JP2720282B2 - Method for pulling Si single crystal with controlled oxygen concentration - 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 for pulling a Si single crystal in which the oxygen concentration is controlled by adjusting the atmosphere.

[0002]

2. Description of the Related Art A typical method for growing a single crystal from a melt is the Czochralski method. In the Czochralski method, a crucible 2 arranged inside a closed container 1 as shown in FIG. A heater 4 and a heat insulating material 5 are provided concentrically on the outer periphery of the crucible 2, and the raw material contained in the crucible 2 is intensively heated by the heater 4 to prepare a melt 6. Melt 6 is maintained at a temperature suitable for single crystal growth. The seed crystal 7 is brought into contact with the melt 6 to grow a single crystal 8 that follows the crystal orientation of the seed crystal 7. The seed crystal 7 is rotated by a rotary winding mechanism 1 through a wire 9.
It is suspended from 0 and pulled up while rotating according to the growth of the single crystal 8. The crucible 2 also descends while rotating appropriately via the support 3. The lowering speed and rotation speed of the support 3 and the rotation speed and rising speed of the seed crystal 7 are as follows.
It is controlled according to the growth rate of the single crystal 8 pulled from the melt 6.

When pulling is performed using the melt 6 to which Sb is added as an n-type impurity, Sb is introduced into the obtained single crystal 8, and a semiconductor material having high conductivity is obtained. Further, oxygen derived from SiO ₂ eluted from the crucible 2 is introduced into the melt 6, and the oxygen is also taken into the single crystal 8.
Oxygen contained in the single crystal 8 precipitates in the bulk when the single crystal 8 is heat-treated, and becomes a precipitation defect. This precipitation defect is used as a gettering center for trapping and rendering harmless heavy metal impurities remaining on the surface of the semiconductor single crystal substrate constituting the electronic device. Also, the oxygen dissolved in the solid
It also has the function of improving the strength of the semiconductor single crystal substrate. For this reason, it is desirable to maintain a high oxygen concentration in the melt in order to increase the concentration of oxygen taken into the single crystal. However, in the conventional method, it has been difficult to stably maintain the oxygen concentration of the Si melt at a high level. The present inventors, in the course of investigating and studying the physical properties of the Si melt, when using a large amount of Sb-doped Si melt,
It has been found that the oxygen concentration of the Si melt uniquely increases as the Sb content increases. And Japanese Patent Application 5-69
No. 924 proposed a method of calculating the oxygen concentration from the Sb content of the melt using the relationship between the Sb content and the oxygen concentration.

[0004]

In a Si melt to which a large amount of Sb has been added, oxygen such as Sb ₂ O and SiO is easily released from the melt surface into the atmosphere. This tendency is
The same applies to a Si melt doped with another group V element such as As or Bi. When oxygen is released from the surface of the melt, the oxygen concentration in the melt fluctuates, and the oxygen concentration of the pulled Si single crystal is significantly reduced. for that reason,
A predetermined characteristic cannot be given to a wafer, a device, or the like cut out from a Si single crystal. The oxygen concentration also fluctuates during the pulling of the Si single crystal. S due to fluctuation during pulling
The oxygen concentration of the i-single crystal becomes unstable, and a single crystal of constant quality cannot be obtained. The present invention has been devised to solve such a problem, and the amount of oxygen released as oxide from the Si melt is adjusted by changing the type of rare gas used in the atmosphere. It is an object of the present invention to control the oxygen concentration of the Si melt and, consequently, the oxygen concentration of the Si single crystal to obtain a Si single crystal having predetermined characteristics.

