JP2001199795A - Method for producing silicon single crystal ingot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a silicon single crystal ingot, capable of solving unevenness of BMD density on a wafer surface caused by an OSF ring in pulling out the silicon single crystal ingot doped with nitrogen by CZ method. SOLUTION: This silicon single crystal ingot is characterized by pulling it out using Czochralski method from a molten silicon liquid 7 obtained by doping nitrogen N to a polysilicon, having 1×1013-1.2×1015 atoms/cm3 nitrogen concentration and setting <=200 min passing time through 1,100-700 deg.C temperature zone for solving the unevenness of the BMD density on the wafer surface caused by the OSF ring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a silicon single crystal ingot, and more particularly to a silicon single crystal ingot for eliminating non-uniformity in BMD density in a wafer surface due to an OSF ring of a nitrogen-doped silicon single crystal ingot. And a method for producing the same.

[0002]

2. Description of the Related Art A silicon wafer used for a semiconductor device is mainly manufactured by slicing a single crystal ingot pulled from a polysilicon by a CZ method.

[0003] In the CZ method, polysilicon as a raw material supplied into a quartz crucible is heated and melted, and the tip of a seed crystal is brought into contact with the silicon melt to be blended. Then, a silicon single crystal ingot is grown and pulled up. Things.

[0004] In order to getter impurities such as heavy metals present on the crystal surface of the silicon wafer, a BMD (B
IG method (Intrinsic Getterin) using ULK Micro Defect (oxygen precipitate)
g) is used.

[0005] In recent years, the density of semiconductor devices has been increasing, and accordingly, low oxygen in silicon single crystal ingots has been required. On the other hand, the BMD in a silicon wafer manufactured from this silicon single crystal ingot is IMD
Although indispensable for the G method, BMD is reduced due to low oxygen.

[0006] Therefore, it has been practiced to dope nitrogen into the polysilicon melt to promote the precipitation of oxygen in the crystal of the silicon wafer. At the same time, nitrogen doping is performed on the silicon thus produced. When a wafer is subjected to a thermal oxidation process, an OSF (Oxidation
Induced Stacking Fault (Oxidation-Induced Stacking Fault) A ring-shaped oxidation-induced stacking fault called a ring is easily generated. This OSF ring changes its ring diameter strongly depending on the heat history during crystal growth, and the OSF ring diameter increases by increasing the cooling rate.
By reducing the cooling rate, the OSF ring diameter becomes smaller.

Further, by making the cooling rate sufficiently high, the OSF ring can be eliminated outside the wafer forming surface, and by making the cooling rate sufficiently slow, the OSF ring can be eliminated. Further, the OSF ring is also affected by the dopant and its concentration, and when nitrogen is doped at a certain concentration or more, the OSF ring is easily generated.

In the cooling process during the crystal growth, the temperature region in which the OSF nucleus, which is the source of the OSF, is formed during the crystal growth is expanded by doping the silicon melt with nitrogen. Pass, the experience time becomes longer, so that an OSF nucleus is easily formed.

For this reason, the OSF ring should be
Doping with nitrogen,
The cooling rate must be faster than when it is not
Absent. This depends on the nitrogen doping concentration and the crystal
The nitrogen concentration in the inside is 1.2 × 10 ^Fifteenatoms / cm³Less than
Appears prominently above.

Also, in the vicinity of the OSF ring, a BMD
There is a range in which the density is extremely low, the BMD density is extremely low, and the BMD density in the wafer surface becomes non-uniform. In this non-uniform part, the gettering ability is insufficient compared to other parts, and the predetermined gettering Ability is not obtained,
This has reduced the withstand voltage of the oxide film and reduced the yield of semiconductor devices.

Japanese Patent Application Laid-Open No. 5-294780 discloses a method of doping nitrogen into a polysilicon melt. The nitrogen doping can effectively suppress the generation of Secco etch pits. This does not eliminate the non-uniformity of the BMD density in the wafer surface caused by the OSF ring.

