JP3467942B2 - Single crystal pulling method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously feeding a fixed raw material into a semiconductor melt stored in a crucible while producing a semiconductor single crystal from the semiconductor melt. single crystal pulling how to raise
About the law . 2. Description of the Related Art Conventionally, the CZ method has been known as one of the methods for growing a semiconductor single crystal such as silicon (Si) or gallium arsenide (GaAs). This CZ method has a large diameter,
This method is used for growing various semiconductor crystals because it has features such as that a high-purity single crystal can be easily obtained without dislocations or with very few lattice defects. In the batch type CZ method, since the amount of the semiconductor melt in the crucible decreases as the single crystal grows, the quality of the single crystal (oxygen concentration, crystal growth interface, impurity concentration, etc.) is reduced in the direction of the growth axis. However, there was a problem that the quality was changed, and only a part of the obtained single crystal became a desired quality, resulting in low productivity. As a solution to this problem, a continuous charge type CZ method (CCZ method) for continuously growing a single crystal while continuously supplying a raw material to a crucible has been known. According to this CCZ method, the growth amount (pulling amount) of a single crystal
Therefore, the amount of semiconductor melt can be kept constant throughout the growth process, and the quality can be made uniform. In the CCZ method, control of the diameter of a growing single crystal is an important issue, and various studies have been made to reduce the fluctuation of the diameter of the single crystal. As means for controlling the diameter of the single crystal, for example, JP-A-4-243
No. 996 discloses the following techniques A to C. In the technique A, the growth rate in the radial direction is increased or decreased by changing the output of a heater for heating the semiconductor melt in the crucible to adjust the melt temperature, thereby controlling the diameter of the single crystal. The technique B controls the diameter of the single crystal by changing the pulling speed at which the single crystal is pulled.
The technique C controls the diameter of the single crystal by adjusting the temperature of the semiconductor melt by increasing or decreasing the amount of the solid raw material charged into the crucible. Further, the diameter of a single crystal to be grown is controlled by applying these techniques A to C in combination. [0007] However, the following problems remain in the means for controlling the diameter of a single crystal in the above-mentioned method for pulling a single crystal. That is, in the technique A, when the output of the heater is changed, the response time until the semiconductor melt changes to a desired temperature and stabilizes is slow, and it is actually difficult to accurately and finely control the diameter. [0008] The technique B is excellent in response to the technique A, but when the pulling speed is changed, the speed at which the single crystal actually grows in the axial direction, ie, the effective growth speed greatly fluctuates. In some cases, the electrical characteristics, defect density, and the like of the resulting single crystal fluctuate, thereby adversely affecting the quality. In the technique C, the responsiveness is excellent as in the technique B. However, since the amount of crystal growth does not coincide with the fluctuation amount of the semiconductor melt, when the pulling speed is constant, the liquid of the semiconductor melt is The position changes with an increase or decrease of the input amount of the solid raw material, and also in this case, the effective growth rate also changes. When the pulling rate is adjusted in response to a change in the liquid level of the semiconductor melt due to an increase or a decrease in the amount of the input of the solid raw material, a change in the effective growth rate can be suppressed.
