JP2804456B2 - Method for growing Si single crystal with uniform impurity concentration distribution in radial direction - 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 growing a Si single crystal having a uniform impurity concentration distribution in a radial direction from a melt.

[0002]

2. Description of the Related Art A typical method for growing a Si 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 S
It is maintained at a temperature suitable for i-single crystal growth. The seed crystal 7 is brought into contact with the melt 6 to grow an Si single crystal 8 that follows the crystal orientation of the seed crystal 7. The seed crystal 7 is suspended from a rotary winding mechanism 10 or a rigid pulling rod via a wire 9, and is pulled while rotating in accordance with the growth of the Si single crystal 8. The crucible 2 also descends while rotating appropriately via the support 3. The lowering speed and rotating speed of the support 3 and the rotating speed and rising speed of the seed crystal 7 are controlled according to the growth speed of the Si single crystal 8 pulled from the melt 6.

[0003]

Various impurities are added to the melt 6 in order to impart various required characteristics to the Si single crystal 8. However, depending on the type of impurity added, the behavior of the melt at the growth interface may be different. Among them, Si doped with impurities such as Ga and Sb
In the melt, the effect of stirring the melt is easily reduced, and accordingly, the impurity distribution in the radial direction becomes non-uniform. The present inventors presumed the cause of the non-uniform impurity concentration as follows. That is, the melt to which Ga or Sb is added has a thermal expansion coefficient of about 6.0 × 10 ⁻⁶ / ° C. near the melting point, and the turbulence effect depending on the thermal expansion coefficient is reduced. Therefore, the added impurities are not sufficiently stirred, and as a result, the impurity concentration in the radial direction immediately below the growth interface becomes uneven. The non-uniform impurity concentration distribution is preserved as it is in the impurity boundary layer formed immediately below the interface, and is taken into the crystal. as a result,
The impurity concentration of the pulled Si single crystal becomes unstable in the radial direction, and the quality stability of the obtained Si single crystal is reduced. The present invention has been devised to solve such a problem, and an element for increasing the thermal expansion coefficient is made of Si.
It is an object of the present invention to improve the effect of diffusing the melt immediately below the growth interface by additionally adding to the melt, and to obtain a high-quality Si single crystal having a uniform impurity concentration in the radial direction.

[0004]

According to the method for growing a Si single crystal of the present invention, when a Si single crystal is pulled up from a Si melt to which Ga or Sb is added by the Czochralski method, a periodic rule is set. An element that belongs to the same group as Ga or Sb in the table and that increases the thermal expansion coefficient of the melt near the melting point is additionally added to the melt.
Elements that increase the coefficient of thermal expansion include B and P,
B is added to the Ga-added Si melt, and P is added to the Sb-added Si melt. These additional elements are such that the added element (Ga or Sb) matches the group (group III or IV) belonging to the periodic table and the resistance value after addition becomes 0.001 to 10 Ω · cm. Added
Considering evaporation on the melt surface during crystal growth, 1 × 1
The addition amount is determined in the range of 0 ^{18 to} 5 × 10 ²⁰ atoms / cm ³ .

[0005]

The non-uniformity of the impurity concentration distribution in the radial direction of the single crystal pulled from the Si melt depends on the uniformity of the impurity concentration distribution of the melt immediately below the growth interface.
Therefore, in order to make the impurity concentration distribution uniform in the radial direction, it is necessary to activate the stirring of the melt immediately below the growth interface. According to the study of the present inventors, when elements such as B and P which increase the thermal expansion of the melt are added,
It has been found that stirring of the melt is promoted immediately below the growth interface. That is, the melt to which elements such as B and P are added has a locally large thermal expansion just below the growth interface near the freezing point. Therefore, the difference in thermal expansion between the melt and the surrounding melt is increased, and the circulating flow of the melt is accelerated due to the difference in thermal expansion. As a result, the melt immediately below the growth interface receives a sufficient stirring action, and the impurity concentration distribution in the radial direction is made uniform. Therefore, the Si single crystal pulled from the melt becomes a high-quality crystal having a uniform impurity concentration distribution in the radial direction.

