JPH0782084A - Single crystal growing method and single crystal growing apparatus - Google Patents

Abstract

PURPOSE:To suppress the growth of an oxygen deposit and improve the quality of a single crystal by providing an apparatus for cooling a heat-shielding member placed above a crucible for Czochralski process, thereby quenching the grown Si single crystal within a prescribed temperature range. CONSTITUTION:A heat-shielding member 21 and a quenching apparatus 23 for the shielding member are placed above a crucible 11 in a process for growing an Si single crystal 14 by pulling up the single crystal from a molten liquid 12 in a crucible 11. The grown Si single crystal is quenched with the quenching apparatus 23 within the temperature range of 1200-700 deg.C. The above temperature range to generate and grow an oxygen deposit is shortened by this process to suppress the growth of the oxygen deposit. An Si single crystal having high quality is produced because the present process suppresses the generation of an oxygen-induced substrate failure(OSF) in the heat-treatment of the single crystal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single crystal growing method and a single crystal growing apparatus, and more particularly to a single crystal growing method and a single crystal capable of growing a high quality Si single crystal used as a semiconductor material. Regarding growth equipment.

[0002]

2. Description of the Related Art There are various methods for growing a single crystal, one of which is the Czochralski method (hereinafter referred to as the CZ method). FIG. 6 is a cross-sectional view schematically showing a single crystal growth apparatus used in the conventional CZ method, and 31 in the figure shows a crucible.

The crucible 31 is composed of a bottomed cylindrical quartz inner layer holding container 31a and a bottomed cylindrical graphite outer layer holding container 31b fitted on the outside of the inner layer holding container 31a. The crucible 31 is supported by a support shaft 38 that rotates at a predetermined speed in the direction of the arrow in the figure. A resistance heating type heater 32 is provided outside the crucible 31.
However, the heat insulating cylinders 37 are arranged concentrically outside the heater 32, and the heater 32 is provided inside the crucible 31.
It is filled with the melt 33 of the crystal raw material melted by. Further, a pulling shaft 34 made of a pulling rod or a wire is hung on the central axis of the crucible 31, and a seed crystal 35 attached to the tip of the pulling shaft 34 via a seed chuck 34a is melted 33 Is brought into contact with the surface of the support shaft 38, and the pulling shaft 34 is pulled up while rotating in the same direction as the support shaft 38 in the same direction or in the opposite direction at a predetermined speed, thereby solidifying the melt 33 and growing the single crystal 36. .

By the way, when the semiconductor single crystal 36 is pulled by this pulling method, in order to adjust the electric resistivity and electric conductivity type of the single crystal 36, the melt 33 is pulled before the pulling.
Impurities are often added to the inside. However, in the ordinary CZ method, a single crystal 36 having a uniform electric resistivity in the growth axis direction of the single crystal 36 cannot be obtained due to a so-called segregation phenomenon occurring between the single crystal 36 and the melt 33. There was a problem.

The segregation phenomenon means that the single crystal 3 is solidified at the interface between the single crystal 36 and the melt 33 during solidification of the single crystal 36.
It means that the impurity concentration taken in 6 and the impurity concentration in the melt 33 do not match, but the effective segregation coefficient Ke
The (impurity concentration in single crystal 36 / impurity concentration in melt 33) is often less than 1. In this case, the single crystal 36 grows and the melt 3 is melted due to the segregation phenomenon.
Since the impurity concentration in 3 gradually increases, the impurity concentration in the single crystal 36 also gradually increases, and the electric resistance decreases. Therefore, in the single crystal 36 grown by the above method,
A part of the product that does not meet the standard with respect to the electrical resistivity is manufactured, resulting in a low yield.

Therefore, a melt layer method has been developed as a single crystal pulling method for preventing a decrease in yield due to the occurrence of the above-mentioned segregation phenomenon and increasing the yield related to the electrical resistivity.

FIG. 7 is a sectional view schematically showing a single crystal growth apparatus used in the melt layer method. The basic characteristic of this melting layer method is that the raw material for crystallization in the crucible 31 having the same structure as that shown in FIG.
The molten layer 43 is formed on the upper layer, and the solid layer 49 is formed on the lower layer.
The solid layer 49 is gradually eluted with the growth of the single crystal to keep the impurity concentration in the molten layer 43 constant. The configuration of the other parts of the apparatus is the same as that of the apparatus used in the CZ method, and the pulling method of the single crystal 46 is almost the same as the pulling method by the CZ method except for the above-mentioned portions.

