JP2601309B2 - Wafer periphery exposure system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a wafer peripheral exposure apparatus for removing unnecessary resist from a semiconductor wafer coated with a photosensitive resist.

[Prior Art] Conventionally, in a technique of this kind, for example, a technique of forming a circuit pattern on a semiconductor wafer, when a photosensitive resist film is formed on a wafer, a spin coating method generally called a spin coating method is used. .

FIG. 3 is a perspective view showing a case where light is guided by a fiber to irradiate a peripheral portion of the wafer, which is an unnecessary portion of the resist applied to the semiconductor wear, and FIGS. 4 (a) and 4 (b) show the third embodiment. FIGS. 3A and 3B are diagrams showing a state in which light is irradiated to a wafer coated with a resist to be exposed by the method shown in the figure, wherein FIG. 3A is a plan view and FIG.

In FIGS. 3 and 4, reference numeral 1 denotes a wafer, and 1a denotes a pattern forming section, which is exposed to the wafer 1 by using a desired pattern (not shown) and reducing it to a fraction by a lens (not shown). , A reduction exposure method (STEP AND R
The pattern is formed by the EPEAT method. 1b is a peripheral portion of the wafer, 1c is a portion of the resist protruding, 1d is a wafer 1
An orientation flat portion (hereinafter referred to as an orientation flat) 3 is a light guide fiber for guiding light from an unillustrated irradiation light source, and 4a is an irradiation portion to which light is irradiated from the light guide fiber 3, and the wafer 1 rotates as the wafer 1 rotates. Light is irradiated to the wafer peripheral portion 1b.

In the spin coating method of applying a resist to the wafer 1, the wafer 1 shown in FIG. 4A is mounted on a turntable, and the resist is poured near the center of the wafer 1 and rotated. The resist is applied to the entire surface of the upper surface 1. However, according to this spin coating method, as shown in FIG. 4 (b), the resist may protrude from the wafer peripheral portion 1b, which is the side edge of the wafer 1, and may also reach the back side. In general, the peripheral portion 1b of the wafer is often rounded in cross section as shown in FIG. 4 (b), so that there is a great possibility that the peripheral portion 1b may go to the back side. Also, the circuit pattern is not formed on the wafer peripheral portion 1b on the surface of the wafer 1,
The other part (pattern forming part) 1a is formed (fourth
(Refer to FIG. 1A.) Therefore, it is not necessary to apply a pattern forming resist to the wafer peripheral portion 1b. However, in the spin coating method, a resist is inevitably applied to this portion. Conventionally, there has been proposed a spin coating method for eliminating burrs of the resist around the wafer, but even in such a case, application of the resist to the peripheral portion 1b remains. Such an unnecessary resist, that is, the resist protruding portion 1c which has also reached the back side shown in FIG. 4 (b) and the resist portion applied to the wafer peripheral portion 1b may cause a problem if it remains. is there.

Resists are generally characterized by the fact that the resin itself is hard and brittle, so if a mechanical shock is applied during the process, such as grabbing or rubbing the wafer during transport, it can be lost and become dust, which can have an adverse effect. Because there is. In particular, during transfer of the wafer 1, a resist piece is missing from the resist protruding portion 1c (see FIG. 4 (b)), which is a side edge of the wafer 1, and the resist piece adheres to the wafer 1 and is not etched. As a result, a pattern defect may be caused, or a necessary ion implantation may be inhibited by acting as a mask at the time of ion implantation, thereby lowering the yield. In addition, when high-energy, high-concentration ion implantation is performed, resist cracks (cracks) may occur due to thermal stress generated around the wafer during ion implantation. This resist crack is generated from the part where the resist on the wafer side edge is irregular or the part with the flaw,
It has been confirmed that it runs toward the center.

This problem is due to the advancement of high integration of semiconductor devices and the conventional contact method or 1:
(1) The exposure method using the aligner of the projection method has been changed to the reduced projection method called the above-mentioned stepper, and accordingly, instead of the negative type register, which has been a mainstay in the conventional pattern forming photo process, This is extremely important in the context of the necessity of using positive resists.

As a method for removing the unnecessary portion of the resist, a solvent injection method is used. In this method, a solvent is sprayed from the back surface of the wafer 1 on which the resist is attached, thereby dissolving unnecessary resist. However, in this method, the resist at the resist protruding portion 1c in FIG. 4 can be removed, but the resist at the wafer peripheral portion 1b is not removed. Injecting a solvent from the surface to remove the resist in the wafer peripheral portion 1b may adversely affect the resist portion 1a on which the pattern is formed.

