JPH05270973A - Determination of magnetic field to be applied in pulling of single crystal - Google Patents

Abstract

PURPOSE:To control the oxygen concentration and get uniform resistivity on a cross section of a single crystal rod doped with a dopant and obtained by MCZ process by measuring the resistivity on a cross section at plural different magnetic field intensities. CONSTITUTION:A silicon single crystal rod is pulled up from a molten silicon obtained by putting silicon crystals into a quartz crucible and applying a magnetic field of 1,000 gauss. The resistivity values on the cross section of the crystal rod are plotted on a graph. The plotting is carried out plural times by changing the intensity of the magnetic field of the MCZ process to 2,000 gauss, 3,500 gauss and 0 gauss. The magnetic field intensity to get completely uniform resistivity on the cross-section of the silicon single crystal rod is determined based on the relationship between the applied magnetic field intensity and the resistivity distribution on the cross section.

Description

Detailed Description of the Invention

[0001]

The present invention relates to the MCZ method (Magnetic f
The present invention relates to a method for determining an applied magnetic field for pulling a single crystal by the ield applied Czochralski crystal growth method.

[0002]

2. Description of the Related Art Conventionally, a silicon wafer is manufactured by pulling a silicon single crystal ingot by the CZ method and subjecting this silicon single crystal ingot to slicing. The CZ method is
Immersing a silicon single crystal seed crystal in a silicon melt in a quartz crucible, while rotating the seed crystal and the quartz crucible in reverse, the seed crystal is gradually pulled up, and a large-diameter silicon with the same crystal orientation as the seed crystal. This is for growing a single crystal rod. Then, in order to obtain a silicon wafer having a good in-plane resistivity distribution, a method of increasing the value of (crystal rotation speed) / (crucible rotation speed) is used when pulling the silicon single crystal rod.

Further, the MCZ method in which a magnetic field is applied to a pulling apparatus of the CZ method suppresses a thermal convection phenomenon of a silicon melt in a quartz crucible and mixes impurities (oxygen etc.) from the quartz crucible into the silicon melt. Is significantly reduced, the solid-liquid interface between the silicon single crystal rod and the silicon melt is kept in a more static state, and the oxygen concentration in the silicon single crystal rod is reduced. , Or
It is possible to control the oxygen concentration by changing the crucible rotation speed. As described above, in the MCZ method, it is known that the oxygen concentration can be controlled by adjusting the crystal rotation speed and the crucible rotation speed when pulling a silicon single crystal rod without adding a dopant.

[0004]

However, in the conventional CZ method, in order to make the in-plane resistivity distribution of the silicon wafer completely uniform, the crystal rotation speed is set to be 10 times or more the rotation speed of the crucible. Although it is expected that it will be necessary, in reality, under such conditions, the level control of the oxygen concentration cannot be performed, so that the CZ method has not yet achieved complete homogenization of the in-plane resistivity. .. On the other hand, in the silicon wafer using the MCZ method, although the oxygen concentration can be precisely controlled, it has not been confirmed whether the resistivity distribution within the surface of the silicon wafer can be made completely uniform.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present application have variously changed the magnetic field strength applied to the silicon melt in the quartz crucible while rotating the crucible rotation speed and the crystal rotation speed at a feasible speed. , The oxygen concentration is controlled, and
It was found that there is a magnetic field strength that can make the resistivity distribution in the plane of the silicon wafer completely uniform.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for determining an applied magnetic field for pulling a single crystal which can control the oxygen concentration and can make the resistivity distribution in the plane of a silicon wafer completely uniform. is there.

[0007]

In the method for determining an applied magnetic field for pulling a single crystal according to the present invention, the in-plane resistivity of a transverse section of a single crystal rod doped with a dopant obtained by the MCZ method is determined by a plurality of different magnetic fields. The strength is measured, and the magnetic field strength having a small distribution of the in-plane resistivity is determined based on the correlation.

[0008]

In the method for determining the applied magnetic field for pulling a single crystal according to the present invention, the single crystal rod is pulled by the MCZ method. With respect to the applied magnetic field strength at this time, the in-plane resistivity distribution of the cross section of the single crystal rod is plotted, for example, on a graph. This plot is performed multiple times by changing the applied magnetic field of the MCZ method. As a result, it is possible to determine the magnetic field strength at which the in-plane resistivity under the pulling condition is completely uniform.

[0009]

EXAMPLE An example of the present invention will be described below. The single crystal pulling apparatus used in this embodiment is the same as the MCZ method single crystal pulling apparatus having a conventionally known structure. This single crystal pulling apparatus has a magnetic field device in which an N pole and an S pole are opposed to each other at a predetermined distance, and a chamber provided between both poles of the magnetic field device. This magnetic field device generates a magnetic field in the horizontal direction from the N pole toward the S pole. A crucible shaft rotated by a motor is provided at the center of the chamber. A cylindrical graphite susceptor with a bottom is attached to the upper end of the crucible shaft. A quartz crucible is detachably held in the graphite susceptor. This quartz crucible also
It has a substantially hemispherical shape. A silicon melt is held in the quartz crucible.

A heater for heating the silicon melt and a heat shield member are arranged outside the graphite susceptor so as to surround the graphite susceptor. Further, a pulling mechanism is provided on the upper part of the chamber. With this pulling mechanism, the pulling wire is configured to move up and down above the quartz crucible while rotating in a direction opposite to the quartz crucible.
A seed crystal of a silicon single crystal is attached to the tip of the pulling wire via a seed chuck. When this seed crystal is immersed in a silicon melt and then raised, the seed crystal grows sequentially starting from the seed crystal, and a silicon single crystal rod having the same crystal orientation as this seed crystal is pulled in an argon atmosphere.

