JPH06271388A - Production of semiconductor single crystal rod - Google Patents

Abstract

PURPOSE:To produce a semiconductor single crystal rod excellent in quality with high production efficiency without increasing cost. CONSTITUTION:When a seed crystal is brought into contact with a semiconductor melted in a crucible and a semiconductor single crystal is grown by slowly pulling up the seed crystal to produce a semiconductor single crystal rod, the single crystal is grown while periodically varying the rate of pulling-up of the seed crystal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor single crystal ingot by the Czochralski method.

[0002]

2. Description of the Related Art A semiconductor single crystal manufactured by the Czochralski (hereinafter abbreviated as CZ) method is used for manufacturing a semiconductor single crystal ingot used for manufacturing various integrated circuits, particularly a silicon single crystal. . As a semiconductor single crystal ingot by the CZ method, there is a demand for a method for producing dislocations and various crystal defects as much as possible and for manufacturing the semiconductor single crystal ingot at a lower cost.

As a conventional method for producing a large diameter (50 mm or more) dislocation-free silicon single crystal rod rod by the CZ method, a single crystal rod pulling rate is 1.2 mm / min or more (for example, Takao Abe "Super. "LSI Process Data Handbook" (published April 15, 1982), Science Forum Co., Ltd., p. 64) is disclosed. In this conventional technique, a dislocation-free large-diameter silicon single crystal rod is 1.2 m
Since it is grown at a pulling rate of m / min, the production efficiency is good, but the quality of the single crystal has problems such as generation of OSF, generation of oxygen precipitates and deterioration of oxide film withstand voltage characteristics.

The pulling speed of the single crystal rod is 0.8 mm.
Although a method of less than 1 / minute is disclosed in Japanese Patent Application Laid-Open No. 2-267,195, the method of this prior art is OSF,
There are few crystal defects such as oxygen precipitates, and the oxide film withstand voltage characteristics are improved, etc., but the quality of the single crystal is excellent, but the production speed is low due to the slow pulling rate, resulting in high cost and impracticality. There is.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for producing a semiconductor single crystal ingot which has high production efficiency and high quality without increasing cost.

[0006]

[Problems to be Solved by the Invention] The above-mentioned objects are to produce a semiconductor single crystal ingot which grows a semiconductor single crystal by bringing a seed crystal into contact with a semiconductor melt which melts in a crucible and gradually pulling this seed crystal. In the method, it is achieved by a method for manufacturing a semiconductor single crystal ingot, which comprises growing the single crystal while periodically changing the pulling rate of the seed crystal.

Further, the above-mentioned objects are to provide a method for manufacturing a semiconductor single crystal ingot, wherein a seed crystal is brought into contact with a semiconductor melt which melts in a crucible, and the semiconductor single crystal is grown by gradually pulling the seed crystal. The seed crystal is brought into contact with a melt, and after the semiconductor single crystal grows from the semiconductor melt to the seed crystal to grow to a desired semiconductor single crystal rod diameter, the pulling rate of the semiconductor single crystal rod is set to the minimum rate. Is 0.2 to 0.
8 mm / min, maximum speed is 1.2-2.0 mm / min, 1 from the lowest speed to the highest speed to the next lowest speed
It can also be achieved by a method for manufacturing a semiconductor single crystal ingot, which comprises pulling up the semiconductor single crystal ingot while repeating the minimum speed and the maximum speed by changing the cycle to be 5 to 60 minutes.

[0008] Further, the above objects are to provide a method for producing a semiconductor single crystal in which a seed crystal is brought into contact with a semiconductor melt which melts in a crucible, and the semiconductor single crystal is grown by gradually pulling the seed crystal. A step of growing the crystal at a rate of 0.55 mm / min or more until the crystal growth length is 50 mm at the longest, and a step of maintaining the pulling rate at a rate of 0.4 mm / min or less for 30 minutes or more. It can also be achieved by a method for manufacturing a semiconductor single crystal, which is characterized in that the semiconductor single crystal is grown while alternately repeating and.

[0009]

The present invention provides a seed crystal which is brought into contact with a semiconductor melt,
After the growth of the single crystal begins and the diameter of the desired thickness is obtained,
Crystal growth is performed while periodically changing the pulling rate of the seed crystal. This is the OS in the semiconductor single crystal rod.
The boundary between the crystal defect generation regions where F, oxygen precipitation defects, etc. are generated and the interphase relationship between the crystal growth rates are used. Normally, the boundary between the crystal defect generation regions in the semiconductor single crystal rod has a high crystal growth rate. Then, it moves to the outside of the crystal rod and occurs in the whole semiconductor single crystal rod, and slows down the growth rate, so that the boundary of the crystal defect generation region moves to the center of the semiconductor single crystal rod and further slows down the growth rate. As a result, the boundary moved to the center disappears, and a semiconductor single crystal ingot having no defect layer is completed over the entire semiconductor single crystal ingot.