Further, Japanese Patent Application Laid-Open No. 11-116391 discloses that the time during which a silicon single crystal grown by low-speed pulling passes through a temperature range of 1150 to 1080 ° C. during crystal growth is set to 20 minutes or less, and the density of glow-in defects is reduced. The method relates to a method for manufacturing a silicon single crystal having an excellent non-defective rate of oxidation withstand voltage characteristics by simultaneously reducing the size and size of the silicon single crystal. However, the non-uniformity in the wafer surface of the BMD density due to the OSF ring in the nitrogen-doped silicon single crystal Does not eliminate the problem.

[0013]

Accordingly, in pulling a silicon single crystal ingot doped with nitrogen by the CZ method, a method of manufacturing a silicon single crystal ingot which eliminates in-wafer non-uniformity of BMD density due to an OSF ring. There is a need for a method.

The present invention has been made in view of the above-mentioned circumstances, and eliminates in-wafer non-uniformity of BMD density due to an OSF ring in pulling a silicon single crystal ingot doped with nitrogen by the CZ method. It is an object of the present invention to provide a method for producing a silicon single crystal ingot.

[0015]

Means for Solving the Problems According to the first aspect of the present invention, which has been made to achieve the above object, according to the present invention, polysilicon is doped from a silicon melt doped with nitrogen by using the Czochralski method, Nitrogen concentration is 1 × 10
^{13 to} 1.2 × 10 ¹⁵ atoms / cm ³ , the passing time of the temperature range of 1100 to 700 ° C. experienced by the crystal during crystal growth is set to 200 minutes or less, and the BMD density caused by the OSF ring is reduced. The gist of the invention is to provide a method for manufacturing a silicon single crystal ingot, which is characterized by eliminating non-uniformity in a wafer surface.

According to the second aspect of the present invention, the oxygen concentration in the crystal is 0.7 × 10 ^{18 to} 1.2 × 10 ¹⁸ atom.
The gist of the present invention is a method for producing a silicon single crystal ingot according to claim 1, wherein the method is s / cm ³ .

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a silicon single crystal ingot according to the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the CZ method used in the method for manufacturing a silicon single crystal ingot according to the present invention is as follows.
A quartz glass crucible 3 installed in a chamber 2 of a single crystal pulling apparatus 1 is filled with polysilicon as a raw material, and further,
As a dopant for doping nitrogen N, the nitrogen concentration during growth is 1 × 10 ^{13 to} 1.2 × 10 ^{15 at.}
ms / cm ³ , a predetermined amount of silicon nitride is added, and the oxygen concentration is a predetermined concentration, for example, the oxygen concentration is 0.7 × 1.
0 ^{18 to} 1.2 × 10 ¹⁸ atoms / cm ³ , the polysilicon is heated and melted by the heater 4 provided on the outer periphery of the quartz glass crucible 3, and then the silicon doped with nitrogen is melted. The seed crystal 7 attached to the seed chuck 6 is immersed in the liquid 5, and the seed chuck 7 is pulled up while rotating the seed chuck 7 and the quartz glass crucible 4 in the same direction or in the opposite direction at a predetermined number of revolutions, and the silicon single crystal ingot 8 is pulled up. Is grown and pulled up at a predetermined pulling rate. Further, in this growing step, the crystal being grown experiences 1100-700.
The time to pass through the temperature range of ° C. is set to 200 minutes or less.

The method of adjusting the oxygen concentration to a predetermined range as described above is a commonly used method, for example, controlling the crucible rotation speed, controlling the atmospheric pressure, controlling the flow rate of the introduced gas, controlling the silicon melt. By taking various measures for adjusting the temperature distribution and the convection of the gas, it can be easily performed. As described above, the oxygen concentration is set to 0.7 × 10 ^{18 to} 1.2.
By adjusting to × 10 ¹⁸ atoms / cm ³ ,
In addition to suppressing the growth of crystal defects, it is also possible to prevent the formation of BMD in the surface layer. In the bulk portion, since the presence of nitrogen promotes the precipitation of oxygen, even if the oxygen concentration is low, BMD can be uniformly and sufficiently precipitated, and formation of OSF can be suppressed.

