JPH11180793A - Method for controlling single crystal pulling-up rate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method capable of providing high quality wafers in each of which the generation of ring-shaped oxidation-induced stacking faults (R-OSF) can be controlled. SOLUTION: In this method, at the time of forming the shoulder of a single crystal, the single crystal pulling-up rate is adjusted so as not to generate any R-OSF in the crystal surface by using the following operation. The operation comprises: at the time of forming a shoulder that has diameter values equivalent to 50 to 100% of the body diameter, growing the single crystal while maintaining such a pulling-up rate as to be 1.2 to 6 times as high as the average pulling-up rate at the time of forming the body, for <=60 min; and further, in this shoulder formation, the length (L) of the shoulder in the direction of the single crystal pulling-up axis and the body diameter (D) meet the relational expression L/D>=1/4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a pulling speed of a single crystal pulled by a Czochralski method (hereinafter referred to as "CZ method"), and more particularly to a method of forming a single crystal shoulder portion (hereinafter referred to as "shoulder"). Formation)), does not cause oxidation-induced stacking faults in the crystal plane,
When pulling up the target product diameter part (hereinafter referred to as “body part”), the pulling speed of a single crystal that does not generate oxidation-induced stacking faults in the crystal plane or keeps the generation position constant. It relates to a control method.

[0002]

2. Description of the Related Art There are various methods for producing a single crystal. Among them, the CZ method is widely used in a method capable of industrial mass production for pulling a silicon single crystal.

FIG. 1 is a view showing the configuration of a pulling apparatus for growing a silicon single crystal by the CZ method. The pulling of the single crystal is performed in a container of the metal chamber 7, and the crucible 1 is disposed at the center thereof. Further, a heater 2 is provided outside the crucible 1, and a crystal raw material melted by the heater, that is, a melt 3 of polycrystalline silicon is accommodated in the crucible 1. The lower end of the seed crystal 5 attached to the tip of the pulling means 4 made of a wire or the like is brought into contact with the surface of the melt 3 and the seed crystal 5 is pulled upward to solidify the melt 3 at the lower end. A single crystal 6 is grown.

[0004] The shape of a single crystal pulled in growing a single crystal is the most basic quality characteristic, and a seed portion 6a having a reduced diameter immediately below the seed crystal 5, a shoulder portion 6b having a gradually increasing diameter, and a growing portion. It comprises a body portion 6c which is later used as a product wafer, and a tail portion (not shown) for gradually reducing the diameter of the single crystal.

[0005] As a specific procedure for forming the above-mentioned shape, first, seed drawing is performed in order to eliminate dislocations in the crystal. Thereafter, in order to secure a target product diameter of the single crystal, a shoulder is formed into a shoulder portion 6b, and when the body diameter is reached, the process proceeds to growing a single crystal body while forming the body portion 6c with a constant diameter. When a single crystal having a body diameter and a predetermined length is grown, til drawing is performed to separate the single crystal from the melt without dislocation. After that, the single crystal separated from the melt is taken out of the growing apparatus, cooled under predetermined conditions, and processed into a wafer. The wafer processed from the single crystal in this way is subjected to surface polishing and the like, and is used as a substrate material for various devices.

[0006] Depending on the conditions for growing the single crystal, a ring-shaped oxidation-induced stacking fault (hereinafter referred to as R-OSF (Oxidation induced Stch) may be formed on the surface of the single crystal wafer grown through the above-described steps.
acking Fault). This RO
SF is a lattice-type dislocation loop generated on the wafer surface during oxidation heat treatment, and degrades device characteristics.
Usually, a single crystal is grown so that R-OSF is not generated in the crystal plane of the wafer.

On the other hand, several kinds of micro defects (hereinafter referred to as Gr), called dislocation clusters and infrared scatterers, are formed in a plane around the R-OSF.
own-in defect), but G outside the R-OSF
A defect-free region where no rown-in defect exists is formed. In the non-defect region, unlike the R-OSF or the Grown-in defect region, a substrate material exhibiting excellent device characteristics can be provided. Furthermore, subsequent studies have made it possible to enlarge this defect-free region. For this reason, such a defect-free region is actively used as a substrate material of a device. In this case, a single crystal is grown so that R-OSF is generated in a crystal plane of a wafer. .

