JPH02180791A - Single crystal pulling up device - Google Patents

Abstract

PURPOSE:To make uniform dopant concn. over the entire length of a single crystal in a Czochralski method by providing a prescribed upright partition cylinder between the inner wall of a crucible and the single crystal and allowing the floating of this cylinder in the molten material in the crucible. CONSTITUTION:The molten material 3 is housed in the crucible 2 in the Czochralski method. The upright partition cylinder 1 having plural projections 4 on the outer periphery is provided between the inner wall of the crucible 2 and the single crystal 13. The cylinder 1 floats on the molten material 3 coaxially with the perpendicular axis of the crucible 2. In addition, the top end of the cylinder 1 projects from the surface of the molten material 3. The above-mentioned plural projections 4a have a spiral vane shape.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application 1] The present invention relates to an apparatus for pulling a single crystal of a semiconductor such as Si or GaAs or an inorganic compound by the Czochralski method.

[Prior art] In crystal growth by the Czochralski method, for example, P
When a doped Si single crystal is grown, it is concentrated into the PtJS melt, so the P concentration at the bottom of the single crystal is higher than at the top. In order to make such a dopant concentration distribution uniform in the length direction of a single crystal, a method of additionally supplying raw materials in parallel with crystal growth has been conventionally used.

Additional supply of raw materials is carried out in the following manner.

When W is the weight of the melt at the start of crystal growth, Go is the dopant concentration in the melt, and k is the segregation coefficient of the dopant, the dopant concentration C in the melt after crystal growth by 1 weight ΔW is given by the following.

From equation (1), in order to maintain C=Co, it is only necessary to add ΔW of raw material having a concentration of k・C, to −C,, ΔW
Since it is also known as -C.

It is sufficient to prepare in advance a raw material having a dopant concentration of , and continuously supply the same weight as the pulling weight ΔW of the crystal. In this case, the amount of melt is always kept at a constant amount W. Alternatively, if we keep the dopant concentration in the melt constant Go by supplying a weight A of raw materials that do not contain dopants, (
From equation 1), A=(1-k)ΔW.

Therefore, the raw material not containing the dopant may be continuously supplied in increments of (1-k)ΔW. Since k<1 normally,
In this case, the feed rate is less than the crystal pulling weight, so the amount of melt gradually decreases.

At this time, a cylindrical partition may be used to prevent the crystal structure of the growing crystal from being disturbed by vibrations of the melt that occur when additional raw materials are supplied. As such a method, as disclosed in Japanese Patent Application Laid-open No. 62-278188, a double crucible having a notch 14 whose partial vertical cross-sectional view is shown in FIG. 4 is used to supply the raw material outside the partition cylinder l. A method is known in which the crystal growing portion is separated from the portion inside the partition cylinder l in which the crystal is grown. However, in this conventional method, the notch 1
The shape and number of 4 control the stirring of the melt between the outside and inside of the partition cylinder l.

In a method that uses a partition cylinder with a notch, the part where the raw material is additionally supplied and the part where the crystals are grown are simply connected through the notch. Therefore, there was a problem in that the melt between the part where the raw material was additionally supplied and the part where the crystals were grown was not sufficiently stirred, resulting in a dopant concentration distribution.

In addition, because the shape and number of notches change the stirring of the melt between the outside and the inside of the partition cylinder, there is also the problem that the shape and number of notches must be determined by trial and error in order to obtain the appropriate stirring situation. Ta. Furthermore, there were other problems, such as the fact that the crucible had a complicated shape, making the manufacturing cost of the crucible high, and that when the temperature of the melt changed, the depth from the melt surface to the notch also changed, causing changes in stirring.

Issue 81 to be Solved by the Invention The present invention partitions off a portion for additionally supplying raw materials and a portion for growing crystals by an inexpensive means.

This is to always create the same stirring state of the melt and make the concentration of the melt uniform.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention provides an apparatus for pulling a single crystal from a molten substance. It floats in the substance and has multiple protrusions on the outer periphery,
The present invention provides a single crystal pulling device characterized in that it is equipped with an upright partition cylinder whose upper end protrudes upward from the surface of the molten material, and a swirling vane-like projection of the same shape is preferably used as the projection. .