The above-mentioned inconvenience due to the release of the resist pieces is improved by removing the resist at the resist protruding portion 1c, but it is still insufficient, and it is necessary to remove the resist at the wafer peripheral portion 1b. Therefore, light irradiation as shown in FIG. 5 has conventionally been performed as a method for easily and surely removing the unnecessary resist in this portion.

FIG. 5 (a) shows a state in which a projection lens 5 is provided at the end of the light emitting portion of the light guide fiber 3 to expose the periphery of the wafer, and FIG. 5 (b) shows a state after development after exposure. FIG.

In FIG. 5 (a), when exposing the periphery of the wafer 1, light from the light guide fiber 3
Then, the wafer peripheral portion 1b which is an unnecessary portion of the resist is irradiated and exposed, and the unnecessary portion of the resist is removed by a known developing method. According to the exposure method shown in FIG. 5A, the removal of the unnecessary resist is improved, but as shown in FIG. 5B, the pattern forming portion 1a and the peripheral portion of the wafer are removed.
The width d of the boundary area A with 1b is blurred and a sharp boundary cannot be formed. At the width d, the resist cannot be completely removed.

[Problems to be Solved by the Invention] Generally, the imaging performance of a lens is good near the optical axis, but tends to deteriorate as the distance from the optical axis increases toward the end. Irradiation light used for removing the unnecessary resist may use light of a single wavelength, for example, light of 436 nm.Therefore, when a lens is provided at the tip of the light emitting portion of the light guide fiber, the chromatic aberration of the lens is not so large. It is not necessary to make this a problem, but the image is blurred due to coma aberration or the like. In this case, there is a problem that the undesired resist remains in the boundary area A even after the exposure and development of the pattern forming section 1a due to blurring of the image, resulting in dust and the like.
Therefore, it is required that the blur of the image, that is, the width of the boundary area A in FIG. 5B be suppressed to as small as possible within 1 mm. However, even when a conventional wafer peripheral exposure apparatus is used, the width d of the boundary region A of the resist portion of the pattern forming portion is required when exposing the unnecessary resist around the wafer.
Is 1 to 2 mm, and it is difficult to satisfy the above requirements.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and a wafer peripheral exposure method capable of clearing a boundary between an exposed portion in a peripheral portion of a wafer and a pattern forming portion to reliably remove unnecessary resist. It is intended to provide a device.

[Means for Solving the Problems] In order to achieve the above object, a wafer peripheral exposure apparatus of the present invention has a plurality of lenses arranged between a rectangular emission end of an exposure wafer and the wafer. The optical axis of the lens coincides with the boundary between the peripheral portion of the wafer and the pattern forming portion,
Or one that is provided at a position substantially coincident with the other, and one end of the emission end of the light guide fiber is arranged on the optical axis, and the other end is arranged on the center side of the wafer with respect to the optical axis. It is.

[Operation] In general, it is known that the best focusing performance of a lens is the light that converges on a point on the optical axis on the image plane. This is because, among the aberrations due to the lens, only spherical aberration and chromatic aberration are a problem on the optical axis in the image plane, and other aberrations occur outside the optical axis. And the imaging performance tends to deteriorate.

In the present invention, by utilizing this property, the boundary between the pattern forming portion and the peripheral portion of the wafer is made to coincide with the optical axis of the lens, and the light applied to the boundary forms an image with the highest accuracy.

Then, one end of the light emitting end of the light guide fiber is arranged on the optical axis and the other end is arranged on the center side of the wafer so that the pattern forming portion is not unnecessarily irradiated with light.

Therefore, the exposure at the boundary between the pattern forming portion and the peripheral portion of the wafer is sharply performed, the blur is small enough not to cause a problem, and after development, only the unnecessary resist is completely removed. Also, the pattern formed on the wafer is not disturbed.

