JP2847915B2 - Projection exposure apparatus and its exposure method - Google Patents

Description

The present invention relates to a projection exposure apparatus for forming a pattern of a semiconductor device and an exposure method therefor, wherein an effective focus is provided when a fine pattern is projected and exposed on an object to be exposed having a large surface step. It is an object of the present invention to provide a projection exposure apparatus capable of securing a depth and an exposure method therefor. [1] A ray emitted from a mercury lamp is reflected by an elliptical mirror, transmitted through a fly-eye lens, and the exposure amount is adjusted by a shutter. A projection exposure apparatus that adjusts, converges with a condenser lens, reduces the light beam transmitted through the reticle with a reduction projection lens, and irradiates the object mounted on an XY stage with an image corresponding to the image forming position of the light beam. , The shutter can be adjusted stepwise or continuously.

[2] The projection exposure apparatus according to claim 1, wherein the exposure amount is reduced when the distance between the imaging position and the resist layer is short, and the exposure amount is reduced when the distance between the imaging position and the resist layer is long. Is configured to be increased.

[Industrial applications]

The present invention relates to a projection exposure apparatus for forming a pattern of a semiconductor device and an exposure method therefor.

In order to cope with miniaturization accompanying the recent high integration of semiconductor substrates, the numerical aperture of the projection optical system has been increased, and the depth of focus has been reduced accordingly.

Therefore, it is necessary to secure an effective depth of focus in the manufacturing process of the semiconductor device.

Under the circumstances described above, there is a demand for a projection exposure apparatus and an exposure method capable of securing an effective depth of focus in an exposure step using the projection exposure apparatus.

[Conventional technology]

A conventional projection exposure apparatus and its projection exposure method will be described in detail with reference to FIG.

FIG. 4 is a view showing a schematic structure of a conventional projection exposure apparatus. As shown in the figure, the light emitted from the mercury lamp 11 is reflected by the elliptical mirror 12, transmitted through the fly-eye lens 13, adjusted in the exposure amount by the shutter 14, and converged by the condenser lens 15, and the pattern 6a is formed. The light beam transmitted through the reticle 6 is reduced by a reduction projection lens 17 and irradiated on a wafer 8 on a XY stage 19 on which a resist film 8a is formed.

In the case of using such a projection exposure apparatus, exposure is performed by fixing the image forming position of the light beam to a fixed position in the optical axis direction on the surface of the wafer 8 and fixing the exposure amount to a fixed value by the shutter 14. ing.

[Problems to be solved by the invention]

In the conventional projection exposure apparatus and the exposure method described above, the image forming position of the light beam is fixed at a fixed position in the optical axis direction on the surface of the object to be exposed, and the exposure amount is fixed at a fixed value by a shutter. Since the exposure is performed, when the numerical aperture of the optical system is high and the step on the surface of the object to be exposed is large, the effective depth of focus becomes asymmetric, so when projecting and exposing a pattern with finer dimensions. Makes it difficult to secure an effective depth of focus, and on a flat substrate as shown in FIG. 5, the surface of the resist film becomes thinner as shown by the defocus (+ δ ₁ ) in the figure. Or a bottom edge of the resist film as shown by a defocus (−δ ₁ ) in the drawing, and on a substrate having a large step as shown in FIG. −
As shown in δ ₁ ), there is a problem that the pattern is formed continuously and it becomes difficult to control the line width.

In view of the circumstances described above, the present invention provides a projection exposure apparatus and an exposure method that can secure an effective depth of focus when projecting and exposing a fine pattern on an object having a large surface step. It is intended to be provided.

[Means for Solving the Invention]

According to the projection exposure apparatus of the present invention, light emitted from a mercury lamp is reflected by an elliptical mirror, transmitted through a fly-eye lens, the exposure is adjusted by a shutter, converged by a condenser lens, and the light transmitted through the reticle is reduced and projected. A projection exposure apparatus that is reduced by a lens and irradiates an object to be exposed mounted on an XY stage.
The shutter is configured to be adjustable stepwise or continuously, and the exposure method of the projection exposure apparatus of the present invention uses the projection exposure apparatus, and when the distance between the image forming position and the resist layer is short, The exposure amount is reduced, and the exposure amount is increased when the distance between the image forming position and the resist layer is increased.

[Action]

That is, in the present invention, the shutter is moved in accordance with the movement of the XY stage in the optical axis direction so that the image forming position of the light beam to be imaged on the surface of the object placed on the XY stage of the projection exposure apparatus is moved. Adjusts the amount of exposure, thereby making it possible to secure an effective depth of focus, and to prevent film slippage on the surface of the resist film or skirting of the bottom surface of the resist film, and the bottom surface of the resist film can be prevented. It is possible to control the line width in the section satisfactorily.

