Effect of substrate temperature on the growth and properties of boron-doped microcrystalline silicon films

Highly conductive boron-doped hydrogenated microcrystalline silicon (muc-Si:H) films are prepared by very high frequency plasma enhanced chemicalvapour deposition (VHF PECVD) at the substrate temperatures $T_{rm S})$rangingfrom 90$^circ$C to 270$^circ$C. The effects of $T_{rm S}$ on the growth andproperties of the films are investigated. Results indicate that the growthrate, the electrical (dark conductivity, carrier concentration and Hallmobility) and structural (crystallinity and grain size) properties are allstrongly dependent on $T_{rm S}$. As $T_{rm S}$ increases, it isobserved that 1)the growth rate initially increases and then arrives at a maximum value of13.3 nm/min at $T_{rm S}$=210$^circ$C, 2) the crystalline volume fraction($X_{rm c})$ and the grain size increase initially, then reach their maximumvalues at $T_{rm S}$=140$^circ$C, and finally decrease, 3) the darkconductivity ($sigma _{rm d})$, carrier concentration and Hall mobility havea similar dependence on $T_{rm S}$ and arrive at their maximum values at$T_{rm S}$=190$^circ$C. In addition, it is also observed that at a lowersubstrate temperature $T_{rm S}$, a higher dopant concentration is required inorder to obtain a maximum $sigma _{rm d}$.