JPH0718764Y2 - Semiconductor single crystal growth equipment - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor single crystal growing apparatus for growing a single crystal by using a double-structured crucible, and particularly, it relates to a carbon compound discharging property in the vicinity of a melt. Concerning improvements to enhance.

"Prior art" When manufacturing a silicon single crystal doped with a dopant such as B, R, Sb by the CZ method, the segregation coefficient of these dopant atoms is not 1, so the dopant concentration in the grown single crystal is There is a problem in that the quality becomes non-uniform in the longitudinal direction and only a part of it becomes the desired quality.

As measures for improving it, JP-A-49-10664 and USP4352784.
In the issue, a double crucible consisting of an outer crucible body and an inner crucible body is used, and by utilizing the difference in the dopant concentration of the raw material melts partitioned by each crucible, the dopant concentration in the single crystal is made substantially uniform, 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 an outer crucible body 2A has a cylindrical inner crucible body 2B, 3 is a graphite susceptor, 4 is a heater, and 5 is a heat retaining cylinder. Then, the 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 the impurities generated from the raw material melt Y. A through hole is formed at the lower end of the inner crucible body 2B.

"Problems to be solved by the device" 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 often been confirmed that the carbon concentration that can be used as a semiconductor element is partially exceeded and that the yield of single crystals is deteriorated.

This kind of carbon pollution originates from various graphite parts (heater 4, heat retaining cylinder 5, susceptor 3, support of inner crucible 2B, etc.) used in the furnace body. Volatile SiO 2 is generated by the reaction with the quartz crucible 2, and this SiO 2 CO
To occur.

SiO + 2C → SiC + CO Therefore, if carbon contamination is more prominent in the double crucible than in the single crucible, in the case of the double crucible, there is some mechanism for dissolving more generated CO in the raw material melt Y. Expected to exist.

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 2B
As shown in the figure, the gas stays in the gap between the outer crucible 2A 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 melt efficiently melts. It melts in the liquid Y and increases the CO concentration of the melt Y and thus of the single crystal T.

As a measure for improving this phenomenon, first, increasing the flow rate of the argon gas supplied into the furnace body 1 is required, but in that case, the cost required for gas supply is significantly increased, and the condition for growing the single crystal T is given. The adverse effects cannot be ignored.

"Means for Solving the Problems" The present invention has been made to solve the above problems, and a raw material melt having a lower end edge in a double crucible in a peripheral wall portion of an outer crucible body and / or an inner crucible body. It is characterized by forming a plurality of vent holes located at a height of 3 to 30 mm.

"Operation" In this semiconductor single crystal growth apparatus, part of the argon gas introduced from the upper part of the furnace body into the inner crucible body or / and
Since the gas containing impurities passes through the plurality of vent holes formed in the peripheral wall of the outer crucible body and flows into the gap between the outer crucible body and the inner crucible body, the gas containing impurities does not stay in this gap and is quickly discharged. . Therefore, compared to conventional equipment,
The amount of CO penetration is reduced, and the carbon concentration in the single crystal is reduced.

[Embodiment] FIG. 1 and FIG. 2 are vertical sectional views showing an embodiment of a semiconductor single crystal growing apparatus according to the present invention.

In the figure, reference numeral 10 is a furnace body composed of an upper body 10A and a lower body 10B, a lower shaft 11 which is raised and lowered and rotated is arranged in the center of the furnace body 10, and a graphite susceptor 12 is provided at the upper end of the lower shaft 11. A quartz double crucible 13 is fixed. Also, the susceptor 12
A heater 14 and a heat-retaining cylinder 15 are arranged in this order around the outer circumference of the furnace, and a wire 17 for holding a seed crystal 16 is moved up and down above the furnace body 10 to move the center of the melt Y in the double crucible 13. Is provided with a pulling mechanism (not shown) for growing the single crystal T.

