Device manufacture involving lithographic processing

Abstract

Fabrication of devices of micron and submicron minimum feature size is accomplished by lithographic processing involving a back focal plane filter. A particularly important fabrication approach depends upon mask patterns which produce images based on discrimination as between scattered and unscattered radiation by accelerated electrons.

Description

BACKGROUND OF THE INVENTION1. Technical FieldThe invention is concerned with the fabrication of devices by procedures including lithographic delineation. Contemplated devices may be discrete or integrated but have the common characteristic of being dependent upon feature size or spacing which may be as small as a micrometer or less. Semiconductor integrated circuits are critically dependent on small dimensions, and future generations are expected to benefit by the invention. Prospectively, integrated circuits will increasingly include optical devices, and these too will be advanced by the inventive teaching.2. TerminologyThe arts involved, commercial as well as scientific, make use of a variety of terms which are not consistently applied. It is convenient to define terms as used in this document. Following definitions are in terms of electron lithography-the area of prime importance as well as that of greatest need of definition. Terms as applied to x-ray or other electromagnetic ra...

AI Technical Summary

Benefits of technology

Appropriate lithographically defining energy must be of such nature as to be scattered or transmitted in the above terms by "blocking" and "transparent" regions of masks which are expediently manufactured and used (e.g. in terms of structural material and thickness). A variety of energy forms are suitable from this standpoint. Inventive significance is primarily in terms of energy of properties inherently suited to micron and submicron feature size definition. A preferred system relies upon electrons sufficiently accelerated for appropriate fine feature resolution. Specific discussion is in terms of acceleration within the 50-200 kV range. Maximum acceleration is likely to be limited by device-consequential material damage. In general, still greater acceleration results in improvement e.g. in terms of depth of focus and penetration depth and may be indicated depending upon device design demands. The inventive fabrication systems may result in product advantages as used with electromagnetic radiation energy e.g. in the x-ray spectrum as well. While the electron beam projection approach as generally contemplated by the invention entails initial illumination of the mask by already-accelerated electrons, the invention is of other value. For example, photo illumination of a photo cathode to result in mask illumination by unaccelerated electrons may benefit by the inventive teaching. This version of the invention involves acceleration of the already mask-patterned radiation. Resulting accelerated electrons as permitted by the back focal plane filter have the described advantages with respect to depth of focus and penetration depth. In addition, the back focal plane filter may increase edge acuity by differentiation based on scatter angle.

Most significant near-term use of the invention involves patterning of resist materials. In general, delineating energy chosen for high resolution or low damage has little direct effect on device-functional properties of usual materials being processed. This is particularly true of an important category of processes which depend on electrons accelerated within the 50-200 kV range or higher. Such energized electrons are not locally absorbed within thin surface regions but penetrate to significant depths, sometimes completely through the article being fabricated. It is a feature of the invention that the very small concentration of damage-induced defects minimizes deterioration of device-significant characteristics.

Suitable to contemplated submicron minimum features, the inventive approach may expedite in-situ processing. For example, electron imaging in accordance with a preferred form of the invention is desirably carried out in an evacuated atmosphere. This is consistent with other procedures which might precede or follow imaging. Examples are deposition procedures such as Molecular Beam Epitaxy and Chemical Vapor Deposition. Such compatibility favors device fabrication without need for changing apparatus or breaking vacuum, and so lessens contamination.

Problems solved by technology

Maximum acceleration is likely to be limited by device-consequential material damage.

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