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Electron Beam Registration

IP.com Disclosure Number: IPCOM000090269D
Original Publication Date: 1969-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Speth, AJ: AUTHOR

Abstract

Use of an electron beam to expose resists for device fabrication often requires multiple pattern exposures which must be spatially registered. Some methods use a registration mark within each field of view to modulate the secondary emission during a raster scan over the field. Generally, the beam is moved to the center of this mark before active exposure takes place.

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Electron Beam Registration

Use of an electron beam to expose resists for device fabrication often requires multiple pattern exposures which must be spatially registered. Some methods use a registration mark within each field of view to modulate the secondary emission during a raster scan over the field. Generally, the beam is moved to the center of this mark before active exposure takes place.

Previously, the same beam is used for referencing and exposing. The low exposure currents enhance the problems, for example, the available secondary electron signal from the mark is reduced due to the masking or attenuating effect of the resist overcoat. Also, slightly different resist thicknesses are likely to be used in successive operations and the intervening chemical operations can affect both the physical profile and chemical constitution of the mark. These tend to change the secondary electron intensity distribution at successive operations on the same wafer. Furthermore, the resist coating is normally insulating and the secondary electron profile can be affected by either charging surface contamination or material changes during continued exposure, in effect causing a time-varying though spatially-referenced signal.

This method uses the backside of the wafer to provide the referencing signal. A separate electron beam whose parameters, aside from voltage, can differ from the exposing beam is used. Substantially larger currents and somewhat larger spot sizes can be us...