Provided is a method for heat-treating a silicon wafer in an inert gas atmosphere, wherein it is possible to discharge SiO gas produced in melting a natural oxide film on the surface of the silicon wafer efficiently, to suppress the accumulation of reaction products in the heat treatment chamber, and to prevent slip deterioration. The wafer is held for a period of 5 to 30 sec inclusive, the rotational speed of the wafer is set to 80 to 120 rpm, and further the inert gas supply in the chamber is controlled so that the gas replacement rate is 90% or more in a temperature range of 900 to 1100° C. inclusive.

In a method for manufacturing a device fabrication wafer, an SiC epitaxial wafer that is an SiC wafer 40 having a monocrystalline SiC epitaxial layer formed thereon is subjected to a basal plane dislocation density reduction step of reducing the density of basal plane dislocations existing in the epitaxial layer of the SiC epitaxial wafer, to thereby manufacture the device fabrication wafer for use to fabricate a semiconductor device. In the basal plane dislocation density reduction step, the SiC epitaxial wafer is heated under Si vapor pressure for a predetermined time necessary to reduce the density of basal plane dislocations, without formation of a cap layer on the SiC epitaxial wafer, so that the density of basal plane dislocations is reduced with suppression of surface roughening.

In various embodiments, single-crystal aluminum nitride boules and substrates are formed from the vapor phase with controlled levels of impurities such as carbon. Single-crystal aluminum nitride may be heat treated via quasi-isothermal annealing and controlled cooling to improve its ultraviolet absorption coefficient and/or Urbach energy.

In various embodiments, single-crystal aluminum nitride boules and substrates are formed from the vapor phase with controlled levels of impurities such as carbon. Single-crystal aluminum nitride may be heat treated via quasi-isothermal annealing and controlled cooling to improve its ultraviolet absorption coefficient and/or Urbach energy.

Nitrogen-doped CZ silicon crystal ingots and wafers sliced therefrom are disclosed that provide for post epitaxial thermally treated wafers having oxygen precipitate density and size that are substantially uniformly distributed radially and exhibit the lack of a significant edge effect. Methods for producing such CZ silicon crystal ingots are also provided by controlling the pull rate from molten silicon, the temperature gradient and the nitrogen concentration. Methods for simulating the radial bulk micro defect size distribution, radial bulk micro defect density distribution and oxygen precipitation density distribution of post epitaxial thermally treated wafers sliced from nitrogen-doped CZ silicon crystals are also provided.

Nitrogen-doped CZ silicon crystal ingots and wafers sliced therefrom are disclosed that provide for post epitaxial thermally treated wafers having oxygen precipitate density and size that are substantially uniformly distributed radially and exhibit the lack of a significant edge effect. Methods for producing such CZ silicon crystal ingots are also provided by controlling the pull rate from molten silicon, the temperature gradient and the nitrogen concentration. Methods for simulating the radial bulk micro defect size distribution, radial bulk micro defect density distribution and oxygen precipitation density distribution of post epitaxial thermally treated wafers sliced from nitrogen-doped CZ silicon crystals are also provided.

Apparatus and methods to process one or more wafers are described. The apparatus comprises a chamber defining an upper interior region and a lower interior region. A heater assembly is on the bottom of the chamber body in the lower interior region and defines a process region. A wafer cassette assembly is inside the heater assembly and a motor is configured to move the wafer cassette assembly from the lower process region inside the heater assembly to the upper interior region.

Apparatus and methods to process one or more wafers are described. The apparatus comprises a chamber defining an upper interior region and a lower interior region. A heater assembly is on the bottom of the chamber body in the lower interior region and defines a process region. A wafer cassette assembly is inside the heater assembly and a motor is configured to move the wafer cassette assembly from the lower process region inside the heater assembly to the upper interior region.

A processing temperature T.sub.S by a rapid thermal processing furnace is 1250° C. or more and 1350° C. or less, and a cooling rate R.sub.d from the processing temperature is in a range of 20° C./s or more and 150° C./s or less, and thermal processing is performed by adjusting the processing temperature T.sub.S and the cooling rate R.sub.d within a range between the upper limit P=0.00207T.sub.S.Math.R.sub.d−2.52R.sub.d+13.3 (Formula (A)) and the lower limit P=0.000548T.sub.S.Math.R.sub.d−0.605R.sub.d−0.511 (Formula (B)) of an oxygen partial pressure P in a thermal processing atmosphere.

A processing temperature T.sub.S by a rapid thermal processing furnace is 1250° C. or more and 1350° C. or less, and a cooling rate R.sub.d from the processing temperature is in a range of 20° C./s or more and 150° C./s or less, and thermal processing is performed by adjusting the processing temperature T.sub.S and the cooling rate R.sub.d within a range between the upper limit P=0.00207T.sub.S.Math.R.sub.d−2.52R.sub.d+13.3 (Formula (A)) and the lower limit P=0.000548T.sub.S.Math.R.sub.d−0.605R.sub.d−0.511 (Formula (B)) of an oxygen partial pressure P in a thermal processing atmosphere.