Patent for License

Multiphase printing for E-beam lithography

A method for a raster scan particle or light beam lithography system for writing in multiple passes interleaved in such a manner as to achieve a composite result nearly identical to normal single pass

Overview

A method for a raster scan particle or light beam lithography system for writing in multiple passes interleaved in such a manner as to achieve a composite result nearly identical to normal single pass raster scan writing with overlapped spots. Multiple pass writing, achieved with little or no degradation or throughput or lithography quality, provides an ideal platform for implementation of known image averaging techniques to improve lithography quality. This technique is combined with the known writing technique of "Virtual Addressing" to improve resolution with little or no degradation of throughput.

SUMMARY OF THE TECHNOLOGY

The writing technique in accordance with this invention is performed in a raster scanning particle beam lithography system having, inter alia, a particle beam source, a means of beam blanking, a means of deflecting said beam in scan lines, and a means of focusing said beam onto a resist-coated substrate positioned on a moveable stage. The final pixelization of the lithographic pattern on the substrate consists of pixels whose centers are placed on a cartesian writing grid as if with a normal raster scan writing technique. Multiphase printing achieves this pixelization by interleaving pixels in a series of passes, over a coarser (larger writing address dimension) grid. Each pass is offset from others by a fraction of the writing address required to achieve the composite cartesian pixel array. Each pass is called a phase.

Since the throughput of a raster scan system increases as the square of the writing grid, multiple passes are achieved with little or no loss of throughput. Since pixels are interlaced on a cartesian grid, all feature edges are logically the same. Spot size may be adjusted to that pixels overlap by a substantial fraction of the pixel size. The result is virtually identical to single pass overlapping of larger spots which the prior art teaches may be used to achieve good lithography quality. Since this present technique is accomplished in multiple passes, it allows the implementation of redundant imaging schemes without the throughput sacrifice required with a normal raster writing technique. Additionally, it provides an improved platform for the implementation of the virtual addressing technique.

Interleaving of pixels in separate passes over separate sets of pixels on a cartesian grid is performed in accordance with the technology. Using this interleaving as a platform for virtual addressing is a second aspect of the technology which is an improvement over the other virtual addressing method.

The technology is applicable to raster scanning systems generally, not just those using E-beams; for instance, a laser beam or other light beam could be used. The exposed material could include materials other than photo-resist, such as photographic film, that is subject to accumulated changes from multiple exposures.