Browse Prior Art Database

Electron Beam Registration Channel With Auto-Zeroing Circuit

IP.com Disclosure Number: IPCOM000041300D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Davis, DE: AUTHOR [+2]

Abstract

In an electron beam lithography tool registration system, the detection signal, produced by scanning the beam across registration marks, is typically DC coupled to an automatic gain control circuit and sent to an A/D converter and a digital feedback loop. As a result of the low level of the registration signals and the high gain of the registration circuit chain, the DC offset at the A/D converter may be excessive. Disclosed herein is a circuit for zeroing this offset voltage once each registration mark cycle, thus providing an acceptable offset at the A/D converter input. Referring to Fig. 1, an electron beam registration system includes detectors 1, the detection signals from which are DC coupled to differentiators 2 and summer 3 via preamplifiers 4.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 70% of the total text.

Page 1 of 2

Electron Beam Registration Channel With Auto-Zeroing Circuit

In an electron beam lithography tool registration system, the detection signal, produced by scanning the beam across registration marks, is typically DC coupled to an automatic gain control circuit and sent to an A/D converter and a digital feedback loop. As a result of the low level of the registration signals and the high gain of the registration circuit chain, the DC offset at the A/D converter may be excessive. Disclosed herein is a circuit for zeroing this offset voltage once each registration mark cycle, thus providing an acceptable offset at the A/D converter input. Referring to Fig. 1, an electron beam registration system includes detectors 1, the detection signals from which are DC coupled to differentiators 2 and summer 3 via preamplifiers 4. The summer output is DC coupled to an automatic gain control circuit 5 via filter 6. The automatic gain control output is sent to an A/D converter via buffer amplifier 7. Auto zeroing circuit 8, in conjunction with timing circuit 9, zeros the DC offset voltage at the A/D converter input over a wide range of input signal amplitudes. Operation of auto-zeroing circuit 8 is as follows: During the first scan across the electron beam registration marks (Fig. 2), the registration signal is sampled by the automatic gain control circuit 5 and the gain is set so that a constant signal is applied to the A/D converter. During the second scan (Fig. 2), control pulses...