JPH0750676B2 - Wafer edge exposure method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer peripheral exposure method for removing unnecessary resist in a peripheral portion 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 of forming a circuit pattern on a semiconductor wafer, when forming a photosensitive resist film on a wafer, a spin coating method generally called a spin coating method is used. .

FIG. 3 is a perspective view in the case of irradiating the peripheral portion 1b of the wafer, which is an unnecessary portion of the resist applied on the semiconductor wafer, with UV (ultraviolet) light guided by a light guide fiber, and FIG. , (B) are views showing a state in which light irradiation for exposure is performed by the method of FIG. 3, in which (a) is a plan view and (b) is a side sectional view thereof.

In FIGS. 3 and 4, 1 is a wafer, and 1a is a pattern forming portion, which is used to expose a desired pattern (not shown) to a wafer 1 by reducing it to a fraction by a lens (not shown). , Reduction exposure method that repeats this exposure one after another (STEP AND R
A pattern is formed by the EPEAT method. Further, 1b is a peripheral portion of the wafer, 1c is a resist protruding portion, and 30 is a wafer 1.
Orientation flat (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 UV from this light guide fiber 8 '.
It is the irradiation part where light is irradiated, and the wafer 1 rotates,
The wafer peripheral portion 1b is irradiated with light.

The spin coating method for coating the resist on the wafer 1 is the fourth method.
The wafer 1 shown in FIG. 1A is placed on a rotary table, the resist is poured near the center of the wafer 1 and rotated, and the resist is applied to the entire surface of the wafer 1 by centrifugal force. However, according to the spin coating method, as shown in FIG. 4 (b), the resist causes the surface tension of the resist to protrude from the wafer peripheral portion 1b of the wafer 1 and to wrap around to the back side, and the resist is raised on the wafer peripheral portion 1b. It may happen. The wafer peripheral portion 1b of the wafer 1 is generally the fourth
As shown in FIG. 3B, the cross section has a bulge at the peripheral portion 1b of the wafer, and there is a high possibility that it will sneak to the back side due to the extra force. Moreover, since the circuit pattern is not formed on the wafer peripheral portion 1b on the front surface of the wafer 1 but on the other portion (pattern forming portion) 1a (see FIG. 3A), the wafer peripheral portion 1b is formed. There is no particular need to apply the pattern forming resist. However, in the spin coating method, the resist is inevitably applied to this portion as well. Conventionally, there has been proposed a spin coating method that eliminates the burr of the resist around the wafer, but even in that case, the coating of the resist on the wafer peripheral portion 1b remains.
Such unnecessary resist, that is, the resist protruding portion 1c that also wraps around on the back side shown in FIG. 4 (b) and the peripheral resist portion applied to the wafer peripheral portion 1b of the wafer 1 remain unresolved. May occur. Since the resist itself is generally characterized by the fact that the resin itself is hard and brittle, it will be removed if mechanical shock such as grasping or rubbing the wafer for transportation during the process is applied, and it will have an adverse effect as dust. Because there is. Especially during transfer of the wafer 1, the resist protrusion 1c of the wafer 1
A resist piece is missing from (see FIG. 4 (b)), which adheres to the wafer 1 and is not etched, resulting in pattern defects, or acting as a mask at the time of ion implantation so that necessary ion implantation is performed. It may be hindered and the yield may be reduced. Further, when high-energy and high-concentration ion implantation is performed, resist cracks may occur due to thermal stress generated from the periphery of the wafer during ion implantation. It has been confirmed that this resist crack is generated from an irregular portion or a flawed portion of the resist in the peripheral portion of the wafer and runs toward the center.

This problem is due to the progress of high density and high integration of semiconductor elements, and in order to maintain the yield, the conventional contact method or 1:
From the exposure method that uses a projection type aligner, the exposure method has changed to the reduction projection method called the above-mentioned step, and with it, instead of the negative type resist, which has been the main force in the conventional photoprocess for pattern formation, This is extremely important in the background that the use of positive resist has become obligatory.

