JP3207573B2 - Method and apparatus for producing single crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a single crystal used as a material of a single crystal substrate for manufacturing a semiconductor circuit, and more particularly, to a method for reducing the amount of oxygen precipitated from a single crystal. The present invention relates to a method and an apparatus for producing a single crystal body which is made uniform regardless of the above.

[0002]

2. Description of the Related Art In the field of semiconductor manufacturing, the Czochralski method has been generally used as a method for growing a silicon single crystal. As an example of an apparatus using this method, for example, an apparatus as shown in FIG. 4 (JP-A-63-319293) and FIG. 5 (JP-A-64-65086) can be exemplified.

An apparatus 1 shown in FIG. 4 comprises a heating chamber 2a for mainly containing a structure for melting silicon and a pulling chamber 2 for storing a silicon crystal S to be pulled.
The crucible 5 and the heater 6 arranged so as to surround mainly the side surface of the crucible 5 are provided in the heating chamber 2a. The crucible 5 contains the silicon melted by the heater 6. The crucible 5 is connected to a driving device (not shown) by the rotating shaft 4, and is rotated at a predetermined speed by the driving device. Usually, the crucible 5 includes a quartz crucible 5a and a graphite crucible 5b for protecting the quartz crucible 5a.

On the other hand, a pull-up wire 7 is provided in the pull-up chamber 2b and penetrated through the top wall, and a chuck 9 for holding a seed crystal 8 is provided at a lower end of the pull-up wire 7. The upper end side of the pulling wire 7 is wound around a wire hoist 10 so as to pull up the silicon crystal S at a predetermined speed. The heat insulating member 11 is provided on the heating chamber 2a side of the illustrated heater 6 in order to prevent heat from the heater 6 from escaping to the outside of the heating chamber 2a.

In the chamber 2, a lifting chamber 2b
Argon gas is introduced from the gas inlet 12 formed in the heating chamber 2a, and flows through the heating chamber 2a evenly as shown in FIG. The reason why the argon gas is made to flow in this way is to prevent carbon dioxide gas generated in the chamber 2 due to the melting of silicon from being mixed into the silicon melt. In the pulling chamber 2b, the portion above the silicon crystal to be pulled (temperature is lower than 1000 ° C.) is rapidly cooled, while the portion near the solid-liquid interface of the silicon melt (temperature is higher than 1000 ° C.) is gradually cooled. The cooling control member 14 which functions is mounted. The portion of the cooling control member 14 in contact with the lifting chamber 2b is configured to promote cooling of the silicon crystal.
The portion extending in a cone shape in b is configured to reflect the radiant heat from the molten silicon to the silicon crystal body S side. By the action of the cooling control member 14,
The temperature history of the growing silicon single crystal is made uniform so that the thermal history of the silicon crystal becomes closer to the ideal, and in particular, the amount of precipitated oxygen in the silicon crystal can be reduced.

The device having the structure shown in FIG. 5 is also similar to the device shown in FIG. 4 in that the gas flow is improved so that the silicon crystal S is given an ideal thermal history. Since most parts of the configuration shown in this figure are the same as those shown in FIG. 4, the same members are denoted by the same reference numerals. The only difference from the configuration of the apparatus shown in FIG. 4 is that a cylinder 15 extending from the heating chamber 2a to the vicinity of the solid-liquid interface is attached, and an inverted conical collar 16 is attached to the tip.

The presence of the cylinder 15 ensures that the argon gas supplied from the gas inlet 12 always passes through the cylinder 15 and is introduced into the chamber 2 from the solid-liquid interface. The side will be quenched. The collar 16 blocks molten silicon and radiant heat from the heater 6, thereby making it possible to adjust the thermal history of the silicon crystal S being pulled up over a wide range.

[0008]

However, in the conventional single-crystal body manufacturing apparatus capable of obtaining an ideal heat history, the heat history is controlled by the heater 6 or the silicon melt. Since the radiant heat from the above is simply used, the control of the heat history has a certain limit. Therefore, although the amount of precipitated oxygen is certainly suppressed, its effect is not sufficient, and it has not been possible to completely prevent the yield in the integrated circuit manufacturing process from lowering. Further, when a quality index called an oxide film breakdown voltage, which is said to correspond well to the yield in the integrated circuit manufacturing process, was examined, no significant improvement was observed although it was somewhat better than the conventional method.

