Process to manufacture silicon hollow monocrystals

FIELD: chemistry; profiled silicon monocrystals manufacturing.

SUBSTANCE: silicon monocrystals are produced by crucible-free vertical float-zone method, which implies induction generation of a melt drip on initial vertical silicon ingot, seeding of monocrystal being grown on a seed [111] oriented silicon monocrystal, building-up of crystal conical portion to specified diameter, while moving initial ingot and coil in horizontal plane, under conditions, which provide for convex crystallisation front, and emergence of face (111) at melt centre surface at the moment the monocrystal specified diameter is reached. This is followed by hollow monocrystal growing, melt column, which connects the melt ring resting on the growing monocrystal with the drip on initial ingot, being positioned between edge of (111) face and cylindrical surface of the growing monocrystal.

EFFECT: production of silicon hollow (tubular) dislocation-free high-purity perfectly structured monocrystals with [111] orientation.

3 dwg

 

The invention relates to the field of nonferrous metallurgy involved in obtaining a shaped single crystals of various materials for various purposes. The invention, in particular, allows to obtain a hollow (tubular) dislocation of the single crystal silicon of high purity and perfection, on the basis of which can be manufactured semiconductor devices of new generation.

Known Stepanov method [1], in which a shaped crystals, including hollow, is produced by extrusion from the melt using a special shaper. Currently, the Stepanov method is practically the only one that allows you to grow hollow crystals.

The disadvantages of this method are the contact shaper with the melt, which introduces the possibility of contamination of the grown crystal, and a rather complicated design of technological devices. The complexity of thermal unit is not always possible to create conditions for growing high-quality single crystals. In particular, this method cannot obtain hollow (tubular) dislocation of the single crystal silicon of high purity.

Know of any other way to obtain hollow cylindrical crystals [2, prototype], in which the hollow crystal pulling from the melt with a seed in the form of tubes.

However, to grow monoc istoricheskie tubes of molten silicon is not possible due to the lack of high-quality hollow single-crystal nucleating (tubes), and the difficulties of overcoming thermal shock, resulting from contact of the melt with the seed at the time of seeding, which leads to the emergence of multiple centers of crystallization and the growth of polycrystalline tubes.

The problem solved by the invention, the receiving hollow of the silicon single crystal.

The technical effect is to provide opportunities to obtain hollow (tubular) dislocation of the single crystal silicon of high purity and perfection.

The effect is achieved due to the fact that in the known method for obtaining hollow silicon single crystal, comprising growing single crystals by using a seed crystal, in contrast to the known cultivation carried out by the method of vertical floating zone melting, including the creation located vertically of the original ingot of silicon droplets of the melt through the inductor; seeding grown single crystal on the seed crystal in the form of oriented in the [111] direction of the single crystal silicon; razresevanje conical part of the grown single crystal to a specified diameter at the offset of the original ingot and inductor in a horizontal plane and when growing conditions, providing a convex solidification front in the growing single crystal and in the moment of achievement of a given diameter grown the crystal exit face (111) surface in the center of the melt, and then grow the W hollow single crystal at the position of the melt, connecting resting on growing the single crystal ring melt with a drop on the original ingot, between the edge faces (111) and the cylindrical surface of the growing crystal.

The proposed method is new, as in not currently known similar ways to grow hollow single crystals of high purity and perfection. Differences between the proposed method consist in the cultivation of the hollow crystal method, floating zone melting (BZP) under certain growing conditions.

The technical effect is that due to the differences between the proposed method provides receiving hollow (tubular) dislocation single crystal silicon high degree of perfection and purity, on the basis of which can be manufactured semiconductor devices of new generation.

Method of growing single crystals using vertical BZP, as you know, allows you to grow dislocation, high-purity single crystals of semiconductor materials, in particular silicon, ingots, even large diameter. However, to date it is not known obtaining in this way the tubular silicon single crystals of this quality. Still not able to realize the advantages of the method of BZP to solve the tasks of obtaining hollow monocrystalline.

The obviousness of the invention lies in the fact that the detected conditions for growing silicon single crystals by the method of BZP, which allows to obtain hollow crystals, it is not clear from the current level of technology.