As a method of removing the resist of such an unnecessary portion,
The solvent injection method is used. In this method, a solvent is sprayed from the back surface of the wafer 1 to which the resist is attached to dissolve the unnecessary resist. However, with this method, the resist in the resist protruding portion 1c shown in FIG. 4 can be removed, but the resist rising portion in the wafer peripheral portion 1b is not removed. Spraying the solvent from the surface to remove the resist on the wafer peripheral portion 1b may adversely affect the resist portion 1a on which the pattern is formed.

Although the above-mentioned inconvenience caused by the release of the resist piece is improved by removing the resist in the resist protruding portion 1c, it is still insufficient, and it is necessary to remove the resist in the wafer peripheral portion 1b as well. Therefore, as a method for easily and surely removing the unnecessary resist in this portion, UV light irradiation as shown in FIG. 3 has been conventionally performed. However, also in this UV light irradiation, the shape of the UV light irradiation portion on the wafer 1 was circular.

5 (a) and 5 (b) are for the wafer peripheral portion 1b.
The figure for explaining the exposure shape of UV light irradiation.
Shows the shape exposed by conventional light irradiation. As is apparent from FIG. 5 (a), the outer peripheral portion of the wafer peripheral portion 1b
The integrated exposure amount differs between 1b-1, the inner peripheral portion 1b-3, and the peripheral central portion 1b-2. As a result, the peripheral portion of the wafer 1 is exposed unevenly, and uniform resist removal cannot be performed after development.

Therefore, as shown in FIG. 5B, the exposure shape of UV light irradiation on the wafer peripheral portion 1b is made rectangular, and the integrated exposure at the outer peripheral portion 1b-1, the inner peripheral portion 1b-3 and the peripheral central portion 1b-2 is performed. I try to match the quantities.

Generally, the UV exposure of the resist applied to the wafer depends on the type of the resist, but usually when the film thickness is 2 μm.
It is necessary to irradiate 150 m ^J / cm ^2, and when the wafer peripheral part 1b rises to about 4 μm as shown in Fig. 4 (b), the required exposure dose is 300 m ^J / cm ² of UV light irradiation. It costs.

[Problems to be Solved by the Invention] As described above, in the conventional wafer edge exposure method,
If an exposure amount of 0 m ^J / cm ² is to be achieved by one rotation exposure, 300 m ^J / cm ² of light energy will be applied to the resist around the wafer in a short time, and the resist will foam. Resulting in. The reason for this is that when the resist is irradiated with ultraviolet rays, the organic solvent contained in the resist evaporates due to decomposition and the resist itself causes a chemical reaction, and the gas generated thereby or the underlayer applied before the resist is applied to the wafer. Gas, etc. generated from the treatment is suddenly generated, which leads to foaming. Therefore, it is necessary to prevent the resist from being damaged due to this foaming and scattering to the periphery.However, if weak UV light irradiation is performed first, the foaming of the resist can be suppressed and the gas inside the resist can be gradually released. it can. However, if a method is adopted in which the rotation speed is slowed to weaken the irradiation UV light and the exposure is completed in one rotation by relatively weak UV light irradiation, the throughput of the exposure processing becomes long, which is not practical.

The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a wafer peripheral exposure method in which the resist does not foam and the throughput does not decrease.

[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 integrated exposure amount per unit area at the time of the second rotation is less than or equal to the resist bubbling exposure amount, and the exposure process is such that the integrated exposure amount due to the exposure after the second rotation becomes a predetermined exposure amount or more.

[Operation] According to the above method, the exposure is performed while suppressing the bubbling of the resist during the exposure of the first rotation, and the exposure of the resist bubbling exposure amount or more is performed in the exposure of the second rotation. After the second and subsequent exposures, gas is not released and stays inside the resist before the emission end rotates to each part of the resist, so that no bubbling occurs.

[Embodiment] FIG. 1 is a schematic view of a wafer periphery exposure apparatus for explaining an embodiment of the present invention, in which 2 is a rotary stage for mounting and rotating the wafer 1, and 4b is a rectangular exposure pattern. A certain irradiation part, 8 is a light guide fiber, 9 is a lens mounted in this light guide fiber 8, 10 is a mercury lamp as a light source,
11 is an elliptical focusing mirror that focuses the light from the mercury lamp 10.
Reference numeral 12 is a reflection mirror from the elliptical focusing mirror 11. Also, the third
The same reference numerals as those in FIGS. 5 to 5 denote the same or corresponding parts.

