JP2555714B2 - Semiconductor single crystal growth equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a semiconductor single crystal growth apparatus for growing a single crystal by using a double-structured crucible, and particularly, it relates to a carbon compound discharge property in the vicinity of a melt. Concerning improvements to enhance.

[Prior Art] When a silicon single crystal to which a dopant such as B, P, Sb, etc. is added by the CZ method is manufactured, the segregation coefficient of these dopant atoms is not 1, so that the dopant concentration in the grown single crystal is low. There is a problem in that it becomes non-uniform in the longitudinal direction, and only a part thereof has a desired quality.

As measures for improving it, JP 49-10664 A and USP 4352
In No. 784, a double crucible composed of an outer crucible body and an inner crucible body is used, and the dopant concentration difference in the raw material melt divided by each crucible is utilized to substantially uniformize the dopant concentration in the single crystal, Techniques for improving yield have been disclosed. FIG. 9 shows an example of the apparatus. Reference numeral 1 is a furnace body, 2 is a double crucible in which a cylindrical inner crucible body 2B is housed in an outer crucible body 2A, 3 is a graphite susceptor, 4 is a heater, and 5 is a heat retaining cylinder. so,
Argon gas is supplied into the furnace body 1 from the gas introduction port 6, and is discharged from the gas discharge port 7 together with impurities generated from the raw material melt Y.

[Problems to be solved by the invention] However, when a silicon single crystal is actually manufactured by an apparatus equipped with this kind of double crucible, the carbon concentration in the obtained single crystal gradually increases from the growth start side to the end side. However, it has been often confirmed that the carbon concentration that can be used as a semiconductor element partially exceeds the standard, which deteriorates the yield of single crystals.

This kind of carbon contamination originates from various graphite parts (heater 4, heat retaining cylinder 5, susceptor 3, support for inner crucible body 2B, etc.) used in the furnace.
And quartz crucible 2 generate volatile SiO,
This SiO is on the surface of the graphite component at high temperature as follows:
Generate O.

SiO + 2C → SiO + CO Therefore, if carbon contamination is more remarkable in the double crucible than in the single crucible, in the case of the double crucible,
It is expected that there is some mechanism for dissolving more generated CO in the raw material melt Y.

Therefore, the present inventors have made detailed studies on the behavior of CO gas, and have obtained the following findings. That is, the argon gas supplied from the gas introduction port 6 flows downward along the single crystal T, passes through the gap between the inner crucible body 2B and the single crystal T, and then rises above the inner crucible body 2B and the outer crucible body 2A. And is discharged from the gas discharge port 7. At that time, the inner crucible body
As shown in the figure, the gas stays in the gap between the 2B and the outer crucible body 2A for a relatively long time, the CO concentration in the gas rises, and the CO continuously contacts the melt Y, so that the CO can be efficiently contacted. It melts into the melt Y, and the melt Y and eventually the CO of the single crystal T
It increases the concentration.

As a measure for remedying this phenomenon, it is conceivable to first increase the flow rate of argon gas supplied into the furnace body 1. In this case, the cost required for gas supply is significantly increased, and the growth condition of the single crystal T is affected. The negative effects cannot be ignored.

"Means for solving the problems" The present invention has been made to solve the above problems,
A cylindrical gas rectifying cylinder is provided above the double crucible coaxially with the double crucible, and a lower end portion of the gas rectifying cylinder is arranged in a gap between the inner crucible body and the outer crucible body. It is characterized in that a space is provided between the outer crucible and the raw material melt.

The maximum thickness of the lower end portion of the gas flow straightening cylinder is 0.3 to 0.8 times the distance between the inner crucible body and the outer crucible body, and the surface of the lower end portion of the gas flow straightening cylinder is preferably a gently curved surface. . Also, the distance between the lower end of the gas flow straightener and the raw material melt is 5 m.
It is desirable that the lower end is larger than m and the lower end is lower than the upper end of the outer crucible body.

Further, between the inner crucible body and the single crystal, a cylindrical cylindrical body is coaxially arranged so that the lower end of the inner crucible body is separated from the inner crucible body, the melt, and the single crystal. You may comprise so that an inert gas may be supplied.

