JPH0333093A - Method and device for growing single crystal - Google Patents

Abstract

PURPOSE:To reduce generation of crystal defect by heating the seed side part of single crystal being pulled up and uniforming the temp. distribution of the seed side part and cooling single crystal while uniforming the temp. distribution of the whole body after drawing-up of single crystal has been completed. CONSTITUTION:Seed crystal 1 is fitted to the lower end of a drawing-up device 9 which can be vertically moved while being rotated to the direction shown by an arrow in a growth chamber 15. A radiation heat shielding plate 16 is opened which is provided to the aperture of the boundary of both a furnace chamber 8 and the growth chamber 15 and freely opened in the directions shown by the arrows. The drawing-up device 9 is lowered and seed crystal 1 is brought into contact with melt 3 in a crucible 30. Thereafter, while the drawing-up device 9 is rotated, seed crystal 1 is slowly drawn up to grow single crystal 2. Single crystal 2 is uniformly heated at 110 deg.C or more by a second heat source 11 provided in the growth chamber 15. Single crystal 2 having prescribed length is drawn up and the whole single crystal is drawn up into the growth chamber 15. Thereafter radiation heat emitted from melt 3 is interrupted by the radiation heat shielding plate 16 and the temp. of single crystal 2 is uniformed. Then the whole single crystal 2 is uniformly cooled by a cooling cylinder 17 and adjustment of electric energy of the heat source 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application J] The present invention relates to a method for growing a single crystal of silicon or the like by the Czochralski method and an apparatus therefor.

[Conventional technology J The following will explain the growth of a silicon single crystal as an example.

Growing single crystals using the Czochralski method has the advantage of being easy to obtain large-diameter single crystals, so it is used in the production of silicon single crystals for semiconductor integrated circuits, and its crystallinity is extremely close to perfect. Due to repeated heat treatments in the circuit element manufacturing process, oxygen contained in silicon may precipitate and crystal defects may occur.

In order to solve the above drawbacks, for example, Japanese Patent Laid-Open No. 57-183
In Publication No. 393, as shown in FIG. 2, a second heat source 11 is provided in the growth chamber 15, and the single crystal 2 being pulled is
By keeping the temperature at 150°C, the temperature difference between the seed side and the bottom side of the single crystal is reduced, and by reducing the difference in thermal history between the two, it is possible to create a device that produces high-quality, homogeneous fluorophore crystals.
However, with this equipment, it was not possible to control the temperature when cooling the single crystal, resulting in differences in thermal history during the cooling process, and the problem was that there were areas where crystal defects were likely to occur due to heat treatment in the element manufacturing process. .

On the other hand, as shown in FIG. 3 in Japanese Patent Application Laid-Open No. 60-191095, it is believed that nucleation of oxidized precipitates occurs by rapidly cooling the single crystal 2 through a cooling tube 17 while pulling it. A method has been proposed to reduce the occurrence of crystal defects due to heat treatment in the element manufacturing process by passing through the temperature range quickly. However, with this method, there is a problem that a large temperature gradient exists within the single crystal, which causes dislocations to occur due to thermal stress, causing the single crystal to lose its properties during pulling, resulting in polycrystallization.

[Problems to be Solved by the Invention] (L) In the method using the apparatus shown in Fig. 2, since temperature control is not performed during the cooling process, differences occur in the thermal history in each part of the single crystal, and the element The problem is that there are parts where defects are likely to occur due to heat treatment during the manufacturing process.

(2) In the method using the apparatus shown in Figure 3, rapid cooling occurs during pulling of a single crystal and thermal stress is generated in the single crystal being pulled, causing dislocations and changing the properties of the single crystal during pulling. The problem is that polycrystalization occurs due to the loss of .

This is an attempt to solve the problem and prevent the difference in thermal history and the occurrence of thermal stress during the cooling process of the single crystal.

[Means for Solving the Problems 1] In order to solve the above-mentioned problems, the present invention provides a method for growing a single crystal by pulling it from a raw material melt, by heating the seed side portion of the single crystal being pulled. A single crystal growth method characterized by making the temperature distribution uniform in a part and cooling the single crystal while making the entire temperature distribution uniform after the single crystal is pulled, and a single crystal suitable for carrying out this method. It has a furnace chamber in which a first heat source melts the raw material to form a melt, and a growth chamber in which a single crystal raised from the melt is stored. In a single crystal growth apparatus equipped with a heat source located at a position surrounding a cylindrical portion of the single crystal, a radiant heat shielding plate provided at the opening at the boundary between the furnace chamber and the growth chamber to open and close the opening, and a radiant heat shielding plate provided at the outer periphery of the second heat source. The present invention provides a single crystal growth apparatus characterized by being provided with a cooling cylinder surrounding a single crystal.

