WO1992018672A1

WO1992018672A1 - Device and method for growing crystal

Info

Publication number: WO1992018672A1
Application number: PCT/JP1991/001450
Authority: WO
Inventors: Nobuyuki Akiyama
Original assignee: Komatsu Electronic Metals Co., Ltd.
Priority date: 1991-04-20
Filing date: 1991-10-23
Publication date: 1992-10-29
Also published as: JP2509477B2; JPH05279172A

Abstract

A device and method for growing a crystal which provide a new technique in picking up a crystal to enable control over temperature distribution of a liquid of the melt in the radial direction of the crucible wherein; when a seed crystal is immersed into a material filled in the crucible and melted by a heater as external heating means surrounding said crucible and grown into a crystal while being gradually picked up, a temperature control plate is disposed in a zone above the liquid and around a crystal to be picked up so that, during picking-up of the crystal, a degree of temperature distribution on the liquid may be constantly kept lowest at the solid-liquid interface below the crystal and, at the same time, gradually higher toward the inner wall of the crucible.

Description

Specification

Crystal growth method and crystal growth apparatus

INDUSTRIAL APPLICABILITY The present invention is applied to a crystal growth technique by a pulling method, particularly a single crystal pulling technique of a semiconductor, and is used to determine a radial temperature distribution of a surface temperature of a material melt filled in a crucible. The present invention relates to a technology for controlling a temperature control plate on the top to improve the pulling speed of a single crystal and the quality of the obtained crystal.

Background art

Conventionally, semiconductor single crystal pulling technology, especially silicon single crystal pulling technology using the Czochralski (CZ) method, has been used to improve productivity and increase heat during the pulling process. In order to control the influence of the history on the crystal, for example, a pulling crystal as disclosed in Japanese Patent Publication No. 57-40119 or Japanese Patent Publication No. 2-310400 is used. In addition, there is a technology in which something like a kind of heat radiation plate in the shape of an inverted cone is provided. These increase the cooling rate of the pulled crystal by cutting off or reflecting the heat from the heating heater that passes through the crucible and the radiant heat from the melt surface. It is a thing.

However, in these techniques, the heat radiated by the heat radiating plate partially heats the melt surface, and the temperature distribution of the entire melt is not normal. In some cases, the crystal properties were adversely affected. Also raise Further improvement in speed is also desired from the standpoint of productivity.

Also, conventionally, in the CZ method, the operator who actually pulls the melt surface based on the temperature distribution state of the melt surface knows that the pattern changes even while pulling a single crystal. ing. Normally, this pattern progresses from the top side (at the beginning of pulling) to the tail side (at the end of pulling) of the single crystal. Therefore, in Fig. 4, the pattern changes from X to Z, but it changes to a state like Z. At that point, it will be difficult to pull up the monozong crystals, and in some cases it may be necessary to raise them on the way.

The more the single crystal is pulled at a high speed, the more this temperature distribution pattern becomes more troublesome. Although it is necessary to reduce the calorific value of the heater in order to accelerate the solidification of silicon, the amount of silicon solidification heat (430 cal / g) generated per unit time increases. This is due to the fact that the temperature on the side of the wall must fall slightly. In the CZ method, it was necessary to control the temperature of the melt in the crucible radial direction, but despite the fact that there was no effective technology, this had not been done conventionally. When the temperature distribution pattern changed from Y to Z, it was common to reduce the pulling speed or increase the power to the heater to escape the inability to pull up. This has a very bad effect on the quality and productivity of the pulled single crystal. It has an impact.

DISCLOSURE OF THE INVENTION.

The present invention provides a new pulling technique that enables control of the temperature distribution of the melt in the radial direction in order to solve the problems of the prior art, and the crucible is filled in the crucible. A technique for growing crystals by immersing a seed crystal in a material melt melted by a heater as an external heating means and gradually pulling it up. By providing a temperature control plate above the melt surface and in the area surrounding the pulled crystal, the temperature distribution on the melt surface is the lowest at the solid-liquid interface below the pulled crystal during pulling of the crystal. As a matter of fact, at the same time, it is a method and a device for constantly maintaining the height gradually in the direction toward the inner wall surface of the crucible.

Furthermore, when the temperature control plate is moved so that the distance from the melt surface during the crystal pulling is variable according to the pulling condition, the temperature distribution on the melt surface is controlled to the above-mentioned state. Become.

Further, the temperature control plate has a holding portion along the crystal pulling region, and an umbrella-shaped portion provided at a lower end portion thereof and extending to the vicinity of the inner wall surface of the crucible which opens downward or horizontally.

Here, if the inclination of the umbrella-shaped portion of the temperature control plate is set to 15 ° or less with respect to the horizontal plane, the state of the temperature distribution on the melt surface becomes good. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a vertical front view of a single crystal growth apparatus showing an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a single crystal growth apparatus showing a different embodiment of the present invention.

FIG. 3 is a longitudinal sectional view of a single crystal growth apparatus showing still another embodiment of the present invention.

