JP2002226291A - Quartz crucible - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a quartz crucible which can always maintain nitrogen content in a drawn silicon single crystal ingot homogenously even for different amount of charge, can control the nitrogen content in the ingot and can grow the nitrogen-doped ingot simply. SOLUTION: A silicon nitride film with a thickness of 0.01-5 μm is formed on an inner surface, which comes into contact with a silicon melt, of the quartz crucible for growing the silicon single crystal ingot in accordance with a Czochralski method. The first silicon nitride film 11 with a thickness of tA (0.015-5 μm) is homogeneously formed on the inner surface of a cylindrical wall 10a of the crucible body part 10. The second silicon nitride film 12 with a thickness of tB (0.01-2 μm) which is thinner than tA is homogeneously formed on the inner surface of a bottom part 10b linking to the wall 10a of the crucible body part 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a quartz crucible used for growing a silicon single crystal ingot based on the Czochralski method (hereinafter referred to as CZ method). More specifically, the present invention relates to a quartz crucible used for growing a nitrogen-doped silicon single crystal ingot.

[0002]

2. Description of the Related Art In the CZ method, silicon is melted in a crucible made of amorphous quartz glass, and a seed crystal touching the upper surface of the silicon melt is pulled upward while gently rotating. The melt that touches the seed crystal loses heat through the seed crystal and precipitates according to the crystal orientation of the seed crystal when solidifying on the seed crystal,
Pulled up as a single crystal ingot. Therefore, in the CZ method, a part of the quartz glass in the crucible that comes into contact with the silicon melt is inevitably dissolved in the silicon melt, thereby dissolving oxygen into the melt. It is the largest impurity. The silicon single crystal ingot grown by this method has 10 ¹⁷ to 10 ¹⁸ at
oms / cm ³ of oxygen is contained as an impurity.

[0003] Impurity oxygen has a great effect on the mechanical strength of silicon wafers, heat treatment induced defects, and internal gettering. Primarily, silicon single crystal ingots grown by the CZ method are used in the manufacture of IC devices because of their superior mechanical strength due to impurity oxygen. This is due to the inherent dislocation fixation of oxygen. However, there is a phenomenon that when impurity oxygen in the single crystal ingot precipitates, the single crystal ingot rapidly becomes weak to thermal stress. Possible causes include a decrease in the interstitial oxygen concentration that causes the dislocation to be fixed, and the fact that oxygen precipitates act as a stress concentration source to facilitate the generation of dislocations.

[0004] Particles originating from crystals (Crystal Originated Particles, hereinafter referred to as COPs) are also generated on the surface of the wafer cut from the silicon single crystal ingot. Here, when the silicon wafer after mirror polishing is washed with a mixed solution of ammonia and hydrogen peroxide, pits are formed on the wafer surface, and when this wafer is measured with a particle counter, the pits are detected as particles together with the original particles. This is a defect caused by the crystal. This COP has electrical properties,
For example, the time-dependent dielectric breakdown characteristics of an oxide film (Time Dependent Die
electrical breakdown (TDDB), oxide breakdown voltage characteristics (Tim
e Zero Dielectric Breakdown (TZDB) and the like. Also, if the COP exists on the wafer surface, a step is generated in a device wiring process, which may cause disconnection. This also causes a leak and the like in the element isolation portion, and lowers the product yield.

As a method for solving the above problems, a method for producing a silicon single crystal ingot doped with nitrogen has been disclosed (JP-A-60-251190). In this method, nitrogen atoms are added to a single crystal by growing a silicon single crystal ingot by mixing a small amount of nitride in a melt of polycrystalline silicon, which is a raw material of the silicon single crystal ingot. Thereby, a silicon single crystal ingot in which the deterioration of crystallinity due to thermal stress is suppressed can be obtained. The wafer cut from the nitrogen-doped silicon single crystal ingot is sufficiently suppressed in the occurrence of crystal defects, resistant to thermal stress during the semiconductor device manufacturing process, and has a small nitrogen doping amount. It does not affect the electrical characteristics.

In a method of doping nitrogen into a silicon single crystal ingot, polycrystalline silicon mixed with a nitrogen compound or polycrystalline silicon formed with a silicon nitride film is charged into a quartz crucible and a silicon melt containing nitrogen is introduced. A method of pulling a silicon single crystal ingot, a method of growing a single crystal while flowing a nitrogen or nitrogen compound gas into a pulling furnace, a method of spraying a nitrogen or nitrogen compound gas on a raw material at a high temperature before melting, and a method of manufacturing a nitride. There are methods such as using a crucible.

[0007]

However, it is necessary to adjust the amount of polycrystalline silicon charged into the quartz crucible depending on the pulling conditions of the single crystal ingot. In order to obtain an ingot, it was necessary to adjust the nitrogen doping amount according to the charge amount charged into the quartz crucible.

