JPH0383886A - Susceptor for pulling up single crystal - Google Patents

Abstract

PURPOSE:To lower amount radiating to the upper part of melted material and suppressing convection in the interior of the melted material and uniform oxygen concentration by dividing a susceptor into at least two upper and lower parts. CONSTITUTION:A ring-formed upper dividing body 20a formed into taper gradually enlarging as the lower end face 20c is advanced downward and vessel like lower dividing body 20b put above the pedestalling 4 and formed into taper gradually enlarging as the upper end face 20d is advanced downward and contact face of lower end face 20c and upper end face 20d are located on the upper part of surface part of surface part 11a of melt 11 in pulling-up initiation point of time and arranged at the position always heated by a heater 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a susceptor for pulling a silicon single crystal used in a single crystal pulling apparatus using the Tyrochralski method.

[Prior Art] Conventionally, an apparatus as shown in FIG. 5 has been used to manufacture silicon single crystals by the Tyrochralski method.

This single crystal pulling apparatus is configured such that a quartz crucible 2 is provided in the center of a furnace body i, and substantially the entire area of the quartz crucible 2 is held inside a vessel-shaped graphite susceptor 3. The lower end of the graphite susceptor 3 is attached to the upper end of a shaft 5 via a bedester ring 4, and the quartz crucible 2 is driven by a quartz crucible rotating motor and a quartz crucible lifting motor (not shown). In addition, quartz crucible 2
A heater 6 is provided around the molten metal 11, and the amount of heating by this heater is controlled to keep the molten metal 11 at or above the melting point of the silicon. Although not shown, a seed 10 (crystal seed) attached via a seed support 9 at the tip of the pulling wire 8 is applied to the molten metal 11 in the quartz crucible 2 using a pulling II placed above. By pulling up after dipping, the single crystal rod 12 that has grown sequentially starting from the seed IO can be pulled up.

As the single crystal rod 12 is pulled up, the amount of the molten metal 11 decreases, but the quartz crucible lifting motor is driven to gradually raise the quartz crucible 2 to keep the surface level of the molten metal 11 constant. Furthermore, in order to obtain a defect-free single crystal rod 12 with a constant shape, it is important to maintain the temperature of the surface 11a of the molten metal 11 at a certain temperature higher than the silicon melting point.

[Problem II to be Solved by the Invention] However, when the area around the quartz crucible 2 is heated by the heater 6 in this way, the surface portion 11a of the molten metal 11
The temperature at the bottom tends to be higher than the temperature at the bottom. This is considered to be because the amount of heat dissipated from the surface portion 11a of the molten metal 11 into the atmosphere of the furnace body l is greater than the amount of heat escaping through the bedestal ring 4 to the sleeve 5. Due to this reverse temperature gradient, thermal convection occurs between the bottom part 11b and the surface part 11a of the molten metal 11, and the molten metal 11 flows from the bottom part 11b to the surface part 11a.
It begins to flow to Then, the flowing silicon melt
Ihxt sequentially reacts with the inner wall of the quartz crucible 2 to produce volatile silicon oxide (Sin), and some of this silicon oxide is mixed into the molten metal it. Oxygen is eluted from the inner wall of the crucible 2 into the molten metal 11.

Due to the mechanism of the molten SZ heated by the heater 6, the manufactured single crystal rod 12 exhibits an extremely high oxygen concentration even after the shoulder on the tip side, so it can be used as a semiconductor. The number of crystals decreases, and the yield of single crystals deteriorates.

For example, as a solution to the above problem, a plurality of heaters are arranged around the quartz crucible in the vertical direction as heating means for the quartz crucible, and the heating amount of each heater is adjusted depending on the progress of the single crystal pulling process. There is one that sets the temperature of molten silicon at a constant temperature.

However, although such devices can easily set the molten metal at a constant temperature by controlling multiple heaters, they have disadvantages such as the complicated configuration of the heaters and the need to provide a control machine. Ta.

The present invention was proposed in view of the above circumstances, and an object of the present invention is to provide a susceptor for pulling a single crystal that can constantly maintain the molten metal in a quartz crucible at a set temperature.

[Means for Solving the Problems] A susceptor for pulling a single crystal according to the present invention is characterized in that the susceptor is divided into at least two parts, an upper and a lower part.

Generally, a susceptor is integrally formed into a vessel shape in order to house and reinforce a quartz crucible. However, as a result of research by the present inventors, the upper edge of the susceptor, which extends upward from the surface of the molten metal, plays the role of a heat radiator that repels the heat from the surface of the molten metal and releases it into the furnace body. It was discovered that the surface temperature of the molten metal decreases due to storage. The present invention is based on this knowledge.

[Function] According to the susceptor for pulling single crystals of the present invention, the graphite susceptor is configured in a shape in which it is divided into at least two parts, upper and lower, so that heat escape from the surface of the molten metal is prevented without reducing the reinforcing function. , reducing only the amount of heat output from the top. As a result, the degree of the inverse gradient of the temperature of the molten metal is reduced, and thermal convection within the molten metal is suppressed, so that the oxygen concentration also becomes in-path condition. A single crystal rod manufactured in such a molten state has an optimum oxygen concentration value as a semiconductor material in substantially the entire area from its tip to its end.

