TWI663045B - Coating method for protecting film - Google Patents

Abstract

The subject of the present invention is to uniformly form a protective coating on the surface of a wafer regardless of the surface shape of the wafer. The solution is to constitute a coating method of the protective film by a resin sheet placing step, an attaching step, and a curing step, and form a protective film corresponding to the thickness of the resin sheet on the surface of the wafer. The resin sheet mounting step is to cover the entire surface area of the wafer with a thin-film resin sheet. The attaching step is to closely contact the resin sheet that has covered the entire surface area of the wafer in the resin sheet mounting step. A resin sheet is attached on the surface, and this hardening step is to harden the resin sheet that has passed through the attaching step.

Description

Coating method for protecting film Field of invention

The present invention relates to a coating method for a protective film covering a surface of a wafer, and more particularly to a coating method for a protective film coating a wafer having a convex portion such as a bump formed on a surface thereof.

Background of the invention

In a laser processing device that irradiates laser light along a predetermined division line to divide a semiconductor wafer or an optical element wafer (hereinafter simply referred to as a wafer), an area to be irradiated with the laser light after being irradiated onto the wafer surface Fragments will appear as a melt. In order to prevent this debris from adhering to the surface of the wafer again, a method has been proposed in which a protective film such as a liquid resin is coated on the surface of the wafer (see, for example, Patent Document 1). In addition, among specific coating methods for protecting a film, a method called spin coating has been proposed, which is a method in which a predetermined amount of a liquid resin is dropped on a center portion of a wafer held on a rotary table. And rotate the turntable at a predetermined speed (see Patent Documents 2 to 4). In addition, 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 Documents 3 and 4).

Prior art literature Patent literature

Patent Document 1: Japanese Patent Laid-Open No. 2004-188475

Patent Document 2: Japanese Patent Laid-Open No. 2006-198450

Patent Document 3: Japanese Patent Laid-Open No. 2008-006379

Patent Document 4: Japanese Patent Laid-Open No. 2014-060269

Summary of invention

However, when convex parts such as bumps are formed on the elements on the surface of the wafer, even if the rotary table holding the wafer is rotated, the liquid resin is caused to flow toward the outer peripheral part by its centrifugal force. As a result, it is difficult to uniformly apply the liquid resin on the surface of the wafer. When the film thickness of the protective film is not uniform, there is a concern that the protection effect of the fragments on the thinner part of the protective film becomes smaller, and the chips attached to the thinner part of the protective film may have an influence on the wafer. Further, as shown in Patent Documents 3 and 4, although a method of performing spin-coating several times is also considered, since the liquid resin is a water-soluble resin, the liquid resin is applied even after the liquid resin is dried. Resin will still cause the initially covered protective film to dissolve, and the protective film may not necessarily be uniformly formed.

The present invention has been made in view of the problems described above, and an object thereof is to provide a coating method for a protective film that can uniformly form a protective film on the surface of a wafer regardless of the surface shape of the wafer.

The method for covering the protective film of the present invention is to form a resin in a plate shape. A coating method for forming a protective film on the surface of a wafer is characterized in that it is composed of the following steps: a resin sheet mounting step, covering the entire surface of the surface with a thin-film resin sheet; and an attaching step, In the resin sheet placing step, the resin sheet covering the entire surface of the surface is closely adhered to the surface to attach the resin sheet; and the hardening step is performed to harden the resin sheet that has passed through the attaching step.

According to this configuration, after placing the resin sheet on the surface of the wafer, the resin sheet can be closely adhered to the entire surface area of the wafer to form a protective film corresponding to the thickness of the resin sheet on the surface of the wafer. Accordingly, regardless of the surface shape of the wafer, for example, even a wafer having convex portions such as bumps formed on the surface, a protective film having a uniform thickness can be formed over the entire surface area of the wafer.

According to the present invention, by making the resin sheet constituting the protective film adhere to the surface of the wafer, the protective film can be uniformly formed on the surface of the wafer regardless of the shape of the surface of the wafer.

