JPH01114035A - Aligner - Google Patents

Abstract

PURPOSE:To obtain an aligner having no irregular illumination with a simple configuration by inserting a phase plate to the optical path of a luminous flux irradiated from a coherence light source, and converting the phase of the flux at random to form an incoherent flux. CONSTITUTION:A luminous flux irradiated from a coherence light source 1 is extended by an expander 2, reflected on a reflecting mirror 10, and distinguished at random to a fine regions converted by from the phase of the region not converted in its phase through a phase plate 3. Thus, the incoherent flux is incident to a flies array lens 4. A secondary light source corresponding to the number of rod lenses is formed at the output side of the lens 4. This is focused on the pupil 9 of a projection lens 7 by a condenser lens 5 to be uniformly irradiated on a reticle 6, thereby eliminating interference fringes. Accordingly, a system having no illumination irregularity is obtained with a simple configuration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exposure apparatus for exposing and transferring semiconductor circuit elements onto a wafer, and particularly to an exposure apparatus suitable for using a coherent light source as an illumination system.

[Conventional technology]

Conventional equipment! used an excimer laser as a coherent light source, and used a deflector to make the laser beam incoherent so as to scan the laser beam two-dimensionally on the pupil plane of the projection lens. Related devices of this type include, for example, Japanese Patent Publication No. 61-502507.

[Problem that the invention seeks to solve]

2. Description of the Related Art In the manufacture of semiconductor integrated circuit devices and the like, photolithography technology, which optically exposes and transfers circuit patterns, is mainly used. Exposure apparatuses include a proximity method, a projection exposure method, and a reduction projection exposure method. Conventionally, these exposure apparatuses have used light from a mercury lamp as illumination. In contrast, it has been proposed to use laser light to obtain higher brightness. Furthermore, the resolving power of a photolithography apparatus depends on the wavelength of the light used, and the shorter the wavelength, the higher the resolution and power can be achieved. For this purpose, it has been proposed to use an excimer laser with a wavelength in the deep ultraviolet region as an illumination light source. However, although lasers have high brightness, they are coherent lights, so they have a drawback of strong interference and the generation of random interference fringes such as speckle patterns.

On the other hand, in the above-mentioned conventional technology, the laser beam is scanned two-dimensionally on the pupil plane of the projection optical system, and the laser beam is exposed with light whose phase is shifted approximately in time to achieve incoherence. However, in this conventional method, when scanning the laser beam two-dimensionally on the pupil plane, it cannot be made incoherent unless the entire area of the pupil is scanned.For this reason, with a pulsed laser such as an excimer laser, the number of pulses is limited. must be increased. Furthermore, there is a drawback that unevenness in the intensity distribution of the laser beam directly causes unevenness in illuminance on the wafer. Furthermore, since the optical deflector is included in the illumination optical system, there is a problem that the apparatus becomes large and expensive.

SUMMARY OF THE INVENTION An object of the present invention is to provide an illumination optical device that has a simple configuration and is free from uneven illumination in order to convert coherent light such as a laser beam into incoherent light.

[Means for solving problems]

In order to achieve the above object, the present invention, as shown in FIG. A phase plate 3 is provided in which the phase shifter is randomly converted.

[Effect]

As shown in FIG. 2, the phase plate includes a plurality of micro regions 3-1.
It is divided into 3-2..., and each works to convert the phase of light at an arbitrary location.

As a result, the light flux incident on the integrator is made incoherent because its phase is random. Furthermore, since the light passes through the integrator, no interference occurs on the object surface or the substrate surface 8, and uniform illumination light can be obtained.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the present invention applied to a reduction projection exposure apparatus. A light beam emitted from a coherent light source 1 is expanded by an expander 2 and reflected by a reflecting mirror 10, and then passes through a phase plate 3 and is made incoherent. As shown in FIG. 2, the phase plate 3 is divided into minute regions of 5 to 50 .mu.m, to form a region 3-1 in which the phase of light is not changed and a region 3-2 in which the phase is changed by π. These regions are randomly arranged, and in order to transform the 6 phases by π, the third
As shown in the figure, a thin film having a refractive index n and a thickness t is formed in the region 3-2. The thickness t is t, = o, 5λ/ (n -1), where λ is the wavelength of the light used and n is the refractive index of the film.
In this example, a K r F laser (wavelength λ = 248.4 nm) among excimer lasers is used as a coherent light source, and as a thin film, 5
iOz (refractive index n=1.46) was used. As is clear from the above equation, the thickness t of the 5iOz film is required to be 0.27 μm.

The S i O,2 film can be easily formed on a glass substrate by using a sputtering method or the like.

The phase conversion film divided into minute regions is placed on a quartz glass substrate 3.
After a 5ift film is formed on the top of the film, a 5ift film is formed using lithography technology. That is, a resist is applied on the 5-ins film, and exposed parts and non-exposed parts of the minute area are selected and exposed. After that, develop the resist and 5i02
By performing this etching, a phase plate as shown in FIG. 3 can be produced. Although 5iOz was used as the phase conversion film in this embodiment, various other thin films may be used. Moreover, even if a thin film is not used, a step may be provided on the surface of the glass substrate as shown in FIG.

The light beam that has passed through the phase plate 3 and has been rendered incoherent enters a fly's eye lens 4 that is composed of a plurality of rod lenses. On the exit side of the fly's eye lens,
Secondary light sources whose number corresponds to the number of rod lenses are formed from the incident light flux. By focusing the secondary light source on the pupil plane 9 of the projection lens 7 using the condenser lens 5, uniform illumination can be achieved on the reticle 6. Furthermore, the illumination distribution in the exposure area on the wafer 8 is uniform, and furthermore, random interference fringes such as speckles do not occur due to the incoherence created by the phase plate. As a result, it became possible to image a pattern on the wafer in a very good condition.

〔Effect of the invention〕

According to the present invention, coherent light can be made incoherent with a simple configuration, and illumination can also be easily made uniform. Therefore, the lighting device can be made smaller and cheaper. As a result, it is now possible to use coherent and high-luminance laser light as illumination light in photolithography equipment used in the manufacture of semiconductor integrated circuit devices, and it is also possible to shorten the exposure wavelength by using excimer lasers, etc. Therefore, it is effective in making patterns finer and increasing throughput.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the present invention, FIG. 2 is a plan view of a phase plate, which is one of the components of the present invention, and FIGS. 3 and 4 are longitudinal sectional views of the phase plate. . 1... Coherent light source, 3... Phase plate, 3-2.
...Phase converter, 4...Integrator, 5...Condenser lens, 6...Reticle, 7...Projection lens, 8...Figure l

Claims (1)

[Claims] 1. In an exposure apparatus that uses a coherent light source, an illumination device is provided with a member that converts the phase of the light passing through a plurality of predetermined minute regions in the light beam emitted from the coherent light source, in the optical path of the light beam emitted from the coherent light source. An exposure apparatus comprising: