Browse Prior Art Database

Error Compensating Electron Beam Microfabrication

IP.com Disclosure Number: IPCOM000078866D
Original Publication Date: 1973-Mar-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 4 page(s) / 58K

Publishing Venue

IBM

Related People

Hatzakis, M: AUTHOR [+3]

Abstract

This description relates to a system wherein registration time and errors in writing patterns for microfabrication, are reduced for a given speed of exposing such wafers in electron-beam systems.

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Error Compensating Electron Beam Microfabrication

This description relates to a system wherein registration time and errors in writing patterns for microfabrication, are reduced for a given speed of exposing such wafers in electron-beam systems.

A major concern in designing systems for electron-beam exposure of electron resists for microfabrication, is that of increasing the speed with which a wafer is exposed to yield a given pattern in the exposed resist.

There are seven relevant areas in which improvements are desired, the first involves the electron source brightness which determines the amount of current delivered into an electron spot of a certain size; the second relates to the sensitivity of a resist which determines how much charge density is necessary to make the resist developable; the third relates to vector scanning of an electron beam to reduce the time wasted in areas where no electron dosage is to be applied; the fourth, fifth, sixth and seventh are multiple spot systems; projection systems; registration speed on step and repeat; and field size of each step and repeat area.

Items six and seven are coupled because registration onto a new field is time-consuming. To reduce the total registration time, (as well as to increase pattern complexity), it is desirable to increase the area exposed on each step and repeat operation. This then begs improvements in the number of lines of resolution in a field. As accommodations to this, the problems of deflection aberration, must be solved by deflection coil design, dynamic astigmatism control and dynamic focus control. Conversely, if registration were no problem, the pressure on field size is somewhat reduced. The following description sets forth a way to reduce the problem of registration.

The proposed system approach as shown in the drawing, includes essentially two identical lenses and identical deflection coils which are coaxially aligned. The electron beams in each subsystem are to be optimized for their respective functions.

The figure schematically shows the embodiment in which two beams, designated the wafer beam and the mask beam, are oppositely directed against opposite sides of a moveable holder for the working wafer and mask master. The wafer beam or writing beam has as large a current as feasible consistent with the required spot size. The mask master beam has a current and spot size to yield a high-quality blanking signal for the writing beam.

The requirement on the mask master is that it is a one-to-one replica of the desired pattern, with allowance in pattern line width to compensate for line width growth on an exposed wafer. Most desirable is a mirror image relationship between the mask pattern and the wafer pattern, to keep the two beams again as mirror images of one another. A second choice is to demand inversion symmetry about a point on the optic axis and midway between the mask master and wafer surfaces. This latter symmetry appears more capable of cancel...