JPH06135791A - Device for growing semiconductor single crystal - Google Patents

Abstract

PURPOSE:To make the dopant concn. uniform in the radial direction of a grown single crystal in the device by the Czochralski method by arranging >=2 inner crucibles having a different radius in an outer crucible and furnishing a circulating hole in the crucibles. CONSTITUTION:A triple inner crucible consisting of the first to third inner crucibles 2 to 4 is coaxially arranged in an outer crucible 1 supported by a susceptor 10, supported by a roatary rotating shaft 5 and rotated. Two communicating holes are formed in the crucible 2, four communicating holes are formed in the crucible 3, and eight communicating holes are formed in the crucible 4 at regular intervals. The communicating holes of the adjacent inner crucibles are arranged at the furthermost position from each other. When a raw powder 7 is supplied into an annular part between the outer crucible 1 and the inner crucible 2, the dopant eluted from the raw powder 7 flows almost uniformly into the inner crucible at the center. A single crystal 9 is pulled up from the molten material 8 having a uniform dopant element and grown to achieve the objective.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for growing a semiconductor single crystal by the Czochralski method while continuously supplying raw materials.

[0002]

2. Description of the Related Art A single crystal to be grown has a small amount of impurity element (dopant element) mixed in a raw material melt in order to be a P-type or N-type semiconductor according to the purpose. The segregation coefficients indicating the degree of inclusion in the grown single crystal are 0.8 and 0.0, respectively, in the case where the silicon single crystal is doped with boron, antimony, or phosphorus.
23 and 0.35 are both lower than 1. As a result, the impurity concentration changes in the upper part and the lower part of the grown crystal, and the electrical properties also change, which is not preferable for manufacturing a semiconductor element. Therefore, a portion of the grown crystal where the impurity concentration does not fall within a certain range becomes a defective product.

Therefore, in order to improve the yield of grown crystals, a continuous Czochralski method has been developed in which a single crystal is grown while continuously supplying a raw material. JP-A-52-58080
Japanese Unexamined Patent Publication (Kokai) No. Sho 59-59 discloses a method of supplying raw materials.
No. 79000 discloses a method in which a polycrystalline material to be additionally supplied is provided with holes or grooves, and a dopant material is enclosed therein. This method is not suitable for precise control of impurity concentration. Incidentally, the concentration of the impurity atom required here is usually about 0.1 to 10 ppma, and the allowable value of the concentration range is also a relatively narrow range of ± 10 to 20%.
Therefore, a well-measured trace amount of impurity elements must be quantitatively mixed in the melt.

Therefore, in comparison with a single crystal grown in advance,
A method has been proposed in which a semiconductor single crystal having an impurity concentration that is three orders of magnitude higher is manufactured and a single crystal master alloy obtained by cutting a rod-shaped or plate-shaped semiconductor single crystal out of the semiconductor single crystal is used. Since there are no grain boundaries in this single crystal master alloy, there is no segregation of impurities to the grain boundaries, and it is possible to obtain a single crystal master alloy that can be considered to be almost uniform. The measurement can be performed with sufficient accuracy. By additionally supplying this single crystal master alloy into the raw material melt, the impurity concentration in the melt can be held constant, and as a result, the impurity concentration of the pulled single crystal can be kept uniform. it can.

FIG. 4 is a conceptual diagram of a single crystal manufacturing apparatus using the above single crystal master alloy. Graphite susceptor 11
A quartz crucible 12 supported by an inner crucible 13 arranged coaxially with the quartz crucible 12 is provided to feed a single crystal master alloy 14 for doping to a raw material melt of an annular portion of the crucible 12. A support member 16 having a gripping chuck 15 at its lower end and capable of moving up and down, and a supply pipe 18 for supplying a granular raw material 17 are provided, and a raw material melt 19 adjusted by an annular portion of the crucible 12 is supplied to the inner crucible 13. One communication hole 20
The seed crystal is immersed in the raw material melt 19 which has been moved into the inner crucible 13 via the and is rotated and stirred by the rotary shaft 21, and the single crystal 22 is pulled while being rotated.

Hereinafter, the growth of a silicon single crystal will be described as an example. The quartz crucible 12 is filled with an initial raw material in which a predetermined proportion of an impurity element is mixed, and after the air in the furnace is replaced with argon gas, the inside of the furnace is heated by a resistance heater. After the initial raw material is completely melted, the calorific value of the heater is reduced to lower the temperature of the silicon melt 19 to a temperature suitable for single crystal growth. In this state, rotate the rotary shaft 21,
The seed crystal is lowered from above and immersed in the silicon melt 19 to pull up the single crystal 22. Supply pipe 18 during pulling up
In order to deal with the growth loss of the single crystal 22 by supplying the powdery raw material 17 from the single crystal master alloy 14 supported by the chuck 15, the single crystal master alloy 14 is lowered at a predetermined speed in the silicon melt of the annular portion of the crucible 12. Supply to.