[Operation] In this semiconductor single crystal growth system, by arranging a gas rectifying tube in the gap between the inner crucible body and the outer crucible body, the argon gas supplied from above the furnace body into the furnace crucible And the gas flow straightening tube, the gas flow straightening tube and the raw material melt, and the gap between the outer crucible body and the gas flow straightening tube so as to flow in a laminar flow, in the gap between the inner crucible body and the outer crucible body. Prevents gas retention and reduces CO penetration into the raw material melt.

Further, when a cylindrical tubular body is coaxially arranged between the inner crucible body and the single crystal, it is possible to prevent gas retention in the gap between the single crystal and the inner crucible body.

Embodiments FIGS. 1 and 2 show one embodiment of a semiconductor single crystal growing apparatus according to the present invention.

Reference numeral 10 in the figure is a furnace body composed of an upper body 10A and a lower body 10B,
A lower shaft 11 that moves up and down and rotates is disposed at the center of the furnace body 10. A double crucible 13 made of quartz is fixed to the upper end of the lower shaft 11 via a graphite susceptor 12. Also, the susceptor
A heater 14 and a heat insulating cylinder 15 are arranged in this order around the outer circumference of 12.

The double crucible 13 has a bottomed cylindrical outer crucible body 13A.
And a cylindrical inner crucible body 13B coaxially disposed therein.
A through hole (not shown) is formed at the lower end of the inner crucible body 13B. Further, above the furnace body 10, a wire 17 holding the seed crystal 16 is moved up and down to rotate, and the inner crucible body is
A pulling mechanism (not shown) for growing the single crystal T from the inside of 13B is provided.

A cylindrical portion 19A and an annular plate portion 1 formed integrally with the upper end of the cylindrical portion 19A are attached to the upper end of the heat insulating cylinder 15 via an annular plate-shaped mounting plate 18.
A gas rectifying cylinder 19 including 9B is fixed. The lower end of the cylindrical portion 19A of the gas flow straightening cylinder 19 is inserted into the gap between the inner crucible body 13B and the outer crucible body 13A, and the lower end and the inner crucible 1
3B, the raw material melt Y, and the outer crucible body 13A are provided with substantially the same gaps. Specifically, as shown in FIG. 2, the distance between the lower end of the gas rectifying cylinder 19 and the melt Y is larger than 5 mm, and the lower end is set lower than the upper end of the outer crucible body 13A. If the distance from the melt Y is less than 5 mm, the flow rate of the argon gas passing through this gap becomes excessive,
In addition to causing unnecessary vibration in the melt Y,
The gas rectifying cylinder 19 may come into contact with the melt Y. Also,
If the lower end of the gas rectifying cylinder 19 is located at a position higher than the upper end of the outer crucible body 13A, the rectifying effect cannot be obtained and CO infiltration into the melt Y cannot be reduced. Moreover, as shown in FIG.
The wall thickness P of the lower end portion of 19 is the inner crucible body 13B and the outer crucible body 13B.
It is desirable that the distance Q from the distance is 0.3 to 0.8. 0.3
If it is less than twice, the gas tends to stay near the inner crucible body 13B and the outer crucible body 13A, and the rectifying effect is weakened. On the other hand, if it is greater than 0.8 times, there is a risk of interference with the crucible bodies 13A and 13B.

As the material of the gas rectifying cylinder 19, a single material or a composite material of high heat resistant material such as Mo, Ta, W, C, or SiC is suitable, and if necessary,
A coating layer such as SiC may be further formed. Furnace body 10
A raw material supply pipe 20 for supplying a raw material to the gap between the inner crucible body 13B and the outer crucible body 13A is provided inside the annular plate portion 19 of the gas rectifying cylinder 19.
It penetrates B and is fixed along the outer surface of the cylindrical portion 19A. The raw material supply pipe 20 may be formed by forming a slit in the cylindrical portion 19A and fixing the slit therein, or may be arranged along the inner surface of the cylindrical portion 19A. Further, 21 is a gas inlet, and 22 is a gas outlet.

In order to use this semiconductor single crystal growing apparatus, first, the silicon crucible 13 is filled with silicon raw material, the heater 14 is energized, and argon gas is supplied from the gas inlet 21 to melt the raw material. Then, the double crucible 13 is raised to adjust the distance to the gas rectifying cylinder 19 to an optimum value, the seed crystal 16 is immersed in the melt Y to grow the single crystal T, and the raw material supply pipe 20
The raw material is supplied to the crucible 13 through to compensate for the decrease in the melt. At this time, the melt and the crucible react to generate SiO,
Further, a part of this SiO reacts with the graphite parts in the furnace body 10 to generate CO.

