JP2000100756A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately hold the adhesion degree of a tape adequate during pick up by having the back side of a substrate in an O-contg. atmosphere irradiated with ultraviolet rays, pasting an ultraviolet curing tape to the substrate back side, dicing the substrate into small pieces, and then irradiating with ultraviolet rays for curing the tape on the substrate back side. SOLUTION: After having the back side of a substrate in an O-contg. atmosphere irradiated with ultraviolet rays, an ultraviolet curing tape is pasted on the substrate back side, the substrate is diced into small pieces, and the substrate back side is irradiated with ultraviolet rays for curing the tape to peel off the small pieces from the ultraviolet curing tape. A dielectric barrier discharge Xe excimer lamp 14 plasma-discharges Xe, a rare gas, between a metal electrode 16 and a metal net electrode 17 in a circular drum to emit and irradiate ultraviolet rays on the back side of an Si wafer 1 in an O-contg. atmosphere. Since the ultraviolet ray is at low mean radiation density of 7 mW/cm2, hence it is irradiated for 60 sec.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for dicing a substrate using an ultraviolet-curable tape (hereinafter, referred to as a UV tape), and more particularly to a technique for appropriately separating a UV tape after dicing. A widely used method for dicing a substrate is to wash the back surface of the substrate, apply a UV tape, dice the substrate in that state, irradiate ultraviolet rays, and peel off the cut small pieces from the tape. That is the method. Because UV tape can be cured by UV irradiation and reduce its adhesion,
It is used to increase the reliability of the process by peeling as a high degree of adhesion during dicing and easy to peel as a low degree of adhesion during peeling, but the degree of adhesion is affected by the storage environment of the substrate before UV tape is attached. Therefore, it is important to determine whether or not the tape has an appropriate degree of adhesion at the time of tape peeling.

[0002]

2. Description of the Related Art FIGS. 2 and 3 are views for explaining steps in a conventional example of dicing a substrate. First, as shown in FIG. 2A, a silicon wafer 1 as a substrate is put in a quartz jig 2 and immersed in hydrofluoric acid (HF) 4 in a quartz tank 3 and etched. Since the front surface of the silicon wafer 1 is protected by the etching resistant tape 5 so as not to be etched, only the back surface is etched. Depending on the process, a gold film or the like may be formed on the back surface of the silicon wafer 1 in advance in order to facilitate dicing (attachment to a package). After the etching, the silicon wafer 1 is washed by washing with water (not shown in the figure).

Next, as shown in FIG. 2B, a frame 6 made of stainless steel or aluminum is used.
A UV tape 8 is attached so as to cover the hole 7, and the back surface of the silicon wafer 1 is attached from the back side. In this figure, the upper part is a plan view, and the lower part is a cross-sectional view cut along the AA plane. In this state, the silicon wafer 1 is set on a dicer and diced by a blade 9 to be divided into chips 10 as shown in an enlarged manner in FIG. At this time, the dicing depth is adjusted so that the UV tape 8 is not completely cut.

The diced chip 10 is shown in FIG.
As shown in FIG. 7, the back surface is irradiated with ultraviolet rays 11 in order to reduce the degree of adhesion of the UV tape 8. The ultraviolet rays 11 are, for example, ultraviolet rays having a wavelength of 365 nm generated by a high-pressure mercury lamp.
(Irradiance about 450 mW / cm ² ) and irradiate for about 1 second. Subsequently, as shown in FIG. 3B, the UV tape 8 is peeled off while pushing up the chips 10 one by one from the back surface of the chip 10 with a pick-up needle 12, and the collet 1 is removed.
Pick up with 3.

A supplementary description of the process shown in FIG. 2A is as follows. That is, after the wafer process, the silicon wafer 1 is ground on the back surface in order to obtain a desired thickness of the substrate, but is etched with an acid or an alkaline solution to remove distortion generated at this time, Polishing is usually performed using a slurry or the like. At this time, the back surface is washed at the same time, but the washing is not carried out sufficiently, or it may be left for a long time without being diced immediately after the treatment, and may be contaminated again during that time. , The gold film may be deteriorated due to silicon (Si) in the silicon wafer 1 or oxygen (O ₂ ) in the atmosphere if left unattended for a long time. Since these cause the adhesiveness of the tape not to decrease even when the ultraviolet rays 11 are irradiated, this step (a) is added to improve this, and usually, this step is performed immediately before the UV tape 8 is attached. Will be

