JPS6175523A - Apparatus for obtaining incoherent light flux - Google Patents

Abstract

PURPOSE:To obtain incoherent light flux having predetermined distribution of cross-section intensity from coherent light flux by reducing capability in interference of light flux. CONSTITUTION:In an apparatus for obtaining incoherent light flux (IC1), a plurality of half-mirrors 1 are arranged in parallel in a certain angle (45 deg.) for a certain angle [shape of beam should be rectangular in lateral direction (a) Xperpendicular direction (b)] to an incident light flux (I0), and distance lbetween adjacent half-mirrors 1 is set longer than the interference distance (coherent length) of incident light flux. However, the mirror surface 2 is finally provided. When the light fluxes emitted from the apparatus 3 for obtaining incoherent light flux are all collected, if it is assumed that there is no absorption by half-mirror 1, the incoherent output lift flux in such an intensity as the incident light flux (I0) can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for making a light beam incoherent, and in particular, when a laser beam is used as an illumination light source for semiconductor manufacturing equipment, the present invention relates to a light beam incoherence device for reducing the coherence of a light source that is harmful to fine pattern formation. This invention relates to an incoherent device.

There are various types of semiconductor manufacturing equipment such as contact, proximity, mirror projection, and stepper. FIG. 1 is a schematic diagram of a projection type semiconductor manufacturing apparatus, in which Is, AS, and PS represent an illumination system, an alignment system, and a projection system, respectively. Illumination light from an illumination system is applied to the mask M, and the pattern formed on the surface of the mask M is transferred to the wafer W side.

In the case of contact and proximity type semiconductor manufacturing equipment, there is no projection system PS, and in the case of mirror projection type, a scanning mechanism is added, but the overall arrangement of the illumination system, alignment system, etc. is similar to Figure 1. Basically no change.

Conventionally, ultra-high pressure mercury lamps or ultra-high pressure X e -Hg lamps have been commonly used as illumination light sources for semiconductor manufacturing equipment for forming fine patterns of LSIs and the like using photophosphorography. However, recently, high-output lasers (such as excimer lasers) in the ultraviolet range, which is the wavelength used in illumination light sources, have advanced and are attracting attention as new light sources for semiconductor manufacturing equipment. Advantages of using a high-output laser such as the above include high efficiency of a condensing optical system due to its high brightness or high directivity, but these are already known.

Here, the only drawback that can be considered in using laser light for printing fine patterns such as LSI is its high coherence. That is, the occurrence of speckles due to interference hinders the formation of fine patterns on the order of wavelengths. However, regarding this matter, the conventional excimer laser mentioned above has multimode oscillation and poor coherence, so there is no such problem. However, even when an excimer laser is used, if the oscillation wavelength l] is narrowed to 0.01n+m or less in special usage, for example by using an injection locking method, the coherence will improve and as mentioned above. problem will occur.

It is therefore an object of the present invention to provide a beam incoherence device that can solve the above-mentioned problems by reducing the coherence of the beam.

Another object of the present invention is to receive a coherent light beam and spread it one-dimensionally or two-dimensionally without losing its optical value, and to generate an incoherent light beam with an arbitrary (including uniform) intensity distribution within the cross-section of the beam. An object of the present invention is to provide a luminous flux incoherent making device M capable of obtaining a large luminous flux.

Preferred embodiments of the invention will now be described with reference to the accompanying drawings. FIG. 2 shows the basic configuration of a device 3 for making a beam incoherent according to the present invention, which receives a coherent beam and emits an incoherent beam.

The luminous flux incoherent device (IC+) of the present invention makes a certain angle (beam shape is a rectangle with horizontal direction a x vertical force direction a) with respect to an incident luminous flux (45 in the figure). '), a plurality of half mirrors (1) are arranged parallel to each other, and the distance #: between adjacent half mirrors 1 is made longer than the coherence hole lil& (coherent length) of the incident light beam. However, the final product will be a car with mirror surface 2.

Especially with such a configuration, when all the emitted light from the beam incoherent device 3 is collected, it becomes a half mirror.
Assuming that there is no absorption due to 1, an incoherent output beam with an intensity equal to the input beam (Io) is obtained. Moreover, the luminous flux can be expanded one-dimensionally. (The incident light beam in the lateral force direction a x longitudinal direction a is expanded to the lateral force direction a x longitudinal direction a.) Also, in this configuration, if the transmittance of each half mirror 1 is determined with a certain regularity, each The reflected light from the half mirror 1 can be made equal (1/n Io). Tsuma I
When you want to divide the amount of incident light into n equal beams using J (n-1) half mirrors 1 and one mirror 2, the transmittance (Ti%) of the first half mirror 1 is T i
= n - i / n + 1- i x 100.

FIG. 3 shows another embodiment of the present invention, in which a half mirror and a group of mirrors are integrated as a prism 4. When the half mirror 1 and the mirror 2 are arranged separately, the emitted light beams may not become parallel to each other due to angular errors in mounting each mirror. On the other hand, when integrated as a prism, as long as the prism angle is suppressed with individual precision, the light beams emitted from each surface will all be parallel. Also, in this case, the distance between adjacent half mirrors 1 may be expressed as ``(k/n)'', where n is the refractive index of the prism.

