Method for evaluating atomic vacancy in surface layer of silicon wafer and apparatus for evaluating the same

An apparatus for evaluating atomic vacancy in a surface layer of a silicon wafer, comprising:

• a silicon sample provided with an ultrasonic wave generating portion and an ultrasonic wave receiving portion;
• a magnetic field generator for applying an external magnetic field to the silicon sample;
• a refrigerator for cooling the silicon sample;
• and
• a measuring means for detecting a difference in phase between an ultrasonic wave pulse injected from the ultrasonic wave generating portion and an ultrasonic wave pulse propagated in the silicon sample and received at the ultrasonic wave receiving portion;
• wherein the ultrasonic generating portion and the ultrasonic receiving portion are respective comb-shaped electrodes formed on corresponding piezoelectric films and are formed on the same main surface of the silicon sample.

A method for manufacturing a silicon wafer, comprising steps of:

• forming a pair of surface acoustic wave (SAW) devices which are arranged opposite to one another on the same main surface of a silicon sample;
• generating an ultrasonic wave pulse from one of the surface acoustic wave (SAW) devices and propagating the ultrasonic wave pulse in a surface layer of the silicon sample while the silicon sample is cooled under a condition of an application of magnetic field, and receiving the propagated ultrasonic wave pulse at the other of the surface acoustic wave (SAW) devices, thereby measuring a difference in phase between the injected ultrasonic wave pulse and the propagated ultrasonic wave pulse;
• and
• calculating an elastic constant Cs of the surface layer of the silicon sample based on the difference in phase and evaluating a concentration “N” of atomic vacancy of the surface layer of the silicon sample based on a change of the elastic constant Cs with a temperature or a change of the elastic constant Cs with an intensity of the magnetic field.