An object of the present invention is to provide a quartz crucible capable of always making the concentration ratio of nitrogen contained in a pulled single crystal ingot constant even at different charge amounts. Another object of the present invention is to provide a quartz crucible capable of controlling the amount of nitrogen contained in a grown single crystal ingot. Still another object of the present invention is to provide a quartz crucible capable of easily growing a nitrogen-doped single crystal ingot.

[0009]

The invention according to claim 1 is
As shown in FIG. 1, in a bottomed cylindrical quartz crucible used for growing a silicon single crystal ingot based on the CZ method, an inner surface 1 of a crucible in contact with a silicon melt.
This is a quartz crucible characterized in that silicon nitride films 11 and 12 having a thickness of 0.01 to 5 μm are formed on Oa and 10b. In the invention according to the first aspect, since the silicon nitride film having a thickness of 0.01 to 5 μm is formed on the inner surface of the crucible that comes into contact with the silicon melt, nitrogen is always dissolved in the silicon melt, so that the amount of nitrogen contained in the melt is constant. Can be kept in the range,
Using this silicon melt as a raw material, a silicon single crystal ingot uniformly doped with nitrogen can be grown. The thickness of the silicon nitride film is 0.01 to 5 μm. Preferably 0.04
２2 μm. When the thickness is less than 0.01 μm, the growth of crystal defects formed in the single crystal ingot cannot be sufficiently suppressed, and when the thickness exceeds 5 μm, the electric characteristics of the single crystal ingot deteriorate.

The invention according to claim 2 is the invention according to claim 1, wherein the first silicon nitride film 11 has a thickness t _A on the inner surface of the cylindrical peripheral wall 10a of the crucible body 10, as shown in FIG.
In uniformly formed, a quartz crucible second silicon nitride film 12 is uniformly formed with a thickness t _A is less than the thickness t _B in the bottom 10b inner surface following the circumferential wall 10a of the crucible body 10. In the invention according to claim 2, the first silicon nitride film is formed uniformly on the inner surface of the cylindrical peripheral wall of the crucible body with a thickness t _A ,
A second silicon nitride film having a thickness t is formed on the inner surface of the bottom portion following the peripheral wall.
Uniformly formed at _A smaller thickness t _B. As described above, the thickness t _A of the first silicon nitride film and the thickness t _B of the second silicon nitride film are different from each other, and the silicon nitride film is formed such that the relationship of t _A > t _B is satisfied. Thereby, the concentration ratio of nitrogen contained in the pulled single crystal ingot can be always kept uniform even with different charge amounts.

The invention according to claim 3 is the invention according to claim 2, wherein the first silicon nitride film has a thickness t _A of 0.01.
This is a quartz crucible having a thickness of 5 to 5 μm and a thickness t _B of the second silicon nitride film of 0.01 to 2 μm. In the invention according to claim 3, the thickness t _A is 0.015 to 5 μm, depending on the size of the crucible and the growth condition of the silicon single crystal ingot.
m and the thickness t _B are 0.01 to 2 μm.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The quartz crucible of the present invention is suitable for a crucible having an inner diameter of 15 to 50 cm. The quartz crucible of the present invention has a thickness of 0.01 mm on the inner surface of the crucible in contact with the silicon melt.
A silicon nitride film having a thickness of about 5 μm is formed. In the CZ method, since the silicon melt and the quartz crucible come into contact with each other, a part of the contact surface is inevitably dissolved in the silicon melt. Since the silicon nitride film was formed on the inner surface in contact with the silicon melt at a thickness of 0.01 to 5 μm, the ingot was grown even before the silicon single crystal ingot was grown.
Even if the silicon melt becomes small, the amount of nitrogen in the silicon melt stored in the quartz crucible can be reduced to 5 × 10 ^{12 to} 5 × 10 ^{14 at.}
It can always be kept within the range of ms / cm ³ .

This 5 × 10¹²~ 5 × 10¹⁴atoms /
cm^ThreeGrown using a silicon melt containing nitrogen
The amount of nitrogen doping contained in the obtained single crystal ingot is 5 × 10
¹²~ 5 × 10¹⁴atoms / cm^ThreeWithin the range. single
Nitrogen doping of crystal ingot is 5 × 10¹²atoms
/ Cm^ThreeIf less than, it will be formed into a single crystal ingot
The growth of crystal defects cannot be sufficiently suppressed. Nitrogen doping amount
5 × 10¹⁴atoms / cm^ThreeA simple bond that has grown up
The electrical properties of the crystal ingot deteriorate and the nitrogen doping
Is 5 × 10^Fifteenatoms / cm^ThreeExceeds
Saturated and Si_ThreeN _FourAs a single crystal ingot
Inhibit the growth of Doping nitrogen concentration is 5 × 10¹²
~ 5 × 10¹⁴atoms / cm^ThreeIs preferably within the range.
More preferably 3 × 10¹³~ 3 × 10¹⁴atoms / c
m^ThreeIs within the range.