Fig. 4 is a schematic diagram showing the temperature distribution on the melt surface. FIG. 5 is a longitudinal sectional view of a conventional single crystal growth apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

[Action]

In the present invention, as described above, the temperature distribution state of the surface of the material melt heated and melted by the heater from a portion immediately below the crystal to a portion in contact with the inner wall of the crucible is determined by the temperature distribution during the pulling. Even at this point, it is intended to realize a high-speed pulling of a crystal of good quality by controlling the temperature directly below the crystal to be the lowest, and increasing toward the outside. The reason that the present invention uses such an action is that, in order to obtain a large-diameter silicon single crystal of excellent quality for IC, for example, in the CZ method, the most important point is that the crystal is a melt. The temperature history of the pulled silicon single crystal is determined around the position A (Fig. 4) where it solidifies from the center, which affects the so-called vertical temperature distribution state and the solidification state from the melt. Is there a temperature distribution in the lateral direction of the melt surface toward the inner wall of the crucible? It is.

In the former, the medium temperature state (1300-900 "ϋ) slightly raised from the high temperature state (1350 ° C or less) immediately after the solidification was completed, and the low temperature state (900-450 ° C) Due to the transition to (C), dramatic occurrences such as precipitation of dissolved oxygen in single crystals, or still forming donors, and annihilation of various crystal defects are affected. It is estimated that

The latter, on the other hand, determines how smoothly the crystal can be pulled, regardless of the physical phenomena in the single crystal. In principle, it is thought that the optimum temperature of a silicon melt can only be the temperature of the melt immediately below the silicon single crystal, but when it is manufactured industrially, the melt in the crucible is required. Control of the temperature distribution on the whole, especially on the surface, is important.

In the CZ method, in which heating is performed by a heater from the outer periphery, heat is always radiated from the object to be heated, such as a graphite crucible, a quartz crucible, or a silicon melt, by conduction, radiation, or convection. ing. As a result, the desired lateral temperature distribution becomes like Y shown in Fig. 4, but of course, by controlling the power to the heater, the temperature distribution just below the crystal in Fig. 4 (symbol A temperature of the part), shea cormorants I is maintained in re co down the solidification temperature (1 4 20 ° C), this is _t which is usually automatically controlled have been made, the optical diameter of the sheet re co down monocrystal The so-called “optical” type, which is used for measurement and control, and a single silicon connection There is a so-called “gravity method”, which uses the weight to detect the fluctuation of the crystal diameter and uses it for control.In either case, the heating value of the heater that heats the melt and the single crystal Generally, means for simultaneously controlling the pulling speed and the pulling speed are incorporated in the control system. However, in order to obtain high-quality crystals, it is not good to give the pulling rate a large percentage of its control, and therefore the temperature control of the silicon melt is increased. This is desirable.

That is, when the technology according to the present invention shown in FIGS. 1 to 3 is adopted, the umbrella-shaped portions 9, 99 の of the temperature control plates 7, 77 suppress heat dissipation on the melt surface, Since the holding parts 8 and 8 8 "around the crystal dissipate heat upward by conduction and increase the cooling rate at the solid-liquid interface, the temperature distribution in the radial direction of the melt surface is shown in FIG. It is considered that the temperature control plate will not fall into the state of Y or Z in any situation during the withdrawal, so that this temperature control plate can follow the fluctuation of the melt surface level. If it is made movable, this effect will be more stable.

[Comparative example]

The quartz crucible (16 inches) 2 was placed in the graphite crucible 1 of the single crystal growth apparatus by the CZ method shown in Fig. 5, and the cylindrical graphite heater (16 inch inside diameter) that had been set in advance was used. 3 Place the silicon material inside the quartz crucible. 45kg of nannageite was loaded. The inside of the apparatus is evacuated, purged with argon gas, the material is heated and melted by the graphite heater 3 to form a melt, and a 5 mm X 5 mm seed crystal 4 is immersed in the melt surface. , Got accustomed. By gradually pulling the seed crystal, a single crystal 5 was started and grown to a diameter of 6 inches. After that, the calorific value of the graphite heater was adjusted so that the pulling speed was 1.3 mm / min., And the growth continued. When the growth length of the single crystal approached 400 mm, a part of the silicon melt began to solidify from a part of the inner wall 6 of the crucible into an island shape. The island gradually grew larger, extended toward the center of the crucible, and abandoned pulling because of the danger of contact between the crystal and the island at a crystal length of 48 ram.

Example 1

Using the same apparatus as in the comparative example, the material silicon was completely dissolved, and as shown in FIG. 1, a temperature control plate 7 was loaded in the lifting apparatus. The temperature control plate 7 has a cylindrical holding portion β and an umbrella-shaped portion 9, and the holding portion 8 surrounds the periphery of the single crystal to be pulled. Further, a support portion 14 for supporting the temperature control plate is provided at an intermediate height of the holding portion 8, and is fixed to an upper portion of a heat insulating cylinder 15 of the single crystal growth apparatus. Further, the outer surface 10 of the umbrella-shaped portion 9 reaches near the boundary surface between the inner wall of the quartz crucible and the melt. The inner diameter of the holding part is 229 mm φ, the angle α formed on the horizontal plane of the umbrella-shaped part is 5 °, the shortest distance from the melt surface is 25 mm, and the distance between the outer diameter 10 and the quartz crucible 2 Is 25mm. The umbrella-shaped part 9 keeps the temperature of the melt surface, and the holding part radiates heat at the solid-liquid interface by transmission.

