No abstract

Ion implantation in semiconductor devices frequently leads to a substantial wafer surface charge build up. Control of this charge during high current implantation is a major process issue, as it may affect the yield and reliability of thin dielectric layers. In addition, the charge build up may affect the ion beam resulting in a non-uniform implant and a reduction in device yield. Control of a specific machine parameter, that will give the charge condition of the ion implanter will enable to neutralize the charge build up.In this study, Disk Current Monitoring (DCM) is shown to be a reliable method for monitoring the Electron Shower (ES) performance in real time. A correlation was found between DCM level and yields, and between DCM level and breakdown voltage, as well as different maintenance activities regarding me ES. A simple 5 steps method is described to achieve a reliable, real time charge monitor, to insure operation within the “High Yield Range”.

Interfacial reactions for the Co/Ge and Ge/Co contact systems on (001)-oriented n-type GaAs substrates were studied with emphasis on Ge-rich stoichiometries−Co:Ge=1:1 and 2:3. Following annealing at temperatures up to 350 °C, intermetallic compounds of cobalt and germanium were formed, depending on the Co:Ge atomic ratio, while the inner interface with the GaAs substrate remained intact. At higher temperatures (up to 600 °C, the highest temperature used) a limited reaction with the GaAs substrate was detected. This reaction for both configurations was contained near the interface with the substrate, and did not develop with temperature. The extent of reaction decreased with the decrease in the Co:Ge atomic ratio. No reaction could be detected at the GaAs interface when the Co:Ge atomic ratio was 2:3 even at temperatures as high as 600 °C (for 30 min). Contacts produced in these systems were rectifying with a nearly ideal thermionic emission behavior. This is in contrast to a case of a more Co-rich composition previously studied in our laboratory where contacts with low barriers and extensive interfacial reactions were observed after annealing at 400 °C or higher temperatures.

Interfacial reactions between thin films of cobalt and germanium on (001) oriented GaAs substrates were studied in two configurations, Co/Ge/GaAs and Ge/Co/GaAs, with emphasis on Ge rich stoichiometries. It was found that at low temperatures, 250≤T<350δC, cobalt reacted with germanium to form intermetallie compounds which depended on the Co/Ge atomic ratio, while the inner interface with the GaAs substrate remained intact. At higher temperatures (up to 600δC) a limited reaction with the GaAs substrate was detected. This reaction was contained for both configurations near the interface with the substrate, and did not develop with temperature. The extent of reaction decreased with the decrease in the Co:Ge atomic ratio. Contacts produced in these systems were rectifying with a nearly ideal thermionic emission behavior.