JP2589060B2 - Reduction projection exposure method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reduced projection exposure method for transferring a desired transfer aperture pattern onto a wafer.

[0002]

2. Description of the Related Art FIG. 4 is a sectional view showing a part of a photomask used in a conventional reduction projection exposure method. As shown in the figure, a light-shielding film 3 made of Cr or the like is provided on a glass substrate 1, a transfer-opening pattern 4 is formed by partially removing the light-shielding film 3, and the transfer-opening pattern 4 is isolated. Its size is close to the resolution limit of a reduction projection exposure apparatus.

[0003]

When a pattern is transferred onto a wafer by a reduction projection exposure apparatus using such a photomask, the amplitude distribution on the photomask is as shown in FIG. Since the optical system cannot transmit a high-frequency spatial frequency component, the amplitude distribution on the wafer has a waveform that spreads too wide as shown in FIG. For this reason, the line width of the pattern formed on the wafer increases, and the dimensional accuracy deteriorates.

The present invention has been made in order to solve the above-mentioned problems, and has as its object to provide a reduced projection exposure method capable of transferring a transfer aperture pattern close to the resolution limit with high accuracy.

[0005]

According to the present invention, there is provided a reduced projection exposure method for transferring a desired transfer opening pattern to a wafer, the method comprising: a light transmitting through the transfer opening pattern; A phase which is provided adjacent to the transfer aperture pattern and which is transmitted through a plurality of fine aperture patterns which are not transferred to the wafer and has a resolution equal to or less than a resolution limit, and which is inverted with respect to the phase of the light which has passed through the transfer aperture pattern. Exposure is performed using light having the following formula:

[0006]

1A and 1B are cross-sectional views each showing a part of a photomask used in a reduction projection exposure method according to the present invention. As shown in FIG.
Fine opening patterns 5a to 5d are provided on both sides of
The widths of the fine aperture patterns 5a to 5d have such small values that they cannot be resolved by the reduction projection exposure apparatus alone.
Further, the phase shift layer 2 is provided on the fine opening patterns 5b and 5c, and the thickness of the phase shift layer 2 is set to the fine opening patterns 5b and 5c.
This is a value that rotates the phase of light transmitted through 5c by 180 °.

And a reduction projection exposure method according to the present invention,
That is, in the method of transferring a pattern onto a wafer using the photomask shown in FIGS. 1A and 1B, the light is transmitted adjacent to the transfer opening pattern 4 and is provided adjacent to the transfer opening pattern 4. Light transmitted through a plurality of fine aperture patterns 5b and 5c that are not transferred to a wafer and having a resolution equal to or less than the resolution limit, and having a phase inverted from the phase of light transmitted through the transfer aperture pattern 4, that is, light having a phase different by 180 °; With respect to the phase of light transmitted through a plurality of fine opening patterns 5a and 5d provided adjacent to the fine opening patterns 5b and 5c and having a resolution equal to or less than the resolution limit and not transferred to a wafer, and transmitted through the fine opening patterns 5a and 5d. Exposure is performed using light having an inverted phase.

In this reduced projection exposure method, the amplitude distribution on the photomask is as shown in FIG. That is,
The phase of the light passing through the transfer opening pattern 4 and the fine opening patterns 5a and 5d differs from the phase of the light passing through the fine opening patterns 5b and 5c by 180 °. Since the exposure optical system cannot transmit a high-frequency spatial frequency component, the amplitude distribution on the wafer is as shown in FIG. That is, only the light transmitted through the transfer opening pattern 4 is largely transmitted, and the light itself transmitted through the fine opening patterns 5b and 5c is not transmitted so much, but the light transmitted through the fine opening patterns 5b and 5c is transmitted through the transfer opening pattern 4. This prevents the amplitude distribution of the light from spreading laterally more than necessary. Therefore, it is possible to transfer the transfer aperture pattern 4 close to the resolution limit with high accuracy.

Next, a case where a 1/10 reduction projection exposure apparatus having an exposure wavelength λ = 365 nm and a numerical aperture NA of a reduction lens = 0.4 will be described. Conventionally, the minimum line width on a wafer of an isolated line that can be resolved by this apparatus has been about 0.5 μm. Thus, in the photomask shown in FIG. 1, the distance between the transfer opening pattern 4 and the fine opening pattern 5b, the distance between the transfer opening pattern 4 and the fine opening pattern 5c is 6 μm, the distance between the fine opening pattern 5a and the fine opening pattern 5b, The interval between the fine opening pattern 5c and the fine opening pattern 5d is 4.5 μm.
m, and the width of the fine opening patterns 5a to 5d was 1 μm. As a result, a pattern in which the width of the transfer opening pattern 4 was 3 μm, that is, 0.3 μm on the wafer, could be resolved.

In the above-described embodiment, the phase shift layer 2 is provided on the fine opening patterns 5b and 5c. However, a phase shift layer may be provided on the transfer opening pattern 4 and the fine opening patterns 5a and 5d.

[0011]

As described above, in the reduced projection exposure method according to the present invention, it is possible to transfer a transfer aperture pattern close to the resolution limit with high accuracy.

[Brief description of the drawings]

FIGS. 1A and 1B are cross-sectional views each showing a part of a photomask used in a reduction projection exposure method according to the present invention.

FIG. 2 is a graph showing an amplitude distribution on the photomask shown in FIG.

FIG. 3 is a graph showing an amplitude distribution on a wafer when the photomask shown in FIG. 1 is used.

FIG. 4 is a cross-sectional view showing a part of a photomask used in a conventional reduction projection exposure method.

FIG. 5 is a graph showing an amplitude distribution on the photomask shown in FIG. 4;

FIG. 6 is a graph showing an amplitude distribution on a wafer when the photomask shown in FIG. 4 is used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Glass substrate 2 ... Phase shift layer 3 ... Light shielding film 4 ... Transfer opening pattern 5b ... Fine opening pattern 5c ... Fine opening pattern

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Yoshio Kawamura 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Central Research Laboratory, Hitachi, Ltd. (56) References JP-B-62-50811 (JP, B2)

Claims (1)

(57) [Claims] 1. A reduced projection exposure method for transferring a desired transfer opening pattern to a wafer, the method comprising: transmitting light passing through the transfer opening pattern to the wafer provided adjacent to the transfer opening pattern; A reduced projection characterized in that light is transmitted using a plurality of fine aperture patterns below the resolution limit that are not transferred and light having a phase inverted from the phase of the light transmitted through the transfer aperture pattern. Exposure method.