When the growth rate of the single crystal is changed, that is, when the pulling rate of the semiconductor single crystal rod is changed, there is a hysteresis between the crystal growth rate and the movement of the boundary between the crystal defect generation regions. Therefore, for example, even if the pulling speed is changed from a low speed to a high speed, the boundary of the crystal defect occurrence region that has disappeared once with the pulling speed slowed sufficiently,
It does not appear immediately after the pulling speed is increased, but when a high pulling speed is maintained to some extent, a boundary between crystal defect regions appears and a crystal defect occurs. Therefore, even if the pulling rate is increased, if the pulling rate is lowered before the crystal defect generation boundary appears, crystal defects do not occur in the semiconductor single crystal rod, and the pulling time as a whole semiconductor single crystal rod manufacturing is increased. The manufacturing time can be shortened by the amount corresponding to the portion where the pulling speed is increased.

[0011]

EXAMPLES The present invention will be described in detail below with reference to examples.

Example 1 The semiconductor single crystal ingot pulling apparatus used in the method for producing a semiconductor single crystal ingot according to the present invention is not particularly limited as long as it is usually used for pulling a semiconductor single crystal ingot by the CZ method. Instead, in this embodiment, a CZ method semiconductor single crystal rod pulling apparatus as shown in FIG. 1 was used.

This CZ method semiconductor single crystal rod pulling apparatus 1
Has a chamber 2 mainly composed of a heating chamber 2a containing a structure for melting silicon and a pulling chamber 2b containing a pulled silicon single crystal ingot S separated and connected by the separating mechanism 20. Then, in the heating chamber 2a, a crucible 5 composed of a quartz crucible 5a and a graphite crucible 5a for protecting the quartz crucible 5, a heating heater 6 arranged so as to mainly surround a side surface portion of the crucible 5, and a heating A heat insulating member 11 is provided in order to prevent heat from the heater 6 from escaping to the outside of the heating chamber 2a. The crucible 5 is connected to a driving device (not shown) by a rotary shaft 4 and is driven by the driving device. And the crucible 5 is moved up and down in order to compensate for the decrease in the silicon melt liquid level as the silicon melt in the crucible 5 decreases. It is made as to the cause.

Inside the pulling chamber 2b, there is provided a pulling wire 7 penetrating through the top wall, and a chuck 9 for holding a seed crystal 8 is provided at the lower end of the pulling wire 7.
Is provided. The upper end side of this pulling wire 7 is
A pulling device that is wound around the wire hoisting machine 10 and that pulls up the silicon single crystal rod S is provided.

Argon gas is introduced into the chamber 2 through the gas introduction port 12 formed in the pulling chamber 2b, and the argon gas is evenly distributed in the heating chamber 2a and discharged from the gas outlet port 13. The reason why the argon gas is circulated in this way is to prevent the SiO generated in the chamber 2 due to the melting of silicon from being mixed into the silicon melt.

A method for manufacturing a silicon single crystal ingot according to the present invention using the above semiconductor single crystal ingot pulling apparatus will be described below.

FIG. 2 is a drawing showing the change in the pulling speed from the periodic minimum speed to the maximum speed according to the present invention. Note that, in FIG. 2, the start time is 0 minutes when the single crystal starts to grow from the seed crystal and reaches a desired crystal diameter.

In the first embodiment, by utilizing the hysteresis until the appearance of the crystal defect generation boundary with respect to the change of the growth rate, the growth of the single crystal is started, and after the diameter of the desired thickness is obtained, the semiconductor single crystal is obtained. The minimum speed of pulling up the rod is reduced to 0.2 to 0.8 mm / min, the crystal defect generation boundary is once eliminated, and then the maximum speed is 1.2 to 2.0 m.
Increase the pulling speed to m / min and then lower the pulling speed to the minimum speed. By repeating this cycle for 5 to 60 minutes for one cycle from the lowest speed to the highest speed and then to the next lowest speed, it is possible to efficiently manufacture a semiconductor single crystal ingot having no OSF or oxygen precipitation defects.

Here, the minimum pulling speed is 0.2 mm /
If it is less than min, the growth in the pulling direction of the semiconductor single crystal rod is stopped, which is not realistic. If it exceeds 0.8 mm / min, the diameter is about 50 mm or more, depending on the diameter of the semiconductor single crystal rod to be manufactured. In the case of a semiconductor single crystal ingot having a large diameter, it is not preferable because the crystal defect generation boundary cannot be eliminated. On the other hand, if the maximum speed is less than 1.2 mm / min, even if the pulling speed is increased, a great effect cannot be obtained in shortening the entire manufacturing time. If it exceeds 2.0 mm / min, the pulling speed is too fast. Therefore, the crystal growth does not go well and the semiconductor single crystal ingot is cut or thinned in the middle, which is not preferable. When the time for one cycle is less than 5 minutes, the crystal growth does not proceed well because the pulling speed changes too rapidly.
If the amount exceeds the limit, the pulling time at high speed becomes too long, so that a crystal defect generation boundary appears and crystal defects occur in the semiconductor single crystal rod, which is not preferable.

The manufacturing method will be described more specifically below.
First, when manufacturing the silicon single crystal ingot S, the pulling chamber 2b is moved to the heating chamber 2 by the separating mechanism 20.
After separating from a, a very small amount of impurities are introduced into the crucible 5 to obtain a raw silicon crude crystal and a desired silicon single crystal type (n type or p type), and the pulling chamber 2b is raised by the separating mechanism 20. It is attached to the heating chamber 2a. In this state, argon gas is introduced into the chamber 2 through the gas inlet 12
Further, the introduced argon gas is discharged from the gas discharge port 13, an argon gas flow is caused to flow so that the inside of the chamber 2 is slightly decompressed (several Torr), and the heater 6 is heated in the crucible 5. Wait for the silicon to melt. When the silicon is in a molten state, the wire winding machine 10 is operated to lower the pull-up wire 7 so that the seed crystal attached to the chuck 9 is in contact with the surface of the silicon melt. In this state, silicon crystals started to grow on the seed crystal, and when the desired diameter of the silicon single crystal rod S was obtained, the wire hoisting machine 10 was pulled up at a speed of 1.5 mm / min. Grow body S.
This pulling rate (1.5 mm / min) is maintained for about 10 minutes in order to pull up the silicon single crystal ingot S with a desired diameter.

Then, after confirming that the silicon single crystal ingot S is pulled up while maintaining a desired diameter, the pulling speed is lowered until the minimum speed becomes 0.4 mm / min. At this time, when the crystal diameter is large, for example, exceeding 50 mm,
In the case of 125 mm, 150 mm or more, which is often used at present, when the minimum speed (0.4 mm / min) is reached, this minimum speed (0.4 mm / Min) for several minutes. This is because there is hysteresis before the crystal defect occurrence boundary disappears, so the boundary does not disappear immediately after the speed reaches the minimum speed.Especially, when the crystal diameter becomes large, the pulling speed becomes slower. It takes several minutes until the crystal defect generation boundary disappears.

After the crystal defect generation boundary disappears in this way, the pulling speed is changed from the minimum speed to the maximum speed of 1.5 mm /
After increasing the pulling speed to the minute and reaching the maximum speed,
Reduce the pulling speed to the minimum speed of 0.4 mm / min. After that, change the speed from the minimum speed to the maximum speed, and change the speed from the minimum speed to the maximum speed for 30 cycles per cycle from the next minimum speed.
The silicon single crystal ingot S is grown while repeating as a minute.

As shown in FIG. 3, the crystal defects and OSF of the silicon single crystal ingot S thus obtained are only present in a small portion on the top side in the initial stage of pulling up of the silicon single crystal ingot S, and the pulling speed is increased. After the crystal defect generation boundary is eliminated by sufficiently lowering the crystal defect generation boundary and before the crystal defect generation boundary appears even if the pulling speed is increased, the pulling speed is also slowed down, so that the crystal defect in the silicon single crystal rod is reduced. Is not generated, and by repeating the change in the pulling speed from the minimum speed to the maximum speed, a silicon single crystal rod in which a defect-free region having no crystal defects is formed over the entire silicon single crystal rod can be obtained.

In Example 1, the pulling rate of the whole silicon single crystal ingot was about 1.0 mm / min on average, and 0.8 mm when a silicon single crystal ingot having no crystal defect was produced by the conventional method. A silicon single crystal ingot having no crystal defects can be pulled up faster than the pulling rate of not more than / min.

Here, the difference in the average pulling speed between the conventional method and the method of the present invention is 0.
Although it is about 2 mm / min, the size of the silicon single crystal ingot is usually over 1 m in the actual production. For example, in the case of producing 1 m of the silicon single crystal ingot, it takes about 4 hours or more. The manufacturing time can be shortened. Furthermore, in the above-described Example 1, the batch type single crystal ingot production is performed. However, while continuously replenishing the melted silicon melt with the crude silicon crystals, the thickness of 1.5 mm or In the production of a continuous type single crystal ingot for producing a silicon single crystal ingot having a length exceeding 2 mm, the present invention can significantly reduce the production time, and moreover, the silicon single crystal obtained in Example 1 can be obtained. The crystal rod is of good quality with no crystal defects.

Examples 2 to 11 and Comparative Examples 1 to 5 FIG. 4 is a drawing showing patterns of changes in pulling speed of other examples according to the present invention. The manufacturing apparatus used for manufacturing the single crystal ingot is the same as that used in Example 1.

In the production methods of Examples 2 to 10, the pulling rate in the first stage of crystal growth is 0.55 mm / min or more, preferably 0.55 to 1.3 m, from the viewpoint of productivity.
It needs to be m / min.

After the crystal is grown at a rate of 0.55 mm / min or more, the pulling rate is kept at 0.4 mm / min or less, preferably 0.4 to 0.2 mm / min. The point defects taken in during solidification diffuse to the melt side and reduce the supersaturation level of the defects.

Then, a single crystal is grown while repeating pulling at a rate of 0.55 mm / min or more and pulling rate of 0.4 mm / min or less to thereby increase the degree of supersaturation of point defects taken during crystal solidification. It is possible to manufacture a semiconductor single crystal in the lowered state. At this time, 0.
The crystal growth length at a speed of 55 mm / min or more is 5 at the longest.
0 mm, preferably 30 to 50 mm, while 0.4
The crystal growth time at a low speed of mm / min or less is 30 minutes or more,
It is preferable to maintain the temperature for 30 to 60 minutes. In addition, preferably, in the final stage of pulling, the growth rate is set to 0.4 mm / min or less so that the point defects taken in at the growth rate of 0.55 mm / min or more sufficiently diffuse to the melt side, The defects are not frozen while the degree of supersaturation is high, and the breakdown voltage of the oxide film is improved.

In FIG. 4, A shows the growth rate at an initial pulling rate of 0.55 mm / min or more and the subsequent growth at a rate of 0.55 mm / min or more, and B shows B. Growth rate at a rate of 0.55 mm / min or more shows a slow growth rate part when the pulling rate after growth at 0.4 mm / min or less, and C indicates a growth rate of 0.55 mm / min or more. The crystal growth length under the growth rate is shown, and D shows the growth time under the low growth rate B.

Under the conditions shown in Table 1 for A to D in FIG.
A silicon single crystal having a length of 500 mm was grown. The single crystal diameter, C-mode pass rate, and single crystal growth time in that case are shown in the same table.

[0032]

[Table 1]

Oxide film breakdown voltage evaluation method For evaluation of the oxide film breakdown voltage, a mirror wafer is manufactured from the entire length of the grown silicon single crystal rod excluding the cone portion and tail portion, and a MOS diode is formed on all the wafers.
25.0 formed in a dry oxygen atmosphere at 1,000 ° C
This is done by examining the electrical characteristics of the gate oxide film, which is a silicon dioxide film of nm. The MOS diode has a two-layer structure of polycrystalline silicon and aluminum in which 1 × 10 ²¹ cm ⁻³ or more of phosphorus is doped on the gate oxide film, and has an area of 1
It has an electrode of 9.63 mm ² , and an aluminum electrode is formed on the back surface for an ohmic electrode. 100 MOS diodes having the above structure were formed per wafer.

As an evaluation index of the oxide film withstand voltage, the electric field applied to the gate oxide film at the time when a current of 1 μA / cm ² flows through the above-mentioned electrode occupies the total number of the MOS diodes having 8 MV / cm or more. The ratio was defined as the C-mode pass rate, and the C-mode pass rate of the lowest wafer among the mirror wafers manufactured from the single-crystal rod was defined as the C-mode pass rate of the single-crystal rod.

The productivity evaluation index was the time for growing a single crystal having a fixed crystal diameter and a length of 500 mm. In Comparative Examples 1 to 4 shown in the same table, the growth rates A and B, the growth length C and the growth time D are out of the range of the present invention, and Comparative Example 5 is disclosed in JP-A-2-267195. It has been disclosed, that is, the case where the crystal is grown at a constant pulling rate of 0.5 mm / min and the crystal growth is performed by a crystal growth method having an oxide film breakdown voltage similar to that of an epitaxial wafer.