FIG. 2 shows the pulling speed and R-OSF during single crystal growth.
FIG. 4 is a diagram schematically illustrating a general relationship with the occurrence position of a slash. R-OSF is generated due to a difference in temperature gradient in a pulling axis direction in a crystal plane during single crystal growth. Therefore, as shown in FIG. 2, the region where R-OSF is generated is affected by the pulling speed (mm / min) during growth, and when the pulling speed is increased, the region where the R-OSF appears appears outside the wafer. When moving and lowering the pulling speed, the area where the R-OSF appears moves to the inside of the wafer. For example, in the above-described shoulder formation, since the pulling speed is as slow as about 1/2 of the pulling speed of the body portion, the pulling condition is such that R-OSF is easily generated in the crystal plane.

[0009]

As described above, when growing a single crystal by the CZ method, R-
There are a method of not generating OSF and a method of intentionally generating R-OSF in the crystal plane. In these methods, when a failure occurs according to the position where each R-OSF occurs, it is different from a case where the failure does not occur.
It is necessary to control the occurrence of F constant.

[0010] In the case of adopting a method in which the R-OSF is not generated in the crystal plane of the wafer, if the R-OSF generation region moves inward and the R-OSF is generated in the crystal plane, the R-OSF is generated in the crystal plane. Becomes defective. In particular, during shoulder formation, R-OSF is likely to be generated in the crystal plane of the wafer, but in this case, the pulling is performed at the maximum pulling speed for growing a single crystal at the same time as the pulling of the body part. Raising moves the R-OSF to the region outside the crystal plane. However, as will be described later, it takes a long time for the R-OSF generated on the crystal plane to disappear from the plane, so a wide range of failures occur from the beginning of pulling up the body after shoulder formation. There is a problem that it is easy. The maximum pulling rate here is determined by the amount of heat input and the amount of heat radiation of the single crystal to be grown.If the growth is continued beyond this maximum pulling rate, the single crystal will not be maintained in a circular shape due to supercooling, It becomes square or twists.

On the other hand, intentionally, the R-OS
Even when adopting the method of generating F, it is good if the position where R-OSF occurs can be controlled to a desired position in the crystal plane, but if the position where R-OSF occurs greatly fluctuates, The corresponding crystal part is defective. As described above, when the position where the R-OSF is generated fluctuates, many specifications such as oxygen concentration and specific resistance value are required for the silicon single crystal wafer in addition to the provisions of the R-OSF. Diversion is hardly considered.

In view of the above-mentioned problems of the prior art, the present invention does not generate R-OSF in the crystal plane of a wafer when forming a single crystal shoulder grown by the CZ method.
It is an object of the present invention to provide a method for controlling a pulling speed of a single crystal in which R-OSF is not generated in a crystal plane when a body portion is pulled, or a position where the R-OSF is generated can be controlled to be constant.

[0013]

The present invention provides the following (1) to
The gist is the method of controlling a single crystal pulling speed of (3).

(1) A method for controlling the pulling speed of a single crystal grown by the CZ method, wherein the pulling speed is adjusted so that R-OSF does not occur in the crystal plane during shoulder formation after seed drawing. And a method for controlling a pulling speed of a single crystal. Hereinafter, this method is referred to as a first control method.

In the first control method, when forming a shoulder in which the shoulder diameter is 50% to 100% of the body diameter which is the target product diameter, the pulling speed is 1.2 to 6 times the average pulling speed in the body portion. It is desirable to keep them for 60 minutes or less.

Further, in the implementation of the first control method, when the length of the single crystal in the pulling axial direction until the body diameter becomes equal to the body diameter by shoulder formation after seed drawing is L, and the body part diameter is D, L It is more preferable that / D ≧ 1/4 (see FIG. 4 described later).

