JP3099403B2 - Single crystal manufacturing method and single crystal manufacturing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a single crystal such as a silicon single crystal and an apparatus used for the method.

[0002]

2. Description of the Related Art A Czochralski (CZ) method is widely known as a method for producing a single crystal. FIG. 4 is a schematic diagram showing an embodiment of a conventional single crystal production by the CZ method. In FIG. 4, reference numeral 4 denotes a quartz crucible. A carbon crucible 5 is provided on the outer periphery of the quartz crucible 4, and a carbon crucible 5 is further provided on the outer periphery thereof.
A heater 7 made of carbon is arranged so as to surround the whole. Then, a crystal raw material is charged into the quartz crucible 4 and heated and melted by the heater 7. Then, the seed crystal 2 suspended by the pulling shaft 1 is immersed in the molten liquid 6, and rotated while rotating. When pulled upward, the single crystal 3
Is grown.

[0003]

In the single crystal growing apparatus constructed as described above, the heat escapes at the upper and lower ends of the heater 7 and does not escape at the center in the vertical direction. The calorific value is in the center as shown by the broken line,
That is, a peak is reached at a position slightly below the liquid level of the melt 6. Due to this heat distribution, a heat convection is generated from the central portion of the side peripheral wall of the quartz crucible 4 toward the pulling region of the single crystal 3 as indicated by an arrow. Then, the quartz crucible 4 is melted by the heating of the heater 7, oxygen is supplied into the melt 6, and the oxygen is taken into the pulling region of the single crystal 3 by the thermal convection, and oxygen is taken into the single crystal 3. Therefore, in this apparatus, since the amount of oxygen supplied to the single crystal 3 is large, approximately 13.0 × 10 ¹⁸ atms / cc
It was impossible to produce a single crystal having the following low oxygen concentration.

Therefore, a heater 7 is provided with a quartz crucible 4 at its center.
When the heat generated by the heater 7 reaches a peak above the liquid surface of the molten liquid 6, the heat flowing from the side peripheral wall of the quartz crucible 4 to the pulling region of the single crystal 3 is increased. The convection is reduced, the amount of oxygen dissolved from the quartz crucible 4 is reduced, the amount of oxygen supplied to the single crystal 3 is reduced, and a single crystal having a low oxygen concentration can be manufactured.
However, the amount of heating in the pulling region of the single crystal 3 increases, and the pulling speed must be reduced in order to continue pulling the single crystal 3, and there is a problem that dislocation of the single crystal 3 accompanies. Was.

The present invention has been made in view of such circumstances, and reduces the amount of oxygen dissolved into the melt from the side peripheral wall of the crucible so that the peak of the heat generation distribution of the heater is located above the liquid level of the melt. By reducing the amount of oxygen supplied to the single crystal pulling region, a single crystal with low oxygen concentration can be obtained without lowering the pulling rate than before and without dislocation of the single crystal. An object of the present invention is to provide a single crystal manufacturing method and a single crystal manufacturing apparatus used for the method.

[0006]

According to a first aspect of the present invention, there is provided a method for producing a single crystal, comprising melting a raw material for crystallization in a crucible with a heater arranged around the single crystal, and then supplying the single crystal from the melt without supplying the raw material for crystallization. In the method for producing a single crystal, a single crystal is produced such that the peak of the heat generation distribution of the heater is positioned above the liquid level of the melt. A single crystal manufacturing apparatus according to a second aspect of the present invention is a single crystal manufacturing apparatus in which a crystal raw material is melted in a crucible around which a heater is disposed, and a single crystal is pulled from a melt and grown. In the middle part where the thickness of the heater faces the liquid surface so that is located above the liquid surface of the melt.
Thinnest, thickest at bottom, thicker at top than middle
Ku is characterized in that are.

[0007]

In the present invention, since the peak of the heat generation distribution of the heater is located above the liquid level of the molten liquid,
Unlike the case where the peak of the heat generation distribution of the heater is located below the liquid level of the melt, the heat convection generated in the melt is of a small scale only toward the pulling region of the single crystal from the upper side peripheral wall of the crucible, Also, the amount of oxygen that dissolves into the melt from the side peripheral wall of the crucible is small. Therefore, the amount of oxygen supplied to the single crystal pulling region is reduced, and a single crystal having a low oxygen concentration can be manufactured. The amount of heating in the single crystal pulling region is smaller than when the heater is arranged high so that the central portion thereof substantially coincides with the upper end position of the quartz crucible, so that pulling can be performed without reducing the pulling speed. Also, it does not involve dislocation of the single crystal.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a schematic longitudinal sectional view of a single crystal manufacturing apparatus according to the present invention. In the figure, reference numeral 4 denotes a quartz crucible.
A carbon crucible 5 is disposed on the outer periphery of the quartz crucible 4, and a carbon heater 8 is disposed on the outer peripheral side so as to surround the carbon crucible 5. And quartz crucible 4
The raw material for crystal is put into the furnace, and the raw material is heated and melted by the heater 8. Then, the seed crystal 2 suspended by the pulling shaft 1 is immersed in the molten liquid 6, and the seed crystal 2 is pulled upward while rotating. The single crystal 3 is grown at the lower end of the seed crystal 2.

