Gas phase considerations for the growth of device quality nanocrystalline silicon at high rate

Abstract

a b s t r a c tIn order to increase industrial viability and to find niche markets, high deposition rate and low temperature depositions compared to standard deposition conditions are two recent trends in research areas concerning thin film silicon. In situ diagnostic tools to monitor gas phase conditions are useful in quick optimization processes of deposition parameters without going into time consuming material characterizations. Optical emission spectroscopy is an efficient technique to monitor/predict growth rate and phase of the material (amorphous or nanocrystalline). However, at high growth rate conditions which are generally achieved at high chamber pressures (p), the simple correlation breaks down. We see that at high pressure condition a higher H ␣ /Si * is needed for the onset of crystallinity than that is found at lower pressure conditions. Additional methods such as estimating the silane depletion from the experiment and the flux ratio of atomic hydrogen to deposited silicon atoms from simulations can be used for fine-tuning the amorphous to nanocrystalline transition regime. On the other hand, intensity of Si * line loses its character as a monitoring tool for deposition rate. Moreover, the plasma changes its character when the pressure is varied, even when the pd product is kept constant. In situ diagnosis of the ion energy distribution function by a retarding field ion energy analyzer has thrown new lights on the role of hydrogen dilution for depositions at low substrate temperature conditions, namely to compensate the loss in ion energy due to lower gas temperature.

Ion bombardment measurements and simulations of a low temperature VHF PECVD SiH4–H2 discharge in the a‐Si:H to μc‐Si:H transition regime

“…With decreasing silane concentration in the plasma the amorphous silicon growth rate comes down . The silane concentrations in the plasma used here can result in Si layer growth on both sides of the amorphous to micro‐crystalline silicon transition . We have observed a crystalline fraction in the film on a Si⟨111⟩ wafer at R = 59 and no crystalline phase at lower dilutions.…”

Solar cells for self-sustainable intelligent packaging

“…The intensity of SiH* (I SiH *) can also be used to infer the deposition rate, since an increase of the SiH* intensity indicates a higher rate; 33 such parameter control is essential when producing solar cells. 39 The intensity ratios, I H b /I H a [39][40][41] and I Si */I SiH *, 42,43 also provide information on electron temperature (T e ). Since T e is also sensitive to the gas temperature in the plasma, a higher temperature leads to a decrease of the molecular density and elongation of inter-molecular distance for the acceleration of electrons in the plasma and consequently higher T e .…”

Combinatorial Deposition of Microcrystalline Silicon Films Using Multihollow Discharge Plasma Chemical Vapor Deposition

“…13,14) For the high pressure depletion method, a wider process window should be realized based on the knowledge of deposition mechanism in detail. 15) To gain further insight into the deposition mechanism, we have applied a multihollow discharge plasma chemical vapor deposition (CVD) method by which contribution of SiH 3 radicals and H atoms to deposition as well as their flux ratio varies with the distance between the substrates and the discharges. [16][17][18][19] In this article, we present the experimental results obtained under the high pressure depletion conditions and, based on the results we discuss relation between the process window and pressure.…”