JPH0332016A - Apparatus for controlling amount of projected light - Google Patents

Abstract

PURPOSE:To control the amount of projected light on a plane under illumination highly accurately for a long period even if high output power laser is used by providing a transparent glass piece without a coating film in a light path, reflecting part of luminous flux, and using a signal detected with a detecting means. CONSTITUTION:Part of light from a light source 10 is reflected with a transparent glass piece 13 without coating film and detected with a photodetector 17c of a detecting means 17. Meanwhile, the light transmitted through the glass piece 13 is projected on a mask 19 at a light condensing system 15a through a plane under illumination 14. The ratio between the amount of light which is reflected from the glass piece 13 and detected with the photodetector 17c and the amount of light which is projected on the plane to be illuminated 14 is obtained beforehand. Therefore, the amount of the projected light on the plane under illumination 14, i.e., the surface of the mask 19, can be detected. In this way, even if high output-power laser is used as the power source, the amount of the projected light on the plane under illumination can be controlled highly accurately for a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an irradiation light amount control device, for example, a mask or mask on which an electronic circuit pattern is formed using a beam from a high-output light source such as an excimer laser. The present invention relates to an irradiation light amount control device suitable for an exposure apparatus for semiconductor manufacturing, etc., which can control the amount of irradiation light on an irradiated surface with high precision when irradiating an irradiated surface such as a reticle surface.

(Prior Art) In recent semiconductor manufacturing technology, as electronic circuit patterns become more highly integrated, there is a need for lithography technology that can form high-density electronic circuit patterns.

Among these, excimer lasers and the like having an oscillation wavelength in the deep UV region have been proposed for various applications in phosphorography technology because of their high brightness, monochromaticity, and good directivity.

In general, in the manufacturing process of semiconductor manufacturing equipment, patterns provided on a reticle or mask (hereinafter collectively referred to as "mask") are sequentially transferred onto the wafer surface in an overlapping manner. in this case,
The pattern on the mask surface is transferred onto the wafer surface by illuminating the mask while it is held in close contact with or very close to the wafer surface using a lighting device, or the pattern on the mask surface is transferred to the surface using a projection lens. It is projected and transferred onto the surface.

In this case, the image quality of the pattern transferred onto the wafer surface is greatly influenced by the performance of the illumination device, such as fluctuations in the amount of light irradiated on the irradiated surface.

The present applicant has disclosed a light amount control device which controls the amount of irradiated light on a surface to be irradiated to a predetermined value and which is particularly suitable for an exposure apparatus for semiconductor manufacturing, for example, in JP-A-62-187815 and JP-A-63- This is proposed in Publication No. 193130.

The light amount control devices proposed in these publications place interference filters and deflection elements in the optical path, and control the amount of light irradiated onto the irradiated surface by detecting the amount of light reflected or deflected by these optical elements. ing.

(Problems to be solved by the invention) As one of the conventional light amount control devices, a half mirror for light splitting is arranged in the optical path to reflect and split a part of the exposure light and guide it to the detection means. Generally, a half mirror is coated with a coating such as an antireflection film so that a predetermined amount of light is guided to the detection means.

However, when far-ultraviolet, high-output light such as an excimer laser is used as a light source for illumination, the coating film of the half mirror is altered by the light irradiation, and its optical characteristics change. For this reason, when such a half mirror is used, there is a problem in that it becomes difficult to control the amount of irradiated light on the irradiated surface with high precision.

For example, if the amount of light incident on the half mirror is 100%, the reflectance from the half mirror is 4%, and the reflectance from the antireflection film is 0.1%, then the amount of light reflected by the half mirror and incident on the detection means is 4.1%. On the other hand, the amount of light that passes through the half mirror and enters the illuminated surface is 95.9%.
becomes.

At this time, the antireflection film changes in quality due to light irradiation, and the reflectance becomes 0.
．． If it changes from 1% to 1%, the amount of light that enters the detection means will be 5%, and the amount of light that will pass through the half mirror and enter the irradiated surface will be 95%. As a result, the amount of light incident on the irradiated surface as a change in the amount of light before and after the deterioration of the antireflection film is 0.
The light intensity changes by 9%, and the amount of light incident on the detection means changes by 22%. However, if the amount of light irradiated onto the irradiated surface is determined based on the signal from the detection means, it becomes very difficult to control the amount of light with high precision.

In the present invention, a light splitting means made of a material whose optical characteristics are hard to change with respect to the irradiated light is arranged at an appropriate position in the optical path from the light source for illumination to the irradiated surface, and the irradiation is divided by the light splitting means. An object of the present invention is to provide an irradiation light amount control device that can control the amount of irradiation light onto a surface to be irradiated to a preset value by detecting a part of light (n-destination light).

(Means for Solving Problems) The irradiation light amount*Jm device of the present invention includes a transparent member having no coating film on the light passing surface, which is disposed in the optical path between the light source and the surface to be irradiated. The light beam reflected by the light beam is detected by a light detection means, and the amount of light irradiated onto the irradiated surface is controlled by a control means using an output signal from the light detection means.

In particular, the present invention is characterized in that the transparent member is made of parallel plane glass of quartz or fluorite.

