JP6730910B2 - Wafer resin coating method - Google Patents

Description

The present invention relates to a resin coating method for coating a resin on the surface of a wafer.

In the manufacturing process of a semiconductor device, grid-like planned dividing lines are formed on the surface of a silicon wafer or the like, and devices such as ICs and LSIs are formed in respective regions defined by the dividing lines. To manufacture individual semiconductor devices by grinding and polishing the back surface of the wafer thus formed to reduce the thickness of the wafer to a predetermined thickness, and then dividing the wafer with a cutting device or the like along a dividing line. You can

In recent years, as a technique for realizing the miniaturization of semiconductor devices, a plurality of metal projections called bumps are formed on the device surface, and these bumps are directly bonded to the electrodes formed on the wiring board so as to face each other. The mounting technology has been put to practical use. Then, among the wafers having bumps formed on their surfaces, there are some wafers on which thick bumps called high bumps are mounted. Conventionally, when grinding such a wafer, a protective tape is attached to the surface of the wafer on which devices and bumps are formed to protect the surface of the wafer. Then, the rotating grinding wheel is brought into contact with the wafer whose protective tape side is suction-held on the holding table to grind the back surface of the wafer.

However, because the thickness of the adhesive on the adhesive surface of the protective tape is insufficient for the thickness of the bumps, the wafer before grinding cannot be flattened by removing the bumps and bumps with the protective tape. Bump irregularities are transferred to the surface to be ground (back surface), variations in the thickness of the wafer after grinding become large, or the protective tape cannot keep up with the holding surface of the holding table and the vacuum in suction holding of the wafer by the holding table There was a problem such as a leak.

In order to solve such a problem, a thick protective tape for high bumps has been developed so that bump unevenness can be absorbed, but such a protective tape has a problem that the processing cost increases because it is expensive. .. Further, in order to prevent a vacuum leak, a holding table having a small vacuum area has been developed, but there is a problem that it takes time and money to replace such a holding table with a grinding device.

Therefore, in order to reduce costs, unevenness of high bumps is not transferred to the surface to be ground, the thickness variation of the wafer after grinding is reduced, and vacuum leak does not occur when holding the wafer on the holding table. There is a method of forming a resin film by coating the surface of a wafer with a resin that is cured by ultraviolet rays instead of a protective tape for grinding, and protecting the wafer with this resin film (for example, refer to Patent Document 1). ..

JP, 2013-175647, A

In the above method of coating a resin on a wafer, first, a predetermined amount of liquid resin is dropped onto the wafer to form a lump of liquid resin. The liquid resin has a property of being cured by light (typically, ultraviolet ray), for example. Then, the wafer whose back surface is suction-held by the holding table is pressed against the liquid resin from the upper side to spread the liquid resin, so that the entire front surface of the wafer is covered with the liquid resin. Next, the liquid resin is irradiated with ultraviolet rays to cure the liquid resin.

However, when covering the surface of a bumpy wafer such as a wafer with high bumps with liquid resin, the liquid resin does not fully reach the details of the unevenness, and the air between the liquid resin and the surface of the wafer is sufficiently filled with resin. In some cases, the liquid resin may be cured in a state where air bubbles enter between the resin and the surface of the wafer. The resin film cured in the state where air bubbles enter may not be able to sufficiently protect the surrounding bumps and devices in which air bubbles have entered, and the grinding pressure may cause damage or breakage of the bumps or damage to the device.

Therefore, when a liquid resin is coated on the surface of a wafer on which irregularities are formed by bumps or the like, it is possible to uniformly coat the surface of the wafer with the liquid resin while preventing bubbles from entering the liquid resin. There are challenges.

The present invention for solving the above problems is a resin coating method for covering the surface of a wafer with a resin, a wafer holding step of holding the wafer on a wafer table, and a resin installed so as to face the wafer table. Resin holding step for holding the resin on the wafer table, an approaching step for bringing the wafer table and the resin table close to each other to bring the wafer and the resin into contact with each other to spread the resin on the surface of the wafer, and to bring the wafer and the resin into contact with each other. A separating step of separating the wafer from the resin table in the kept state, and repeating the approaching step and the separating step to coat the surface of the wafer with the resin.