Embodiment FIG. 1A is a perspective view showing a schematic configuration of a main part of an embodiment of an apparatus for removing an unnecessary resist according to the present invention, and FIG. FIG. 6 is a diagram for explaining a fiber emission unit of FIG. In FIG. 1 (a), 8
Reference numerals 8 'and 8' denote cassettes, 10 and 10 'denote loader and unloader, respectively, and 10a and 10'a denote loader drive mechanisms and unloader drive mechanisms for sequentially driving the loader 10 and unloader 10', respectively. Numeral 12 denotes a transport belt which is driven integrally, 6 denotes a vertically movable and rotatable processing stage having a vacuum suction hole (not shown), and 7 denotes a center of the wafer which is arranged at a predetermined position on the wafer transport line by rotation and retracts. An output arm 11 is a stage controller for driving and controlling the processing stage 6, H is a spot light irradiation device, 3 is a light guide fiber attached to the spot light irradiation device H, 3a
Is an emission part of the light guide fiber, and 9 is a mounting base.

The control mechanism of FIG. 1A will be described. A cassette 8 containing a large number of wafers 1 is placed on a loader 10 and fixed. Next, the loader drive mechanism 10a operates to lower the loader 10 by a predetermined distance, and the wafer 1 to be processed is placed on the transport belt 12. Then, the transport belt 12 is driven to transport the wafer 1 above the processing stage 6. In the meantime, the wafer centering arm 13 rotates from the retracted position, and the centering side wall 13a is arranged at a predetermined value on the wafer transfer line. Then, the wafer 1 is conveyed by the conveyance belt 12, and hits the centering side wall 13a, so that the center of the wafer 1 and the center of the processing stage 6 are automatically almost coincident. In this state, after the processing stage 6 is raised and the wafer 1 is vacuum-sucked,
Lift slightly above the wafer transfer line. A photo sensor composed of a light emitting element and a light receiving element (not shown) detects the edge of the wafer 1 by the edge detecting mechanism of the wafer 1 and sends the result of the formation to the emitting unit 3a. When the stage rotates, predetermined exposure is performed following the edge of the wafer 1.

When the predetermined exposure of the wafer peripheral portion 1b is completed,
The emission unit 3a is retracted to the retracted position, the processing stage 6 is lowered, the wafer 1 is placed on the transport belt 12 again, and the vacuum suction of the processing stage 6 is released. Then the conveyor belt
When the wafer 12 transports the wafer 1 and carries it into the cassette 8 'mounted and fixed on the unloader 10', the exposure process for removing unnecessary resist of the present embodiment is completed. FIG. 1 (b) shows the exposure at the emission section 3a of the light guide fiber 3.
This will be described in detail with reference to FIG.

In FIG. 1 (b), the shape of the emission part 3a of the light guide fiber 3 is bundled in a rectangular shape, and 5a, 5b and 5c are projection lenses each composed of a convex lens, and are housed in a lens barrel 5 '. S denotes an optical axis of the projection lenses 5a, 5b, 5c (hereinafter collectively referred to as 5), and 1bt denotes a wafer peripheral portion 1b located immediately below the optical axis S of the projection lens group 5 and a pattern forming portion. The boundary of 1a is shown. The emission section 3a shown in FIG.
Is composed of a projection lens group 5 and a lens barrel 5 'for housing them. The same reference numerals as those in FIGS. 3 and 5 denote the same or corresponding parts.

FIG. 2 (a) is a plan view showing an exposure image when the peripheral portion of the wafer is irradiated according to FIG. 1, and FIG. 2 (b) is the same as FIG. 1 (a).
Is a side sectional view after development, and 4'a is an exposure image irradiated with light.

Since the image of the end of the light exiting portion 3a of the light guide fiber 3 is projected in reverse by the projection lens group 5, the image of the end of the light exiting portion 3a located on the center side from the optical axis is located outside the boundary 1bt. It is projected on the wafer peripheral portion 1b. At this time, since the boundary 1bt is located on the optical axis of the projection lens group 5, light having the least aberration is connected to the boundary 1bt, and blur of the image is minimized. In this case, the image at a position distant from the boundary 1bt is considerably blurred. However, since it is important to sharply remove the resist at the boundary, even if the blur is large, there is no problem at all.

Although the boundary 1bt on the optical axis is slightly affected by spherical aberration, a better result can be obtained by applying a known lens design technique for removing spherical aberration to the projection lens group 5.

However, by using the projection lens composed of only the convex lenses shown in FIGS. 1B and 1C, a very good result in which the width d shown in FIG. 5B is about 100 μm can be obtained. Was. This means that the optical system according to the present invention, that is, the exit end of the light guide fiber and the boundary of the exposure are firstly positioned with respect to the optical axis of the projection lens.
This is an effect due to the arrangement as shown in FIGS. 9B and 9C, that is, to make the boundary position of the exposed portion coincide with the optical axis position. Thus, the exposure performance could be remarkably improved by changing the optical arrangement of FIG. 5A as shown in FIGS. 1B and 1C.