Further, FIG. 2 is a time chart for explaining the wafer peripheral exposure method of the present invention using the apparatus of FIG. 1, the solid line shows the exposure process in the embodiment of the present invention, and the dot-dash line shows the conventional exposure process. Is shown.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2 in comparison with a conventional case.

In this example, OFPR8000 manufactured by Tokyo Ohka Co., Ltd. is used as the resist applied to the wafer 1, and the resist is irradiated with light having a wavelength of 436 nm.

Now, by rotating the rotary stage 2, the wafer 1 placed on the rotary stage 2 is rotated twice in 30 seconds, and the exposure amount of energy of 2000 mw / cm ² is applied to the light guide fiber 8.
Exposure is performed by irradiating from the irradiation portion 4b which is the emission end of the. In this exposure method, since the wafer 1 was rotated once every 30 seconds with an exposure amount of energy of 2000 mw / cm ² , the exposure time is the same as that of this embodiment, and the integrated exposure amount (time integrated exposure amount ) Is the same, but as is clear from FIG. 2, the way of increasing the exposure amount per unit area is different. Therefore,
According to the conventional method, the resist bubbling exposure amount at the first exposure of the resist at a specific position (the amount of bubbling energy when the exposure amount is given to the resist at a predetermined time, though it depends on the type of the resist): B) is reached. On the other hand, according to the embodiment of the present invention, in the exposure of the first rotation of the wafer 1, since each portion of the resist does not reach the bubbling exposure amount, the irradiation portion which is the emitting end of the light guide fiber 8 is next. The exposure of the resist of each part is temporarily interrupted until 4b comes and the exposure of the second rotation is performed. During this time, gas from each part of the resist is not released and does not accumulate inside, so that the foaming is not possible. Absent. Although the exposure is completed by the second and subsequent rotations, the entire exposure time is the same as in the conventional case, and the time-integrated exposure amount per unit area of the resist (integrated exposure amount) is the same as in the conventional case.

Then, when the exposure is completed, it is needless to say that the resist on the peripheral portion 1b of the wafer is removed by developing it by a known method.

Although the wafer 1 is rotated by the rotation of the rotary stage 2 in the above embodiment, the exposure may be performed by rotating the irradiation portion 4b which is the exposure pattern while the wafer 1 is stationary. Is.

[Effects of the Invention] As described above, according to the present invention, since the exposure is interrupted during the exposure process of the resist, the gas in the resist is released during that period. Therefore, the rotation speed at each irradiation can be rather increased, the throughput does not decrease as a result, and since there is no foaming, the resist does not scatter to the pattern forming portion of the wafer and disturb the pattern. There is no need to worry about defective products.

[Brief description of drawings]

FIG. 1 is a schematic view of a wafer peripheral exposure apparatus for explaining an embodiment of the present invention, and FIG. 2 is a time chart for explaining the wafer peripheral exposure method of the present invention using the apparatus of FIG.
FIG. 3 is a perspective view in which UV (ultraviolet) light is guided by a light guide fiber to irradiate the peripheral portion of the wafer, which is an unnecessary portion of the resist applied to the semiconductor wafer, and FIGS. 4 (a) and 4 (b). )
Is a diagram showing a state in which light irradiation for exposing by the method of FIG. 3 is performed. FIG. 5A is a plan view, FIG. 5B is a side sectional view thereof, and FIG. 5A and FIG. [Fig. 3] is a diagram for explaining an exposure shape of UV light irradiation on a peripheral portion of a wafer. In the figure. 1: Wafer, 2: Rotating stage 1a: Pattern formation part, 1b: Wafer peripheral part 4b: Irradiation part, 8: Light guide fiber

Claims (1)

[Claims] 1. A wafer peripheral exposure method for exposing a peripheral resist applied to a wafer by spotwise irradiating the peripheral part of the wafer with light while rotating either the wafer or a light emitting mechanism. Alternatively, the rotation of the light emitting mechanism is two rotations or more, and the integrated exposure amount per unit area during the first rotation is less than or equal to the resist bubbling exposure amount, and the integrated exposure amount due to the exposure after the second rotation. A wafer peripheral exposure method, which comprises an exposure step in which the exposure amount is equal to or more than a predetermined exposure amount.