1‧‧‧ Protective film forming device

10‧‧‧ resin sheet

11‧‧‧ peeling sheet

12‧‧‧Protective resin

2‧‧‧ holding station

20‧‧‧ Electric motor

21‧‧‧Drive shaft

3‧‧‧ clamping means

30‧‧‧arm

31‧‧‧Clamping mechanism

32‧‧‧Drive mechanism

33‧‧‧Fixed support

34‧‧‧ movable support

4‧‧‧ placement means

40‧‧‧Resin sheet holding means

41‧‧‧Movement

42‧‧‧rail

43‧‧‧moving blocks

44‧‧‧ Arm

45, 45a, 45b ‧‧‧ holding claws

5‧‧‧air jet nozzle

50‧‧‧Air supply source

5a‧‧‧Vertical

5b‧‧‧Horizontal

51‧‧‧rotating motor

6‧‧‧fan

7‧‧‧ heater

8‧‧‧ water jet nozzle

B‧‧‧ convex

F‧‧‧Ring frame

T‧‧‧holding tape

W‧‧‧ Wafer

FIG. 1 is a diagram showing an example of a wafer to which a protective film coating method according to this embodiment is applied.

FIG. 2 is a diagram showing an example of a resin sheet used in the method for coating a protective film according to the embodiment.

FIG. 3 is a schematic diagram of a protective film forming apparatus applied to a method for coating a protective film according to this embodiment.

FIG. 4 is a diagram showing an example of a resin sheet placing step in the present embodiment.

FIG. 5 is a diagram showing an example of a sticking procedure in the present embodiment.

FIG. 6 is a diagram showing an example of a curing step in the present embodiment.

FIG. 7 is a diagram showing a sticking procedure according to a first modification.

FIG. 8 is a diagram illustrating a step of attaching a second modification.

Forms used to implement the invention

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram showing an example of a wafer to which a protective film coating method according to this embodiment is applied. FIG. 2 is a diagram showing an example of a resin sheet used in the method for coating a protective film according to the embodiment. FIG. 3 is a schematic diagram of a protective film forming apparatus applied to the method for coating a protective film according to this embodiment. In this embodiment, an example in which a protective film forming apparatus is applied to a laser processing apparatus will be described. In addition, the protective-film-forming-apparatus of this embodiment is not limited to the structure shown below, and can be changed suitably. The protective film forming device may be configured in any manner as long as it has a configuration in which a resin sheet can be attached to the surface of the wafer and a protective film is formed on the surface of the wafer.

First, a wafer applied to this 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 element regions by predetermined division lines (not shown) arranged in a grid shape. Hemispherical protrusions B such as a plurality of bumps are formed in each element region. The wafer W is held on the ring frame F with the surface facing upward, and is held by the holding tape T attached to the back side. Furthermore, the wafer W is not limited to semiconductors such as silicon wafers and gallium arsenide. The bulk wafer may also be a package substrate, glass, or a sapphire-based inorganic material substrate. The convex portion B formed on the surface of the wafer W is not limited to a bump. For example, a configuration may be adopted in which the surface of the optical element formed on the alumina ceramic substrate is protected with a silicone resin, and a plurality of convex portions B are provided on the surface of the silicone resin. In addition, the convex portion B is not necessarily formed.

However, when a protective film is formed on the surface of the wafer W, spin coating is generally used. In spin coating, a liquid resin is dropped onto the center of the surface of the wafer W, and a holding table holding the wafer W is rotated at high speed. Thereby, a centrifugal force is formed on the liquid resin, and the liquid resin is diffused from the center of the wafer W to the outer periphery. As a result, the liquid resin can be applied to the entire surface area of the wafer W. However, in spin coating, a large amount of liquid resin is caused by the high-speed rotation of the holding table 2 (more specifically, about 90% of the liquid resin that has been dropped on the center of the surface of the wafer W). If blown away, the liquid resin blown away will be discarded. As described above, in the formation of a protective film by spin coating, saving of a liquid resin has been a problem for a long time.

