JP6411142B2 - Protective coating method - Google Patents

Description

  The present invention relates to a method for coating a protective film that covers the surface of a wafer, and more particularly, to a method for coating a protective film that covers a wafer on which convex portions such as bumps are formed.

  In a laser processing apparatus that divides a semiconductor wafer or optical device wafer (hereinafter simply referred to as a wafer) by irradiating a laser beam along the division line, when the laser beam is irradiated on the wafer surface, the melted material starts from the irradiated area. As debris occurs. In order to prevent the debris from reattaching to the surface of the wafer, a method of covering the surface of the wafer with a protective film such as a liquid resin has been proposed (see, for example, Patent Document 1). As a specific method of coating the protective coating, a so-called spin coating method has been proposed in which a predetermined amount of liquid resin is dropped onto the center of a wafer held on a rotary table and the rotary table is rotated at a predetermined speed. (See Patent Document 2 to Patent Document 4). Furthermore, in order to make the film thickness of the protective film uniform, a method of performing spin coating a plurality of times has been proposed (see Patent Document 3 and Patent Document 4).

JP 2004-188475 A JP 2006-198450 A JP 2008-006379 A JP 2014-060269 A

  By the way, when bumps or other convex parts are formed on the device on the surface of the wafer, the rotary table holding the wafer may be rotated, and the centrifugal force may cause the liquid resin to flow toward the outer periphery. It was difficult to uniformly apply the liquid resin to the surface of the wafer, hindered by the convex portions on the surface. When the thickness of the protective coating is not uniform, the protective effect against debris is reduced in the thin portion of the protective coating, and the debris attached to the thin portion of the protective coating may affect the wafer. In addition, as shown in Patent Document 3 and Patent Document 4, it may be possible to perform spin coating a plurality of times. However, since the liquid resin is a water-soluble resin, the liquid resin is once dried and then applied again. Even so, the protective film first coated melts, and the protective film cannot always be formed uniformly.

  This invention is made | formed in view of this point, and it aims at providing the coating method of the protective film which can form a protective film uniformly on the surface of a wafer irrespective of the surface shape of a wafer.

The method for coating a protective coating of the present invention is a coating method for forming a protective coating on the surface of a plate-like wafer with a resin, and has a viscosity that is water-soluble and does not flow out of the wafer from the surface. A resin sheet mounting process that covers the entire surface with a film-shaped resin sheet containing a gel-shaped protective resin, and a protective resin by spraying air toward the resin sheet that covers the entire surface in the resin sheet mounting process It consists of the sticking process which sticks to the surface and sticks a resin sheet, and the hardening process which hardens the protective resin which passed through the sticking process.

  According to this configuration, after the resin sheet is placed on the surface of the wafer, the resin sheet is closely adhered to the entire surface of the wafer, thereby forming a protective film on the surface of the wafer according to the thickness of the resin sheet. Can do. Therefore, a protective film having a uniform thickness can be formed over the entire surface of the wafer regardless of the surface shape of the wafer, for example, even a wafer having convex portions such as bumps formed on the surface.

  According to the present invention, the protective film can be uniformly formed on the surface of the wafer regardless of the surface shape of the wafer by bringing the resin sheet constituting the protective film into close contact with the surface of the wafer.

It is a figure which shows an example of the wafer to which the coating method of the protective film which concerns on this Embodiment is applied. It is a figure which shows an example of the resin sheet used for the coating method of the protective film which concerns on this Embodiment. It is a schematic diagram of the protective film formation apparatus applied to the coating method of the protective film which concerns on this Embodiment. It is a figure which shows an example of the resin sheet mounting process which concerns on this Embodiment. It is a figure which shows an example of the sticking process which concerns on this Embodiment. It is a figure which shows an example of the hardening process which concerns on this Embodiment. It is a figure which shows the sticking process which concerns on a 1st modification. It is a figure which shows the sticking process which concerns on a 2nd modification.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing an example of a wafer to which the protective coating method according to the present embodiment is applied. FIG. 2 is a diagram illustrating an example of a resin sheet used in the protective film coating method according to the present embodiment. FIG. 3 is a schematic view of a protective film forming apparatus applied to the protective film coating method according to the present embodiment. In the present embodiment, an example in which the protective film forming apparatus is applied to a laser processing apparatus will be described. In addition, the protective film formation apparatus which concerns on this Embodiment is not limited to the structure shown below, A change is possible suitably. The protective film forming apparatus may be configured in any way as long as it is configured to adhere a resin sheet to the surface of the wafer and form a protective film on the surface of the wafer.