Since the relative liquid level of the semiconductor melt with respect to the position of the heater fluctuates, the temperature near the liquid surface of the semiconductor melt and its temperature distribution deviate from the setting, and the diameter control becomes difficult. The present invention has been made in view of the above-mentioned problems, and while controlling the diameter of a single crystal to be grown while keeping the effective growth rate constant, suppresses the fluctuation and achieves uniform quality. It is an object of the present invention to provide a method for stably pulling a large-diameter long single crystal. The present invention has the following features to attain the object mentioned above. That is, in the single crystal pulling method of the present invention, a semiconductor melt melted by heating of a heater is stored in a crucible provided inside an airtight container, and while the solid raw material is charged into the crucible, the inside of the crucible is charged. In the single crystal pulling method for pulling a long semiconductor single crystal from the semiconductor melt, when the diameter of the semiconductor single crystal is larger than a set diameter, the amount of the solid raw material is reduced, and When the crystal becomes smaller than the set diameter, increase the input amount of the solid raw material,
Increase or decrease of the input amount of the solid material and the growth amount of the semiconductor single crystal
This is applied to the change in the liquid level of the semiconductor melt calculated from
Set the amount of lifting and lowering of the double crucible to be corrected in advance, and
The crucible is moved up and down by the crucible elevating mechanism in conjunction with the increase and decrease of the charge amount, and the liquid level of the semiconductor melt relative to the position of the heater is kept constant. In this single crystal pulling method, when the diameter of the single crystal becomes larger than the set value, the amount of the solid material to be charged is reduced to reduce the cooling effect of the semiconductor material by the charged solid material and to reduce the melting temperature. The liquid temperature is increased, and the growth rate of the single crystal in the radial direction is decreased. Conversely, when the diameter of the single crystal becomes smaller than the set value, by increasing the input amount of the solid source, the cooling effect of the semiconductor melt by the input solid source is increased, the melt temperature is lowered, and the single crystal is cooled. Increase the radial growth rate. Note that the temperature of the semiconductor melt changes with a quick response to an increase or decrease in the amount of injection since the solid raw material is directly injected into the semiconductor melt. The storage amount of the semiconductor melt fluctuates due to the increase or decrease in the input amount of the solid raw material, and the absolute value of the liquid level changes, but in response to the increase or decrease in the input amount, the crucible is raised and lowered, and the position of the heater with respect to the position of the heater is changed. By keeping the relative liquid level of the semiconductor melt constant, the liquid surface temperature of the semiconductor melt and its temperature distribution are maintained in the set state. An embodiment of the present invention will be described below with reference to FIG. In these figures, reference numeral 1 denotes a silicon single crystal pulling apparatus, 2 denotes a chamber, 3 denotes a double crucible, 4 denotes a heater, 5 denotes a raw material supply apparatus, and 6 denotes a magnet. FIG. 1 shows a single crystal pulling apparatus employing a continuous charge type magnetic field applying CZ method using a so-called double crucible (hereinafter abbreviated as CMCZ method) which is one of the improved types of the above-mentioned CZ method. It is one. In the CMCZ method, by applying a magnetic field to a semiconductor melt in a crucible from the outside, convection in the semiconductor melt is suppressed, and control of oxygen concentration is excellent and a single crystal having a good single crystallization rate is grown. And a feature that the raw material can be continuously supplied between the outer crucible and the inner crucible to easily obtain a long semiconductor single crystal. Therefore, it is said to be one of the most excellent methods for obtaining a large-diameter and long semiconductor single crystal. In the single crystal pulling apparatus 1, as shown in FIG. 1, a double crucible 3, a heater 4, and a raw material supply device 5 are arranged in a chamber 2 which is a hollow airtight container.
A magnet 6 is arranged outside the chamber 2. The double crucible 3 is made of substantially hemispherical quartz (SiO 2).
₂ ) An outer crucible 11 made of quartz and an inner crucible 12 made of quartz (SiO ₂ ) which is a cylindrical partition member provided in the outer crucible 11. A plurality of communication holes 13 communicating between the crucible 12 and the outer crucible 11 (raw material melting region) and the inside of the inner crucible 12 (crystal growth region) are formed. The double crucible 3 is mounted on a susceptor 15 on a shaft 14 vertically provided vertically below the center of the chamber 2 and has a predetermined angular velocity on a horizontal plane about the axis of the shaft 14. It is configured to rotate.
