Silicon carbide single crystal wafer and manufacturing method for same

Patent metadata

Field	Value
Publication number	US-9234297-B2
Application number	US-201214241623-A
Country	US
Kind code	B2
Filing date	Aug 29, 2012
Priority date	Aug 29, 2011
Publication date	Jan 12, 2016
Grant date	Jan 12, 2016

Abstract

Provided are a method for manufacturing a SiC single crystal having high crystal quality and, in particular, extremely low screw dislocation density and a SiC single crystal ingot obtained by the method. In particular, provided is a silicon carbide single crystal substrate that is a substrate cut from a bulk silicon carbide single crystal grown by the Physical Vapior Transport (PVT) method, in which the screw dislocation density is smaller in the peripheral region than in the center region, so that screw dislocations are partially reduced.
The method is a method for manufacturing a SiC single crystal by the PVT method using a seed crystal and the ingot is a SiC single crystal ingot obtained by the method. Particularly, the silicon carbide single crystal substrate is a silicon carbide single crystal substrate in which when, by representing the diameter of the substrate as R, a center circle region having a diameter of 0.5×R centered around a center point O of the substrate and a doughnut-shaped peripheral region remaining by excluding the center circle region are defined, the average value of screw dislocation densities observed in the doughnut-shaped peripheral region is 80% or less of the average value of screw dislocation densities observed in the center circle region.

First claim

The invention claimed is:

1. A silicon carbide single crystal substrate that is a disk-shaped silicon carbide single crystal substrate cut from a bulk SiC single crystal grown by the Physical Vapor Transport (PVT) method, the silicon carbide single crystal substrate being characterized in that when, by representing the diameter of the substrate as R, a center circle region having a diameter of 0.5×R centered around a center point O of the substrate and a doughnut-shaped peripheral region remaining by excluding the center circle region of the substrate are defined, the average value of screw dislocation densities observed in the doughnut-shaped peripheral region is 80% or less of the average value of screw dislocation densities observed in the center circle region.

2. The silicon carbide single crystal substrate according to claim 1 , wherein the average value of the screw dislocation densities observed in the doughnut-shaped peripheral region is 60% or less of the average value of the screw dislocation densities observed in the center circle region.

3. The silicon carbide single crystal substrate according to claim 1 , wherein the average value of the screw dislocation densities observed in the doughnut-shaped peripheral region is 50% or less of the average value of the screw dislocation densities observed in the center circle region.

4. The silicon carbide single crystal substrate according to claim 1 , wherein when four diameters dividing the circumference of the substrate into eight equal parts are arbitrarily selected on the substrate and eight radii r 1 to r 8 extending radially from the center point O of the substrate set to 0 are regarded as axes, each scaled from 0 to 1, the average value of the screw dislocation densities observed in the center circle region is an average of values measured at total 17 measurement points of i) to iii) below and the average value of the screw dislocation densities observed in the doughnut-shaped peripheral region is an average of values measured at total 16 measurement points of iv) to v) below:
i) center point O
ii) a 1 to a 8
iii) b 1 to b 8
iv) c 1 to c 8
v) d 1 to d 8
wherein numerals appended to symbols a to d correspond to numerals of the radii r 1 to r 8 and, for example, a 1 , b 1 , c 1 , and d 1 represent measurement points present on the radius r 1 ; among the measurement points, a and b represent measurement points present within a range of from more than 0 and not more than 0.5 in each radius, and c and d represent measurement points present within a range of from more than 0.5 and not more than 1; and eight measurement points having the same symbol are present on the same circle of each of the symbols a to d.

5. The silicon carbide single crystal substrate according to claim 4 , wherein the average value of the screw dislocation densities observed in the doughnut-shaped peripheral region is 500/cm 2 or less.

6. The silicon carbide single crystal substrate according to claim 4 , wherein the average value of the screw dislocation densities observed in the doughnut-shaped peripheral region is 300/cm 2 or less.

7. The silicon carbide single crystal substrate according to claim 4 , wherein the average value of the screw dislocation densities observed in the doughnut-shaped peripheral region is 100/cm 2 or less.

