JPH0462167B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an exposure apparatus, and particularly to an exposure apparatus used for forming a photoresist pattern on a semiconductor wafer.

[Prior art]

Conventional exposure apparatuses are equipped with a mechanism in which the amount of exposure remains constant even if the intensity of the exposure light source changes with respect to a certain exposure setting value. However, even if the exposure time is kept constant, when processing materials whose surface reflectance tends to fluctuate, such as aluminum, there is a problem that large dimensional variations occur because the surface reflectance varies between wafers. Ta.

[Purpose of the invention]

An object of the present invention is to provide a semiconductor exposure apparatus that can reduce dimensional variations between wafers due to variations in reflectance on the wafer surface.

[Summary of the invention]

In order to achieve such an objective, the present invention
a light source that causes incident light to enter the object to be processed; and a first light source that detects the amount of the incident light of the light source.
a photodetector; a second photodetector that detects the amount of light reflected from the incident light on the object to be processed; and an exposure time setting means for setting an exposure time for exposing the object to be processed.

An exposure apparatus configured in this manner is useful when handling materials with different light reflectances on the object to be processed, or when handling materials with different light reflectances depending on the location even on the same object. In this case, the aim is to accurately control the exposure time by accurately detecting their light reflectance.

For example, when handling materials with different light reflectances, even if a photoresist formed on the main surface of the material is selectively exposed, the difference in light reflectance will result in a difference in the actual amount of exposure.

For this purpose, the present invention allows incident light to enter the object to be exposed, detects the amount of the incident light, detects the amount of reflected light of the incident light to the object, and detects the amount of light reflected from the incident light to the object to be processed. The exposure time for exposing the object to be processed is appropriately set according to the amount of reflected light relative to the amount of light.

The reason why we set the exposure time according to the amount of reflected light relative to the amount of incident light, rather than setting the exposure time according to the amount of reflected light only, is because the intensity of the light source of the incident light varies. The aim is to accurately set the exposure time without being affected by this.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. As is well known, the exposure apparatus includes an optical system, for example, a lens 17, which passes an exposure light beam from an exposure light source 1 into an image of a mask pattern placed inside a lens barrel 2 onto a wafer placed on a stage 3. 4, it is designed to be exposed to light for a certain period of time. The exposure time is determined by opening and closing the shutter 5.

The present invention includes two optical fibers 10A and 10B that guide the exposure light beam of the exposure light source 1 necessary for measuring the reflectance of the wafer 4 on the side surface of the lens barrel 2, and the light beams from the optical fibers 10A and 10B. Photodetector 11A, 11 that receives the signal and converts it into an electrical signal
B is provided. Said one optical fiber 10A
The light beam 12 emitted from the wafer 4 is reflected by the surface of the wafer 4 and is incident on one photodetector 11A. The light beam from the other optical fiber 10B is directly incident on the other photodetector 11B.

The outputs of the photodetectors 11A and 11B are input to a computer 14 via a differential amplifier 13. In order to obtain the same dimensions between the wafers 4, the computer 14 is set with a data file 15 in which the relationship between surface reflectance and exposure time is stored as shown in FIG. Further, the output of the computer 14 is input to a step motor 16 that drives the shutter 5.

Next, the effect will be explained. When the shutter 5 is closed, the exposure light beam from the exposure light source 1 is guided to the optical fibers 10A and 10B, and the light beam 12 emitted from one optical fiber 10A is reflected by the surface of the wafer 4 and enters one photodetector 11A. However, the light beam emitted from the other optical fiber 10B directly enters the other photodetector 11B.
The signal currents of these two photodetectors 11A and 11B are compared and amplified by a differential amplifier 13, and then input to a computer 14. The computer 14 calculates the surface reflectance based on the signal from the differential amplifier 13, the data file 15 extracts the exposure time corresponding to this surface reflectance, and outputs a shutter drive pulse corresponding to this exposure time. The step motor 16 is driven by this pulse to open and close the shutter 5, and the wafer 4 is exposed.

In this way, the surface reflectance of the wafer 4 is measured,
Since the optimal exposure time is calculated from the surface reflectance and the exposure is performed, dimensional variations among the wafers 4 can be eliminated. There are also two photodetectors 11A and 11B.
Since the surface reflectance of the wafer 4 is measured based on the difference between the signal currents, variations in the measured reflectance value due to variations in the light amount of the exposure light source 1 can be ignored.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to prevent dimensional variations between wafers due to variations in reflectance due to exposure light on the wafer surface, and to prevent dimensional variations, which are a major problem in semiconductor miniaturization. can be countered. Furthermore, since it is no longer necessary to advance one wafer during exposure and examine the relationship between reflectance and dimensions, through-prototyping can be improved and wafer production costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention, and FIG.
The figure is an explanatory diagram showing the relationship between surface reflectance and exposure time required to obtain the same dimensions. 1...Exposure light source, 3...Stage, 4...Wafer, 5...Shutter, 11A, 11B...Photodetector, 14...Computer, 17...
lens.

Claims (1)

[Claims] 1. A light source that causes incident light to enter the object to be processed, a first photodetector that detects the amount of the incident light from this light source, and a first photodetector that detects the amount of light reflected from the incident light on the object to be processed. a second photodetector; and an exposure time setting means for setting an exposure time for exposing the object to be processed according to the amount of light detected by the second photodetector relative to the amount of light detected by the first photodetector. An exposure device characterized by comprising: