JPH02137216A - Method of projection exposure - Google Patents

Abstract

PURPOSE:To enlarge a focal depth while requiring only one exposure by changing position of a wafer along the optic axis during the exposure. CONSTITUTION:Optical pattern formed on a mask 14 is projected and exposed through a lens 16 onto a resist layer 12 on a semiconductor wafer 10. During said projection and exposure, the wafer 10 is first placed at a position Z1 on the optic axis and then placed at a position Z2 somewhat higher than Z1. In this instance, the wafer 10 is shifted continuously from the position Z1 to the position Z2 somewhat higher than Z1. The wafer 10 also may be shifted from Z1 to Z2 by multiple stages or reciprocally (in a vibrational manner). Focal depth can be enlarged thereby and hence production yield can be improved. Further., since only one exposure is required, throughput also can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a projection exposure method used for manufacturing semiconductor devices and the like.

[Summary of the Invention] The present invention aims to expand the depth of focus by changing the position of the wafer along the optical axis during projection exposure of an optical pattern formed on a mask onto a resist layer on a wafer. It is something that

[Prior Art] Conventionally, in the manufacture of LSIs and the like, reduction projection exposure equipment, full-magnification projection exposure equipment, etc. have been used to transfer contact hole patterns, wiring patterns, etc. to a resist layer on a semiconductor wafer. ing.

In this type of projection exposure apparatus, resolution is improved by increasing the aperture diameter of the projection optical system and shortening the projection wavelength to enable processing of fine patterns. However, when the resolution is improved in this manner, the depth of focus becomes narrower, and even if the Ueno plane is slightly shifted from the focal plane in the optical axis direction, there is a problem in that the transfer accuracy is significantly reduced.

In order to solve these problems, a multiple imaging exposure method has been proposed in which exposure is performed in multiple steps, as shown in FIGS. 4 and 5.

In the process shown in FIG. 4, the resist layer 1 on the semiconductor wafer 10 is
2, the optical pattern formed on the mask 14 is projected and exposed through the lens 16. At this time, the position of the wafer lO along the optical axis is assumed to be 21. Next, in the step shown in FIG. 5, projection exposure processing is performed in the same manner as before with the position of the wafer 10 set at Z2, which is slightly higher than 21. in this case,
The temporal relationship between the wafer position and the shirt opening/closing operation is shown in FIG. That is, when the wafer position is 21, the shutter is opened to perform the first exposure, and then the shutter is closed. Then, with the wafer position set at 22, the shutter is opened again to perform a second exposure, and then the shutter is closed.

[Problems to be Solved by the Invention] According to the above-described multiple imaging exposure method, exposure processing is required multiple times, and the process is inevitably complicated.

An object of the present invention is to enable expansion of the depth of focus with one exposure process.

[Means for Solving the Problems] The projection exposure method of the present invention is characterized in that the wafer position is changed along the optical axis during exposure. In this case, the wafer position can be changed continuously, in multiple steps, reciprocally, or the like.

[Function] According to the method of the present invention, since the wafer position is changed along the optical axis during exposure, the depth of focus is expanded and only one exposure process is required.

[Embodiment] The present invention is implemented, for example, in a reduction projection exposure apparatus. In this type of device, the semiconductor wafer is held on a moving stage and its position is controlled three-dimensionally in the X direction (horizontal direction), Y direction (front and back direction), and X direction (vertical direction, i.e., optical axis direction). It looks like this. When implementing this invention, the wafer position in the X direction is controlled by a piezoelectric element, a voice coil, a motor, etc., and the position in the X direction is detected by a laser interferometer, an oblique incidence optical system, an optical sensor, a capacitance sensor, an air Highly accurate position control is possible by using a method such as a microsensor.

1 to 3 are the first to third views of this invention, respectively.
The changes in the wafer position in the X direction according to the embodiments shown in FIG.

In the first embodiment (FIG. 1), the wafer position is continuously changed from Zll to Z12, which is slightly higher, while the shutter is open (during exposure). Further, in the second embodiment (FIG. 2), the wafer position is changed in multiple steps from 221 to Z22, which is slightly higher than 221, while the shutter is open. In the first or second embodiment, the wafer position may be changed from a high position (Z12 or Z22) to a low position (Z-th position or Z21).

In the third embodiment (FIG. 3), the wafer position is reciprocated (vibrated) between 231 and Z32, which is slightly higher, while the shutter is open.

[Effects of the Invention] As described above, according to the present invention, since the depth of focus can be expanded, the manufacturing yield can be improved. Furthermore, since the exposure process only needs to be performed once, an effect of improving throughput can also be obtained.

[Brief explanation of the drawing]

1 to 3 are the first to third views of this invention, respectively.
These are time charts showing changes in wafer position as the shutter opens and closes, and Figs. 4 and 5 show sequential exposure steps in the conventional multiple imaging exposure method. FIG. 6 is a time chart showing the relationship between the conventional wafer position and the opening/closing operation of the shirt shutter. IO...Semiconductor wafer, 12...Resist layer-14...Mask, 16...Lens.

Claims (1)

[Claims] 1. In a projection exposure method in which an optical pattern formed on a mask is projected onto a resist layer formed on the surface of a wafer, the position of the wafer is changed along the optical axis during exposure. A projection exposure method characterized by 2. The projection exposure method according to claim 1, wherein the change in the position of the wafer is a continuous change. 3. The projection exposure method according to claim 1, wherein the change in the position of the wafer is performed in multiple steps. 4. The projection exposure method according to claim 1, wherein the change in the position of the wafer is a reciprocating change.