JPH05315445A - Assembling method of solid-state imaging device - Google Patents

Abstract

PURPOSE:To prevent black mark generation due to cutting scrap in the assembling process of a solid-state imaging device, in particular, at the time of dicing, and improve the peeling rate of a surface protecting sheet. CONSTITUTION:A surface protecting sheet 5 is stuck on the surface of a wafer on which a solid-state imaging device is formed, and the wafer is stuck on a sheet 2 for dicing. After dicing, the sheet 2 for dicing is expanded, and the intervals ((a) and (b)) between cut-off chips 4 are ensured as specified values (e.g. 5mm or longer). After that, the surface protecting sheet 5 is exfoliated by using a sheet 3 for peeling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for assembling a solid-state image pickup device, and more particularly to a method for dicing a wafer.

[0002]

2. Description of the Related Art Conventionally, a wafer for a solid-state image pickup device has a general I
It was diced in the same manner as C. That is, the back surface of the wafer is attached to a dicing sheet for dicing, the dicing sheet is enlarged, and then the device is mounted on the package.

In the above dicing method, since cutting scraps produced by the blade are likely to adhere to the chip surface, the cutting scraps have been removed by running water at the same time as dicing. By this method, a certain effect has been achieved by optimizing the speed of the blade, the amount of flowing water, and the like. However, it has become clear that with the recent trend of increasing the number of pixels, the above-mentioned water washing means cannot prevent the yield reduction.

It is becoming more sensitive to fine dust with the miniaturization of pixels, and on-chip microlenses have been generalized to prevent the sensitivity from deteriorating, and the chip surface is made of organic material. This is because dust is likely to adhere to the lens surface, and the lens surface is easily damaged by cutting scraps or the like.

Therefore, a method has been devised in which a surface protective sheet is attached to the surface of a wafer prior to dicing, and then peeled off after dicing. FIG. 6 is the process flow. First, a surface protection sheet is attached to the front surface of the wafer, the back surface of the wafer is attached to the dicing sheet, and then dicing is performed. Next, after irradiating the surface with ultraviolet rays to reduce the adhesive strength of the surface protective sheet, the surface protective sheet is peeled off using a release sheet. Then, the wafer is divided into individual chips and the chips are mounted on a package.

[0006]

According to the above-mentioned method of attaching the protective sheet to the wafer surface, it is possible to prevent the cutting dust and the like from adhering to the chip surface, damage, etc. However, in the method according to the flow of FIG. Since the protective sheet was not smoothly separated from the wafer, the workability was poor and the practicality was poor.

[0007]

A method for assembling a solid-state image pickup device according to the present invention comprises attaching a protective sheet to the surface of a wafer having a solid-state image pickup element formed thereon, and peeling the protective sheet after dicing. After a predetermined distance is secured between the cut chips, the peeling sheet is attached and adhered, and then the protective sheet is peeled together with the peeling sheet.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a process flow of the first embodiment of the present invention, FIG. 2A is a plan view showing a state where the process marked with * in FIG. 1 is completed, and FIG. )
[Fig. 3] is a partial cross-sectional view of Fig. (A).

First, a surface protection sheet 5 having the same size as or slightly smaller than that of the wafer is attached to the surface of the wafer on which the solid-state image pickup device is formed, the adhesive strength of which is reduced by the irradiation of ultraviolet rays. Next, dicing is performed by bringing the back surface of the wafer into close contact with the dicing sheet 2 that has the same adhesive strength and is stretched by the irradiation of ultraviolet rays that is attached to the frame 1. Next, the dicing sheet 2 on the back surface is enlarged to divide the wafer into chips 4, and the peeling sheet 3 is attached (FIG. 2). Next, the surface protection sheet 5 is removed using the peeling sheet 3. Next, ultraviolet rays are radiated from the back surface to move to the mounting step.

FIG. 3 is a graph for explaining the effect of the present invention.
It is a graph which shows the relationship between the gap width between chips and the peeling rate of a surface protection sheet. Peeling of the surface protective sheet 5 from the chip 4 provides good adhesion with the chip 4 even when the adhesive force is reduced after irradiation with ultraviolet rays, and fine cutting scraps during dicing are attached to the surface protective sheet 5. So it's not easy.

