JPH0540240A - Illumination optical system - Google Patents

Abstract

PURPOSE:To provide the illumination optical system which resolves problems such as the reduction of resolution caused by speckle or the nonuniformity of illumination, suppresses the generation of the speckle, more uniformly illuminate the surface of a reticule, detects an exposed variable and controls a proper exposed variable. CONSTITUTION:This system is composed of a first light source image generating means 2 to generate plural light source images by using beams emitted from a laser beam source 2, biaxial oscillating mirror 8 to scan the beams from the first light source image generating means 2, second light source image generating means 10 to generate plural light source images by using the beams scanned by the biaxial oscillating mirror 8, condenser lens 15 to irradiate the surface of a reticule 16 in the state of overlapping the beams emitted from the second light source image generating means 10 and laser output control circuit 23 to fixedly control the exposed variable detected by an exposed variable detecting means 13 by arranging the exposed variable detecting means 13 just behind the second light source image generating means 10 so as to integrate and detect the exposed variable caused by the pulsed laser beams.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optimum illumination optical system for uniformly illuminating a reticle surface using a laser beam as a light source in a semiconductor exposure apparatus.

[0002]

2. Description of the Related Art In recent years, the miniaturization of circuit patterns of semiconductor devices, especially super LSIs, and the progress of high integration have been remarkable,
The line width of circuit patterns is advancing to submicrons of 1 μm or less. In order to enable miniaturization and high integration of this pattern, a semiconductor exposure apparatus capable of obtaining higher resolution is required.

Generally, the shorter the wavelength used, the better the resolution, and an ultra-high pressure mercury lamp or a xenon mercury lamp was also used as a light source for illumination, but the light flux from these light sources has no directivity and is low. Due to the brightness, the exposure time was long and it was difficult to obtain high throughput.
On the other hand, recently, a semiconductor exposure apparatus using an excimer laser having a wavelength in the deep ultraviolet region of 250 nm or less as a light source for illumination has been put into practical use.

The illumination optical system of the conventional semiconductor exposure apparatus will be described below. FIG. 4 is a schematic configuration diagram of a conventional semiconductor exposure apparatus, which is disclosed in JP-A-64-37837. In FIG. 4, reference numeral 41 is an exposure mechanism section. An illumination light source 42 is a light source such as an excimer laser. 43 is a mirror, 44 is a concave lens, 4
Reference numeral 5 is a convex lens. Concave lens 44 and convex lens 45
Has a role as a beam expander and expands the beam diameter of the laser to approximately the size of the fly-eye integrator 47. Reference numeral 46 is a mirror, and 47 is a fly-eye integrator for uniformly illuminating the reticle 50. 48 is a mirror,
A condenser lens 49 collimates the beam emitted from the fly-eye integrator 47. 50 is a reticle on which a circuit pattern is drawn, 51 is a reticle 5.
A reticle holder that holds 0 by suction, 52 is a reticle 50
Is a projection lens for projecting the pattern, and 53 is a wafer on which the pattern is printed. 54 is an XY stage,
The wafer 53 is sucked and held, and is moved in the XY directions when baking is performed. Reference numeral 55 is a surface plate of the exposure mechanism section.

The operation of the semiconductor exposure apparatus configured as described above will be described below.

First, the beam emitted from the excimer laser light source 42 is reflected by the mirror 43 and expanded by the beam expanders 44 and 45. The expanded beam is reflected by the mirror 46, and the fly-eye integrator 47 generates a plurality of light source images. A plurality of light source images emitted from the fly-eye integrator 47 are reflected by the mirror 48, collimated by the condenser lens 49 in a superposed state, and uniformly illuminate the reticle 50. The circuit pattern drawn on the reticle 50 is projected onto the wafer 53 by the projection lens 52, and the pattern is printed.

FIG. 5 is a schematic configuration diagram of a conventional illumination optical system, which is disclosed in JP-A-59-226317.

In FIG. 5, reference numeral 61 is an illumination light source, which is a light source such as an excimer laser. The laser beam emitted from the laser light source 61 is focused on a spot by the scanning optical device 62 and is two-dimensionally scanned on the scanning surface 63. The light beam from the scanning surface 63 is converted into a parallel light beam by the collimator lens 64 having a focal point on the scanning surface 63 and is incident on the fly-eye lens 65. The beam emitted from the fly-eye lens 65 illuminates a reticle 67 on which a circuit pattern is drawn by a condenser lens 66, and the pattern is printed on a wafer 69 by a projection lens 68.

