JPH07300389A - Production of semiconductor single crystal - Google Patents

Abstract

PURPOSE:To suppress the oscillation of liquid surface and prevent the polycrystallization of a semiconductor single crystal in the production of a semiconductor single crystal by a continuous charging method by varying the level of a molten liquid relative to a raw material supplying pipe prior to the start of raw material supplying operation. CONSTITUTION:A raw material supplying part is separated from a single crystal, growing part with a vapor phase by immersing a lower part of a raw material supplying pipe 3 attached to the lower end of a raw material supplying part into a molten liquid 2 stored in a crucible 1. The growing of neck and shoulder parts 5 and the growing of the upper end of a straight cylinder part 6 are carried out exclusively with the molten liquid 2 stored in the crucible 1 by lifting the crucible without feeding a polycrystalline raw material from a raw material supplying pipe 3 to effect the pull-up growing of a semiconductor single crystal. Thereafter the lifting rate of the crucible 1 is lowered to perform the growing of the upper end part of the straight cylinder 6 and vary the level of the molten liquid relative to the raw material supplying pipe 3. After the above procedures, the supply of the polycrystalline raw material from the raw material supplying pipe to the molten liquid 2 is started, the lifting motion of the crucible l is stopped and pulling up of the semiconductor single crystal is carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a semiconductor single crystal which continuously produces a homogeneous semiconductor single crystal by using a continuous charge method.

[0002]

2. Description of the Related Art A high-purity single crystal silicon is mainly used for a substrate of a semiconductor element, and one of the methods for producing this single crystal silicon is the Czochralski method (hereinafter referred to as the CZ method). In the CZ method, a graphite crucible is placed on the upper end of a crucible shaft installed in a chamber of a semiconductor single crystal manufacturing apparatus via a crucible receiver, and a quartz crucible housed in the graphite crucible is filled with polycrystalline silicon. The polycrystalline silicon is heated and melted by a heater provided around the graphite crucible to form a melt. Then, the seed crystal attached to the seed chuck is immersed in the melt, and the seed chuck is pulled up while the seed chuck and the graphite crucible are rotated in the same direction or in the opposite direction to grow single crystal silicon.

In recent years, the diameter of semiconductor wafers has increased,
With the demand for large-diameter wafers exceeding 8 inches, single crystal silicon having a diameter of 8 inches or more is becoming the mainstream. For this reason, the single crystal manufacturing equipment also becomes larger,
The throughput per cycle tends to increase. However, as the size of the single crystal manufacturing apparatus becomes larger, the time required for the single crystal growth step becomes longer, and before and after that, for example, the time required for melting the raw material polycrystal, and after taking out the grown single crystal silicon out of the furnace. The cooling time required for the crucible, the heater, etc. to reach a temperature at which they can be cleaned is longer than before. These are factors that reduce the productivity of single crystal silicon. Further, since the quartz crucible is deformed or cracked due to the heat load applied when the polycrystalline silicon is melted, it is replaced with a new one every time the single crystal silicon is pulled up.

As one of means for efficiently producing large-diameter single crystal silicon by the CZ method, a raw material is supplied into a crucible according to the amount of the pulled single crystal silicon, and the single crystal silicon is continuously pulled up. The charge method is used. FIG. 2 is a partial cross-sectional view schematically showing an example of a semiconductor single crystal manufacturing apparatus using the continuous charging method, and two sets of raw material supply parts 10 are installed above the peripheral edge of the quartz crucible 1. The raw material supply unit 10 melts rod-shaped polycrystalline silicon (hereinafter referred to as a raw material crystal rod) 11 supported from the upper portion of the chamber 9 and drops it into the melt 2. The raw material melting heater 12 and the raw material It comprises a protective cylinder 13 surrounding the melting heater 12, and a quartz raw material supply pipe 3 attached to the lower end of the protective cylinder 13.

