JP2867306B2 - Method and apparatus for producing semiconductor grade polycrystalline silicon - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a polycrystalline silicon rod having a small shape defect and a smooth surface.

2. Description of the Related Art In general, semiconductor-grade polycrystalline silicon supplies a raw material gas into a high-temperature reactor through a nozzle provided at the bottom of a closed reactor, and heats the raw material gas on the surface of a red-heated silicon rod provided in the furnace. It is produced by decomposing or reducing with hydrogen to deposit and grow polycrystalline silicon on the rod surface. Recently, as the demand for semiconductor polycrystalline silicon has increased, large silicon rods have tended to be used because of the need to increase the production volume. As an example, the length of the rod has conventionally been about 1 m, but recently a rod having a length of about 2 m has been used, which inevitably leads to an increase in the size of the manufacturing apparatus. However, when the size of the reactor is increased, the flow rate of the source gas is reduced before reaching the upper part of the reactor, and the flow rate of the source gas is different between the upper part and the lower part of the furnace, so that the concentration tends to be uneven. For this reason, unevenness (popcorn) occurs on the rod surface, and the thickness of the rod becomes uneven, resulting in a shape defect. When irregularities occur on the rod surface, the surface area increases, and the rod is easily contaminated by impurities. In order to eliminate irregularities on the rod surface, the surface temperature of the rod may be lowered and the precipitation reaction may be moderated. However, in this case, the growth of the rod is slowed, and productivity and energy efficiency are remarkably reduced.

[0002]

As described above, conventionally, as the size of a rod is increased, there is a problem that a rod having a smooth surface, no irregularities, and a uniform thickness cannot be efficiently manufactured. The present invention solves such a conventional problem, and provides a method and apparatus for manufacturing a large-sized polycrystalline silicon rod having a smooth rod surface and no shape defect while maintaining high productivity. With the goal.

[0003]

According to the present invention, there is provided:
In the production of semiconductor-grade polycrystalline silicon, a source gas is supplied from a nozzle provided at the bottom of a closed reactor into a high-temperature reactor, and polycrystalline silicon is deposited on a silicon rod provided in the furnace. By using the upper nozzle for supplying the raw material gas toward the bottom and the lower nozzle for supplying the raw material gas toward the bottom of the silicon rod, the supply amount of the raw gas supplied to the upper and lower parts of the silicon rod is adjusted. At the same time, a semiconductor grade polycrystalline silicon manufacturing method characterized by suppressing a change in the gas concentration and manufacturing a polycrystalline silicon rod having a smooth surface and a uniform thickness is used.
Further, according to the present invention, (b) the above production method using a nozzle with a high gas flow rate as the upper nozzle and using a nozzle with a lower gas flow rate as the lower nozzle, (c) a high position of the injection port as the upper nozzle Using a nozzle, the above manufacturing method using a nozzle having a low position of the injection port as a lower nozzle,
(D) When increasing the flow rate of the upper nozzle and the flow rate of the lower nozzle at the beginning of the reaction, make the flow rate of the upper nozzle larger than the flow rate of the lower nozzle, and reduce the flow rate ratio of both nozzles as the reaction proceeds. Is provided. Further, according to the present invention, (e) in a semiconductor-grade polycrystalline silicon manufacturing apparatus having a raw material supply nozzle at the bottom of a sealed reactor, an upper nozzle for supplying a raw material gas toward the upper part of the silicon rod, and a lower part of the silicon rod And a lower-level nozzle for supplying a source gas to the semiconductor-grade polycrystalline silicon.

Semiconductor-grade polycrystalline silicon is generally a gaseous material that decomposes to deposit silicon, for example, monosilane,
Disilane, trichlorosilane, silicon tetrachloride and a mixture of these and hydrogen are purified to a high purity, and a raw material gas is brought into contact with a high-purity silicon substrate at a high temperature to be thermally decomposed or hydrogen reduced to form silicon crystals on the surface of the substrate. It is produced by precipitation. As a specific example of the apparatus, a bell jar type reaction furnace whose inside is sealed is used. Inside the reaction furnace, a plurality of silicon rods are erected, and the lower ends of the rods are supported by an electrode holder, and are supplied with electricity so that the rods glow red during manufacturing. Also, a number of nozzles are uniformly arranged at the bottom of the reaction furnace, and a raw material gas is supplied into the furnace through the nozzles. The raw material gas supplied from the nozzle comes into contact with the red-heated silicon rod, is decomposed and reduced, and deposits silicon on the rod surface. This deposition reaction causes polycrystalline silicon to gradually accumulate on the silicon rod surface, increasing the diameter of the rod and increasing the rod surface area.

