Silicon dioxide is a widely used material in semiconductor industry. It is used for instance as a gate oxide and as a dielectric layer in dynamic random access memories (DRAM). Recently, other possible applications have evolved that would require good step coverage and good SiO₂ filling capabilities, for example shallow trench isolation (STI). ALD has been proposed as a possible technique to meet these more stringent requirements. Unfortunately, the growth rate per cycle has traditionally been low for ALD SiO₂ processes making the processing economically non-viable. New precursors with higher reactivity enabling higher growth rate are therefore needed.

In this study, two silicon precursors were tested: tris(dimethylamino)silane (trisDMAS) and SAM.24 from Air Liquide. Ozone was used as the oxygen source. The depositions were done in ASM Pulsar^®2000 ALCVD™ reactor on 200 mm silicon wafers. The film thickness and uniformity were determined with a spectroscopic ellipsometer.

TrisDMAS was tested at 250 – 325 °C. Only very low growth rates were obtained when a 0.2-s trisDMAS pulse was used, the growth rate was increased from 0.07 to 0.09 Å/cycle with increasing deposition temperature. The film non-uniformity was also increased with increasing temperature from 5.4 to 10% (Uf 1σ). The highest growth rate was achieved with 0.5-s precursor pulses at 275 °C: 0.15 Å/cycle. The non-uniformity% was 4.8.

Depositions using SAM.24 were done at 250 and 300 °C. When 0.5-s precursor pulses were used, the growth rate and non-uniformity% were 0.15 Å/cycle and 4.8% at 250 °C, and 0.35 Å/cycle and 4.7% at 300 °C. A higher growth rate of 0.4 Å/cycle was achieved both at 250 and 300 °C using 1.0-s precursor pulses.

In this paper, the effect of deposition parameters on the growth of SiO₂ will be presented.

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