Method for evaluating internal stress of silicon carbide monocrystalline wafer and method for predicting warpage in silicone carbide monocrystalline wafer
View Patent ↗Provided are a method of evaluating an internal stress of a silicon carbide (SiC) single crystal wafer and a method of predicting warpage of the SiC single crystal wafer after completion of polishing by evaluating the internal stress of the wafer. Wavenumber shift amounts of Raman-scattered light are measured at two points within a surface of the SiC single crystal wafer, and the internal stress is evaluated through use of a difference between the wavenumber shift amounts. Also provided is a method of predicting warpage of a silicon carbide single crystal wafer in advance, the silicon carbide single crystal wafer being produced by sublimation-recrystallization method, the method including predicting warpage of a SiC single crystal wafer through use of the evaluation indicator.
1. A method of evaluating an internal stress of a silicon carbide single crystal wafer comprising:
producing a silicon carbide single crystal ingot by sublimation-recrystallization;
cutting out the silicon carbide single crystal wafer from the silicon carbide single crystal ingot;
measuring Raman shift values at two points within a principal surface of the silicon carbide single crystal wafer with a Raman spectrometer;
calculating a Raman index from the Raman shift values; and
evaluating the internal stress of the silicon carbide single crystal wafer from the Raman index,
wherein the measuring Raman shift values comprises:
measuring a first Raman shift value (A) at a center of the silicon carbide single crystal wafer;
measuring a second Raman shift value (B) at an outer peripheral portion of the silicon carbide single crystal wafer; and
calculating a Raman shift difference (A−B) between the first Raman shift value and second Raman shift value, wherein the Raman shift difference is the Raman index.
2. The method of claim 1 , wherein the internal stress of the silicon carbide single crystal wafer is distributed in a concentric fashion.
3. A method of predicting warpage of a silicon carbide single crystal wafer comprising:
producing a silicon carbide single crystal ingot by sublimation-recrystallization;
cutting out the silicon carbide single crystal wafer from the silicon carbide single crystal ingot;
measuring Raman shift values at two points within any one of a front surface and a back surface of the silicon carbide single crystal wafer with a Raman spectrometer;
calculating a Raman index from a difference between the said Raman shift values;
determining a relational expression between the Raman index and the warpage of the silicon carbide single crystal wafer;
predicting an amount of warpage of the silicon carbide single crystal wafer after final polishing from the relational expression; and
finally polishing the silicon carbide single crystal wafer;
wherein the predicting a warpage step is performed before the final polishing step.
4. The method of claim 3 wherein the cutting out the silicon carbide single crystal wafer from the silicon carbide single crystal ingot step comprises
slicing the silicon carbide single crystal wafer from the silicon carbide single crystal ingot.