. The pressing pad 23 is positioned at the upper standby position.

From this state, as shown in FIG. 3B, a predetermined amount of liquid resin P <b> 1 is supplied to the center of the work placement surface 12 a of the stage 12 in a lump state. As the resin P1 to be supplied, an ultraviolet curable type that is cured by being irradiated with ultraviolet rays is used, and a viscosity of, for example, about 50 to 30000 mPa is selected. Next, as shown in FIG. 3C, the wafer 1 is placed on the resin P1 supplied to the workpiece placement surface 12a ( work placement step ).

  Subsequently, the driving units 21A and 22A are operated to extend the rods 21 and 22 downward to lower the pressing pad 23, to bring the suction surface 24a of the suction unit 24 into contact with the surface 1a of the pressing pad 23, and further press The pad 23 is lowered and the wafer 1 is pressed toward the resin P1. Then, as shown in FIG. 4 (a), the resin P1 is spread and protrudes from the back surface of the wafer 1, and a state in which the resin P1 is uniformly distributed over the entire back surface 1b of the wafer 1 is secured (work pressing). Process).

  When the resin P1 is applied to the entire back surface 1b of the wafer 1 in this way, a negative pressure is generated in the suction portion 24 of the pressing pad 23, and the surface 1a of the wafer 1 is sucked to the suction surface 24a to become flat. The wafer 1 is held by the suction unit 24. When the wafer 1 is held by the suction unit 24, the operation of the drive units 21A and 22A is stopped or the pressure applied to the resin P1 by the operation is reduced. Then, the load pressing the wafer 1 against the resin P1 by the pressing pad 23 is weakened, and the wafer 1 held by the pressing pad 23 is slightly received by the repulsive force of the resin P1 as shown in FIG. As a result, the thickness of the resin P1 is slightly increased (work movement process). The rising amount of the wafer 1 here is set to a position where the wafer 1 is sufficiently deformed to return to the original shape within the thickness of the resin P1 after rising (a position corresponding to the deformation element).

  Next, after releasing the state of holding the wafer 1 by stopping the negative pressure operation of the pressing pad 23, as shown in FIG. 5A, the pressing pad 23 is raised and returned to the standby position, The suction surface 24a is separated from the surface 1a of the wafer 1 (pressing means separation step). When the pressing pad 23 is separated from the wafer 1, the flattened wafer 1 is deformed to return to the original state due to internal stress. The deformation of the wafer 1 at this time is possible because the resin P1 has not been cured yet, and the deformation occurs while the resin P1 is flowing.

  Next, the shutter 15 is opened as shown in FIG. Then, the ultraviolet rays emitted from the UV lamp 13 are applied to the resin P1 through the filter 16 (resin curing step). The resin P1 irradiated with ultraviolet rays is cured, and a resin film P2 in close contact with the back surface 1b is formed on the back surface 1b of the wafer 1, so that the wafer 1 can be taken out from the work placement surface 12a. The surface (lower surface) of the resin film P2 that is in close contact with the workpiece placement surface 12a is formed flat by transferring the flat workpiece placement surface 12a.

[4] Flattening by grinding the wafer The wafer 1 having the back surface 1a coated with the resin film P2 as described above is transferred to a flattening process in which both surfaces are ground. FIG. 6 shows a grinding spindle 30 and a chuck table 40 for grinding the wafer 1.

  The grinding spindle 30 has a configuration in which a spindle shaft 33 rotated by a motor 32 is built in a cylindrical housing 31, and a grindstone wheel 35 is fixed to the spindle shaft 33 via a flange 34. The grinding spindle 30 is installed in a state where the axial direction of the spindle shaft 33 is along the vertical direction, and can be moved up and down by a lifting mechanism (not shown). The grindstone wheel 35 has a plurality of grindstone chips 37 arranged in an annular shape and fixed to the lower surface of an annular frame 36.

  The chuck table 40 is disposed below the grinding spindle 30 so as to face the grinding wheel 35. The horizontal upper surface of the chuck table 40 is constituted by an adsorption portion 41 that adsorbs and holds a workpiece by the action of negative pressure. The suction portion 41 is the same as the suction portion 24 of the pressing pad 23 of the resin coating apparatus 10, is formed in a disk shape with a porous material, and has an upper surface serving as a suction surface 41a. The chuck table 40 is rotated by a rotation driving means (not shown).