Next, a method for determining an applied magnetic field for pulling a single crystal using the above single crystal pulling apparatus will be described. Prior to the pulling, a high-purity polycrystalline silicon and a small piece of a silicon crystal highly doped with phosphorus are put in a quartz crucible in a graphite susceptor. All of these are attached to the crucible shaft. After the inside of the chamber is evacuated by a vacuum device, argon gas is supplied into the chamber so that the inside of the chamber is 10 to 20.
Argon atmosphere of Torr. Using a magnetic field device,
While applying a magnetic field of 1000 gauss in the horizontal direction, the heater is directly energized to heat the quartz crucible and melt the raw material such as silicon.

Then, the crystal orientation <1 is set on the seed chuck.
00> silicon single crystal seed crystal is attached, and this seed crystal is brought into contact with the central portion of the liquid surface of the silicon melt. Simultaneously with this contact, the motor rotates the crucible shaft to the left at a rotation speed of 5 rotations / minute, and the pulling mechanism rotates to the right at a rotation speed of the crystal of 10 rotations / minute to move the seed crystals. Raise slowly. As a result, a silicon single crystal ingot grows and is pulled up from the seed crystal. Then, the diameter of the silicon single crystal ingot was monitored by an optical sensor for diameter control diagonally above the quartz crucible, and the pulling rate of the pulling mechanism was changed (average 1.4 to 1.7 mm / min) to obtain the diameter. Is always 6 inches.
When the length of the straight body portion of the silicon single crystal ingot reaches 600 mm, the silicon single crystal ingot is subjected to tail treatment, and the N-type silicon single crystal ingot having the crystal orientation <100> is taken out from the single crystal pulling apparatus.

Next, the taken out silicon single crystal ingot is longitudinally split, and the in-plane uniformity as a silicon wafer is evaluated by the four-point probe method for the resistivity at the central portion and the peripheral portion in the crystal radial direction. .. This evaluation is {(peripheral resistivity-central resistivity) / central resistivity} × 100 (%)
Was performed by substituting into the equation (1), and the measured values at 10 points in the longitudinal direction were averaged to obtain a representative value of the silicon single crystal ingot.
The typical value and the applied magnetic field of 1000 thus obtained
Gauss is plotted in Fig. 1 by ●. The graph in Figure 1
The vertical axis represents the in-plane uniformity of resistivity, and the horizontal axis represents the applied magnetic field strength.

Next, while keeping the other pulling conditions constant,
The applied magnetic field of the MCZ method was changed to 2000 Gauss, 3500 Gauss, and 0 Gauss, and the silicon single crystal rods were pulled up, and the in-plane resistivity was measured, respectively.
Plot each symbol with a ● mark. As a result, 1
It can be determined that there is a magnetic field strength in the vicinity of the magnetic field strength of 700 gauss that can make the in-plane resistivity of the N-type silicon wafer completely uniform. The applicant of the present invention has confirmed that the oxygen concentration in the silicon single crystal ingot is controlled within a predetermined range in each case.

Next, with the other pulling conditions kept constant, 1
A magnetic field of 900 gauss is applied to pull up the silicon single crystal ingot by the MCZ method. When a silicon wafer is manufactured from this silicon single crystal ingot and the in-plane resistivity of this silicon wafer is measured, both the central portion and the peripheral portion of the in-plane surface of the silicon wafer have the same resistivity. Therefore, a silicon wafer having a completely uniform in-plane resistivity distribution can be manufactured.

Next, the boron-doped P-type silicon single crystal ingot is pulled up by the MCZ method. The magnetic field applied at this time is changed to 0 gauss, 1000 gauss, 2000 gauss, and 3500 gauss. A silicon wafer is manufactured from each of the pulled silicon single crystal rods, and the resistivity distribution is measured and plotted with a black square in FIG. As a result, it is possible to determine the magnetic field strength that can make the in-plane resistivity of the P-type silicon wafer completely uniform. The in-plane resistivity of the silicon wafer manufactured from the silicon single crystal ingot pulled by the MCZ method by applying this 2000 gauss magnetic field is the same in the central portion and the peripheral portion, and is completely uniform. Similarly, the same experiment is performed for the case of doping with antimony, arsenic, etc. In general, in order to control the in-plane resistivity distribution of a silicon wafer within ± 5%, the applied magnetic field strength is 1500 to 2500 gauss. Has been confirmed to be suitable.

[0017]

As described above, according to the method for determining an applied magnetic field for pulling a single crystal according to the present invention, pulling conditions for a single crystal rod capable of producing a wafer having a completely uniform in-plane resistivity can be determined.

[Brief description of drawings]

FIG. 1 is a graph used in a method of determining an applied magnetic field for pulling a single crystal according to an embodiment of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayuki Shinnai 1-297, Kitabukuro-cho, Omiya-shi, Saitama Mitsubishi Materials Corporation Central Research Laboratory

Claims (1)

[Claims] 1. The in-plane resistivity of a cross section of a single crystal ingot obtained by the MCZ method and doped with a dopant is measured for each of a plurality of different magnetic field intensities, and the in-plane resistivity is determined based on the correlation. A method for determining an applied magnetic field for pulling a single crystal, which comprises determining a magnetic field strength having a small distribution of resistivity.