JPH0461330B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical exposure apparatus used in integrator and semiconductor device manufacturing.

More specifically, the present invention relates to an integrator devised to realize ultrafine processing in a photolithography process in semiconductor device manufacturing, and a reduction projection excimer exposure apparatus using the integrator.

BACKGROUND ART Conventionally, reduction projection type exposure apparatuses (steppers) using ultra-high pressure mercury lamps as light sources have been commercially available for microfabrication of semiconductor devices, particularly LSIs, VLSIs, etc. However, conventional steppers use the G-line (435 nm) and I-line (365 nm) of ultra-high pressure mercury lamps, so the resolution is 1.2 μm for the G-line and 1.2 μm for the I-line.
The limit was about 0.8 μm. At these wavelengths,
In the future, it will be nearly impossible to obtain the 0.5 μm resolution required for 4Mbit RAM and 16Mbit RAM production.

Therefore, in recent years, the wavelength of
Xecl (308nm), KeF (249nm), ArF (193nm)
The development of exposure equipment using excimer laser light sources such as the above is being considered.

Problems to be Solved by the Invention However, although the excimer light source can produce a large output, it is a small surface light source with a beam diameter of, for example, about 2 cm ² , so the illuminance varies within the surface.
It is about 10%, and it is necessary to change the beam shape to match the mask and reduction lens.

That is, it is necessary to widen the beam diameter with uniform illuminance so that the entire surface of the mask can be irradiated with light.

Therefore, in the present invention, a light dispersion plate (integrator) with excellent dispersion performance and capable of uniform dispersion is installed between the excimer light source having a certain spot diameter and the optical path of the reduction lens, and a light dispersion plate (integrator) is installed between the excimer light source having a certain spot diameter and the reduction lens. to widen the beam diameter with uniform illuminance,
The purpose is to uniformly print a mask pattern onto the wafer surface.

Means for Solving the Problems That is, the present invention uses a synthetic quartz plate that is transparent from the visible light range to 200 nm as the base material of the light-transmitting substrate, and has a plurality of concentric circles on at least one main surface of the synthetic quartz plate. We will manufacture an integrator that can uniformly disperse the far-ultraviolet beam emitted from the excimer light source by forming recesses using the lens effect of each recess.

Furthermore, the present invention uses such an integrator in a reduction projection exposure apparatus using excimer light.

Effects The integrator of the present invention ensures more uniform light dispersion due to the unique concave portion, and is useful for optical devices that require uniformity of the light source.

Furthermore, by installing at least one integrator in the optical path of the excimer light source and the reduction lens, the beam diameter of the excimer light source can be uniformly expanded to the irradiation area required for the mask that performs reduction projection exposure, and the irradiation area of the wafer can be expanded uniformly. It is now possible to irradiate the entire surface with excimer laser light with uniform illuminance.
It becomes possible to obtain a uniform ultra-fine resist pattern.

Note that at this time, it is desirable to further install a condenser lens or similar optical component between the integrator and the mask in order to regulate the focal position.

Embodiment For example, as shown in FIG. 1, an excimer light source 1 that emits excimer laser light, an optical mirror 2, an integrator 3, a condenser lens 4, a mask holder 5 that holds a mask 5A, a beam splitter 6, and a reduction projection lens 7 , a main body 9 consisting of a wafer stage 8 on which a semiconductor wafer 8A is placed, an alignment lens 11, an alignment beam splitter 12, and an alignment light source 1.
3. As an integrator used in an excimer exposure apparatus consisting of an alignment optical system 15 consisting of an image reading camera 14 and a computer 16 that processes image signals obtained from the alignment optical system and controls movement of the wafer stage,
Shapes as shown in Figures 2 to 5 (for example, 2cm~
(approximately 4 cm square) (round may also be used).
That is, FIG. 2 shows a plurality of concentric dish-shaped recesses 22 (22a, 22b, 2
2c, 22d) and an integrator A whose surface is coated with anti-reflection multi-coating 23 (multilayer film). In this example, four concentric recesses (22a to 22d) are formed.