[0006]

EXAMPLE B or P was further added at 10 ¹⁵ atoms / cm ³ to 5 kg of a Si raw material to which 0.1 atomic% of Ga or Sb was added, and was dissolved in a crucible. Then, the Si melt was held in a chamber filled with argon gas until the start of pulling the single crystal. From the temperature dependence of the density shown in FIG. 2, the melt to which Ga or Sb is added is estimated to have a thermal expansion coefficient of about 6.0 × 10 ⁻⁶ / ° C. in a temperature range from the melting point to 1430 ° C. In particular, in the temperature range from the melting point to 1430 ° C., the rapid fluctuation of the density is alleviated, a sufficient stirring action cannot be obtained, and it is apparent that the impurity distribution in the melt is uniform. In the case where B or P was further added to this melt, the melting point to 1 point was obtained from the temperature dependency of the density of adding 0.1 atomic% B or P shown in FIG.
The thermal expansion coefficient in the temperature range of 430 ° C. is about 1.5 × 10
^-3 / ° C. That is, the thermal expansion coefficient is expected to increase as compared with the case where Ga or Sb is added, and the circulating flow in the melt becomes active.

[0007] Actually, each of the Ga-doped Si melt and the Ga, B-doped Si melt has a diameter of 3 inches and a length of 200 mm.
mm single crystal was pulled up, and the impurity concentration in the growth direction was measured. As shown in FIG. 3 showing the measurement results, when B was not added to the Ga-doped Si melt, the variation in the resistivity in the radial direction was ± 20%. On the other hand, when B was further added, the variation in resistivity was suppressed to a range of ± 5%. As is clear from this contrast,
By adding an element that increases the coefficient of thermal expansion,
It was confirmed that sufficient stirring of the melt was ensured immediately below the growth interface, and that a Si single crystal having a uniform impurity concentration distribution in the radial direction was obtained.

[0008]

As described above, in the present invention, Ga or S doped with an element which increases the coefficient of thermal expansion is used.
From the b-doped Si melt, S
Growing i single crystal. The element that increases the coefficient of thermal expansion has the effect of sufficiently stirring the melt just below the growth interface,
A single crystal can be grown from a melt having a uniform impurity concentration distribution. Therefore, the obtained Si single crystal is a high-quality single crystal having a uniform impurity concentration distribution in the radial direction.

[Brief description of the drawings]

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

FIG. 2 is a graph showing the relationship between the density and temperature of a Si melt to which various impurities are added.

FIG. 3 is a graph showing an impurity concentration distribution in a growth direction of a pulled Si single crystal by a resistance value.

[Explanation of symbols]

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

────────────────────────────────────────────────── ─── Continuing on the front page (73) Patent holder 000006264 Mitsubishi Materials Corporation 1-5-1, Otemachi, Chiyoda-ku, Tokyo (73) Patent holder 000205351 Sumitomo Sitix Corporation 1-Higashihama-cho, Amagasaki-shi, Hyogo (72 Inventor Soroku Kawanishi 1-16-2 Tokodai, Tsukuba, Ibaraki Pref. (72) Inventor Koji Izuma, 1770-1-502 off Arakawa, Ami-cho, Inashiki-gun, Ibaraki Pref. 4182-3 Kashima (72) Inventor Hitoshi Sasaki 1-545, Taiseicho, Omiya City, Saitama Prefecture (72) Inventor Shigeyuki Kimura 3-712 Takezono, Tsukuba City, Ibaraki Prefecture (72) Inventor Atsushi Ikari 2- Tokodai, Tsukuba City, Ibaraki Prefecture 12-15 (56) References JP-A-57-118089 (JP, A) JP-A-6-204150 (JP, A) JP-A-62-226890 (JP, A) KAWANISHI S. ET AL. , "EFFECT OF IMPU RITY DOPING ON DEN SITY ANOMALLIES INM OLTEN SILICON", JPN. J. APPL. PHYS. PART 2, JAPAN, 15 NOV. 1995, VOL. 34, NO. 11B, PP. L1509-1512 KAWANISHI S.L. ET AL. , "EFFECT OF GALL IUM ADDITION ON DE NITY VARIATION OF MOLTEN SILICON", JPN. J. APPL. PHYS. PAR T 1, JAPAN, FEB. 1995, VOL. 34, NO. 2A, PP. 482-483 (58) Fields surveyed (Int.Cl. ⁶ , DB name) C30B 29/06 C30B 15/04 H01L 21/208

Claims (2)

(57) [Claims] Czochral from a Si melt to which Ga is added.
When pulling the Si single crystal by the ski method,
B, which increases the coefficient of thermal expansion of the melt, is added to the melt.
A method for growing a Si single crystal in which temperature fluctuation is suppressed, characterized by additionally adding . 2. Czochral from a Si melt to which Sb has been added.
When pulling the Si single crystal by the ski method,
P, which increases the thermal expansion coefficient of the melt, is added to the melt.
A method for growing a Si single crystal in which temperature fluctuation is suppressed, characterized by additionally adding .