The double crucible 13 has a bottomed cylindrical outer crucible body 13A,
It is composed of a cylindrical inner crucible body 13B coaxially arranged therein, and a through hole (not shown) is provided at the lower end of the inner crucible body 13B.
Are formed. Further, inside the furnace body 10, a raw material supply pipe 18 is fixed so as to vertically penetrate the upper wall of the furnace body, and its lower end is positioned above the gap between the inner crucible body 13B and the outer crucible body 13A. The furnace body 10 is further formed with a gas inlet 19 and a gas outlet 20.

In the peripheral wall portions of the outer crucible body 13A and the inner crucible body 13B,
A plurality of round ventilation holes 21 and 22 are formed at equal intervals in the circumferential direction. The height H from the raw material melt Y at the lower edges of these vents 21 and 22 is 3 to 30 mm, and the diameter is 10 to
It is about 30 mm. If the height from the raw material melt Y is less than 3 mm, when the raw material falls from the raw material supply pipe 18, the swelled melt spills out of the crucible through the vent hole 21 or through the vent hole 22. There is a possibility that the grown portion of the crystal T is adversely affected. On the other hand, if the height of the bottom edge is 30 mm or more, the ventilation port 2
Gas stays below 1,22 and the staying prevention effect is reduced. Further, if the diameter of the vent holes 21 and 22 is less than 10 mm, sufficient gas flowability cannot be obtained, and if it is 30 mm or more, the splash of the melt Y passes through this when the raw material falls and affects the growth part of the single crystal T. May be given. The number of ventilation holes 21 and 22 is 2
The size of the heavy crucible 13 is taken into consideration so as to obtain sufficient air permeability.

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 19 to melt the raw material. Then, the seed crystal 16 is immersed in the melt Y to grow the single crystal T, and the raw material is supplied through the raw material supply pipe 18 to compensate for the decrease in the melt Y. At this time, melt Y and crucible 13
React with each other to form SiO, and a part of this SiO
Reacts with graphite parts inside to produce CO.

On the other hand, the argon gas supplied from the gas introduction port 19 descends along the single crystal T, and then the ventilation port 22 of the inner crucible body 13B.
Through the space between the inner crucible body 13B and the outer crucible body 13A,
Furthermore, it flows out of the crucible through the vent 21. At this time, as the crucible 13 rotates, the positions of the vent holes 21 and 22 with respect to the melt Y constantly change, so that the gas is uniformly distributed over the entire circumference of the gap. Therefore, the gas containing CO and SiO is quickly discharged from the gap without staying, so that the total amount of CO dissolved in the melt Y is remarkably reduced as compared with the conventional apparatus, and a high-quality single carbon with a low carbon concentration is obtained. It is possible to produce crystal T.

Further, by solving the problem of gas retention, the peripheral wall portions of the inner crucible body 13B and the outer crucible body 13A can be set higher than in the conventional device, so that when the melt Y is splashed by the raw material falling from the raw material supply pipe 18. Moreover, this bounce does not jump into the inside of the inner crucible body 13B, and there is no risk of affecting the growing portion of the single crystal T and causing dislocation defects or the like. At the same time, if the peripheral wall is raised, the radiant heat reaching the single crystal T can be reduced,
It is possible to improve the growth rate of the single crystal T.

Although the vents 21 and 22 are formed in both the outer crucible body 13A and the inner crucible body 13B in the above-described embodiment, only the outer crucible body 13A as shown in FIG. 3 or as shown in FIG. Vents may be formed only in the inner crucible body 13B. In any case, a gas retention preventing effect can be obtained as shown in the figure.

Further, although the shape of the vent holes 21 and 22 is circular in the above-described embodiment, it may be changed to, for example, a quadrangle or a slit shape extending in the circumferential direction or the vertical direction. Further, in the above-mentioned embodiment, the upper end of the inner crucible body 13B is a horizontal plane, but it is chamfered to have a semicircular cross section, or an inclined surface that descends toward the outside or an inclined surface that descends toward the inside. With this, the flow path of the argon gas flow can be adjusted.
Similarly, the entire inner crucible body 13B can be formed into a conical shape that constricts upward, and in this case, a larger amount of gas passes through the gap between the inner crucible body 13B and the outer crucible body 13A. Become.