Further, when the amount of precipitated oxygen of the single crystal produced by the apparatus shown in FIG. 4 is examined, as shown in FIG. 6, the amount of precipitated oxygen is not large at the top and bottom sides of the crystal. You can see that it is uniform. When the amount of precipitated oxygen is not uniform, there is a problem that the yield when manufacturing a semiconductor integrated circuit using the silicon single crystal thus produced is reduced. In order to prevent this, conventionally, the length of the silicon single crystal is limited to a short length, and when the crystal is completed, the crystal is prevented from plunging into the upper chamber 2c, the amount of oxygen precipitation is suppressed to a small level, and the uniformity is maintained. Keeping has been done.

However, in this method, the straight portion that can be processed on the wafer is shortened, and the ratio of the head to the tail is increased. This causes not only a decrease in yield but also a problem of poor production efficiency. there were.

The present invention has been made in view of such conventional problems, and positively adjusts the temperature of a single crystal body by a heater installed at a predetermined distance from a solid-liquid interface. Accordingly, it is an object of the present invention to provide a method of producing a single crystal having a uniform amount of precipitated oxygen while realizing an ideal heat history and an apparatus therefor.

In order to achieve the above object, the present invention provides a method for producing a single crystal in which a single crystal is grown by bringing a seed crystal into contact with a melt to be melted in a crucible and gradually raising the seed crystal. A ring-shaped heater that generates heat by electric power supplied from the outside is supported by a support member also serving as an electrode, and is separated from the solid-liquid interface of the melt by a predetermined distance and pulled up from 900 ° C. to 1100 ° C. Present
The single crystal body is arranged so as to surround the single crystal body at a position near the outer peripheral surface of the portion to be heated, and a predetermined power is supplied to the heater to gradually cool the outer peripheral surface of the single crystal body to be pulled up. It is assumed that.

Further, in a method for manufacturing a single crystal in which a single crystal is grown by bringing a seed crystal into contact with a melt melted in a crucible and gradually pulling the seed crystal, heat is generated by electric power supplied from the outside. An annular heater is supported by a support member that also serves as an electrode, and surrounds the single crystal at a position away from the solid-liquid interface of the melt by a predetermined distance and near the outer peripheral surface of the single crystal pulled up. Until the single crystal body is pulled up a predetermined distance, a predetermined power is supplied to the heater to gradually cool the outer peripheral surface of the single crystal body that is pulled up, and thereafter, the power supplied to the heater is reduced. It is characterized in that cooling is promoted to reduce the outer peripheral surface of the single crystal body.

Further, in a single crystal manufacturing apparatus for pulling up and growing a single crystal from a melt melted in a crucible,
A portion which is separated from the solid-liquid interface of the melt by a predetermined distance and pulled up and which is located near the outer peripheral surface of a portion exhibiting 900 ° C. to 1100 ° C. so as to surround the single crystal, A heating unit supported by a support member also serving as an electrode; and a heating value adjusting unit configured to adjust a heating value from the heating unit in accordance with a pulling distance of the single crystal body. Things.

[0015]

When manufactured by the above-described process, the portion of the single crystal which seems to be preferably cooled gradually is preferably heated by a heater, and the portion cooled more rapidly is considered to be more suitable for quality. The part which seems to be more preferable will be quenched, and the degree of heating varies depending on the part of the single crystal body,
The thermal history can be made closer to the ideal one, and a single crystal having extremely high quality can be manufactured.

Further, with the above configuration, the calorific value of the heating means can be adjusted by the calorific value adjusting means in accordance with the pulling distance of the single crystal body. By optimizing this adjustment in accordance with the pulling of the single crystal, a very ideal thermal history can be realized.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of an apparatus for producing a single crystal according to the present invention, and FIG. 2 is a detailed view of a heater provided in the apparatus shown in FIG.