The inventor of the present application, as one of the causes of causing a situation where the liquid resin is cured in a state where air bubbles have entered between the resin and the surface of the wafer, when the liquid resin is spread on the wafer, When the liquid resin flowing between the resin table and the resin table is completely separated into two bodies, the air bubbles are generated at the apex portions of the respective resin bodies, and the air bubbles finally form the resin and the surface of the wafer. I found that I got in between. Therefore, in the resin coating method according to the present invention, the wafer table and the resin table are brought close to each other to bring the wafer and the resin into contact with each other to spread the resin on the surface of the wafer, and the wafer and the resin are brought into contact with each other. By providing a separation step that separates the wafer from the resin table in the state, the resin is spread on the wafer while repeating separation and approach without completely separating the wafer and the resin, and the liquid resin on the wafer. It is possible to coat the resin evenly on the wafer while preventing air bubbles from entering the resin when unfolding.

It is sectional drawing which shows the structure of a wafer. It is sectional drawing which shows the state which hold|maintained the wafer on the wafer table. It is sectional drawing which shows the state which has supplied resin to the resin table and is holding|maintaining resin by the resin table. FIG. 6 is a cross-sectional view showing a state in which the wafer table and the resin table are brought close to each other to bring the wafer and the resin into contact with each other to spread the resin on the wafer. FIG. 6 is a cross-sectional view showing a state where the wafer is separated from the resin table while the wafer and the resin are in contact with each other. FIG. 6 is a cross-sectional view showing a state in which the resin film is irradiated with ultraviolet rays to cure the resin film. FIG. 6 is a cross-sectional view of a wafer whose surface is protected by a resin film.

A semiconductor wafer W having a circular plate-like outer shape shown in FIG. 1 is made of a silicon wafer having a predetermined thickness (for example, 300 μm), and its surface Wa has a plurality of lattice-like shapes partitioned by a plurality of dividing lines. Devices such as ICs and LSIs are formed in the area. A plurality of bumps (projection electrodes) Wf are provided on the surface of this device, respectively. The bump Wf is formed to have a height of about 100 μm to 200 μm, for example. The back surface Wb of the wafer W is a surface to be ground when grinding is performed.
Hereinafter, each step of the resin coating method according to the present invention for covering the front surface Wa of the wafer W with resin will be described.

(1) Wafer Holding Step The wafer table 30 shown in FIG. 2 is a table capable of sucking and holding the wafer W. The wafer table 30 has, for example, a circular outer shape, and includes a suction unit 300 configured by a porous member or the like for suctioning the wafer W, and a frame body 301 supporting the suction unit 300. A suction hole 301a is formed through the center of the bottom of the frame 301 in the thickness direction (Z-axis direction), and the lower end of the suction hole 301a is a suction space 301b that extends between the frame 301 and the suction unit 300. It is in communication. A suction source 39 composed of a vacuum generator, a compressor and the like is connected to the suction hole 301a via a suction pipe, and is a holding surface which is an exposed surface of the suction section 300 and is flush with the lower surface of the frame 301. The surface 300a communicates with the suction source 39 via the suction space 301b, the suction hole 301a, and the suction pipe. Then, the wafer table 30 can suck and hold the wafer W on the holding surface 300a. The wafer table 30 can be moved in the horizontal direction and the vertical direction by the moving means 38.

In the wafer holding step, first, the wafer table 30 is positioned above the wafer W with the back surface Wb side facing upward so that the center of the wafer table 30 and the center of the wafer W substantially coincide with each other. .. Then, the wafer table 30 descends in the -Z direction by the moving means 38, and the holding surface 300a and the back surface Wb of the wafer W come into contact with each other. Further, the suction force generated by the suction of the suction source 39 is transmitted to the holding surface 300a through the suction pipe, the suction hole 301a, and the suction space 301b, and the wafer table 30 is held on the holding surface 300a. The back surface Wb of W is suction-held.

(2) Resin Holding Step The resin table 40 having a circular outer shape shown in FIG. 3 is formed of, for example, a transparent member such as glass that transmits ultraviolet rays, and has a flat holding surface 40a that communicates with a suction source (not shown). Equipped with. The resin table 40 faces the wafer table 30 when the wafer table 30 shown in FIG. 2 is positioned above. Then, as shown in FIG. 3, the resin table 40 is in a state where the protective sheet T formed into a circular shape having a diameter substantially the same as the wafer W or a diameter larger than the wafer W is suction-held on the holding surface 40a. .. The protective sheet T is made of, for example, a transparent synthetic resin film such as polyethylene terephthalate (PET), and plays a role of preventing the liquid resin J from adhering to the holding surface 40a of the resin table 40.

