JPH0212811A - Aligning method for wafer periphery - Google Patents

Abstract

PURPOSE:To prevent the foaming of resist and the decrease of throughput by making the number of revolutions of a wafer or a light emitting mechanism equal to two or more, and making the integrated light exposure amount per unit area at the time of a first revolution, equal to or less than the light exposure amount of resist foaming. CONSTITUTION:While a wafer 1 or a light emitting mechanism 8 is rotated, the periphery 1b of the wafer 1 is irradiated with a spot light, and the peripheral resist spread on the wafer 1 is exposed to light. In this exposing method of wafer periphery, the exposure process is arranged as follows; the number of revolutions of the wafer 1 or the light emitting mechanism 8 is two or more; the integrated light exposure amount per unit area at the first revolution is equal to or less than the light exposure amount of resist foaming; the integrated light exposure amount by the exposure of the second and the later revolutions is more than or equal to a specified light exposure amount. Thereby, it does not occur that gas is discharged and leaves in the resist, until an light emitting end is rotated and comes to each part of the resist, in a period between the first exposure and the second and later exposure, so that the foaming is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wafer periphery exposure method for removing unnecessary resist from the periphery of an electronic material such as a semiconductor wafer coated with a photosensitive resist.

[Prior Art] Conventionally, in this type of technology, for example, in the technology for forming circuit patterns on semiconductor wafers, when forming a photosensitive resist film on a wafer, a spin coating method, generally called a spin code method, is used. It will be done.

FIG. 3 is a perspective view when UV (ultraviolet) light is guided by a light guide fiber and irradiated onto the wafer peripheral area tb, which is an unnecessary part of the resist applied to the semiconductor wafer, and FIG.
Figures a) and (b) are diagrams showing the state in which light irradiation is performed for exposure using the method shown in Figure 3, where Figure (a) is a plan view and Figure (b) is a plan view.
is a side sectional view thereof.

In FIGS. 3 and 4, l is a wafer, and 1a is a pattern forming section, which uses a desired pattern (not shown), reduces it to a fraction of the size with a lens (not shown), and exposes it onto the wafer l. , a reduction exposure method (!1iTE) that repeats this exposure one after another.
A pattern is formed using the P AND REPEAT method. Further, lb is the wafer periphery, 1c is the resist protrusion, 30 is the orientation flat of the wafer l (hereinafter referred to as orientation flat), 8' is a light guide fiber made of quartz that guides UV light from a UV irradiation light source (not shown), and 4a
is an irradiation portion to which UV light is irradiated from this light guide fiber 8', and the wafer 1 rotates to irradiate the wafer peripheral portion 1b with light.

The spin code method of applying resist to the wafer 1 is the fourth step.
The wafer 1 shown in FIG. 1A is placed on a rotating table, resist is poured onto the wafer 1 near its center and rotated, and the resist is applied to the entire surface of the wafer 1 using centrifugal force. However, according to this spin code method, the 41st
As shown in FIG. 3(b), the resist may sometimes protrude from the wafer periphery 1b of the wafer 1 due to its surface tension, go around to the back side, or bulge at the wafer periphery ib. Generally, the wafer peripheral part lb of the wafer l has a cross section as shown in FIG. It is not formed in the wafer peripheral part 1b on the surface of the wafer, but is formed in the other part (pattern formation part) la (see t53 (a), tH4).
There is no particular need to apply a pattern-forming resist to the wafer peripheral area 1b. However, in the spin code method, resist is inevitably applied to this area as well. In the past, has there been any proposal for a spin code method that eliminates the resist flakes around the wafer? Even in that case, the resist still remains to be applied to the wafer peripheral area 1b.

Such unnecessary resist, that is, the resist protruding portion 1c that extends to the back side as shown in FIG. 4(b), and the wafer l
The peripheral resist part applied to the wafer peripheral part ib is
If this remains, it may cause problems. Resist is generally characterized by being hard and brittle due to the resin itself, so if a mechanical shock is applied to the wafer during the L process, such as when the wafer is grabbed for transportation or rubbed, it may break off.
There is a possibility that it will become dust and have no adverse effects, so it is C.

Particularly, when a resist piece is missing from the resist protruding portion 1c (see FIG. 4(b)) of the wafer L while the wafer L is being transported,
This may adhere to the wafer 1 and not be etched, resulting in pattern defects, or act as a mask during ion implantation, obstructing necessary ion implantation, resulting in a decrease in yield. Further, when performing high-energy, high-concentration ion implantation, resist cracks may occur due to thermal stress generated from around the sea urchin during ion implantation.

