JPS60177623A - Exposure device - Google Patents

Abstract

PURPOSE:To perform uniform patterning on a wafer with high precision by a method wherein light of the same wavelength with exposing light is projected to the wafer, and the exposing condition is measured from intensity of reflected light to control exposing intensity and time length required. CONSTITUTION:A light source 12 is lighted, the alignment marks of a wafer 3 and a reticle 2 are recognized 14 utilizing reflected light of the wafer 3, and an X-Y table 4 is driven to perform positioning. The reflected light intensity signal of a sensor 13 is inputted to a control part 16 at the same time, compared with stored informations, resist film thickness and reflectivity of the substrate are calculated 17, the most suitable exposing condition is calculated 18 from relation between data thereof and pattern size, and control of the amount of exposure 19 (opening time of a shutter 7, intensity of a light source 8) is performed. As a result, because the most suitable condition can be set at every alignment or exposure, respective pattern sizes can be controlled uniformly with high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to exposure technology, and particularly to technology that can expose semiconductor device patterns with high precision.

[Background technology]

The so-called IJ lithography technology is used in the element pattern forming process during the manufacture of semiconductor devices, in which a film of photoresist (photosensitive resin) is applied to the surface of the semiconductor substrate on which the element pattern is to be formed, and then the desired pattern is formed on this. By exposing and developing the photoresist mask, a photoresist mask having the pattern described above can be formed, and this can be used to perform selective diffusion and selective etching onto a semiconductor substrate. Therefore, as the accuracy of the diffusion dimensions and etching dimensions to be formed increases, it is necessary to improve the dimensional accuracy of the photoresist pattern accordingly. For example, when forming a pattern width of 2μ, ±0
．． Dimensional accuracy of approximately 2μ is required.

By the way, when exposing this photoresist,
It is known that the exposure amount and photoresist film thickness have a large effect on pattern dimensions. In particular, when exposing fine patterns, monochromatic light such as G-line is used to increase resolution, so depending on the thickness of the photoresist, a standing wave effect occurs due to light interference, as shown in Figure 1. Dimensional variations occur as shown.

In other words, it can be seen from FIG. 1 that even a slight change in the photoresist film thickness causes a large change in dimensions.

Similarly, variations in the reflectance of the photoresist underlayer cause the dimensions to change, as can be seen in FIG.

Therefore, in order to control the dimensions with high precision in this photolithography technology, it is necessary to measure the photoresist film thickness and the reflectance of the underlying layer, and adjust the exposure amount to the optimum amount based on the measurement results. be done. For this reason, it is conceivable to adopt a method of measuring the photoresist film thickness and underlayer reflectance in a pre-exposure step, and setting the exposure intensity and exposure time of the exposure device based on the results to perform exposure.

However, in this type of method, the exposure amount must be set artificially, so the first semiconductor substrate (wafer) of each lot or several lots must be
Measurements and corresponding settings are made only for
The following wafers must all be exposed under the same conditions. For this reason, this method cannot deal with process variations not only between lots but also within lots and within wafers, creating the problem that it is difficult to uniformly form highly accurate dimensional patterns. was revealed by the present inventor.

[Purpose of the invention]

The purpose of the present invention is to automatically set the optimum exposure amount and immediately perform exposure under these conditions, thereby enabling optimum exposure for each pattern and realizing patterning with high dimensional accuracy. Our goal is to provide exposure technology.

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

In other words, there is a means for projecting the same wavelength as the exposure light of the exposure device onto the wafer and measuring the intensity of the reflected light, and a means for calculating the exposure conditions from the intensity of the reflected light, and determining the exposure intensity and exposure time of the exposure device based on the calculated conditions. By adding a control means, it is possible to automatically perform exposure under the optimum exposure conditions for each exposure of each pattern, thereby making it possible to form a uniform pattern with high dimensional accuracy. .

〔Example〕

FIG. 3 shows an overall configuration diagram of an exposure apparatus which is an embodiment of the present invention. In the figure, l is an exposure device exemplified by a 1:10 reduction type projection aligner, and a reticle 2
The pattern can be reduced to 1=10 and exposed onto the wafer 3. That is, this exposure apparatus 1
XY where you can place C3 on top and move this in the X, Y, and θ directions
It has a stage 4, and a 1:1 degree reduction projection lens 6 and a shutter 7 are disposed above the stage 4 between it and a reticle support frame 5 that supports the reticle 2. Also, above the reticle support frame 5 is a light source 8 that emits a G-line.
and a condenser lens 9 are arranged on the same optical axis to illuminate the reticle 2 and transfer the reticle pattern to the wafer 3.
It's projected onto the top.

On the other hand, a mirror 10 is provided in the vicinity of the reticle support frame 5, and a half mirror 11 and an alignment light source 12 are arranged on the sides of the mirror 1o to face it, and an optical sensor 13 such as a CCD is arranged at a right angle thereto. It is set up. The alignment light source 12 emits alignment light of the same wavelength as the exposure light, but with low intensity. This light is projected onto the wafer 3 through the reticle/I/2, and the reflected light is passed through the reticle 2 again. Mirror 10. The light is reflected by the half mirror 11 and received by the optical sensor 13. A pattern recognition circuit section 14 is connected to the optical sensor 13, and the pattern recognition circuit section 14 can recognize each alignment mark (not shown) on the wafer 3 and the reticle 2 by the reflected light from the wafer 3, and the recognition result can be recognized by the pattern recognition circuit section 14. In other words, relative positioning (alignment) of wave 3 and reticle 2 so that both alignment marks match based on
XY stage drive circuit 15 so that
Drive the Y stage 4.

