The addition of He to N-2 increases significantly the deposition rate of lithium phosphorus oxynitride thin films by radio frequency magnetron sputtering of Li3PO4 targets. From the correlation with the optical emission intensity, the enhanced rate is attributed to an increase in the N-2(+) ion concentration in the plasma due to Penning ionization. The ionic conductivity of the films deposited at higher rates in He+20% N-2 compares favorably with that of films deposited at lower rates in pure N-2.