The lower end of the raw material supply pipe 3 is immersed in the melt 2,
Vibrations are prevented from propagating to the melt 2 of the single crystal growth portion 20 due to the falling droplets. In addition, the raw material supply unit 10
Forms an independent space isolated from the single crystal growing section 20, and the vapor phase of the raw material supply section 10 and the single crystal growing section 20 are separated. The raw material crystal rods 11 are alternately hung down one by one inside the raw material melting heater 12, and when the melting of the raw material crystal rods on one side is completed, the raw material crystal rods on the other side are melted and the raw material is continuously supplied. . In addition, 4 is a seed chuck, 7
Crucible shaft, 14 main heater, 15 heat insulation tube, 16
Is a melt cover that serves as a discharge passage for the inert gas flowing down the raw material supply section 10, and 17 is single crystal silicon being grown.

[0006]

Quartz is generally used for the raw material supply pipe 3, but the portion of the raw material supply pipe 3 immersed in the melt 2 reacts with the melt 2 as shown in FIG. Then, it is gradually eroded, and a step is formed at the boundary between the eroded portion and the portion above it. When such a raw material supply pipe is used, the melt surface comes into contact with the step and vibration of the liquid surface occurs.
When the semiconductor single crystal under growth receives the liquid surface vibration, it causes polycrystallization.

The present invention has been made by paying attention to the above-mentioned conventional problems, and suppresses the liquid level vibration caused by the contact of the melt surface with the stepped portion of the eroded raw material supply pipe, and the semiconductor single crystal It is an object of the present invention to provide a method for producing a semiconductor single crystal capable of preventing polycrystallization of the above.

[0008]

In order to achieve the above object, in the method for producing a semiconductor single crystal according to the present invention, the lower part of the raw material supply pipe attached to the lower end of the raw material supply part is immersed in the melt stored in the crucible. Thereby, in the gas phase separation of the raw material supply unit and the single crystal growth unit, in the production of a semiconductor single crystal pulling the semiconductor single crystal while continuously supplying the raw material polycrystal to the melt from the raw material supply unit, By displacing the position of the melt surface with respect to the raw material supply pipe before the start of the supply of the raw material polycrystal to the melt from the raw material supply unit or before the start of the supply of the raw material polycrystal and after the end of the supply of the raw material polycrystal, It is characterized by suppressing the liquid surface vibration generated by contact with the liquid surface, and specifically, in growing the neck and shoulder and growing the upper part of the straight body, the raw material polycrystal from the raw material supply part Without supply, only the melt was retained in the crucible while increasing the crucible perform development of the,
Next, the position of the melt surface with respect to the raw material supply pipe is changed by lowering the rising rate of the crucible and growing the upper end of the straight body, and thereafter, the supply of the raw material polycrystal to the melt is started from the raw material supply section. At the same time, it was decided to stop the ascending of the crucible. Furthermore, in addition to the above, when the supply of the raw material polycrystal to the melt from the raw material supply unit is completed and the crucible is raised, the crucible is raised when the semiconductor single crystal is grown by only the melt stored in the crucible. While stopping for a predetermined period, or by changing the position of the melt surface with respect to the raw material supply pipe by growing the semiconductor single crystal by lowering the rate of rise of the crucible, then raise the crucible at a normal rate of rise. You may make it grow the tail.

[0009]