(Embodiment) FIG. 1 is a schematic block diagram of an embodiment in which the present invention is applied to a projection exposure apparatus for semiconductor manufacturing. In the figure, 10 is a light source, for example, an injection locking type F excimer laser (wavelength 248.4n).
m). Reference numeral 11 denotes a light amount control means, which controls opening and closing of the shutter, controls the output of the light source 10, or controls the aperture diameter of the illumination optical system, as will be described later. 12 is an illumination optical system for illuminating an irradiated surface 14 such as a reticle or a mask; 13;
is transparent glass, and is made of parallel plane glass without a coating film, such as quartz or fluorite, which has good transmittance for short wavelength light whose optical characteristics do not change much with respect to the pulsed laser light from the light source 10. ing. Reference numeral 15a denotes a condensing system, which guides the light beam from the irradiated surface 14, such as a masking blade, to limit the exposure area to the reticle surface. 15b
is a projection optical system for projecting a circuit pattern on a reticle surface 19 onto an irradiated surface 16 which is a wafer surface. 17 is a transparent glass 13 for controlling the amount of light irradiated onto the irradiated surface 14;
This is a detection means for detecting reflected light from. 18 is a driving means for driving the light quantity control means 11 based on the output signal from the detection means 17.

In this embodiment, the illumination optical system 12 irradiates the irradiated surface 14 with the light beam from the light source 1 . At this time, a part of the irradiated light is reflected and split through a transparent glass having a known reflectance that is large enough to include the effective luminous flux placed in the optical path and guided to the detection means 17 . Then, the amount of irradiation light incident on the irradiated surface 14 is measured from the amount of light detected by the detection means 17. Based on the output signal from the detection means 17, the driving means 18 drives the light amount control means 11 to control the amount of light irradiated onto the irradiated surface 14. At this time, the light amount control means 11 adjusts the output intensity from the light source 10 or changes the aperture diameter of the illumination optical system 12 so that the amount of light irradiated onto the irradiated surface 14 becomes a preset value.

In this way, in this embodiment, by using transparent glass without a coating film, the surface to be irradiated can be irradiated with a constant amount of light over a long period of time.

In particular, since light in the ultraviolet region (wavelength 200 to 300 nm) has a strong chemical reaction, this embodiment is very effective when used as a light source for an F excimer laser or the like.

FIG. 2 is a schematic diagram of a main part when a part of FIG. 1 is constructed with specific optical elements. In this figure, the same elements as those shown in FIG. 1 are given the same reference numerals.

In the figure, a beam expander 3 converts a beam 2 from a light source 10 into a beam diameter of a predetermined size, and converts the beam 2 from a light source 10 into a secondary light source forming means 4 such as a so-called optical inch grater for forming a plurality of secondary light source surfaces. It is incident. Then, the light beam from the secondary light source forming means 4 is condensed by a condenser lens 5,
The irradiated surface 14 is irradiated. At this time, a part of the illumination light beam is reflected and split by a parallel plate-shaped transparent glass 13 made of quartz, fluorite, etc. without using a coating film, etc., so that the optical characteristics do not change with respect to the irradiated light, and then sent to the light receiving element. The light is focused on a field stop 17b via a light amount adjustment filter 17a such as an ND filter that adjusts the amount of light. The amount of light passing through the field stop 17b is detected by the light receiving element 17c.

On the other hand, the light beam passing through the transparent glass 13 is guided to an irradiated surface 14 such as a masking blade, and the mask 19 is illuminated by the light beam from the irradiated surface 14 using a condensing system 15a. Then, the pattern on the mask 19 surface is projected onto the wafer 16 surface at a predetermined magnification by the projection optical system 15b.

In this embodiment, the ratio of the amount of light reflected by the transparent glass 13 and detected by the light receiving element 17c of the detection means 17 and the amount of light irradiating the irradiated surface 14 is determined in advance.

The amount of light irradiated onto the irradiated surface 14, that is, the surface of the mask 19, is controlled with high precision using the value obtained at this time and the signal obtained from the light receiving element 17c.

For example, the reflectance of one surface of the transparent glass 13 is about 4% for ultraviolet light and far ultraviolet light. Therefore, the amount of light incident on the light receiving element 17c is about 8
%. The amount of reflected light at this time is used to control the amount of light irradiated onto the irradiated surface as described above.

(Effects of the Invention) According to the present invention, the above-mentioned transparent glass without a coating film is disposed in the optical path of the illumination optical system, a part of the irradiated light beam is reflected and split and detected by the detection means, and the light from the detection means is By using the signal, it is possible to achieve an irradiation light amount control device that can control the irradiation amount of light onto a surface to be irradiated with high precision over a long period of time even when a high-power laser such as an excimer laser is used as a light source.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention applied to an exposure apparatus for semiconductor manufacturing, and FIG. 2 is a schematic diagram of a main part when a part of FIG. 1 is constructed with specific optical elements. be. In the figure, 10 is a light source, 11 is a light amount control means, 12 is an illumination optical system, 13 is a transparent glass, 14 is an irradiated surface, 15a is a condensing system, 15b is a projection lens, and 16 is a projection surface (surface for sea urchins)
, 17 is a detection means, 18 is a driving means, 2 is a luminous flux, and 4 is a 2
The secondary light source forming means 5 is a condenser lens.

Claims (3)

[Claims] (1) A transparent member with no coating film on the light passing surface is arranged in the optical path between the light source and the irradiated surface, and the light flux reflected by the transparent member is detected by a light detection means, and the light beam is detected by the light detection means. An irradiation light amount control device, characterized in that the amount of irradiation light to the irradiated surface is controlled by a control means using an output signal of the irradiation target surface. (2) The irradiation light amount control device according to claim 1, wherein the transparent member is made of parallel plane glass of quartz or fluorite. (3) The transparent member is provided in an optical path between a secondary light source forming means for forming a plurality of secondary light sources with a light beam from a light source and an irradiated surface. irradiation light amount control device.