In the melt layer method, two different methods have been proposed as a method for keeping the impurity concentration in the melt layer 43 constant, that is, a constant melt layer thickness method and a melt layer thickness changing method.

As a method for making the melt layer thickness constant, the solid layer 49 containing no impurities is melted as the single crystal 46 is pulled up, and the volume of the melt layer 43 is kept constant so that the melt layer 43 is kept constant.
There is a method of continuously adding impurities to keep the concentration of impurities in the molten layer 43 constant. JP-B-34-8242, JP-B-62-880 and JP-B-3-7405.
The above-mentioned method is disclosed in Japanese Laid-Open Patent Publication No. 2003-242, and the solid layer 49 is first made to contain impurities, and the impurities are not added to the molten layer 43. A method of keeping the volume constant and the impurity concentration of the molten layer 43 almost constant is disclosed in JP-B-62-880 and JP-A-63-252989.

The melt layer thickness changing method is a method of intentionally changing the volume of the melt layer 43 to keep the impurity concentration in the melt layer 43 constant without adding impurities during the pulling of the single crystal 46. There are Japanese Patent Laid-Open Nos. 61-205691, 61-205692, and 61.
-215285.

In the above two melt layer methods,
The thickness of the molten layer 43 is controlled by the heater 32 as a heating element.
Length and power, position and depth of crucible 31 and heater 32
It is performed by appropriately selecting the shape and material of the heat insulating cylinder 37 which is provided around the outside of the crucible 31 and promotes heat transfer in the lower portion of the crucible 31.

As described above, in the melt layer method, the melt layer 43
Since the impurity concentration in the inside can be kept substantially constant, the yield related to the electrical resistivity can be improved.

Further, as disclosed in Japanese Patent Laid-Open No. 5-24972, the single crystal 46 is pulled up while controlling the elution amount of the solid layer 49 by using a two-stage heater. A single crystal 46 having a substantially constant electrical resistivity in the axial direction of the single crystal 46 can also be obtained by a method of keeping the impurity concentration in the molten layer 43 constant.

[0014]

Another major factor affecting the characteristics of a single crystal is the oxygen concentration in the single crystal.
Most of the Si single crystals used as LSI substrates are CZ
The Si single crystal obtained by the CZ method contains a large amount of oxygen atoms of about 15 × 10 ¹⁷ atoms / cm ³ mixed from the quartz crucible during the pulling. Oxygen atoms present in the interstitial space are usually supersaturated.

Oxygen atoms contained in this supersaturation do not form a solid solution in the Si single crystal and form oxygen precipitates as they are cooled. In the growth process of the oxygen precipitates, in order to alleviate strain, phenomena such as emission of interstitial Si atoms, absorption of vacancies, and generation of dislocation loops called punch-out are caused. Further, Si atoms existing between the lattices are aggregated around the oxygen precipitates during the high temperature heat treatment to form dislocation loops accompanied by stacking faults.

When such crystal defects caused by supersaturated oxygen exist deep in the wafer surface, that is, deeper than the active region of the device,
Impurities that enter the surface area of the wafer during the device manufacturing process by fixing dislocations generated in the wafer and increasing the strength of the wafer, growing oxygen precipitates during the heat treatment process of the wafer and generating strain around them. Has the advantage of trapping and preventing contamination of the active area of the device.

However, if the oxygen precipitates or dislocation loops penetrate into the device active region on the wafer surface, it causes an increase in leak current and causes a problem of degrading device characteristics. In particular, when a wafer is thermally oxidized, a dislocation loop (oxygen-induced stacking fault (OSF)) accompanied by stacking faults that grow due to aggregation of interstitial Si atoms released from an oxide film growing from the wafer surface during thermal oxidation is generated. There is a problem that it occurs on the wafer surface.

The present invention has been made in view of the above problems, and suppresses the generation and growth of oxygen precipitates in a Si single crystal, and even if the Si single crystal is heat-treated after pulling, the OS
It is an object of the present invention to provide a crystal growth method and a single crystal growth apparatus capable of suppressing the generation of F and manufacturing a high-quality Si single crystal.