When nitrogen is doped into a silicon single crystal ingot, aggregation of atomic vacancies in silicon is suppressed, and the size of crystal defects is reduced. This effect is considered to be due to the transition of the process of aggregation of atomic vacancies from the formation of uniform nuclei to the formation of heterogeneous nuclei. Therefore, by doping with nitrogen, the growth of crystal defects introduced during crystal growth can be suppressed, and the size of the introduced crystal defects can be very small. Therefore, the effect of reducing the voids caused by the voids and the effect of shortening the heat treatment time required for eliminating COPs and voids can be obtained. In addition, by doping with nitrogen, the solid solubility of the vacancies generated in the single crystal ingot is increased to suppress the disappearance of the vacancies, and a large amount of oxygen precipitates in the silicon single crystal ingot using the vacancies. Generate nuclei. This oxygen precipitation nucleus can exhibit the effect of internal gettering.

Further, a thickness t is formed on the inner surface of the cylindrical peripheral wall of the crucible body.
_A(0.015 to 5 μm) uniform first silicon nitride film
And a thickness t on the bottom inner surface following the peripheral wall of the crucible body._A
Smaller thickness t_B(0.01-2 μm) second silicon nitride
By forming a uniform recon film, it can be included in the ingot.
The nitrogen concentration can be set within a strict concentration range. thickness
t_BIs the thickness t_AAs it gets bigger, ingots can be raised
Therefore, when the amount of silicon melt decreases, the nitrogen concentration
It may increase. Therefore, the thickness t _AAnd thickness
t_BIs t_A> T_BAnd 0.01 μm ≦ t_B<
t_A≦ 5 μm.

As shown in FIG. 1, a first silicon nitride film 11 is formed on the inner surface of the cylindrical peripheral wall 10a of the crucible body 10 to a thickness t _A.
The second silicon nitride film 12 is formed to a thickness t _A on the inner surface of the bottom 10 b following the peripheral wall 10 a of the crucible body 10.
It is formed uniformly with a smaller thickness t _B. At this time, the inner surface area of the inner surface of the cylindrical peripheral wall is S _A , the volume of the first silicon nitride film uniformly formed with the thickness t _A is V _A , the inner surface area of the bottom inner surface is S _B , and the thickness t _B is uniform. the volume of the second silicon nitride film when V _B formed in the crucible cylindrical inner surface of the peripheral wall and the bottom first and second identical per unit volume if the silicon nitride film is melted into the silicon melt are formed on the inner surface In order to obtain a nitrogen concentration of

[0017]

(Equation 1) It is represented by Accordingly, the thickness t _A and the thickness t _B are expressed by the following equation (2):

[0018]

(Equation 2) Where S _B / S _A = x and V _B / V _A = y,
Equation (2) is represented by the following equation (3).

[0019]

(Equation 3) Since x and y each take a constant value depending on the size of the crucible, the thickness t of the first silicon nitride film formed on the inner surface of the peripheral wall is set.
The thickness of the second silicon nitride film formed on the inner bottom surface by setting the _A t _B is also determined.

Next, a method for manufacturing the quartz crucible of the present invention will be described. When a silicon nitride film is formed on the inner surface of a quartz crucible, a chemical vapor deposition (CVD) method is used.
or Deposition), physical vapor deposition (PVD)
por Deposition) and a plasma spraying method. For example, when a silicon nitride film is formed by a CVD method, first, the crucible is kept in an NH ₃ atmosphere and Si
By supplying H ₄ and raising the temperature to 700 to 900 ° C. to cause thermal decomposition, a silicon nitride film is formed on the inner surface to a thickness t _B. Then a mask is inner bottom surface with a resist, and then forming the film forming method and the thickness t _A to the silicon nitride film on a cylindrical inner surface of the peripheral wall of the crucible are in the same manner. Finally, by removing the resist, as shown in FIG. 1, the first silicon nitride film 11 having a thickness of t _A is formed on the inner surface of the cylindrical peripheral wall 10a.
It is a second quartz crucible 10 in which the silicon nitride film 12 are formed respectively in the thickness in the bottom 10b the inner surface of t _A is less than the thickness t _B.

