JPH02279582A - Apparatus and method for producing semiconductor single crystal - Google Patents

Abstract

PURPOSE:To continuously produce a single crystal which is approximately uniform in impurity concn. in the longitudinal direction with the subject apparatus of a continuous charge system by specifically providing a raw material-supplying mechanism consisting of a protective cylinder and a resistance heater, etc. CONSTITUTION:A raw material-supplying mechanism 200 consists of a resistance heater 11, an insulating pipe 18, a heat insulating cylinder 10, the protective cylinder 9, a holding pipe 150, and a raw material rod feeder. The heater 11 is held in the heat insulating cylinder 10 held in the protective cylinder 9 via the insulating pipe 18 in order to suppress the thermal influence of a grown single crystal 6. Further, the protective cylinder 9 is hermetically fixed to the holding pipe 150 provided in the apparatus 180 for producing the single crystal at the top end thereof and the front end part thereof is located in the raw material melt packing region in a quartz crucible 4. The front end of the protective cylinder 9 is positioned in a melt 100 and a vapor phase part 101 in a pulling-up device is isolated from a vapor phase part 102 in the protective cylinder 9 at the time of the growth of the single crystal 6. Even if a liquid drop is dropped by the melting of the raw material rod 13 fed into the heater 11 which is higher in the temp. toward the lower part, the nonuniformity of the temp. generated in the melt 100, the oscillation of the liquid surface and further, the arrival of the falling foreign matter at the single crystal 6 are suppressed.

Description

[Detailed description of the invention] C industrial application field] The present invention continuously supplies raw materials into a crucible.

This invention relates to technology for continuously manufacturing homogeneous semiconductor single crystals.

[Prior Art] A CZ method is used to grow a semiconductor single crystal, in which a cylindrical crystal is grown from a raw material melt in a crucible. In this technique, an impurity element called a dopant is added to the raw material melt in a crucible in order to control the resistivity of the single crystal being grown. However, dopants generally have a segregation coefficient of 1.
Therefore, in the normal CZ method, the concentration in the crystal changes as the length of the crystal increases. This poses a problem in the production of semiconductor single crystals whose resistivity is controlled by dopant concentration.

To solve this problem, a technology using a continuous charging method and a double crucible in which 1M material is continuously supplied into the crucible and the dopant concentration in the raw material melt is kept constant (Japanese Patent Laid-Open No. 63-7
9790) has been proposed. As a raw material supply means in the continuous charging method, the raw material melting place and the single crystal growing place are separated and transported (Japanese Patent Application Laid-Open No. 52-58080,
JP-A-56-16409'7), those using rod-shaped raw materials (JP-A-56-84397, JP-A-62-1059)
92) and other proposals.

[Of the continuous charging technologies mentioned above, the first two are:
It requires a crucible for melting raw materials and a crucible for crystal growth, making it structurally complex, and it is difficult to control the supply amount. In the latter two, in order to melt the rod-shaped raw material with the melt in the crucible, it is necessary to increase the temperature gradient between the crystal growth location and the raw material melting location in the crucible, and the raw material melts during crystal growth. Furthermore, the latter of the latter requires a high amount of waste when preheating the raw material, but for example, in a reduced pressure furnace used for growing single crystal silicon, there is a high risk of electrical discharge, making it impractical. Further, in the case of a double crucible, polycrystals are likely to be generated from the inner wall, and the growth rate is inevitably reduced. Moreover.

There is also an intermediate layer where the amount of impurities mixed in from the crucible material increases.

[Means for Solving the Problems] The present invention solves the problems of conventional continuous charging technology,
This makes it possible to continuously produce a single crystal with almost uniform impurity concentration along its length. A resistance heater is provided above the tip, and the temperature of the resistance heater can be set so that the lower part can melt the raw material at a higher temperature.When pulling a single crystal, the tip of the protective cylinder is positioned in the melt. The gas phase part in the protective cylinder and the gas phase part in the pulling device are separated by the melt, and the crystal rods are melted at the lower part of the protective cylinder by a resistance heater and supplied to the surface of the melt in the crucible. In addition, when pulling a single crystal, the single crystal is continuously pulled while a new raw material is melted and supplied from a raw material supply mechanism configured such that the gas phase part is independent from the gas phase part in the apparatus. It is characterized by being carried out in a specific manner.

In the present invention, if the raw material supply mechanism is equipped with a raw material rod feeding mechanism that controls the feed of the raw material rod according to the amount of decrease in the melt in the crucible due to the growth of the single crystal, stable continuous growth of single crystals is possible. Become.

Also, if the resistance heater is made into a cylindrical spiral shape.

The melted part of the raw material can be brought closer to the melt surface.