2 (a) and 1 (a), when the wafer 1 is rotated by the rotation of the processing stage 6, the exposure image 4'a
Moves relative to the peripheral portion 1b of the wafer 1 and follows the edge of the wafer 1 by the servo mechanism described above.
Is exposed once. At this time, the boundary 1bt is exposed with high-resolution light having a very small blur as described above. Therefore, as shown in FIG. 2B, the resist in the peripheral portion 1b of the wafer, which is an unnecessary area, is sharply released after the development. As described above, the sharpness of the boundary is approximately equal to the d width in FIG.
100 μm.

FIG. 1 (c) is a view showing another embodiment of the fiber exit end of FIG. 1 (a), in which a convex lens 15 is added to the exit section of the light guide fiber 3, and the other structure is the same as that of FIG. This is the same as FIG. 1 (b), and the operation is basically the same as FIG. 1 (b).

The light emitted from the end of the emission part 3a of the light guide fiber 3 spreads with the maximum angle of incidence on the trend fiber 3 as the maximum angle. In this case, when the convex lens 15 is provided near the end of the emission part 3a as shown in FIG. 1C, the light beam expanding from the end of the emission part 3a is refracted in the optical axis direction, and the spread is suppressed. Therefore, as compared with the case of FIG. 1B, the diameter and thickness of the projection lens group 5 can be made smaller, and as a result, the lens barrel for housing these lenses can be made smaller, so It is effective for exposure processing.

Note that the unnecessary resist exposed in the above embodiment is removed by a known spray developing or other developing process.

[Effects of the Invention] As described above, according to the present invention, a plurality of lenses are arranged between the rectangular exit end of the light guide fiber and the wafer, and the optical axes of these lenses are aligned with the peripheral portion of the wafer and the pattern. It is provided at a position that coincides with or substantially coincides with the boundary between the forming portion, that is, the boundary between the portion to be exposed and the portion not to be exposed, or the boundary portion to remove the resist. On the other side, the other end has a configuration arranged on the center side of the wafer with respect to the optical axis, so that exposure with high imaging performance can be performed at the boundary where the resist is removed at the peripheral portion of the wafer, and after development, at the boundary, Sharp resist removal is performed. In addition, there is no unnecessary residual resist on the wafer and the pattern forming portion is not exposed.

[Brief description of the drawings]

FIG. 1 (a) is a perspective view showing a schematic configuration of a main part of an embodiment of an apparatus for removing an unnecessary resist according to the present invention, and FIG. 1 (b) shows a fiber emission section of FIG. 1 (a). FIG. 2 (c) is a view for explaining another embodiment of the fiber emitting portion of FIG. 2 (a), and FIG. 2 (a) is an exposure when the peripheral portion of the wafer is irradiated according to FIG. Plan view showing an image,
FIG. 3B is a side sectional view after development of FIG. 3A, and FIG. 3 is a case where light is guided by a fiber to a peripheral portion of the wafer, which is an unnecessary portion of the resist applied to the semiconductor wafer. FIGS. 4 (a) and 4 (b) are views showing a state before development in which light irradiation is performed on a wafer coated with a resist to be exposed by the method of FIG. 3, and FIG. FIG. 5 (a) is a plan view, FIG. 5 (b) is a side sectional view thereof, and FIG. 5 (a) is a view showing a conventional example in which a projection lens is provided at an end of an emitting portion of a light guide fiber to expose the periphery of a wafer. FIG. 2B is a view showing a state after exposure and development. In the figure. 1: Wafer 1a: Pattern forming part 1b: Wafer peripheral part 3: Light guide fiber 5, 5a, 5b, 5c: Projection lens 5 ': Lens barrel 6: Processing stage

Claims (1)

(57) [Claims] 1. A wafer peripheral exposure apparatus for exposing a peripheral portion of a wafer coated with a resist by irradiating light guided by a light guide fiber with a light, wherein a light is emitted between a rectangular emission end of the light guide fiber and the wafer. A plurality of lenses are disposed at positions where the optical axes of these lenses coincide with, or substantially coincide with, the boundary between the peripheral portion of the wafer and the pattern forming portion. A wafer edge exposure apparatus, wherein one end is disposed on the optical axis and the other end is disposed on the center side of the wafer with respect to the optical axis.