Method of heat treatment of silicon wafer doped with boron
A method of subjecting a silicon wafer doped with boron to a heat treatment in an argon atmosphere, wherein the argon atmosphere is replaced with a hydrogen atmosphere or a mixed gas of an argon gas and a hydrogen gas in a proper fashion, to thereby uniformize a boron concentration in the thickness direction of the surface layer of the silicon wafer doped with boron.
1. A method for uniformizing a boron concentration in a surface layer of a p-type silicon wafer at a depth up to 10 μm from a surface of the silicon wafer, said p-type silicon wafer cut out from a silicon ingot grown by a Czochralski method and doped with boron in a concentration of 1×10 16 atoms/cm 3 or below, said surface layer of the p-type silicon wafer up to 10 μm from the surface being a device activation area for fabricating a device, wherein
when the silicon wafer is subjected to a heat treatment in a heat treatment furnace at a temperature of up to 1200° C., an entire surface of the silicon wafer has been contaminated with boron prior to charging the silicon wafer into the heat treatment furnace,
the heat treatment comprises:
a first step of removing contamination of the boron adhering to the surface of the silicon wafer by reacting the boron with hydrogen during the heat treatment in a hydrogen 100% atmosphere and a temperature environment of 1200° C. or less, or in a mixed gas of argon gas and hydrogen gas and a temperature environment of 800° C. or higher and less than 1200° C. and
a second step of replacing the atmosphere with an atmosphere consisting of argon, and performing the heat treatment in the argon atmosphere at a temperature of up to 1200° C., the temperature being held at 1200° C. finally.
2. The method according to claim 1 wherein the mixed gas of the argon gas and the hydrogen gas is a mixed gas of an argon gas and a hydrogen gas containing the hydrogen gas in a concentration of an explosion limit or below.
3. A method for uniformizing a boron concentration in a surface layer of a p-type silicon wafer at a depth up to 10 μm from a surface of the silicon wafer, said p-type silicon wafer cut out from a silicon ingot grown by a Czochralski method and doped with the boron in a concentration of 1×10 16 atoms/cm 3 or below, said surface layer of the p-type silicon wafer up to 10 μm from the surface being a device activation area for fabricating a device wherein
when the silicon wafer is subjected to a heat treatment in a heat treatment furnace at temperature of up to 1200° C., an entire surface of the silicon wafer has been contaminated with the boron prior to charging the silicon wafer into the heat treatment furnace,
the heat treatment comprises:
a first step of removing contamination of the boron adhering to the surface of the silicon wafer by performing the heat treatment at a temperature of 1200° C. or less in an atmosphere of argon and hydrogen and by reacting the boron with the hydrogen during the heat treatment; and
a second step of replacing the atmosphere with an atmosphere consisting of argon, and performing the heat treatment in the argon atmosphere at a temperature of up to 1200° C., the temperature being held at 1200° C. finally.