Furthermore, if the diameter of the protective tube and the resistance heater is reduced downward, the amount of raw material supplied can be easily controlled.

In addition, 50cc/11711.・cm
By flowing an inert gas of 3 or more, it is possible to prevent the retention of silicon monoxide and extend the life of the heater.

In the present invention, in order to prevent electrical discharge, a configuration is adopted in which a rod-shaped raw material is melted directly above the melt surface using a resistance heater. The raw material rod used has a dopant concentration equal to that of the grown single crystal. The feeding speed or feeding weight is adjusted based on, for example, the pulling speed of the single crystal or the weight of the single crystal, and is further controlled, if necessary, by adjusting the amount of electric power to the resistance heater. In this way, only the amount corresponding to the pulled up amount is newly supplied to the melt in the crucible.Furthermore, in order to prevent vibrations caused by falling of the feed material melt and adhesion of fallen foreign matter to the growing single crystal, a A protective tube made of cylindrical quartz covered the entire surface of the resistance heater, and its tip was immersed in the raw material melt to isolate the gas phase within the raw material supply mechanism and the gas phase within the pulling device from each other.

Further, if the resistance heater is configured in a cylindrical spiral shape, it becomes compact.

Furthermore, if the protective cylinder is provided with a gas supply pipe and an exhaust pipe to the outside of the system, it becomes possible to supply an inert gas into the protective cylinder.

In the present invention, even if the melt in the crucible starts to decrease at the same time as the pulling starts, the feeding speed of the raw material rod is adjusted to match this decrease, and the electric power to the resistance heater is Controlled melting of raw material rods.

The resistance heater, which continuously supplies raw materials, is constructed so that the lower part is at a high temperature, so that the raw material rod melts only at the lower part. Furthermore, since the tip of the protective cylinder is maintained in the melt in the crucible, the molten raw material falls onto the surface of the melt in the protective cylinder. Even if a foreign object falls, it will remain inside this protective cylinder.

The present invention will be explained in more detail below using the drawings which are one embodiment thereof.

1 shows a single crystal manufacturing apparatus u according to one embodiment of the present invention, FIG. 3 shows a single crystal manufacturing apparatus according to another embodiment of the present invention, and FIG. 4 shows an embodiment of the single crystal manufacturing apparatus u according to the present invention. An example resistance heating heater section is shown.

In the embodiment of the present invention, the raw material supply mechanism 200 is.

It consists of a resistance heater 11, an insulating tube 18, a heat retaining tube 10, a protection tube 9, a holding tube 150, and a raw material rod feeder 20 (see FIG. 3).

As shown in FIG. 4, the resistance heater 11 is held in a heat insulating tube 10 via an insulating tube 18 in order to suppress the thermal influence on the grown single crystal as much as possible. It is stored inside. Therefore, the resistance heater 11. The insulating tube 18 and the heat retaining tube 10 are held within the protective tube 9. Furthermore, as shown in FIG. 1, the protective tube 9 is airtightly fixed at one upper end to a holding tube +50 provided in the single crystal manufacturing apparatus 180, and the tip is located in the raw material melt filling area of the crucible. are doing. Therefore, during single crystal growth, the tip of the protection tube 9 is always in the melt 100, and the gas phase section 102 in the raw material supply mechanism and the gas phase section 101 in the single crystal manufacturing apparatus become independent of each other. . Also,
By locating the tip of the protective cylinder in the melt 100 in this way, even if droplets fall due to the melting of the raw material rod 13, unevenness in the degree of droplets occurring in the crucible melt 100 and the liquid level can be prevented. This suppresses vibration and also prevents this liquid level vibration and furthermore, falling foreign matter from reaching the grown single crystal 6.

As shown in FIG. 4, the resistance heater 11 has a cylindrical shape separated into left and right parts, a heating part 170 having a double helical structure, and an electrode 160 at each upper end. Raw material rod 1
3 is fed into the resistance heater 11 in conjunction with the weight of the grown single crystal 6 to keep the amount of the raw material melt 100 constant, becomes molten at the lower part of the heating section +70, and the raw material melt 10
Supplied during 0.

In addition, if the raw material supply mechanism is removed from the single crystal pulling area and installed in two locations as shown in Figure 1, when one raw material rod is exhausted, the other raw material rod loaded in advance can be used. During this time, the gate valve 17 can be closed and the exhausted raw material rod can be replaced with a new raw material rod. By repeating this process, semiconductor single crystals can be grown continuously.

In addition, A A in FIG. 1, FIG. 2, and FIG. 3 is shown in FIG.
A cross-sectional view along the line is shown.

