KR20030058714A - Thermal shield in Apparatus of growing a single crystalline silicon ingot and method for fabricating single crystalline silicon ingot using thereof - Google Patents

Abstract

PURPOSE: A heat shield of a silicon single crystal ingot growing apparatus and a method for manufacturing a silicon single crystal ingot using the same are provided to be capable of reducing the generation of growth defect by increasing the gradient of mean vertical temperature and effectively removing the defect due to oxygen precipitation. CONSTITUTION: A heat shield(104) is provided with a housing(104a) located in a silicon growing apparatus for surrounding a silicon single crystal ingot(106) and heat insulating material(104b) filled in the housing. The housing has the first tilt surface(108a) opposite to the silicon single crystal ingot, the horizontal surface(108b) opposite to a silicon melted solution(102), and the second tilt surface(108c) having a slope of 90-120 degree from the horizontal surface.

Description

Thermal shield in Apparatus of growing a single crystalline silicon ingot and method for fabricating single crystalline silicon ingot using according to the present invention.

The present invention relates to a heat shield of a silicon single crystal ingot growth apparatus and a method for manufacturing a silicon single crystal ingot using the same, in particular, by increasing the pulling speed of the silicon single crystal ingot to suppress the formation of the oxygen lamination defect nucleus and thereby depositing oxygen on the silicon wafer. To minimize the density of defects and to improve productivity.

Silicon single crystal ingots are prepared by melting polycrystalline silicon in a liquid phase and then growing the crystals by Czochralski (hereinafter, referred to as Czochralski) crystal growth method.

In crystal growth of a silicon single crystal ingot by the Czochralski method, the defect characteristics in the silicon single crystal ingot largely depend on the growth rate of crystal pulling and cooling. Therefore, many efforts have been made to control the type and distribution of crystal defects by controlling the thermal environment near the growth interface.

As the silicon melt is solid crystallized, point defects of vacancy type and interstitial type are mixed above the equilibrium concentration, and these defects aggregate and grow during cooling. Done. According to VVVoronkov (The mechanism of swirl defects formation in silicon "(Journal of crystal growth. Vol. 59 (1982). P, 625.,), the formation of these defects is closely related to the VG ratio. Where V is the pulling rate of the ingot and G is the vertical temperature gradient in the crystal near the growth interface.

In the above, when the ratio of V.G exceeds a certain threshold, a vacancy type crystal defect is generated, and below that, an interstitial type crystal defect is generated. Therefore, when growing a crystal using the apparatus for producing a single crystal ingot, under certain growth conditions of a predetermined hot zone, the kind, size and density of defects present in the crystal are affected by the pulling speed.

In general, the vertical temperature gradient (G) in the crystal is the smallest at the center of the ingot and increases radially toward the edge. Therefore, it is easy to form a vacancy-type crystal defect region in the center of the ingot, and the formation of an interstitial crystal defect region in the outer peripheral portion. These defects, such as COP, LDP, OSF is observed in the subsequent process.

Therefore, in order to suppress the occurrence of baconic type crystal defects at the center of crystal growth and interstitial type crystal defects at the outer periphery, the vertical temperature gradient deviation (G) of the single crystal ingot in the crystal radial direction, that is, the single crystal ingot The difference between the vertical temperature slope at the center and the vertical temperature slope at the outer periphery should be reduced and the average vertical temperature slope at the growth interface should be improved.

In order to reduce the vertical temperature gradient deviation (G) in the crystal radial direction of the single crystal ingot, it is necessary to increase the vertical temperature (Gc) slope of the center portion or lower the vertical temperature (Ge) slope of the outer peripheral portion.

However, decreasing the vertical temperature gradient deviation by lowering the vertical temperature (Ge) slope of the outer peripheral portion decreases the average vertical temperature slope of the single crystal ingot growth interface, thereby decreasing the growth rate (V) of the single crystal ingot.

Therefore, much effort has been focused on the development of a single crystal ingot manufacturing apparatus for reducing the occurrence of crystal defects and improving the growth rate, particularly a heat shield directly affecting the thermal environment of the growth interface.

1 is a schematic cross-sectional view of an apparatus for producing a single crystal ingot according to the prior art.

The apparatus for manufacturing a single crystal ingot according to the prior art is provided with a quartz crucible 14 containing a silicon melt 12 in a chamber 10. The quartz crucible 14 is supported by a crucible support 16 made of graphite outside. The crucible support 16 is fixedly installed on the rotating shaft 18, and the rotating shaft 18 is rotated by a driving means (not shown) to rotate the quartz crucible 14.