According to the above structure, in the pulling of the semiconductor single crystal by the continuous charge method, the melt surface to the raw material supply pipe is supplied before starting the supply of the raw material polycrystal to the melt or before and after the start of the supply of the raw material polycrystal. It was decided to change the position. Specifically, the raw material polycrystal is not supplied from the raw material supply unit to the melt until the growth of the upper end of the straight body, and the position of the melt surface with respect to the raw material supply pipe is changed by lowering the rising rate of the crucible, Since the melt surface is not brought into contact with the stepped portion of the raw material supply pipe caused by being eroded by the melt, it is possible to suppress the occurrence of liquid level vibration caused by the stepped portion. Furthermore, after the supply of the raw material polycrystal to the melt from the raw material supply unit, the rising of the crucible is stopped for a predetermined period, or it is decided to grow the semiconductor single crystal by lowering the rising rate of the crucible. The relative position between the raw material supply pipe and the melt surface changes during the period, and the occurrence of liquid level vibration is suppressed. By performing such an operation, even if there is a step in the raw material supply pipe that is immersed in the melt, the occurrence of liquid level vibration is suppressed, and it is possible to prevent polycrystallization of a single crystal.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for producing a semiconductor single crystal according to the present invention will be described below with reference to the drawings. Figure 1
It is a schematic diagram which showed the semiconductor single crystal pulling process in time series. In FIG. 1A, a melt 2 formed by melting a raw material polycrystal is stored in a crucible 1, and a lower portion of a raw material supply pipe 3 attached to a lower end of a raw material supply section is immersed in the melt 2. There is. The lower end of the seed crystal attached to the seed chuck 4 is dipped in the melt 2 to be blended, the seed chuck 4 is pulled up to grow a neck, and then the shoulder 5 is grown. After the shoulder 5 has been grown, as shown in FIG. 1 (b), a straight body growing step is started to grow the straight body 6 to an axial length of about 50 mm. During the period from the neck growth to the straight body length growth of about 50 mm, the raw material supply unit does not supply the raw material to the melt 2, and the crucible is used to keep the melt surface position with respect to the main heater (not shown) at a predetermined position. The shaft 7 is driven to raise the crucible 1.

In the straight body growing step, the raw material is not continuously supplied from the raw material supply section to the melt 2 during the axial length of the straight body 6 from about 50 mm to about 100 mm, and the ascending rate of the crucible 1 is normally set. Drop to 1/2. As a result, as shown in FIG. 1C, the melt surface position with respect to the raw material supply pipe 3 attached to the lower end of the raw material supply section is gradually lowered,
During this time, the contact position of the melt surface with respect to the raw material supply pipe 3 changes little by little. Therefore, the melt surface does not continuously come into contact with the same position of the eroded raw material supply pipe 3, and the generation of the liquid level vibration due to the step of the raw material supply pipe 3 is suppressed.

In the straight body part growing step, after the axial length of the straight body 6 of about 100 mm, the raw material supply section starts the raw material supply. That is, as shown in FIG. 1D, a raw material melting rod (not shown) melts the raw material crystal rod, and the droplets are supplied to the melt 2 through the raw material supply pipe 3. At this time, the ascending of the crucible 1 is stopped.

After melting an arbitrary number of raw material crystal rods and supplying them to the melt, the raw material supply section completes the supply of the raw material. From this point, the growth of the semiconductor single crystal is continued while raising the crucible 1 at a normal rate of increase.
As shown in FIG. 3, the raising of the crucible 1 is stopped for the growing of the lower end portion of the straight body 6 of about 20 mm. During this time, since the melt surface gradually descends, the contact position of the melt surface with the raw material supply pipe 3 also gradually changes, and vibration of the melt surface is suppressed. A method of lowering the rate of rise of the crucible 1 below a normal value may be used when growing the lower end portion of the straight body 6 of about 20 mm.

After the growth of about 20 mm at the lower end of the straight body 6 is completed, the tail 8 is grown as shown in FIG. 1 (f).
In raising the tail 8, the crucible 1 is raised at a normal rate of increase. In this case, since the melt surface descends as the melt 2 decreases, the lower end of the raw material supply pipe 3 separates from the melt 2.

In the present embodiment, even when a raw material supply pipe having a step due to erosion is used, by performing the above operation, the single crystal extending from the position of about 50 mm at the upper end of the straight body to the lower end, that is, the boundary with the tail. During the growth, the contact position of the melt surface with the raw material supply pipe is at a position other than the step portion.
For this reason, the liquid level vibration that has conventionally occurred due to the contact of the melt surface with the stepped portion of the raw material supply pipe is suppressed, and the polycrystallization of the grown single crystal can be prevented. Further, during tail growth, the melt surface position with respect to the raw material supply pipe is displaced along with the decrease in the melt, and finally the lower end of the raw material supply pipe is separated from the melt, so that liquid surface vibration does not occur.

