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The deposition of epitaxial silicon films at temperatures from 600°–800°C by both very low‐pressure chemical vapor deposition (VLPCVD) and plasma‐enhanced chemical vapor deposition (PECVD) has been examined. The VLPCVD deposition process is first order in silane partial pressure, zero order in hydrogen partial pressure, and exhibits a low, 8–12 kcal/ mole, activation energy for temperatures from 700°–800°C with 1–15 mtorr silane and hydrogen. For temperatures below 700°C an activation energy of 40 kcal/mole is observed. The growth rate depends upon surface orientation, decreasing in the order (100), (111), polycrystalline, indicating surface processes are rate controlling. The low activation energy regime is associated with a process controlled by silane adsorption and decomposition on a sparsely covered silicon surface. The higher activation energy regime is thought to reflect growth under conditions of high surface coverage with silane fragments and the transition temperature is thought to be pressure dependent. Conditions for the deposition of device quality epitaxial silicon at low temperatures are defined and discussed. Plasma enhancement of the VLPCVD process is discussed in a companion paper.

I n situ arsenic doping of epitaxial silicon films deposited from 700 to 800 °C by both very-low-pressure chemical vapor deposition (VLPCVD) and plasma-enhanced chemical vapor deposition (PECVD) has been investigated. The growth rate and morphology of films deposited by silane VLPCVD are degraded in the presence of arsine. The overall activation energy for deposition increases and the apparent silane reaction order decreases relative to VLPCVD in the absence of arsine. VLPCVD arsenic incorporation depends sublinearly on the arsine partial pressure and appears to saturate for incorporation fractions above 1018 As atoms/cm3. PECVD growth rates are less sensitive to arsine, and plasma enhancement is seen to provide significant advantages for n-type doping of epitaxial silicon at low temperatures. PECVD deposits show an order-of-magnitude increase in active dopant incorporation, exhibit superior morphology relative to VLPCVD, and allow for increased doping flexibility. Incorporation remains proportional to arsine partial pressures over the entire range investigated and allows for doping to at least 7×1019 As atoms/cm3 for PECVD. Both VLPCVD and PECVD arsenic-incorporation fractions increase with decreasing temperature. PECVD incorporation also exhibits a weak plasma power dependence. Ion-bombardment-induced disruption of arsenic surface aggregation is proposed to account for the observed doping behavior and plasma enhancement. A companion paper discusses boron doping during low-temperature epitaxial growth.

A low-energy argon sputter process has been optimized to successfully remove native oxide from a silicon surface at elevated temperatures without introducing permanent damage. The process relies upon confining all sputtering events to the near-surface region of the silicon and exploits the enhancement of sputter efficiencies observed for silicon and silicon dioxide above 600 °C. The procedure has been implemented as an in situ etch for low-temperature (below 800 °C), very low-pressure (1–10 mTorr), epitaxial silicon deposition in a high vacuum ambient. The reactor and conditions employed are presented along with measures of residual substrate damage as a function of processing conditions, and the process limitations are discussed. A companion paper describes the excellent structural quality of the resultant epitaxial films. The ion energies (100 eV) and fluxes (5×1013 cm−2 s−1) employed represent a significant departure from conventional sputter cleaning processes.

The use of a plasma during the deposition of epitaxial silicon from 750 to 800 °C is explored. Emphasis is placed on enhancement of the deposition process as opposed to the predeposition surface clean. Plasma enhancement of the deposition process is observed without a change in the apparent activation energy, and the mild ion bombardment (plasma) exposure during deposition introduced no additional defects observable by cross-sectional transmission electron microscopy. Plasma enhancement is also shown to facilitate deposition of high-quality epitaxial silicon films with low levels of unintentional impurity incorporation.