JPS58122726A - Manufacture of semiconductor element by close control of resist dimension - Google Patents

Abstract

PURPOSE:To uniform the width dimension of a resist pattern over the whole surface of a wafer, by a method wherein a photoresist film substantially uniformly applied is exposed to light in such a step-and-repeat manner that the exposure time is gradually varied from the peripheral areas toward the center. CONSTITUTION:A positive photoresist is rotationally applied to an Si wafer having a diameter of about 100mm. and provided with an SiO2 film. As a result, a resist film is formed having a film thickness varying from the center toward the peripheral edges. After prebaking, an exposure is effected while the exposure time is gradually decreased from the peripheral edge areas toward the center with a step pitch of 10mm.X10mm., for example, so that the exposure time is 0.2sec in the center and is 0.4sec at the peripheral edge areas. The longer the exposure time, the smaller in width of the positive resist pattern. Therefore, by carrying out exposure and development according to this constitution, the resist pattern width can be unifored over the whole surface. In the case of a negative photoresist, it will suffice to reverse the exposure time.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention This invention relates to IC-? The present invention relates to a method for manufacturing semiconductor devices such as LSI, and more specifically to a photolithography process for performing microfabrication.

Technical Background of the Invention Recently, in IJ lithography, patterns have become finer to improve the degree of integration of devices, and as resolution and dimensional accuracy become more important, the photoresists used have changed from negative to negative type. The shift was to positive type, and the exposure equipment used was contact type and l:1 grossiex.

In addition to the step-and-repeat method, the step-and-repeat method has started to attract attention.

In addition, coating equipment can be roughly divided into a dip method and a spray method, but the dip method is prone to defects such as uneven coating and resist residue within the wafer surface and between wafers, and is difficult to automate. Because of these drawbacks, automated spray-only equipment is often used.

Problems with the Background Art However, in the case of the current one-spray method, there is a problem in that the width dimension of the resist pattern is different between the center portion and the peripheral portion of the wafer. In other words, in the case of a positive resist, the width of the resist pattern at the center compared to the periphery is
The width dimension of the remaining pattern becomes smaller, and the width dimension of the punching pattern becomes larger.

This problem is considered to be closely related to the following phenomena (i) and (ii).

(i) In the spray type, the developer is generally sprayed without rotating the wafer, so the center of the wafer is exposed to more developer than the periphery, and the development speed in the center is faster. .

(if) In order to keep the developer temperature constant, it should not be higher than room temperature.
In this case, the temperature at the periphery tends to drop more easily than at the center, and the developing speed at the periphery becomes slower.

This variation in width due to different development speeds is a major cause of a decrease in device yield, especially in the case of fine patterns. In particular, since the development speed of positive resists is more susceptible to development conditions than that of negative resists, this poses a particularly serious problem when positive resists are used.

FIG. 1 is a diagram showing a conventional manufacturing method (that is, after applying a positive resist, the entire surface of the sea urchin is exposed for the same exposure time, and then developed using a spray method). In the figure, the horizontal axis represents the distance d(m)i from the center of the wafer, and the vertical axis represents the width dimension t (μmyt) of the resist pattern. From this figure, it can be seen that according to the conventional manufacturing method, the development speed is relatively low in the central part. On the other hand, the developing speed at the peripheral edge portion is relatively slow, and it can be seen that the width dimension of the resist pattern varies.

Purpose of the Invention An object of the present invention is to provide a novel semiconductor device manufacturing method that eliminates variations in the width dimension of resist patterns formed in one-way spray development (including one-way shower development). Summary of the Invention The method for manufacturing a semiconductor device of the present invention was developed by focusing on the fact that the width of a resist pattern changes depending on an increase or decrease in exposure time. In other words, in the resist coating process, a photoresist film that is almost uniformly applied to the surface to be coated is formed into a resist pattern by a spray or shower development process, but variations in the width of the resist pattern are removed in the fog light process. This is an attempt to compensate and eliminate the variation by performing step-and-repeat exposure in which the exposure time is gradually changed from the periphery to the center of the surface to be coated.