When the peeling sheet 3 is used for peeling after dicing without enlarging the sheet, the peeling sheet 3 having an adhesive force about 80 times the adhesive force between the chip and the surface protection sheet is used. The rate at which the surface protection sheet 5 was peeled from the chip 4 (peeling rate) was 0%. Therefore, when a gap is provided between the chips after dicing and the distance is gradually increased with a = b, the peeling rate improves in proportion to this distance, and a peeling rate of almost 100% can be realized with a gap width of 5 mm. It was As shown in the cross-sectional view between the chips in FIG. 2B, this is because the separation sheet 3 adheres to the cross-section of the surface protection sheet 5 where the cutting dust is less adhered due to the gap between the chips 4. However, it is considered that this is due to the formation of a tail for peeling from the chip 4. Therefore, if the peeling sheet 3 has a certain distance, that is, the peeling sheet 3 has a sufficient contact area with the cross section of the surface protection sheet 5, the peeling can be sufficiently performed.

FIG. 4 is a process flow showing a second embodiment of the present invention, and FIG. 5 is a plan view showing a state where the process marked with * in FIG. 4 is completed. The steps from the step of attaching the wafer having the surface protective sheet attached thereto to the dicing sheet and performing the dicing are the same as those in the previous embodiment.

After that, ultraviolet rays are irradiated from the front surface and the back surface. Next, only the good chips 4 are re-arranged from the dicing sheet on the arranging sheet 7 stretched on the frame 1, and the peeling sheet 3 is attached on the surface protection sheet (FIG. 5). The surface protection sheet is peeled off using the peeling sheet 3, and the back surface is irradiated with ultraviolet rays, and then the mounting step is performed.

In this embodiment, although the process is slightly complicated, the gaps a and b between the chips can be set independently according to the shape of the chips, and it is possible to obtain a high peeling rate as in the previous embodiments. In addition, since the incompletely formed chip 6 as shown in FIG. 2 is eliminated, the incompletely formed chip 6 adheres to the peeling sheet 3 when the sheet is peeled off, and the cutting scraps attached thereto are redeposited. It can be prevented. Furthermore, in the present embodiment, even if a chip that could not be peeled occurs, the peeling step can be performed again by performing the same steps.

[0015]

As described above, according to the present invention, in the process of assembling the solid-state image pickup device, the surface protection sheet is attached to the surface of the wafer prior to dicing, and the gap between the cut chips is set to a predetermined value. Since the surface protection sheet is peeled off by the peeling sheet after securing the distance (for example, 5 mm), according to the present invention, adhesion of cutting scraps to the chip surface and surface damage due to cutting scraps or the like are prevented. Further, the surface protection sheet can be peeled off at a high peeling rate. Therefore, according to the present invention, it is possible to realize a method of manufacturing a solid-state imaging device with high practicability and high yield.

[Brief description of drawings]

FIG. 1 is a process flow chart of a first embodiment of the present invention.

2A and 2B are a plan view and a sectional view in one process step of the first embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the gap width between chips and the surface protection sheet peeling rate.

FIG. 4 is a process flow chart of the second embodiment of the present invention.

FIG. 5 is a plan view of one process step of the second embodiment of the present invention.

FIG. 6 is a process flow chart showing a prior art of the present invention.

[Explanation of symbols]

 1 Frame 2 Dicing Sheet 3 Peeling Sheet 4 Chip 5 Surface Protection Sheet 6 Incompletely Formed Chip 7 Arrangement Sheet

Claims (1)

[Claims] 1. A step of attaching a protective sheet to the front surface of a wafer on which a solid-state imaging device is formed, a step of attaching the back surface of the wafer to a dicing sheet to perform dicing, and a solid sheet via a release sheet. A method of assembling a solid-state image pickup device, comprising: a step of peeling off the protective sheet attached to the surface of the image pickup element chip, wherein peeling of the protective sheet is performed between predetermined solid-state image pickup element chips. A method of assembling a solid-state imaging device, characterized in that a gap of width is secured.