From the results shown in the table, the example of the present invention is C
It was possible to grow a single crystal having a length of 500 mm and a good withstand voltage of an oxide film with a mode pass rate of more than 90% in 16.3 hours at the longest. On the other hand, in Comparative Examples 1 to 3, the crystal growth rate B at a low speed, the crystal growth length C at a high growth rate, or the crystal growth time D at a low growth rate was obtained.
Is out of the scope of the present invention, and does not have the oxide film breakdown voltage like an epitaxial silicon wafer. In Comparative Example 4, the crystal growth rate A at a rate of 0.55 mm / min or more is out of the range of the invention, and although the oxide film withstand voltage is good, the productivity is improved as compared with Comparative Example 5. Not done. Furthermore, in the case of Comparative Example 5, Examples 2 to 11
It was inferior in productivity at a maximum of 1.7 times compared to.

[0037]

As described above, according to the method for manufacturing a semiconductor single crystal ingot of the present invention, the pulling rate of the semiconductor single crystal ingot which has no OSF and oxygen precipitation defects and has improved oxide film withstand voltage can be increased as a whole. It can be manufactured efficiently without slowing down. In particular, when manufacturing a semiconductor single crystal ingot having a large diameter or a long single crystal ingot, an excellent effect of cost reduction can be obtained.

[Brief description of drawings]

FIG. 1 is a drawing for explaining a semiconductor single crystal rod pulling apparatus used in an example of the present invention.

FIG. 2 is a drawing showing a change in pulling speed according to the first embodiment of the present invention.

FIG. 3 is a schematic sectional view of a silicon single crystal ingot obtained according to Example 1 of the present invention.

FIG. 4 is a diagram showing a change in pulling speed according to a second embodiment of the present invention.

[Explanation of Codes] 1 ... Semiconductor single crystal ingot manufacturing apparatus, 2 ... Chamber, 2a ... Heating chamber, 2b ...
Lifting chamber, 3 ... Lifting chamber,
4 ... Rotary axis, 5 ... Crucible,
5a ... Graphite crucible, 5b ... Quartz crucible,
6 ... Heater, 7 ... Wire,
9 ... Chuck, 10 ... Wire hoist, 11 ... Heat insulating material, 12 ... Gas inlet, 13 ... Gas outlet, 2
0 ... Separation mechanism.

Front page continued (72) Inventor Shunta Naito 3434 Shimada, Hikari City, Yamaguchi Prefecture Nittetsu Electric Co., Ltd. (72) Inventor Kiyo Kojima 3434 Shimada, Hikari City, Yamaguchi Prefecture Nittatsu Electric Co., Ltd. (72) Invention Person Shigeo Takao 3434 Shimada, Hikari City, Yamaguchi Prefecture Nippon Steel Corporation Hikari Steel Works Co., Ltd.

Claims (3)

[Claims] 1. A method for manufacturing a semiconductor single crystal ingot, wherein a seed crystal is brought into contact with a semiconductor melt that melts in a crucible, and the semiconductor single crystal is grown by gradually pulling the seed crystal. A method of manufacturing a semiconductor single crystal ingot, which comprises growing a single crystal while periodically changing the temperature. 2. A method for producing a semiconductor single crystal ingot, wherein a seed crystal is brought into contact with a semiconductor melt that melts in a crucible, and the semiconductor single crystal is grown by gradually pulling the seed crystal, wherein After the seed crystal is brought into contact with the seed crystal, the semiconductor single crystal grows from the semiconductor melt to a desired semiconductor single crystal rod diameter, and then the pulling rate of the semiconductor single crystal rod is set to a minimum rate of 0.2. ~ 0.8 mm / min, maximum speed is 1.2-2.0 mm / min, and one cycle from the lowest speed to the highest speed to the next lowest speed is changed to 5 to 60 minutes A method for producing a semiconductor single crystal ingot, comprising pulling the semiconductor single crystal ingot while repeating the speed and the maximum speed. 3. A method for producing a semiconductor single crystal in which a seed crystal is brought into contact with a semiconductor melt that melts in a crucible, and the seed crystal is gradually pulled up to produce a semiconductor single crystal. Alternately, the step of growing at a rate of 0.55 mm / min or more and the step of growing at a rate of 0.4 mm / min or less for 30 minutes or more are alternately performed until the crystal growth length is up to 50 mm. A method for producing a semiconductor single crystal, which comprises repeatedly growing the semiconductor single crystal.