It has been confirmed that these resist cracks occur from irregular or scratched areas of the resist at the periphery of the wafer and run toward the center.

This problem has arisen as the density and integration of semiconductor devices progresses, and in order to maintain yield, conventional contact methods or l:
The exposure method has changed from an exposure method using an l-projection aligner to a reduction projection method called the step mentioned above, and as a result, the negative resist, which was the mainstay of the conventional photo process for pattern formation, has been replaced. Against the background of having to use positive resists, FFI is extremely important.

As a method to remove such unnecessary parts of the resist,
A solvent injection method is used. In this method, a solvent is sprayed from the back side of the wafer l to which the resist is attached, and unnecessary resist is dissolved away. However, with this method, although the resist in the resist protruding portion 1c in FIG. 4 can be removed, the raised portion of the resist in the wafer peripheral portion 1b is not removed.

Spraying a solvent from the surface to remove the resist at the wafer peripheral portion tb may have an adverse effect on the resist portion 1a where the pattern is being formed.

Although the above-mentioned problem caused by the detachment of resist pieces can be improved by removing the resist in the resist protruding portion 1c, it is still not sufficient and it is necessary to also remove the resist in the wafer peripheral portion 1b.

Therefore, as a method for easily and reliably removing unnecessary resist in this area, UV light irradiation as shown in FIG. 3 has conventionally been used. However, even in this UV light irradiation, the shape of the UV light irradiated portion on the wafer 1 was circular.

Further, FIGS. 5(a) and 5(b) are diagrams for explaining the exposure shape of UV light irradiation on the wafer peripheral area 1b.
a) shows a shape exposed by conventional light irradiation. As is clear from FIG. 5(a), the wafer peripheral area 1b
The outer peripheral part 1b-1, the inner peripheral part 1b-3, and the peripheral center part 1b
-2, the cumulative exposure amount is different. As a result, the periphery of the wafer 1 is exposed non-uniformly, and the resist cannot be removed uniformly after development.

Therefore, as shown in FIG. 5(b), the exposure shape of the UV light irradiation on the wafer peripheral part 1b is made rectangular, and the outer peripheral part 1b is
The cumulative exposure amount at b-1, the inner peripheral portion 1b-3, and the peripheral center portion 1b-2 is made to match.

In general, UV exposure for resist coated on a wafer depends on the type of resist, but when the film thickness is 21 mm, it is usually 1.
If the peripheral area 1b of the wafer rises to about 4g+s as shown in FIG. 4(b), the required exposure amount is 300"J/.2". Requires irradiation.

[Invention or problem to be solved] As mentioned above, in the conventional wafer peripheral exposure method.

For example, 300″″J/. If an attempt is made to perform an exposure amount of
8. The light energy 7 of the snow is applied in a short period of time, causing the resist to foam. The reason for this is that when the resist is irradiated with ultraviolet rays, the organic solvent contained in the resist decomposes and evaporates. The resist itself causes a chemical reaction, and the resulting gas, or the gas generated from the surface treatment performed before applying the resist to the wafer, rapidly generates, leading to foaming.This foaming causes the resist to It is necessary to prevent damage and scattering to the surrounding area, but if you first irradiate the resist with weak UV light, it is possible to suppress foaming of the resist and gradually release the gas inside the resist. If an attempt is made to slow down the rotational speed to weaken the UV light and finish the exposure in one rotation with relatively weak UV light irradiation, the throughput of the exposure process will be long, which is impractical.

The present invention was made to solve these problems, and an object of the present invention is to provide a wafer peripheral exposure method that does not cause foaming of the resist and does not reduce throughput.

[Means for Solving the Problems] In order to achieve the above object, the method of the present invention is such that the rotation of the wafer or the light emitting mechanism is two or more rotations, and the first
The cumulative exposure amount per unit area during the second rotation is less than the resist foaming exposure amount.

The exposure process includes an exposure process such that the cumulative exposure amount from the second rotation and subsequent exposures is equal to or greater than a predetermined exposure amount.

[Function] According to the above method, during the first rotation exposure, the resist is exposed while suppressing foaming, and during the second rotation exposure, the exposure amount is greater than the resist foaming exposure amount, but the first rotation exposure After that, during the second and subsequent exposures, gas is released by the time the output end rotates to each part of the resist and does not remain inside the resist, so there is no possibility of foaming. .