[Example 1] Silicon was produced using the single crystal manufacturing apparatus shown in FIG. 1, which shows an example of the present invention. 11 crystals were grown. The conditions for single crystal growth are as follows: quartz crucible 4 has a diameter of 16 inches, the amount of melt in the quartz crucible is 15 kg, the diameter of the raw material rod 13 is 50 mm, the diameter of the grown single crystal 6 is 4 inches, and the resistivity (phosphorus dope) is 10.
Ω'cm, pulling speed 1mm/ff1in.

It is. There is a relationship between the feeding speed of the raw material rod and the electric power of the resistance heater as shown in FIG. 6. In this example,
The feed rate of the raw material rod 13 was 4 ml/akin, and the electric cuff of the resistance heater 11 was set to -.

FIG. 7 shows the resistivity change in the axial direction of the grown single crystal.

For reference, we also show the results of the conventional CZ method when the amount of melt in the crucible is the same.8 In the conventional CZ method, the resistivity changes greatly with growth, but using the present invention It is almost constant in the grown single crystal. Figure 8 shows the change in oxygen concentration in the axial direction.The growth conditions are the same.The single crystal grown using the present invention is uniform in the axial direction,
Moreover, the oxygen concentration is lower than that of the ordinary CZ method.

Compared to the double crucible method, it is 172 or less. This makes it possible to widen the control range of oxygen concentration.

It is clear that the present invention can be applied in various ways, such as the growth of single crystals other than silicon, the application of a magnetic field, and the use of granular raw materials.

[Embodiment 2] Next, a different embodiment of the present invention shown in FIG. 2 will be described.

In the description of the second embodiment, the same components as those in the first embodiment of the present invention are denoted by the same reference numerals, and redundant explanation will be omitted.

The main points in the embodiment shown in FIG. 2 that differ from Example 1 of the present invention described in OjI are the air supply device (not shown) into the raw material supply mechanism and the connection between the melt 100 and the tip of the resistance heater II. An exhaust pipe 300 to the outside of the device system is provided on the side wall of the protective tube 9. As a result, the gas phase section 10 in the raw material supply mechanism
For example, an inert gas can be supplied to 2.

Using the apparatus shown in FIG. 2, a silicon single crystal was grown under the same conditions as in Example 1 while flowing argon gas at 50 cc/min into the raw material supply mechanism 200 and exhausting the air from the exhaust pipe 300. I did it.

The characteristics of the grown single crystal were similar to those in Example 1, but the resistance heater, especially at its lower end, had the same characteristics as those in Example 1.
The formation of silicon carbide, which occurred in the previous example, was not observed, and it was confirmed that this method is effective in preventing the deterioration of resistance heaters. This is thought to be because the silicon oxide and silicon oxide rising from the melt surface are carried away from the apparatus system before they come into contact with the resistance heater due to the flow of argon gas.

[Advantageous Effects] In the present invention, since a resistance heater is used as the heater for melting the raw material rod, the occurrence of electric discharge in the single crystal manufacturing equipment is prevented. The shape can be made compact and it can be melted directly into the raw material melt.

In addition, in order to completely isolate the gas phase inside the single crystal manufacturing equipment and the gas phase inside the raw material supply mechanism, we have adopted a protective tube that covers the entire surface of the resistance heater and whose tip is located in the melt. It is possible to prevent fallen foreign matter from reaching the crystal growth section, and it is also possible to suppress vibrations on the melt surface due to raw material supply.

Furthermore, the vibration itself remains within the protective cylinder and does not propagate to the entire surface of the melt. Furthermore, compared to the method using a double crucible, the number of impurities introduced from the crucible material can be reduced and high-speed growth can be achieved. In such an apparatus having a conventional JM material supply mechanism, the gas phase within the single crystal Δ apparatus body and the gas phase within the raw material supply mechanism are not isolated from each other, so that SiO, etc. generated within the raw material supply mechanism is However, according to the present invention, there is no such pressure that the material falls onto the melt surface due to the internal pressure of the raw material supply mechanism and inhibits single crystallization.

By providing an exhaust pipe in the protective cylinder between the lower part of the resistance heater and the melt surface and flowing inert gas into the raw material supply mechanism, -
It is possible to prevent silicon oxide from remaining and reduce the amount of silicon carbide that adheres to the resistance heater. This has the effect of preventing deterioration of the resistance heater. Note that the flow rate of the inert gas in this case is preferably 50 cc/min, .multidot.1 or more.

In addition, by making the resistance heater into a cylindrical double helix shape, it can be made extremely compact and efficient, and the temperature at the cutting edge of the heater can be set to the highest temperature.
Thereby, the melted part of the raw material can be brought closer to the melt surface.