(2) A method for controlling a pulling speed of a single crystal grown by the CZ method, wherein the pulling up of a body portion which is a target product after the formation of a shoulder is performed so that R-OSF is not generated in a crystal plane. A method for controlling a pulling speed of a single crystal, characterized by adjusting a speed. Hereinafter, this method is referred to as a second control method.

In the second control method, the average pulling speed of the single crystal is adjusted until the length of the single crystal pulled immediately after the body diameter becomes equal to the body diameter after the shoulder is formed.
It is desirable to grow at a pulling speed of 1.2 to 6 times.

(3) A method for controlling a pulling speed of a single crystal grown by the CZ method, wherein a pulling of a body part as a target product is performed so that R-OSF is generated at a predetermined position in a crystal plane. A single crystal pulling speed control method characterized in that the pulling speed is adjusted within a range from a maximum of 30% to a minimum of 30% of the speed.
Hereinafter, this method is referred to as a third control method.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first control method is characterized in that a pulling speed is adjusted so that R-OSF does not occur in a crystal plane of a wafer in forming a shoulder after seed drawing. As described above, in order to increase the diameter of the single crystal in forming the shoulder, the pulling speed becomes about 1/2 of the pulling speed of the body portion, and the R-OSF is easily generated in the wafer surface. The first control method is adopted. Specifically, when forming a shoulder having a shoulder diameter of 50% to 100% of the body diameter, it is possible to keep the body at a pulling speed of 1.2 to 6 times the average pulling speed of the body and hold the shoulder for 60 minutes or less. desirable. By such operation, R-OSF
Disappears outside the wafer crystal plane. Here, the reason why the lower limit of the shoulder diameter is set to 50% of the body diameter is that even if control is performed with a shoulder diameter smaller than that, the shoulder is too small to be effective in controlling the R-OSF.

FIG. 3 is a diagram showing the relationship between the pulling speed and the time when the R-OSF generated in the crystal plane of the wafer disappears from the plane. The relationship shown in FIG. 3 represents the time until R-OSF is generated in the body portion and disappears outside the crystal plane, and can be applied not only when forming the shoulder but also when pulling up the body portion. The pulling speed is shown in comparison with the average pulling speed of the body portion. The average pulling speed of the body portion here is the pulling length of the body portion (mm) / the pulling time (min). Speed (mm / min).

As is apparent from FIG. 3, the pulling speed of 1.2 to 6 times the average pulling speed of the body portion is set to at least 60 times.
If the amount is held, the R-OSF generated in the crystal plane of the wafer can be moved outside the crystal plane. However, when the above-mentioned pulling speed is maintained for more than 60 minutes, the single crystal is deformed by supercooling, and cannot maintain a circular shape.

Further, in the first control method, when the length of the single crystal in the pulling-up axis direction until the body diameter becomes equal to the body diameter by the shoulder formation after the seed drawing is L, and the body part diameter is D, L / D ≧ More preferably, it is set to 1/4.

FIG. 4 is a diagram for explaining the relationship between the length L of the single crystal in the pulling axial direction until the body diameter becomes equal to the body diameter after the seed drawing in the shoulder formation and the body portion diameter D. After the seed drawing, in the shoulder formation, the pull-up axial direction length L of the single crystal from 5% of the body diameter at which the shoulder portion starts to the body diameter is controlled under the above conditions, so that the R-OSF can be further formed on the wafer. Easily disappears outside of the crystal plane. Further, as shown on the left side of FIG. 4, if the pulling speed is increased in a state where the length L in the pulling axial direction is short, L / D <１ ／, a supercooled state occurs and the single crystal is deformed. It will be easier.

The second control method is characterized in that the pulling speed is adjusted so that R-OSF is not generated in the crystal plane when pulling up the body after the formation of the shoulder. Even if the first control method is adopted, the R-OSF may not be able to be eliminated from within the crystal plane of the wafer, so that adjustment in the body by the second control method is required.

