Deposition of Phosphosilicate Glass Layers Having Uniform Thickness and Dopant Concentration Onto Semiconductor Substrates
Original Publication Date: 1983-Oct-01
Included in the Prior Art Database: 2005-Feb-07
Typical open-tube diffusion processes involve gas reactions in the tube to form a doped glass which deposits on the wafers. Gas reactions are: O2 + BBr3 for boron-doped glass, O2 + POCl3 for phosphorous-doped glass. The reacting gases are carried into the tube via a carrier gas (typically, argon). A typical diffusion process sequence involves three phases: I Furnace recovery and temperature equilibrium with: Ar carrier gas + O2 No source (BBr3 or POCl3) II Doped glass deposition: Ar carrier gas + O2 Source (BBr3 or POCl3) III Drive in: Ar carrier gas + O2 It is assumed that the small oxygen flow rate during phase I is enough to form a small nonuniform layer of oxide onto the wafers which, in turn, results in non-uniform thickness and doping of the doped glass layer.