[0005]

In order to achieve the object, a method for pulling a Si single crystal according to the present invention accommodates a Si melt doped with 1.0 × 10 ^-4 atom% or more of a Group V element in a crucible. Then, when pulling up the Si single crystal from the Si melt, the oxygen concentration is 9.9 as an atmosphere gas in contact with the Si melt.
When growing a Si single crystal exceeding 0 × 10 ¹⁷ atoms / cm ³ , a rare gas having a large mass is supplied with an oxygen concentration of (3.0).
(9.0) × 10 ^{17 When} growing a Si single crystal having ^{17 17} atoms / cm ^3, a rare gas having a small mass is used. The oxygen concentration is calculated as a JEIDA-converted value (3.0
3) is used. As a rare gas having a large mass, K
r, Xe or Rn is used. Ne or Ar is used as the rare gas having a small mass. This single crystal pulling method is applied to a Si melt doped with a group V element such as P, As, Sb, and Bi. Group V element content and S
Considering the relationship with the oxygen concentration of the i melt, the content of the group V element is preferably set to 1 × 10 ⁻⁴ atomic% or more for P and As, and 0.01 atomic% or more for Sb and Bi. .

[0006]

[Function] The oxygen concentration of a single crystal pulled from a Si melt does not depend on the oxygen eluted from the quartz crucible into the melt or the oxygen concentration in the melt, but exclusively reflects the oxygen concentration on the melt surface. You. However, on the surface of the melt in contact with the atmospheric gas, a large amount of oxygen is carried away by the atmospheric gas as an oxide, and the oxygen concentration is not constant. This tendency is particularly strong in a Si melt doped with a V continuum element, which releases oxygen as an oxide having a high vapor pressure. The present inventors have found that as a result of investigation and research, the mass of the rare gas used as the atmosphere gas affects the oxygen concentration on the melt surface.
It is presumed that the mass of the rare gas affects the oxygen concentration on the melt surface by the following mechanism. The Si melt is placed in an atmosphere filled with an ideal gas,
It is assumed that a single crystal has been pulled from the melt.
The number of times f that gas molecules evaporating from the surface of the Si melt collide with gas molecules in the atmosphere is inversely proportional to the square root of the mass _mg of the atmosphere gas. The collision energy E has a relationship of E = K · _mg (K: constant) with the mass _mg . Thus, the collision between the evaporated substrate molecules and the ambient gas is proportional to the square root of the mass _mg .

Therefore, when a rare gas having a larger mass than Ar, which is generally used for pulling a single crystal, is used, evaporation of the substrate from the surface of the melt is suppressed, and the amount of oxide evaporated is reduced. It is expected that the oxygen concentration on the liquid itself and on the melt surface, and thus the oxygen concentration of the obtained Si single crystal, will be maintained at a high level. Conversely, when a rare gas having a smaller mass than Ar is used, it is expected that a Si single crystal having a low oxygen concentration will be obtained. In particular, in a Si melt doped with a group V element, each element alone and an oxide evaporate from the melt surface, but at 1500 ° C. or lower, these evaporates show a higher vapor pressure than SiO. Therefore, the influence of the atmospheric pressure appears greatly. Therefore, it can be seen that, depending on the selection of the rare gas used as the atmosphere gas, Si single crystals having different oxygen concentrations at high levels can be obtained. This inference was confirmed in an example described later. Since a Si single crystal having a high oxygen concentration contains a Group V element as a dopant, it is used as a semiconductor material having characteristics such as a small leak current and efficient gettering of heavy metals. In addition, since the oxygen concentration is adjusted to a predetermined range, the reliability regarding the quality is high. This tendency is the same when other group V elements such as P, As, and Bi are used as the dopant.

[0008]

【Example】

Example 1: 20 g of pure Si is 50 mm in diameter and 60 m in height
m, and heated to a surface temperature of 1450 ° C. with a vertical temperature difference of 50 ° C. After maintaining this state for 30 minutes, 0.7 g of pure Sb was added to the Si melt. Further, the temperature is kept for 30 minutes under the same temperature condition, and the cooling rate is
At 1350 ° C. and cooled to room temperature at a cooling rate of 50 ° C./hour. Thus, a Sb-doped Si melt having a target Sb concentration of 0.8 atomic% was prepared. Ne, Ar, K
In an atmosphere of r and Xe, the Sb-doped Si
After heating to １５1542 ° C. and holding for 90 minutes, single crystal pulling was started. A test piece having a thickness of 2 mm was cut out from the obtained single crystal, and the oxygen concentration was measured by SIMS. During the pulling, the conditions were set so that the oxygen concentration on the melt surface was the same, and the oxygen concentration of the melt itself was measured.