Therefore, the applicant of the present invention has thought of attaching a resin sheet 10 (see FIG. 2) having a shape matching the wafer W to the surface of the wafer W, and transferring the protective resin 12 (see FIG. 2) constituting the protective film to the wafer W surface method. Thereby, a protective film corresponding 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 on the entire surface area of the wafer W regardless of the surface shape of the wafer W. In addition, by using the resin sheet 10 that conforms to the shape of the wafer W, a protective film can be formed with the minimum required amount of the protective resin 12 and the protective resin 12 can be saved. the following, The resin sheet used in the coating method of the protective film of this embodiment is demonstrated.

As shown in FIG. 2, the resin sheet 10 is formed by applying a gel-like protective resin 12 on the surface of a circular release sheet 11 having a diameter substantially the same as that of the wafer W, and is formed into a thin film. After the resin sheet 10 is attached (adhered) to the surface of the wafer W, a protective film is formed on the entire surface area of the wafer W by drying. The release sheet 11 is formed of a film of a synthetic resin such as polyethylene terephthalate (PET). The protective resin 12 is made of a resin having water solubility and thermoplasticity such as polyvinyl alcohol (PVA) and polyethylene glycol (PEG). Furthermore, it is desirable that the gel-like protective resin 12 has a viscosity such 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.

Further, it is preferable to add an absorbent that absorbs light of a laser wavelength to the protective resin 12. Accordingly, during laser processing, the protective film can be removed at the same time as the wafer W is processed, so that the protective film can be prevented from being peeled from the surface of the wafer W due to the vapor of the thermal decomposition product of the wafer W and the like. Situation. In addition, the resin sheet 10 is not limited to the above-mentioned structure, and may be any structure as long as it is an article that can be attached to the surface of the wafer W to form a protective film. For example, the protective resin 12 may be formed of a thermoplastic resin film or a water-soluble resin film. At this time, the release sheet 11 is not necessarily provided.

Next, a protective film forming apparatus according to this embodiment will be described. As shown in FIG. 3, the protective film forming apparatus 1 is configured to attach a resin sheet 10 (see FIG. 2) to a surface of a wafer W, and the wafer W is placed on a holding table 2. And the upper surface is held by a plurality of clamping means 3. The holding table 2 is formed in a disc shape, and a holding surface that attracts and holds 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 a porous ceramic, and the holding surface is connected to a suction source (not shown). The wafer W placed on the holding table 2 is attracted and held by the negative pressure generated on the holding surface. An upper end portion of a 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 capable of rotating while receiving the rotational force of the electric motor 20.

In addition, a plurality of (for example, four) holding means 3 are arranged on the outer periphery of the holding table 2 at regular intervals in the circumferential direction of the holding table 2. The clamping means 3 is configured to clamp the upper and lower surfaces of the ring-shaped frame F, and the clamping mechanism 31 is mounted on the arm 30 protruding from the outer peripheral surface of the holding table 2. The clamping mechanism 31 supports a lower surface of the ring frame F (holding tape T) by a cylindrical driving mechanism 32 having a rotation axis (not shown) in a circumferential direction (horizontal direction) of the holding table 2. The fixed support part 33 and the movable support part 34 which supports the upper surface of the ring-shaped frame F are comprised.

The driving mechanism 32 is constituted by, for example, an air-driven rotary actuator. The fixed support portion 33 is formed of an elongated body extending in the horizontal direction. One fixed support portion 33 is mounted on each of both side surfaces of the drive mechanism 32 so that the front end portion (from the outer peripheral surface of the drive mechanism 32) protrudes radially inward of the holding table 2. The movable support portion 34 is formed in an L-shape when viewed from the side, and has one end fixed to a rotation shaft of the drive mechanism 32. The movable support portion 34 is formed to be driven by the drive mechanism 32 so that the movable support portion 34 can be held at a clamping position (the front end of the fixed support portion 33 and the movable support portion) to clamp the ring frame F. The position where the front end of 34 is opposed) and the retracted position retracted from the fixed support portion 33. In this manner, the clamping mechanism 31 is formed so that the ring frame F (wafer W) can be clamped between the fixed support portion 33 and the movable support portion 34.