  First, a wafer applied to the present embodiment will be described. As shown in FIG. 1, the wafer W has a circular shape, and the surface of the wafer W is divided into a plurality of device regions by division lines (not shown) arranged in a lattice pattern. In each device region, a plurality of hemispherical convex portions B such as bumps are formed. The wafer W is held by the ring frame F via a holding tape T attached to the back side with the front side facing up. The wafer W is not limited to a semiconductor wafer such as a silicon wafer or a gallium fin, but may be a package substrate, glass, or a sapphire inorganic material substrate. Further, the convex portions B formed on the surface of the wafer W are not limited to bumps. For example, the surface of the optical device formed on the alumina ceramic substrate may be protected with a silicone resin, and a plurality of convex portions B may be provided on the surface of the silicone resin. Moreover, the convex part B does not necessarily need to be formed.

  By the way, when forming a protective film on the surface of the wafer W mentioned above, generally spin coating is employ | adopted. In spin coating, a liquid resin is dropped on the center of the surface of the wafer W, and the holding table that holds the wafer W is rotated at a high speed. Thereby, centrifugal force is generated in the liquid resin, and the liquid resin is diffused from the center of the wafer W toward the outer periphery. As a result, the liquid resin is applied to the entire surface of the wafer W. However, in the spin coating, a large amount of liquid resin (more specifically, about 90% of the liquid resin dropped on the center of the surface of the wafer W) is blown off and blown away by the high-speed rotation of the holding table 2. The liquid resin was discarded. Thus, in the formation of the protective film by spin coating, saving of the liquid resin has been a problem.

  Therefore, the applicant of the present application attaches a resin sheet 10 (see FIG. 2) conforming to the shape of the wafer W to the surface of the wafer W, and attaches the protective resin 12 (see FIG. 2) constituting the protective coating to the surface of the wafer W. I came up with the idea of transcribing. Thereby, the protective film according to the thickness of the resin sheet 10 (protective resin 12) can be formed, and a protective film having a uniform thickness can be formed over the entire surface of the wafer W regardless of the surface shape of the wafer W. it can. Moreover, by using the resin sheet 10 matched to the shape of the wafer W, the protective coating can be formed with the minimum amount of the protective resin 12, and the protective resin 12 can be saved. Hereinafter, the resin sheet used for the coating method of the protective film which concerns on this Embodiment is demonstrated.

  As shown in FIG. 2, the resin sheet 10 is formed by applying a gel-like protective resin 12 to the surface of a release sheet 11 formed in a circular shape having the same diameter as the wafer W, and is formed in a film shape. The The resin sheet 10 is adhered (adhered) to the surface of the wafer W and then dried to form a protective film over the entire surface of the wafer W. The release sheet 11 is made of a synthetic resin film such as polyethylene terephthalate (PET). As the protective resin 12, a water-soluble or thermoplastic resin such as polyvinyl alcohol (PVA) or polyethylene glycol (PEG) is used. The gel-like protective resin 12 preferably has such a viscosity that it does not flow out from the surface of the wafer W to the outside of the wafer W after being in close contact with the surface of the wafer W.

  The protective resin 12 is preferably added with an absorbent that absorbs light having a laser wavelength. As a result, the protective coating is removed at the same time as the processing of the wafer W during laser processing, so that the protective coating is prevented from peeling off from the surface of the wafer W due to the vapor of the thermal decomposition product of the wafer W. In addition, the resin sheet 10 is not limited to the above-described configuration, and may be configured in any manner as long as it is attached to the surface of the wafer W to form a protective film. For example, the protective resin 12 may be made of a thermoplastic resin film or a water-soluble resin film. In this case, the release sheet 11 is not necessarily provided.

  Next, the protective film forming apparatus according to the present embodiment will be described. As shown in FIG. 3, the protective film forming apparatus 1 is mounted on the upper surface of the holding table 2, and a resin sheet 10 (see FIG. 2) is attached to the surface of the wafer W held by a plurality of clamping means 3. Configured to do. The holding table 2 is formed in a disc shape, and a holding surface for sucking and holding the wafer W is formed on the upper surface of the holding table 2. The holding surface is formed of a porous member such as porous ceramic, and the holding surface is connected to a suction source (not shown). The wafer W placed on the holding table 2 is sucked and held by the negative pressure generated on the holding surface. Further, the upper end portion of the drive shaft 21 of the electric motor 20 is fixed to the center of the lower surface of the holding table 2. Accordingly, the holding table 2 is configured to be rotatable by receiving the rotational force of the electric motor 20.

