JPH0529193A - Projection type exposure method using ultraviolet pulsed laser - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] A high-power, short-wavelength ultraviolet pulsed laser beam is used to generate a speckle pattern and generate a fine circuit pattern at a desired position on a substrate using a reduction projection lens Provided is a projection type exposure method using an ultraviolet pulse laser capable of transferring with high resolution. [Structure] An ultraviolet pulsed laser light emitted from an ultraviolet pulsed laser light source 17 is diffused, and the diffused ultraviolet pulsed laser light is condensed by a condenser lens 23 to be directed to a reticle on which a desired fine circuit pattern is formed. Likewise, the substrate is moved to a desired position, and by this uniform illumination, a desired fine circuit pattern on the reticle is imaged at a desired position on the substrate by a reduction projection lens to form the desired fine circuit pattern on the substrate. Projection exposure to the desired position above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure method using an ultraviolet pulse laser for photorepeating a fine circuit pattern on a wafer substrate for producing ICs and LSIs and printing it by reduction projection printing.

[0002]

2. Description of the Related Art FIG. 1 is a block diagram of a photo repeater conventionally used. Below the light source part 1 is a reticle holding part 2 for fixing a reticle plate on which an image of, for example, 10 times the usage pattern is recorded. Below this is the camera body 3, and at the bottom of it is the exposure lens (reduction projection lens) 4
Is installed. At the time of reduction exposure, the reticle plate is illuminated by the light coming from the light source portion, and its image is exposed plate 5 fixed to plate holder 6 by exposure lens 4.
An image is formed on the surface of, and reduction exposure is performed. When one reduction exposure is completed, the XY stage 7 automatically moves the plate to be exposed to the next exposure portion and stops, and the next reduction exposure is performed. In this way, reduction exposure is automatically performed one after another on necessary portions, and the exposure on one exposed plate (substrate) is completed.

The details of the light source portion 1 are shown in FIG. Focused light 10 emitted from a light source lamp 9 attached to the upper part of the reflection concentrator 8 passes through a shutter 11 and a light integrator 12 that makes the light intensity distribution uniform, and becomes a diffused light with a uniform distribution. Enters the collimator lens 14 and collimates 1
5 and enters the reticle holding portion 2 of FIG.

Further, Japanese Patent Laid-Open No. 48-30875 discloses that pulse laser light is used as a light source for exposure.

[0005]

However, when the latter prior art pulsed laser light source is used as the light source of the former prior art reduction projection exposure apparatus, the laser light source generally has a narrow spectral bandwidth. Therefore, there is a problem that so-called speckle noise is generated and a fine circuit pattern cannot be transferred with high resolution.

An object of the present invention is to solve the above problems.
A high-power, short-wavelength ultraviolet pulsed laser beam is used to transfer a fine circuit pattern to a desired position on a substrate with high resolution using a reduction projection lens without generating a speckle pattern. A projection exposure method using a pulse laser is provided.

[0007]

In order to achieve the above object, the present invention diffuses the ultraviolet pulsed laser light emitted from the ultraviolet pulsed laser light source, and collects the diffused ultraviolet pulsed laser light with a condenser lens. The reticle on which the desired fine circuit pattern is formed is illuminated and uniformly illuminated, and the substrate is moved to a desired position. This uniform illumination causes the reduction projection lens to project the desired fine circuit pattern on the reticle onto the substrate. Is a projection type exposure method using an ultraviolet pulse laser, wherein the desired fine circuit pattern is projected and exposed at a desired position on the substrate by forming an image at the desired position.

[0008]

With the above structure, a speckle pattern is not generated by using an ultraviolet pulsed laser beam having a high output and a short wavelength, and a fine circuit pattern is successively reduced and exposed to a desired position on a substrate by a reduction projection lens. Can be transferred with high resolution.

[0009]

EXAMPLES The present invention will be described in detail below with reference to the examples shown in the drawings. 3 is a diagram showing a schematic configuration of an embodiment of a photo repeater which is an exposure apparatus of the present invention, and FIG.
It is a block diagram which showed in detail the light source part 16 shown in FIG.

Reference numeral 16 is a light source portion for outputting a high-power parallel laser beam. That is, the laser light 18 for exposure emitted from the laser oscillator 17 which emits pulsed light having a sufficiently short pulse width is
The light is bent downward by the mirror 19, enters the optical integrator 21 through the shutter 20, becomes diffused light 22 having a uniform light distribution, enters the collimator lens 23, and becomes a parallel light beam 24, and becomes the reticle holding unit 2. Proceed to. Then, by continuously moving the XY stage 7 and outputting a pulse laser at a predetermined position, the reticle image is transferred to the plate to be exposed (substrate) 5 by the exposure lens (reduction projection lens) 4.

The photorepeater is normally fed at the earliest 10 times.
Although it is up to 0 mm / s, in order to perform the exposure while feeding, the exposure must be performed for a short time as long as the displacement of the image does not affect the pattern. For example,
In the case of a 1 μm pattern, it is necessary to use a laser having a short pulse width of 1 μs or less in order to suppress an image shift of 0.1 μm or less. Further, at an exposure wavelength of 3000 to 4000 Å, an energy density of 10 mJ / cm ³ or more is usually required for exposing a photoresist. Assuming that the transmittance of the optical system on the way is 1/3, the laser output required for a chip of maximum 10 mm square is 30 mJ.

As described above, the exposure wavelength is 3000 to 40.
Using a laser with a pulse width of 1 μs or less and a laser output of 30 mJ or more at 00Å, the photo repeater moves the reticle holding part (master reticle) 2 and the exposed plate 5 at a predetermined position while moving them at a speed of 100 mm / s or less. It is possible to continuously perform exposure with a trigger signal indicating that the exposure time has come, and the exposure time can be greatly shortened.