[0019]

Means for Solving the Problems As a result of studies to achieve the above-mentioned object, the present inventors have found that the generation and growth of oxygen precipitates are found in the intermediate temperature region through which a pulled Si single crystal passes, That is, it is promoted in a temperature region of 1200 to 700 ° C. formed in the pulling axial direction of the single crystal, and the growth of oxygen precipitates can be suppressed by rapidly cooling the Si single crystal in this temperature region, and after pulling, The inventors have found that the generation of OSF is reduced even when a heat treatment or the like of a Si single crystal is performed, and that a high quality Si single crystal can be obtained, and have completed the present invention.

That is, the single crystal growth method according to the present invention is
A method for growing an Si single crystal, which comprises growing a crystal while pulling it from a melt, wherein the grown Si single crystal is 1200
It is characterized by rapid cooling in the temperature range of ℃ to 700 ℃.

Further, the single crystal growth apparatus according to the present invention is a single crystal growth apparatus for pulling up a melt in a crucible to grow a single crystal, wherein a heat shield and a heat shield are provided above the crucible. And a cooling device for cooling.

The method for growing a single crystal according to the present invention is based on the above-mentioned C.
It can be applied to any method such as the Z method and the melt layer method. The single crystal to be pulled has a different thermal history depending on the pulling method, the size of the single crystal growth apparatus, the diameter of the single crystal to be pulled, and so on. It took about 7 hours to cool to ℃. However, in the present invention, since the temperature is cooled from 1200 ° C. to 700 ° C. in about 5 hours, the precipitation of oxygen is suppressed, and the wafer made of the obtained Si single crystal is also subjected to the subsequent heat treatment or the like. Generation of OSF is suppressed.

Usually, the heat shield used in the pulling apparatus by the CZ method or the molten layer method is arranged in the shape of an inverted cone above the crucible. It is in the middle temperature range (1200 to 700 ° C.) of the single crystal, and in the method of the present invention, that part is cooled and the thermal history of the Si single crystal is controlled so as to shorten the time in that temperature range. Therefore, if a cooling device serving as a heat sink is brought into contact with the upper portion of the heat shield, the upper portion and the intermediate portion of the heat shield can be cooled, and the thermal history of the Si single crystal can be controlled.

The cooling device and the heat shield may be movable in the vertical direction, or the cooling device and the heat shield may be combined so that they can move integrally. . Further, the cooling device and the heat shield may have a structure that allows a coolant to flow inside. When a coolant such as water is passed through the cooling device or the heat shield, the cooling capacity of the heat shield can be changed by changing the flow rate. Further, it is preferable that the upper portion of the heat shield and the cooling device are formed of a material having a high heat conductivity such as a refractory metal such as Mo or a ceramic such as AlN or SiC.

As a mechanism for moving the cooling device and the heat shield in the vertical direction, the cooling device and the heat shield inside the chamber can be used in a device that can withstand high temperatures and have such a sealed structure. There is no particular limitation as long as the airtightness of the inside of the chamber can be ensured even if is moved.
As a specific example of the moving mechanism, for example, a nut-threaded member is fixed to a part of the chamber, and a bolt-threaded metal rod and the member are screwed together to form a screw. A mechanism for moving a cooling device or the like fixed to the tip of the cut metal rod by rotating the cut metal rod, and a hydraulic cylinder capable of vertically moving a piston by hydraulic pressure are provided outside the chamber. A mechanism in which the tip of the piston is connected to and fixed to a cooling device inside the chamber, and the piston is moved up and down to move the cooling device can be used.

[0026]

According to the crystal growth method of the present invention, a method for growing a Si single crystal is described, in which a crystal is grown while being pulled from a melt, and the grown Si single crystal is heated from 1200 ° C. to 7 ° C.
Since it is actively cooled in the temperature range of 00 ° C, Si
Generation and growth of oxygen precipitates at the time of pulling the single crystal are suppressed, and a high-quality Si single crystal is manufactured. In the wafer manufactured from the Si single crystal obtained by this method, the generation of OSF is suppressed even in the subsequent heat treatment or the like.