  In the grinding of the wafer 1, first, as shown in FIG. 6, the resin film P2 is adsorbed on the adsorption surface 24a of the adsorption unit 24, and the wafer 1 is held on the chuck table 40 in a state where the surface 1a is exposed. Then, the chuck table 40 is rotated, while the grinding wheel 37 that rotates while the grinding spindle 30 is lowered is pressed against the surface of the wafer 1. Thereby, the surface 1a of the wafer 1 is ground. In this case, the entire outer surface of the rotating grinding wheel 35 passes through the center of the rotating wafer 1, whereby the entire surface of the wafer 1 is ground and the surface is processed to be flat.

  When the front surface 1a of the wafer 1 is processed flat as shown in FIG. 7A, the resin film P2 is then peeled off from the back surface 1b of the wafer 1 and removed as shown in FIG. Then, the ground surface 1a is attracted to the attracting surface 24a, and the wafer 1 is held on the chuck table 40 so that the back surface 1b is exposed. Next, the back surface 1b is ground by the grinding spindle 30 while rotating the chuck table 40, and the back surface 1b is processed flat as shown in FIG. As described above, as shown in FIG. 7D, the front surface 1a and the back surface 1b are processed flat and parallel to each other, and the wafer 1 having a uniform thickness is obtained.

[5] Effect of Embodiment In the embodiment in which the resin film P2 is coated on the back surface 1b of the wafer 1 by the resin coating apparatus 10 as described above, the wafer 1 including undulations and warpage placed on the resin P1 is used. The point is that after pressing toward the resin P1 with the pressing pad 23, the wafer 1 is held on the pressing pad 23 to raise the wafer 1, and then the resin P1 is cured.

  By raising the wafer 1 after pressing and increasing the thickness of the resin P1, the wafer 1 that has been flattened by pressing is deformed so as to return to its original shape while flowing the resin P1 due to internal stress. The deformation state can be reproduced. For this reason, the shape of the wafer 1 is maintained in the original deformed state with the resin P1 cured, and the wafer 1 is hardly deformed even after the resin film P2 is removed from the wafer 1. Therefore, the flatly ground wafer 1 is held in a flat state as it is.

  Further, since the wafer 1 is brought into close contact with the resin P1 and corrected flatly just before the pressing pad 23 is separated from the wafer 1, the wafer 1 on the resin P1 is generated in a gravitational environment. It can have a strict flatness in consideration of deflection. Conventionally, a wafer that has been deformed is placed on a resin without considering the deformation of the wafer due to bending, and the wafer is fixed on the resin in a shape including the deformation due to bending, and then ground.

Therefore, the conventional wafer includes an internal stress due to the deflection, and a new warp is generated due to the internal stress due to the deflection in a weightless environment. However, the wafer 1 that has been corrected to be flat and then released is fixed to the resin P <b> 1 in a deformed shape mainly due to warping by alleviating the influence of gravity. For this reason, the obtained wafer 1 does not include or is close to the internal stress due to deflection. As a result, the wafer 1 has a more flat shape even under zero gravity.

In this case, as the resin used in this case, an appropriate viscosity and thickness are selected in consideration of various factors such as the material, structure, shape, and inherent internal stress of the wafer 1, The effect of the present invention can be obtained more remarkably. In other words, the appropriate viscosity and thickness are considered to allow the deformation of the wafer after the correction is canceled due to warpage and suppress the deformation due to deflection. In other words, it can be said that the resin pushes back the force generated on the wafer by gravity with almost the same force.

[6] Operation of Resin Coating Apparatus According to Other Embodiments In the above embodiment, the wafer 1 is placed on the resin P1 supplied to the stage 12 as shown in FIG. Although pressing toward the resin P1, the wafer 1 that has been flattened by correcting the deformation may be pressed against the resin P1.

  By adsorbing and correcting the wafer 1, the wafer 1 is deformed so that the deformation such as the original swell and warp is flattened. Then, the resin P1 is pressed and the resin P1 supplied to the workpiece placement surface 12a of the stage 12 is spread. However, since the wafer 1 is flattened, the resin P1 is uniformly distributed over the entire back surface 1b of the wafer 1. Cheap. In addition, there is an advantage that bubbles are less likely to enter between the wafer 1 and the resin P1.

  Further, in the present embodiment, the resin P1 is applied to the back surface 1b of the wafer 1 by supplying the block-shaped resin P1 to the workpiece placement surface 12a of the stage 12 and pressing the resin P1 with the wafer 1. In this embodiment, the amount of the resin P1 to be used can be set to the minimum amount that can be applied to the back surface 1b of the wafer 1, and as a result, the amount of resin used can be suppressed and the cost can be reduced. Further, since the resin P1 can be supplied immediately before use, it is possible to use even a resin having a low viscosity, and the options of the viscosity are widened so that the wafer 1 can be brought closer to flatness. In such an embodiment, the present embodiment is particularly effective because it is necessary to press and spread the resin P1.