As described in the prior art, XY
It is obvious that the reticle image can be transferred onto the plate (substrate) 5 to be exposed by moving the stage 7 intermittently and outputting a pulse laser at a desired position.

FIG. 4 shows the construction of another embodiment of the light source section 16. A laser beam 18 emitted from a laser oscillator 17 which emits a pulsed light having a sufficiently short pulse width is bent downward by a mirror 19, passes through a shutter 20 and enters an optical integrator 21, and is a diffused light with a uniform intensity distribution. 22 enters the collimator lens (condensing lens) 23,
The diffused light image at the exit end of the collimator lens 23 is sent to the reticle holding unit 2 as a parallel light beam 24 so as to form an image on the entrance pupil of the exposure lens 4. The image of the reticle illuminated with this light is transferred to the plate 5 to be exposed while moving by the exposure lens 4.

A feature of this embodiment is that the illumination optical system of the projection type exposure apparatus shown in FIG. 4 is provided with a speckle suppressing optical system 25 for suppressing generation of speckle. When a laser is used as the exposure light source, the coherence of the laser light is strong, so that a speckle pattern is generated in the transfer pattern. The optical integrator 21 shown in FIGS. 4 and 5 has a considerable speckle suppression effect, but in the case of a fine pattern, high resolution is required, and thus it is difficult to perform highly accurate transfer by itself. .. Therefore, as shown in FIG. 5, it is possible to transfer a fine pattern accurately and at high speed only by using the speckle suppression optical system 25.

FIG. 6 shows an example of the speckle suppressing optical system used in the present invention. Laser light with high coherence 1
When 8 enters the cell 26 and passes through the liquid 27 therein, the band width of the light is widened and emerges as a low-coherence laser light 28 with reduced coherence. As the liquid 27, various liquids such as a liquid obtained by diluting milk with water and carbon disulfide can be used.

FIG. 7 shows another example of the speckle suppressing optical system used in the present invention. The laser light 18 having a high coherence enters the optical fiber bundle 29 having a length nonuniformity exceeding the coherence length, and the wavefronts are made different in the space to emerge as the light 30 having a low coherence. The generation of speckles can be suppressed.

FIG. 8 shows another example of the speckle suppressing optical system 25 used in the present invention. The laser light 18 having a high coherence enters the cell 26 and passes through the liquid 28 in the cell 26, so that the bandwidth of the light is widened, the coherence is reduced, and the laser light 28 is emitted as a low coherence. Next, this light enters the optical fiber bundle 29 having a nonuniform length, which is longer than the coherence length of the light, and further emerges as a laser light 30 with low coherence. By performing the exposure with this light, it is possible to suppress the generation of speckles even when the laser light with a short pulse is sufficiently exposed.

FIG. 9 shows another example of the speckle suppressing optical system 25 used in the present invention. The laser light 18 with high coherence hits the ground glass 32 rotated by the motor 31 and undergoes random light modulation,
The diffused light 33 with the coherence reduced by making the wavefronts different in the space is then incident on the stationary ground glass 34 and the direction of the light is randomly changed again, and the diffused light 35 with the reduced coherence is generated. Comes out. Therefore, speckle can be suppressed by using this light.

If two or more of the rotary ground glass are allowed to pass, the effect of suppressing speckles will be correspondingly higher. But,
Since the transmittance of laser light is lowered, there is a certain limit.
Further, the ground glass is not necessarily required to be rotated, and may be any movement such as vibration or movement in one direction. The static ground glass alone has some effect, but by adding the motion ground glass, the effect is dramatically increased.

By providing each of the various speckle suppressing optical systems as described above or in the optical path of the light source part, a fine pattern can be transferred with high resolution.

[0022]

As described above, according to the present invention, in the reduction projection type exposure method, a high-output, short-wavelength ultraviolet pulse laser beam is used to generate a fine circuit pattern without generating a speckle pattern. With the reduction projection lens, it is possible to perform reduction projection exposure to desired positions on the substrate sequentially with high resolution.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a photo repeater.

FIG. 2 is a configuration diagram showing a light source portion 1 in detail.

FIG. 3 is a schematic configuration diagram of an embodiment of a photo repeater.

FIG. 4 is a configuration diagram showing a light source portion 16 in detail.

FIG. 5 is a configuration diagram showing another example of a light source portion.

FIG. 6 is an example of a speckle suppression optical system.

FIG. 7 shows another example of the speckle suppression optical system.

FIG. 8 shows another example of the speckle suppression optical system 25.

FIG. 9 shows another example of the speckle suppression optical system 25.

[Explanation of symbols]

 2 ... Reticle holding part, 3 ... Camera body part, 4 ... Exposure lens (reduction projection lens), 5 ... Exposed plate (substrate), 6 ... Plate holder, 7 ... XY stage, 16 ... Light source part, 17 ... Laser oscillator , 20 ... Shutter, 21 ... Optical integrator, 23 ... Collimating lens, 25 ... Speckle suppression optical system

Claims (1)

Claim: What is claimed is: 1. An ultraviolet pulsed laser beam emitted from an ultraviolet pulsed laser light source is diffused, and the diffused ultraviolet pulsed laser beam is condensed by a condenser lens to form a desired fine circuit pattern. Point it at the reticle and illuminate it uniformly,
The substrate is moved to a desired position, and the uniform illumination causes the desired fine circuit pattern on the reticle to be imaged at a desired position on the substrate by a reduction projection lens, so that the desired fine circuit pattern is formed on the substrate. A projection type exposure method using an ultraviolet pulse laser, which comprises projecting and exposing the position.