JPH0287518A - Wafer peripheral exposure method - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention is applicable to rc, LS1. In the process of forming fine patterns in the processing of parts in other electronic devices, semiconductor substrates such as silicon wafers,
Alternatively, the present invention relates to a wafer periphery exposure method for removing unnecessary resist on the periphery of a resist coated on a substrate such as a dielectric, metal, or insulator through a development process.

[Prior Art] In the manufacturing process of ICs, LSIs, etc., when forming fine patterns, a resist is applied to the surface of a silicon wafer, etc., and then exposed and developed to form a resist pattern. Next, processes such as ion implantation, etching, and lift-off are performed using this resist pattern as a mask.

Usually, resist is applied by a spin code method. In the spin code method, the wafer is rotated while resist is poured onto the center of the wafer surface, and the resist is applied to the wafer surface using centrifugal force. However, according to this spin code method, the resist sometimes protrudes from the periphery of the wafer and wraps around the back side of the wafer.

FIG. 2 is a partial cross-sectional view of the wafer showing the resist that has gone around to the back side of the wafer, where l is the wafer, IP is the wafer peripheral area, 1a is the resist in the pattern forming area, and ■b is the wafer peripheral area IP. It shows the resist on the front surface, lc, or the resist that has gone around from the edge of the wafer l to the back side. The resist IC that has gone around to the back side is not irradiated during the exposure process for pattern formation, and in the case of a positive resist, remains even after development.

FIG. 3 is a diagram showing the shape of a circuit pattern exposed on a wafer. One area indicated by T corresponds to one circuit pattern. In most cases, circuit patterns cannot be drawn correctly around the wafer, and even if they can be drawn, the yield is poor. The resist lb at the periphery of the wafer is almost unnecessary for forming a circuit pattern. Incidentally, even if the periphery of the wafer is exposed as shown in FIG. 3, the resist remains after development.

Unwanted resist remaining from the surface and edges of the wafer to the front side of the wafer periphery causes the following problems. That is, wafers coated with resist 41 are transported through various processing steps and in various ways. At this time, the periphery of the wafer is mechanically grasped and held, or the periphery of the wafer slips against the wall of a container such as a wafer cassette.

At this time, if the unnecessary resist from the periphery of the wafer is removed and adheres to the pattern forming area of the wafer, it will not be possible to form a correct pattern and the yield will be lowered.

Unnecessary resist remaining on the wafer periphery becomes "dust" and reduces yield, which has become a serious problem, especially now that integrated circuits are becoming more sophisticated and smaller.

Therefore, in order to remove unnecessary resist remaining on the periphery of the wafer even after such development, a technique of removing it by a solvent spraying method has been put into practical use.

This method involves injecting a solvent from the back side of the wafer periphery to which resist has been applied to dissolve unnecessary resist. However, with this method, although the resist IC in the protruding portion shown in FIG. 2 can be removed, the unnecessary resist 1b on the surface of the wafer periphery is not removed. Even if a solvent is sprayed from the surface of the wafer l in order to remove the unnecessary resist lb on the surface of the wafer periphery, not only will the problem of solvent splash occur, but also the unnecessary resist lb on the surface of the wafer periphery will be removed. It is not possible to sharply and controllably remove only the unnecessary resist from the boundary portion between the pattern forming portion and the resist 1a, which is a resist necessary as a mask layer during etching, ion implantation, etc.

Therefore, in recent years, apart from the exposure process for pattern formation, a separate exposure process has been carried out to remove unnecessary resist on the wafer's 14 sides by performing a development process.

This wafer periphery exposure method can be used to sharply control the boundary between the unnecessary resist lb on the surface of the wafer periphery in FIG. It removes well,
Superior to solvent injection method.