[0021]

Next, examples of the present invention will be described together with comparative examples. Example 1 First, a quartz glass crucible having an inner diameter of 29.3 cm was prepared. In this quartz crucible, a first silicon nitride film was formed on the inner surface of the cylindrical peripheral wall by 0.01 μm, and a second silicon nitride film was formed on the inner surface of the bottom by 0.005 μm by the above-described method for forming a silicon nitride film. Next, the quartz crucible was filled with polycrystalline silicon, and the filled polycrystalline silicon was heated to 1415 ° C. and melted in an inert gas. Next, the seed crystal was gently brought into contact with the upper surface of the melted silicon melt, and was pulled upward while rotating the seed crystal to grow a single crystal ingot having a charge amount of 100 kg. Example 2 Charge amount of single crystal ingot was 150 k
A single crystal ingot was grown in the same manner as in Example 1 except that g was used.

Comparative Example 1 The first silicon nitride film was
A single crystal ingot was grown in the same manner as in Example 1 except that a quartz crucible having a thickness of 1 μm and a second silicon nitride film of 0.005 μm was used. Comparative Example 2 A single crystal ingot was grown in the same manner as in Example 1 except that a quartz crucible having a first silicon nitride film of 10 μm and a second silicon nitride film of 5 μm was used.

<Comparative Evaluation> Examples 1 and 2 and Comparative Examples 1 and 2
In the crystal top part of the single crystal ingot grown in 2
The nitrogen concentration was measured. Table 1 shows the respective nitrogen concentrations.
In Table 1, t _AIs the thickness of the first silicon nitride film, t_BIs
The thickness of the second silicon nitride film is shown.

[0024]

[Table 1]

As is clear from Table 1, Comparative Examples 1 and 2
The concentration of nitrogen contained in the single crystal ingot grown using the quartz crucible is 5 × 10 ^{12 to} 5 × 10 ¹⁴ atoms / c.
It had been outside the range of m ^3. Therefore, in the ingot grown in Comparative Example 1, the growth of crystal defects formed in the ingot cannot be sufficiently suppressed, and in the ingot grown in Comparative Example 2, the electrical properties of the ingot deteriorate. On the contrary,
In Examples 1 and 2, 5 × 10 ^{12 to} 5 × 10 ¹⁴ atoms
/ Cm ³ , and the use of this single crystal ingot can suppress the deterioration of crystallinity due to thermal stress. Further, even when the thickness t _A and the thickness t _{B of the} silicon nitride film formed in the quartz crucible were formed to the same thickness in Examples 1 and 2 having different amounts of charge to be pulled, the nitrogen in the single crystal ingot remained By using the quartz crucible of the present invention having the same concentration, the same concentration of nitrogen can be doped even when pulling a single crystal ingot with different charge amounts.

[0026]

As described above, according to the present invention, even if the amount of the silicon melt changes due to the pulling of the silicon single crystal ingot, the ratio of the nitrogen contained in the melt is always within a certain range. _A first silicon nitride film having a thickness of 0.01 to 5 μm on the inner surface of the crucible that comes into contact with the silicon melt, specifically, a first silicon nitride film having a thickness tA of 0.0
Uniformly formed in 15～5Myuemu, since the thickness t _A is less than the thickness t _B of the second silicon nitride film on the inner bottom surface following the circumferential wall is uniformly formed at 0.01 to 2 [mu] m, using this quartz crucible This makes it possible to easily grow a nitrogen-doped single crystal ingot and to control the nitrogen doping amount of the grown silicon single crystal ingot.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a quartz crucible of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Quartz crucible 10a Cylindrical peripheral wall part 10b Bottom part 11 1st silicon nitride film 12 2nd silicon nitride film

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hitoshi Sasaki 1-5-1, Otemachi, Chiyoda-ku, Tokyo Mitsubishi Materials Silicon Co., Ltd. F-term (reference) 4G077 AA02 BA04 CF10 EG02 PD05

Claims (3)

[Claims] 1. A bottomed cylindrical quartz crucible used for growing a silicon single crystal ingot based on the Czochralski method, wherein the inner surface (10a, 10b) of the crucible in contact with the silicon melt has a thickness of 0.1 mm. A quartz crucible characterized in that a silicon nitride film (11, 12) of 01 to 5 μm is formed. 2. A first silicon nitride film (11) having a thickness t _A is uniformly formed on an inner surface of a cylindrical peripheral wall (10a) of a crucible body (10), and is formed on a peripheral wall (10a) of the crucible body (10). continued bottom (10b) inner surface to a second quartz crucible according to claim 1, wherein the silicon nitride film (12) is uniformly formed with a thickness t _B the smaller thickness t _a. 3. The first silicon nitride film (11) having a thickness t _A of 0.015 to 5 μm and a second silicon nitride film (12)
Quartz crucible according to claim 2, wherein the thickness t _B is 0.01 to 2 [mu] m.