Further, it is possible to adopt a configuration (batch type) in which the raw material supply pipe 18 is not provided, and in that case, the growth may be performed while raising the crucible 13 as the melt Y decreases.

"Experimental example" Next, the effect of the present invention will be demonstrated by giving an experimental example.

Using the device shown in Fig. 1, the full length under the following growing conditions
A 500 mm silicon single crystal was prepared. Eight circular vents each having a diameter of 20 mm were formed in each of the outer crucible body and the inner crucible body at equal intervals in the circumferential direction so that the lower ends thereof were located 10 mm from the raw material melt.

Inner diameter of outer crucible: 250 mm Inner diameter of crucible: 170 mm Initial filling amount of raw material: 8 kg Depth of initial melt: 80 mm Outer diameter of single crystal: 75 mm Height of outer crucible from melt: 60 mm Inner crucible Height from body melt: 60mm Argon gas supply rate: 50l / min (normal pressure) Raw material supply to crucible: None (batch type) On the other hand, only the double crucible of the above equipment forms a vent. The single crystal was pulled under the same conditions except that the same size was replaced.

Further, similarly, this time, while supplying the raw material using the raw material supply pipe, single crystals were produced under the same conditions by using the same crucible as the above-mentioned two kinds. However, the length of each single crystal is 500m
It was m.

The carbon concentration of each of the four single crystals thus obtained was measured at multiple points in the longitudinal direction using an IR measuring device (carbon detection limit of 0.1 × 10 ¹⁷ atoms / cm ³ ). The results are shown in FIG. 5 (in the case of the batch method) and FIG. 6 (in the case of additionally supplying the raw materials). As is clear from these graphs, in the device using the conventional double crucible, the carbon concentration gradually increases with the growth, whereas in the device of the present invention, the carbon concentration is higher than that in most of the single crystals. Was kept low.

[Advantages of the Invention] As described above, in the semiconductor single crystal growth apparatus according to the present invention, after the argon gas introduced from the upper part of the furnace body descends along the single crystal, the inner crucible body and / or the outer crucible body is formed. It constantly flows through a plurality of vent holes in the peripheral wall of the body into the gap between the inner crucible body and the outer crucible body. This allows CO
Since the gas containing SiO and SiO is quickly discharged from the gap without staying, it dissolves in the melt as compared with the conventional equipment.
It is possible to produce a good-quality single crystal with a low carbon concentration because the total amount of CO is significantly reduced.

Also, by solving the problem of gas retention, the peripheral wall parts of the inner crucible body and the outer crucible body can be set higher than before, so even if the melt splashes due to the raw material falling from the raw material supply pipe, this splash Can be prevented from jumping into the inner crucible body and affecting the growing portion of the single crystal, and dislocations and defects in the single crystal can be reduced.

Further, if the peripheral wall is raised, the radiant heat reaching the single crystal is reduced, so that the single crystal growth rate can be improved.

[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, and FIG. 2 is a vertical sectional view of a main part of the apparatus. 3 and 4 are longitudinal sectional views showing another embodiment of the present invention, and FIGS. 5 and 6 are graphs showing the effect of the present invention. On the other hand, FIG. 7 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, 18
…… Raw material supply pipe, 19 …… Gas inlet, 20 …… Gas outlet, 21,22 …… Vent, H ・ ・ ・ Height of melt from the bottom edge of the vent.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeaki Sahira 1-297 Kitabukuro-cho, Omiya-shi, Saitama, Central Research Laboratory, Mitsubishi Metals Co., Ltd. (56) Reference JP-A-61-132583 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. A semiconductor single crystal growth apparatus, comprising 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 inside of the inner crucible body, wherein the outer crucible body and / or On the peripheral wall of the inner crucible,
A semiconductor single crystal growing apparatus having a plurality of vent holes whose lower edges are located at a height of 3 to 30 mm from a raw material melt in a double crucible.