Further, according to the crystal growth apparatus of the present invention, a single crystal growth apparatus for pulling up the melt in the crucible to grow a single crystal, wherein a heat shield is provided above the crucible, and the heat shield is provided. And a cooling device for cooling the
The single crystal of i is easily and surely cooled in the temperature range of 1200 ° C. to 700 ° C., generation and growth of oxygen precipitates at the time of pulling up the Si single crystal are suppressed, and a high quality Si single crystal is manufactured.

[0028]

EXAMPLES AND COMPARATIVE EXAMPLES Examples of a single crystal growth apparatus according to the present invention and examples of pulling a single crystal by the single crystal growth method according to the present invention using the single crystal growth apparatus will be described with reference to the drawings. explain.

In this example, the single crystal was pulled by using the melt layer method. FIG. 1 is a cross-sectional view schematically showing a single crystal growth apparatus according to an example, and 19 in the figure shows a main chamber. In addition, FIG. 2 shows that the cut surface of the single crystal growth apparatus shown in FIG.
It is sectional drawing at the time of rotating by °.

The main chamber 19 is a cylindrical vacuum container, and the crucible 11 is arranged at the central position of the main chamber 19. Further, the crucible 11 is a bottomed cylindrical quartz-made inner layer holding container 11a and this inner layer holding container 11a.
The outer layer holding container 11b is also made of graphite and has a bottomed cylindrical shape and is fitted to the outside of the. In this embodiment,
For example, the inner layer holding container 11a having a diameter of 16 inches and a height of 14 inches is used. Further, a support shaft 16 for rotating and raising and lowering the crucible 11 is provided at the bottom of the outer layer holding container 11b of the crucible 11, and the outer periphery of the crucible 11 has, for example, a main heater 15a having a heat generation length of about 90 mm. However, below the main heater 15a, sub-heaters 15b having the same diameter as the main heater 15a and having a heat generation length of, for example, about 90 mm are arranged in concentric cylinders, and are arranged outside the main heater 15a and the sub-heater 15b. A heat insulation cylinder 22 is provided around the.

On the other hand, above the crucible 11, a pull-up shaft 17 is hung so as to be able to rotate and ascend and descend through a small cylindrical pull chamber 20 which is continuously formed above the main chamber 19 and is formed. A seed crystal 18 is attached to the lower end of 12 via a seed chuck 12 a. Then, after the lower end of the seed crystal 18 is immersed in the molten layer 12, the seed crystal 18 is raised while rotating the seed crystal 18 and the crucible 11, whereby the Si single crystal 14 is grown from the lower end of the seed crystal 18. It is like this.

Next, the heat shield 21 and the cooling device 23, which are the main parts of the single crystal growth apparatus according to the embodiment, will be described below.

Above the crucible 11, Si is pulled up.
A heat shield 21 having an inverted conical shape is arranged so as to surround the single crystal 14, and the heat shield 21 is installed in a member forming the heat retaining cylinder 22. By disposing the heat shield 21 in such a position, the crucible 11 and the molten layer 12 melted in the crucible 11 and the main heater 1
The radiant heat from 5b and the like is insulated, and the Si single crystal 14 is prevented from being excessively heated and consequently gradually cooled.

The cooling device 23 is in contact with the upper portion 21a of the heat shield 21, and the upper portion 21a of the heat shield 21 is cooled by the contact of the cooling device 23 with the heat shield 21 in this manner. As a result, the Si single crystal 14 pulled up is cooled more rapidly.

FIG. 3A is a vertical sectional view schematically showing the structure of the cooling device 23, and FIG. 3B is a sectional view taken along the line CC of the cooling device shown in FIG. 3A. In addition, FIG.
The cutting surface of the cooling device 23 shown in FIG.
It is a fragmentary sectional view showing the case of rotating by 0 °, (b)
Is A of the moving mechanism portion 26 of the cooling device 23 shown in (a).
FIG. 6B is a sectional view taken along the line A-A, and FIG. 6C is a sectional view taken along the line B-B of the moving mechanism portion 26 of the cooling device shown in FIG.

