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Browse Prior Art Database

Determining Vapor Density & Detecting Contaminants in Evaporation Processes

IP.com Disclosure Number: IPCOM000076536D
Original Publication Date: 1972-Mar-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 37K

Publishing Venue

IBM

Related People

Hoekstra, JP: AUTHOR [+2]

Abstract

In processes where metals are evaporated on to a substrate, a necessary problem to be overcome is evaporation shadowing. Heretofore, to prevent such effect, a metal thickness monitor has been disposed such that it is offset from the metal source to the substrate axis. However, in such arrangement, the metal deposited on the substrate, as indicated by the monitor can only be accurately measured when no changes occur in the spatial distribution of the vapor stream during the evaporation. However, because the cross-sectional density distribution of the metal vapor stream is in as continuous state of flux because of source configuration, the presence of slag, the depletion of melt and other factors, the monitor cannot be employed to directly determine the thickness of the metals deposited on the substrate.

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Determining Vapor Density & Detecting Contaminants in Evaporation Processes

In processes where metals are evaporated on to a substrate, a necessary problem to be overcome is evaporation shadowing. Heretofore, to prevent such effect, a metal thickness monitor has been disposed such that it is offset from the metal source to the substrate axis. However, in such arrangement, the metal deposited on the substrate, as indicated by the monitor can only be accurately measured when no changes occur in the spatial distribution of the vapor stream during the evaporation. However, because the cross-sectional density distribution of the metal vapor stream is in as continuous state of flux because of source configuration, the presence of slag, the depletion of melt and other factors, the monitor cannot be employed to directly determine the thickness of the metals deposited on the substrate.

For deposition control, a crystal thickness technique is most commonly employed because of its simplicity and relative accuracy. However, this technique presents a disadvantage, in that the crystal has a limited lifetime and its capability of only measuring the vapor for which it has been calibrated.

Described is an evaporation vapor monitoring technique which measures the density of metal vapor that is deposited on a substrate. With the technique, there is also analyzed the vapor composition during deposition. Such analysis is most important when there are deposited mixtures such as aluminum-copper, and the like.

The principle of this technique is the transmitting of a beam of small ionic projectiles through the metal evaporation stream into a collector. By measuring the charge on the collector, the evaporation stream density can be directly determined since the cross-section for scattering beyond a given solid angle is directly proportional to the vapor density of the stream. By having a projectile detector disposed at an angle, the scattered projectiles can be analyzed as to energy. The kinematics resulting f...