[0009]

With the recent increase in the degree of integration of VLSIs, higher uniformity of illumination has been required. However, in the conventional configuration described above, When laser light is used, the laser light has high coherence, so speckles (interference fringes) are generated on the reticle surface only by using the fly-eye integrator, and it becomes difficult to obtain sufficient uniformity. ing. In addition, there is a problem in that when trying to obtain a submicron high resolution of 1 μm or less, the resolution is lowered due to the influence of speckles and the like.

Further, since the excimer laser is a pulse oscillation system, there is a problem that a conventional exposure amount control system, that is, a system for controlling a time set by a timer using a shutter cannot be used.

The present invention solves the above-mentioned problems of the prior art and suppresses speckle generation, illuminates the reticle surface more uniformly, and detects the actual exposure amount and controls the appropriate exposure amount. The purpose is to provide an optical system.

[0012]

To achieve this object, the present invention provides a plurality of light source images using a light source that emits pulsed laser light for illuminating an object and a beam emitted from the light source. A first light source image generating means, a scanning means for scanning the beam from the first light source image generating means, and a second light source for generating a plurality of light source images using the beam scanned by the scanning means. The image generation means and the irradiation means for irradiating the surface to be irradiated with the beams from the second light source image generation means are superimposed.

[0013]

According to the present invention, according to the above construction, the plurality of beams generated by the first light source image generating means are scanned by the scanning means to be incident on the second light source image generating means, and the second light source image generating means. It is separated into a plurality of beams generated in. As a result, the uniformity of illumination can be more excellent, and at the same time, the generation of speckles can be suppressed.

Further, by providing the control means for controlling the laser light source when the exposure amount detected by the exposure amount detecting means becomes constant, the proper exposure amount can be easily controlled.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a semiconductor exposure apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 1 is an exposure mechanism section. An illumination light source 2 is, for example, an excimer laser light source. 3 is a mirror, 4 is a concave lens, and 5 is a convex lens. The concave lens 4 and the convex lens 5 have a role as a beam expander, and expand the beam diameter of the laser to approximately the size of the fly-eye integrator 6. Reference numeral 6 is a first fly-eye integrator for uniformly illuminating the reticle 16, and the fly-eye integrator 6 is configured by joining a large number of square columns as shown in the plan view of FIG.
Both end surfaces of each quadrangular prism are formed as convex spherical surfaces, and have a positive lens function. Reference numeral 7 is a convex lens, and 8 is a scanning means for scanning the beam emitted from the first fly-eye integrator 6 in two directions of both X and Y directions, which has a rotation axis of two axes, and a driving means such as a piezoelectric element. It is a swinging mirror that swings by. 9 is a convex lens, and 7 is a convex lens.
Reference numerals 9 and 9 serve as collimating lenses for collimating the beam emitted from the first fly-eye integrator 6.

Reference numeral 10 denotes a second fly-eye integrator for uniformly illuminating the reticle 16, which has the same configuration as the first fly-eye integrator 6 and has the first fly-eye integrator 6. The incident surface of 1 and the exit surface of the second fly-eye integrator 10 are maintained in a substantially conjugate relationship. Reference numeral 11 is a beam splitter that reflects the laser beam emitted from the fly-eye integrator 10 by several percent, and 12 is a condenser lens that condenses the laser beam reflected by several percent. Reference numeral 13 denotes an exposure amount detecting means for detecting the laser beam condensed by the condenser lens 12, which is, for example, an ultraviolet photosensor. 22
Is a light amount integrating circuit that integrates the light amount detected by the UV photosensor, and 23 is a laser output control circuit that controls the laser output.

Reference numeral 14 is a mirror, and 15 is a condenser lens, which is a two-stage fly-eye integrator 6 and 1.
The beam emitted from 0 is collimated. Reference numeral 16 is a reticle on which a circuit pattern is drawn, 17 is a reticle holder that holds the reticle 16 by suction, 18 is a projection lens that projects the pattern of the reticle 16, and 19 is a wafer on which the pattern is printed. Reference numeral 20 denotes an XY stage that holds the wafer 19 by suction and moves in the XY directions when baking is performed. Reference numeral 21 is a surface plate of the exposure mechanism section.

The operation of the semiconductor exposure apparatus configured as described above will be described below.