The crucible support 16 is enclosed by a cylindrical heater 20 at predetermined intervals, and the heater 20 is enclosed by a thermos 22. The heater 20 melts a high purity polycrystalline silicon mass in the quartz crucible 14 to form a silicon melt 12.

A pulling means (not shown) for winding up the cable 24 is provided on the upper portion of the chamber 10, and the pulling means is rotated. A seed crystal 26 is provided below the cable 24 to grow in contact with the silicon melt 12 in the quartz crucible 14 to grow the silicon single crystal ingot 28.

A heat shield 30 is provided between the silicon single crystal ingot 28 and the quartz crucible to be grown. The heat shield 30 is a silicon melt 12 contained in the quartz crucible 14 at a high temperature to release the heat at the interface of the silicon melt 12 when a large amount of heat is released, the temperature of the silicon melt required for ingot growth It is formed for thermal insulation because it is difficult to maintain.

One side of the heat shield 30 is fixed to the shield 22 in the silicon single crystal growth apparatus, and the other side of the heat shield is formed to be close to the interface of the silicon melt 12.

One side of the shielding part 22 is connected to the heat shield 30 to fix the heat shield, and the other side of the shielding part 22 is connected to and fixed to the thermos 22.

FIG. 2 is a diagram illustrating a distribution of thermal history of a silicon single crystal ingot growth apparatus according to the prior art. When a silicon single crystal ingot is grown using a silicon single crystal ingot growth apparatus as shown in FIG. 2, an oxygen stacking defect is formed at a temperature. The vertical temperature gradients Gc and Ge at 1073 to 1,343 K are small as shown in Table 1.

In addition, when the pulling speed of the silicon single crystal ingot was pulled at a speed of 0.9 mm / min, which is a normal pulling speed, as shown in FIG. 3, the density of oxygen lamination defects was high, such as ²⁰⁰ to 10,000 pieces / cm ² or more.

Table 1

(K / cm)

(G2: Temperature gradient in the range of 1,073-1,343K)

As another method for reducing such oxygen lamination defects, in order to control oxygen lamination defects in Japanese Patent Application Laid-open No. 5-58800, which is already known, silicon single crystal ingots are grown to less than 2 mm within 10 days or a low temperature of 243 K or less. Suggested storage method.

However, such a method does not remove the oxygen lamination defect core, which is the cause of the oxygen lamination defect, but has a problem that cannot be a fundamental solution by preventing the growth of the already grown nucleus.

In addition, in order to store the silicon single crystal ingot at a low temperature of less than 243K, an expensive low temperature storage is required, and a large maintenance cost is generated to maintain it, and there is a time problem of cutting the stored silicon single crystal ingot within 10 days.

Therefore, the present invention has been proposed to solve the above problems, the storage period and storage temperature of the silicon single crystal ingot manufacturing apparatus and the silicon single crystal ingot manufacturing apparatus for reducing the occurrence of growth defects by increasing the average vertical temperature gradient of the grown silicon single crystal ingot It is an object of the present invention to provide a heat shield of a silicon single crystal ingot growth apparatus capable of producing a silicon single crystal ingot effectively removing oxygen lamination defects without resorting to the above, and a method of manufacturing a silicon single crystal ingot using the same.

The heat shield according to the present invention for achieving the above object has a longitudinal axis and comprises a housing mounted in the silicon growth apparatus to surround the silicon single crystal ingot growing at the crystallization interface, and a silicon made of a heat insulating material filled in the housing In the heat shield of a single crystal ingot growth apparatus, the housing is a first inclined surface facing the silicon single crystal ingot and inclined at a predetermined angle, a horizontal surface facing the silicon melt, and a first inclined at a predetermined angle connected to one end of the horizontal surface. It is characterized by consisting of two inclined surfaces.

In addition, the method for producing a silicon single crystal ingot for achieving the above object is a method for growing a silicon single crystal ingot by the Czochralski method, which is 18 to 25K at a temperature range of 1,073 to 1,343K in the temperature gradient in the silicon single crystal ingot growth apparatus. The temperature gradient of / cm is maintained, and the silicon single crystal ingot is grown by maintaining the pulling speed of the silicon single crystal ingot at 1.2 ~ 1.3mm / min.

The temperature gradient of the silicon single crystal ingot is preferably adjusted by a heat shield provided inside the growth device of the silicon single crystal ingot, which consists of a first inclined plane, a horizontal plane, and a second inclined plane.