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 mounting means 4 includes a resin sheet holding means 40 that grasps and holds one end of the resin sheet 10 and a moving means 41 that moves the resin sheet holding means 40 in a horizontal direction. The moving means 41 includes a guide rail 42 extending in a horizontal direction above the holding table 2 and a moving block 43 movable along the guide rail 42. The moving block 43 is driven by a driving mechanism (not shown) to move in a horizontal direction along the guide rail 42.

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 on the front end of the arm portion 44 extending downward from the moving block 43. The arm 30 is configured to be expandable and contractible 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 the upper holding claw 45b is brought closer to the lower holding claw 45a so as to be held by one end of the resin sheet 10. In the mounting means 4, the resin sheet 10 can be placed on the surface of the wafer W by moving the resin sheet holding means 40 horizontally and expanding and contracting the arm portion 44 while the resin sheet 10 is already held. In the predetermined position. The operation of the placing means 4 will be described later.

The details will be described later, but the protective film forming apparatus 1 has a structure in which air is sprayed toward the wafer W after the resin sheet 10 is placed. Air injection nozzle 5 (see FIG. 5). By spraying air toward the wafer W (resin sheet 10), the protective resin 12 (see FIG. 2) of the resin sheet 10 can be closely adhered to 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 sprayed toward the resin sheet 10. Thereby, the protective resin 12 of the resin sheet 10 is closely adhered to the surface of the wafer W, and the resin sheet 10 is attached to the wafer W. After the resin sheet 10 is attached, the protective sheet 12 constituting the protective film can be transferred to the surface of the wafer W by peeling off the release sheet 11. Further, the protective resin can be dried and hardened by rotating the holding table 2. With the above, a protective film corresponding to the thickness of the resin sheet 10 (protective resin 12) can be formed on the surface of the wafer W. As described above, by covering the surface of the wafer W with the protective film, it is possible to prevent the debris generated by the laser processing from adhering to the surface of the wafer W.

Next, a method for coating the protective film according to this embodiment will be described with reference to FIGS. 4 to 6. FIG. 4 is a diagram showing an example of a resin sheet placing step in the present embodiment. In FIG. 4, for convenience of explanation, the right side of the paper surface is regarded as one end side of the resin sheet (including the wafer and the holding tape), and the left side of the paper surface is regarded as the other end side of the resin sheet. FIG. 5 is a diagram showing an example of a sticking procedure in the present embodiment. FIG. 6 is a diagram showing an example of a curing step in the present embodiment. The covering method of the protective film of this embodiment is composed of the following steps: a resin sheet mounting step of placing a resin sheet on the surface of the wafer to cover the entire surface area of the wafer, and attaching the resin sheet to the wafer And a hardening step of hardening a resin sheet (protective resin). The following explains Each step of the coating method of the protective film of this embodiment.

As shown in FIG. 4, first, a resin sheet mounting step is performed. The wafer W is supported by the ring frame F through the holding tape T with the convex portion B facing upward, and is sucked and held on the holding surface of the holding table 2. At this time, a part of the ring frame F and the holding tape T are 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. In addition, the horizontal position of the resin sheet holding means 40 and the height position of the pair of holding claws 45 (the length of the arm portion 44) are adjusted so that the other end side of the resin sheet 10 is positioned on the wafer W (the holding table 2) ) On the other side.