Incidentally, when the impurity concentration is 1 ppma, the diameter is 80
mm pulling speed of 1m silicon single crystal rod 1m
It is pulled up and grown at m / min and has an impurity concentration of 56.
When a rectangular parallelepiped single crystal master alloy of 10 mm square and 120 mm in length is lowered at 0 ppma, the descending speed of the single crystal master alloy is as follows. 4 × 4 × 3.14 × 1 / (560 × 1 × 1) = 0.09
(Mm / min) The silicon melt in the annular portion of the crucible 12 is
Of the grown single crystal 22 through the through hole 20 of
Is stirred by convection caused by the rotation of, and the impurity concentration is made uniform.

[0008]

However, in the conventional apparatus shown in FIG. 4, since only one inner crucible 13 is used and one through hole 20 is provided in the crucible, the grown single crystal 22
Even if is rotated, as shown in FIG. 5, the dopant concentration in the raw material melt in the inner crucible is actually high near the through hole 20 and becomes lower as it goes away. Therefore, the dopant concentration in the radial direction of the obtained single crystal 22 could not be said to be uniform at all. Therefore, in the present invention,
An object of the present invention is to provide a device for growing a semiconductor single crystal, which can solve the above-mentioned drawbacks and make the dopant concentration in the radial direction of the grown single crystal uniform.

[0009]

According to the present invention, in an apparatus for growing a semiconductor single crystal by the Czochralski method, two or more inner crucibles having different radii are coaxially arranged in the crucible and the outermost inner crucible is arranged. 2 at equal intervals in the radial direction on the side of the crucible
One circulation hole is provided, the number of circulation holes is doubled as the inner crucible becomes inner, and the circulation holes of the adjacent inner crucibles are arranged at the farthest positions from each other, and the raw material supply means is provided to the outermost crucible. Is arranged and the semiconductor single crystal is pulled from the center of the crucible.

[0010]

FIG. 1 is a front sectional view of a semiconductor single crystal growing apparatus which is one embodiment of the present invention, and FIG. 2 is a plan view of FIG. The apparatus shown in FIG. 1 has a triple inner crucible consisting of a first inner crucible 2, a second inner crucible 3 and a third inner crucible 4 coaxially in the outer crucible 1 supported by the susceptor 10. It is arranged and rotatably supported by the rotating shaft 5. And
As shown in FIG. 2, the first inner crucible 2 has two communication holes, the second inner crucible 3 has four communication holes, and the third inner crucible 4 has eight communication holes at equal intervals. The positions of the communication holes of the inner crucibles adjacent to each other were arranged at positions most distant from each other as shown in the figure. The raw material powder 7 is fed from the raw material supply pipe 6 to the outer crucible 1.
The dopant that is supplied to the annular portion between the first inner crucible 2 and the first raw crucible 2 and begins to melt from the raw material powder 7 is
Since it diffuses and sequentially migrates into the inner crucible, a substantially uniform dopant element flows into the central inner crucible. Since the single crystal 9 is pulled up and grown from the raw material melt 8 having a uniform dopant element, it is possible to make the dopant concentration in the radial direction of the grown single crystal 9 uniform.

[0011]

EXAMPLE Using the apparatus of the present invention shown in FIGS. 1 and 2 and the conventional apparatus shown in FIG. 4, a diameter of 80 mm and a length of 20 under the following conditions.
A silicon single crystal doped with 0 mm of phosphorus was grown. Pulling speed 1 mm / hr Crystal rotation speed 5 rpm Crucible rotation speed 5 rpm Crucible material Quartz crucible inner diameter Conventional device 12 cm, 20 cm (double crucible) Device of the present invention 12 cm, 16 cm, 20 cm
(Triple crucible) Crucible wall thickness 3mm Inner crucible through hole diameter 5mm

A single crystal was grown for each run on both devices. When the variation in the specific resistance in the radial direction of the obtained single crystal was investigated, the single crystal obtained by the conventional apparatus was 10 to 20%, whereas the single crystal obtained by the apparatus of the present invention was 3 to 7%. And showed an extremely low value. The following equation was used as an equation indicating the degree of variation. K = [(C _max −C _min ) / C _av ] × 100 (%) C _max : maximum value of specific resistance in a certain radial direction C _min : minimum value of specific resistance in a certain radial direction C _av : certain diameter Mean value of resistivity in the direction

[0013]

According to the present invention, by adopting the above structure, it is possible to grow a semiconductor single crystal having a uniform dopant concentration in the radial direction and to improve the yield in the production of semiconductor devices.

[Brief description of drawings]

FIG. 1 is a front cross-sectional view of a semiconductor single crystal growth device that is one specific example of the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is a diagram for explaining a diffusion path of a dopant in the device of FIG.

FIG. 4 is a front sectional view of a conventional semiconductor single crystal growing device.

5 is a diagram showing a dopant concentration gradient of a raw material melt in an inner crucible in the apparatus of FIG.

Claims (1)

[Claims] 1. An apparatus for growing a semiconductor single crystal by the Czochralski method, in which two or more inner crucibles having different radii are coaxially arranged in the crucible, and the inner crucible on the outermost side is radially aligned. Two circulation holes are provided at intervals, the number of circulation holes is doubled as the inner crucible becomes inner, and the circulation holes of adjacent inner crucibles are arranged at the farthest positions from each other, and the outer crucible is arranged at the outermost crucible. Arrange the raw material supply means,
An apparatus for growing a semiconductor single crystal, wherein the semiconductor single crystal is pulled from the center of the crucible.