CHARACTERIZATION OF IN-SITU PHOSPHORUS-DOPED POLYCRYSTALLINE SILICON FILMS GROWN BY DISILANE-BASED LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITION

Low-pressure chemical vapor deposition of in situ phosphorus-doped sil icon films using disilane (Si2H6) and phosphine (PH3) has been investi gated in the growth temperature range of 415 to 560 degrees C and for doping levels between 10(19) and 10(21) cm(-3). Regarding the film dep osition, no significant difference in apparent activation energy was o bserved between the undoped and heavily doped deposition process. The electrical and structural properties of the films grown at 480 degrees C have been studied as a function of doping level and post-heat-treat ment including furnace and rapid thermal annealings. The observed chan ges in film resistivity after isochronal annealings for doping levels above 10(20) cm(-3) are interpreted in terms of dopant segregation and supersaturation of carriers. The impact on resulting film properties when replacing disilane with silane (SiH4) in the deposition process h as been investigated. The films were grown under identical conditions except for the deposition temperature which was 80 degrees C higher fo r the silane than for the disilane case. There is no indication of dif ferent phosphorus incorporation when comparing electrical properties o f crystallized silane-and disilane-based films. However, the disilane layers exhibit larger crystallite grains and lower specific resistivit ies than the silane layers. In addition, the disilane films demonstrat e a strongly preferred <111> texture after crystallization which is ab sent for the silane films. The observations are attributed to the high er degree of disorder of the as-deposited disilane films compared to t he silane films resulting from the difference in deposition temperatur e.