Furthermore, the optical sensor 13 measures the light reflection intensity, generates an electric signal according to the intensity, and detects the photoresist film formed on the surface of the wafer 3 based on the difference between the light reflection intensity and the alignment light source intensity. A control unit 16 is connected to the controller 16, which includes a first calculation circuit 17 that calculates the film thickness and base layer reflectance, and a second calculation circuit 18 that calculates appropriate exposure conditions from the calculation results. That is, the second arithmetic circuit 1
8 stores the characteristics shown in FIG. 1 and FIG. In each case, the exposure amount, and more specifically the conditions such as exposure intensity and exposure time, are calculated. Based on this calculation result, the controller 19 in the control section 16 can control the intensity of the light source 80 and the shutter 7 of the exposure apparatus 1.

According to the above configuration, prior to exposing the reticle pattern onto the wafer 3, the alignment light source 12 is turned on to project alignment light onto the wafer 3, and the reflected light is used to illuminate each of the wafer 3 and the reticle 2. The alignment mark is detected by the pattern recognition device 14, and based on this
By operating the XY stage 4, the relative positioning of the wafer 3 and reticle 2 is completed. At this time, in parallel with this, the reflected light intensity signal from the optical sensor 130 is input to the first arithmetic circuit 17 of the control section 16, where it is compared with the stored data to determine the photoresist film thickness and base layer reflectance. It will be done. The relationship between this film thickness and reflectance and the required pattern dimensions (see Figures 1 and 2)
The second arithmetic circuit 18 calculates the optimum exposure conditions from FIG. In this case, if either the exposure intensity or the exposure time is fixed, the exposure amount is controlled by changing the other, and the opening time of the shutter 7 or the luminous intensity of the light source 8 is controlled as appropriate. Of course,
You can also control both at the same time. As a result, regardless of variations in photoresist film thickness or underlayer reflectance, suitable conditions can be set for each alignment, that is, each exposure, and the dimensions of each pattern can be managed uniformly and with high precision. Therefore, it is possible to obtain uniform pattern dimensions with high precision not only within a wave but also within the same lot and between lots. Note that the first arithmetic circuit and the second arithmetic circuit may be configured as one arithmetic circuit.

〔effect〕

(1) means for causing a part of the exposure apparatus to project light of the same wavelength as the exposure light onto the wafer and measuring the reflection intensity;
It is equipped with a means to calculate exposure conditions from the intensity of this reflected light and automatically control the exposure equipment according to the exposure conditions based on the results, so the photoresist film thickness and base layer reflectance can be adjusted for each pattern exposure. It is possible to measure and set the optimum exposure conditions for each case, thereby making it possible to obtain a pattern with uniform dimensions with high precision.

(2) The reflection intensity measuring means for measuring the photoresist film thickness and underlying layer reflectance is configured to double as an alignment device that performs relative positioning of the reticle and wafer, so it is easy to control the existing equipment. The device of the present invention can be configured by simply attaching it, and the configuration can be simplified and the cost can be reduced.

(3) Since the exposure conditions can be automatically set for each pattern exposure, it is possible to follow variations in photomask film thickness and underlayer reflectance not only between wafer lots, but also within the same lot, and even between each TIG pattern on the same wafer. This allows suitable exposure to be completed.

(4) To measure the reflection intensity, by using an alignment light source with the same wavelength as the exposure light, the resist film thickness and underlayer reflectance can be determined at the same time as wafer alignment, and the optimal exposure conditions can be determined. Since the settings can be made, it is possible to achieve the effect of enabling highly accurate exposure without affecting throughput.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. Nor. For example, the means for measuring the reflection intensity on a wafer is installed in a pre-alignment device installed as a pre-process device of an exposure device, and the measurement results are memorized here, and the measurement results can be quickly set under the optimal conditions during exposure. It may also be possible to perform exposure at . Further, in the case of the above embodiment, a part of the exposure light source may be used to measure the photoresist film thickness and the underlying layer reflectance, and furthermore, a part of the exposure optical system may be used at this time. good.

[Application field]

In the above explanation, the invention made by the present inventor was mainly applied to an exposure apparatus for manufacturing semiconductor devices, which is the background field of application, and in particular an exposure apparatus for wafers, but the present invention is not limited thereto. Of course, exposure to things other than wafers, such as masks, etc.
It can also be applied to equipment other than semiconductor manufacturing equipment.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the correlation between photoresist film thickness and dimensions, FIG. 2 is a diagram showing the correlation between base layer reflectance and dimensions, and FIG. 3 is a diagram showing the overall configuration of the exposure apparatus of the present invention.

Claims (1)

[Claims] 1. An apparatus for exposing a wafer having a film such as a photoresist formed on the surface thereof to light to form a desired pattern, the apparatus projecting light having the same wavelength as the exposure light onto the wafer surface; An exposure apparatus comprising means for measuring the reflected light intensity, and means for calculating optimum exposure conditions from the reflected light intensity and controlling the exposure apparatus according to the calculated conditions. 2. The exposure apparatus according to claim 1, wherein the means for controlling the exposure apparatus comprises a control circuit for controlling the exposure intensity or exposure time of the exposure apparatus. 3. The exposure apparatus according to claim 1 or 2, wherein the means for measuring the reflection intensity utilizes a part of the alignment light or exposure light of a wafer alignment mechanism attached to the exposure apparatus.