Specifically, the growth is performed at a pulling speed of 1.2 to 6 times the average pulling speed of the single crystal until the length of the single crystal pulled immediately after the body diameter becomes equal to the body diameter after forming the shoulder. It is desirable to do. The reason why the single crystal was grown at a pulling speed of 1.2 times to 6 times the average pulling speed is based on the results shown in FIG. In addition, the pulling length of the single crystal for which the pulling speed is adjusted is limited to the body diameter because, in the initial stage of pulling up the body part, heat is largely released from the shoulder portion and the pulling speed is increased. Because it can be. Further, the numerical limitation by the body diameter is based on the results of various studies by the present inventors.

In the third control method, the maximum pulling speed of the body portion is set so that the R-OSF is generated at a predetermined position in the crystal plane.
It is characterized in that the pulling speed is adjusted within a range of 30% to a minimum of 30%. The target diameter of the body portion of the single crystal changes according to the fluctuation of the silicon melt. It is necessary to control the pulling speed in accordance with the deviation of the diameter, and this third control method makes it possible to generate the R-OSF at a predetermined position in the crystal plane. Therefore, the third control method is as follows.
This is applied when a method of intentionally generating an R-OSF in a crystal plane of a wafer is adopted. Where up to 30
The reason for adjusting the pulling speed within the range of 30% to 30% is that if the pulling speed is adjusted beyond this range, the R-
This is because the OSF greatly fluctuates, and satisfactory quality as an industrial product cannot be obtained.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The speed control method of the present invention is applied to the growth of a single crystal having a diameter of 8 inches (203 mm) by using the pulling apparatus shown in FIG. A single crystal that does not generate and a single crystal that R-OSF generates in the crystal plane of the wafer were manufactured.

(Example 1) As a crystal raw material, 120 kg of polycrystalline silicon was filled, and boron was added as a P-type dopant so that the electric resistivity became 10 Ωcm.
And while rotating the lifting means 4 in opposite directions,
Single crystal 1 was pulled up.

Here, in order to prevent R-OSF from being generated in the crystal plane, the seed aperture is raised at a pulling speed of 2 mm / min to 4 mm.
mm / min, then applying the first control method, shoulder formation was performed at an average pulling speed of 0.8 mm / min, and 1.8 mm / min for 20 minutes from the time when the body diameter reached 60% of the body diameter.
Pulling was performed at ~ 2.2 mm / min. As will be described later, since the average pulling speed of the body portion is 1.1 mm / min, the pulling speed in this shoulder formation is equivalent to 1.6 to 2.0 times. Since the length L of the shoulder portion in the direction of the pulling axis is 80 mm, L / D is 0.39.

Next, by applying the second control method, the length of the single crystal to be pulled after the transition to the pulling of the body portion is 50
1.8mm / min until it reaches mm (about 1/4 of body diameter)
Crystals were grown at ３3 mm / min (corresponding to 1.6 to 2.0 times the average pulling speed of the body). As a result, the average pulling speed of the body portion was 1.1 mm / min, but this average speed was the maximum speed at which the single crystal was not deformed by supercooling.

Since the body diameter of the single crystal fluctuates with the fluctuation of the silicon melt, the third control method was applied.
The pulling speed was adjusted within a range of ± 0.2 mm / min with a pulling speed of 1.2 mm / min in order to suppress the influence of the fluctuation of the silicon melt.

After pulling up the single crystal, the wafer was cut out by slicing, subjected to a surface mirror polish, oxidized, and then light-etched to observe the crystal plane of the wafer. As a result, no R-OSF was observed in the crystal plane over the entire length of the grown single crystal.

Example 2 A single crystal was pulled up in the same manner as in Example 1 for filling polycrystalline silicon and adding a P-type dopant. Further, pulling was performed under the same conditions as in Example 1 until a shoulder was formed from the seed drawing and the process shifted to pulling of the body portion.