  In addition, a plurality of (for example, four) clamp means 3 are provided on the outer periphery of the holding table 2 at regular intervals in the circumferential direction of the holding table 2. The clamp means 3 is configured to clamp the upper and lower surfaces of the ring frame F, and is configured by attaching a clamp mechanism 31 to an arm 30 protruding from the outer peripheral surface of the holding table 2. The clamp mechanism 31 includes a columnar drive mechanism 32 having a rotation shaft (not shown) in the circumferential direction (horizontal direction) of the holding table 2, and a fixed support portion 33 that supports the lower surface (holding tape T) of the ring frame F. , And a movable support portion 34 that supports the upper surface of the ring frame F.

  The drive mechanism 32 is composed of, for example, an air-driven rotary actuator. The fixed support portion 33 is formed of a long body extending in the horizontal direction. The fixed support portions 33 are attached to the both side surfaces of the drive mechanism 32 one by one so that the tip portions protrude from the holding table 2 in the radial direction (from the outer peripheral surface of the drive mechanism 32). The movable support portion 34 is formed in an L shape in a side view, and one end is fixed to the rotation shaft of the drive mechanism 32. The movable support portion 34 is retracted by retreating from the fixed support portion 33 and a holding position where the ring frame F is held (a position where the front end of the fixed support portion 33 and the front end of the movable support portion 34 face each other). It can be opened and closed between positions. Thus, the clamp mechanism 31 can clamp the ring frame F (wafer W) between the fixed support portion 33 and the movable support portion 34.

  In addition, a mounting means 4 for mounting the resin sheet 10 on the surface of the wafer W is provided above the holding table 2. The placing means 4 includes a resin sheet holding means 40 that holds and holds one end of the resin sheet 10 and a moving means 41 that moves the resin sheet holding means 40 in the horizontal direction. The moving means 41 includes a guide rail 42 that extends in the horizontal direction above the holding table 2 and a moving block 43 that can move along the guide rail 42. The moving block 43 is moved in the horizontal direction along the guide rail 42 by driving a driving mechanism (not shown).

  The resin sheet holding means 40 is configured by providing a pair of holding claws 45 a and 45 b extending in the horizontal direction at the tip of an arm portion 44 that extends downward from the moving block 43. The arm 30 is configured to be extendable in the vertical direction. The pair of holding claws 45 a and 45 b are provided so as to face each other vertically, and the lower holding claw 45 a is fixed to the arm portion 44. The upper holding claw 45b is configured to be movable up and down, and by holding the upper holding claw 45b closer to the lower holding claw 45a, it is possible to grasp and hold one end of the resin sheet 10. Become. In the mounting means 4, the resin sheet 10 can be placed at a predetermined position on the surface of the wafer W by expanding and contracting the arm portion 44 while horizontally moving the resin sheet holding means 40 while holding the resin sheet 10. it can. The operation of the mounting means 4 will be described later.

  Moreover, although mentioned later for details, the protective film formation apparatus 1 has the air injection nozzle 5 which injects air toward the wafer W after the resin sheet 10 is mounted (refer FIG. 5). By spraying air toward the wafer W (resin sheet 10), the protective resin 12 (see FIG. 2) of the resin sheet 10 is brought into close contact with the surface of the wafer W.

  In the protective film forming apparatus 1 configured as described above, the resin sheet 10 is placed on the surface of the wafer W held on the holding table 2 by the placing means 4. After the resin sheet 10 is placed, air is jetted toward the resin sheet 10. As a result, the protective resin 12 of the resin sheet 10 adheres to the surface of the wafer W, and the resin sheet 10 is adhered to the wafer W. After the resin sheet 10 is adhered, the protective sheet 12 constituting the protective film is transferred to the surface of the wafer W by peeling off the release sheet 11. Then, by rotating the holding table 2, the protective resin is dried and cured. As described above, a protective coating corresponding to the thickness of the resin sheet 10 (protective resin 12) can be formed on the surface of the wafer W. Thus, by covering the surface of the wafer W with the protective film, it is possible to prevent debris generated by laser processing from adhering to the surface of the wafer W.

  Next, with reference to FIG. 4 to FIG. 6, a method for coating a protective film according to the present embodiment will be described. FIG. 4 is a diagram illustrating an example of a resin sheet placement process according to the present embodiment. In FIG. 4, for convenience of explanation, the right side of the paper is the one end side of the resin sheet (including the wafer and the holding table), and the left side of the paper is the other end side of the resin sheet. FIG. 5 is a diagram illustrating an example of a sticking process according to the present embodiment. FIG. 6 is a diagram illustrating an example of a curing process according to the present embodiment. The protective film coating method according to the present embodiment includes a resin sheet placement step of placing a resin sheet on the surface of the wafer to cover the entire surface of the wafer, and an adhesion step of adhering the resin sheet to the surface of the wafer. And a curing step for curing the resin sheet (protective resin). Hereinafter, each process of the coating method of the protective film which concerns on this Embodiment is demonstrated.

