JPH0761894A - Method for growth control of single crystal drawing part - Google Patents

Abstract

PURPOSE:To provide the subject method enabling the diameter controllability of single crystal drawing part to be raised. CONSTITUTION:A seed crystal 9 attached to the lower end of a wire 7 is immersed in a stock melt 12 in a quartz crucible 2 being revolved at a specified speed of CR, and this wire 7 is pulled at a specified speed of SE while revolving it to grow a single crystal 13 at the tip of the seed crystal 9. In this single crystal drawing process using CZ process, the diameter of the single crystal drawing part is controlled with at least the single crystal pull speed SE and the crucible revolving speed CR as parameters. Since the crucible revolving speed CR of high control responsiveness is used as the parameter in place of conventional heater temperature, the diameter controllability of the single crystal drawing part can be raised and the successfulness of single crystal growth can be improved.

Description

Detailed Description of the Invention

[0001]

The present invention relates to the CZ method (Czochralski method).
) Relates to a method for controlling growth of a single crystal narrowed portion in growing a single crystal.

[0002]

2. Description of the Related Art In a single crystal growth apparatus employing the CZ method, a raw material such as polycrystalline silicon supplied to a quartz crucible is heated and melted by a heater, and a molten melt (hereinafter referred to as "melt"). A seed crystal attached to the lower end of a pulling shaft such as a wire is dipped in and is pulled at a predetermined speed while rotating the pulling shaft to grow a single crystal at the tip of the seed crystal.

By the way, in the CZ method, the diameter of the seed crystal is narrowed to about 2 to 5 mm to form a narrowed portion in order to make the crystal dislocation-free after immersing the seed crystal in the melt and starting the growth of the single crystal. The drawing process is essential. After the drawing step, a cone step of gradually expanding the grown single crystal to a specified diameter, a straight body step of growing the single crystal with the specified diameter, and a slip of the single crystal due to thermal stress when separating the single crystal. A tailing process is performed in which the diameter of the single crystal is gradually reduced to prevent entry.

Therefore, in the drawing step, the diameter of the single crystal drawn portion needs to be controlled with an accuracy of deviation of about 0.5 mm or less. If the diameter is too narrow, the grown single crystal is cut from the melt and the single crystal is cut. It becomes impossible to grow crystals, or it becomes impossible to support the straight body part that is to be grown thereafter due to insufficient strength of the drawing part. Conversely, if the diameter is too large, dislocation-free crystals are sufficiently formed in the drawing part. If this is not done, the crystals will have dislocations in the cone portion or in the straight body portion that follows, and the quality of the single crystal will deteriorate.

Therefore, the diameter of the single crystal narrowed portion must be controlled with high precision, and conventionally, the diameter of the single crystal narrowed portion was controlled by the crystal pulling speed and the heater temperature. Specifically, depending on the type of the single crystal, for example, when the single crystal is pulled at a speed of the upper limit value of 2 to 3 mm / min or more, protrusions are generated in the single crystal and cause crystal defects,
The crystal pulling rate is controlled in the range of 2 to 3 mm / min or less, but if it cannot be controlled in this range, it was also controlled by the heater temperature.

[0006]

However, in controlling the heater temperature, it takes 10 to 30 minutes for the surface temperature of the melt to stabilize, so the control response is poor and the controllability of the diameter of the single crystal drawn portion is also poor. There was a problem of getting worse.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for controlling the growth of a single crystal drawn portion which can improve the diameter controllability of the single crystal drawn portion.

[0008]

In order to achieve the above object, the present invention is to dip a seed crystal attached to a lower end of a pulling shaft into a raw material melt in a crucible rotating at a predetermined speed CR, and to pull the pulling shaft. While rotating the
In the single crystal drawing step in the CZ method of growing a single crystal by pulling the single crystal, the diameter of the single crystal drawn portion is controlled by using at least the single crystal pulling speed SE and the crucible rotation speed CR as parameters.

[0009]

According to the present invention, since the crucible rotation speed CR having high control response is used as the diameter control parameter of the single crystal narrowed portion, instead of the conventional heater temperature, the diameter controllability of the single crystal narrowed portion is improved. As a result, the success rate of single crystal growth can be improved.

