JPS61232615A - Exposure device - Google Patents

Abstract

PURPOSE:To improve efficiently the curvature of field of a projective optical system and the halo caused by higher spherical aberration outside an axis and to enlarge the dimensions of an image plane substantially by a system wherein the surface of a reticle is scanned and illuminated partially through a slit-shaped opening, and the reticle or a wafer is moved in the direction of the optical axis of the projective optical system in synchronization with the scan. CONSTITUTION:A flux of light from a light source 2, such as a mercury-vapor lamp and a laser, which is disposed in the vicinity of the first focal point of an elliptical mirror 1 is converged by the elliptical mirror 1 and guided to a first illumination system 3, and illuminates, with a prescribed angular distribution, an opening 4 for scanning which operates as a basic unit of exposure. The flux of light passing through the opening 4 is reflected by an oscillating mirror 5 for scanning and then by a reflector 6, and thereafter it is made to illuminate the surface of a reticle 8, a first object, by a second illumination system 7. The opening 4 for scanning is imaged virtually on the surface of the reticle 8 by the second illumination system 7 for the purpose of uniform illumination. The flux of light reflected by the oscillating mirror 5 and passing through the opening 4 scans and illuminates the surface of the reticle 8 in accordance with the oscillation of the oscillating mirror 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an exposure apparatus, particularly 10. The present invention relates to an exposure apparatus suitable for projecting and exposing a pattern on a mask or reticle surface onto a surface of a wafer using a projection optical system in the production of integrated circuits such as LSIs.

(Prior Art) Conventionally, in the production of integrated circuits, two methods have been broadly classified as methods for transferring and exposing a pattern on a reticle surface onto a wafer surface.

One is called a step-and-repeat method, in which the wafer surface is divided into a plurality of parts, and the pattern on the reticle surface is sequentially projected and exposed onto the divided wafer surface. This method exposes the entire wafer by repeating the process of moving the wafer a predetermined position after one shot exposure and performing projection exposure again. This method combines dynamic drive.

The other method is called a scan method proposed in Japanese Patent Application Laid-Open No. 52-5544. This method uses a specific area (
It becomes ring-shaped. ), the mask and wafer corresponding to the object plane and the imaging plane are simultaneously scanned and one projection exposure is performed.

Attention has been paid. In this method, the area that can be exposed in one exposure, that is, the screen size, depends on the performance of the projection optical system. In general, the higher the resolution of the imaging performance of the projection optical system, the smaller the screen size becomes. That is,
There is a rule of thumb for projection optical systems. In other words, this corresponds to the fact that if the projection optical system is used as one information transmission means, the amount of information that can be transmitted is constant. Now that integrated circuit patterns are becoming more dense, it has become important to increase the amount of information transmitted by projection optical systems and to build systems that can support future devices.

Currently, in the production of high-density integrated circuits, one of the most important factors in optical design that limits the screen size is field curvature, which is one of the various aberrations of the projection optical system. Generally speaking, if you try to reduce this field curvature, flatten the image surface, and enlarge the screen size, high-order off-axis spherical aberration called a halo will increase, and this halo will reduce the projection resolution. This is the cause of For this reason, it is very difficult to increase the screen size of the projection optical system.

(Objective of the Present Invention) An object of the present invention is to provide an exposure apparatus that obtains high resolution over the entire screen by adopting a new exposure method and substantially enlarges the screen size of the projection optical system.

(Main feature of the present invention) When projecting and transferring a planar first object onto a planar second object surface via a projection optical system, the first object surface is illuminated while being scanned with a slit-shaped light beam and is scanned. synchronized with the first
One of the object and the second object is moved in the optical axis direction of the projection optical system according to the imaging performance of the projection optical system.

Other features of the invention are described in the Examples.

(Example) FIG. 1 is a schematic diagram of one embodiment of the invention.

In the figure, 1 is a male circular mirror, 2 is a light source such as a mercury lamp located near the first focal point of the circular mirror 1, and the light beam from the light source 2 is focused by the circular mirror 1. The light is guided to the first illumination system 6, and illuminates the scanning aperture 4, which is the basic unit of exposure according to this embodiment, with a predetermined angular distribution. The light flux passing through the aperture 4 is reflected by a scanning mirror 5, and once reflected by a reflection mirror 6, a second illumination system 7 illuminates the surface of a reticle 8, which is a first object.

The scanning aperture 4 is illuminated uniformly by a second illumination system 7.
The image is formed approximately on the 8th surface of the reticle.