As shown in FIGS. 3 and 4, the cooling device 2
Reference numeral 3 denotes a hollow disc-shaped cooling plate 24, and two refrigerant flow pipes 2 connected to the cooling plate 24 for circulating the refrigerant through the cooling plate 2.
5 and a moving mechanism portion 26 for moving the cooling plate. The cooling plate 24 has a cavity 24a inside so that the refrigerant can be circulated, and the refrigerant is supplied to the cavity 24a through two refrigerant circulation pipes 25 connected to the cooling plate 24. ing. The moving mechanism portion 26 is rotatably connected to the upper portion of the cooling plate 24, and has a threaded rod 26a threaded into a bolt shape, a fixing member 26b to which the threaded rod 26a is screwed, and a threaded rod. The motor 26c has a fixed end 26a. The supporting member 26b is actually divided into two parts as shown in FIG. 2, and is fixed to the main chamber 19. The fixing member 26b has a structure shown in FIG.
As shown in (b), a guide groove 26d is formed so that the motor 26c can move up and down. When the threaded rod 26a rotates clockwise, the cooling plate 24 moves upward, When the threaded rod 26a rotates counterclockwise, the cooling plate 24 moves downward. Although not shown in the figure, in order to maintain airtightness in the main chamber 19 even if the cooling device 23 is arranged in the main chamber 19, the threaded rod 26a or the refrigerant flow pipe 25 and the main chamber 19 are connected to each other. It is sealed by an O-ring or the like. The upper portion 21a of the heat shield 21 is made of Mo, which has good thermal conductivity.

When the single crystal 14 is grown by using the single crystal pulling apparatus having the above-mentioned structure, the crucible 11 is filled with 65 kg of polycrystal of silicon, for example, as a raw material for crystal, and the n-type dopant phosphorus is filled therein. -Add 0.6 g of silicon alloy. And inside the main chamber 19
After setting the Ar atmosphere to 0 Torr, the main heater 15a
Also, the power of the sub-heater 15b is set to about 50 kW, about 100 kW in total, to melt all the crystal raw materials.
Next, the power of the sub-heater 15b is set to 0 kW and the power of the main heater 15a is set to about 70 kW, and the solid layer 13 is formed below the melt. After that, the lower end of the seed crystal 18 is immersed in the molten layer 12, and the crucible 11 and the pulling shaft 17 (the crucible 1
1 rotation / rotation of the pulling shaft 17) = 1 rpm / 10 r
The single crystal 18 is pulled up while rotating so as to have a pm ratio. When the pulling of the single crystal 18 shifts to the neck and the shoulder, and when it shifts to the body, the heater power is adjusted to control the elution amount of the solid layer 13 to keep the impurity concentration of the molten layer 12 constant, and the pulling rate 1 mm / min. The power of the main heater 15a is adjusted so that the diameter of the pulled single crystal 14 is maintained at 154 mm.

When pulling up the Si single crystal 14, water is used as a coolant to circulate in the cooling device 23, and the Si single crystal 14 is pulled up in the medium temperature range (1200 to 700 ° C.).
Was cooled. Further, the temperature of the Si single crystal 14 pulled up at this time was measured using a thermocouple, whereby a predetermined portion of the Si single crystal 14 was measured at 1200 ° C. to 70 ° C.
It was calculated how long it took to cool to 0 ° C.

As a comparative example, a single crystal growth apparatus similar to that of the above-described example was used except that the cooling device 23 was not provided in the single crystal growth apparatus, and Si was used in the same manner as in the case of the example.
The single crystal 14 was pulled up.

FIG. 5 shows a Si wafer manufactured by using the Si single crystal 14 manufactured by using the single crystal growth apparatus according to the example and a Si single crystal manufactured by using the conventional apparatus according to the comparative example. 6 is a graph comparing the number of OSFs generated in a Si wafer by subjecting the Si wafer thus manufactured to a heat treatment in an oxygen atmosphere at 1000 ° C. for 16 hours.

The Si single crystal 14 is heated from 1200 ° C. to 7 ° C.
The time required for cooling to 00 ° C. is 5 in the example.
Time, 7 hours in the comparative example.

As is clear from FIG. 5, S according to the comparative example.
The OSF occurrence rate of the Si wafer made from i single crystal is 10
While it was about 20 (pieces / cm ² ), the OSF occurrence rate of the Si wafer manufactured from the Si single crystal 14 according to the example is remarkably reduced to 0-10 (pieces / cm ² ).

