JP2816633B2 - Single crystal pulling apparatus and pulling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a single crystal pulling apparatus and a pulling method.

[0002]

2. Description of the Related Art High-purity silicon is mainly used as a base of a semiconductor integrated circuit device. One method of producing this high-purity silicon is to pull a columnar single crystal from a raw material melt in a crucible. Czochralski method (hereinafter C
Z method) is used. In the CZ method, a crucible is filled with a raw material polycrystal, the raw material is heated and melted by a heater surrounding the outer periphery of the crucible, and then a seed crystal attached to a seed chuck is immersed in a melt. The seed chuck is pulled up while rotating in one direction or the other direction to grow a single crystal.

In recent years, the diameter of semiconductor wafers has increased, and large-diameter wafers having a diameter of more than 6 inches have been required, and single crystals having a diameter of 6 inches or more are becoming mainstream. For this reason, the size of the single crystal manufacturing apparatus is increased, and the processing amount per cycle tends to increase. However, the required time in the single crystal growth step is increased with the increase in the size of the single crystal manufacturing apparatus, and before and after the step, for example, the time required for dissolving the raw material polycrystal, and after the grown single crystal is taken out of the furnace, The time required for cooling until the temperature of the crucible, the heater and the like can be reduced is also longer than before. These are factors that reduce the productivity of the single crystal.
In addition, since the quartz crucible is deformed, cracked, etc. due to a thermal load applied when the raw material polycrystal is melted, it is replaced with a new one each time a single crystal is pulled.

[0004]

As a means for solving the problem of a decrease in the productivity of a single crystal, there is a conventionally known method of recharging. This is a method in which after the single crystal is pulled out of the melt, the process of charging and melting the raw material polycrystal again without turning off the heater power and growing the single crystal again is repeated several times. This recharging method can save several batches of time for cooling in-furnace components, time for cleaning the chamber, and the like. In addition, the number of quartz crucibles that normally require one for each pulling of one single crystal is one for several single crystals, and the manufacturing cost is reduced. However, when a raw material polycrystal, for example, a rod-shaped polycrystal is directly immersed and melted in a melt remaining in the quartz crucible, a large heat load is applied to the quartz crucible and the surface thereof is eroded. In addition, the bubbles in the quartz expand to deform the quartz crucible, and in severe cases, there is a problem that the bubbles are ruptured and fragments of the quartz crucible are mixed into the melt to inhibit single crystallization. . The present invention has been made in view of the above-mentioned conventional problems, and can reduce a single crystal production time, and a single crystal pulling apparatus capable of pulling a single crystal several times with one quartz crucible and It aims to provide a method of raising.

[0005]

In order to achieve the above object, a single crystal pulling apparatus according to the present invention is a single crystal pulling apparatus using the Czochralski method, wherein an upper heater surrounding a single crystal pulled above a melt surface is provided. The crystal pulling method using this single crystal pulling apparatus is to melt the raw material polycrystal using the upper heater, or heat the raw material polycrystal using the upper heater,
The raw material polycrystal may be dissolved by using a main heater surrounding the crucible. Further, after a certain amount of the raw material polycrystal is melted, the additional raw material polycrystal may be melted using the upper heater or the upper heater and the main heater.

[0006]