The light beam reflected by the vibrating mirror 5 and passing through the aperture 4 illuminates the surface of the reticle 8 while scanning it in accordance with the vibration of the vibrating mirror 5.゛Figure 2 is an explanatory diagram of an embodiment showing the state of scanning illumination at this time. In the figure, reference numeral 41 denotes an aperture image formed on the surface of the reticle 8 by the second illumination system 7 of the aperture 4. The aperture image 41 has a linear slit shape, and the length of the slit is long enough to cover the screen size to be exposed.

By scanning this slit-shaped aperture image 41 in the direction of the arrow, the entire screen of the reticle 8 is exposed.

Referring again to FIG. 1, a projection optical system 9 projects the pattern on the reticle 8 onto the wafer surface.

In this embodiment, the projection magnification of the projection optical system is reduced or equal magnification. 10 is a wafer and stage 11
is placed on top. The stage 11 can be driven in each direction by drive devices 12, 13, and 14 in the x, y, and z directions, and in the θ direction by a drive means (not shown). 1
5 is a driving bag ft' in two directions synchronized with the vibration of the vibrating mirror 5.
This is a drive control device for driving 14.

The feature of this embodiment is that the entire surface of the reticle 8 is not exposed at once, but is exposed by scanning illumination using the aperture image 41.

Furthermore, in this embodiment, in one exposure, the stage 11 is moved in two axial directions, that is, in the optical axis direction of the projection optical system 9, by the drive device 14 in correspondence with the scanning position of the aperture image 41 on the reticle 8 surface. It is being driven.

At this time, the driving amounts in the two-axis directions are controlled in synchronization with the vibrating mirror 5 by the drive control device 15 so as to match the field curvature characteristics of the projection optical system 9 determined in advance. The amount of driving at this time is set to the average image plane position 1a within the scanning slit.

For example, the curve P shown in FIG.
1, and as shown in FIG. 4, it is assumed that an aperture image 42 of the wafer 10 is projected at a position a distance a1 from the optical axis S. At this time, the distance a1* from the optical axis S
The curvature of the image plane at a position separated from the optical axis S by a distance a2 is defined as bl, and the curvature of the image 1aI at a position a distance a2 from the optical axis S is defined as b2. Then, the image surface characteristic within the aperture image 42 is the curve P2 shown in FIG.
It will be like this.

At this time, in this embodiment, exposure is performed after the stage 11 is driven to the side of the projection optical system 9 by a distance i (b I +b 2) /as compared to the Gaussian image plane G on the optical axis S.

In this embodiment, by adopting such an exposure method, even in a region that cannot be used conventionally due to optical performance, that is, a region at a distance Ma2 from the optical axis S, it is possible to achieve high resolution that is almost the same as that on the optical axis. A pattern image is obtained. As a result, a projection optical system with substantially enlarged screen size is achieved.

In this embodiment, instead of driving the stage 11 for mounting the wafer 10 in synchronization with scanning, the reticle 8 may be driven in the optical axis S direction in synchronization with scanning.

Further, in this embodiment, scanning may be performed continuously or discontinuously.

(Effects of the present invention) By partially illuminating the reticle surface with a slit-shaped aperture and moving the reticle or wafer in the optical axis direction of the projection optical system in synchronization with the scanning,
Efficiently improve field curvature of the projection optical system and halo caused by off-axis high-order spherical aberration, overcome optical design constraints,
An exposure apparatus with substantially enlarged screen size can be achieved. Furthermore, it becomes possible to construct an exposure apparatus suitable for manufacturing integrated circuits that will become increasingly dense in the future.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of a scanning method according to the present invention, and FIGS. 6 and 4. FIG. 5 is an explanatory diagram of the field curvature of the projection optical system according to the present invention. In the figure, 1 is a circular mirror, 2 is a light source, 6 is a first illumination system, 4 is a scanning aperture, 5 is a vibrating mirror, 7 is a second illumination system, 8 is a reticle, 9 is a projection optical system, 10 is the wafer, 11 is the stage,
12, 13, and 14 are drive devices, and 15 is a drive control device.

Claims (2)

[Claims] (1) When projecting and transferring a planar first object onto a planar second object surface via a projection optical system, the first object surface is illuminated while scanning with a slit-shaped light beam, and at the same time An exposure apparatus characterized in that one of the first object and the second object is moved in the optical axis direction of the projection optical system in accordance with the imaging performance of the projection optical system. (2) The amount of movement of the first object or the second object is determined from the average value of the amount of field curvature within the scanning slit within the screen of the projection optical system. exposure equipment.