Next, the dispersive radiation characteristics of light of the integrator shown in FIG. 2 will be explained using FIG. 3. First, generally speaking, the incident light Lin emitted from the exier light source is 10%
For example, lights ₄ , ₅ , and ₆ near the central axis are relatively strong;
Lights ₁ , ₂ , ₃ , ₇ , ₈ , _{and g} in the peripheral area are weak.
The light incident on each of the circumferential dish-shaped recesses 22a to 22c of the substrate 21 is spread into each recess, and
The light is dispersedly emitted from the substrate 21 as dispersed emitted light Lout. ₁ ′ to ₉ ′ indicate the synchrotron radiation from ₁ to ₉ , respectively. A location a certain distance X away from the substrate 21 (for example, the position of the condenser lens 4 in FIG.
For example, the recess 22
The light incident on b spreads over the entire Y area, and the light incident on the recess 22c also spreads over the entire Y area. Therefore, in Y, both strong and weak parts of the incident light Lin irradiate the entire Y surface, resulting in a very uniform irradiation intensity within the Y plane. Moreover, since the integrator shown in Figure 2 has concentric recesses,
Since the dispersion state shown in FIG. 3 occurs in the 360° direction, a uniform illuminance distribution can be obtained over the entire Y area. Note that X is selected to be approximately 50 cm to 1 m, for example, but the size of the surface Y with uniform illuminance and the distance X
can be determined by selecting the curvature of each of the recesses 22a to 22d. Also, each recess 22a to 22d
may have different curvatures, improving uniformity.

Therefore, if the Y plane is selected, for example, at the position of the condenser lens 3 in the exposure apparatus shown in FIG. 1, it becomes possible to irradiate the photomask 5A with light having a uniform illuminance distribution over the entire surface. This means that
When printing the pattern of the mask 5A onto the resist on the wafer 8A through the reduction projection lens 7, exposure can be performed with uniform illuminance, which is extremely effective for forming submicron patterns. Note that this exposure with uniform illuminance becomes more effective as the pattern width becomes narrower, and is also convenient for forming ultra-fine patterns of 0.5 μm or less. Furthermore, compared to ultra-high pressure mercury lamps, which normally have a variation in illuminance of about 2.5%, laser light from an excimer light source has a large illuminance variation (variation) of about 10%, and a 360° beam as shown in Figure 2.
An integrator that can obtain a uniform illuminance distribution in all directions, that is, over the entire Y plane, is extremely effective for exposure apparatuses using excimer light sources. The condenser lens 3 is a so-called focusing optical system for regulating the focus, and may be a concave mirror or the like.

For example, consider the case where a positive resist pattern 201 with a width of 2 μm and a resist pattern 202 with a width of 0.5 μm are formed on a semiconductor substrate 200. When forming a resist pattern by reduction projection exposure, if the exposure illuminance of the light L _P increases by 5 to 6% in a certain exposure area on the semiconductor substrate 200, the pattern size will normally become narrower by about 0.2 μm on one side. At this time, as shown in FIG. 7a, the resist pattern 20
1, 202 becomes thin like a broken line, and although a resist pattern 201 with a width of 2 μm is practically acceptable, a resist pattern 202 with a width of 0.5 μm becomes unusable or impossible to form a pattern.

On the other hand, if the integrator of the present invention is used to improve the variation in illuminance to about 2%, it becomes possible to suppress the narrowing to about 0.05 μm on one side in the area where the illuminance increases by about 2%. Therefore, as shown in FIG. 7b, the pattern thinning as indicated by the broken line in FIG. 7b is reduced, and the resist pattern 202 of, for example, 0.5 .mu.m can be used sufficiently for practical use, and the accuracy of pattern formation is improved. Note that the pattern expands in areas where the illuminance decreases, but in this case as well, the width of the resist pattern, which should originally be 0.5 μm, expands significantly, making it practically unusable. The same thing can be said for negative resists, except that the pattern thinning and expansion are opposite to the positive resists.