On the other hand, the argon gas supplied from the gas inlet 21 is
All are focused on the cylindrical portion 19A by the annular plate portion 19B of the gas rectifying cylinder 19 and descend along the single crystal T, between the inner crucible body 13B and the cylindrical portion 19A, between the cylindrical portion 19A and the melt Y, and between the cylindrical portion 19A. The gas is discharged from the gas discharge port 22 by rapidly passing between the portion 19A and the outer crucible body 13A without any delay. As a result, the SiO and CO
Since it is discharged without staying in the gap between the outer crucible body 13A and the inner crucible body 13B, the total amount of CO dissolved in the melt is remarkably reduced as compared with the conventional apparatus, and a high-quality single crystal T with a low carbon concentration is produced. It is possible to manufacture.

In addition, in the above embodiment, the lower end of the gas flow straightening cylinder 19 is square, but as shown in FIG.
As shown in FIG. 4, a thick bulge portion 23 may be formed at the lower end, and the entire surface thereof may be curved. The dimensions and the like of each part are the same as those in the above embodiment. With this configuration, the gas flow passing near the lower end of the cylindrical portion 19A is less likely to have a vortex, and the above effect can be further enhanced. In addition, a configuration (batch type) in which the raw material supply pipe 20 is not provided is also possible. In that case, the crucible is raised as the melt Y decreases and the gap between the melt Y and the gas rectifying cylinder 19 is kept constant.

Next, FIG. 5 shows another embodiment of the present invention. In this embodiment, in addition to the configuration of the above embodiment, the annular plate portion 19 of the gas rectifying cylinder 19 is added.
It is characterized in that B is extended inward in the radial direction, and a cylindrical body 31 that hangs down from the inner edge of the extension portion 30 is coaxially provided. The lower end of the cylindrical body 31 is inserted into the gap between the single crystal T and the inner crucible body 13B, and the lower end portion, the single crystal T, the melt Y, and the inner crucible body 13B.
And substantially the same interval is formed between the two. The distance between the lower end and the melt Y is 5 mm or more, and the position of the lower end is set lower than the upper end of the inner crucible body 13B. This is for the same reason as in the case of the gas flow straightening cylinder 19.

According to this example, first, the supplied argon gas is sequentially layered between the lower end of the tubular body 31 and the single crystal T, between the tubular body 31 and the melt Y, and between the tubular body 31 and the inner crucible body 13B. Since it flows as a flow, in addition to the gap between the inner crucible body 13B and the outer crucible body 13A, retention in the gap between the single crystal T and the inner crucible body 13B can be prevented, and the carbon concentration of the single crystal T can be reduced. It can be further reduced.

The laminar flow effect can be further increased by rounding the lower end of the cylindrical body 31 into a round shape, as in the case of the gas rectifying cylinder. Further, without providing the extension portion 30, the cylindrical body 31 may be formed into a conical shape so as to be constricted downward as shown by the two-dot chain line (a) in FIG. 5, or as shown by the two-dot chain line (b). It is also possible to move the cylinder downward to shorten the cylinder 31, or to form a ventilation hole in the extension portion 30 so that a part of the argon gas is passed between the gas rectifying cylinder 19 and the cylinder 31 and the gas in this portion is You may prevent retention. Furthermore, as shown in FIG. 6, it is possible to extend the cylinder body 31 directly from the gas introduction port 21 to the inside of the inner crucible body 13B.

"Experimental Example" Next, the effects of the present invention will be demonstrated with reference to Examples.

Using the apparatus shown in FIG. 1, a single crystal having a total length of 700 mm was prepared under the following growth conditions.

Inner diameter of outer crucible: 334 mm Outer diameter of inner crucible: 252 mm Initial filling amount of raw material: 20 kg Depth of initial melt: 110 mm Outer diameter of single crystal: 104 mm Height of outer crucible and inner crucible from melt Both: 120mm Gas rectifier outer diameter: 320mm Gas rectifier wall thickness (constant): 20mm Height of gas rectifier from melt: 10mm Distance from inner crucible of gas rectifier: 14mm Gas rectifier Distance from the outer crucible: 7 mm Argon gas supply rate: 50 / min (normal pressure) Raw material supply to the crucible: None (batch method) On the other hand, the gas rectifier was removed from the above equipment to produce exactly the same growth The single crystal was pulled up under the conditions.