According to the above structure, in the single crystal pulling apparatus using the Czochralski method, since the upper heater surrounding the single crystal pulled above the melt surface is provided, the main heater surrounding the crucible is provided by using the upper heater. The raw material polycrystal can be dissolved without increasing the power of the heater. Further, during heating by the upper heater, the power of the main heater can be reduced to reduce the heat load on the quartz crucible. Therefore, after the first single crystal pulling, the rod-shaped or granular raw polycrystal supported by the wire cable of the crystal pulling mechanism is melted by the upper heater, or the raw polycrystal heated by the upper heater is melted by the main heater. For example, the thermal load applied to the quartz crucible from the main heater can be minimized, and the service life of the quartz crucible can be extended to several times. Further, when the granular polycrystal filled in the quartz crucible is melted, the melt surface is below the upper end of the crucible, so after completion of the melting, the additional material polycrystal is added using the upper heater or the upper heater and the main heater. By dissolving the single crystal, it is possible to increase the amount of charge at one time, and a single crystal longer than a conventional one can be pulled, which contributes to an improvement in the yield and productivity of the single crystal.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a single crystal pulling apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a partial cross-sectional view schematically showing a schematic configuration of a lower portion of a single crystal pulling apparatus, showing a state during single crystal pulling. In the figure, a quartz crucible 3 is fitted to a graphite crucible 2 installed in a main chamber 1, and a silicon single crystal 5 is pulled up from a melt 4 stored in the quartz crucible 3.
6 is a crucible shaft, 7 is a main heater, 8 is a heat insulating cylinder, and a radiation screen 9 is attached to the upper end of the heat insulating cylinder 8. The radiation screen 9 is a heat shield surrounding the single crystal pulling region, and is a conical tube whose lower end opening has a diameter equal to or less than the upper end opening. Also, the upper heater 10
Is a cylindrical graphite heater surrounding the silicon single crystal 5 and is supported by a bracket 11 provided at the upper end of the heat insulating cylinder 8. As shown in FIG. 2, the upper heater 10 includes a cylindrical graphite heater main body 10a and a cylindrical graphite heat insulation cylinder 10b surrounding the heater main body 10a. The heat insulation cylinder 10b is a cylindrical heat insulating material made of carbon fiber. 10c is graphite surface layer 1
0d. By changing the axial length, size, etc. of the upper heater 10, heating of the raw material polycrystal,
The time required for dissolution can be reduced. In the present embodiment, the upper heater 10 is supported by the heat insulating cylinder 8 via the bracket 11, but is not limited to this, and may be supported or fixed to the inner wall of the chamber or the radiation screen 9.
Needless to say, the present invention is also applicable to a single crystal pulling apparatus without a radiation screen.

Next, a single crystal pulling method using the single crystal pulling apparatus will be described. When pulling the single crystal shown in FIG. 1, the upper heater 10 is not operated, and only the main heater 7 is operated. When the pulling of the first single crystal is completed, this single crystal ingot is taken out of a pull chamber (not shown). Next, as shown in FIG. 3, the rod-shaped polycrystalline silicon 13 supported by the wire cable 12 of the crystal pulling mechanism is suspended in the upper heater 10,
The upper heater 10 is operated. The heated and dissolved polycrystal is dropped onto the melt 4 remaining in the quartz crucible 3. Melt 4
When a predetermined amount is reached, the operation of the upper heater 10 is stopped, the wire cable 12 is wound up, and the polysilicon 1
The rest of 3 is taken out of the pull chamber. afterwards,
A seed crystal is supported on the wire cable 12 of the crystal pulling mechanism, the seed crystal is immersed in the melt 4, and a single crystal is pulled as shown in FIG. As described above, since the raw material polycrystal is melted and supplied by the upper heater 10, the heat load applied to the quartz crucible 3 from the main heater 7 is reduced, and the single crystal is pulled multiple times without replacing the quartz crucible. It can be performed. The polycrystalline silicon 13
May be immersed in the melt 4 while being heated by the upper heater 10 and dissolved by the main heater 7. In this case, since the polycrystalline silicon 13 is sufficiently heated, it can be easily dissolved in the melt without increasing the power of the main heater 7.

FIG. 4 is an explanatory view of the second embodiment, in which granular polycrystalline silicon is used in place of the rod-shaped polycrystalline silicon. A granular polycrystalline silicon 14 is filled in a quartz container 15 made of quartz or quartz provided on the inside, and this is suspended by the wire cable 12 of the crystal pulling mechanism and suspended in the upper heater 10. To dissolve. The polycrystalline silicon 14 is supplied to the upper heater 10
Alternatively, a method may be used in which the main heater 7 drops the melt 4 while heating it, and then melts it with the main heater 7.