The same operation as in the comparative example was performed, and pulling of a single crystal having a diameter of 6 inches was started at a pulling rate of 1.3ππππι / mill. No solidified islands appeared from the inner wall of the crucible even when the crystal length reached 400 mm. The same pulling speed was maintained until the end, and a 640 mm long silicon single crystal was finally obtained.

When the umbrella-shaped portion is slightly inclined as in this embodiment, the inner contact surface of the inner wall surface of the crucible and the circumferential contact region of the melt can be more effectively kept warm than the solid-liquid interface portion. It was found that the effect was not particularly noticeable when the angle was set more than 15 ° from the horizontal plane.

Example 2

For the single crystal growth length of 300 mm, the shortest distance (H) from the melt surface of the temperature control plate 7 is set to 100 mm, and then H = 50 mm and 600 mni at 400 mm. Then, a silicon single crystal was pulled in the same manner as in Example 1 except that Z was gradually changed so that H = 25 mm. The pulling speed was constant at 1.3 mm / min. And there was no island until the end. Finally

A silicon single crystal with a length of 642ιππι was obtained.

As shown in FIG. 2, the temperature control plate 7 ′ has a shaft 11 fixed to the upper end of the holding portion 8 ′, which is provided on the inner wall 12 of the lifting device chamber 1, so that the temperature control plate 7 ′ can be swung from outside the chamber. The gear 13 rotates by a source (not shown), and moves up and down in conjunction with JP91 / 01450 1 g-1 Example 3

In the same manner as in Example 1, the shape of the temperature control plate 7 was changed as shown in FIG. The temperature control plate employed in the present embodiment has an umbrella-shaped portion 9 "set horizontally and a holding portion 8 部 having a thickness. The surface of the melt is umbrella-shaped. The high temperature is maintained by the reflection and heat retaining action of the part 9〃, and the vicinity of the solid-liquid interface, on the contrary, is effectively radiated by the conduction action of the thick retaining part 8〃 and is maintained at a low temperature. Since the source is outside the crucible, an ideal temperature gradient pattern of the melt surface rising from the center of the crucible to the outside is formed.

According to this example, substantially the same effect was obtained, and a silicon single crystal having a crystal length of 644 mm and a diameter of 6 inches was obtained.

The physical properties of the single crystals obtained in Examples 1 to 3 were examined, but no significant difference from those produced by the conventional method was found.

In each of the embodiments, graphite is used as the material of the temperature control plate. However, a metal material such as molybdenum may be used. Also, a multilayer structure may be used.

According to the present invention, the pattern of the temperature distribution in the crucible radial direction on the surface of the melt gradually increases from the solid-liquid interface to the crucible inner wall surface at any stage from the start to the end of the pulling. Can be maintained Therefore, even if the pulling speed of the single crystal is increased, the melt temperature on the crucible side does not decrease. Therefore, it is possible to pull crystals at a speed at which solidification islands are conventionally formed on the melt and pulling is impossible, thereby improving the productivity.

Industrial applicability

The present invention is applied to semiconductor single crystal pulling technology.

Claims

The scope of the claims

(1) A method for growing a crystal by immersing a seed crystal in a material melt filled in a container and melted by an external heating means and gradually pulling the seed crystal. By providing a temperature control plate in an area surrounding the crystal pulling area above the melt filling area, the temperature distribution on the melt surface is minimized at the solid-liquid interface below the crystal pulled during the crystal pulling. A crystal growth method characterized in that it is kept constantly higher in the direction toward the inner wall surface.

(2) During crystal pulling, the position of the temperature control plate is varied in accordance with the displacement of the melt surface, so that the temperature distribution on the melt surface is changed at the solid-liquid interface under the crystal being pulled during crystal pulling. 2. The crystal growth method according to claim 1, wherein the temperature is maintained at the lowest level and gradually maintained in a direction toward the inner wall surface of the container.

(3) Filled in a container, grown in a molten state by means of external heating means, immersed in a material melt and gradually pulling it up to grow the crystal A crystal growth apparatus, wherein a temperature control plate is provided in a region surrounding the crystal pulling region above the melt filling region.

(4) The temperature control plate is characterized in that it has a holding part along the crystal pulling area and an umbrella-shaped part provided at the lower end thereof, which opens downward or horizontally and reaches near the inner wall surface of the container. 4. The crystal growth apparatus according to claim 3, wherein:

(5) The inclination of the umbrella of the temperature control plate is 5. The crystal growth apparatus according to claim ^{4, wherein the} angle is 15 ° or less.

(6) The crystal growth apparatus according to any one of claims 3 to 5, wherein the temperature control plate is configured to be vertically movable.