JP2003178948A - Method for forming photoresist film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoresist film forming method capable of forming a tick photoresist film which is uniform in thickness at a low cost. <P>SOLUTION: A photoresist liquid film 5 is uniformly applied in an opening 4 provided to a squeegee mask 1 on a semiconductor wafer 2 so as to be uniform in thickness by the use of a squeegee 6, by which a thick photoresist film 7 that is uniform in thickness can be formed on the semiconductor wafer 2 at a low cost. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a thick photoresist film covering a semiconductor wafer.

[0002]

2. Description of the Related Art A photoresist film used for forming and processing an arbitrary pattern on a semiconductor wafer adjusts the viscosity of the resist and, when it is formed by a spin coating method, adjusts its rotation speed. By doing so, a predetermined film thickness is obtained. 6A to 6D show a conventional photoresist film forming method, and FIGS. 6A to 6D are process cross-sectional views of main parts shown in the order of processes.

First, the semiconductor wafer 10 is placed on the support base 101.
2 is set ((a) in the figure). Next, the photoresist solution 103 is dropped and the support base 101 is rotated ((b) of the same figure). By this rotation, the photoresist solution 103 is centrifugally extended to the outer peripheral portion of the semiconductor wafer 102, and the side wall b
The photoresist solution 103 also adheres to the surface (FIG. 7C). Next, the photoresist solution 103 is heated and heated.
Is cured to form a photoresist film 104 (FIG. 7 (d)). As described above, in the spin coating method, the photoresist film 104, which may become particles during the transportation of the apparatus used in the subsequent process, is attached to the outermost periphery a, the side wall b, and the back surface c of the semiconductor wafer 102. In many cases, an organic solvent called a side rinse is used for the outer peripheral portion a and the side wall b of the front surface of the semiconductor wafer 102, and a back rinse is used for the rear surface c of the semiconductor wafer 102.
The photoresist film 104 is removed.

[0004]

Recently, in order to reduce the size of a semiconductor device having an integrated circuit as shown in FIG. 7, a semiconductor chip 201 is molded with a resin 203,
The pad portion 202 formed on the semiconductor chip 201 has the same thickness as the resin 203 (several tens μm to 100 μm).
Groove is formed, and a metal pillar 204 having a height F of about several tens of μm is formed by metal plating up to the middle of this groove.
The resin 203 is removed until 04 is exposed, and a solder ball 205 is formed on the surface of the exposed metal pillar 204,
Wiring of printed circuit board (not shown) and this solder ball 2
CSP (Chip Size Pa)
The development of semiconductor devices using such devices is actively carried out.

In order to manufacture a semiconductor device using this CSP or the like, as described above, a thick photoresist film having a thickness of several tens to 100 μm is required as a mask for metal plating. In the above-described coating apparatus used in the spin coating method, the coating portion of the photoresist liquid is exhausted from the outer peripheral portion a of the semiconductor wafer 102. Therefore, volatilization of the organic solvent contained in the photoresist liquid 103 is prevented. The outer peripheral portion a is faster than the central portion. Therefore, the viscosity of the photoresist liquid on the outer peripheral portion a becomes high, and it becomes more difficult for the photoresist liquid to move to the outside. On the other hand, since the viscosity of the photoresist liquid in the central portion has not yet increased, it flows to the outer peripheral portion, and as a result, the outer peripheral portion is thicker than the central portion as shown by the dotted line d. The thickness of the outer peripheral portion b is about 1.4 times that of the central portion.

When a film thickness of several tens of μm is required, the amount of the solvent is extremely reduced and the viscosity is reduced as compared with the case of forming a photoresist film of a normal film thickness of several μm. By increasing the height, a thick film is achieved, and in this case, the magnification is further increased. Therefore, the film thickness difference between the outer peripheral portion and the central portion becomes several μm to several tens of μm, and it becomes difficult to completely remove the photoresist film on the outer peripheral portion even with the subsequent side rinse.

Further, it becomes more difficult to form an extremely thick photoresist film having a thickness of about 100 μm by the spin coating method. An object of the present invention is to solve the above problems and provide a photoresist film forming method capable of forming a photoresist film with a uniform and thick film thickness at low cost.

[0008]

In order to achieve the above object, in a photoresist film forming method for forming a thick photoresist film on a semiconductor wafer, a step of installing the back surface of the semiconductor wafer on a support base. A step of bringing a first mask having a predetermined film thickness and having an opening whose outer peripheral edge is larger than the outer peripheral edge of the semiconductor wafer and smaller than the outer peripheral edge of the semiconductor wafer into close contact with the semiconductor wafer; A step of dropping a liquid photoresist on the semiconductor wafer, and using a squeegee longer than the opening, the dropped liquid photoresist is made to have a thickness equivalent to that of the first mask over the opening. A forming method includes a step of stretching and a step of heating and solidifying the stretched liquid photoresist to form a photoresist film.