Above the resin table 40, a resin supply means 41 having a supply nozzle 410 for supplying the liquid resin J is positioned. As shown in FIG. 3, the resin supply means 41 includes a resin supply source 411 in which the liquid resin J is stored, and the liquid resin J stored in the resin supply source 411 is, for example, about 500 to 5000 mPa. It is a solventless curable resin having a viscosity of, and has the property of being cured by being irradiated with ultraviolet rays.

In the resin holding step, first, the supply nozzle 410 of the resin supply means 41 is positioned above the substantially central region of the protective sheet T that is suction-held on the resin table 40. Next, the resin supply source 411 sends out the liquid resin J toward the supply nozzle 410, and an appropriate amount of the liquid resin J is dripped from the supply nozzle 410 toward the holding surface 40a of the resin table 40, and the liquid resin J is applied to the central region on the protective sheet T. Liquid resin J is supplied. The liquid resin J having a certain degree of viscosity maintains a substantially hemispherical shape on the protective sheet T, and the resin table 40 holds the liquid resin J via the protective sheet T. When a suitable amount of the liquid resin J is deposited on the upper surface of the protective sheet T, the resin supply unit 41 stops the supply of the liquid resin J, and the resin supply unit 41 retreats from above the resin table 40.

(3) Approaching Step After the resin holding step is completed, the moving means 38 shown in FIG. 4 moves the wafer table 30 that sucks and holds the wafer W so that the center of the wafer W and the center of the protective sheet T are substantially aligned. The wafer W is positioned so that the front surface Wa of the wafer W faces the liquid resin J on the protective sheet T.

As the moving means 38 lowers the wafer table 30 in the −Z direction, the wafer table 30 and the resin table 40 approach each other, and the tops of the bumps Wf of the wafer W and the liquid resin J are separated from each other in FIG. It contacts at the height position Z0 shown in. When the wafer table 30 is further lowered in the −Z direction by the moving means 38, the liquid resin J on the protective sheet T is pressed by the wafer W, and the liquid resin J is radially outward on the front surface Wa of the wafer W. It spreads toward. Then, for example, the wafer table 30 holding the wafer W is lowered to the height position Z1 where the liquid resin J is sufficiently pushed to the root of the bump Wf of the wafer W, and the liquid resin J on the protective sheet T is transferred to the wafer W. Is spread over the surface Wa.

(4) Separation Step For example, as shown in FIG. 5, after the wafer table 30 holding the wafer W is lowered to a height position Z1 at which the liquid resin J is sufficiently pushed to the root of the bump Wf of the wafer W, The moving means 38 raises the wafer table 30 in the +Z direction to separate the wafer W from the resin table 40. The liquid resin J in a state of being adhered to both the front surface Wa of the wafer W and the upper surface of the protective sheet T is, for example, in the expansion/contraction direction (Z-axis direction) between the front surface Wa of the wafer W and the upper surface of the protective sheet T. ) While being gradually flown while keeping the shape of the truncated cone curved so that the outer diameter of the middle portion of the above) is reduced, the wafer W ascending is extended in the +Z direction. In this way, the moving means while maintaining the state where the front surface Wa of the wafer W and the liquid resin J are in contact with each other, that is, the state where the liquid resin J between the front surface Wa of the wafer W and the upper surface of the protective sheet T is not divided. 38 raises the wafer table 30 in the +Z direction. Then, for example, the moving means 38 raises the wafer table 30 in the +Z direction until the apex of the bump Wf of the wafer W is located at a height position Z2 which is about the midpoint between the height position Z0 and the height position Z1. ..

For example, after the apex of the bump Wf of the wafer W reaches the height position Z2 which is about the midpoint between the height position Z0 and the height position Z1, the approach step is performed again, and the apex of the bump Wf of the wafer W is raised. The moving means 38 lowers the wafer table 30 holding the wafer W to reach a height position Z3 that is a predetermined distance below the height position Z1, and the liquid resin J on the protective sheet T is transferred onto the surface of the wafer W. Push it further to Wa. Then, the separating step is performed again, and the moving means 38 raises the wafer table 30 in the +Z direction while maintaining the state in which the liquid resin J between the front surface Wa of the wafer W and the upper surface of the protective sheet T is not divided. Then, for example, the moving means 38 raises the wafer table 30 in the +Z direction until the apex of the bump Wf of the wafer W reaches the height position Z4 which is about the middle of the height position Z2 and the height position Z3. By thus repeating the approaching step and the separating step a plurality of times (for example, 4 to 7 times), while maintaining the state in which the liquid resin J between the front surface Wa of the wafer W and the upper surface of the protective sheet T is not divided, The liquid resin J on the protective sheet T is spread over the front surface Wa of the wafer W, and the height position of the wafer W when the wafer is pressed in the approaching step is gradually lowered.

