Regensburg 1998 – scientific programme

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HL: Halbleiterphysik

HL 28: Epitaxie

HL 28.9: Talk

Thursday, March 26, 1998, 12:30–12:45, H14

Atomic Contro of Doping during SiGe Epitaxy — •Bernd Tillack — Institute for Semiconductor Physics, Walter-Korsing-Str.2, 15230 Frankfurt (Oder)

P and B atomic layer doping has been achieved using LP(RT)CVD at temperatures between roomtemperature and 400 degrees C. In the case of P doping the process is self-limited. P doses below one monolayer were deposited by separating adsorption of PH3, and de- position of SiGe. Below 400 degree C the dominating process is dissociative adsorption of PH3 with an activation energy of 0.3 eV. At higher temperatures also desorption of P occurs decrea- sing the P dose. For this reason the temperature for P atomic layer doping should be below 550 degree C to control the process by adsorption, only. The P dose incorporated into SiGe may by controlled by partial pressure of phosphine as well as by hy- drogen partial pressure. For B atomic layer doping we found no self-limitation of the diborane adsorption. At low partial pres- sure of diborane it is possible to prepare B peaks with a concen- tration below one monolayer. In this case doping is dominated by dissociative adsorption of diborane at Si surface sites with 0.7 eV activation energy. Using high partial pressures of diborane several monolayers of B were deposited. The diborane is adsorbed at B occupied surface sites. The results indicate atomic control of P and B at very low temperature which is essential especially for decreasing vertical dimensions of electronic devices.