1 is a cross-sectional view schematically showing a silicon single crystal ingot growth apparatus according to the prior art.

Figure 2 shows the thermal history distribution of the silicon single crystal ingot growth apparatus according to the prior art.

Figure 3 is an optical microscope photograph of the oxygen lamination defect according to the prior art.

4 is a cross-sectional view schematically showing a heat shield of a silicon single crystal ingot growth apparatus according to the present invention.

5 is a diagram showing a thermal history distribution of a silicon single crystal ingot growth apparatus according to the present invention.

Figure 6 is an optical microscope photograph of the oxygen lamination defects according to the present invention.

※ Description of main parts of drawing ※

100: quartz crucible 102: silicon melt

104a: housing 104b: insulation

104: heat shield 106: silicon single crystal ingot

108a: first inclined plane 108b: horizontal plane

108c: second slope

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 4 shows a schematic view of the longitudinal cross section of the silicon single crystal ingot, which is symmetrical with respect to the longitudinal axis direction of the silicon single crystal ingot, showing only half of the right side.

The heat shield of the silicon single crystal ingot growth apparatus according to the present invention has a longitudinal axis and includes a housing 104a mounted in the silicon growth apparatus to surround the silicon single crystal ingot growing at the crystallization interface, and a heat insulating material filled in the housing 104a. In the heat shield 104 of a silicon single crystal ingot growth apparatus comprising a 104b, the housing 104 is opposed to a silicon single crystal ingot and inclined at an angle to the first inclined surface 108a and to the silicon melt. And a second inclined surface 108c connected to one end of the horizontal plane and inclined at a predetermined angle.

More specifically, the first inclined plane 108a is formed from the longitudinal axis of the silicon single crystal ingot so as to provide a path for the camera accurately installed outside the chamber to observe the growth state of the silicon single crystal ingot at the interface of the silicon melt. It is formed to be inclined at 20 to 30 degrees which is a certain angle (a).

The horizontal surface 10b is formed to be as close as possible to the silicon melt 102 to maximize the thermal insulation effect, but is preferably located at a height of 20 to 30 mm.

The second inclined surface 108c is formed such that the angle b formed in contact with the horizontal surface 108b is 150 degrees or more. If the angle (b) is formed smaller than this, the effect of insulating heat released from the silicon melt is reduced.

In addition, the distance T1 between the second inclined surface 108c and the heat insulator 104b and the distance T2 between the horizontal plane 108b and the heat insulator 104b may be formed to maximize the thermal insulation effect, but preferably 10 It is formed at -42 mm.

However, the distance T3 between the first slope 108a and the heat insulator 104b is narrowly formed on the second slope 108c and the horizontal plane 108b because the distance T3 between the first slope 108a and the heat insulator 104b must be provided.

The housing 104a is preferably made of graphite, and the heat insulating material 104b preferably uses low density carbon fiber.

More preferably, the housing 104a is formed of graphite having a thermal conductivity of 30 to 50 W / mK and a density of 1.5 to 2.0 g / cm ³ , and the heat insulating material 104b has a thermal conductivity of 0.15 to 0.6 at 1,273 K and 1,773 K. Is preferably from 0.2 to 0.8 and the density is from 0.12 to 0.25 g / cm ³ .

Then, in order to manufacture the silicon single crystal ingot using the silicon single crystal ingot growth apparatus including the heat shield according to the present invention, first, the thermal history and temperature gradient of the silicon single crystal ingot growth apparatus including the heat shield according to the present invention are simulated. Check it.

Table 2 is a table showing the temperature gradient computer simulation data in the oxygen deposition defect nucleus growth temperature range (1,073-1,343K), Table 3 is the table showing the distance from the solid-liquid interface to the temperature shown on the horizontal axis, Table 4 Is a table which shows the temperature gradient in each temperature range from G1 to G9.

Table 2

(K / cm)

As shown in Table 2, it can be seen that the temperature gradients of the edge portion and the center portion of the silicon single crystal ingot are significantly larger than the average temperature gradient of 15K / cm above 18K / cm.

Table 3

(cm)

Table 4

(K / cm)

G1: 1,412-1,400 (K) G2: 1,400-1,300 (K)

G3: 1,300-1,200 (K) G4: 1,200-1,100 (K)

G5: 1,100 to 1,000 (K) G6: 1,000 to 900 (K)

G7: 900 to 800 (K) G8: 800 to 700 (K)

G9: 700 to 600 (K)

The thermal history distribution of the silicon single crystal ingot growth apparatus is shown in FIG. 5 with reference to the computer simulation data described above.

