JPH0497201A - Production of beam expander and diffraction grating - Google Patents

Abstract

PURPOSE:To obtain the compact beam expander at a low cost by providing two sheets of diffraction gratings intersecting with an excimer laser beam. CONSTITUTION:The 1st reflection type diffraction grating 1a and the 2nd reflection type diffraction grating 2a are so disposed as to intersect orthogonally with each other. The excimer laser beam 3 before being expanded by these diffraction gratings becomes a laser beam 4 expanded to a square shape. The laser light 3 emitted from an excimer laser beam source is uniformly expanded in the two directions within the plane perpendicular to the optical axis by the 1st diffraction grating 1a and the 2nd diffraction grating 2a orthogonal with the 1st diffraction grating 1a in such a manner, by which the square luminous flux having a uniform and wide area is obtd. The same function as the function of ordinary devices is obtd. in this way only by two sheets of the diffraction gratings in place of the costly optical lenses for which many pieces of optical parts constituting the device are used.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an excimer laser stepper, a beam expanding device used in an excimer laser processing machine, and a method for manufacturing a diffraction grating for an excimer laser.

2. Description of the Related Art In recent years, as semiconductor manufacturing technology has improved, technology for creating mask patterns using excimer laser light has become mainstream. Furthermore, processing machines using excimer lasers have appeared due to the demand for micro-processing. Both of the above two devices require large beam diameters. In the case of a stepper, the size of the exposure area must be 20 Ill or more due to the manufacturing process. In the case of a processing machine, it is necessary to shorten the wavelength of the laser beam or increase the diameter of the beam in order to narrow down the beam diameter, but if you use an excimer laser beam and further increase the diameter of the beam, The diameter can be reduced.

For the above reasons, a device for expanding excimer laser light is necessary. In recent years, beam expanding devices are generally composed of lens elements.

An example of the conventional beam expanding device mentioned above will be described below with reference to the drawings.

FIG. 7 shows the configuration of a conventional excimer stepper beam expanding device. As shown in FIG. 5, the conventional beam expanding device uses excimer laser light 3. Anamorphic zoom 6, zoom extract band 7, first integrator 9. Second integrator9. It is composed of a reticle blind projection lens 12° reticle 14, and the like.

The operation of the beam expanding device configured as described above will be explained below. First, excimer laser light 3
enters the device. The anamorphic zoom 6 turns a rectangular light beam into a circular light beam, and the zoom expansion band 7 turns a thin light beam into a thick light beam. Next, integrators 8 and 9 equalize the light intensity in the vertical and horizontal directions. The combination of the lens 10° 13 and the reticle blind projection lens 12 is configured to project light with uniform luminous intensity onto the reticle 14.

Problems to be Solved by the Invention In such a conventional configuration, a plurality of lenses are required for the anamorphic zoom 6 and the zoom beam expander 7 in order to reduce aberrations. Excimer laser (Kn-
In the case of F), a laser beam of 248 nm is oscillated, but the lens glass material used is quartz or fluorite as a material that transmits this far ultraviolet light, which has the problem that the lens manufacturing cost is high. Furthermore, since a large number of lenses are used, there is also the problem that the entire device becomes large.

The present invention solves these problems by providing a zoom extend band device in which the optical system that used many expensive lenses is replaced with a two-piece diffraction grating made of inexpensive materials, and a method for manufacturing the diffraction grating used therein. The purpose is to provide

Means for Solving the Problem In order to solve this problem, the present invention applies an excimer laser beam to a first diffraction grating in the front, expands the beam in the longitudinal direction, and then expands the beam by a second diffraction grating in the rear. It is equipped with two orthogonal diffraction gratings to expand the beam in the lateral direction.

Further, the diffraction grating used in the beam expanding device of the present invention is formed by processing a SiO2 plate using a hologram interference method and a wet etching or dry etching process.

Effect: With this configuration, the laser beam emitted from the excimer laser light source is uniformly expanded in two directions in a plane perpendicular to the optical axis by the first diffraction grating and the second diffraction grating perpendicular to the first diffraction grating. By doing so, it is possible to obtain a square luminous flux having a uniform and wide area. As a result, it is possible to realize a beam expanding device having the same functions as the conventional device by using only two diffraction gratings instead of a large number of expensive optical lenses.

Furthermore, in a diffraction grating created by the conventional method of forming a diffraction grating using photoresist, most of the excimer laser light is absorbed by the resist forming the diffraction grating, resulting in a decrease in laser light transmission efficiency. In order to prevent a decrease in the transmission efficiency of excimer light, a grating is created on the substrate by etching the optical plate. As a result, the diffraction grating is not a resist that absorbs excimer light (because the diffraction grating is formed on quartz or fluorite itself, the absorption of excimer light by the diffraction grating is eliminated, and the transmission efficiency of excimer light is improved ( Become.

