Method for evaluating quality of SiC single crystal body and method for producing silicon carbide single crystal ingot using the same
A method for evaluating the quality of a SiC single crystal by a non-destructive and simple method; and a method for producing a SiC single crystal ingot with less dislocation and high quality with good reproducibility utilizing the same. The method for evaluating the quality of a SiC single crystal body is based on the graph of a second polynomial equation obtained by differentiating a first polynomial equation, the first polynomial equation approximating the relation between a peak shift value and a position of the measurement point and the peak shift value being obtained by an X-ray rocking curve measurement. The method for producing a SiC single crystal ingot manufactures a SiC single crystal ingot by a sublimation recrystallization method using, as a seed crystal, the SiC single crystal body evaluated by the evaluation method.
1. A method for evaluating the quality of a SiC single crystal body composed of a disc-shaped silicon carbide single crystal,
which comprises
conducting an X-ray rocking curve measurement of a main surface of the SiC single crystal body on a predetermined diffraction surface;
obtaining an angle Ω at a plurality of measurement points P n on a diameter of the main surface, wherein the Ω is an angle between an X-ray incident direction and the main surface when a diffraction peak is exhibited; and
calculating the difference (Ω n −Ω 0 ) as a respective peak shift value, in which Ω 0 is an angle at a certain reference measurement point P 0 and Ω n is an angle at a measurement point P n other than P 0 among these measurement points;
obtaining a relation between the location of the measurement point P n (X) on the diameter of the main surface and the peak shift value (Y) as a first polynomial equation;
linearly differentiating the first polynomial equation to obtain a second polynomial equation, and evaluating the quality of the SiC single crystal body based on these polynomial equations.
2. The method for evaluating the quality of a SiC single crystal body according to claim 1 , wherein, when the second polynomial equation is expressed as a graph in which the Y axis indicates the inclination of the first polynomial equation and the X axis indicates the position of the measurement point P n on the diameter of the main surface of the SiC single crystal body, the quality is evaluated by determining whether the graph of the second polynomial equation passes Y=0 or not.
3. The method for evaluating the quality of a SiC single crystal body according to claim 2 , wherein the quality is evaluated by determining whether a graph representing the second polynomial equation passes Y=0 twice or not.
4. The method for evaluating the quality of a SiC single crystal body according to claim 2 , wherein the quality is evaluated by determining whether a function of a peak shift value (Y) in the first polynomial equation has a local maximum value or a local minimum value.
5. The method for evaluating the quality of a SiC single crystal body according to claim 1 , wherein, when the second polynomial equation is expressed as a graph in which the Y axis indicates the inclination of the first polynomial equation and the X axis indicates the position of the measurement point on the diameter of the main surface of the SiC single crystal body, the quality is evaluated by a difference between a maximum value and a minimum value of the inclination (Y).
6. The method for evaluating the quality of a SiC single crystal body according to claim 1 , wherein the degree of the first polynomial equation is 4 or more.
7. The method for evaluating the quality of a SiC single crystal body according to claim 1 , wherein the reference measurement point P 0 is a center point of the main surface of the SiC single crystal body.
8. The method for evaluating the quality of a SiC single crystal body according to claim 1 , which comprises determining a basal surface dislocation density of the SiC single crystal body.
9. A method for producing a silicon carbide single crystal ingot which comprises growing a silicon carbide single crystal on a seed crystal by a sublimation recrystallization method,
wherein
an X-ray rocking curve measurement of a main surface of a SiC single crystal body composed of a disc-shaped silicon carbide single crystal is previously conducted on a predetermined diffraction surface;
an angle Ω is obtained at a plurality of measurement points P n on a diameter of the main surface, wherein the Ω is an angle formed between an X-ray incident direction and the main surface when a diffraction peak is exhibited;
the difference Ω n −Ω 0 is calculated as a respective peak shift value, in which Ω 0 is an angle at a certain reference measurement point P 0 and Ω n is an angle at a measurement point P n other than P 0 among these measurement points;
a relationship between the position of the measurement point P n (X) on the diameter of the main surface and the peak shift value (Y) is obtained as a first polynomial equation;
the first polynomial equation is linearly differentiated to obtain a second polynomial equation, and when thus obtained second polynomial equation is expressed as a graph in which the Y axis indicates the inclination of the first polynomial equation and the X axis indicates the position of the measurement point P n on the diameter of the main surface of the SiC single crystal body, the SiC single crystal body whose graph does not pass Y=0 twice or more is used as the seed crystal.