In the present embodiment, the raw material polycrystal is not supplied from the raw material supply portion to the neck and shoulder growth and the position of the upper end of the straight body of about 100 mm, and the crucible is located between the upper end of the straight body of about 50 mm and about 100 mm. The rate of increase was set to 1/2 of that during normal single crystal growth, but it is not limited to this, and the supply start time of the raw material polycrystal, the rate of increase in the crucible, and the growth site are determined according to the position of the step of the raw material supply pipe used. The axial length of is to be selected appropriately. Similarly, the supply end time of the raw material polycrystal, the crucible rising stop period or the crucible rising rate may be selected according to the capacity of the crucible and the position of the step of the raw material supply pipe. Further, not only the method of melting the raw material crystal rod and supplying the droplets to the melt but also the method of directly charging the granular raw material polycrystal into the melt through the raw material supply pipe whose lower end is immersed in the melt The present invention can be applied to the method.

[0017]

As described above, according to the present invention, as one of the causes of the vibration of the melt surface in the pulling of the semiconductor single crystal using the continuous charge method, the erosion of the raw material supply pipe immersed in the melt is caused. Focusing on the point that the melt surface comes into contact with the step portion formed by, the supply period of the raw material polycrystal to the melt is limited as a means for avoiding the contact of the melt with the step portion. Then, before the start of the supply of the raw material polycrystal or before the start of the supply of the raw material polycrystal and after the end of the supply, the melt surface position with respect to the raw material supply pipe is displaced by lowering the rising rate of the crucible or stopping the rising of the crucible. Since the melt surface is not brought into contact with the stepped portion of the raw material supply pipe caused by the reaction with the melt, the occurrence of liquid surface vibration is suppressed in most of the semiconductor single crystal growing step. By performing such an operation, even if there is a step in the raw material supply pipe that is immersed in the melt, it is possible to prevent polycrystallization of the single crystal, and the number of defective products is drastically reduced. Can be improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing a semiconductor single crystal pulling process in time series, where (a) is a neck and a shoulder, (b),
(C), (d) and (e) show a straight body, and (f) shows a tail growing process.

FIG. 2 is a partial cross-sectional view schematically showing an example of a semiconductor single crystal manufacturing apparatus using a continuous charge method.

FIG. 3 is a cross-sectional view of a raw material supply pipe in which a portion immersed in a melt is eroded and its peripheral portion.

[Explanation of symbols]

 1 Crucible 2 Melt 3 Raw Material Supply Pipe 5 Shoulder 6 Straight Body 8 Tail 10 Raw Material Supply Section 17 Single Crystal Silicon 20 Single Crystal Growth Section

Claims (3)

[Claims] 1. A raw material supply pipe attached to the lower end of a raw material supply part is immersed in a melt stored in a crucible to separate the raw material supply part and the single crystal growing part into a gas phase, and the raw material supply part is supplied. In the production of a semiconductor single crystal that pulls a semiconductor single crystal while continuously supplying a raw material polycrystal to the melt from a part, before starting the supply of the raw material polycrystal to the melt from the raw material supply part or supplying the raw material polycrystal By displacing the position of the melt surface with respect to the raw material supply pipe before the start and after the end of the supply, a semiconductor single crystal characterized by suppressing the liquid surface vibration caused by the contact between the raw material supply pipe and the melt surface Production method. 2. When growing a neck and a shoulder and a straight upper end of a straight body, a raw material polycrystal is not supplied from a raw material supply section, and the above-mentioned growth is performed only by a melt stored in a crucible which is raising a crucible. And then change the position of the melt surface with respect to the raw material supply pipe by lowering the rate of rise of the crucible and growing the straight body upper end, and then supplying the raw material polycrystal to the melt from the raw material supply section. 2. The method for producing a semiconductor single crystal according to claim 1, wherein the ascending of the crucible is stopped at the same time as the starting. 3. When the supply of the raw material polycrystal to the melt from the raw material supply unit is completed and the crucible is being raised, the rising of the crucible is predetermined when the semiconductor single crystal is grown only by the melt stored in the crucible. The position of the melt surface with respect to the raw material supply pipe is changed by either stopping for a period of time or by lowering the rising rate of the crucible to grow the semiconductor single crystal, and then raising the crucible at the normal rising rate while the tail is raised. 2. The method for producing a semiconductor single crystal according to claim 1, wherein the growth is performed.