Heat treatment method and heat treatment apparatus of light irradiation type
A front surface of a semiconductor wafer is rapidly heated by irradiation of a flash of light. Temperature of the front surface of the semiconductor wafer is measured at predetermined intervals after the irradiation of the flash of light, and is sequentially accumulated to acquire a temperature profile. From the temperature profile, an average value and a standard deviation are each calculated as a characteristic value. It is determined that the semiconductor wafer is cracked when an average value of the temperature profile deviates from the range of ±5σ from a total average of temperature profiles of a plurality of semiconductor wafers or when a standard deviation of the temperature profile deviates from the range of 5σ from the total average thereof of the plurality of semiconductor wafers.
1. A heat treatment method for irradiating a substrate with a flash of light to heat the substrate, the heat treatment method comprising the steps of:
(a) preliminarily heating a substrate using a continuous lighting lamp;
(b) irradiating a front surface of said substrate with a flash of light from a flash lamp;
(c) acquiring a temperature profile by measuring temperature of the front surface of said substrate for a predetermined period starting at a beginning of the step (b), wherein the temperature profile for the period includes increase and decrease in temperature of the front surface of said substrate; and
(d) determining that said substrate is cracked when a characteristic value, calculated from said temperature profile for the period including increase and decrease in temperature of the front surface of the substrate, is out of a predetermined range.
2. The heat treatment method according to claim 1 , wherein said step (d) includes a step of selecting and setting said characteristic value.
3. The heat treatment method according to claim 1 , wherein in said step (c), temperature of the front surface of said substrate is measured from intensity of infrared light having a wavelength from 5 μm to 6.5 μm emitted from the front surface of said substrate.
4. The heat treatment method according to claim 1 , wherein
an average value and a standard deviation of said temperature profile each serve as said characteristic value, and
it is determined in said step (d) that said substrate is cracked when an average value of said temperature profile is out of a predetermined range, or a standard deviation of said temperature profile is out of a predetermined range.
5. The heat treatment method according to claim 4 , wherein it is determined in said step (d) that said substrate is cracked when an average value of said temperature profile is out of a range of ±5σ, or a standard deviation of said temperature profile exceeds a range of 5σ.
6. A heat treatment apparatus for heating a substrate by irradiating said substrate with a flash of light, the heat treatment apparatus comprising:
a chamber that houses the substrate;
a continuous lighting lamp for preliminarily heating said substrate;
a flash lamp that irradiates a front surface of said substrate housed in said chamber with a flash of light;
a radiation thermometer that measures temperature of the front surface of said substrate by receiving infrared light emitted from the front surface;
a profile acquiring unit that acquires a temperature profile of the front surface of said substrate, measured by said radiation thermometer for a predetermined period starting at a beginning of irradiation by said flash lamp, after preliminarily heating said substrate by said continuous lighting lamp, wherein the temperature profile for the period includes increase and decrease in temperature of the front surface of said substrate; and
an analyzing unit that determines that said substrate is cracked when a characteristic value, calculated from said temperature profile for the period including increase and decrease in temperature of the front surface of the substrate is out of a predetermined range.
7. The heat treatment apparatus according to claim 6 , further comprising: a setting unit for setting the characteristic value.
8. The heat treatment apparatus according to claim 6 , wherein said radiation thermometer is configured to measure temperature of the front surface of said substrate from intensity of infrared light having a wavelength from 5 μm to 6.5 μm emitted from the front surface of said substrate.
9. The heat treatment apparatus according to claim 6 , wherein
an average value and a standard deviation of said temperature profile each serve as said characteristic value, and
said analyzing unit is configured to determine that said substrate is cracked when an average value of said temperature profile is out of a predetermined range, or a standard deviation of said temperature profile is out of a predetermined range.
10. The heat treatment apparatus according to claim 9 , wherein said analyzing unit is configured to determine that said substrate is cracked when an average value of said temperature profile is out of a range of ±5σ, or a standard deviation of said temperature profile exceeds a range of 5σ.