The single crystal manufacturing apparatus 1 has a member for melting silicon, a mechanism for pulling up crystallized silicon, and the like. The member for melting silicon is accommodated in a heating chamber 2a. The mechanism for pulling the silicon single crystal is provided inside and outside the pulling chamber 2b which can be separated from the heating chamber 2a by the separating mechanism 20.

A crucible 5 for accommodating molten silicon is provided in the heating chamber 2a. The crucible 5 is supported by a driving device 22 by a rotating shaft 4 so as to be rotatable and vertically movable. The driving device 22 raises the crucible 5 by an amount corresponding to the lowering of the liquid level to compensate for the lowering of the liquid level due to the pulling of the silicon single crystal S, and constantly rotates the crucible 5 at a predetermined rotational speed for stirring the silicon melt. Rotate with. Rotary axis 4
Penetrates through the heating chamber 2a, but is held by a special bearing 23 in order to maintain airtightness inside and outside the chamber and to be used under extremely poor temperature conditions. The crucible 5 comprises a quartz crucible 5a and a graphite crucible 5b for protecting the same as in the prior art.

On the side wall of the crucible 5, a heater 6 for melting silicon is arranged so as to surround the periphery thereof. Outside the heater 6, a heat insulating member 11 for preventing heat from the heater 6 from being directly radiated to the heating chamber 2a is provided so as to surround the periphery thereof. Note that the heater 6 and the heat insulating member 11 are attached to a support 24. The support 24 is manufactured using a material having a very large thermal resistivity.

One end of the wire hoisting machine 10 is attached to the lifting chamber 2b.
A pull-up wire 7 is provided which is hung down through the top wall of the pull-up wire 7, and a chuck 9 for holding a seed crystal 8 is attached to a lower end of the pull-up wire 7. The wire hoist 10 pulls up the silicon single crystal S that gradually grows on the lower end side of the seed crystal 8 in accordance with the growth rate or the like, and at the same time, constantly rotates the crucible 5 in the direction opposite to the rotation direction.

In the chamber 2, a lifting chamber 2b
Argon gas is introduced from the gas inlet port 12 formed in the heating chamber 2a, and flows through the heating chamber 2a evenly and is discharged from the gas outlet port 13. The flow of the argon gas in this manner is to prevent the SiO gas generated in the chamber 2 due to the melting of silicon from being mixed into the silicon melt.

The crucible 5 is placed in the lifting chamber 2b.
A cylinder 25 made of graphite is provided extending toward the solid-liquid interface. The cylinder 25 cuts off radiant heat from the heating chamber 2a and enables rapid cooling of the top portion of the silicon crystal S.

An annular heater 30 functioning as heating means is provided between the lower end of the cylinder 25 and the surface of the silicon melt. The position where this is arranged is that the temperature of the silicon single crystal body S to be pulled is from 900 ° C. to 1100 ° C.
Is optimal. How far away from the silicon melt surface should be placed,
The capacity of the heater is determined as appropriate so that an optimum thermal history can be obtained for the silicon single crystal by each device. The annular heater 30 is attached to the lifting chamber 2b by a support member 31 also serving as an electrode. Electric power is supplied from the heating control device 40 to the annular heater 31. The heating control device 40 is configured so that the supplied electric power can be varied as required. The heating control device 40 functions as a heating value adjusting unit.

FIG. 2 is a diagram showing a specific configuration of the annular heater 30. As shown in the drawing, the annular heater 30 is of an annular type, and heats the outer peripheral surface of the silicon single crystal body S whose interior is pulled up. The annular heater 30 is attached to the pull-up chamber 2b by means such as bolts on a pair of support members also serving as electrodes. The annular heater 30 and the support member 31 are formed using high melting point metal or carbon. The pair of electrodes is drawn out of the pulling chamber 2b, for example, and connected to the heating control device 40.

Next, the operation of the apparatus of the present invention configured as described above and the method of the present invention realized by the apparatus will be described in detail.

