JPS61117553A - Exposing device - Google Patents

Abstract

PURPOSE:To improve the utilizing efficiency of light and reduce the fluctuation of luminance, by condensing light radiated from a light source onto a rotary regular polyhedron mirror by means of a condensing reflecting mirror and projecting the optical beam reflected and expanded in the shape of a fan upon spherical mirrors. CONSTITUTION:Light from a light source 1 of a short-arc type mercury-arc lamp is changed to spot-like parallel light through a condensing reflecting mirror 2 having an elliptic cross section and projected upon a rotary regular polyhedron mirror 4 through plane mirrors 8 and an aspherical mirror 3. The polyhedron mirror 4 having a truncated pyramid-like shape is rotated by a motor M at a prescribed speed and light repeatedly scanned in a prescribed angle range in the from of a fan by the rotation of the mirror 4 becomes an arc-like slit of 1-4mm in width while it is repeatedly reflected by plural spherical mirrors 7 and plane mirrors 8. The arc-like light passing through a photomask 9 is repeatedly reflected among a trapezoidal mirror 10, concave mirror 11, and convex mirror 12 and forms a photomask pattern on a wafer 13 which is a body to be irradiated. By simultaneously moving the photomask 9 and wafer 13 in parallel with each other, the whole surface of a previously designated wafer can be exposed to the arc-like light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an exposure device that performs exposure by a scanning method, among devices that expose an object to be irradiated through a photomask.

[Conventional technology]

Exposure by the scanning method is used in various fields, but the most widely known case is exposure of bare semiconductor wafers. In order to speed up understanding, the explanation will be given below using a semiconductor wafer as an example.

IC manufacturing technology has also entered the realm of VLSI from LSI, and higher resolution is required for the lithography process as well.
became. The resolution 6 when using the optical system is given by the following equation.

0.8λ (1) ε=NA-(μm) Here, λ is the wavelength of light (μm), and NA is the refraction angle at the focal point F of the optical lens 23 shown in FIG. 0(2) This is a numerical value given by K, and is called the numerical aperture.

As can be seen from equation (1), in order to increase the resolution 8, it is possible to increase the numerical aperture NA or decrease the wavelength λ.
When the NA is increased, the problem of depth of focus arises. In other words, the depth of focus Δ is given by Δ, so as the NA increases, the depth of focus becomes shallower, causing defocus due to the flatness and unevenness of the wafer surface, and it is difficult to design an optical lens with an extremely large NA.

On the other hand, for example, the wavelength λ can be set to 365 by using an ultra-high pressure mercury lamp.
If we move to the ultraviolet region one after another (nm, 254nm, 185nm, etc.), the resolution will increase as the wavelength becomes shorter, but such ultraviolet rays are absorbed by ordinary optical lenses, and the materials of the lenses are limited. It becomes a thing.

For the above reasons, several exposure apparatuses have been developed that use a scanning method using a reflective optical system that does not cause problems such as absorption even when the wavelength λ is shortened.

In other words, this method utilizes the fact that the mask image is projected one-to-one onto the wafer using only the reflective optical system and only the circular arc portion (
USP 3,748,015 A, 0ffner) uses an arc-shaped mercury lamp and a short-arc type mercury lamp, and uses a reflective optical system to bring this light in an arc shape. [Problem to be solved by the invention] However, in the conventional scanning method semiconductor wafer exposure apparatus described above, an arc-shaped mercury lamp is used. In the case of the method used, there are problems such as variations in brightness over the arc length of the arc-shaped lamp and the need for severe cooling. In the case of the unfolding method, there were problems such as a low rate of capture of light from the light source by the reflective optical system and extremely poor light utilization efficiency.

[Means to solve the problem]

The exposure apparatus of the present invention includes a light source, a focusing reflector in which the light source is placed at a first focal position, and a shaft for creating spot-like parallel light placed in a position to receive light from the converging reflector. A removal optical system, a rotating regular polyhedral mirror that receives the spot-like parallel particles and reflects them repeatedly in a fan shape within a predetermined angular range, and a light beam that is repeatedly reflected in the fan shape is further reflected and expanded onto the photomask in an arc shape. The method includes a plurality of spherical mirrors that project the arcuate reflected light onto the irradiated object via the photomask, and simultaneously moves the photomask and the irradiated object to create a photomask pattern that is specified in advance. It is characterized in that it is projected one-on-one across the area by a scanning method.