By the way, when the crucible rotation speed CR is increased, the melt center temperature is lowered, so that the diameter of the single crystal narrowed portion is increased. Conversely, when the crucible rotation speed CR is decreased, the melt center temperature is increased and the single crystal is increased. The diameter of the narrowed portion becomes smaller.

[0011]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic sectional view of an apparatus for growing a single crystal for carrying out the method of the present invention. In the figure, 1 is a stainless steel chamber in which a quartz crucible 2 has a shaft. It is attached and stored on top of the 3rd floor. The shaft 3 and the quartz crucible 2 are rotationally driven around its central axis at a speed CR by a driving unit (not shown).

A heater 4 made of carbon is arranged around the quartz crucible 2 in the chamber 1, and the heater 4 and the quartz crucible 2 are surrounded by a cylindrical heat insulating member 5 made of carbon. Has been done.

On the other hand, in the chamber 1, a wire 7 as a pulling shaft which is elevated and lowered by a motor 6 is hung, and a seed crystal 9 is held at a lower end of the wire 7 via a holder 8. .

A window 1 provided on the shoulder of the chamber 1
In the vicinity of 0, a CCD camera 11 for optically measuring the diameter of the growing single crystal is installed.

Next, the operation of the present single crystal growing apparatus will be described.

For example, when growing a silicon single crystal by the CZ method, the inside of the chamber 1 is kept under a reduced pressure (eg, an internal pressure of 30 mbar) in an Ar gas atmosphere, and the polycrystalline silicon supplied into the quartz crucible 2 is heated by a heater 4. The quartz crucible 2 is heated and melted by the, so that a melt 12 of polycrystalline silicon is contained in the quartz crucible 2.

Next, the motor 6 is driven to drive the wire 7
When the temperature is lowered, the seed crystal 9 held at the lower end of the wire 7 is immersed in the melt 12 in the quartz crucible 2, and the quartz crucible 2 is rotationally driven together with the shaft 3 in the direction of the arrow (clockwise direction) at a speed CR. At the same time, when the seed crystal 9 is also pulled at a predetermined speed SE while being rotated at a speed SR in the direction of the arrow (counterclockwise direction) in the drawing, a single crystal 13 grows on the tip of the seed crystal 9 as shown in the drawing.

By the way, in the CZ method, the seed crystal 9 is dipped in the melt 12 and the growth of the single crystal 13 is started.
A drawing process of forming a narrowed portion by narrowing down to a certain degree is indispensable, and as described above, the diameter of the narrowed portion needs to be controlled with high accuracy.

Now, a method of controlling the diameter of the single crystal narrowed portion according to the present invention will be described with reference to FIGS. 2 to 4. Incidentally, FIG.
Is a flow chart showing the diameter control procedure of the single crystal drawing portion,
3 and 4 show the crystal pulling speed SE and the crucible rotation speed C.
It is a figure which shows the time-dependent change of R.

In this embodiment, the crystal pulling speed SE, the crucible rotation speed CR and the time are used as the diameter control parameters, and the temperature of the heater 4 is kept constant.

When the drawing process is started (STEP in FIG. 2)
1), crucible rotation speed CR is initial value (CR) _O = 14r
The crystal pulling speed SE is set in the range of 0.25 to 2 mm / min according to the diameter of the single crystal diaphragm portion measured by the CCD camera 11 (see FIG. 2).
STEP 2). That is, if the diameter of the single crystal drawn portion is larger than the set value, the pulling speed SE is increased, and conversely, if the diameter of the single crystal drawn portion is smaller than the set value, the pulling speed S is set.
E can be lowered.

Thus, in this embodiment, the crystal pulling speed S
0.4 mm / mi as the lower limit set value (SE) _MIN of E
n, upper limit set value (SE) _MAX as 1.9 mm / min
Is set, and the pulling speed SE is (SE) _MIN ~
(SE) The crucible rotation speed C every time the state deviating from the range of _MAX (0.4 to 1.9 mm / min) continues for a predetermined time.
Control for increasing / decreasing R by 1 rpm is performed.