FIG. 2 is a perspective view of the heater 8. Heater 8
Have upper slits 8b, 8b,
8b,... And lower slits 8c, 8 cut from the lower end
are alternately provided in the circumferential direction. At the lower end of the heater 8, the electrodes 8a, 8a are separated by 180 ° in the circumferential direction.
Are provided, so that electricity is supplied. When energized, a current flows through the heater 8 while changing its direction in the vertical direction as indicated by the arrow. The thickness of the heater 8 is
It differs between the middle and lower three stages. The thickness t _{2 of the} middle portion is approximately の of the thickness t ₃ of the lower portion, and the thickness t _{1 of the} upper portion is slightly larger than the thickness t _{2 of the} middle portion. And the length l of the upper part
₁ , the ratio of the length l ₂ of the middle part to the length l ₃ of the lower part is approximately 1:
2: 5.

The resistance is inversely proportional to the thickness of the resistor, that is, the cross-sectional area, and the calorific value is proportional to the resistance. As described above, since the thickness of the upper portion and the middle portion of the heater 8 is made smaller than that of the lower portion, the calorific value of the upper portion and the middle portion is larger than that of the lower portion. Therefore, when the liquid level of the melt 6 is positioned slightly below the center of the middle portion of the heater 8, the heat generated by the heater 8 is substantially at the center of the middle portion as shown by the broken line, that is, the liquid level of the melt 6 The peak is reached slightly higher. Due to this heat distribution, the single crystal 3 is pulled from the upper side wall of the quartz crucible 4, unlike the case where the peak of the heat distribution of the heater is located below the liquid level of the melt, as indicated by the arrow in the melt 6. Small-scale heat convection only to the region occurs. The amount of the quartz crucible 4 that is melted by the heating of the heater 8 is small. Therefore, the amount of oxygen carried from the side peripheral wall of the quartz crucible 4 to the pulling region of the single crystal 3 by the heat convection is small, and as a result, the oxygen concentration of the single crystal 3 can be reduced.

FIG. 3 is a graph showing the relationship between the pulling length and the oxygen concentration when the position of the exothermic peak is changed. In the figure, □ indicates an example of the present invention in which the exothermic peak is on the liquid level of the molten liquid 6, and Δ
Is a comparative example in which the exothermic peak is at the same position as the liquid level of the molten liquid 6,
○ is a conventional example in which the exothermic peak is below the liquid level of the melt 6. From FIG. 3, according to the method of the present invention, 7.0 to 13.0 × 1.
It is understood that a single crystal having a low oxygen concentration of about ¹⁸ atms / cc can be manufactured.

[0012]

[0013]

As described above, according to the present invention, the peak of the heat generation distribution of the heater is positioned above the liquid level of the melt, and the amount of oxygen dissolved into the melt from the side peripheral wall of the crucible is reduced. The amount of oxygen supplied to the single crystal pulling region is reduced, and a single crystal having a low oxygen concentration can be obtained.
Since the amount of heating above the pulling region of the single crystal is smaller than when the heater is displaced above the crucible, there is no need to lower the pulling speed, and there is no accompanying dislocation of the single crystal. The present invention has excellent effects.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a single crystal manufacturing apparatus according to the present invention.

FIG. 2 is a perspective view of a heater.

FIG. 3 is a graph showing a relationship between a pulling length and an oxygen concentration when a position of an exothermic peak is changed.

FIG. 4 is a schematic longitudinal sectional view of a conventional single crystal manufacturing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pulling shaft 2 Seed crystal 3 Single crystal 4 Quartz crucible 5 Carbon crucible 6 Melt 8 Heater

Continuation of the front page (72) Inventor Norihito Harai 1 in Higashihama-cho, Amagasaki City, Hyogo Prefecture Inside Osaka Titanium Manufacturing Co., Ltd. (56) References JP-A-2-172885 (JP, A) (58) .Cl. ⁷ , DB name) C30B 1/00-35/00

Claims (2)

(57) [Claims] A method for producing a single crystal, comprising melting a raw material for crystal in a crucible with a heater arranged around and then pulling a single crystal from the melt without supplying the raw material for crystal.
A single crystal manufacturing method, wherein a single crystal is manufactured such that a peak of a heat generation distribution of the heater is located above a liquid level of the melt. 2. A single crystal manufacturing apparatus for melting a crystal raw material in a crucible having a heater disposed therearound and pulling a single crystal from the melt to grow the same, the peak of the heat generation distribution of the heater being the peak of the melt. so as to be positioned above the liquid surface, before
The thickness of the heater is the thinnest in the middle where the thickness of the heater faces the liquid surface.
An apparatus for producing a single crystal, characterized in that the step is the thickest, and the upper part is thicker than the middle part .