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Multiple Crystal Technique for Evaporated Metal Thickness Control

IP.com Disclosure Number: IPCOM000043068D
Original Publication Date: 1984-Jul-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Logan, JS: AUTHOR [+4]

Abstract

A major cause of metal film thickness variation is the shifting of the evaporant cloud in the chamber during E-beam evaporation. This shifting can be detected and controlled by using two frequency shift crystals, located 180Πapart on the periphery of the deposition area. These crystals would be monitored by separate microprocessors, either one of which could be used to control the deposition rate. With this arrangement, control of the evaporant cloud can be achieved by a two-step operation. First, the beam position is adjusted longitudinally to equalize the deposition rate on both crystals, insuring that the center of the cloud is equidistant from these two points. Second, the beam position is adjusted latitudinally to minimize the power necessary to give the desired deposition rate.

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Multiple Crystal Technique for Evaporated Metal Thickness Control

A major cause of metal film thickness variation is the shifting of the evaporant cloud in the chamber during E-beam evaporation. This shifting can be detected and controlled by using two frequency shift crystals, located 180OE apart on the periphery of the deposition area. These crystals would be monitored by separate microprocessors, either one of which could be used to control the deposition rate. With this arrangement, control of the evaporant cloud can be achieved by a two- step operation. First, the beam position is adjusted longitudinally to equalize the deposition rate on both crystals, insuring that the center of the cloud is equidistant from these two points. Second, the beam position is adjusted latitudinally to minimize the power necessary to give the desired deposition rate. With the cloud now located in the center of the system, the thickness variation will be smaller within a run and from run to run. A distribution shield can also be added to give a more uniform distribution across the dome. A centrally located third crystal can be used to sense and control total beam current for the desired deposition rate, as is usually done.

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