[Question 8 to be solved by the invention] In the conventional wafer peripheral exposure method as described in 1-1, if the resist is irradiated with strong ultraviolet rays from the beginning, the organic solvent contained in the resist will decompose and the resist will evaporate and the resist will be exposed. Gas and the like generated by the photochemical reaction of the resist itself may not be sufficiently released to the outside of the resist, resulting in bubbles within the resist.

If this foaming occurs, the foamed portion rubs against the wafer cassette and scatters, and the scattered resist becomes dust and adheres to the pattern forming area of the wafer, causing the aforementioned pattern defect problem.

The present invention has been made to solve these problems, and it is an object of the present invention to provide a solid-edge exposure method for sea urchins that does not cause foaming from the resist, has no pattern defects, and has a high yield.

[Means for Solving the Problem] In order to achieve the above object, the wafer peripheral exposure method of the first invention of this application irradiates the same irradiation area with light guided by a light guide fiber. Irradiation is performed two or more times, and the illuminance of the light in the wavelength range necessary for the first exposure is lower than the illuminance of the light in the wavelength range necessary for the second and subsequent exposures. In the second invention, the first invention is carried out while the wafer is in a heated state during at least the first irradiation.

[Function] According to the present invention, when the resist is first irradiated with light of low intensity, the gas generated from inside the resist is not concentrated in one place but is gradually released to the outside of the resist, thereby preventing the resist from foaming. do not have. Furthermore, for the second and subsequent exposures, even if the light is irradiated with strong illuminance, most of the gas will be released during the first exposure and no bubbles will form, so it is possible to increase the rotation speed and shorten the exposure time. can.

[Embodiment] FIG. 1 is a diagram showing a schematic configuration of the main parts of an exposure apparatus for carrying out a wafer peripheral exposure method which is an embodiment of the present invention.

In FIG. 1, l is a wafer to which peripheral exposure is performed, 2 is a stage on which this wafer l is placed, 3 is a stage drive system that rotates stage 2, 4 is a system controller, and 5 is a conveyor for transporting wafer 1 to stage 2. wafer transport system for
6 is a shutter actuator; 7 is a shutter that is opened and closed by the shutter actuator 6; 8 is a neutral density filter actuator; 9 is a neutral density filter composed of a metal mesh or the like that controls the transmittance of light to be exposed;
0 is a light guide fiber that guides the light to be exposed, 11 is the output end of this light guide fiber 10, 12 is a plane reflecting mirror, 13 is an elliptical collector mirror, and 14 is a short arc discharge lamp (hereinafter referred to as a lamp). Yes, the shutter actuator 6 and the neutral density filter actuator 8 may be constituted by, for example, a rotary solenoid.

A specific example of an exposure method using the exposure apparatus shown in FIG. 1 will be described below.

First, in response to a signal from the system controller 4, the wafer transport system 5 transports the wafer l and places it on the stage 2 a. On the stage 2 on which the wafer 1-a is placed, a vacuum chuck mechanism (not shown) starts to operate and vacuum-chucks the wafer 1 on the stage 2-a. Thereafter, the stage 2 starts rotating, and the shutter actuator 6 opens the shutter 7 based on a signal from the system controller 4, but the neutral density filter 9 located in the irradiation optical path remains in the same position, and the light from the lamp 14 is removed. is attenuated and the light guide fiber 10
The light is emitted from the light emitting end 11 of the wafer 1, and the periphery of the wafer 1 is exposed for the first time while the wafer 1 is rotated once.

The completion of one rotation of the wafer l from the start of light emission from the light guide fiber 10 is detected by a detection means (not shown) (for example, by counting the pulses of a pulse motor used in the stage drive system 3 or by providing a rotary encoder). After confirming this with the following steps, the stage 2 continues to rotate in order to perform the second exposure. During the second exposure, the neutral density filter actuator 8 operates the neutral density filter 9 based on the signal from the system controller 4.
is moved out of the irradiation optical path. Regarding other mechanisms, open the shutter 7 in the same way as for the first exposure, and open the exit end 1.
From step 1 onwards, the periphery of the wafer l is exposed to light with stronger illuminance.

