JPS61212816A - Lighting equipment - Google Patents

Abstract

PURPOSE:To obtain lighting equipment which prevent interference fringes from being formed on the irradiated surface of a wafer, etc., and is suitable to semiconductor manufacture by providing a waveguide means which makes luminous flux with good coherence incident on a fly-eye lens from a laser, etc., while its angle of incidence variously. CONSTITUTION:The luminous flux 2 from a light source such as a laser which emits luminous flux having good coherence is made incidence on the fly-eye lens 6 as parallel luminous flux from the afocal converter 45 consisting of convex lenses 4 and 5 at various angles of incidence by rotating a rotary mirror 3 as shown by an arrow, thus constituting the optical waveguide means. The luminous flux passed through plural fine lens elements constituting a lens 6 illuminates the irradiated surface of a wafer, etc., for semiconductor manufacture while the coherence is reduced by a lighting system lens 7 because respective pieces of luminous flux are variously out of phase to prevent interference fringes from being formed. Thus, the lighting equipment which realizes a high throughput while having high resolving power and high efficiency is obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an illumination device suitable for exposure equipment for semiconductor manufacturing, and uses a high-intensity light source such as an excimer laser with good coherence in %. Nine-time mask face or Ueno mask
The present invention relates to an illumination device that can completely reduce interference fringes that occur on a surface and uniformly illuminate an irradiated surface.

(Conventional technology) Recent semiconductor manufacturing technology includes high integration of electronic circuits.
There is a need for a lithographic technique that can form high-density circuit patterns.

Generally, when a circuit pattern on a mask or reticle surface is transferred onto a wafer surface, the resolution line width of the circuit pattern transferred onto the surface is proportional to the wavelength of the light source. For this reason, far ultraviolet (deep U) wavelengths of 200 to 300 nTIL are used.
For example, an ultra-high pressure mercury lamp, a xenon mercury lamp, etc. that oscillates a short wavelength in the V region) is used. However, these light sources have low brightness and lack directivity, and the photosensitivity of the photoresist coated on the wafer surface is also low, resulting in long exposure times and reduced υ throughput.

On the other hand, a light source with an oscillation wavelength in the deep UV region called excimer (@xcimar) laser has recently been developed.
Due to its high brightness, monochromaticity, and directivity, it has various applications in phosphorography technology. being researched. However, when using an excimer laser, there are many cases where irregularities occur on the mask surface, wafer surface, etc. due to the inherent coherency of the laser, imperfections in the striped surface or surface, and the optical characteristics of the illumination system. Interference fringes, so-called speckles, occur. This speckle causes uneven illumination and burn-in, which causes errors and reduces the resolution of the mask pattern image.

(Objective of the present invention) The present invention aims to reduce speckles that occur when using a high-intensity light source with good coherence, such as a laser, and to provide a companion illumination device that enables uniform illumination.

A further object of the present invention is to reduce speckles that occur on the mask surface and surface when using a highly coherent light source such as an excimer laser, and to manufacture semiconductors that enable high resolution of mask pattern images. An object of the present invention is to provide an illumination device suitable for an exposure apparatus for use.

(Main features of the present invention) A light source, a light guiding means for causing a light beam from the light source to enter a fly's eye lens forming a secondary image of the light source at various incident angles, and a means for superimposing the light beams and irradiating the surface to be irradiated.

Other features of the invention are described in the examples.

(Embodiment) FIG. 1 is a schematic diagram of a part of an optical system of an embodiment when the present invention is applied to an exposure apparatus for semiconductor manufacturing. 1 in the diagram
2 is a light source emitting a highly coherent light beam such as an excimer laser; 2 is a light beam emitted from the light source 1; 3 is a rotating mirror that rotates or vibrates as shown by the arrow in order to deflect the light beam 2;
4.5 are convex lenses, each of which forms an afocal converter 45* for emitting the entire reflected light beam from the rotating mirror 3 at a predetermined angle. Reference numeral 6 denotes a fly-eye lens having a plurality of minute lenses. 7 is an illumination system, and 8 is a mask surface as an irradiated surface.

A light beam 2 emitted from a light source 1 is scanned by a rotating mirror 3 and enters an afocal converter 45 at various angles. The parallel light flux emitted from the afocal converter 45 enters each minute lens of the fly's eye lens. In this embodiment, the rotating mirror 3 and the afocal converter 45 constitute the entire light guiding means. The exit surface of the fly's eye lens 6 becomes a secondary light color mixture, and the light flux emitted from the fly's eye lens 6 illuminates the mask surface 8 by the illumination system 7. The circuit pattern on the mask surface 8 is projected onto the surface of the sea urchin by a projection system (not shown) or is directly transferred onto the surface of the sea urchin.

