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Control of Minority Carrier Lifetime in Silicon by Cesium Implantation

IP.com Disclosure Number: IPCOM000086257D
Original Publication Date: 1976-Aug-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Sixt, G: AUTHOR

Abstract

Minority carrier lifetime is an important parameter for silicon devices which require short switching times. To control carrier lifetime for optimum device design, it is necessary to introduce a well-known concentration of lifetime doping. In addition, for use in integrated circuits it is desirable that the lifetime can be selectively controlled in different areas.

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Control of Minority Carrier Lifetime in Silicon by Cesium Implantation

Minority carrier lifetime is an important parameter for silicon devices which require short switching times. To control carrier lifetime for optimum device design, it is necessary to introduce a well-known concentration of lifetime doping. In addition, for use in integrated circuits it is desirable that the lifetime can be selectively controlled in different areas.

Gold is frequently used today to adjust carrier lifetime in silicon devices. Gold, however, is a fast diffuser and can therefore be introduced only in a final processing step when all high-temperature processes have been performed.

Cesium can be used as a dopant for the reduction of lifetime in silicon. Cesium has a donor level at midgap that strongly reduces the minority carrier lifetime. Cesium is introduced into the silicon by ion implantation. By use of masking techniques it is easily possible to implant cesium selectively in different areas. Cesium is a slow diffuser as contrasted to gold in silicon. Thus the cesium distribution in the silicon is only slightly affected by temperature treatments at about 1000 degrees C, to restore the damaged silicon lattice after implantation.

Cesium not only controls the carrier lifetime but also affects the doping density in silicon, In N-type silicon for example, the doping density is increased by almost a factor of 10/2/ when implanted with 1 x 10/13/Cs/+//cm/2/. This doping behavior of ces...