First, the beam emitted from the excimer laser light source 2 is reflected by the mirror 3 and expanded by the beam expanders 4 and 5. The expanded beam is incident on the fly-eye integrator 6 which is the first light source image generating means. The focal length of the convex surface on the incident surface side of the fly-eye integrator 6 is almost equal to the thickness of the fly-eye integrator 6, so that the beam incident on the fly-eye integrator 6 is made incident on the exit surface side by each quadrangular prism lens element. The light is condensed in the vicinity of each convex surface, and N (N is an integer) spot images are formed. The formed spot image is scanned by an oscillating mirror 8 which oscillates in two axes of an X axis and a Y axis by a driving method of a piezoelectric element or the like. The N spot images scanned by the oscillating mirror 8 generate N × M (M is an integer) light source images by the fly-eye integrator 10 which is the second light source image generating means. For example, when the spot image is scanned along the locus as shown in the perspective view of the scanning surface of FIG.
On the exit surface of each quadrangular prism lens element as shown in the perspective view of the exit surface of the fly-eye integrator 10 in (b), all spot images are scanned along a locus of a shape similar to the locus of the scanning surface, A plurality of N × M spot images are simultaneously scanned on the entire exit surface of the integrator 10. A plurality of light source images emitted from the fly-eye integrator 10 are transmitted by 90% by the beam splitter 11, the transmitted beams are reflected by the mirror 14, are collimated by the condenser lens 15 in a superposed state, and are uniformly distributed on the reticle 16. To illuminate. The circuit pattern drawn on the reticle 16 is projected onto the wafer 19 by the projection lens 18 and the pattern is printed.

Fly eye, which is the second light source image generating means
The beam emitted from the integrator 10 is reflected by the beam splitter 11 by several%, and the reflected beam is collected by the condenser lens 1.
The light beam condensed by 2 is input to the ultraviolet photosensor 13. The output of the UV photosensor 13 is
It is input to the light amount integrating circuit 22. The output of the light amount integration circuit 22 is input to the laser output control unit 23, and controls the laser light source 2 when the pre-input appropriate exposure amount is reached.

As described above, according to the present embodiment, by providing the swing mirror in the middle of the two-stage fly-eye integrator, it is possible to obtain uniform and uniform illumination without lowering the light amount, and to integrate the light. Proper exposure can be achieved by installing an exposure monitor.

[0023]

As described above, according to the present invention, the scanning means is provided in the middle of the two-stage light source image generating means, and the plurality of beams generated by the first light source image generating means are scanned by the scanning means. Since it is made incident on the second light source image generating means and separated into the plurality of beams generated by the second light source image generating means,
The uniformity of the illumination is better and at the same time
Generation of speckles can be suppressed.

Further, by providing the control means for controlling the laser light source when the exposure amount detected by the exposure amount detecting means becomes constant, the proper exposure amount can be easily controlled.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a semiconductor exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view of a fly-eye integrator according to an embodiment of the present invention.

FIG. 3 is a perspective view of a scanning surface according to an embodiment of the present invention, and a perspective view of a fly-eye integrator exit surface according to an embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a conventional semiconductor exposure apparatus.

FIG. 5 is a schematic configuration diagram of a conventional illumination optical system.

[Explanation of symbols]

 1 exposure mechanism part 2 illumination light source part 3 mirror 4, 5 beam expander 6, 7 fly eye integrator 8 swinging mirror 9, 10 fly eye integrator 11 beam splitter 12 condensing lens 13 exposure amount detecting means 14 mirror 15 condenser Lens 16 Reticle 17 Reticle Holder 18 Projection Lens 19 Wafer 20 XY Stage 21 Surface Plate 22 Light Quantity Integration Circuit 23 Laser Output Control Section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshito Nakanishi, 3-10-10 Higashisanda, Tama-ku, Kawasaki City, Kanagawa Prefecture Matsushita Giken Co., Ltd. (72) Takeo Sato 3 Higashimita, Tama-ku, Kawasaki City, Kanagawa Prefecture Chome 10-1 Matsushita Giken Co., Ltd.

Claims (5)

[Claims] 1. A light source that emits pulsed laser light for illuminating an object, a first light source image generating means that generates a plurality of light source images using a beam emitted from the light source, and the first light source image generating means. Scanning means for scanning the beam from the light source image generating means, second light source image generating means for generating a plurality of light source images using the beam scanned by the scanning means, and the second light source image generating means. An illumination optical system comprising: an irradiation unit that irradiates the surface to be irradiated with the beams from the laser beams superimposed on each other. 2. The first light source image generating means and the second light source image generating means are composed of a condenser lens and a fly's eye integrator, and the incident surface of the first light source image generating means and the second light source image generating means. 2. The illumination optical system according to claim 1, wherein the emission surface of the light source image generating means is maintained in a substantially conjugate relationship. 3. The scanning means has a rotation axis in two directions, and
2. The illumination optical system according to claim 1, wherein the illumination optical system makes a swinging movement in a direction. 4. An exposure amount detecting means for integrating and detecting the exposure amount of the pulsed laser light, and a control means for controlling the exposure amount detected by the exposure amount detecting means to be constant. The illumination optical system according to claim 1. 5. The illumination optical system according to claim 4, wherein the exposure amount detecting means is arranged immediately after the second light source image generating means.