That is, while the length of the single crystal narrowing portion does not reach the set length (10 times or more the diameter of the narrowing portion) (ST of FIG. 2).
In EP3), the diameter of the narrowed portion becomes small because the temperature of the melt 12 is high, and as a result, the single crystal pulling speed SE is below the lower limit set value (SE) _MIN (= 0.4 mm / min) (SE ≦ If (SE) _MIN ) continues for 40 seconds, as shown in FIG.
Is increased by 1 rpm (STEP P4, 5 in FIG. 2), for example C
R = 15 rpm and the state is further 120 sec
If it continues for c times, the crucible rotation speed CR is further increased by 1 rpm at that point (STEPs 6 and 7 in FIG. 2), for example, CR =
It is set to 16 rpm. Thus, the crucible rotation speed C
When R is increased, the central temperature of the melt 12 is decreased and the diameter of the narrowed portion is controlled to be increased.

On the contrary, since the temperature of the melt 12 is low, the diameter of the narrowed portion is large, which causes the single crystal pulling speed SE to be the upper limit set value (SE) _MAX (= 1.9 mm / mi).
n) or more (SE ≧ (SE) _MAX ) is 210s
If it continues for ec, as shown in FIG. 4, the crucible rotation speed CR is reduced by 1 rpm at that time (STEP8 of FIG. 2,
9), for example, CR = 13 rpm (when the judgment results in STEP4 and STEP6 in FIG. 2 are both NO), and if that state continues for a further 420 seconds, the crucible rotation speed CR will further increase by 1 rpm. Lowered (STEP 1 in Figure 2
0, 11), for example CR = 12 rpm (STEP 4,
6) is set to NO). When the crucible rotation speed CR is lowered in this way, the central temperature of the melt 12 rises and the diameter of the throttle portion is controlled to the smaller side. In addition, STEP4, 6 and STEP8 of FIG.
By combining the 10 judgment results (YES or NO),
Crucible rotation speed CR is initial value (CR) _O ± 2 rpm
It is increased or decreased within the range of (12 to 16 rpm).

As described above, in this embodiment, since the crucible rotation speed CR having high control response is used as the diameter control parameter of the single crystal narrowed portion, instead of the conventional heater temperature, the single crystal narrowed portion is controlled. The diameter controllability is improved and the success rate of single crystal growth is improved.

[0027]

As is apparent from the above description, according to the present invention, the raw material melt in the crucible rotating at the predetermined speed CR is
Immerse the seed crystal attached to the lower end of the pulling shaft,
In the single crystal drawing step in the CZ method for growing a single crystal by pulling it at a predetermined speed SE while rotating the pulling shaft, at least the single crystal pulling speed SE and the crucible rotation speed CR are used as parameters. Since the diameter of the narrowed portion is controlled, there is an effect that the diameter controllability of the single crystal narrowed portion can be enhanced.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a single crystal growth apparatus for carrying out the method of the present invention.

FIG. 2 is a flowchart showing a diameter control procedure of a single crystal drawing portion.

FIG. 3 is a diagram showing changes over time in a crystal pulling speed SE and a crucible rotation speed CR.

FIG. 4 is a diagram showing changes over time in a crystal pulling speed SE and a crucible rotation speed CR.

[Explanation of symbols]

2 Quartz crucible (crucible) 7 Wire (pulling shaft) 9 Seed crystal 12 Melt (melt of raw material) 13 Single crystal CR crucible rotation speed SE Single crystal pulling speed (SE) _MAX Set upper limit of crystal pulling speed (SE) _MIN crystal Lower limit setting value of pulling speed

Front page continued (72) Inventor Michiaki Yoshida 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Semiconductor Co., Ltd. Isobe Factory (72) Inventor Kimio Mogi 2-13-1, Isobe, Gunma Prefecture Shin-Etsu Semiconductor Co., Ltd.

Claims (2)

[Claims] 1. A seed crystal attached to a lower end of a pulling shaft is immersed in a raw material melt in a crucible rotating at a predetermined speed CR, and the seed crystal is pulled up at a predetermined speed SE while rotating the pulling shaft. In the single crystal drawing step in the CZ method of growing a single crystal by means of the above method, the diameter of the single crystal drawing part is controlled by using at least the single crystal pulling speed SE and the crucible rotation speed CR as parameters. Control method 2. The crucible rotation speed CR is increased every time the single crystal pulling speed SE is equal to or lower than a predetermined lower limit set value (SE) _MIN for a predetermined time, and the single crystal pulling speed S is increased.
The method for controlling growth of a single crystal drawn portion according to claim 1, wherein the crucible rotation speed CR is lowered every time a state where E is equal to or _larger than a predetermined upper limit set value (SE) _MAX continues for a predetermined time.