The relationship between the width dimension of the resist pattern and the exposure time differs depending on the type and material of the resist. For example, in the case of a positive resist, the graph in Figure 2 [the horizontal axis is the exposure time T (see)]
, the vertical axis represents the width t (μm) of the resist pattern] As shown in K, the width of the resist pattern decreases as the exposure time increases, and this fact can be utilized to increase the width of the resist pattern by development. By reducing the exposure time for the center of the wafer, where the width is small, and increasing the exposure time for the periphery of the wafer, where the width of the resist pattern is large, the width of the resist pattern can be reduced over the entire wafer. can be kept constant. In the case of a negative resist, this process may be reversed.

By the way, in the step-and-repeat method of exposure, the exposed surface is divided into reduced projected exposure areas and a mechanism for repeated exposure is provided.
It was only used to reduce the number of defects and improve accuracy by correcting alignment and focus, and as in this invention, the exposure time is changed for each step to eliminate variations in the width dimension of the resist pattern. It had never been used like that.

In this invention, the photoresist is applied almost uniformly to the surface to be coated. The force that causes variations in the width dimension of the resist pattern due to variations in the coating film thickness; the variation in the width dimension of the resist pattern due to this cause is usually applied by rotating the wafer/tube, so the resist pattern width varies from the periphery to the center of the wafer. Since this phenomenon occurs gradually, it can be compensated for by this invention.

The developing step in this invention is carried out by spraying or showering. A feature of these methods is that the object to be developed rotates. Normally, in the spray type, the developer is sprayed with N2 gas or the like, and in the shower type, the developer is pressurized with N2 gas or the like, so that the developer is spouted from a nozzle and sprayed onto the object to be developed.

In addition, photolithography in semiconductor device manufacturing refers to a process in which photolithography is applied, and can be understood to include cases in which it is applied not only to semiconductor wafers but also to mask blanks. It must be.

Next, one embodiment of the present invention and its specific effects will be explained.

EXAMPLE OF THE INVENTION A silicon wafer having a diameter of 100 ff and having an oxide film having a thickness of 4000× was coated with a positive photoresist to a thickness of 1.5 tones, and then prebaked at 90° C. for 10 minutes. Next, in the exposure process, with a step pitch of 10M x 101nI, the exposure time was 0.2 seconds for the chips at the center of the wafer, and 0.2 seconds for the chips at the periphery of the wafer.
Exposure was carried out in a step-and-repeat manner using a reduced projection type exposure apparatus while gradually decreasing the exposure time from the wafer periphery toward the wafer center so that the exposure time was 4 seconds. After the exposed wafer was developed using a spray method, the width distribution of the resist pattern was measured, and it was found that the difference in width between the center and peripheral portion of the wafer was only 0.06 μm or less. In addition, the width measurement values obtained by performing the same test on a population of statistically reliable size were compared with the width measurement values obtained using the conventional method (i.e., step-and-repeat method with the same exposure time on the entire surface). , the standard deviation is 0.10/IWi in the conventional method, whereas the present invention has a uniform pattern size over the entire surface of the wafer, as described above. As a result, a novel semiconductor device manufacturing method is provided that can improve chip yield. Furthermore, according to this invention, it is not necessary to fundamentally improve the developing device or the resist coating device, etc., and the currently used reduced-size projection exposure device can be used. is not necessary,
Therefore, a large cost-effectiveness can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the distribution of resist pattern width dimensions on a wafer obtained by a conventional manufacturing method, and Fig. 2 is a diagram showing the facts that form the basis of this invention.Patent applicant: Tokyo Shibaura Electric Co., Ltd.

Claims (1)

[Claims] 1 In photolithography in semiconductor device manufacturing, photoresist is applied to the surface to be coated in the resist coating process, and in the exposure process, the exposure time is gradually changed from the periphery to the center of the surface to be coated. A method for manufacturing a semiconductor device, characterized by performing and-repeat exposure.