Fabrication of Undoped and N + Microcrystalline si Films Using SiH 2 Ci 2
- PDF / 311,770 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 24 Downloads / 231 Views
ABSTRACT We have studied the growth of undoped and n+ [c-Si:H(:Cl) films by Remote Plasma CVD using SiH 4/SiH 2CI 2/H2/He mixtures. It was found that the .tc-Si film can be fabricated by increasing flow rate of SiH 2 CI 2 and/or H2 . The deposited undoped ýtc-Si film exhibited a maximum crystalline volume fraction of 85 %, obtained from Raman spectroscopy. The n-type lic-Si film, deposited with SiH 4/SiH 2Cl 2/H2/PH 3/He mixtures, shows a room temperature conductivity of 2 S/cm, conductivity activation energy of 29.8 meV and optical band gap of -2.0 eV. The optical band gap of n-type lic-Si deposited using SiH 2 CI 2 is much higher compared to conventional PcSi film.
INTRODUCTION Microcrystalline silicon (iic-Si) has been drawing attention for their realized and potential applications in large area electronic devices[l]. It was motivated from the properties of high electrical conductivity and large optical band gap compared to n-type hydrogenated amorphous silicon (a-Si:H). Especially, heavily phosphorous doped ltc-Si is widely used as ohmic contact layer in an a-Si:H TFTs as well as in a-Si:ll solar cells[2]. It is known that a high hydrogen dilution in a silane plasma produces Vtc-Si:H thin films at relatively low substrate temperature[3]. The V.c-Si films can also be fabricated by various deposition techniques: plasma enhanced chemical vapor deposition (PECVD) of SiF 4/H2, or of SiH 2F2/H2/SiH 4 [4], photo CVD[5] and hydrogen radical enhanced CVD[6]. In all cases, hydrogen and fluorine radicals play an important role. In this work, we have investigated the electrical, structural and optical properties for the undoped and n+ ltc-Si films deposited by remote plasma chemical vapor deposition (RPCVD) using SiH 2 CI 2. The effect of rf power on the sturctural properties of undoped ltc-Si film, together with the SiH 2CI 2 flow rate effect on the structural and electrical properties of n-type pjc-Si have been investigated.
EXPERIMENTS The undoped and heavily phosphorous doped Itc-Si films were deposited by RPCVD using SiH 4/SiH 2C12/H2/He mixtures. The important growth parameters are shown in Table I. We used He as a non-depositing, exciting species. He was passed through the plasma generating region contained inside a cylindrical quartz tube of a diameter of 3.8 cm. The distance between the bottom of the quartz tube and substrate holder in the deposition reactor was -10 cm. Downstream 75 Mat. Res. Soc. Symp. Proc. Vol. 377 01995 Materials Research Society
from the plasma, in the deposition area, SiH /SiH 2 C12/H 2 were added for deposition of l•tc-Si films. The infra-red (IR) absorption and Raman4 scattering were measured by Bomem 100 FT-IR and Jobin Yvon U1000, respectively, to investigate the structure of lptc-Si. The crystalline volume fraction of film was determined by deconvolution of Raman spectrum into amorphous and crystalline components[7]. The optical absorbance was measured by Cary 17-D spectrophotometer. The optical band gap was obtained from Tauc's plot. The electrical conductivity in the dark((•d) wa
Data Loading...