  As shown in FIG. 4, first, a resin sheet placing step is performed. The wafer W is sucked and held on the holding surface of the holding table 2 with the convex portion B facing upward and supported by the ring frame F via the holding tape T. At this time, a part of the ring frame F and the holding tape T is sandwiched between the fixed support portion 33 and the movable support portion 34. In the mounting means 4, one end side of the resin sheet 10 is held by the resin sheet holding means 40. Further, the horizontal position of the resin sheet holding means 40 and the height positions of the pair of holding claws 45 (arm portions 44) so that the other end side of the resin sheet 10 is located on the other end side of the wafer W (holding table 2). Is adjusted).

  The placing means 4 brings the other end of the resin sheet 10 into contact with the other end of the wafer W, and then lowers the height position of the pair of holding claws 45 while holding one end of the resin sheet 10 (arm portion 44). The moving block 43 is moved from the other end side toward the one end side along the guide rail 42. Thereby, the center of the resin sheet 10 and the center of the wafer W are aligned, and the resin sheet 10 is placed on the surface of the wafer W with the protective resin 12 facing downward. In the state shown in FIG. 4, the surface of the protective resin 12 is in contact with the apex of the convex portion B, and a gap is generated between the protective resin 12 and the wafer W by the height of the convex portion B.

  Next, a sticking process is implemented. First, the configuration necessary for the sticking process will be described. As shown in FIG. 5, an air injection nozzle 5 that injects air toward the resin sheet 10 is provided above the wafer W. The air injection nozzle 5 is connected to an air supply source 50. The air injection nozzle 5 is formed in a substantially L shape above the outer peripheral side of the holding table 2 by a vertical portion 5a extending in the vertical direction and a horizontal portion 5b extending in the horizontal direction from the lower end of the vertical portion 5a. The tip of the horizontal portion 5b is bent downward, and air is jetted from the bent tip portion toward the resin sheet 10. A rotation motor 51 is provided at the upper end of the vertical portion 5a. By driving the rotary motor 51, the air injection nozzle 5 is swung around the vertical portion 5a above the wafer W.

  In the sticking step, air is jetted over the entire area of the wafer W while the air jet nozzle 5 is swung. Thereby, the resin sheet 10 is pressed toward the wafer W by the air injection force. As a result, the gel-like protective resin 12 adheres (sticks) to the surface of the wafer W without a gap while slightly deforming the convex portion B following the shape. Then, the protective resin 12 is transferred to the surface of the wafer W by peeling off the release sheet 11. Note that the release sheet 11 may not be peeled off.

  Next, a curing step is performed. As shown in FIG. 6, in the curing process, the protective resin 12 is cured by rotating the holding table 2. Thereby, a protective coating corresponding to the thickness of the protective resin 12 is formed on the surface of the wafer W. Further, the protective resin 12 may be dried by blowing air to the protective resin 12 by the fan 6 provided above the wafer W.

  As described above, according to the method for coating a protective film according to the present embodiment, after the resin sheet 10 is placed on the surface of the wafer W, the resin sheet 10 is adhered to the entire surface of the wafer W. A protective coating corresponding to the thickness of the resin sheet 10 (protective resin 12) can be formed on the surface of the wafer W. Therefore, regardless of the surface shape of the wafer W, for example, even when the wafer W has bumps or other convex portions formed on the surface, a protective film having a uniform thickness can be formed on the entire surface of the wafer W. Moreover, by using the resin sheet 10 matched to the shape of the wafer W, the protective coating can be formed with the minimum amount of the protective resin 12, and the protective resin 12 can be saved.

  Next, with reference to FIG. 7, the sticking process which concerns on a 1st modification is demonstrated. FIG. 7 is a diagram showing an attaching process according to the first modification. The first modification is different from the present embodiment in that the resin sheet (protective resin) is brought into close contact with the wafer using the thermoplasticity. In the following description, components having the same name are denoted by the same reference numerals.