8. A method for manufacturing a silicon carbide single crystal by the PVT method using a seed crystal, the method being characterized by including:
a first growth step of growing a silicon carbide single crystal having a thickness of at least 0.5 mm at a first growth atmosphere pressure of from 3.9 to 39.9 kPa and a first growth temperature in which the temperature of the seed crystal is not less than 2100° C. and below 2300° C., wherein a first growth rate is 100 μm/h or less, and
a second growth step of growing the silicon carbide single crystal to a larger thickness than in the first growth step at a second growth atmosphere pressure of from 0.13 to 2.6 kPa and a second growth temperature in which the temperature of the seed crystal is higher than the first growth temperature and below 2400° C.

9. The method for manufacturing a silicon carbide single crystal according to claim 8 , wherein the first growth atmosphere pressure is reduced to the second growth atmosphere pressure at a pressure changing rate of 12 kPa or less per hour.

10. The method for manufacturing a silicon carbide single crystal according to claim 8 , wherein the first growth temperature is increased to the second growth temperature at a temperature changing rate of 40° C. or less per hour.

11. The method for manufacturing a silicon carbide single crystal according to claim 8 , wherein the first growth step is performed at a crystal growth rate of 100 μm/hr or less.

12. The method for manufacturing a silicon carbide single crystal according to claim 8 , wherein, in the entire growth process including the first and the second growth steps, the first growth step is performed within a time of ½ or less of the entire growth process after starting the crystal growth.

13. The silicon carbide single crystal substrate according to claim 2 , wherein when four diameters dividing the circumference of the substrate into eight equal parts are arbitrarily selected on the substrate and eight radii r 1 to r 8 extending radially from the center point O of the substrate set to 0 are regarded as axes, each scaled from 0 to 1, the average value of the screw dislocation densities observed in the center circle region is an average of values measured at total 17 measurement points of i) to iii) below and the average value of the screw dislocation densities observed in the doughnut-shaped peripheral region is an average of values measured at total 16 measurement points of iv) to v) below:
i) center point O
ii) a 1 to a 8
iii) b 1 to b 8
iv) c 1 to c 8
v) d 1 to d 8
wherein numerals appended to symbols a to d correspond to numerals of the radii r 1 to r 8 and, for example, a 1 , b 1 , c 1 , and d 1 represent measurement points present on the radius r 1 ; among the measurement points, a and b represent measurement points present within a range of from more than 0 and not more than 0.5 in each radius, and c and d represent measurement points present within a range of from more than 0.5 and not more than 1; and eight measurement points having the same symbol are present on the same circle of each of the symbols a to d.

14. The silicon carbide single crystal substrate according to claim 3 , wherein when four diameters dividing the circumference of the substrate into eight equal parts are arbitrarily selected on the substrate and eight radii r 1 to r 8 extending radially from the center point O of the substrate set to 0 are regarded as axes, each scaled from 0 to 1, the average value of the screw dislocation densities observed in the center circle region is an average of values measured at total 17 measurement points of i) to iii) below and the average value of the screw dislocation densities observed in the doughnut-shaped peripheral region is an average of values measured at total 16 measurement points of iv) to v) below:
i) center point O
ii) a 1 to a 8
iii) b 1 to b 8
iv) c 1 to c 8
v) d 1 to d 8
wherein numerals appended to symbols a to d correspond to numerals of the radii r 1 to r 8 and, for example, a 1 , b 1 , c 1 , and d 1 represent measurement points present on the radius r 1 ; among the measurement points, a and b represent measurement points present within a range of from more than 0 and not more than 0.5 in each radius, and c and d represent measureme

Assignees

• Sato Shinya
• Fujimoto Tatsuo
• Tsuge Hiroshi
• Katsuno Masakazu
• Nippon Steel & Sumitomo Metal Corp

Inventors

• Sato Shinya
• Fujimoto Tatsuo
• Tsuge Hiroshi
• Katsuno Masakazu

Classifications

• H10D62/8325

  Silicon carbide · CPC title

• C30B23/00 Primary

  Single-crystal growth by condensing evaporated or sublimed materials · CPC title

• Y10T428/21

  Circular sheet or circular blank · CPC title

• C30B23/02 Primary

  Epitaxial-layer growth · CPC title

• C30B29/36

  Carbides · CPC title