After the mounting means 4 makes the other end of the resin sheet 10 contact the other end of the wafer W, it lowers the height position of the pair of holding claws 45 while holding one end of the resin sheet 10 (while lowering the arm portion 44 is extended), while moving the moving block 43 along the guide rail 42 from the other end side toward the one end side. Thereby, the resin sheet 10 can be placed on the surface of the wafer W with the center of the resin sheet 10 and the center of the wafer W aligned and the protective resin 12 facing downward. In the state shown in FIG. 4, the surface of the protective resin 12 is brought into contact with the apex of the convex portion B, and a gap corresponding to the height of the convex portion B is formed between the protective resin 12 and the wafer W.

Next, the attaching step is performed. First, the necessary configuration in the attaching step will be described. As shown in FIG. 5, an air ejection nozzle 5 that ejects 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 jet nozzle 5 is located above the outer peripheral side of the holding table 2 with a vertical portion 5a extending in the vertical direction and facing from the lower end of the vertical portion 5a. The horizontal portion 5b extending in the horizontal direction is formed in a substantially L-shape. The front end of the horizontal portion 5b is bent downward, and air can be ejected toward the resin sheet 10 from the curved front end portion. A rotary motor 51 is provided at the upper end of the vertical portion 5a. By driving the rotary motor 51, the air jet nozzle 5 can be rotated around the vertical portion 5a above the wafer W as an axis.

In the attaching step, the air is sprayed while covering the entire area of the wafer W while the air jet nozzle 5 is wound. Thereby, the resin sheet 10 is pressed toward the wafer W by the spraying force of air. As a result, the gel-shaped protective resin 12 can be slightly deformed in accordance with the shape of the convex portion B, and can be closely adhered (attached) to the surface of the wafer W without any gap. Then, the peeling sheet 11 is peeled off to transfer the protective resin 12 to the surface of the wafer W. It should be noted that the peeling sheet 11 may not be peeled off.

Next, a hardening step is performed. As shown in FIG. 6, in the hardening step, the protective resin 12 is hardened by rotating the holding table 2. Thereby, a protective film corresponding to the thickness of the protective resin 12 can be formed on the surface of the wafer W. In addition, the fan 6 provided above the wafer W may blow the wind toward the protective resin 12 to dry the protective resin 12.

As described above, according to the coating method of the protective film of this embodiment, after the resin sheet 10 is placed on the surface of the wafer W, the resin sheet 10 can be adhered to the entire surface area of the wafer W, and the A protective film corresponding to the thickness of the resin sheet 10 (protective resin 12) is formed on the surface of W. Accordingly, regardless of the surface shape of the wafer W, for example, even if the wafer W is formed with convex portions such as bumps on the surface, a protective film having a uniform thickness can be formed over the entire surface area of the wafer W. In addition, by using a tree of a shape matching the wafer W The fat sheet 10 can form a protective film with the necessary minimum amount of the protective resin 12, and can save the protective resin 12.

Next, the attaching procedure of the first modification will be described with reference to FIG. 7. FIG. 7 is a diagram showing a sticking procedure according to a first modification. The first modification is different from the present embodiment in that the resin sheet (protective resin) is used to make it adhere to the wafer by using the thermoplasticity. In the following description, configurations having the same names are denoted by the same symbols.

As shown in FIG. 7, a heater 7 is provided above the holding table 2 so as to cover the entire surface area of the wafer W. In addition, the resin sheet 10 in the first modification does not include a release sheet, and is composed of only a thin-film protective resin 12. In the attaching step of the first modification, the resin sheet 10 (protective resin 12) is heated by causing the heater 7 to generate heat. Since the protective resin 12 is thermoplastic, it is melted by being heated. With this, the convex portion B of the protective resin 12 can be slightly deformed according to the shape, and can be closely adhered (attached) to the surface of the wafer W without any gap. In addition, as in this embodiment, a protective film can be formed by performing a curing step. As described above, in the first modification, a protective film corresponding to the thickness of the resin sheet 10 (protective resin 12) may be formed on the surface of the wafer W.

Also, the following modifications are possible. Referring to FIG. 8, a description will be given of a second modification example. FIG. 8 is a diagram illustrating a step of attaching a second modification. The second modification is different from the present embodiment in that the resin sheet (protective resin) is made to adhere to the wafer by being water-soluble.