First, in manufacturing a silicon single crystal, the pulling chamber 2b is separated from the heating chamber 2a by the separation mechanism 20, and a crude silicon crystal as a raw material and a very small amount of impurities are charged into the crucible 5; The lifting chamber 2b is attached to the heating chamber 2a by the separation mechanism 20. In this state, the annular heater 6 is heated to wait for the silicon in the crucible 5 to be melted. When the silicon is in a molten state, the wire hoist 10 is operated to pull down the wire 7 so that the seed crystal attached to the chuck 9 is in contact with the silicon melt surface. In this state, when the silicon crystal begins to grow on the seed crystal,
Next, the wire hoisting machine 10 is pulled up at a predetermined speed, and FIG.
The silicon crystal S is grown as shown in FIG. With this lifting, the annular heater 30 functioning as a heating unit is operated. This annular heater 30
Is supplied from the heating control device 40, but approximately 7 Kw of power is supplied from the start of pulling up to a predetermined distance, and the annular heater 30 is kept at a relatively high temperature. Thus, the quenched state of the silicon single crystal body S that is being pulled up is changed to a gradually cooled state.

FIG. 3 shows a change state of the power supply to the annular heater 30. As shown in FIG. 3, the power supply to the annular heater 30 is set to be relatively high while the top side of the ingot passes through the inside of the annular heater, and is set to be relatively low at other times. The reason is as follows.

The upper side of the ingot is the upper chamber 2c.
It cools down slowly enough. On the other hand, in a high temperature region of 1100 ° C. or more, many defect nuclei are formed, and oxygen is diffused and coagulated into the defect nuclei during cooling sufficiently slowly in the upper chamber 2c, and many oxygen precipitate nuclei are formed. It is formed. Therefore, the amount of precipitated oxygen increases. However, 1
In the range of 100 ° C. to 900 ° C., a phenomenon occurs in which the defect nuclei formed in the high temperature range of 1100 ° C. or more disappear.
Therefore, when a portion corresponding to this temperature is heated by the annular heater 30, the defect nuclei disappear and the amount of precipitated oxygen does not increase even if the portion is cooled slowly in the upper chamber 2c.

Further, in the cylinder 25, the gas inlet 12
Is flowing downward, so that
Temperature ranges other than 0 ° C. to 900 ° C. are rapidly cooled. Therefore, the diffusion and aggregation of oxygen and the formation of oxygen precipitation nuclei can be more completely suppressed, and as a result, the effect of eliminating the factor that reduces the yield in the integrated circuit manufacturing process can be eliminated.

On the other hand, the bottom side of the ingot is immediately wound up in the upper chamber 2c after the formation of the crystal tail, so that it is rapidly cooled. Therefore, diffusion aggregation of oxygen and oxygen precipitation nuclei are hardly formed, and the amount of precipitated oxygen tends to be reduced. Therefore, from 1100 ° C to 90
The degree to which the temperature is gradually cooled in the range of 0 ° C. should be warmed as compared to the top side of the ingot. Therefore, the power supplied to the annular heater 30 is set lower. The effect of quenching a temperature other than 1100 ° C. to 900 ° C. is described in the same manner as the ingot top side.

As described above, according to the present invention, the portion to be heated and the portion to be cooled can be clearly distinguished, and the heating and cooling portions matched to each portion such as the top side and the bottom side of the ingot. Since control is possible, it becomes possible to efficiently produce a high-quality silicon single crystal in which the amount of precipitated oxygen is strictly controlled, which was impossible with the prior art.

In order to confirm this, an experiment was conducted to compare the amount of precipitated oxygen, the OSF, and the oxide film breakdown voltage of the single crystal manufactured based on the apparatus and method of this embodiment with those of the conventional technique.

In this experiment, the annular heater 30
Was placed at about 200 to 300 mm from the silicon melt surface, and the single crystal was gradually cooled at around 900 ° C.
The single crystal to be compared was manufactured using the apparatus shown in FIG.

The OSF was evaluated by the area density of etch pits after heat treatment for 60 minutes in a wet oxygen atmosphere at 1100 ° C. With respect to the oxide film breakdown voltage, a polysilicon MOS diode was formed on a wafer, the dielectric breakdown characteristics of the oxide film when a voltage was applied thereto was examined, and the average breakdown voltage was used as the oxide film breakdown voltage.

