Nitrogen Incorporation in Thin Silicon Oxides in a N 2 O Plasma: Effects of Processing Conditions

Abstract

Oxynitrides were grown by constant current anodization of silicon in a plasma. The effects of process conditions such as reactor pressure, flow rate, substrate temperature, and current density on the incorporated nitrogen bonding chemistry, concentration, and spatial distribution were studied using angle‐resolved X‐ray photoelectron spectra of the as‐grown, etched‐back (4.5 nm), and annealed oxynitrides.Current‐voltage and capacitance‐voltage characteristics of the oxynitrides were evaluated. Compared to a reference oxynitride grown at 350 °C, 30 mTorr, 10 sccm, and 3.8 mA/cm2 an increase in substrate temperature (to 400 °C) and current density (to 5 mA/cm2) along with reactor pressure changes (to 15 and 50 mTorr) favored the incorporation of nitrogen in a bonding structure over bonding structures near the interfacial region. A pressure of 15 mTorr and a flow rate of 25 seem, which result in lower residence times, and a temperature of 400 °C, yielded lower nitrogen concentrations (≈0.6 to 1 atom %). Oxynitrides with nitrogen in a bonding structure at the interfacial region, in atomic concentrations of ≈1%, exhibited the highest breakdown fields. Fixed oxide charges were low, with the oxynitride grown at 400 °C having the lowest charge level at 8.5 × 1010 charges/cm2.