  As shown in FIG. 7, a heater 7 is provided above the holding table 2 so as to cover the entire surface of the wafer W. In addition, the resin sheet 10 according to the first modification is configured by only the film-like protective resin 12 without including a release sheet. In the sticking process according to the first modification, the resin sheet 10 (protective resin 12) is heated by the heater 7 generating heat. Since the protective resin 12 has thermoplasticity, it melts when heated. As a result, the protective resin 12 adheres (sticks) to the surface of the wafer W without a gap while slightly deforming the convex portion B following the shape. And a protective film is formed by implementing a hardening process similarly to this Embodiment. Thus, also in the 1st modification, the protective film according to the thickness of the resin sheet 10 (protective resin 12) can be formed on the surface of the wafer W.

  Also, the following modifications are possible. With reference to FIG. 8, the sticking process which concerns on a 2nd modification is demonstrated. FIG. 8 is a diagram illustrating an attaching process according to a second modification. The second modification is different from the present embodiment in that the resin sheet (protective resin) is brought into close contact with the wafer using the water solubility.

  As shown in FIG. 8, above the holding table 2, a water injection nozzle 8 that injects water toward the surface of the wafer W (resin sheet 10) is provided. Similarly to the first modification, the resin sheet 10 according to the second modification is configured by only the film-like protective resin 12 without including the release sheet. In the sticking step according to the second modification, water is jetted from the water jet nozzle 8 over the entire area of the resin sheet 10. Since the protective resin 12 is a water-soluble resin, it has fluidity by absorbing the injected water. Thereby, the protective resin 12 adheres (sticks) to the surface of the wafer W without a gap while flowing along the convex portion B in conformity with the shape. And a protective film is formed by implementing a hardening process similarly to this Embodiment. Thus, also in the 2nd modification, the protective film according to the thickness of the resin sheet 10 (protective resin 12) can be formed on the surface of the wafer W.

  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 embodiment, the placing means 4 is configured to place the resin sheet 10 on the surface of the wafer W by grasping one end of the resin sheet 10 and sliding it in the horizontal direction. Not. The placing means 4 may be configured in any way as long as the resin sheet 10 can be placed on the surface of the wafer W. For example, the release sheet is sucked and held by the suction table with the release sheet side of the resin sheet 10 facing upward, the suction table is positioned above the wafer W, and then the suction table is lowered to dispose the protective resin 12 on the wafer W. You may make it contact the surface of. In this case, the resin sheet 10 can be placed on the surface of the wafer W by releasing the suction holding of the resin sheet 10.

  Moreover, in the said embodiment, although it was set as the structure which implements a resin sheet mounting process and a sticking process separately, it is not limited to this structure. For example, the resin sheet 10 is formed in a roll shape, and the resin sheet 10 is fed to the surface of the wafer W by a feed roller, and the resin sheet 10 is pressed toward the surface of the wafer W by a pressing roller provided above the wafer W. May be. In this case, the resin sheet placing step and the sticking step can be performed at the same time, and the covering method of the protective film can be simplified.

  In the above-described embodiment, the method for coating the protective film is configured to be performed by the protective film forming apparatus 1, but is not limited to this configuration. The method for coating the protective film may be performed by an operator.

  As described above, the present invention has an effect that a protective film can be uniformly formed on the surface of the wafer regardless of the surface shape of the wafer, and in particular, convex portions such as bumps are formed on the surface. This is useful for a method of coating a protective coating for coating a wafer.

W Wafer 10 Resin sheet

Claims (3)

A method of coating a protective film, which forms a protective film on the surface of a plate-shaped wafer with resin,
A resin sheet mounting step in which the protective resin covers the entire surface of the surface with a film-like resin sheet containing a gel-like protective resin having a water-soluble and viscosity that does not flow out of the wafer from the surface ;
A sticking step of sticking the resin sheet by injecting air toward the resin sheet covering the entire surface of the resin sheet in the resin sheet placing step to closely adhere the protective resin to the surface;
A curing step of curing the protective resin that has undergone the sticking step; A method of coating a protective film, which forms a protective film on the surface of a plate-shaped wafer with resin,
A resin sheet placing step in which the protective resin covers the entire surface of the surface with a film-like resin sheet containing a water-soluble and thermoplastic protective resin;
A sticking step of sticking the resin sheet in close contact with the surface by heating the resin sheet covering the entire surface of the resin sheet placing step and melting the protective resin;
A curing step of curing the protective resin that has undergone the sticking step; The resin sheet is configured by applying the protective resin to a release sheet that matches the shape of the wafer,
In the resin sheet placing step, the resin sheet is placed with the protective resin facing the wafer side,
In the sticking step, the protective resin is brought into close contact with the surface by being pressed toward the wafer by an air jet force through the release sheet, and then transferred to the surface by peeling the release sheet. The covering method of the protective film of Claim 1 characterized by the above-mentioned.

Images