[0036]

[Table 1]

As can be seen from the above results, when the method of the present invention is carried out using the apparatus of the present invention, all parts of the single crystal are as shown in the above table and also as shown in FIG. In addition, a uniform amount of precipitated oxygen is exhibited. Also, the withstand voltage of the oxide film can be improved.

In this embodiment, the cylinder 25 is exemplified. However, the cylinder 25 is not particularly provided if the purpose of producing a single crystal having a uniform oxygen deposition amount can be achieved. Good. This is because if the slow cooling state by the annular heater 30 is reliably realized, the amount of precipitated oxygen can be made uniform.

[0039]

As described above, according to the present invention, when pulling up the single crystal, the portion requiring slow cooling is heated at an arbitrary temperature by the heating means. The pressure resistance can be improved, and the amount of precipitated oxygen can be made uniform regardless of the location of the ingot.

Further, since the calorific value of the heating means can be arbitrarily adjusted by the calorific value control means, the heat history of the single crystal can be positively adjusted.

In addition, the use of the present invention makes it possible to produce a single crystal having a uniform quality regardless of the length thereof. Is very effective.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an apparatus for producing a single crystal according to the present invention.

FIG. 2 is a detailed view of the annular heater shown in FIG.

FIG. 3 is a diagram provided for describing an effect of the present invention.

FIG. 4 is a schematic configuration diagram of a conventional single crystal manufacturing apparatus.

FIG. 5 is a schematic configuration diagram of a conventional single crystal manufacturing apparatus.

FIG. 6 is a diagram showing the amount of oxygen precipitated in a single crystal produced by a conventional apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Single crystal manufacturing apparatus 2 ... Chamber 2a ... Heating chamber 2b ... Pulling chamber 2c ... Upper chamber 5 ... Crucible 6 ... Annular heater 7 ... Pulling wire 8 ... Seed crystal 30 ... Annular heater (heating means) 31 ... Supporting member 40: heating control device (heating value adjusting means) S: silicon single crystal (single crystal)

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Toshio Iwasaki 3434 Shimada, Hikari-shi, Yamaguchi Prefecture Inside Nippon Steel Corporation Hikari Works (56) References JP-A-4-16589 (JP, A) 60-86092 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C30B 1/00-35/00

Claims (3)

(57) [Claims] 1. A method for producing a single crystal in which a seed crystal is brought into contact with a melt to be melted in a crucible and a single crystal is grown by gradually pulling up the seed crystal. The ring-shaped heater is supported by a support member also serving as an electrode, and is located near the outer peripheral surface of a portion exhibiting 900 ° C. to 1100 ° C. of the single crystal body separated from the solid-liquid interface of the melt by a predetermined distance and pulled up. A method of manufacturing the single crystal body, wherein the single crystal body is disposed at a position so as to surround the single crystal body, and a predetermined power is supplied to the heater to gradually cool the outer peripheral surface of the single crystal body to be pulled up. . 2. A method for producing a single crystal in which a seed crystal is brought into contact with a melt to be melted in a crucible and a single crystal is grown by gradually pulling the seed crystal. An annular heater is supported by a support member that also serves as an electrode, and surrounds the single crystal at a position away from the solid-liquid interface of the melt by a predetermined distance and near the outer peripheral surface of the single crystal pulled up. Until the single crystal body is pulled up a predetermined distance, a predetermined power is supplied to the heater to gradually cool the outer peripheral surface of the single crystal body that is pulled up, and thereafter, the power supply to the heater is reduced. A method for producing a single crystal, characterized by promoting cooling of the outer peripheral surface of the single crystal in a reduced amount. 3. A single crystal manufacturing apparatus for pulling up and growing a single crystal from a melt melted in a crucible, wherein the single crystal is separated from a solid-liquid interface of the melt by a predetermined distance from 900 ° C. of the single crystal pulled up. A heating unit that is disposed at a position near the outer peripheral surface of a portion exhibiting 1100 ° C. and surrounds the single crystal body and is supported by a support member also serving as an electrode; An apparatus for producing a single crystal, comprising: a heating value adjusting means configured to be adjustable according to a pulling distance of the single crystal.