In the double crucible 3, a semiconductor melt (a raw material of a semiconductor single crystal melted by heating) 21 is stored. At the lower part of the shaft 14, a crucible elevating mechanism R capable of elevating the double crucible 3 to an arbitrary height together with the shaft 14 and the susceptor 15 is provided. The heater 4 heats and melts a semiconductor raw material in a crucible and keeps the semiconductor melt 21 generated. Usually, resistance heating is used. The raw material supply device 5 continuously feeds a predetermined amount of the semiconductor raw material 22 onto the surface of the semiconductor melt 21 between the outer crucible 11 and the inner crucible 12. Further, the raw material supply device 5 is provided with a charging amount adjusting mechanism T capable of arbitrarily adjusting the charging amount of the raw material 22.
have. The magnet 6 applies a magnetic field to the semiconductor melt 21 in the double crucible 3 from outside the double crucible 3, and the Lorentz force generated in the semiconductor melt 21 causes the semiconductor 6 to melt. It controls convection, controls oxygen concentration, suppresses liquid level vibration, and the like. The raw material 2 supplied from the raw material supply device 5
As 2, for example, those obtained by crushing an ingot of polycrystalline silicon with a crusher or the like to form flakes, or granules of polycrystalline silicon obtained by depositing particles from a gaseous material by a pyrolysis method are suitably used, Boron (B) (for making p-type silicon single crystal) or phosphorus (P) as necessary
An additional element called a dopant such as (for forming an n-type silicon single crystal) is further supplied. The same applies to gallium arsenide (GaAs). In this case, the additive element is zinc (Zn) or silicon (Si). Next, a method for growing a semiconductor single crystal in one embodiment of the single crystal pulling method according to the present invention will be described. [Initial Material Melting Step] First, a predetermined amount of a polycrystalline material such as a polycrystalline silicon lump is put into the outer crucible 11, and the inside of the chamber 2 is evacuated by a vacuum pump or the like to be in a vacuum state. In addition, an inert gas such as argon (Ar) is introduced into the chamber 2, and the outer crucible 11 is rotated at a predetermined angular velocity by rotating the shaft 14 on a horizontal plane at a predetermined angular velocity about the axis. The heater 4 is energized to heat the polycrystalline raw material in the outer crucible 11 to a temperature equal to or higher than the single crystal growth temperature, and the raw material is completely melted. [Double crucible forming step] After the raw materials are completely melted, the heating by the heater 4 is slightly weakened.
An inner crucible 12 arranged on the same axis as the outer crucible 11 is placed in the semiconductor melt 21 to form the double crucible 3. [Single Crystal Growth Step] After forming the double crucible 3, the magnet 6 is energized to apply a predetermined magnetic field, the power of the heater 4 is adjusted, and the central liquid level 23 of the semiconductor melt 21 is adjusted.
After keeping the vicinity at the single crystal growth temperature and allowing the seed crystal 25 suspended by the pulling shaft 24 to adapt to the semiconductor melt 21,
Using this seed crystal 25 as a nucleus, a semiconductor single crystal 26 is grown. Here, after the seed crystal is dislocation-free, the diameter of the single crystal is gradually increased to a semiconductor single crystal 26 having a predetermined diameter. With the semiconductor single crystal 26 having a predetermined diameter, a constant diameter portion (a columnar portion) is grown with the output of the heater 4 and the pulling speed of the semiconductor single crystal 26 kept constant. In this single crystal growing step, the diameter of the fixed portion of the semiconductor single crystal 26 is controlled as follows. When the diameter of the semiconductor single crystal 26 becomes larger than the set value, the amount of the raw material 22 is reduced by the charging amount adjusting mechanism T, so that the semiconductor melt 2 by the charged raw material 22 is reduced.