In this way, using the integrator of the present invention to reduce the variation in the illuminance of excimer light in the excimer exposure device to about 2% or less, for example,
It is extremely effective for forming resist patterns of about 0.5 μm or less.

In FIG. 4, concentric dish-shaped recesses are formed on both principal surfaces of a light-transmissive substrate 21, and the dish-shaped recesses 22a
~22c, recesses 32a~32d are formed on both main surfaces, and recesses 22a~22c and 32a~
32d, the bottom positions are shifted from each other between the two main surfaces. This type B integrator makes it possible to further shorten the distance X shown in FIG. 3 and to improve uniformity.

FIG. 5 shows an integrator that has the same structure as type B in FIG. 4 by stacking two pieces of type A in FIG.

Fig. 6 shows an integrator D that has a parallel dish-shaped recess 100 that is not concentric, and the degree of uniformity is inferior to that of Figs. For example, when the excimer light source emits a parallelogram beam, it is extremely convenient to first convert the beam shape to a square in D and then make it uniform in A to C types.

It goes without saying that the integrator of the present invention can be used with any optical device other than exposure equipment as long as it is necessary to widen the beam diameter.

Effects of the Invention By using the integrator of the present invention, even if an excimer light source with a small radiation area and large illuminance unevenness is used, it is possible to uniformly and easily widen the beam diameter so that uniform illumination can be provided over the entire mask surface.
In particular, when printing a submicron-order fine mask pattern onto the surface of a semiconductor wafer through a reduction lens optical system, it can be highly effective in preventing uneven exposure and maintaining resolution.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram for explaining the outline of an excimer exposure apparatus according to an embodiment of the present invention, and Fig. 2a
is a front view of an integrator according to an embodiment of the present invention, FIG. 2b is a sectional view taken along the line -' of FIG.
4a is a front view of an integrator according to another embodiment of the present invention, FIG. 4b is a sectional view taken along the line -' of FIG.
The figures are a sectional view of an integrator according to still another embodiment of the present invention, FIG. 6a is a front view of an integrator having a parallel dish-shaped recess, FIG. FIG. 2 is a diagram for explaining the influence of uneven exposure of a light source on a resist pattern. DESCRIPTION OF SYMBOLS 1... Excimer light source, 3... Integrator, 5... Mask holder, 6... Beam splitter, 7... Reduction projection lens, 8... Wafer stage, 15... Alignment optical system, 22...
... Concentric dish-shaped recess, 21 ... Light-transmitting substrate, 23
...Anti-reflection multi-coating, 201,20
2...Positive resist pattern.

Claims (1)

[Claims] 1. A plurality of concentric recesses are provided on at least one main surface of a light-transmissive substrate, and light incident from one or the other main surface of the substrate is directed from the other or one main surface. An integrator characterized by distributed radiation. 2. The integrator according to claim 1, wherein the recess is dish-shaped. 3. Claim 1, characterized in that a plurality of concentric recesses are provided on both main surfaces of the light-transmitting substrate.
Integrators listed in section. 4. The integrator according to claim 3, wherein the positions of the bottoms of the plurality of concentric recesses on both main surfaces are shifted from each other. 5. Claim 1, characterized in that the surface of the recessed portion is multi-coated for antireflection.
The integrator according to any one of Items 1 to 4. 6 Excimer light source, reduction projection lens, wafer stage, mask holder, integrator,
In the exposure apparatus including an alignment optical system, the integrator has a configuration in which a plurality of concentric recesses are provided on at least one principal surface of a light-transmissive substrate, and excimer light from the light source is directed to one of the integrators. Alternatively, an exposure apparatus characterized in that the wafer on the stage is irradiated with the wafer on the stage through the lens. 7. The exposure apparatus according to claim 6, wherein the integrator is placed within the light exposure area of the excimer light source and the reduction projection lens. 8. Claim 6, characterized in that the excimer light source emits KrF excimer laser light.
Exposure apparatus described in Section 1. 9. The exposure apparatus according to claim 6, characterized in that a converging optical system is disposed between the integrator and the reduction projection lens, and the converging optical system is installed on a uniform illuminance surface of the light emitted from the integrator. .