FIG. 4 shows the optical block shown in FIG. 3 expanded into a two-dimensional matrix. In this case, in order to make the emitted light beam uniform, it is preferable to determine the transmittance of each half mirror using the following equation. In other words, in the vertical direction counting from the incident light beam side,
Transmittance Tij of the jth half mirror in the horizontal direction
(%), Tij = (m-i/m+1-i)X
It is best to set it as (n-j/n+1-j) X 100.

In FIG. 5, five groups of microlenses (for example, fly's eye lenses) having the same focal length are provided for each exit window on the exit side of the optical block 4 shown in FIG. FIG. 6 shows a case where this optical block 4 and microlens 5 are applied to the semiconductor manufacturing apparatus shown in FIG. 1.

According to FIG. 6, a parallel beam of light emitted from a laser source (LS) passes through an optical block 6, and its optical path is bent at a right angle. Thereafter, the light -II'J is focused on the focal point F of the lens 5, and then transmitted through the mask M by the action of the condenser lens 7, and is focused on the pupil plane 8 of the projection system (PS), forming a group of bright spots. Then, the light source image (in this case, bright spot group) (E
S) is called an effective light source.

In comparison, an illumination method that focuses an illumination light source image on the pupil plane of the projection system is called Koehler illumination, and is a means of eliminating uneven illuminance on the object plane (mask M).

Further, by adopting the arrangement shown in FIG. 6, there is an advantage that the effective light source (ES) can be made uniform.

FIG. 7 shows an embodiment in which a -dimensional effective light source is rotated and averaged over time to create an equivalent two-dimensional effective light source. The optical block 9 for creating a one-dimensional effective light source shown in FIG. 7 can be applied to, for example, FIG. 6, and in this case the laser is incident from directly above FIG. ), rotate around axis c-c'. FIG. 8 shows an example in which the optical block 9 of FIG. 7 is applied to the optical block 9 of FIG.
This shows the state observed on the pupil 8 of the projection system when rotated around c'.

Although FIG. 9 has a different configuration from FIG. 7, it shows an example in which a one-dimensional effective light source is rotated and averaged over time to create an equivalent two-dimensional effective light source, as in FIG. 7. It is something. For example, the optical block 10 for creating a one-dimensional effective light source shown in FIG. 9 is applied to FIG.
Rotate around −σ. FIG. 10 shows a state when the optical block 10 of FIG. 9 is applied to FIG. 6 and rotated about the axis c-c' as observed on the pupil 8 of the projection system.

Next, FIG. 11 shows an embodiment of the present invention configured to create a two-dimensional effective light source without rotation.

In this case, the half mirror 1 has a conical shape or a truncated conical shape.
A plurality of mirrors 2, 13 and mirrors 14 are arranged concentrically.

The distance between adjacent half mirrors is set longer than the coherent length of the laser beam.

Also, in this case, a ring-shaped toric lens 15 is provided on the exit side.
Place them without any gaps. In Figs. 7, 9, and 11, the lens 5.15 is placed on the exit side, but in general, a large incoherent luminous flux can be obtained on the exit side without using it, and there is no light loss. do not have.

As explained above, according to the luminous flux incoherentization device of the present invention, an incoherent luminous flux having an arbitrary cross-sectional intensity distribution can be obtained from a coherent luminous flux.

Furthermore, when applied to semiconductor manufacturing equipment, it is possible to prevent deterioration of the resolution performance of the optical system due to speckles, etc., and it is possible to stably print fine patterns in the vicinity of lpm.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a projection type semiconductor manufacturing apparatus, FIG. 2 is a diagram showing the basic configuration of a beam incoherent device of the present invention, and FIG. 3 is another example of a beam incoherent device of the present invention. FIG. 4 is a diagram showing an example in which the optical block shown in FIG. 3 is expanded into a two-dimensional matrix. FIG. 5 is a diagram showing a case where a microlens group is arranged on the exit side of the optical block shown in FIG. 4. Fig. 6 shows a case where the luminous flux incoherence making device of the present invention is applied to semiconductor manufacturing equipment, and Fig. 7 shows a case in which a one-dimensional effective light source is rotated and averaged over time, and equivalently two-dimensional Figure 8 shows an example of creating an effective light source with axis c.
Figure 9 is a diagram showing the state observed on the pupil 8 of the projection system when rotated around -c' as the center. Figure 9 has a different configuration from Figure 7, but like Figure 7, it has a one-dimensional shape. Figure 10 shows an example in which an effective light source is rotated and averaged over time to create an equivalent two-dimensional effective light source. A diagram showing the state observed on the pupil 8 of the projection system when rotated about -c' as the center. Figure 11 is a book configured to create a two-dimensional effective light source without rotation. It is a figure showing an example of the invention. 1--half mirror, 12-m-mirror, 4-m-optical block, 5-m-microlens, 8-m-pupil plane. JP-A-Sho Gl-75523 (6)

Claims (5)

[Claims] (1) It has at least two optical elements into which a coherent light flux is incident, and in order to make the light flux emitted by the optical element incoherent, the distance between adjacent optical elements is set to the coherent length of the incident light flux. A device for making a luminous flux incoherent, which is characterized by making it longer. (2) The light beam incoherence device according to claim 1, wherein the optical elements are arranged one-dimensionally. (3) The light beam incoherence device according to claim 1, wherein the optical elements are arranged two-dimensionally. (4) The light beam incoherence device according to claim 1, wherein the optical element is a half mirror or a mirror. (5) The device for making a beam incoherent according to claim 1, wherein the optical element has various transmittances in order to obtain an arbitrary light intensity distribution within a cross section of the emitted beam.