FIG. 5 is an explanatory diagram of the third embodiment. The granular polycrystalline silicon 14 is dropped on the melt remaining in the quartz crucible 3 as it is, and the main heater 7 and the upper heater 10 are dropped.
And are simultaneously operated to dissolve. This method may be used for the first melting of the raw material, that is, for melting the granular polycrystalline silicon filled in the quartz crucible 3. Since it is not necessary to increase the power of the main heater 7 by operating the upper heater 10, it is possible to melt the raw material while minimizing the heat load applied to the quartz crucible.

When the melting of the granular raw material polycrystal filled in the quartz crucible is completed, the melt surface is located at a position lower than the upper end of the quartz crucible, and the capacity of the quartz crucible is allowed. According to a fourth aspect of the present invention, the amount of charge is increased by utilizing this phenomenon. After the completion of the dissolution, the raw material polycrystal is additionally dissolved. The raw material polycrystal to be added has a rod shape or a granular shape as described above, and is melted only by the upper heater or by the upper heater and the main heater. According to this method, it is possible to increase the amount of charge at one time to about 1.5 times the conventional amount.

[0012]

As described above, according to the present invention, the upper heater is provided above the surface of the melt to surround the single crystal, and the upper heater mainly comprises the polycrystalline material filled in the crucible and the polycrystalline material to be recharged. , Or after sufficiently heating with the upper heater and then melting with the main heater, the time required for melting the raw material polycrystal can be greatly reduced. Due to this effect and the effect of the recharge method, the time required for manufacturing a single crystal per crystal can be reduced to about one third of the conventional one. Further, by utilizing the upper heater, the thermal load applied to the quartz crucible can be minimized and the deterioration can be delayed, so that the single crystal can be pulled several times without replacing the quartz crucible. In addition, the upper heater can be used to change the thermal history of a single crystal that has already been grown, or the single crystal with different resistance values can be pulled up in the same quartz crucible by changing the doping material of the source polycrystal to be recharged. it can.

[Brief description of the drawings]

FIG. 1 is a partial sectional view schematically showing a schematic configuration of a lower portion of a single crystal pulling apparatus.

FIG. 2 is a plan view of an upper heater.

FIG. 3 is an explanatory diagram showing a state in which a rod-shaped polycrystal is melted by an upper heater.

FIG. 4 is an explanatory view showing a state in which a granular polycrystal is melted by an upper heater.

FIG. 5 is an explanatory diagram showing a state in which a granular polycrystal is melted using an upper heater and a main heater.

[Explanation of symbols]

2 graphite crucible 13,14 polycrystalline silicon 3 quartz crucible 4 melt 5 silicon single crystal 7 main heater 10 upper heater

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Sho 59-189875 (JP, U) Japanese Utility Model Sho 61-183971 (JP, U) Japanese Utility Model Hei 1-122068 (JP, U) (58) Field (Int.Cl. ⁶ , DB name) C30B 15/14-15/18 C30B 15/02-15/04

Claims (4)

(57) [Claims] 1. A single crystal pulling apparatus using a Czochralski method, wherein an upper heater surrounding the single crystal pulled above a melt surface is provided. 2. A single crystal pulling method using a single crystal pulling apparatus according to claim 1, wherein the raw material polycrystal is melted using an upper heater. 3. A single crystal pulling apparatus using the single crystal pulling apparatus according to claim 1, wherein the raw material polycrystal is heated using an upper heater, and the raw material polycrystal is melted using a main heater surrounding a crucible. Method. 4. The single crystal pulling apparatus according to claim 1, wherein after a certain amount of the raw material polycrystal is melted, the additional raw material polycrystal is melted by using the upper heater or the upper heater and the main heater. Single crystal pulling method used.