As described above, the nitrogen concentration during growth is 1 × 10
^{13 to} 1.2 × 10 ¹⁵ atoms / cm ³ and an oxygen concentration of a predetermined concentration, preferably 0.7 × 10 ¹⁵ atoms / cm ^3.
18 was adjusted to ^{~1.2 × 10 18 atoms / cm 3} ,
Further, by making the time of passing through the temperature range of 1100 to 700 ° C. experienced by the growing crystal 200 minutes or less, even in the case of a silicon melt having a low oxygen concentration, oxygen doping can be performed by nitrogen doping. Promote OSF
The low concentration region of the BMD density generated near the ring shape can be improved, the BMD density can be made uniform in the plane, and the effect of reducing the content of impurities such as heavy metals by intrinsic gettering can be improved. Further, since pulling at a high speed is also possible, productivity of pulling a silicon single crystal can be improved.

[0021]

EXAMPLE 1 Test 1 : Using a silicon single crystal pulling apparatus as shown in FIG. 1, the nitrogen concentration during the growth was 1 × 10 5 by the silicon single crystal pulling method according to the present invention.
^{13 to} 1.2 × 10 ¹⁵ atoms / cm ³ and oxygen concentration of 0.7 × 10 ^{18 to} 1.2 × 10 ¹⁸ atoms / c
As m ^3, pulling up the silicon ingot having a diameter of 8 inches were examined for heterogeneity of BMD density. The pulling speed was changed as shown in Table 1 in order to change the time that the growing crystal experiences in passing through the temperature range of 1100 to 700 ° C.

(Results): The test results are shown in Table 1.

[0023]

[Table 1]

1100-70 experienced by the growing crystal
It was confirmed that the time required to pass through the temperature range of 0 ° C. was 200 minutes or less, and in Examples 1 and 2 in which the high-speed pulling was performed as compared with Comparative Examples 1 to 3, there was no unevenness in the BMD density. Was done. -On the other hand, more than 200 minutes, Example 1 and Example 2
In Comparative Examples 1 to 3 in which pulling was performed at a low speed, non-uniformity of the BMD density was confirmed.

[0025]

According to the method for manufacturing a silicon single crystal ingot according to the present invention, in pulling a silicon single crystal ingot doped with nitrogen by the CZ method, an OS
A method for manufacturing a silicon single crystal ingot capable of manufacturing a silicon single crystal ingot that eliminates non-uniformity of the BMD density in the wafer plane due to the F ring can be provided.

That is, it is pulled up from a silicon melt obtained by doping nitrogen into polysilicon using the Czochralski method, and the nitrogen concentration in the crystal is 1 × 10 ¹³ to 1 × 10 ¹³ .
2 × 10 ¹⁵ atoms / cm ^3, which is a method for producing a silicon single crystal ingot in which the passage time in the temperature range of 1100 to 700 ° C. experienced by the crystal during crystal growth is 200 minutes or less. The non-uniformity of the BMD density in the wafer surface can be eliminated, and the effect of reducing the content of impurities such as heavy metals by intrinsic gettering can be improved. Further, since pulling at a high speed is also possible, productivity of pulling a silicon single crystal can be improved.

The oxygen concentration in the crystal is 0.7 × 10
^{Since it is 18 to} 1.2 × 10 ¹⁸ atoms / cm ³ , a silicon single crystal ingot having a low oxygen concentration can be obtained, and the formation of OSF can be suppressed.
The non-uniformity of the BMD density in the wafer surface due to the ring can be eliminated.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a single crystal pulling apparatus used for pulling a silicon single crystal ingot according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon single crystal pulling apparatus 2 Chamber 3 Quartz glass crucible 4 Heater 5 Silicon melt 6 Seed chuck 7 Seed crystal 8 Silicon single crystal ingot N Nitrogen

Claims (2)

[Claims] 1. A silicon melt obtained by doping a polysilicon with nitrogen by a Czochralski method and having a nitrogen concentration of 1 × 10 ^{13 to} 1.2 × 1 in the crystal.
0 ¹⁵ atoms / cm ³ , and the passage time of the temperature range of 1100 to 700 ° C. experienced by the crystal during crystal growth is 2
00 minutes or less, and B due to the OSF ring
A method for producing a silicon single crystal ingot, wherein non-uniformity of MD density in a wafer surface is eliminated. 2. The oxygen concentration in the crystal is 0.7 × 10
^{18 ~1.2} × ^{10 1} 8 atoms / method for manufacturing a silicon single crystal ingot according to claim 1, wherein the cm ^3.