[Effect]

In the present invention, first, a short-arc type mercury lamp can be used as a light source instead of an arc-shaped mercury lamp, so that the variation Φ in brightness is extremely small over the entire length of the arc-shaped luminous flux trace. The light emitted from the light source is then focused by a condensing reflector onto a rotating regular polyhedral mirror via an off-axis optical system for creating spot-shaped parallel light, and the light is reflected and expanded into a fan shape by this rotating regular polyhedral mirror. Since the beam is projected onto the spherical mirror, the light beam is reliably captured by the optical system including the spherical mirror, and the efficiency of light utilization is significantly improved.

〔Example〕

The present invention will be explained in detail with reference to the drawings.

In one embodiment of the present invention, as shown in FIG. 1, for example, a short arc type mercury rung is used as the light source 1, and the arc portion of the mercury lamp is placed at the focal point of a condensing reflector 2 having an elliptical cross section. position. The light reflected by the condensing reflector 2 is turned into spot-like parallel light by an off-axis optical system for creating spot-like parallel light. That is, after being reflected by a plane mirror 8, it is reflected by an aspherical mirror 6 for creating a spot-shaped parallel beam placed at or near a focal point, and this spot-shaped parallel beam is projected onto a rotating regular polyhedral mirror 4. . This rotating regular polyhedral mirror 4 has a truncated polygonal pyramid shape, and is rotated by a motor M at a predetermined speed.

Therefore, the parallel spot beam Fi projected thereon is repeatedly reflected and expanded in a fan shape, but by appropriately selecting the number of mirror surfaces of the polyhedral mirror 4, the angle of the fan shape can be arbitrarily determined.

The light, which is repeatedly scanned in a fan-like manner within a predetermined angle range by the rotation of the polyhedral mirror 4, is reflected repeatedly by the plurality of spherical mirrors 7 and plane mirrors 8, and due to the action of the spherical mirror 7, the light is scanned repeatedly within a predetermined angle range. The arc-shaped light passing through the photomask 9 is formed into a circular arc-shaped slit with a width of
0. concave mirror 11, convex mirror 12, concave mirror 11
, and the trapezoidal mirror 10, and the photomask pattern is imaged onto the wafer 13, which is the object to be irradiated. This arcuate beam is exposed by simultaneously moving the photomask 9 and the wafer 13 in parallel and projecting the photomask pattern over the entire area on the wafer surface specified in advance in a one-to-one scanning manner. It will be done.

In the exposure performed according to the present invention, as shown in FIG. 3, an arcuate light flux trace 31 formed on the surface of the wafer 13 is repeated in the Y-axis direction from A to BK with a slit width W at a speed of
The wafer 13 is scanned at a speed V in the X-axis direction. Therefore, if the speed V at which the spot moves on the arc is not made sufficiently larger than the speed V at which the arcuate light flux trace 51 moves on the surface of the wafer 16, uneven exposure will occur in the resist film on the wafer. Normally, exposure unevenness is required to be within ±5 inches, and in the present invention, as the spot beam repeatedly scans the arc-hi, the arc-shaped light beam trace 31 moves on the wafer 13. Exposure unevenness is determined by how many times the spot beam passes through a certain point. For example, as shown in Fig. 4, the spot beams are A, →B A, -B A, →
B, and when the velocity V at which the arc-shaped light beam trace shifts by one spot per movement is set, there are some places where the light flux trace passes once and places where it passes twice. That is, the point pFi shown in Fig. 4 is exposed when moving from → BIK, and the point qFi is exposed twice at the upper side of the arc when moving from A1 → B, K and at the lower side of the arc when moving to the person and horse. . Therefore, exposure unevenness increases, and the above conditions are not satisfied at all. Referring to the above example, the spot shift is 1/1 with one movement! , 1/4..., the number of times the spot passes (the number of exposures) and the exposure unevenness at a point where the spot may be shifted by the amount of the spot are K as follows.