〔Example〕

Hereinafter, a schematic structure of a projection exposure apparatus according to an embodiment of the present invention will be described in detail with reference to FIG. 1, and the shape characteristics of a pattern formed by an exposure method according to an embodiment of the present invention will be described in detail with reference to FIG.

FIG. 1 is a view showing a schematic structure of a projection exposure apparatus according to one embodiment of the present invention. As shown in the figure, the light emitted from the mercury lamp 1 is reflected by the elliptical mirror 2, transmitted through the fly-eye lens 3, the exposure is adjusted by the shutter 4, and converged by the condenser lens 5 to form the pattern 6a. The light beam transmitted through the reticle 6 is reduced by a reduction projection lens 7 and irradiated on a wafer 8 on a XY stage 9 on which a resist film 8a is formed.

In the projection exposure apparatus according to an embodiment of the present invention, the XY stage 9 can be moved in the optical axis direction so as to move the image forming position of the light beam on the surface of the wafer 8, and the shutter 4 is moved in accordance with the amount of movement. It is possible to control and adjust the exposure amount.

When the exposure amount is adjusted by controlling the shutter 4 in accordance with the movement of the image forming position of the light beam on the surface of the wafer 8 in this manner, on a flat substrate as shown in FIG.
If the defocus is + δ ₂ , the exposure amount is reduced, or if the defocus is −δ ₂ , the exposure amount is increased.
It is possible to form a resist pattern that is almost the same as in the case of the best focus, to prevent film slippage at the surface portion of the resist film or skirting at the bottom portion, and to control the line width satisfactorily. Becomes possible.

Also, on a substrate having a large step as shown in FIG. 3, if the exposure amount is adjusted in the same manner as in the case of FIG. 2, the same effect as in the case of FIG. 2 can be obtained as shown. .

In the case of continuously changing the imaging position in the present embodiment, it is necessary to perform high-speed exposure control,
Design transmittance in advance in addition to the normal shutter function
Use ND filter together.

As a result of applying the present invention to a projection exposure apparatus having an exposure wavelength of i-line (365 nm) and a numerical aperture of 0.35, the pattern of 0.5 μm line width or gap width has a practical depth of focus of 0.5 μm in the conventional method. In this case, the thickness was 1.5 μm.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, when the numerical aperture of the optical system is high, the XY stage is moved in the direction of the optical axis to change the structure of the projection exposure apparatus. Since the exposure is adjusted by the shutter in accordance with the movement of the image forming position of the light beam on the surface, it is possible to secure an effective depth of focus. A projection exposure apparatus and a method of exposing the same, which are advantageous in that it is possible to control the line width at the bottom portion of the resist film, etc. Can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a schematic structure of a projection exposure apparatus according to one embodiment of the present invention, and FIG. 2 is formed on a flat substrate by an exposure method according to one embodiment of the present invention. FIG. 3 is a view showing the shape of a pattern, FIG. 3 is a view showing the shape of a pattern formed on a substrate having a large step by an exposure method according to an embodiment of the present invention, and FIG. 4 is a schematic structure of a conventional projection exposure apparatus. FIG. 5 is a diagram showing the shape of a pattern formed on a flat substrate by a conventional exposure method. FIG. 6 is a diagram showing the shape of a pattern formed on a substrate having a large step by a conventional exposure method. Fig. In the figure, 1 is a mercury lamp, 2 is an elliptical mirror, 3 is a fly-eye lens, 4 is a shutter, 5 is a condenser lens, 6 is a reticle, 6a is a pattern, 7 is a reduction projection lens, 8 is a wafer, and 8a is a resist film. Reference numeral 9 denotes an XY stage.

Claims (2)

(57) [Claims] 1. A condenser lens (5) which reflects a light beam emitted from a mercury lamp (1) by an elliptical mirror (2), transmits the light beam through a fly-eye lens (3), adjusts an exposure amount by a shutter (4), and adjusts an exposure amount. A projection exposure apparatus for reducing the light beam transmitted through the reticle (6) with a reduction projection lens (7) and irradiating the object (8) mounted on an XY stage (9) A projection exposure apparatus wherein the shutter (4) can be adjusted stepwise or continuously in accordance with an image forming position. 2. A projection exposure apparatus according to claim 1, wherein the exposure amount is reduced when the distance between the image forming position and the resist layer is short, and is reduced when the distance between the image forming position and the resist layer is long. An exposure method for a projection exposure apparatus, wherein the exposure amount is increased.