[0006]

However, FIG.
Even if the process as shown in FIG. 3A is provided, the degree of adhesion of the UV tape 8 may not be properly reduced by the irradiation of the ultraviolet rays 11. For this reason, there has been still a problem that the chip 10 is not peeled off at the time of picking up, or if the chip 10 is forcibly peeled off, the chip 10 is scratched, cracked or broken. These cause a decrease in the operation rate of the apparatus and a decrease in the yield. The cause of the decrease in the adhesiveness of the tape is determined, and further improvement for realizing the appropriate adhesiveness of the tape has been desired.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a semiconductor device capable of maintaining an appropriate degree of tape adhesion during pickup.

[0008]

According to the present invention, there is provided, according to the present invention, [1] a step of irradiating a back surface of a substrate with a first ultraviolet ray in an atmosphere containing oxygen, and then applying an ultraviolet curing type to the back surface of the substrate. A step of attaching a tape, a step of dicing the substrate into small pieces, a step of irradiating a second ultraviolet ray for tape curing on the back surface of the substrate, and a step of peeling off the small pieces from the ultraviolet curable tape. [2] The method according to [1], further comprising, before the step of irradiating the first ultraviolet ray, etching the back surface of the substrate with hydrofluoric acid (HF). Or in [2], the first
Is achieved by being vacuum ultraviolet light or ultraviolet light generated by an excimer lamp.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 4 shows the result of investigation on the effect of etching with hydrofluoric acid (HF) in FIG. 2 (a). This etching process is applied to a silicon wafer with gold deposited on the back surface, a UV tape is attached, and the adhesive force of the tape after irradiating ultraviolet rays for lowering the adhesive force (or for curing the tape) is reduced to the above etching time. It looks at how it changes. It is inferred from these results that impurities that can be removed with hydrofluoric acid can be removed in a short time, while impurities that cannot be removed with hydrofluoric acid prevent the adhesion from being reduced. It is. As a result of observing the back surface of the silicon wafer before and after the hydrofluoric acid treatment to confirm this, the following became clear. (1) Organic substances adhere to the surface, and can hardly be removed by hydrofluoric acid. (2) The silicon under the gold film is oxidized, and if the gold film is thin, a portion is exposed on the surface. The structure is dominated by SiO (silicon monoxide). When this is treated with hydrofluoric acid, SiO
The area is increasing and the part exposed on the surface is also increasing.

The inventor of the present invention has proposed that these organic substances and SiO
It was expected that the adhesive strength would not be reduced even if it was strongly adhered to the V-tape and irradiated with ultraviolet rays for reducing the adhesive strength. Therefore, a step of irradiating the back surface of the silicon wafer with ultraviolet rays (center wavelength: 172 nm) generated by a dielectric barrier discharge xenon excimer lamp was added between the hydrofluoric acid etching step and the UV tape attaching step. FIG. 4 also shows how the adhesive force of the tape changed as a result. As in the other data, it was measured after irradiating ultraviolet rays for lowering the adhesive force under the same conditions. It was confirmed that the adhesive force was sufficiently reduced and was within a range where the pickup could be properly performed.

When observing the back surface of the silicon wafer after the irradiation of the ultraviolet rays, no organic matter was recognized, and silicon monoxide (Si) was not observed.
O) was changed to silicon dioxide (SiO ₂ ). The mechanism of the decrease in adhesive force in FIG. 4 inferred from these is as follows. As is well known, ultraviolet light, especially
For example, short-wavelength ultraviolet rays including those called vacuum ultraviolet rays of 200 nm or less are absorbed by oxygen (O ₂ ) in the atmosphere and generate very strong oxidizing power such as ozone (O ₃ ) and excited oxygen atoms O (1D). generate. The activated oxygen converts the organic matter into carbon monoxide (CO) and carbon dioxide (CO
₂ ) or decomposes into stable oxides such as water (H ₂ O)
It is considered that silicon monoxide (SiO) or silicon trioxide (SiO ₃ ) is changed to silicon dioxide (SiO ₂ ). The former evaporates in a normal process, and the latter silicon dioxide adheres to the tape stably, so that the degree of adhesion of the tape can be maintained at an appropriate level.