[Effect] The present invention will be explained using the drawings.

FIG. 1 is a longitudinal sectional view showing a schematic configuration of an embodiment of a single crystal growth apparatus according to the present invention for growing a silicon single crystal.

A crucible 20 in a furnace chamber 8 is used to melt and store a silicon single crystal raw material. Melting is performed using the first heat source 6. 7 is a heat shield plate disposed outside the first heat source 6. The crucible 20 is supported by a support member 18 made of graphite or the like, which is rotated by a rotating shaft 19 in the direction of the arrow in the figure.

Seed crystal 1 is attached to the lower end of a pulling device 9 that can move up and down while rotating in the direction of the arrow in the figure within the growth chamber 15. The radiant heat shield plate 16, which can be opened and closed freely, is opened, and the pulling device 9 is lowered to bring the seed crystal l into contact with the melt 3.
While rotating in the direction of the arrow in the figure, the single crystal 2 is gradually pulled up to grow the single crystal 2.

A second heat source 11 separate from the first heat source 6 is provided in the growth chamber 15, surrounding the cylindrical portion of the single crystal 2 to be pulled, and surrounding the outer periphery of the second heat source. A cooling cylinder 17 is provided.

In this embodiment, the quartz tube 13 is installed in the cooling cylinder 17 in order to improve the uniformity of heating of the single crystal 2 by the second heat source 11 and to prevent the adhesion of impurities from the second heat source 11. A heat shield plate 12 is provided to prevent overheating caused by the second heat source 11, respectively.

Resistance heating or high-frequency heating is used for the second heat source 11, and the cooling cylinder 17 runs water through a spirally wound pipe.
When rapid cooling is required, the single crystal is cooled from room temperature to 1500°C by flowing liquid nitrogen, measuring the temperature by installing thermal lightning pairs at equal intervals inside the second heat source ti, and performing heating or cooling. It is possible to control any temperature up to

Heating is adjusted by electric power, and cooling is adjusted by controlling the current flow of water or liquid nitrogen.

The heat shield plate 16 moves in the direction of the arrow in the figure at the boundary between the furnace chamber 8 and the growth chamber 15 to open or close the opening at the boundary.

During pulling of the single crystal 2, in order to reduce the difference in thermal history between the seed side and the bottom side of the single crystal 2, the second heat source II heats the seed side part of the single crystal 2, which is farther away from the furnace chamber 8. Prevents the seed side from cooling down.

Note that silicon has a property that when high-temperature pre-heat treatment is applied, the defect density generated by subsequent heat treatment becomes smaller. ) It is desirable to be able to maintain higher values.

After pulling the single crystal 2 to a predetermined length, the whole single crystal is pulled up to the growth chamber 15, and then the furnace chamber 8 and the growth chamber 15 are separated by the radiant heat shielding plate 16, and the inside of the growth chamber t5 is removed. By preventing the single crystal 2 from receiving radiant heat from the surface of the melt 3, the uniformity of the temperature of the single crystal 2 is improved.

Next, the entire single crystal 2 is uniformly cooled by, for example, flowing water into the cooling cylinder 17 and adjusting the flow rate of the water and the amount of electric power of the second heat source 11.

In this device, inert gas flows in through an inert gas inlet 4 and flows out through an inert gas outlet 5.

As explained above, according to the present invention, the single crystal 2
It is possible to reduce the difference in thermal history and the occurrence of thermal stress in each part of the silicon single crystal described above (
For example, the method can also be used to grow other single crystals such as gallium-arsenide compound semiconductors.

[Example] A silicon single crystal having a diameter of 15 cm and a length urn was grown using the single crystal growth apparatus shown in FIG. During single crystal growth, the temperature around the single crystal in the growth chamber was maintained at 1200° C. by a second heat source provided in the growth chamber. After pulling, the entire single crystal was stored in the growth chamber, the furnace chamber and the growth chamber were isolated with a radiant heat shield, and water was flowed into the cooling tube to uniformly cool the single crystal.

Thermocouples were embedded in the longitudinal direction of the obtained single crystal at intervals of 10 crru, and this was placed into the growth chamber of the apparatus shown in Figure 1, lowered into the furnace chamber, and the bottom tip was brought into contact with the molten surface for measurement. The temperature distribution is shown in FIG. 4 as the method of the present invention, and the temperature distribution when this single crystal is similarly charged into a conventional apparatus without a second heat source is also shown as 5 conventional method. It can be seen that the temperature difference between the seed side and the bottom side is smaller than in the conventional method.

The above-mentioned single crystal with the thermocouple embedded therein was charged into the growth chamber of the apparatus shown in step t7, the single crystal was soaked to 1200°C, the furnace chamber and the growth chamber were isolated by a radiant heat shield plate I, and then the cooling cylinder was placed. Figure 5 shows the temperature changes over time on the Miko side and the bottom side of the single crystal.