[0005] In this case, the raw material gas supplied from the nozzle provided at the furnace bottom contacts the silicon rod surface and flows upward as the raw material gas, for example, trichlorosilane (TCS)
The concentration of TCS decreases due to the progress of the decomposition and precipitation reaction, and the concentration of the source gas changes at the lower and upper portions of the silicon rod. Further, the flow rate decreases as the raw material gas flows upward along the silicon rod from the furnace bottom, so that the supply amount of the raw material gas to the upper part of the silicon rod is insufficient, and the exchange of the raw material gas and the reaction product gas becomes insufficient. There is a fear.

Therefore, in the present invention, an upper nozzle for supplying a source gas toward the upper portion of the silicon rod and a lower nozzle for supplying a source gas toward the lower portion of the silicon rod are used. To supply the source gas independently. As the upper nozzle, a nozzle with a higher injection port can be used, and as the lower nozzle, a nozzle with a lower injection port can be used. In addition, nozzles having different flow rates of the source gas to be injected may be used. A nozzle having a high gas flow rate can be used as an upper nozzle, and a nozzle having a lower gas flow rate can be used as a lower nozzle.

In the present invention, the raw material gas is independently supplied to the upper and lower parts of the silicon rod from the upper nozzle and the lower nozzle, so that the raw material gas is supplied to the upper and lower surfaces of the silicon rod, and The source gas and the by-product gas are sufficiently exchanged, and the gas flow in the furnace becomes smooth, so that the deposition reaction on the silicon rod surface proceeds favorably.

As the precipitation reaction progresses, the diameter of the rod increases, so the supply amount of the raw material gas must be increased. Therefore, when the upper nozzle and the lower nozzle having different gas velocities are used, the flow rate of the upper nozzle and the lower nozzle may be adjusted together with the increase in the supply amount. In particular,
In the initial stage of the reaction, the flow rate (V1) of the upper nozzle is set higher than the flow rate (V2) of the lower nozzle, and as the reaction proceeds, the flow rate ratio (V1 / V2) between the upper nozzle and the lower nozzle is reduced. As an example, in the initial stage of the reaction, the flow rate (V1) of the upper nozzle is 30 m / s to 150 m / s, while the flow rate of the lower nozzle is
(V2) 20m / s ~ 50m / s to advance the reaction, when the rod diameter becomes somewhat thicker, the flow rate of the upper nozzle is constant,
The flow rate of the lower nozzle is kept slightly lower than the flow rate of the upper nozzle.

Since the flow rate of the upper nozzle is large at the beginning of the reaction, the source gas is sufficiently supplied to the upper portion of the silicon rod, and the exchange of the source gas and the reaction product gas on the rod surface is promoted. On the other hand, since the lower part of the rod is close to the source gas supply nozzle, the exchange of the source gas and the reaction product gas is relatively good even if the gas flow rate is small. As a result, the reaction progresses uniformly as a whole silicon rod without any irregularities. A silicon rod having a smooth surface and a uniform thickness grows. When the reaction proceeds and the rod diameter is increased to some extent, surface irregularities are less likely to occur, so it is not necessary to increase the flow rate of the upper nozzle.

Similar effects can be obtained in the case of a two-stage feed in which the position of the ejection port is changed, in addition to the case of the two-flow feed using nozzles having different flow rates as described above.

[0011]

[Example of manufacturing apparatus] An example of a manufacturing apparatus according to the present invention is shown in the figure. As shown in FIG. 1, a bell jar 30 is provided above the base 20 of the reaction furnace 10, and the inside is sealed. A plurality of inverted U-shaped silicon rods 50 serving as seed rods are erected in the furnace, and both lower ends of the rods 50 are electrode holders at the bottom of the furnace.
Supported by 60. The rod 50 is an electrode holder
It is energized through 60 and glows red. An upper nose 70 for supplying a source gas toward the upper part of the rod and a lower nose 80 for supplying a source gas to the lower part of the rod are provided at the furnace bottom. The number of these upper nozzles 70 and lower nozzles 80 is appropriately determined according to the number of silicon rods 50.
The nozzles 70 and 80 need only be uniformly arranged on the furnace bottom, and may be close to or apart from each other. As shown in FIGS. 2A and 2B, the upper nozzle 70 is provided with a nozzle port higher than the lower nozzle 80 so that the source gas can easily flow toward the upper part of the furnace. Also, as shown in FIG. 2 (B), the lower nozzle 80 has a nozzle opening so that the raw material gas can be easily diffused around.
The vicinity of 81 is formed thin. The lower nozzle 80
As shown in FIGS. 2 (C) and 2 (D), the nozzle opening 81 may have a shape expanding upward. The upper nozzle 70 and the lower nozzle 80 may be integrally formed as shown in FIGS. In FIG. 3, the nozzle is constituted by a double tube, in which an upper nozzle 70 is formed inside and a lower nozzle 80 is formed outside. Nozzle port of lower nozzle 80
Numeral 81 is open obliquely upward so that the source gas can easily diffuse to the surroundings. The upper nozzle 70 and the lower nozzle 80 are connected to a raw gas supply pipe 90, respectively. The supply line 90 communicates with a source gas supply source via a flow control valve 92. The raw material gas is supplied to the upper nozzle 70 through the supply line 90.
Then, it is sent to the nozzle 80 for the lower part and supplied from the nozzles 70 and 80 into the furnace. The flow rate of the source gas is adjusted by a valve 92. The exhaust gas after the reaction is discharged to the outlet 93 and the discharge line.
It is discharged outside the furnace through 94.