Similarly, while supplying the raw material using the raw material supply pipe, a single crystal was produced under the same conditions as described above in the case of using the gas rectifying cylinder and the case of not using the gas rectifying cylinder. However, the length of each single crystal was 1000 mm.

With respect to the four single crystals thus obtained, the carbon concentration was measured at multiple points in the longitudinal direction using an IR measurement device (carbon detection limit: 0.1 × 10 ¹⁷ atoms / cm ³ ).

The results are shown in FIG. 7 (in the case of the batch method) and FIG. 8 (in the case of additionally supplying the raw material). As is clear from these graphs, the carbon concentration gradually increases with the growth when there is no gas rectifying cylinder, whereas the carbon concentration in most of the entire length increases when the gas rectifying cylinder is used. It was suppressed below the detection limit.

"Effects of the Invention" As described above, according to the semiconductor single crystal growth apparatus of the present invention, the argon gas supplied into the furnace body from above the furnace body is the gap between the inner crucible body and the gas rectifying cylinder, and the gas. Since it flows quickly in a laminar flow through the gap between the flow straightening cylinder and the raw material melt, and the gap between the outer crucible body and the gas flow straightening cylinder, gas retention does not occur in the gap between the inner crucible body and the outer crucible body, and the raw material melt To liquid
CO penetration can be reduced. This allows SiO and CO
Since impurities such as are discharged without staying in the gap between the outer crucible body and the inner crucible body, the total amount of CO that dissolves in the melt is significantly reduced compared to conventional equipment, and high-quality single crystals with low carbon concentration are manufactured. It is possible to

Further, when the cylindrical body is arranged between the inner crucible body and the single crystal, gas retention in the gap between the single crystal and the inner crucible body is prevented, and the carbon concentration can be further reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of a semiconductor single crystal growing apparatus according to the present invention, FIG. 2 is a vertical sectional view of a main part of the apparatus, and FIGS. 3 and 4 show other portions of the present invention. FIGS. 5 and 6 are longitudinal sectional views of a main part of the embodiment, FIGS. 5 and 6 are longitudinal sectional views of still another embodiment, and FIGS. 7 and 8 are graphs showing the effects of the experimental examples of the present invention. On the other hand, FIG. 9 is a vertical sectional view of a conventional semiconductor single crystal growing apparatus. T: single crystal, Y: raw material melt, 10: furnace body, 13: 2
Heavy crucible, 13A …… Outer crucible body, 13B …… Inner crucible body, 19
...... Gas rectifying cylinder, 20 …… Raw material supply pipe, 21 …… Gas inlet, 22 …… Gas outlet, 31 …… Cylinder.

Claims (5)

(57) [Claims] 1. A semiconductor single crystal growing apparatus for providing a double crucible composed of an inner crucible body and an outer crucible body in a furnace body and pulling and growing a single crystal from the inner side of the inner crucible body. , A cylindrical gas rectifying cylinder is provided coaxially therewith, the lower end of the gas rectifying cylinder is disposed in the gap between the inner crucible body and the outer crucible body, and the lower end portion, the inner crucible body, the outer crucible body, and the raw material An apparatus for growing a semiconductor single crystal, characterized in that a space is provided between the melt and the melt. 2. The semiconductor single crystal growing apparatus according to claim 1, wherein the maximum thickness of the lower end portion of the gas flow straightening cylinder is 0.3 to 0.8 times the distance between the inner crucible body and the outer crucible body. . 3. The semiconductor single crystal growing apparatus according to claim 1 or 2, wherein the surface of the lower end portion of the gas rectifying cylinder has a gentle curved surface. 4. The first or second aspect, wherein the distance between the lower end of the gas flow straightening cylinder and the raw material melt is greater than 5 mm, and the lower end is lower than the upper end of the outer crucible body.
Item 6. A semiconductor single crystal growth device according to item 3 or item 3. 5. A cylindrical tubular body is coaxially arranged between the inner crucible body and the single crystal such that the lower end portions thereof are separated from the inner crucible body, the melt and the single crystal, respectively. An inert gas is supplied from above through the body, so that the first, second, third, or fourth term
The semiconductor single crystal growth apparatus according to the item.