In the opening of the first mask, a pillar for closely covering the pad portion formed on the semiconductor chip and a third mask in which the upper portion of the pillar is connected to each other by a connecting body are formed. The third mask and the first mask are connected to each other, and the height of the pillar of the third mask is preferably flush with the height of the first mask. By doing so, a thick photoresist film can be uniformly formed on a semiconductor wafer at low cost by using a squeegee and a mask.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a method of forming a resist film according to a first embodiment of the present invention. FIGS. 1A to 1D are sectional views showing the main process steps in order of process. is there. In FIG. 1A, a semiconductor wafer 2 is set on a supporting table 3 and a mask 1 having a predetermined film thickness and having an opening 4 at the center thereof.
Are brought into vacuum contact with the outer peripheral portion of the semiconductor wafer 2.

In FIG. 1B, a photoresist solution 5 is dropped on the surface of the opening 4 where the semiconductor wafer 2 is exposed. In the same figure (c), the dropped photoresist solution 5 having a viscosity of 1000 CP is opened using a squeegee 6.
The film is evenly spread over the entire surface to the same thickness as the mask 1.

In FIG. 1D, the photomask liquid 5 is semi-cured (not completely cured) by prebaking at 90 ° C. for several seconds, the mask 1 is removed, and the photoresist film 7 is removed from the support base 3. The covered semiconductor wafer 2 is removed and post-baked at about 120 ° C. for several minutes to completely cure the photoresist film 7. In this way, by using the squeegee mask 1 and the squeegee 6 for the semiconductor wafer 2 to apply and cure the photoresist solution 5, a uniform and thick photoresist film 7 is formed on the semiconductor wafer 2.
Can be formed in the central portion (region to be the semiconductor chip) of the. A photoresist film 7 is formed on the outer peripheral portion of the semiconductor wafer 2.
Since the film is not formed, the side rinse is not required, and the cost can be reduced. The material of the mask 1 may be metal or resin. Further, the amount of the photomask liquid 5 needs to be larger than the amount that allows the opening 4 of the mask 1 to be uniformly filled with the thickness W of the mask 1. Further, the viscosity of the photoresist solution 5 does not need to be high as in the case of forming a thick film in spin coating. As the viscosity,
It may be about several cp to 1000 cp, and the baking conditions may be changed according to the viscosity.

Further, a squeegee 6 is used for the photoresist solution 5
In order to evenly extend the object, it is advisable to sweep it in multiple directions in the front, rear, left, and right directions more than once. After the step of FIG. 1D, although not shown, the photoresist film 7 having a thick film thickness of about 100 μm is formed by photolithography.
For example, only the bonding pad is opened by photolithography, and a metal pillar of several tens of μm is formed on the bonding pad in this opening by using metal plating or the like. After that, the photoresist film 7 is removed, and further,
The exposed seed layer (which covers the entire semiconductor wafer with a metal film serving as a plating electrode: the seed layer on the bond pad is omitted in FIG. 7) is removed to replace the metal pillars with the seed layer. Do not electrically connect with. After that, the semiconductor wafer in which the metal pillar is formed on the bonding pad is cut into a semiconductor chip, the semiconductor chip is resin-molded, the resin is scraped to expose the metal pillar, and a solder ball is formed on this exposed surface. CS as in Figure 7
A P semiconductor device can be manufactured.

2A and 2B are configuration diagrams of the mask and squeegee used in FIG. 1. FIG. 2A is a plan view and FIG. 2B is a cross-sectional view taken along line X--X in FIG. FIG. The squeegee mask 1 has a minute tunnel 8 of about 10 μm open therein. By vacuuming the tunnel 8, the mask 1 is brought into close contact with the outer peripheral portion of the semiconductor wafer 2.
The squeegee 6 is longer than the opening 4 of the mask 1, and the squeegee 6 is used to spread a photoresist solution (not shown) over the entire opening 4 of the mask to a uniform thickness. The film thickness is similar to a mask.

FIG. 3 is a block diagram of a mask corresponding to FIG. 2 in the resist film forming method of the second embodiment of the present invention.
The figure (a) is a top view and the figure (b) is an A section enlarged view of the figure (a). FIG. 4 is a cross-sectional view of each part of FIG. 3B, FIG. 4A is a cross-sectional view of a main part taken along line XX of FIG. 4B, and FIG. 3B is a sectional view of a main part taken along the line YY, and FIG. 3C is a sectional view of the main part taken along the line ZZ of FIG. 3B.

FIG. 5 is a sectional view of each part of the photoresist film formed by using the mask used in FIG. 3, and FIG. 5 (a) is a sectional view of the main part corresponding to FIG. 4 (a). (B)
4C is a cross-sectional view of the main part corresponding to FIG. 4B, and FIG.
It is a principal part sectional view corresponded to (c). This will be described with reference to FIGS. 3 to 5. The difference from FIG. 2 is that a rod-shaped mask 21 is added to the mask 2 used in FIG. 2 at a position corresponding to the pad 32 so that the photoresist film 24 does not cover the pad 32 formed on the semiconductor wafer 2. That is the point. The rod-shaped mask 21 is composed of a rod-shaped column 22 and a connector 23 that connects the column 22.