The above single crystal was charged into the growth chamber of the apparatus shown in Fig. 2, and after soaking the single crystal to 1200°C, the heating by the second heat source was stopped. Temperature changes are also shown in FIG. 5 as a conventional method.

In the conventional method, there is a temperature difference between the bottom side and the seed side, but in the present invention, the culm has been improved so that the temperature difference between the two can be ignored. Furthermore, it is possible to pass through the temperature range of 600 to 900°C, where Is shadow formation of oxidized precipitates is predicted to occur, within 30 minutes.

FIG. 6 shows the apparatus shown in FIG. 1, with the furnace chamber and growth chamber separated by a radiant heat shield plate, the single crystal with a thermocouple embedded inside the growth chamber, and then water poured into the cooling cylinder. This figure shows the temperature distribution of a single crystal during cooling.

1, Il, and rll are the temperature distributions after 15 minutes, 30 minutes, and 45 minutes, respectively, after the start of cooling. It can be seen that a uniform temperature distribution can be obtained along the columnar single crystal in this way, and there is almost no difference in thermal history between the seed side and the bottom example.

A sample for crystal defect observation was located in the longitudinal direction of the single crystal from a wafer cut from the single crystal obtained by the present invention.
Samples were taken out every m, heat treated and light etched, and the density of defects that appeared was investigated. Incidentally, a single crystal produced by the conventional method using the apparatus shown in FIG. 2 was also investigated in the same manner.

As a result, as shown in Figure 7, the difference in the defect density in each part of the single crystal is smaller than that in the single crystal grown using the conventional method, and the absolute number of defect densities is also smaller. Recognize.

FIG. 8 shows the relationship between the distance from the seed crystal and the probability of dislocation occurrence for the single crystal grown according to the present invention and the single crystal grown by the conventional method using the apparatus shown in FIG. This probability is determined by confirming the occurrence of dislocations by changing the external shape of the single crystal,
The location and number of occurrences are determined, and the value is calculated by dividing the number of occurrences by the total number. By cooling the single crystal after finishing pulling,
The probability of polycrystallization occurring during drawing was improved to about 1/3 compared to the conventional method.

[Effects of the Invention] According to the present invention, as a result of improving the cooling process during single crystal growth using the Czochralski method, it is possible to reduce the occurrence of thermal stress in the single crystal, thereby reducing polycrystalization. By being able to reduce the difference in thermal history, for example, it is possible to grow a single crystal that not only reduces the occurrence of crystal defects caused by heating in the semiconductor manufacturing process, but also reduces the differences between the parts of the single crystal. Ta.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing a schematic configuration of an embodiment of the single crystal growth apparatus of the present invention, FIG. 2 is a vertical cross-sectional view showing a schematic configuration of a conventional single crystal growth apparatus, and FIG. FIG. 4 is a longitudinal cross-sectional view showing the schematic configuration of the single crystal growth apparatus; FIG. 4 is a diagram showing the temperature distribution in the longitudinal direction of the single crystal; FIG. 5 is a diagram showing the change in temperature over time during cooling of the single crystal; FIG. Fig. 7 shows the distribution of defect density in the longitudinal direction of the single crystal, and Fig. 8 shows the probability of dislocation occurrence in the single crystal in the longitudinal direction of the single crystal. It is a figure showing distribution of directions. l... Seed crystal 2... Single crystal 3... Melt 4... Inert gas inlet 5... Inert gas outlet 6... First heat source... Heat shield plate ... Pulling device l ... Second heat source 3 ... Quartz tube 5 ... Growth chamber 7 ... - Cooling tube 9 ... - Rotating shaft ... Furnace chamber 0 ... - Viewing window 2 ... Heat shield plate 4 ... Partition plate 6 ... Radiant heat shield plate 8 ... - Holding member O ... - Crucible application agent Kawasaki Steel Corporation

Claims (1)

[Claims] 1. In a method of growing a single crystal by pulling it from a raw material melt, the seed side portion of the single crystal being pulled is heated to make the temperature distribution uniform on the seed side portion, and after the single crystal is pulled, A method for growing a single crystal, characterized by cooling the single crystal while making the entire temperature distribution uniform. 2 It has a furnace chamber in which the single crystal raw material is melted into a melt using a first heat source, and a growth chamber in which the single crystal pulled from the melt is stored. In a single crystal growth apparatus including a second heat source at a position surrounding a cylindrical portion of the single crystal, a radiant heat shielding plate provided at an opening at the boundary between the furnace chamber and the growth chamber to open and close the opening; A single-crystal growth device characterized by being provided with a cooling cylinder surrounding the outer periphery of the single crystal.