In this embodiment, a certain point 81 on the mask surface 8 is illuminated by a light beam that has passed through a plurality of microlenses constituting the fly's eye lens 6. Among the light beams converging on one point 81 on the mask surface 8, different phases 7 of the light beams emitted from the microlenses are different from each other.

In this embodiment, the rotary mirror 3 is rotated to variously change the angle of incidence of the light beams incident on the fly-eye lens 6, thereby providing various phase differences between the respective light beams emerging from each minute lens of the fly-eye lens 6. This changes the phase difference between the respective light beams converging on one point 81. Thereby, uniform illumination of the mask surface 8 is achieved by reducing the coherence between the respective light beams and preventing the occurrence of interference fringes.

Figure 2 shows 2j of the tiny lenses of fly-eye lens 6.
), the light beams passing through these microlenses are illuminated by the illumination system 7 on the mask surface 8.
One point P above. It is an explanatory view when irradiating. Note that for ease of explanation, -Po is a point on the optical axis.

In the figure, lens surface 2 of microlens 6-1.
When the parallel light beams are incident on the person □ and 2A2, they converge on the other lens surfaces 2B and 2B2.5 and the minute lens 6-1
．． 6-2 each has its own configuration. That is, in the same figure, for example,
Bright, lens surface 2 of microlens 6-1.8-2 from system 7 side
When the parallel light beam LA, , Li2 is incident on B, , 2B2, the light beam LA, .

LA is a point 2C112 on lens surfaces 2A□ and 2A2, respectively.
It is configured to converge to C2.

In the congruent diagram, two parallel light beams "1' L2 enter the microlenses 6-1, 6-2 perpendicularly, that is, at an incident angle O, pass through the microlenses 6-1°6-2, and enter the illumination system. 7 is used to irradiate one point Po on the optical axis.Next, each point 2C□, 2C2 of the microlens 6-1.6-2
The luminous flux LA,.

If LA2 is incident at an incident angle θ and is assumed to be @, these light beams LA and LA2 are aligned with the optical axis from the lens surfaces 2B□ and 2B2.

The illumination system 7 irradiates the point Po. This and 1! ! Two luminous fluxes LA□.

LA20 phase difference Δφ is 2π Δφ−1・dsinθ ・・・・・・・・・il
It becomes lλ. That is, point P is obtained by changing the incident angle θ to the microlens according to equation (1). can be irradiated with light beams having various retardation values. This averages out the phase difference between the irradiated beams and lowers the coherence.

In this embodiment, the angle of incidence of the light beam incident on the microlens is changed by scanning the light beam with the rotary mirror 3. At this time, the displacement amount of the phase difference between each light beam should be, for example, 2π or more between the light beams from adjacent microlenses, so that the bright and dark pattern due to interference is repeated one or more times on the mask surface. This is preferable because the amount of irradiated light is more averaged.

In the explanation of FIG. 2, for the sake of simplicity, one point P on the optical axis of the illumination system 7 will be used.

However, a phase difference can be similarly given to points off the optical axis.

In this way, in this embodiment, the occurrence of speckles on the irradiated surface B is reduced.

In this embodiment, an acousto-optic element may be used instead of the rotary mirror to change the diffraction angle of the incident light beam, thereby providing a phase difference between each light beam. According to this, since there is no rotating part, the device is simplified.

(Effects of the Invention) According to the present invention, by changing the entire incident angle of the light beam incident on the shift eye lens by the light guide means, coherence is lowered and speckle generation is reduced. A lighting device that allows uniform illumination can be achieved.

In particular, if a high brightness light source such as an excimer laser is used and applied to exposure equipment for semiconductor manufacturing, uniform illumination of the ask surface will be possible, high resolution will be obtained, and a complete illumination system will be achieved with high efficiency and high throughput. can do.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a schematic diagram of a part of the optical system of an embodiment when the present invention is applied to an exposure apparatus for semiconductor manufacturing, and FIG. FIG. In the figure, 1 is a light source, 2 is a luminous flux, 3 is a rotating mirror, 45
is an afocal converter, 6 is a fly-eye lens,
7 is an illumination system, and 8 is an illuminated surface. t￥f Applicant: Canon Co., Ltd. Figure 1

Claims (2)

[Claims] (1) A light source, a light guiding means for making the light beam from the light source enter the fly's eye lens at various angles of incidence, which forms a secondary image of the light source, and a light guide device that superimposes the light beam diverging from the secondary image. 1. An illumination device comprising means for irradiating a surface to be irradiated. (2) The light source emits a highly coherent light beam, and the light guiding means has an optical scanning system, and the scanning system causes the light to enter the fly's eye lens at various angles of incidence. The lighting device according to claim 1, characterized in that: