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Detection Preamplifiers for E Beam Calibration and Registration

IP.com Disclosure Number: IPCOM000082136D
Original Publication Date: 1974-Oct-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Davis, DE: AUTHOR [+3]

Abstract

This circuit amplifies both registration and calibration signals in such a way, as to optimize the signal-to-noise ratios for each signal.

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Detection Preamplifiers for E Beam Calibration and Registration

This circuit amplifies both registration and calibration signals in such a way, as to optimize the signal-to-noise ratios for each signal.

An electron beam-impinges on target area 10, producing backscattered electrons which are detected by diodes 12, 14, 16 and 18. The calibration signal is produced from a calibration grid and results in a signal having an amplitude of approximately 300 microamps, requiring a 5 mhz bandwidth for sensing without distortion. On the other hand, a registration signal is typically 5 mricroamps in amplitude and requires a 250 khz bandwidth for sensing without distortion.

By using a switch 20 to control both the gain and bandwidth of the preamplifiers 22, an optimum signal-to-noise ratio is obtained for both signals. The resultant signal is summed in summing amplifier 24 for calibration. For registration, different amplifiers 26 provide the registration signal. Both signals are derived from the backscattered electrons from the beam target area 10.

The diodes 12, 14, 16 and 18 are fully depleted, with a guard ring and are turned with the junction side of the diode away from the beam for protection. The diodes are biased such that the side of the diode turned toward the beam is at ground potential, in order to not deflect the beam.

The shape and angle of the diodes with respect to the semiconductor wafer surface are optimized, to maximize signal strength and signal-to noise r...