After the two exposures are completed, the wafer 1 is transported from the stage 2 to another location by the wafer transport system 5, and developed by known means to remove the resist around the wafer.

FIGS. 4(a) and 4(b) show the respective illuminances for the first and second and subsequent times.

In this example, the illuminance of the light during the first and second exposures was made weaker at the first time and stronger at the second time by adjusting the neutral density filter 9. Using a 2-pot thick phenol novolac positive resist, the illumination intensity for the first exposure was set to 200'', and the illumination intensity for the second exposure was adjusted to 2000''.

However, it goes without saying that the illuminance, exposure time, and rotation speed each time vary somewhat depending on the material of the resist.

In the above example, when the wafer temperature is maintained at 100°C for exposure, no firing occurs even if the first illuminance is increased to 100°C, and the first exposure time is about 30°C. This can be reduced to one-fold.This is because as the temperature increases,
This is because gas generated by exposure quickly diffuses within the resist and is released to the outside of the resist.

Note that the heating temperature needs to be lower than the resist temperature.

Moreover, unlike the method of performing exposure once for each rotation as in the above embodiment, multiple light guide fibers are used during one rotation as shown in FIG. 5(b), and these fibers are Exposure may be performed continuously by shifting the positions and times from each other.

However, in this case, the illuminance of the light used for the first exposure must be lower than the illuminance of the light used for the next exposure, and the resist must be prevented from foaming due to the first exposure.

As the illuminance adjustment means, in addition to a neutral density filter, it is also possible to adjust the power supplied to the lamp or use a dichroic mirror.

[Effect of Irradiation II] As explained above, in the wafer peripheral exposure method of the present invention, the irradiation with the light guided by the light guide fiber is performed twice or more with a time interval, and the first irradiation light is The illuminance was set to be weaker than the illumination intensity of the light irradiated from the second time onward, so there was no foaming of the resist, which resulted in a good product yield. It can be improved by increasing .

[Brief explanation of drawings]

FIG. 1 is a diagram showing a schematic configuration of the main parts of an exposure apparatus for carrying out a wafer peripheral exposure method, which is an embodiment of the present invention, and FIG. FIG. 3 is a diagram showing the shape of the circuit pattern exposed on the wafer, and FIG. 7iSA is a diagram showing the relationship between illuminance and wafer rotation angle in the exposure method of the present invention. This figure shows a case in which each exposure is performed intermittently, and FIG. 6(b) shows a case in which each exposure is carried out continuously. In the figure. Wafer stage Stage drive system system controller Wafer transport system Shutter actuator Shutter Neutral density filter actuator Neutral density filter Light guide fiber 11: Output end 12: Flat reflector 13: Elliptical condenser mirror 14 Lamp agent Patent attorney 1) Haruichi Kitatake Figure (α) Figure Figure Figure Figure

Claims (2)

[Claims] (1) In a wafer peripheral exposure method in which the wafer is exposed by irradiating light guided by a light guide fiber onto the periphery of the wafer while rotating the wafer, when irradiating the wafer with light guided by the light guide fiber, the same irradiation area is irradiated two or more times, and the illuminance of the light in the wavelength range necessary for the first exposure is made weaker than the illuminance of the light in the wavelength range necessary for the second and subsequent exposures. Wafer peripheral exposure method. (2) In a wafer peripheral exposure method in which the wafer is exposed by irradiating light guided by a light guide fiber onto the wafer periphery without rotating the wafer, when irradiating the wafer with the light guided by the light guide fiber, the same irradiation The area is irradiated two or more times, and the wafer is heated during at least the first irradiation, and the illuminance of light in the wavelength range necessary for the first exposure is irradiated from the second time onwards. A wafer peripheral exposure method characterized by reducing the illuminance of light in the wavelength range necessary for exposure.