As shown in FIG. 5, the interval of the contour lines between 1,073 and 1,343K belonging to the temperature range where the oxygen deposition defects are formed is narrower than that of the thermal history distribution according to the related art of FIG. Narrow contours mean a larger temperature gradient.

Then, the silicon single crystal ingot is grown by the Czochralski method in the silicon single crystal ingot growth apparatus according to the present invention capable of thermal history and temperature gradient described above.

At this time, the temperature gradient in the temperature range in which the oxygen lamination defects are formed can be maintained at 18 to 25 K / min. Thus, the pulling speed of the silicon single crystal ingot is increased to 1.2 mm / min or higher than the conventional 0.9 mm / min. This was possible.

Preferably, it is most preferable to grow a silicon single crystal ingot in the range of 1.2 to 1.3 mm / min.

Figure 6 is a silicon single crystal ingot growth apparatus according to the present invention after processing the silicon single crystal ingot grown at a pulling speed of 1.2 ~ 1.3mm / min with a silicon wafer, the oxygen formed on the surface after the heat treatment for measuring the oxygen deposition defects It is an optical microscope photograph of lamination defects.

The heat treatment at this time was performed at 1,373K for 120 minutes.

As shown in Figure 6 it can be seen that the density of the oxygen stacking defect much reduced compared to the conventional 200 ~ 10,000 pieces / cm ² appeared to 10 / cm ² or less.

As described above, the present invention can change the structure of the heat shield of the silicon single crystal ingot growth apparatus to maintain a temperature gradient of 1,073 to 1,343K, which is the formation temperature range of the oxygen lamination defect, to 18 K / cm or more. Can increase the speed of hike. Therefore, the productivity of the silicon single crystal ingot is also improved.

In addition, the density of oxygen lamination defects formed in the silicon single crystal ingot can be significantly reduced, so that the silicon single crystal ingot or block can be stored for a long time without depending on external influences such as storage type, storage temperature, and storage period.

And since the additional costs do not occur according to the conventional storage can reduce the production cost.

Claims (9)

A heat shield of a silicon single crystal ingot growth apparatus, comprising a housing mounted in a silicon growth apparatus and having a longitudinal axis and surrounding a silicon single crystal ingot growing at a crystallization interface, and an insulating material filled in the housing. The housing and the first inclined surface facing the silicon single crystal ingot and inclined at an angle, With the horizontal plane opposite the silicon melt, The heat shield of the silicon single crystal ingot growth apparatus, characterized in that the second inclined surface is inclined at a predetermined angle connected to one end of the horizontal plane. The method of claim 1, The heat shield of the silicon single crystal ingot growth apparatus, wherein the distance (D) between one point where one end of the first inclined plane and one end of the horizontal plane meet and the outer circumferential edge of the silicon single crystal ingot is 20 to 30 mm. The method of claim 1, The distance (T1) between the second inclined plane and the heat insulator and the distance (T2) between the horizontal plane and the heat insulator is 10 to 42mm, the heat shield of the silicon single crystal ingot growth apparatus. The method of claim 1, The first inclined surface is a heat shield of the silicon single crystal ingot growth apparatus, characterized in that formed inclined 20 to 30 degrees from the longitudinal axis of the silicon single crystal ingot. The method of claim 1, And the second inclined surface is inclined at an angle of 90 to 120 degrees with a horizontal plane. The method of claim 1, And said horizontal plane is located at a height (H) of 20 to 30 mm from the silicon melt. The method of claim 1 The housing is formed of graphite, the heat insulating material is a heat shield of the silicon single crystal ingot growth apparatus, characterized in that the carbon fiber. In the method for producing a silicon single crystal ingot having a longitudinal axis and using the Czochralski method for growing a silicon single crystal ingot at the crystallization interface, Among the temperature gradients in the silicon single crystal ingot growth apparatus, the temperature gradient of 18 to 25 K / cm is maintained at the temperature range of 1,073 to 1,343 K, and the silicon single crystal ingot is grown by maintaining the pulling speed of the silicon single crystal ingot at 1.2 to 1.3 mm / min. Method for producing a silicon single crystal ingot, characterized in that. The method of claim 8, The temperature gradient of the silicon single crystal ingot consists of a first inclined plane, a horizontal plane and a second inclined plane is a silicon single crystal ingot manufacturing method characterized in that it is adjusted by a heat shield installed inside the growth apparatus.