The cooling effect of (1) is reduced to increase the temperature of the melt, and the growth rate of the semiconductor single crystal 26 in the radial direction is reduced. Conversely, when the diameter of the semiconductor single crystal 26 becomes smaller than the set value,
2 by increasing the input amount of the raw material 22
The cooling effect of the semiconductor melt 21 by the above is increased, the melt temperature is lowered, and the growth rate of the semiconductor single crystal 26 in the radial direction is increased. At this time, since the input amount of the raw material 22 is increased or decreased, the input amount does not coincide with the growth amount of the semiconductor single crystal 26, the storage amount of the semiconductor melt 21 changes, and the liquid level L is changed. fluctuate. If the liquid level L changes at a constant pulling speed, the effective growth rate of the semiconductor single crystal 26 changes, and the liquid level L relative to the position of the heater 4 also changes. There is a disadvantage that the temperature near the liquid surface and the temperature distribution deviate from the setting. In order to solve the above-mentioned inconvenience, the amount of rise and fall of the double crucible 3 for correcting the change in the liquid level L calculated from the increase and decrease of the input amount and the growth amount of the semiconductor single crystal 26 is described. Is set in advance. That is, the double crucible 3 is moved up and down by the crucible elevating mechanism R in conjunction with the increase and decrease of the input amount of the raw material 22, and the relative liquid level L of the semiconductor melt 21 with respect to the position of the heater 4 is made constant. Therefore, the diameter of the semiconductor single crystal 26 can be controlled with high responsiveness, the effective growth rate does not fluctuate, and the semiconductor melt 2
The temperature and its temperature distribution in the vicinity of the liquid level 1 can be kept in the set state. As described above, it is possible to grow the semiconductor single crystal 26 having a constant diameter portion with small diameter fluctuation and uniform quality. In this embodiment, the CMCZ method is employed. However, as long as the solid raw material is continuously charged into the crucible, it may be applied to the normal CCZ method without applying a magnetic field. In addition, although the single crystal was grown with the heater output and the pulling speed of the semiconductor single crystal kept constant, even when these were changed, the responsiveness of controlling the single crystal diameter was increased, and the fluctuation of the effective growth rate was suppressed. can do. According to the single crystal pulling method of the present invention, the diameter of the single crystal is controlled by changing the input amount of the solid raw material, and the crucible is moved up and down accordingly, whereby the semiconductor melt is removed. Since the liquid level is set so as to be relatively constant with respect to the position of the heater as a heat source, it is possible to control the single crystal diameter with excellent responsiveness while maintaining the effective growth rate constant,
The temperature and the temperature distribution in the vicinity of the liquid surface of the semiconductor melt can be maintained at the set state. Therefore, high-precision diameter control can be realized, and good single crystal growth with uniform quality can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing one embodiment of a single crystal pulling apparatus employing a single crystal pulling method according to the present invention. [Description of Signs] 1 Single crystal pulling device 2 Chamber (airtight container) 3 Double crucible 4 Heater 5 Raw material supply device 6 Magnet 11 Outer crucible 12 Inner crucible 21 Semiconductor melt 22 Raw material 26 Semiconductor single crystal T Input adjustment mechanism R Crucible lifting mechanism

Continuation of the front page (72) Michio Kida, Inventor Michio Kita 1-297 Kitabukurocho, Omiya City, Saitama Prefecture Mitsubishi Materials Co., Ltd. (56) References JP-A-4-243996 (JP, A) JP-A-1- 122988 (JP, A) JP-A-3-54188 (JP, A) JP-A-7-133186 (JP, A) JP-A-7-133187 (JP, A) JP-A-2-10468 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) C30B 1/00-35/00

Claims (1)

(57) [Claim 1] A semiconductor melt melted by heating of a heater is stored in a crucible provided inside an airtight container, and while the solid raw material is charged into the crucible, In the single crystal pulling method for pulling a long semiconductor single crystal from a semiconductor melt in a crucible, when the semiconductor single crystal is larger than a set diameter, reduce the input amount of the solid raw material, conversely When the diameter of the semiconductor single crystal becomes smaller than the set diameter, the input amount of the solid material is increased, and the increase or decrease of the input amount of the solid material and the growth amount of the semiconductor single crystal are increased.
This is applied to the change in the liquid level of the semiconductor melt calculated from
Set the amount of double crucible lifting to be corrected in advance, and
A single crystal pulling device which raises and lowers the crucible by a crucible raising / lowering mechanism in conjunction with the increase and decrease of the charging amount of the material to keep the relative level of the semiconductor melt relative to the position of the heater constant. Top method.