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Dose Stabilization Technique in E-Beam Lithography

IP.com Disclosure Number: IPCOM000047929D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Vettiger, P: AUTHOR [+2]

Abstract

The proposed technique provides for precise regulation of the incident electron dose striking on a sample in an E-beam system. Sample and)or backscattered currents are measured and used to control the beam-stepping rate without changing the electron source. Dose control is either instantaneous or "averaged". The figure shows a schematic diagram of an E-beam system employing the proposed control technique. The primary electron beam strikes the sample which is placed on a sample holder 1 connected to a sample current amplifier 3. A backscattered electron (BSE) detector 2 is connected to a second amplifier 4. The outputs of these amplifiers are transferred to circuitry 5 providing for a variety of functions, such as filtering, adding and averaging, to be selectively performed on the input signals.

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Dose Stabilization Technique in E-Beam Lithography

The proposed technique provides for precise regulation of the incident electron dose striking on a sample in an E-beam system. Sample and)or backscattered currents are measured and used to control the beam-stepping rate without changing the electron source. Dose control is either instantaneous or "averaged". The figure shows a schematic diagram of an E-beam system employing the proposed control technique. The primary electron beam strikes the sample which is placed on a sample holder 1 connected to a sample current amplifier 3. A backscattered electron (BSE) detector 2 is connected to a second amplifier 4. The outputs of these amplifiers are transferred to circuitry 5 providing for a variety of functions, such as filtering, adding and averaging, to be selectively performed on the input signals. Comparator 6 compares the actual dose signal from circuitry 5 and a preset reference signal. The error signal at the output of comparator 6 is applied to dwell-time correction circuit 7 which could be a digital delay line generator or voltage-controlled oscillator. Its output is used to control the beam-step clock. Different modes of operation are possible. In one mode, the beam dwell time for the next exposure period is determined by averaging the sample current for a selected period to "average out" variations in the sample current due to backscattered and secondary electron emissions from the sample caused by topographi...