US 4,924,257 A · Scan and repeat high resolution projection lithography system

Abstract

This scan and repeat lithography system has high resolution capability, large effective image field size, and high substrate exposure speed, and comprises: (a) a substrate stage capable of scanning a substrate in one dimension and, when not scanning in said dimension, capable of moving laterally in a direction perpendicular to the scan direction so as to position the substrate for another scan; the substrate stage exposing the full substrate by breaking up the substrate area into parallel strips, and exposing each of the strips by scanning the length of the strip across a fixed illumination region; (b) a mask stage capable of scanning in the same direction as, and synchronized with, the substrate stage, at a speed faster than the substrate stage scanning speed by a certain ratio M; (c) an illumination subsystem having an effective source plane in the shape of a polygon, and capable of uniformly illuminating a polygon-shaped region on the mask; (d) a projection subsystem having an object-to-image reduction ratio M, and having a polygon-shaped image field of an area smaller than the desired effective image field size of the lithography system; and (e) provision of complementary exposures in an overlap region between the areas exposed by adjacent scans in such a way that a seam in the exposure dose distribution received on the substrate is absent between the scans, and such that the exposure dose delivered across the entire substance is uniform.

Claims22

Dependent claims

A high resolution, high exposure speed, large effective field size scan and repeat lithography system for producing precise images of a pattern that is present on a mask onto a substrate, comprising:

(a) a substrate stage capable of scanning a substrate in one dimension and, when not scanning in that dimension, capable of moving laterally in a direction perpendicular to the scan direction so as to position the substrate for another scan;
said substrate stage thus being capable of exposing the full substrate by breaking up the substrate are into a certain number of parallel strips, and exposing each of said strips by scanning the length of the strip across a fixed illumination region;
(b) a mask stage capable of scanning in the same dimension as, and synchronized with, the substrate stage, at a speed equal to the substrate stage scanning speed multiplied by a certain ratio M;
(c) an illumination subsystem having the desired characteristics of wavelength and intensity distribution, having an effective source plane in the shape of a polygon, and capable of uniformly illuminating a polygon-shaped region on the mask;
(d) a projection subsystem for imaging the said polygon-shaped illuminated region on the mask onto the substrate, having an object-to-image reduction ratio M, having the desired image resolution, and having an image field in the shape of a polygon and of an area smaller than the desired effective image field size of the said lithography system;
and
(e) control means to operatively interrelate said substrate stage, said mask stage and said illumination subsystem, and to provide complementary exposures in an overlap region between the areas exposed by adjacent scans in such a way that the exposure dose distribution received in the overlap region is seamless, and such that the exposure dose delivered across the entire substrate is uniform.

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The method for providing a scan and repeat lithography system for high-resolution, large-field, high-speed lithography, characterized by the following steps:

(a) Providing a substrate stage for holding the substrate, and capable of scanning the substrate in one dimension, and capable of moving laterally in a direction perpendicular to the scan direction;
(b) Providing a mask stage for holding the mask, and capable of scanning the mask in the same dimension as the substrate stage;
(c) Providing an illumination subsystem having the desired characteristics of wavelength and intensity distribution, having aan effective source plane in the shape of a polygon, and capable of uniformly illuminating a polygon-shaped region on the mask;
(d) Providing a projection subsystem for imaging the said polygon-shaped illuminated region on the mask on to the substrate, having an object-to-image reduction ratio M, having the desired image resolution, and having an image field in the shape of a polygon and of an area smaller than the desired effective image field size of the said lithography system;
(e) Providing a mask which has a certain number of complete, patterned chip fields, and additional patterned areas that fall within the hexagonal illuminated region on the mask;
(f) Scanning the substrate across the polygonal substrate illumination region at a certain velocity v.sub.x, and simultaneously scanning the mask in a parallel direction across the polygonal mask illumination region at a velocity Mv.sub.x ;
(g) Stopping the scanning of the substrate and mask stages upon completion of a scan across the total length of the substrate along the direction of scan, moving the substrate by a certain distance in a direction perpendicular to the scan direction, and resuming the scanning of the substrate and the mask stages in directions opposite to their respective directions in step (f);
(h) Providing complementary exposures in an overlap region between the areas exposed by adjacent scans in such a way that a seam in the exposure dose distribution received on the substrate is absent between the said scans, and such that the exposure dose delivered across the entire substrate is uniform;
(i) Repeating steps (f)-(h) until exposure of the entire substrate is completed.

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