As shown in FIG. 8, a water spray nozzle 8 that sprays water toward the surface (resin sheet 10) of the wafer W is provided above the holding table 2. The tree of the second modification Similarly to the first modification, the fat sheet 10 is not provided with a release sheet and is composed of only a thin-film protective resin 12. In the attaching step of the second modification, water is sprayed from the water spray nozzle 8 over the entire area covering the resin sheet 10. Since the protective resin 12 is a water-soluble resin, it has fluidity by absorbing the sprayed water. Thereby, the protective resin 12 flows in accordance with the shape of the convex portion B, and is closely adhered (attached) to the surface of the wafer W without any gap. In addition, as in this embodiment, a protective film can be formed by performing a curing step. In this manner, in the second modification, a protective film corresponding to the thickness of the resin sheet 10 (protective resin 12) may be formed on the surface of the wafer W.

The present invention is not limited to the above-mentioned embodiments, and can be implemented with various modifications. In the above-mentioned embodiment, the size, shape, and the like shown in the attached drawings are not limited to this, and it is possible to appropriately change within a range where the effects of the present invention can be exhibited. In addition, as long as it does not deviate from the objective of this invention, it can implement suitably by changing it suitably.

For example, in the above-mentioned embodiment, although the mounting means 4 is configured to slide the resin sheet 10 in the horizontal direction by grasping one end of the resin sheet 10, the resin sheet 10 is placed on the surface of the wafer W The above structure is not limited to this structure. The mounting means 4 may be configured in any manner as long as the resin sheet 10 can be mounted on the surface of the wafer W. For example, the release sheet may be sucked and held by an adsorption table with the release sheet side of the resin sheet 10 facing upward, and after the adsorption table is positioned above the wafer W, the adsorption table may be lowered to protect the resin 12 It is in contact with the surface of the wafer W. At this time, the resin sheet 10 can be placed by releasing the suction and holding of the resin sheet 10. On the surface of wafer W.

Moreover, in the said embodiment, although it was set as the structure which carried out the resin sheet mounting process and the attaching process separately, it is not limited to this structure. For example, the resin sheet 10 may be configured as a roll, the resin sheet 10 may be fed to the surface of the wafer W by a feed roller, and the resin sheet 10 may be directed toward the wafer W by a pressing roller provided above the wafer W. Press on the surface. At this time, the resin sheet placing step and the attaching step can be performed at the same time, and the covering method of the protective film can be simplified.

Moreover, in the said embodiment, although the coating method of the protective film was implemented by the protective film formation apparatus 1, it is not limited to this structure. The coating method for protecting the film may be implemented by an operator.

Industrial availability

As described above, the present invention has the effect of uniformly forming a protective film on the surface of a wafer regardless of the surface shape of the wafer, and particularly, it is a protective film for coating a wafer having convex portions such as bumps on the surface. The covering method is useful.

Claims (2)

A method for coating a protective film is to form a protective film on the surface of a plate-shaped wafer with resin. The method for coating the protective film is composed of the following steps: a resin sheet mounting step, and a film-like resin containing the protective resin The protective resin covers the entire surface of the surface. The protective resin has a water-soluble and gel-like viscosity that does not flow from the surface to the outside of the wafer. The resin sheet covering the entire surface of the surface is sprayed with air in the mounting step to adhere the protective resin to the surface to attach the resin sheet; and a hardening step to harden the protective resin after the attaching step. For example, the method for coating a protective film according to claim 1, wherein the resin sheet is formed by coating the protective resin on a release sheet that matches the shape of the wafer, and in the resin sheet placing step, the resin sheet faces the protective resin The wafer is placed on the side, and in the attaching step, the protective resin is tightly adhered to the surface by pressing the wafer with the spraying force of the air through the release sheet, and then the release sheet is peeled off. Instead, the protective resin is transferred to the surface.