JPH104059A - Exposure apparatus and exposure method - Google Patents

Abstract

(57) Abstract: An exposure apparatus capable of realizing a predetermined light intensity in nonlinear multiple exposure using, for example, a two-photon absorption resist and shortening each exposure time. SOLUTION: An illumination optical system IL for converging a laser beam from a pulse oscillation type laser light source 1 to illuminate a mask 3 on which a predetermined pattern is formed, and a photosensitive substrate for converting a pattern image of the mask 3 to a photosensitive substrate. And a projection optical system 4 to be formed on the projection optical system 5. Then, a resist having a photosensitive characteristic in which exposure proceeds nonlinearly with respect to the intensity of incident light is applied onto the substrate 5, and the light intensity distribution on the substrate 5 is changed to perform nonlinear multiple exposure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus and an exposure method, and more particularly to a projection exposure apparatus used for manufacturing a semiconductor device, a liquid crystal display device, and the like.

[0002]

2. Description of the Related Art For example, Japanese Unexamined Patent Publication No. 6-29109 and the letter 177 of the 33rd volume (1994) of "Japanese Journal of Applied Physics" disclose a technique relating to nonlinear multiple exposure by the inventors of the present application. ing. In the nonlinear multiple exposure, multiple exposure is performed on a resist having a photosensitive characteristic in which exposure proceeds nonlinearly with respect to the intensity of incident light while changing the light intensity distribution on a wafer coated with the resist.

At the time of exposure, a latent image reaction density ξ represented by the following equation (1) is generated in the resist. ξ = exp (−C · I ^m · T) (1) where, I: intensity of incident light T: exposure time C: constant

Here, m is an index indicating the linearity of the resist. It is said that, in a resist having a photosensitive characteristic of m = 1, such as a positive resist generally used at present, the photosensitive proceeds linearly with the intensity of incident light. On the other hand, m
It is said that in a resist having the photosensitive characteristic of # 1, the photosensitive proceeds nonlinearly with the intensity of the incident light. In the non-linear multiple exposure, for example, the exposure is repeated while changing the light intensity distribution on the wafer by changing the position of the mask pattern with respect to the projection optical system or changing the mask pattern itself. With this nonlinear multiple exposure technique, a high-resolution fine pattern exceeding the diffraction limit can be formed on a wafer.

[0005]

In general, the non-linear multiple exposure technique requires a higher light intensity and a longer exposure time than ordinary exposure. Hereinafter, a two-photon absorption resist having a photosensitive characteristic of m = 2, for example, will be considered as a resist having a photosensitive characteristic in which light sensitivity progresses nonlinearly with respect to light intensity. E, published in Proceedings of SPIE, Vol. 1674 (1992), pp. 776-778.
According to the paper by n. S. Wu et al., the two-photon absorption efficiency W (unit: photon / sec) is given by W = δI ² .

[0006] The two-photon absorption amount V is given by: V = WT = δI
Given by ² T. Here, the constant δ is approximately 10 ⁻⁵⁸
It is on the order of m ⁴ sec / photon. Assuming the value of this constant δ, it is difficult to achieve exposure using a two-photon absorption resist unless I ² T is extremely large. That is, for example, in a nonlinear multiple exposure technique using a two-photon absorption resist, much larger light intensity and exposure time are required than in normal exposure.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. For example, in non-linear multiple exposure using a two-photon absorption resist, it is possible to realize a predetermined light intensity and to reduce an exposure time for each exposure. It is an object to provide an apparatus and an exposure method.

[0008]

In order to solve the above problems, the present invention provides a method for illuminating a mask on which a predetermined pattern is formed by condensing a laser beam from a pulse oscillation type laser light source. An illumination optical system, and a projection optical system for forming a pattern image of the mask on a photosensitive substrate, the photosensitive substrate having a photosensitive characteristic in which photosensitive progresses nonlinearly with respect to the intensity of incident light on the substrate. An exposure apparatus is provided in which a resist is applied and nonlinear multiple exposure is performed by changing a light intensity distribution on the substrate. According to a preferred aspect of the exposure apparatus of the present invention, the latent image reaction density of the resist is formed corresponding to the m-th power (m> 1) of the intensity of incident light.

In the present invention, a laser beam from a pulse oscillation type laser light source is condensed to illuminate a mask on which a predetermined pattern is formed, and a pattern image of the mask is exposed through a projection optical system. Formed on a transparent substrate,
A resist having a photosensitive characteristic in which photosensitivity advances nonlinearly with respect to the intensity of incident light is applied on the substrate, and a non-linear multiple exposure is performed by changing a light intensity distribution on the substrate. Provide a way. According to a preferred aspect of the exposure method of the present invention, the latent image reaction density of the resist is formed corresponding to the m-th power of the intensity of the incident light (m> 1).

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, it will be explained that a pulse oscillation laser having a large peak power is more advantageous than a continuous oscillation laser in exposure when a two-photon absorption resist is used, if the average power is the same. . As described above, the two-photon absorption amount V is proportional to I ² T. In the case of a continuous wave laser, the two-photon absorption amount V is proportional to Iav ² T, where the average power is Iav. On the other hand, in the case of pulsed lasers, and the peak power and Ipe, when the ratio of oscillation time and oscillation interval and R (R <1), 2-photon absorption quantity V is ^{Ipe 2 RT = IpeIavT = Iav 2} T / It is proportional to R.