[0012]

[Examples and Comparative Examples]

EXAMPLE Using the apparatus shown in FIG. 1 and using trichlorosilane and hydrogen as raw material gases, the flow rate (V1) of the upper nozzle and the flow rate (V2) of the lower nozzle were adjusted to the ranges shown in Table 1 to obtain a polycrystal. A silicon rod was manufactured. A rod was manufactured under the same conditions except that the nozzle shown in FIG. 2 was used. The results are summarized in Table 1.

Comparative Example A rod was manufactured under the same conditions except that a conventional apparatus having no distinction between an upper nozzle and a lower nozzle was used. Table 1 shows the results.

[0013]

[Table 1] ───────────────────────────────── V1 (m / s) V2 (m / s) Good shape ratio (%) Remarks Example 1 170 85 No 85 Two-flow feed 2 60 128 No 90 Two-stage feed 3 220 155 No 95 Double-tube nozzle comparative example 1 100 Yes 38 1 Flow feed 280 Yes 35 Same as above ── ──────────────────────────────

[0014]

According to the present invention, a large-sized polycrystalline silicon rod having a smooth rod surface and no shape defect can be manufactured while maintaining high productivity.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a manufacturing apparatus according to the present invention.

FIG. 2 is a schematic sectional view of a nozzle used in the apparatus according to the present invention, wherein (A) shows an upper nozzle, and (B) and (C) show a lower nozzle.

FIG. 3 is a schematic sectional view of another nozzle used in the apparatus according to the present invention.

[Explanation of symbols]

10-reactor, 20-base, 30-bell jar, 50-silicon rod, 60-electrode holder, 70-upper nozzle, 80-lower nozzle, 90-supply line, 92-regulating valve, 93-outlet , 94
-Discharge pipeline

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-295297 (JP, A) JP-A-1-2088312 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C30B 1/00-35/00 C01B 33/02

Claims (5)

(57) [Claims] 1. In the production of semiconductor-grade polycrystalline silicon, a raw material gas is supplied into a reaction furnace at a high temperature from a nozzle provided at the bottom of a closed reaction furnace, and polycrystalline silicon is deposited on a silicon rod provided in the furnace. By using an upper nozzle for supplying the raw material gas toward the upper part of the silicon rod and a lower nozzle for supplying the raw material gas toward the lower part of the silicon rod, the raw material gas supplied to the upper part and the lower part of the silicon rod is A method for producing semiconductor-grade polycrystalline silicon, comprising adjusting a supply amount and suppressing a change in gas concentration to produce a polycrystalline silicon rod having a smooth surface and a uniform thickness. 2. The method according to claim 1, wherein a nozzle having a large gas flow rate is used as the upper nozzle, and a nozzle having a small gas flow rate is used as the lower nozzle. 3. The method according to claim 1, wherein a nozzle having a high injection port is used as the upper nozzle, and a nozzle having a low injection port is used as the lower nozzle. 4. When increasing the flow rate of the upper nozzle and the flow rate of the lower nozzle in the initial stage of the reaction, the flow rate of the upper nozzle is made larger than the flow rate of the lower nozzle. 2. The method according to claim 1, wherein: 5. A semiconductor-grade polycrystalline silicon manufacturing apparatus having a raw material supply nozzle at the bottom of a closed reaction furnace, an upper nozzle for supplying a raw material gas toward an upper part of a silicon rod, and a raw material gas for supplying a lower part of a silicon rod. An apparatus for producing semiconductor-grade polycrystalline silicon, wherein each of the lower nozzles is provided.