The pillars 22 have heights H of the pillars 22 relative to each other.
The point is that a knitted mask connected by a connecting body 23 having a smaller thickness T is used in the opening 4 of FIG. By using the rod-shaped mask 21, the rod-shaped groove 25 can be formed in the photoresist film 24 on the pad 32. Also in this case, since the photolithography is not used and the amount of the photoresist liquid can be reduced, the manufacturing cost can be reduced as compared with the case of using the mask 1 of FIG.

Further, the thickness of the photoresist film 24 is set to 10
If the depth is about 0 μm, the depth of the groove 25 is about 100 μm. By forming a metal column (not shown) having a thickness of several tens of μm by metal plating on the pad 32 at the bottom of the groove 25, and resin molding, Since the semiconductor device such as CPS can be manufactured without performing the photolithography described in FIG. 1, the manufacturing cost can be reduced.

[0019]

According to the present invention, by using a squeegee and a mask for a squeegee, a uniform and thick photoresist film, which is difficult in the spin coating method, can be formed at a low cost in the central portion of a semiconductor wafer. Can be formed. In addition, by adding a rod-shaped mask to the opening of this squeegee mask, which contacts a portion corresponding to the pad formed on the semiconductor wafer, the photoresist film on the pad is used without using photolithography. Can be removed, and the manufacturing cost of the semiconductor device such as CSP can be formed.

[Brief description of drawings]

FIG. 1 is a diagram showing a method of forming a resist film according to a first embodiment of the present invention, in which (a) to (d) are process cross-sectional views of a main part shown in the order of processes.

2A and 2B are configuration diagrams of the mask and squeegee used in FIG. 1, in which FIG. 2A is a plan view and FIG. 2B is a sectional view of a main part taken along line XX in FIG.

3A and 3B are configuration diagrams of a mask corresponding to FIG. 2 in a resist film forming method according to a second embodiment of the present invention, FIG. 3A is a plan view, and FIG. 3B is an enlarged view of part A of FIG.

4A and 4B are cross-sectional views of each part of FIG. 3B, in which FIG. 4A is a cross-sectional view of a main part taken along line XX of FIG. 3B, and FIG. 4B is Y of FIG. 3B. 3B is a cross-sectional view of the main part cut along the line Y, and FIG. 3C is a cross-sectional view of the main part cut along the line ZZ of FIG. 3B.

5 is a cross-sectional view of each part of a photoresist film formed using the mask used in FIG. 3, (a) of FIG.
4B is a sectional view of an essential part corresponding to FIG. 4B, and FIG. 4C is a sectional view of an essential part corresponding to FIG. 4C.

FIG. 6 is a conventional photoresist film forming method,
(A) to (d) are process cross-sectional views of the main part shown in the order of processes

FIG. 7: CSP (Chip Size Packag)
Sectional drawing of the main part of the semiconductor device using e) etc.

[Explanation of symbols]

1 mask 2 Semiconductor wafer 3 support 4 openings 5 Photoresist liquid 6 squeegee 7, 13, 24 Photoresist film 8 tunnels 21 Rod-shaped mask 22 Rod-shaped pillars 23 Connected body 25 Rod-shaped groove 31 semiconductor chips 32 pads

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // B05C 11/02 H01L 21/30 564Z F term (reference) 2H025 AB16 EA04 4D075 AC53 AC78 AC92 BB26Z DA06 DA08 DB11 DC22 EA07 EA45 4F042 AA02 AA07 BA25 5F046 JA01 JA19

Claims (2)

[Claims] 1. A method of forming a thick photoresist film on a semiconductor wafer, comprising the step of setting a back surface of the semiconductor wafer on a support, the outer peripheral edge of which is larger than the outer peripheral edge of the semiconductor wafer. A step of bringing a first mask having a predetermined thickness having an opening smaller than the outer peripheral edge of the semiconductor wafer into close contact with the surface of the semiconductor wafer, and dropping a liquid photoresist onto the semiconductor wafer in the opening. Step, using a squeegee longer than the opening, a step of extending the dropped liquid photoresist to a thickness equivalent to the thickness of the first mask over the opening, and the extended liquid photoresist And a step of forming a photoresist film by heating the resist to solidify the photoresist film. 2. A pillar for closely contacting and covering a pad portion formed on the semiconductor chip and a third mask in which an upper portion of the pillar is connected to each other by a connecting body are formed in the opening of the first mask. , Connecting the third mask and the first mask,
The photoresist film forming method according to claim 1, wherein the height of the pillar of the third mask is flush with the height of the first mask.