As shown in FIG. 6, by repeating the approaching step and the separating step a plurality of times, the entire surface Wa of the wafer W is covered with the liquid resin J, and after the resin film J1 for eliminating the unevenness of the bumps Wf is formed, The vertical movement of the wafer table 30 by the moving means 38 is stopped. Then, for example, the resin film J1 is irradiated with ultraviolet rays to cure the resin film J1. In the resin coating method according to the present application, as described above, the wafer table 30 and the resin table 40 are brought close to each other to bring the wafer W and the liquid resin J into contact with each other and to spread the liquid resin J onto the surface Wa of the wafer W. , A separation step of separating the wafer W from the resin table 40 in a state where the wafer W and the liquid resin J are in contact with each other, and thus the separation and the approach are repeated without completely separating the wafer W and the liquid resin J. However, since the liquid resin J is pushed and spread on the wafer W, the top portion of the liquid resin J when the liquid resin J that expands and contracts between the wafer W and the resin table 40 is completely separated into two bodies (separated It is possible to cure the resin film J1 in a state where no bubbles are generated in the resin film J1 that uniformly covers the entire surface Wa of the wafer W without generating bubbles at the tip of the portion).

For example, as shown in FIG. 6, a resin curing unit 70 for curing the liquid resin J is disposed below the resin table 40, and the resin curing unit 70 includes a plurality of UV lamps 700 that emit ultraviolet light. I have it. For example, the ultraviolet light emitted from the resin curing unit 70 in the +Z direction passes through the transparent resin table 40 and the protective sheet T and is applied to the resin film J1. As a result, the resin film J1 is cured, and the resin film J1 that covers and protects the front surface Wa of the wafer W is formed.

Then, for example, the suction by a suction source (not shown) is stopped, the suction holding of the protective sheet T by the resin table 40 is released, and the moving means 38 raises the wafer table 30 in the +Z direction to move the wafer W to the resin table. 40, and the protective sheet T is exposed downward. Further, the protective sheet T is sandwiched by the sandwiching means composed of a clamp or the like of a stripping device (not shown), and the sandwiching means is moved to strip the protective sheet T from the wafer W. As shown in FIG. It is possible to manufacture a wafer W in which the back surface Wb can be ground by being protected by the resin film J1.

The resin coating method according to the present invention is not limited to the above embodiment, and the configurations of the wafer table 30 and the resin table 40 illustrated in the accompanying drawings are not limited to this. However, it can be appropriately changed within a range in which the effects of the present invention can be exhibited. For example, the liquid resin J of the above-described embodiment is an ultraviolet curable resin that is cured by ultraviolet rays, but is not limited to this. For example, a thermosetting resin that is cured by heating may be used. In that case, a heating means is used instead of the resin curing means 70.

W: Wafer Wa: Wafer front surface Wb: Wafer back surface Wf: Bump 30: Wafer table 300: Adsorption part 300a: Holding surface 301: Frame body 301a: Suction hole 301b: Suction space 38: Moving means 39: Suction source 40 : Resin table 40a: Holding surface 41: Resin supply means 410: Supply nozzle 411: Resin supply source
70: Resin curing means 700: UV lamp T: Protective sheet J: Liquid resin J1: Resin film

Claims (1)

A resin coating method for covering the surface of a wafer with a resin,
A wafer holding step of holding the wafer on the wafer table,
A resin holding step of holding resin on a resin table installed so as to face the wafer table,
An approaching step of bringing the wafer table and the resin table close to each other to bring the wafer and the resin into contact with each other and spread the resin on the surface of the wafer;
A separation step of separating the wafer from the resin table in a state where the wafer and the resin are in contact with each other,
A resin coating method comprising repeating the approaching step and the separating step to coat the surface of the wafer with a resin.

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