High pressure regime of plasma enhanced deposition of microcrystalline silicon

Abstract

An investigation of the effect of the total gas pressure on the deposition of microcrystalline thin films form highly diluted silane in hydrogen discharges was carried out at two different frequencies. The study was performed in conditions of constant power dissipation and constant silane partial pressure in the discharge while using a series of plasma diagnostics as electrical, optical, mass spectrometric, and in situ deposition rate measurements together with a simulator of the gas phase and the surface chemistry of SiH4∕H2 discharges. The results show that both the electron density and energy are affected by the change of the total pressure and the frequency. This in turn influences the rate of high energy electron–SiH4 dissociative processes and the total SiH4 consumption, which are favored by the frequency increase for most of the pressures. Furthermore, frequency was found to have the weakest effect on the deposition rate that was enhanced at 27.12MHz only for the lowest pressure of 1Torr. On the other hand, the increase of pressure from 1to10Torr has led to an optimum of the deposition rate recorded at 2.5Torr for both frequencies. This maximum is achieved when the rate of SiH4 dissociation to free radical is rather high; the flux of species is not significantly hindered by the increase of pressure and the secondary gas phase reactions of SiH4 act mainly as an additional source of film precursors.

Influence of Hydrogen Plasma on the Defect Passivation of Polycrystalline Si Thin Film Solar Cells

“…In this case the electron density is expected to be at its maximum due to the reduction of charge losses. [21] Such a condition is beneficial for atomic H production as it will reduce the amount of power spent for ion acceleration and will enhance low-energy electron dissociation processes. Different pressures very presumably will lead to a different self-bias and ion bombardment of the films.…”

Electron drift velocity in silane in strong electric fields determined from rf breakdown curves

“…Silane (SiH 4 ) is widely used for depositing hydrogenated amorphous and microcrystalline silicon, SiO 2 and silicon nitride [1][2][3][4][5][6][7][8][9][10]. Therefore a large number of papers are devoted both to experimental studying and to simulating discharge characteristics in SiH 4 (see, e.g., [11][12][13][14][15][16][17]).…”

Highly efficient microcrystalline silicon solar cells deposited from a pure SiH4 flow

“…2͑a͔͒ the entire reactor is filled with the SiH 4 /H 2 gas mixture, whereas in the stable situation after plasma ignition ͓Fig. 2͑e͔͒ the SiH 4 is heavily depleted [8][9][10][11] and the reactor is predominantly filled with H 2 . During the transformation, the SiH 4 depletion in the plasma zone ͓Fig.…”

“…[9][10][11] The reactor used for intrinsic c-Si: H deposition, described in more detail elsewhere, 12 encompassed a showerhead electrode for gas injection, and consisted of a volume of 11 liter, an interelectrode distance of 1.0 cm, and an electrode area of 150 cm 2 . We applied a power of 0.5 W / cm 2 , a pressure of 10 Torr͑1.3ϫ 10 3 Pa͒, a SiH 4 flow of up to 3.3 sccm ͑1.0 standard cm 3 min −1 , or sccm, equals 7.4ϫ 10 −7 mol s −1 ͒, and an H 2 flow of up to 1000 sccm.…”