EXAMPLE Hereinafter, a beam expanding device according to an example of the present invention will be explained with reference to the drawings. FIG. 1 shows the configuration of an expander according to a first embodiment of the present invention. As shown in FIG. 1, the first reflective diffraction grating 1a and the second reflective diffraction grating 2a are arranged to be perpendicular to each other, and the excimer laser beam 3 before being expanded is shaped into a square shape by the diffraction grating. The laser beam 4 is expanded to .

The operation of the beam expanding device configured as described above will be explained. Excimer laser light 3 (wavelength 2
48 nm), the beam is cut into a rectangle, and irradiated from the direction in which the shorter side of the rectangle is expanded by the first reflective diffraction grating. The irradiated light is diffracted by the first diffraction grating 1a, and the second reflective type is placed so as to be diffracted in a direction perpendicular to the diffraction direction of the first diffraction grating 1a and the direction of incidence of the excimer laser beam 3. It irradiates the diffraction grating 2a. The irradiated light is further diffracted and irradiates the reticle as laser light 4. FIG. 2 is a diagram showing the action of the first reflection type diffraction grating 1a in FIG.
The light is then diffracted and becomes a beam of light 5a. At this time, a part of the excimer laser light 3 becomes reflected light 5b. Specifically, the wavelength of the excimer laser beam 3 is λ (248 nm), and the incident angle is θ.
If the diffraction angle of τ, −th order is θdit, the diffraction grating pitch d is given by sinθr + sin e dit−λ/dθτ゛θd1t′″, and the magnification magnification m is m=tanθτ.

The second reflection type diffraction grating shown in FIG. 1 also expands the luminous flux by the same effect as described above. According to the embodiments described above, the excimer laser beam having a rectangular beam cross section can be diffracted twice to obtain a square beam.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 shows a beam expanding device according to a second embodiment of the present invention. FIG. 4 is a diagram showing the function of the first transmission type diffraction grating. The difference from the first embodiment is that two transmission diffraction gratings are used instead of two reflection diffraction gratings. Note that the same members as in FIGS. 1 and 2 are given the same numbers and their explanations will be omitted. The operation of the beam expanding device configured as described above will be explained.

The action of deflecting the laser beam by the diffraction grating is exactly the same as in the first embodiment. Since the diffraction grating is of a transmission type, the diffraction direction is mirror-symmetrical to that of the first embodiment, as shown in FIG.

Further, a third embodiment of the present invention will be described with reference to the drawings.

FIG. 5 and FIG. 6 are cross-sectional views of the diffraction grating in the manufacturing process of the diffraction grating of the present invention. As shown in Figure 5, SiO2
A mask is formed on the substrate 15 using a resist 16.

The manufacturing process up to FIG. 5 will be explained. A positive photoresist is spin-coated onto the SiO2 substrate 15 using a spinner.
Perform two-beam interference exposure using an r laser. Exposure is performed so that the pitch of the diffraction grating becomes the value d determined in the first embodiment. When the photoresist is developed, a grid of photoresist as shown in FIG. 5 is formed.

Next, FIG. 6 shows the relief grating of the SiO2 substrate 17 after etching. When the relief grating shown in FIG. 5 is subjected to wet etching or dry etching and the resist is removed, the relief shown in FIG. 6 is formed. Etching here uses HF and CF4. By performing such etching processing, a diffraction grating with good transmission efficiency for excimer laser light is formed, and an inexpensive beam expanding device can be realized.

Effects of the Invention As is clear from the description of the embodiments above, the present invention provides a low-cost, compact beam expanding device by providing two diffraction gratings that intersect with excimer laser light. be able to.

Furthermore, as a method for manufacturing the diffraction grating, by forming the grating on the surface of the SiO2 substrate by dry etching or wet etching, a diffraction grating that does not absorb excimer laser light and has good transmission efficiency can be realized.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the reflective beam expanding device of the present invention, FIG. 2 is a diagram showing the action of the reflective diffraction grating, FIG. 3 is a perspective view of the transmitting beam expanding device, and FIG. 4 is the same. 5 and 6 are cross-sectional views of the diffraction grating during the same manufacturing process, and FIG. 7 is a diagram showing the configuration of a conventional beam expanding device. la, 2a...Reflection type diffraction grating, Ib, 2b.
... Transmission type diffraction grating, 3 ... Excimer laser light, 4 ... Expanded laser light, 5a ...
・1st order diffracted light, 5b...Reflected light, 15...
...SiO2 substrate, 16...Photoresist, 1
7...SiO2 diffraction grating. Name of agent: Patent attorney Shigetaka Awano and one other person

Claims (3)

[Claims] (1) A beam expanding device consisting of an excimer laser, a diffraction grating that expands the laser beam, and a projection device, in which the two diffraction gratings that uniformly expand the laser beam are arranged so that the diffraction directions are orthogonal to each other. Expanding device. (2) The beam expanding device according to claim 1, wherein either a transmission type or reflection type diffraction grating is used for diffraction of the laser beam. (3) A method for manufacturing a diffraction grating in which a diffraction grating is formed by etching a fluorite plate or a SiO_2 plate that transmits or reflects excimer laser.