Furthermore, if the diameter of the protective tube and the resistance heater is reduced downward, the control of the raw material feeder becomes easier.

Since the protective tube is provided inside the pulling device outside the single crystal growth area, it does not interfere with pulling.

As a result of the above-mentioned effects, the present invention makes it possible to supply raw materials, which is the biggest problem in continuous charging type semiconductor single crystal manufacturing equipment, without adversely affecting the single crystal being grown. As a result, the dopant concentration in the raw material melt in the crucible can be controlled, and the resistivity in the axial direction of the single crystal becomes constant.

This greatly improves the product yield of manufactured semiconductor single crystals.

In the apparatus of the present invention, quartz or carbon is preferable as the material for the protective tube, and it is particularly preferable to use high-purity quartz for the tip portion that comes into contact with the melt. Further, the resistance heater may be made of a material that is used for ordinary carbon heaters. Moreover, carbon, silicon carbide, etc. can be used for the heat retaining cylinder.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a single crystal manufacturing apparatus showing an embodiment of the present invention. FIG. 2 is a longitudinal sectional view of a single crystal manufacturing apparatus showing another embodiment of the present invention. FIG. 3 is a longitudinal sectional view of a single crystal manufacturing apparatus showing still another embodiment of the present invention. Fig. 4 is a vertical cross-sectional view of the resistance heater; Fig. 5 is a longitudinal cross-sectional view of the resistance heater;
FIG. 3 is a cross-sectional view taken along line 8-A in FIGS. 2 and 3. FIG. 6 is a diagram showing the relationship between raw material feed rate, melting power, and raw material diameter. FIG. 7 is a diagram showing the relationship between the dose and resistivity of a grown single crystal according to an embodiment of the present invention. FIG. 8 shows the small crystals grown according to an embodiment of the present invention.
A diagram showing the relationship between Mr. and acid g f4 degree. Heater 11... Resistance heating heater 3 Graphite Ruppo I3 - Raw material rod internal gas phase section - I IJ crucible 14 - Seed crystal 6-, (γ Seiichisha crystal 17... Gate valve 8 Cover
18...Insulating tube 5] Protective tube 19...Bedistal 10--Heating tube 20... Raw material melt to feed the raw material gas phase part inside the single crystal manufacturing device Raw material feeder single crystal manufacturing device JJu etc. [Pipe No. 3 Figure Patent applicant: Komatsu Electronic Metals Co., Ltd. Quartz crucible Figure 5 A-A sectional view Figure 6 Raw material rod feeding speed. (mm/min,) Fig. 7 Weight of grown single crystal. (K9) Figure 8 Growth single crystal weight (kg)

Claims (1)

[Claims] 1. A crucible filled with raw materials, a heater located around the crucible to melt the raw materials in the crucible, and a seed crystal immersed in the molten raw materials in the crucible to pull a single crystal. In a semiconductor single crystal manufacturing apparatus having a pulling mechanism, a protective tube having a tip opening in the raw material melt filling area of the crucible and communicating with the inside of the pulling device only at this tip; A raw material supply mechanism is installed in the device outside the single crystal pulling area, and consists of a resistance heater that is provided in the protective cylinder and whose temperature is maintained at a higher temperature in the lower part, and which is controlled to maintain the temperature so that the lower part can melt the semiconductor raw material. However, when pulling a single crystal, the tip of the protective cylinder is immersed in the raw material melt, so that the gas phase part in the pulling device and the gas phase part in the protective cylinder are made independent of each other. A semiconductor single crystal manufacturing device characterized by: 2. The semiconductor single crystal manufacturing apparatus according to claim 1, wherein the raw material supply mechanism includes a raw material rod feeder whose feed rate is controlled according to the amount of decrease in the raw material melt in the crucible. 3. The semiconductor single crystal manufacturing apparatus according to claim 1 or 2, wherein the resistance heater has a cylindrical shape with a spiral structure. 4. The semiconductor single crystal manufacturing apparatus according to any one of claims 1 to 3, wherein the protective tube and the resistance heater have diameters that are reduced downward. 5. In a semiconductor single crystal manufacturing method in which a single crystal is grown by dipping a seed crystal into the surface of a raw material melt filled in a crucible and gradually pulling it up, the gas phase of the single crystal is exposed to the air inside the equipment when the single crystal is pulled up. A method for manufacturing a semiconductor single crystal, characterized in that the single crystal is continuously pulled while supplying a new raw material to the phase part from a raw material supply mechanism having an independent configuration. 6. In the raw material supply mechanism, 50cc/min.・cm＾3
6. The method for manufacturing a semiconductor single crystal according to claim 5, further comprising flowing the above inert gas.