H.D. Goldbach

Reaction Mechanism for Deposition of Silicon Nitride by Hot-Wire CVD with Ultra High Deposition Rate(>7 nm/s)

The deposition process of silicon nitride (SiN x ) by hot-wire chemical vapor deposition (HW CVD) is investigated by exploring the effects of process pressure and gas-flow ratio on the composition of the deposited SiNx films. Furthermore, experiments with D 2 and deuterated silane were performed to gain further insight in the deposition reactions taking place. It appeared that the N/Si ratio in the layers determines the structural properties of the deposited films and since the volume concentration of Si-atoms in the deposited films is constant with N/Si ratio, the structure of the films are largely determined by the quantity of incorporated nitrogen. Because the decomposition rate of the ammonia source gas is much smaller than that of silane, the properties of the SiN x layers are largely determined by the ability to decompose the ammonia and to incorporate nitrogen into the growing material. It appeared that the process pressure greatly enhances the efficiency of the ammonia decomposition, presumably caused by the higher partial pressure of atomic hydrogen. With this knowledge we increased the deposition rate to a very high value of 7 nm/s for dense transparent SiN x films, much faster than conventional deposition techniques for SiN x can offer. Despite this high deposition rate good control over the composition is achieved by varying the flow ratio of the source gasses. Depositions performed with deuterated silane as a source gas reveal that almost all hydrogen in N-rich films originates from ammonia, probably caused by SiN x matrix formation by cross linking reactions

Silicon Nitride as Dielectric Medium Deposited at Ultra High Deposition Rate (>7 nm/s) using Hot-Wire Chemical Vapor Deposition

The deposition process of silicon nitride (SiNx) by hot-wire chemical vapor deposition (HWCVD) is investigated by exploring the effects of process pressure and gas-flow ratio on the composition of the SiNx films. It appeared that the N/Si ratio in the layers determines the structural properties of the deposited films. The volume concentration of Si-atoms in the deposited films appeared to be independent of N/Si ratio. Because in a silane/ammonia mixture the decomposition rate of ammonia is smaller than that of silane, the properties of the SiNx layers are largely determined by the ability to incorporate nitrogen into the growing material. An increase in the process pressure greatly enhances the efficiency of the ammonia decomposition, which is ascribed to the higher partial pressure of atomic hydrogen originating from the decomposition of silane molecules. With this knowledge we were able to increase the deposition rate of high-density SiNx films to a very high value of 7 nm/s, much faster than any commercial plasma deposition technique can offer. Despite this high deposition rate, the SiNx layers still posses a high mass density of 2.6 g/cm3 and good thermal stability. Current–voltage (I–V) and capacitance–voltage (C–V) measurements show that silicon nitride deposited at high deposition rate has good potential for application as the dielectric layer in various applications.

Hot-wire chemical vapor deposition of silicon nitride for multicrystalline silicon solar cells

A new regime of high rate deposition of silicon nitride by hot wire chemical vapor deposition was investigated. The present design of the filament arrangement and the showerhead gas supply system allows for virtually unlimited scale-up. The deposition rates obtained were in excess of 5 nm/s. The refractive index (n at 2 eV; wavelength /spl sim/630 nm) could be controlled from 1.90 /spl plusmn/ 0.05 to 2.5 /spl plusmn/ 0.05, by varying the SiH/sub 4/ flow and the extinction coefficient (k) at 3.1 eV (wavelength 400 nm) was < 0.007 for all films of interest. The layers were tested on multicrystalline silicon solar cells in order to assess their passivation and antireflection properties. The cells had state-of-the-art values for all photovoltaic parameters, similar to cells with a microwave plasma deposited SiN/sub x/ anti-reflection coating. An efficiency of 14.3% was reached using HWCVD-SiN/sub x/ for multi-crystalline Si solar cells with an industrial process using screen printing.