In addition, among the susceptors configured in a split shape, the lower split body can be split in the vertical direction to absorb stress and strain caused by thermal expansion, thereby extending the life of the susceptor. It is preferable that the upper divided body is an integral ring-shaped body in order not to impair the reinforcing function of the quartz crucible.

[Example] An example of a graphite susceptor for pulling a single crystal according to the present invention will be described with reference to FIGS. 1 and 4. In addition,
Components similar to those in the above embodiment are given the same reference numerals, and their explanation will be omitted.

FIG. 1 is a diagram showing a graphite susceptor for pulling a single crystal according to the present invention. The overall shape of the graphite susceptor 20 has the same dimensions as a conventional susceptor, and is divided into two parts, an upper and a lower part, consisting of an upper part 20a and a lower part 20b. The upper divided body 20a has a ring shape, and its lower end surface 2
0c is formed in a tapered shape whose diameter gradually increases as it goes downward. Further, the lower divided body 20a is formed in a vessel shape, and the lower part thereof is placed on the upper part of the bedestal ring 4, and the upper end surface 20d is formed in a tapered shape whose diameter gradually increases as it goes downward. and,
The graphite susceptor 20 is constructed by stacking the upper divided body 20a on the lower divided body 20b with the lower end surface 20c and the upper end surface 20d in contact with each other.

As shown in FIGS. 2 and 3, this split-shaped graphite susceptor 20 has a split surface (a contact surface between the lower end surface 20c and the upper end surface 20d) that is connected to the molten metal at the time of starting pulling.
It is located above the surface portion 11a of the heater 6, and is placed in a position where it is constantly heated by the heater 6.

When performing single crystal pulling work, the molten metal 1
1, the inner surface wJtla is conducted to the lower divided body 20b via the quartz crucible 2, and heat (indicated by the arrow in FIG. A slight gap 20 between the lower surface 20c of 20a and
Since heat is formed, it is difficult for heat to be transmitted to the upper divided body 20a, and the amount of heat radiation is reduced.

Therefore, since the graphite susceptor 20 is configured to be divided into at least two parts, upper and lower, the escape of heat from the surface portion 11a of the molten metal mxi through the quartz crucible 2 and the graphite susceptor 3 is reduced, and the temperature of the molten metal 11 is reduced. Since the degree of the reverse gradient is reduced and thermal convection inside the melt s11 is suppressed, the oxygen concentration is also in a substantially angular-state. The single crystal +41112 produced from this single crystal has an oxygen concentration value suitable for a semiconductor material in almost the entire area from its tip to its end.

As described above, when the graphite susceptor 20 is configured to be divided into upper and lower parts, the lower side expands because the temperatures of the upper and lower parts are different during operation, but the expansion occurs due to the abutment surfaces of the divided surfaces 20c and 20d being misaligned. I can do it. In addition, since the overall height of the graphite susceptor 20 is unchanged from that of the conventional one, the reinforcing function of the quartz crucible 2 can be fully demonstrated.

Moreover, what is shown in FIG. 4 is another implementation of the present invention,
The lower divided body 20b is divided into a plurality of parts in the vertical direction (in the illustrated example, there are three parts).
Division) It is constructed in a divided shape. These vertically divided bodies 20f, 20g, 20h
Since the graphite susceptor 20 is configured such that the upper part of the graphite susceptor 20 is supported by the ring-shaped upper divided body 20a, it is possible to absorb the stress strain caused by thermal expansion and prevent the graphite susceptor 20 from cracking. 20 can be extended in life.

In this example, when assembling the graphite susceptor 20, the upper divided body 20a serves to hold down the plurality of lower divided bodies 20b, making it easy to set the crucible 2 and the like on the upper part of the shaft 5.

[Effects of the Invention] As explained above, according to the present invention, the amount of heat dissipated to the upper part of the molten metal can be reduced by configuring the graphite susceptor into at least two halves, without changing the overall shape of the graphite susceptor. As a result, the degree of the inverse gradient of the temperature of the molten metal is reduced and thermal convection inside the molten metal is suppressed, so that the oxygen concentration also becomes approximately angular. The single-crystal rod produced in this way has an optimum oxygen concentration value as a semiconductor material over substantially the entire region from the tip to the end.

[Brief explanation of drawings]

Figures i to 4 show embodiments of the susceptor for pulling single crystals of the present invention. 3 is a sectional view of the main parts arranged in the apparatus, FIG. 3 is a sectional view of the main parts showing the vicinity of the molten metal surface inside the quartz crucible, FIG. 4 is an external view showing another embodiment of the susceptor, and FIG. 5 is the conventional susceptor. FIG. 2 is a cross-sectional view of a susceptor installed in a single crystal pulling device. l... Furnace body, 2... Quartz crucible, 6... Heater, ! ... Molten metal, la... Molten metal surface, llb... Molten metal bottom, 2... Single crystal rod, O... Graphite susceptor, Oa...・Upper divided body, 20b...Lower divided body, Oc...Lower end surface of the upper divided body, 0, d...Upper end surface of the lower divided body, Oe...
Gap, CB, 20g, 20h... Vertically divided body.

Claims (1)

[Scope of Claim] A vessel-shaped susceptor for holding a quartz crucible used in a single crystal pulling device using the Czochralski method, wherein the susceptor is configured to be divided into at least two parts, an upper and a lower part. Characteristic susceptor for pulling single crystals.