Table 1 shows the oxygen concentration of each test piece cut from the Si single crystal pulled in an Ar atmosphere in relation to the Si melt and the oxygen concentration on the melt surface. From Table 1,
It can be seen that the oxygen concentration of the Si single crystal does not depend on the oxygen concentration of the melt itself, but changes according to the oxygen concentration on the melt surface. In Table 1, the oxygen concentration of the melt itself was measured by SIMS for the rapidly solidified melt in the same manner as for the single crystal test piece. The oxygen concentration on the melt surface was calculated by the following equation using the atmospheric pressure P found by the present inventors as a factor.

(Equation 1)

[0010]

[Table 1]

As is clear from Table 1, the oxygen concentration C ₃ of the Si single crystal largely depends on the oxygen concentration C ₂ on the melt surface. Further, the oxygen concentration on the surface of the melt was examined after a lapse of a predetermined time from the start of pulling of the Si single crystal, and the change over time in the oxygen concentration for each type of rare gas was examined. As is clear from FIG. 2 showing the investigation results, the oxygen concentration on the melt surface shows a tendency to decrease as the mass of the rare gas used as the atmosphere gas decreases, and the oxygen concentration decreases with the rare gas having a large mass. Was suppressed. Using Kr as an atmosphere gas, a liquid surface temperature of 14 under an atmosphere of 30 Torr.
A Si single crystal was pulled up from a 50 ° C. Si melt. The oxygen concentration of the obtained Si single crystal is (9.5 to 11.0) × 1
It was stable in the range of 0 ¹⁷ atoms / cm ³ . On the other hand, Ne
Was grown under the same conditions except that was used as an atmospheric gas. The oxygen concentration of the obtained Si single crystal was (3-5) × 10 ¹⁷ atoms / cm ³ . Each of them had a high level of oxygen concentration within a predetermined range and could be used as a semiconductor device material having excellent quality stability.

[0012]

As described above, in the present invention, by using a rare gas having a different mass as an atmosphere gas in contact with a Si melt doped with a group V element, the oxygen concentration of a pulled Si single crystal can be improved. The oxygen concentration on the surface of the melt, which is closely related to the above, is controlled. As a result, the oxygen concentration of the pulled Si single crystal is maintained at a high level within a predetermined range in accordance with the mass of the rare gas, and a Si single crystal having a constant quality can be obtained. The obtained single crystal contains a large amount of oxygen effective for trapping electrons leaked during operation of the semiconductor device and gettering of heavy metals, etc. It is used as a semiconductor material suitable for a bipolar device or the like utilizing a channel inside.

[Brief description of the drawings]

Fig. 1 Czochralski method for pulling a single crystal from a melt

FIG. 2 Influence of rare gas on oxygen concentration of Si melt

[Explanation of symbols]

1: Closed container 2: Crucible 3: Support 4:
Heater 5: Insulation material 6: Melt 7: Seed crystal 8:
Single crystal 9: Wire 10: Rotary winding mechanism

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Koji Izumi, Inventor 1770-1-502, Arakawa-oki, Ami-machi, Inashiki-gun, Ibaraki (72) Inventor Shigeyuki Kimura 3-712 Takezono, Tsukuba-shi, Ibaraki

Claims (3)

(57) [Claims] 1. An atmosphere in contact with a Si melt doped with 1.0 × 10 ⁻⁴ atom% or more of a Group V element in a crucible and pulling a Si single crystal from the Si melt. The gas has an oxygen concentration of 9.0 × 10 ¹⁷ atoms / c.
When growing a Si single crystal exceeding m ³ , a rare gas having a large mass is used. When growing a Si single crystal having an oxygen concentration of (3.0 to 9.0) × 10 ¹⁷ atoms / cm ³ , An Si single crystal pulling method using a rare gas having a small mass. 2. The method according to claim 1, wherein Kr, Xe or Rn is used as the noble gas having a large mass. 3. A rare gas having a small mass of Ne or Ar
The method of claim 1, wherein