[Embodiment] Fig. 1 is a schematic diagram of a wafer peripheral exposure apparatus for explaining an embodiment of the present invention, in which 2 is a rotation stage on which a wafer l is placed and rotated, and 4b is a rectangular exposure pattern. A certain irradiation part, 8 is a light guide fiber, 9 is this light guide fiber 8
The lens 10 is a mercury lamp which is a light source, 11 is an elliptical condenser mirror that collects light from the mercury lamp 10, and 12 is a reflection mirror from the elliptical condenser mirror 11. Further, the same reference numerals as in FIGS. 3 to 5 indicate the same or corresponding parts.

Furthermore, FIG. 2 is a time chart for explaining the wafer peripheral exposure method of the present invention using the apparatus shown in FIG. It shows the process.

Hereinafter, one embodiment of the present invention will be described in comparison with a conventional case using FIGS. 1 and 2.

In this embodiment, the resist applied to the wafer 1 is 0FPR8000 manufactured by Tokyo Ohka Chemical Co., Ltd., and the cysts are irradiated with light having a wavelength of 436 nm.

Now, by rotating the rotation stage 2, the first
The wafer 1 placed on the wafer 1 is rotated twice in 30 seconds using the S method, and the irradiation portion 4b, which is the output end of the light guide fiber 8, is irradiated with an exposure amount of energy of 2000''w8,'. In this exposure method, the wafer l was rotated once every 30 seconds with an exposure amount of energy of 2000'''w8♂ in the past, so the exposure time is the same as in this example, and the cumulative exposure amount (time integral The exposure amount) is the same, but as is clear from FIG. 2, the manner in which the exposure amount per unit area increases is different. Therefore, according to the conventional method, the resist foaming exposure amount (depending on the type of resist, but when a certain exposure amount is given to the resist for a predetermined time, the resist foaming energy: the second In contrast, according to the embodiment of the present invention, each part of the resist does not reach the bubbling exposure amount in the first rotation exposure of the wafer l, so that the light guide The exposure of each part of the resist is temporarily interrupted until the irradiation part 4b, which is the output end of the fiber 8, is exposed for the second rotation, and during this time, gas from each part of the resist is released and inside. Because it never accumulates.

There is no bubbling, and the exposure ends after the second rotation, but the overall exposure time is the same as in the conventional case, and the time-integrated exposure amount per unit area of the resist (
a3I exposure amount) is the same as the conventional one.

After the exposure is completed, development is performed using a well-known method to remove the resist on the wafer peripheral area 1b.

In the above embodiment, the wafer 1 is rotated by the rotation of the rotary stage 2, but it is of course possible to perform exposure by rotating the irradiation portion 4b, which is the exposure pattern, while the wafer 1 remains stationary. It is.

[Effects of the Invention] As described above, according to the present invention, there is a state in which exposure is interrupted during the exposure process of the resist, so that gas in the resist is released during that time.

Therefore, the rotation speed during each irradiation can be rather increased, resulting in no reduction in throughput, and since there is no foaming, the resist will not scatter to the pattern forming area of the wafer and disturb the pattern. There is no need to worry about producing defective products.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the periphery exposure device for UNIHA to explain an embodiment of the present invention, FIG.
Figure 3 is a perspective view of the case where υV (ultraviolet) light is guided by a light guide fiber and irradiated onto the wafer periphery, which is an unnecessary part of the resist applied to the semiconductor wafer, and Figures 4 (a) and (b).
) is a diagram showing a state in which light irradiation is performed for exposure using the method of FIG. 3, where (a) is a plan view, (b) is a side sectional view, and b) is U for the wafer periphery.
FIG. 3 is a diagram for explaining the exposure shape of v-light irradiation. In the figure. l: Wafer 2: Rotating stage l Mini pattern forming part lb: Wafer peripheral part 4b: Irradiation part 8: Light guide fiber

Claims (1)

[Claims] In a wafer peripheral exposure method, in which the peripheral part of the wafer is spot-wise irradiated with light while either the wafer or the light emitting mechanism is rotated to expose the resist in the peripheral part coated on the wafer, the wafer or the light emitting mechanism is rotated. The rotation is two or more rotations, and the cumulative exposure amount per unit area during the first rotation is less than or equal to the resist foaming exposure amount, and the second
A wafer periphery exposure method comprising an exposure step such that the cumulative exposure amount of exposure after the second rotation is equal to or greater than a predetermined exposure amount.