[0012]

FIG. 1 shows an embodiment of the present invention. As compared with the process explanatory diagrams of the conventional example of FIGS. 2 and 3, only the process shown in this figure is replaced by the process of FIG. 2A, and the subsequent processes are not changed, so that they are omitted. In the present embodiment, the back surface of the silicon wafer 1 is irradiated with ultraviolet rays (vacuum ultraviolet rays having a wavelength of 172 nm) 15 generated by the dielectric barrier discharge xenon excimer lamp 14 in an atmosphere containing oxygen. Since the irradiance of ultraviolet rays was as low as 7 mW / cm ^{2 on} average, irradiation was performed for 60 seconds. The dielectric barrier discharge xenon excimer lamp 14 has a structure in which a circular tube having a donut-shaped cross section is sealed in a cylinder, and xenon, which is one of the rare gases in the circular tube, is applied to a metal electrode 16 and a metal mesh electrode 17. Ultraviolet light emission (excimer light emission) is performed by causing a plasma discharge 18 between the two.

In the above embodiment, ultraviolet rays generated by a dielectric barrier discharge xenon excimer lamp are used as the ultraviolet rays. This is because the apparatus is compact and can efficiently generate short wavelength ultraviolet rays at present. This is because it is considered to be one (energy conversion efficiency from electric power to light of 10%) and is not limited to this. For example, an excimer lamp using a gas different from xenon, or ultraviolet light generated by various excimer lasers can be used. Further, from the viewpoint of wavelength, the shorter the wavelength, the larger the quantum energy becomes, so that ultraviolet light called vacuum ultraviolet light is considered to be particularly effective in the present invention. Further, this step is a conventionally known processing step, for example, hydrofluoric acid (HF)
It is also an advantage of the present invention that it can be used in combination with a chemical treatment step by etching or the like, and does not adversely affect each other when used in combination.

[0014]

The present invention is configured as described above, and has the following effects. By irradiating the back surface of the substrate with ultraviolet rays, it is possible to remove or stabilize contamination and alteration which are difficult to remove with hydrofluoric acid (HF) or the like, and it is possible to greatly increase the reliability in the pickup process. According to the conventional technique of treating with hydrofluoric acid (HF) immediately before attaching a UV tape, 70% or more of the diced pieces may not peel off in some cases. According to the present invention, this is reduced to 0%. be able to. There is a remarkable effect on the process management and economic effect accompanying this.

After the irradiation with the ultraviolet rays, the sheets were stored in a normal environment for several days, and then the steps after the application of the UV tape were performed. All dicing small pieces could be peeled off. For this reason, the effect obtained in the process control is great. Although the reason why there was no adverse effect even after long-term storage is not sufficiently clear, it is not clear whether organic substances or silicon monoxide (Si
This is probably because O) does not occur again in a normal storage environment once it has been removed.

Furthermore, in the present invention, chemical changes are caused to the contamination and alteration of the substrate by using an optical resource such as ultraviolet rays. This is in contrast to what is said to be a resource. For this reason, the device can be made compact, and the effect of securing work safety or environmental measures is great.

In this embodiment, the ultraviolet light generated by the dielectric barrier discharge xenon excimer lamp is irradiated for 60 seconds because of its low illuminance. However, good results are obtained even for about 30 seconds. This time is almost the same as the time generally required for the etching treatment with hydrofluoric acid, and shows the effectiveness of the present invention.

[Brief description of the drawings]

FIG. 1 shows an embodiment according to the present invention.

FIG. 2 is a process explanatory view of a conventional example (part 1).

FIG. 3 is a process explanatory view of a conventional example (part 2).

FIG. 4 is a diagram showing a tape adhesive force during pickup.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon wafer 8 UV tape 10 Chip 11 Ultraviolet light (for lowering adhesive strength) 13 Collet 15 Ultraviolet light (excimer emission)

Claims (3)

[Claims] 1. A step of irradiating a back surface of a substrate with first ultraviolet rays in an atmosphere containing oxygen, a step of applying an ultraviolet curing tape to the back surface of the substrate, and a step of dicing the substrate into small pieces And a step of irradiating the back surface of the substrate with a second ultraviolet ray for curing the tape, and a step of peeling off the small pieces from the ultraviolet curing type tape. 2. The method according to claim 1, further comprising a step of etching the back surface of the substrate with hydrofluoric acid (HF) before the step of irradiating the first ultraviolet ray. 3. The method according to claim 1, wherein the first ultraviolet ray is a vacuum ultraviolet ray or an ultraviolet ray generated by an excimer lamp.