According to the single crystal growth method according to the embodiment, the Si single crystal 14 grown while pulling the crystal from the melt is used.
In the growth method of
Because it cools rapidly in the temperature range of 00 ℃ to 700 ℃,
Generation and growth of oxygen precipitates at the time of pulling Si single crystal can be suppressed, and high-quality Si single crystal 14 can be manufactured. Also, the Si single crystal 14 obtained by the above method
In the Si wafer manufactured by the above method, the generation of OSF can be reduced even in the subsequent heat treatment or the like. Further, according to the crystal growth apparatus of the example, in the single crystal growth apparatus for pulling up the melt in the crucible 11 to grow the single crystal 14, the heat shield 21 is provided above the crucible 11, and the heat shield 21 is provided. Is in contact with the cooling device 23, the grown S
The i single crystal 14 can be rapidly and easily quenched in the temperature range of 1200 ° C. to 700 ° C., and the generation and growth of oxygen precipitates at the time of pulling the Si single crystal can be suppressed. Crystal 14 can be manufactured.

[0044]

As described in detail above, the single crystal growth method according to the present invention is a method for growing a Si single crystal in which a crystal is grown while pulling a crystal from a melt, and the grown S
Since the i single crystal is rapidly cooled in the temperature range of 1200 ° C. to 700 ° C., it is possible to suppress the growth of oxygen precipitates when pulling the Si single crystal, and it is possible to manufacture a high-quality Si single crystal. Further, in the Si wafer manufactured from the Si single crystal obtained by the above method, the generation of OSF can be reduced even in the subsequent heat treatment and the like.

Further, the single crystal growth apparatus according to the present invention is a single crystal growth apparatus for pulling up a melt in a crucible to grow a single crystal, wherein a heat shield and a heat shield are provided above the crucible. Since the cooling device for cooling the shield is provided, the grown Si single crystal can be easily and surely cooled in the temperature range of 1200 ° C. to 700 ° C., and the growth of oxygen precipitates at the time of pulling the Si single crystal can be prevented. It is possible to suppress, and thus it is possible to manufacture a high-quality Si single crystal.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a single crystal growth apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the single crystal growth apparatus shown in FIG. 1 when a cut surface is rotated by 90 ° about a pulling axis.

3A is a vertical cross-sectional view schematically showing the configuration of a cooling device, and FIG. 3B is a CC of the cooling device shown in FIG.
It is a line sectional view.

4 (a) is a sectional view of the cooling device shown in FIG.
Is a partial cross-sectional view showing a case of rotating 90 ° about a central axis, (b) is a cross-sectional view taken along the line AA of the moving mechanism portion of the cooling device shown in (a), and (c) is also the same. It is a BB line sectional view of the movement mechanism part of the cooling device shown in (b).

FIG. 5 is a diagram illustrating the number of OSFs generated in a Si wafer obtained by subjecting a Si wafer manufactured using a single crystal growth apparatus according to an example and a Si single crystal manufactured using a conventional apparatus according to a comparative example to a heat treatment to a Si wafer. It is the graph which compared.

FIG. 6 is a sectional view schematically showing a single crystal growth apparatus used in a conventional CZ method.

FIG. 7 is a sectional view schematically showing a single crystal growth apparatus used in a conventional melt layer method.

[Explanation of symbols]

 11 Crucible 12 Melt Layer 14 Si Single Crystal 21 Heat Shield 23 Cooling Device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideki Fujiwara, 4-53-3 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture Sumitomo Metal Industries, Ltd. (72) Shuichi Inami 4-chome, Kitahama, Chuo-ku, Osaka City, Osaka Prefecture No. 33 Sumitomo Metal Industries, Ltd.

Claims (2)

[Claims] 1. A method for growing a Si single crystal which is grown while pulling a crystal from a melt, wherein the grown Si single crystal is rapidly cooled in a temperature range of 1200 ° C. to 700 ° C. How to grow. 2. A single crystal growth apparatus for pulling up a melt in a crucible to grow a single crystal, comprising a heat shield above the crucible and a cooling device for cooling the heat shield. And a single crystal growth apparatus.