Method for manufacturing defect-free silicon single crystal

Abstract

A method for controlling the temperature gradient on the side surface of a silicon single crystal, the height of a solid-liquid interface, and the oxygen concentration in the longitudinal direction of the silicon single crystal is provided in order to manufacture a defect-free silicon single crystal whose oxygen concentration is controlled to a predetermined value rapidly and stably. By disposing a cylindrical cooler around the silicon single crystal, and adjusting the pulling speed of the silicon single crystal, the rotation speed of a crucible that stores molten silicon and the rotation speed of the silicon single crystal, and the output ratio of a multi-heater separated into at least two in the longitudinal direction of the silicon single crystal disposed around the crucible, the temperature gradient on the side surface, the height of the solid-liquid interface, and the oxygen concentration in the longitudinal direction of the silicon single crystal are controlled.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are cross-sectional view schematically showing a CZ furnace in which the apparatus required to execute the present invention are exemplified;

FIGS. 2A and 2B show delta V (the allowable range of the pulling speed of the silicon single crystal (mm/min)) under conditions where the height of the solid-liquid interface (mm) are shown on the horizontal axis, and the temperature gradient on the side surface of the crystal (degrees C./mm) are shown on the vertical axis;

FIGS. 3A to 3D each shows areas where kinds of defects are present at locations in the longitudinal direction of the silicon single crystal and at locations from the center;

FIG. 4 shows the pulling speeds at locations in the longitudinal direction of the silicon single crystal;

FIGS. 5A to 5C each shows areas where types of, defects are present at locations in the longitudinal direction of the silicon single crystal and at locations from the center;

FIG. 6 shows the pulling speed at locations in the longitudinal direction of the silicon single crystal;

FIGS. 7A and 7B show the height of the solid-liquid interface when the number of rotations of the crucible per unit time or the number of rotations of the silicon single crystal per unit time is changed;

FIG. 8 shows the oxygen concentration in the silicon single crystal at locations in the longitudinal direction of the silicon single crystal;

FIG. 9 shows the oxygen concentration in the silicon single crystal when the flow rate of inert gas and the inner pressure in the CZ furnace are changed;

FIGS. 10A and 10B show the change in the oxygen concentration in the longitudinal direction of the silicon single crystal and the change in the height of the solid-liquid interface in the case that the heater power ratio is changed;

FIG. 11 shows the change in the oxygen concentration in the silicon single crystal at a 400 mm location in the longitudinal direction of the silicon single crystal when the number of rotations of the crucible per unit time is changed;

FIGS. 12A and 12B show the number of rotations of the crucible per unit time (horizontal axis) and the heater power ratio (vertical axis), and the number of rotations of the crucible per unit time (horizontal axis) and the height of the solid-liquid interface (vertical axis), to obtain each oxygen concentration at a 400 mm location in the longitudinal direction of the silicon single crystal;

FIG. 13 shows the adjustment state of the heater power ratio at locations in the longitudinal direction of the silicon single crystal;

FIG. 14 shows the adjustment state of the distance between the heat shield plate and the molten silicon at locations in the longitudinal direction of the silicon single crystal;

FIG. 15 shows the adjustment state of the pulling speed of the silicon single crystal at locations in the longitudinal direction of the silicon single crystal;

FIG. 16 shows the change in the oxygen concentration in the silicon single crystal at locations in the longitudinal direction of the silicon single crystal;

FIG. 17 shows the defect distribution at locations in the longitudinal direction of the silicon single crystal evaluated by X-ray topography;

FIG. 18 shows the change in the height of the solid-liquid interface at locations in the longitudinal direction of the silicon single crystal;

FIG. 19 is a cross-sectional view schematically showing a conventional CZ furnace; and

FIG. 20 is a view explaining “the height of the solid-liquid interface”.

Claims

1. A method for manufacturing a defect-free silicon single crystal by the CZ method, comprising the steps of: disposing a cylindrical cooler around the silicon single crystal; andby adjusting a pulling speed of the silicon single crystal, a rotation speed of a crucible that stores molten silicon and a rotation speed of the silicon single crystal, and an output ratio of a multi-heater separated into at least two in the longitudinal direction of the silicon single crystal disposed around the crucible, controlling a temperature gradient on a side surface of the silicon single crystal in the longitudinal direction of the silicon single crystal, a height of a solid-liquid interface, and an oxygen concentration in the longitudinal direction of the silicon single crystal, to manufacture a defect-free silicon single crystal.

2. The method according to claim 1, wherein the multi-heater consists of an upper heater and a lower heater located below the upper heater, and the output ratio of the lower heater to the upper heater is set to 0.9 or more and 3.5 or less.

3. The method according to claim 1, wherein the multi-heater consists of a cylindrical side heater disposed around the crucible and a bottom heater disposed on a lower side of the crucible, and the output ratio of the bottom heater to the side heater is set to 0.9 or more and 3.5 or less.

4. The method according to claim 2, wherein the output ratio is set to 0.9 or more and 1.5 or less.

5. The method according to claim 3, wherein the output ratio is set to 0.9 or more and 1.5 or less.

6. The method according to claim 2, wherein the output ratio is changed and adjusted in the longitudinal direction of the silicon single crystal.

7. The method according to claim 1, wherein the rotation speed of the crucible is set to 0.5 rpm or more and 1 rpm or less.

8. The method according to claim 1, wherein the rotation speed of the silicon single crystal is set to 18 rpm or more and 20 rpm or less in a reverse direction of the rotation of the crucible.

9. The method according to claim 8, wherein the rotation speed of the silicon single crystal is set to 18 rpm or more and 20 rpm or less in a reverse direction of the rotation of the crucible.

10. The method according to claim 1, further comprising the step of: changing and adjusting a distance between the lower edge of a heat shield plate surrounding the silicon single crystal and adjusting an amount of radiant heat radiated onto the silicon single crystal and the surface of the molten silicon in the longitudinal direction of the silicon single crystal.

11. The method according to claim 10, wherein the distance between the lower edge of the heat shield plate and the surface of the molten silicon is adjusted in a range from 45 mm or more to 75 mm or less, and the pulling speed of the silicon single crystal is adjusted in a range from 0.45 mm/min or more to 0.70 mm/min or less.

12. The method according to claim 1, wherein a magnetic field is applied to the molten silicon.

13. A method for manufacturing a defect-free silicon single crystal by the CZ method, comprising the step of: by adjusting a pulling speed of the silicon single crystal, a rotation speed of a crucible that stores molten silicon and a rotation speed of the silicon single crystal, and an output ratio of a multi-heater separated into at least two in the longitudinal direction of the silicon single crystal disposed around the crucible, controlling a temperature gradient on the side surface of the silicon single crystal in the longitudinal direction of the silicon single crystal, a height of a solid-liquid interface, and an oxygen concentration in the longitudinal direction of the silicon single crystal, to manufacture a defect-free silicon single crystal.