[Effect]

The present invention will be explained using the drawings. FIG. 1 is a schematic vertical cross-sectional view of an embodiment of the present invention, in which a melt 3 is accommodated in a crucible 2, and an upright partition cylinder 1 is provided with its upper end protruding upward from the surface of the melt 3, and the melt is A plurality of protrusions 4 are attached to the outer periphery of the partition cylinder l so that the vertical axis of the crucible 2 and the vertical axis of the partition cylinder l do not deviate from each other. If the protrusions 4 are, for example, a plurality of swirling vane-like protrusions of the same shape as shown in a perspective view in FIG. The flow of the melt 3 induced by the rotation causes the partition cylinder l to rotate, improving the stirring of the melt 3.

The raw material 6 is supplied to the gap between the crucible 2 and the partition cylinder l using the raw material supply pipe 5.

Since the partition cylinder l is not fixed to the crucible 2 and is attached to the melt 3, even if the depth of the melt 3 changes, the relative position between the partition cylinder l and the top surface of the melt 3 can be kept constant. .

[Example] A single crystal was grown by adding P as a dopant to Si using an apparatus whose vertical cross-sectional schematic diagram is shown in FIG. Single crystal 1
3 has a diameter of approximately 155 mm, and partition cylinder 1 has an inner diameter of 400 mm.
A material with a thickness of 5 mm and a thickness of 5 mm was used. The inner diameter of crucible 2 is 450 mm.

Both the partition cylinder 1 and the crucible 2 were made of quartz glass. The specific gravity of the quartz glass used is 2.2, and the specific gravity of the molten Si melt 3 is approximately 2.5, so the partition cylinder 1 is floating in the melt 3.

The vertical axis of the crucible 2 and the vertical axis of the partition cylinder l do not deviate significantly due to the protrusion 4, and the length of the partition cylinder l is 100 m.
m, and the part protruding above the surface of melt 3 is about 10 mm.
I made it so that

The raw material 6 was additionally supplied to the 20 mm gap between the partition cylinder l and the crucible 2 using the raw material supplying vibrator 5.

In this example, two single crystals were drawn in succession. The first crystal is pulled at a dopant concentration of 1.5x l O1
The experiment was carried out while continuously supplying 5 atoms/crn' of the raw material in an amount equal to the weight of the crystal to be pulled. During this time Melt 3 lf
f1 was constant. Subsequently, for the second crystal pulling,
The raw material containing no dopant was continuously supplied at a rate of 0.65 ΔW (ΔW is 1 crystal pulling side per unit time).

The relationship between the length of the obtained single crystal ingot and the P concentration is
In the 0 diagram shown in the figure, a is the 0th one of the 1st book of E, and b is the 0th one of the 1st book of Eki.
Honestly, it's zero.

Note that C and d are single crystal E-drawn using the crucible whose partial longitudinal section is shown in Fig. 4;
is a comparative example in which no raw material was added, and d was a comparative example in which a raw material was added.

Compared to conventional devices, by using the device of the present invention,
The Pa degree was uniform over the entire length of the ingot and could be kept within the target range.

[Effects of the Invention] The apparatus of the present invention has a simple structure and uses an inexpensive crucible, and can draw a single crystal with a uniform dopant concentration within the target range over the entire length of the ingot, making it economical. Highly effective.

[Brief explanation of the drawing]

Fig. 1 is a schematic longitudinal cross-sectional view of an embodiment of the device of the present invention, Fig. 2 is a perspective view of an upright partition cylinder equipped with a swirling vane-like protrusion, and Fig. 3 shows the relationship between the longitudinal distance of the ingot and the degree of Pa. diagram showing,
FIG. 4 is a partially vertical cross-sectional explanatory view of a crucible of a conventional device. l・-Upright partition cylinder 2...-Quartz crucible 3...Melt 4...Protrusion 4a-...Swivel vane-like projection 5...Vibro for raw material supply...Raw material 7...Raw material supply device 8...Graphite crucible 9...Heater lO...Insulating material 11...Casing 12...Crucible holding shaft 13...Single crystal 14...Notch

Claims (1)

[Scope of Claims] 1. In an apparatus for pulling a single crystal from a molten substance, a crystal that is suspended in the molten substance coaxially with the vertical axis of the vessel is provided between the side wall of a container containing the molten substance and the single crystal. A single crystal pulling apparatus characterized in that the apparatus further comprises an erect partition cylinder having a plurality of protrusions on the outer periphery and an upper end of the cylinder protruding upward from the surface of the molten material. 2. The single crystal pulling device according to claim 1, wherein the plurality of protrusions have the same shape as swirl vanes.