  That is, as shown in FIGS. 8A to 8B, when the resin P1 is supplied onto the workpiece placement surface 12a of the stage 12, a negative pressure is generated in the suction portion 24 of the pressing pad 23, and FIG. As shown in FIG. 3, the surface 1a of the wafer 1 is adsorbed on the adsorption surface 24a of the adsorption unit 24. In addition to waviness and warpage, the wafer 1 which has been deformed including the above-described deflection is brought into close contact with the suction surface 24a and the deformation is corrected, and is held on the pressing pad 23 in a flat state. Next, the pressing pad 23 is lowered to bring the flat back surface 1b of the wafer 1 into close contact with the resin P1, and further lowered to press the wafer 1 toward the resin P1 as shown in FIG. . Thereafter, the same operation as in the above embodiment is performed to form the resin film P2 on the back surface 1b of the wafer 1.

  Further, when the wafer 1 has a shape including warpage, the behavior of returning the warp while causing the resin P1 to flow after the correction is released occurs when the convex side of the warp is attracted to the suction portion 24 of the pressing pad 23. It is preferable because it is easy.

It is sectional drawing of the wafer by which resin is coat | covered by one side in one Embodiment of this invention. It is a perspective view of the resin coating apparatus which concerns on one Embodiment of this invention. It is sectional drawing which shows the resin coating process of one Embodiment. It is sectional drawing which shows the resin coating process (continuation of FIG. 3) of one Embodiment. It is sectional drawing which shows the resin coating process (continuation of FIG. 4) of one Embodiment. It is a side view showing a grinding device (grinding spindle) of one embodiment which grinds a wafer. It is sectional drawing which shows a grinding process. It is a perspective view which shows the resin coating process which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wafer (work), 1a ... Wafer surface (one surface), 1b ... Wafer back surface (other surface), 10 ... Resin coating apparatus, 12 ... Stage, 12a ... Workpiece mounting surface, 13 ... UV lamp (External stimulus applying means), 20 ... wafer holding means (work holding means, pressing means, work moving means), 23 ... pressing pad, P1 ... resin (resin before curing), P2 ... resin film (resin after curing) ).

Claims (5)

A resin coating method for coating a resin on the other surface of the workpiece in order to grind and flatten one surface of a thin plate-shaped workpiece including deformation elements such as waviness and warpage,
A workpiece placement step of placing the workpiece on the curable resin supplied in a predetermined amount in a lump state on the workpiece placement surface of the stage;
A workpiece pressing step of pressing the workpiece from the one surface side toward the massive resin by a pressing means;
A workpiece moving step of moving the workpiece in a direction from the other surface toward the one surface to at least a position corresponding to the deformation element while holding the workpiece on the pressing means;
A pressing means separating step for separating the pressing means from the one surface of the workpiece;
A resin coating method comprising at least a resin curing step of curing the resin by applying a stimulus to the curable resin by an external stimulus applying means. The curable resin is an ultraviolet curable resin that is cured by ultraviolet irradiation,
The resin coating method according to claim 1, wherein the external stimulus applying unit is an ultraviolet irradiation unit that irradiates ultraviolet rays. The curable resin is a thermosetting resin that cures when heated.
The resin coating method according to claim 1, wherein the external stimulus applying unit is a heating unit that performs heating. The curable resin is a thermoplastic resin that liquefies when heated and cures when cooled.
The resin coating method according to claim 1, wherein the external stimulus applying unit is a cooling unit that performs cooling. A resin coating apparatus for coating a resin on the other surface of the workpiece in order to grind and flatten one surface of a thin plate-shaped workpiece including deformation elements such as undulation and warpage,
Workpiece holding means for holding the workpiece detachably in a state where the other surface is exposed;
A stage having a workpiece placement surface disposed opposite to the workpiece holding means, and a predetermined amount of a block of curable resin is supplied to the workpiece placement surface;
A pressing means for pressing the workpiece toward the curable resin supplied in a predetermined amount in a lump state on the workpiece placement surface of the stage;
A workpiece moving means for moving the workpiece pressed toward the curable resin by the pressing means in a direction from the other surface toward the one surface;
A resin coating apparatus comprising at least an external stimulus applying means for applying an external stimulus to the curable resin supplied to the workpiece placement surface of the stage.

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