Here, the third control method is applied to make the R-OSF occur in the crystal plane of the wafer,
The pulling speed of the body part is set to 0.7 mm / min, and the pulling speed is adjusted within a range of ± 0.15 mm / min, and the R-OSF is set to a predetermined position in the crystal plane of the wafer, for example, the radius of the wafer as R. R-
The position where the inner diameter of the OSF occurs was set to 1 / 3R.

After pulling up the single crystal, the wafer was cut out by slicing, polished on the surface, oxidized, and then light-etched to observe the crystal plane of the wafer. As a result, 50mm from the transition position to the body
Up until the transition position, the R-OSF was at a predetermined position, and the R-OSF did not exist in the crystal plane.
/ 3R.

From the above Examples 1 and 2, by applying the pulling speed method of the present invention in pulling a single crystal,
It can be seen that defects in the product single crystal can be significantly reduced. That is, when growing a single crystal in which R-OSF is not generated in the crystal plane of the wafer, R-OSF is not generated in the crystal plane. Further, even when the R-OSF is generated in the crystal plane, the R-OSF can be generated at a predetermined position in the crystal plane of the wafer immediately after shifting to the pulling of the body.

[0038]

According to the pulling speed control method of the present invention, C
In pulling up the Z method, R-OSF is not generated in the crystal plane, or the generation position can be kept constant.
High quality single crystal wafers can be grown.
Moreover, by applying the pulling speed control method of the present invention, the yield of single crystal is increased, and a more inexpensive wafer can be provided.

[Brief description of the drawings]

FIG. 1 is a view showing a configuration of a pulling apparatus for growing a silicon single crystal by the CZ method.

FIG. 2 is a diagram schematically illustrating a general relationship between a pulling speed during the growth of a single crystal and an R-OSF generation position.

Fig. 3 Pulling speed and R-OS generated in the crystal plane of the wafer
It is a figure showing relation with time when F disappears from a field.

FIG. 4 is a view for explaining the relationship between the length L of the single crystal in the pulling axial direction until the body diameter becomes equal to the body diameter after seed drawing in the shoulder formation and the body part diameter D.

[Explanation of symbols]

 1: Crucible 2: Heater 3: Melt 4: Pulling means 5: Seed crystal 6: Single crystal 6a: Seed part 6b: Shoulder part 6c: Body part 7: Metal chamber

Claims (6)

[Claims] A method for controlling a pulling speed of a single crystal grown by a Czochralski method, wherein a ring-shaped oxidation-induced stacking fault is not generated in a crystal plane in forming a shoulder after seed drawing. A method for controlling a pulling speed of a single crystal, comprising adjusting a speed. 2. When forming a shoulder in which the shoulder diameter is 50% to 100% of the body diameter which is the target product diameter, the body is held at a pulling speed of 1.2 to 6 times the average pulling speed of the body for 60 minutes or less. The method for controlling a pulling speed of a single crystal according to claim 1, wherein the crystal is grown by growing. 3. When the length of the single crystal in the pulling axial direction until the body diameter is formed by shoulder formation after seed drawing is L, and the body diameter is D, L / D ≧ １ ／. 3. The method for controlling a pulling speed of a single crystal according to claim 2, wherein: 4. A method for controlling a pulling speed of a single crystal grown by a Czochralski method, wherein ring-shaped oxidation-induced stacking faults are generated in a crystal plane when a body portion serving as a target product is formed after a shoulder is formed. A pulling speed control method for a single crystal, wherein a pulling speed is adjusted so as not to cause the pulling. 5. A method of growing a single crystal at a pulling speed of 1.2 to 6 times the average pulling speed of the single crystal until the length of the single crystal pulled immediately after the body diameter becomes equal to the body diameter after forming the shoulder. 5. The method for controlling a pulling speed of a single crystal according to claim 4, wherein: 6. A method for controlling a pulling speed of a single crystal grown by a Czochralski method, wherein a target product is formed such that ring-shaped oxidation-induced stacking faults are generated at predetermined positions in a crystal plane. Maximum 30% to minimum 30 of body speed
%, Wherein the pulling speed is adjusted within the range of%.