Phosphorous planar dopant source for low temperature applications

Claim 1

A doping composition for forming a dopant source wafer for doping by vapor phase transport of P 2 O 5 a silicon wafer with phosphorus for low temperature applications, the compsoition consisting essentialy of: (a) finely divided particles of a polycrystalline ceramic having an average linear coefficient of thermal expansion of less than about 32×10 -7/ °C. from zero to 300° C. and consisting essentially of the following oxides in approximate mole percent; ______________________________________ OXIDE MOLE PERCENT ______________________________________ P.sub.2 O.sub.5 45-75 Al.sub.2 O.sub.3 11-28 Ta.sub.2 O.sub.5 6.5-13 SiO.sub.2 0-20 La.sub.2 O.sub.3 0-7 ______________________________________ where P 2 O 5 +Al 2 O 3 +Ta 2 O 5 is at least about 75 mole percent of the composition (b) finely divided particles of Al 2 O 3 , and (c) H 3 PO 4 in an aqueous solution for reaction with Al 2 O 3 to form a binder for the ceramic particles.

Claim 3

A method of doping a silicon wafer comprising the steps of: (A) forming a doping source wafer for doping a silicon wafer with phorphorous, the source wafer being formed from composition comprising: (a) 100 mesh or smaller particles of a polycrystalline ceramic having an average linear coefficient of thermal expansion of less than about 32×10 -7/ °C. from zero to 300° C. and consisting essentially of the following oxides in approximately mole percent: ______________________________________ OXIDE MOLE PERCENT ______________________________________ P.sub.2 O.sub.5 45-75 Al.sub.2 O.sub.3 11-28 Ta.sub.2 O.sub.5 6.5-13 SiO.sub.2 0-20 La.sub.2 O.sub.3 0-7 ______________________________________ where P 2 O 5 +Al 2 O 3 +Ta 2 O 5 is at least about 75 mole percent of the composition, (b) about 100 mesh or smaller particles of Al 2 O 3 , and (c) H 3 PO 4 in an aqueous solution for reaction with Al 2 O 3 to form a binder for the ceramic particles, and (B) firing the doping source wafer to form a glassy layer on a silicon wafer by the vapor phase transport of P 2 O 5 to diffuse phosphorus into the silicon wafer.

Claim 4

A method of doping a silicon wafer comprising the steps of: (A) forming a doping source wafer for doping a silicon wafer with phorphorous, the source wafer being formed from composition comprising: (a) 100 mesh or smaller particles of a polycrystalline ceramic having an average linear coefficient of thermal expansion of less than about 32×10 -7/ °C. from zero to 300° C. and consisting essentially of the following oxides in approximately mole percent: ______________________________________ OXIDE MOLE PERCENT ______________________________________ P.sub.2 O.sub.5 45-75 Al.sub.2 O.sub.3 11-28 Ta.sub.2 O.sub.5 6.5-13 SiO.sub.2 0-20 La.sub.2 O.sub.3 0-7 ______________________________________ where P 2 O 5 +Al 2 O 3 +Ta 2 O 5 is at least about 75 mole percent of the composition, (b) about 100 mesh or smaller particles of Al 2 O 3 , and (c) H 3 PO 4 in an aqueous solution for reaction with Al 2 O 3 to form a binder for the ceramic particles, and (B) firing the doping source wafer to form a glassy layer on a silicon wafer by the vapor phase transport of P 2 O 5 to diffuse phosphorus into the silicon wafer.