Analysis of intermediate pressure SiH₄/He capacitively coupled plasma for deposition of an amorphous hydrogenated silicon film in consideration of thermal diffusion effects

Abstract

To achieve rapid, uniform deposition of an amorphous hydrogenated silicon (a-Si:H) film, a capacitively coupled plasma (CCP) is often used at an intermediate pressure (>100 Pa), with a silane (SiH 4 )-based mixture. At these pressures, heavy particle interactions (such as ion-ion, ion-neutral, and neutral-neutral reactions) contribute significantly to the formation of precursor radicals. By adding a consideration of the thermal diffusion effects to the neutral transport equation, the chemical processes have been numerically analyzed with variation in the number fraction of SiH 4 and electrode spacing using a two-dimensional fluid model of radio frequency discharges in a cylindrically symmetric CCP reactor. The non-uniformity of the deposition rate profiles increases consistently as electrode spacing increases, although the non-uniformity of the plasma parameters decreases with the increase of electrode spacing. The simulated deposition rate profiles match well with the experimental data for the change of electrode spacing. Based on the validation of our model, we propose predictive designs to potentially improve the reactor and process by modifying the thermal and electrical surface conditions.

Theoretical Analysis of Si2H6 Adsorption on Hydrogenated Silicon Surfaces for Fast Deposition Using Intermediate Pressure SiH4 Capacitively Coupled Plasma

“…The experimental setup and methodology were described in detail in our previous studies [28][29][30]. By using an ellipsometer and an X-ray diffractometer, we measured the properties of the Si:H layer experimentally.…”

“…By using an ellipsometer, film thicknesses were measured. To simulate surface depositions, by referring to the surface fluxes of silicon-containing radicals (Si x H y ), a sticking model was applied as similarly performed in previous studies [28][29][30]. Sticking coefficients of radicals were adopted from other groups' experimental data [32,33].…”

“…Particulars of the plasma discharge model were presented in our previous reports [26][27][28][29][30]; therefore, details are omitted here. Only equations about the electron density and flux balances are shown below:…”

Kinetic Analysis of Electrode Heating Effects in a Torr-Regime Capacitively Coupled Plasma Reactor: 2-D Particle-in-Cell Simulation Study

“…At the same time, the mass production of devices requires technically complex and expensive reactors, which have resulted in chipmakers experiencing financial difficulties when expanding the production capacity for a semiconductor device [4]- [6]. Consequently, chipmakers have continuously strived to produce chips more efficiently.…”

“…In the fabrication of advanced microelectronics, equipment design technologies are strongly required to demonstrate challenging uniformity control for plasma deposition [4]- [6]. Therefore, based on the requirement for high productivity and feasibility, capacitively coupled plasma (CCP) reactors operated under pressurized conditions in the torr regime (i.e., p g > 100 Pa, where p g is the gas pressure), are often considered to be the best reactor configuration to uniformly deposit various functional layers such as thin dielectric films [12].…”