Spot (QXV sea urchin...-face-F's arbitrary
Exposure A.

Number of exposures at the point Ospot 2 and 3 times 35 3 cheer 4
1 4th and 5th 20chi V6 #
6th and 7th 14.6ch'/8 #
8th and 9th times 11.1chi'/(o'I -
10 times and 11 times 91chi From this, in order to achieve exposure unevenness of 10- or less, the deviation of the arcuate light flux trace should be 1/1o or less of the spot width with one movement of the spot. .

Next, we will discuss the relationship between exposure unevenness and rotational speed of the polyhedral mirror when applied to exposure of a 6-inch diameter wafer. When exposing a wafer by the normal scanning method, the exposure time for one wafer is about 10 seconds, and the width of the arcuate slit is 4M, so these values are also applied in the present invention.

Since a 6-inch wafer has a diameter of approximately 150 m+, the moving speed V of the arcuate light flux trace in the X-axis direction is v = 150/10.
=15-/see. On the other hand, the distance the spot moves is 150×π/2−235× in one movement, assuming that the arc-shaped light beam trace moves half of the arc of Uni-no-. Also, if you move the spot by moving the arcuate light flux trace 10 times and moving it 4 cm as mentioned above, the exposure unevenness will be within 10 inches, so the distance traveled in the X-axis direction in one movement is '/10 =
It is 0.4-. On the other hand, as mentioned above, since the moving speed V of the arcuate light beam trace is 15-1, the number of times the spot moves during this period is 15"10.a = 37.5 times. Therefore, if the polyhedral mirror 4 is If it is a facepiece,
If it rotates once per second, there will be no problem with uneven exposure. And the moving speed of the spot Vd V= 235 x 37.5?
8800 .mu./w: and 'v/v-600. Therefore, if the moving speed of the spot is set to about 600 degrees of the moving speed of the arcuate light beam trace, the exposure unevenness Fi will be 10%.

Next, referring to the light utilization efficiency in the present invention,
The energy required for normal exposure is approximately 100 mJ, so the output of the mercury lamp to obtain this energy is:
Assuming that 5000 watts of electric power is converted into light of a predetermined wavelength and the light utilization efficiency is 70%, a mercury lamp of approximately 150 W will suffice. On the other hand, in the case of the above-mentioned method in which the light from the conventional mercury lamp is expanded as it is with a spherical mirror, a 2KW mercury lamp is required, and the power consumption is less than that of the conventional method, so the light is used more efficiently. is quite high.

〔Effect of the invention〕

As explained above, in the present invention, the light emitted from the light source is focused on a rotating regular polyhedral mirror by a condensing reflector, and the light beam that is reflected and expanded in a fan shape by this rotating regular polyhedral mirror is projected onto a spherical mirror. Therefore, the efficiency of using light from the light source is extremely high, and variations in brightness can be reduced. - Also, the ratio of the moving speed V of the spot beam to the scanning speed V that horizontally scans the wafer surface is ■/v
>600, exposure unevenness can be reduced to 10 inches or less, so there is no problem with exposure unevenness.

It should be noted that the present invention is not limited to the above-mentioned exposure apparatus for semiconductors, but can also be applied to exposure of crystal resonators, acoustic wave elements, etc., for example.

[Brief explanation of the drawing]

FIG. 1 is a detailed explanatory diagram of the present invention, FIG. 2 is an explanatory diagram of the definition of the optical system NA, and FIGS. 3 and 4 are explanatory diagrams of exposing the wafer surface.

Claims (1)

[Claims] a light source, a condensing reflector in which the light source is placed at a first focal position, an off-axis optical system for creating a spot-like parallel light placed in a position to receive light from the condensing reflector, and this spot. A rotating regular polyhedral mirror that receives parallel light and reflects it repeatedly in a fan shape within a predetermined angular range, and a plurality of spherical mirrors that reflect and expand the light beam that is repeatedly reflected in the fan shape in an arc shape onto a photomask. By projecting the arc-shaped reflected light onto the irradiated object through the photomask and simultaneously moving the photomask and the irradiated object, the photomask pattern is spread over a pre-specified area. An exposure apparatus characterized by projecting images using a one-to-one scanning method.