As described above, in the pulse oscillation laser, the two-photon absorption V becomes 1 / R for the same exposure time as compared with the continuous oscillation laser having the same average power. In other words, the exposure time of the pulse oscillation laser is R times that of the continuous oscillation laser having the same average power. Here, since R <1, it can be seen that the exposure time can be reduced by using a pulsed laser. That is, if the exposure time is the same, a pulsed laser with lower power can be used. This is equivalent to the fact that the exposure time has been increased by R times due to the uneven distribution of the light in the R times portion. That is, it is possible to increase the light intensity by temporally distributing the laser light.

As described above, in the exposure using the two-photon absorption resist, the exposure time can be drastically shortened by temporally distributing the illumination light.
Alternatively, by illuminating the illumination light temporally, the laser power can be drastically reduced. This is generally true for resists having nonlinear photosensitive characteristics where m> 1 in equation (1) above. In other words, it can be easily inferred that the temporal uneven distribution is advantageous even in the case of other resists whose photosensitivity proceeds in accordance with I ^m T (m> 1). In general, it is clear that there is a case where temporal uneven distribution is advantageous even for a resist having a non-linear photosensitive characteristic which cannot be expressed by a power of light intensity.

An embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a view schematically showing a configuration of an exposure apparatus according to an embodiment of the present invention. The exposure apparatus of FIG. 1 includes a pulse oscillation type laser light source 1. Note that the peak power Ipe of the laser light source 1 is equal to the average power Iav of 100.
Shall be doubled. The light emitted from the laser light source 1 is converted into a substantially parallel light beam by a collimating lens 2, and then illuminates a mask 3 which is a projection original. As described above, the laser light source 1 and the collimating lens 2 constitute an illumination optical system IL for illuminating the mask 3.

The light diffracted by the pattern of the mask 3 forms a mask pattern image on the surface of a wafer 5 serving as a photosensitive substrate via a projection optical system 4. The image plane size (viewing area) of the projection optical system 4 covers the entire pattern of the mask 26. The surface of the wafer 5 is coated with a two-photon absorption type resist. The wafer 5 is fixed on a wafer stage 6, and the wafer stage 6 is configured to be two-dimensionally driven by a suitable drive system 7 in a plane perpendicular to the optical axis of the projection optical system 4.

In this manner, an entire image of the mask pattern is formed on the wafer 5 by one exposure. In the non-linear multiple exposure, when the first exposure is completed, the relative position of the mask 3 with respect to the projection optical system 4 is changed, the mask pattern is changed by exchanging the mask 3, or the wafer 5 with respect to the projection optical system 4 is moved. Change the relative position. As described above, the non-linear multiple exposure is completed by repeating the exposure while changing the light intensity distribution on the wafer 4. As a result, a high-resolution fine pattern exceeding the diffraction limit can be formed on the wafer 5 by nonlinear multiple exposure.

In the above embodiment, the peak power of the pulse oscillation type laser light source 1 is 100 times the average power. Therefore, as described above, the exposure time can be reduced to 1/100 as compared with a continuous wave laser having the same average power. In each of the above embodiments, 2
The invention has been described using a photon absorbing resist as an example.
However, as described above, in general, I ^m T (m>
The present invention can be applied to the case of other resists in which exposure proceeds nonlinearly in correspondence with 1). Needless to say, the present invention can be applied to a resist having a non-linear photosensitive characteristic that cannot be expressed by a power of light intensity.

[0017]

As described above, according to the exposure apparatus and the exposure method of the present invention, for example, in a non-linear multiple exposure using a two-photon absorption resist, a predetermined light intensity is realized and the exposure time for each exposure is greatly reduced. can do.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a configuration of an exposure apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pulse oscillation type laser light source 2 Collimating lens 3 Mask 4 Projection optical system 5 Wafer 6 Wafer stage 7 Drive system IL Illumination optical system

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Soichi Yamato 3-2-2 Marunouchi, Chiyoda-ku, Tokyo Nikon Corporation

Claims (4)

[Claims] An illumination optical system for converging a laser beam from a pulse oscillation type laser light source to illuminate a mask on which a predetermined pattern is formed, and a pattern image of the mask on a photosensitive substrate. A projection optical system for forming, a resist having a photosensitive characteristic in which photosensitivity proceeds nonlinearly with respect to the intensity of incident light is applied on the substrate, and the light intensity distribution on the substrate is changed. An exposure apparatus for performing non-linear multiple exposure. 2. The exposure apparatus according to claim 1, wherein the latent image reaction density of the resist is formed corresponding to the m-th power (m> 1) of the intensity of incident light. 3. A laser beam from a pulse oscillation type laser light source is condensed to illuminate a mask on which a predetermined pattern is formed, and a pattern image of the mask is formed on a photosensitive substrate via a projection optical system. A resist having a photosensitive characteristic in which photosensitivity progresses nonlinearly with respect to the intensity of incident light is applied on the substrate, and a non-linear multiple exposure is performed by changing a light intensity distribution on the substrate. Exposure method. 4. The exposure method according to claim 3, wherein the latent image reaction density of the resist is formed corresponding to the m-th power (m> 1) of the intensity of incident light.