The essence of the invention lies in the fact that in the usual way vertical BZP cylindrical rods are offset in the horizontal plane of the original ingot and inductor discovered growing conditions do not violate the crystallographic dislocation growth of a crystal around zakristallizuetsya faces (111), forming the wall of the tube.

After the formation of the melt drops on the source ingot using an inductor, the diameter of which is larger than the diameter of the original ingot, make the connection drops melt with the seed (seeding), which is oriented in the [111] direction of the silicon single crystal.

At the next stage produce razresevanje conical part of the grown single crystal to a specified diameter at the offset of the original strand and coil in the horizontal plane and create the conditions in which is formed a zone of a melt consisting of a part located on the end of the growing single crystal, a column of small diameter and upravlyaushaya surface of the original ingot. All three parts of zone melt continuously linked with the fight during the entire growing process. In the process of razresevanja create thermal conditions ensuring formation of convex solidification front in the Central area of the growing crystal with the surface of the melt in the moment of achievement of the specified diameter of the grown crystal - crystallographic plane (111), which zakristallizuetsya, forming an annular zone of the melt. The required thermal conditions, as is known, by changing the power supply inductor and the speed of growing.

Found that under these conditions, when the continuation of the growth process, the growth of the single crystal occurs with the formation of a cavity in the Central part. The structure of the crystal is not disturbed and, eventually, grown hollow, dislocation single crystal (trumpet) high quality.

The invention is illustrated is shown in figure 1, 2, 3 a schematic depiction of the sequence of the main stages of the method, where:

1 - lower stem with structuralism,

2 - the seed [111],

3 - cone part of the grown single crystal,

4 - convex solidification front,

5 - zone melt,

6 - ring inductor,

7 - the original ingot,

8 - upper collet for mounting the original crystal,

9 - upper rod,

10 - the direction of rotation of the upper rod,

11 - direction of rotation is placed lower rod,

12 - the direction of movement of the upper rod,

13 - the direction of movement of the lower rod,

14 - the offset direction in the horizontal plane of the upper rod,

15 - the offset direction in the horizontal plane of the inductor,

16 - melt,

17 - crystallographic plane (111) of the crystallization front, left on the surface of the melt,

18 - ring of the melt,

19 - the melted surface of the original ingot,

20 is a hollow single crystal.

The proposed method uses the well-known device for vertical BZP cylindrical rods, site growth which consists of the lower stem with structuralism 1, which establishes the monocrystalline seed 2 - the silicon single crystal with orientation [111]; the ring inductor 6, the upper rod 9 with the collet 8, which establishes the original ingot 7. The lower shaft 1 rotates in the direction 11 and moves in the direction 13. The upper shaft 9 rotates in the direction 10, is moved in the direction 12 and is shifted in a horizontal plane in the direction 14. The inductor 6 is shifted in the horizontal plane in the direction 15.

The proposed method is as follows. Inductor 6 create a drop melt on the source ingot 7 and using seed 2 - the silicon single crystal with orientation [111] to produce razresevanje stake the bulk of the single crystal 3. Changing the power supply inductor and the speed of growing, produce thermal conditions necessary for the formation of convex solidification front 4, at least in the Central part of the grown crystal. Razresevanje cone to produce a given diameter as normal with BZP area of the melt 5 (figure 1). Then, displacing the original crystal offset top shaft 9 in the direction 14 and inductor 6 in the direction of 15 form the melt 16 of small diameter and placed between the Central part of the melt and the surface of the grown crystal. Change the power supply and the magnitude of the displacement speed of the upper and lower rods produce thermal conditions of the output of the Central convex portion of the crystallization front 4 with the plane (111) 17, on the surface of the melt. The Central region of the melt located in the growing crystal, crystallized and formed a ring of melt 18, which is connected by a bar 16 with upravlyaushaya surface 19 of the original ingot 7 (figure 2). The new ring of the melt 18 provides crystallization hollow single crystal 20 of a given diameter without breaking its crystallographic orientation (figure 3). The result is grown hollow single crystal on a solid cone base.

An example of a specific application of the method can be implemented is the situation of the proposed method on known devices for vertical BZP-installation "Crystal 206", "Crystal 107", "Crystal 108", "Crystal 114" (development unhitch them. Vpolodere).

Grown hollow silicon single crystals on a solid tapered base with an outer diameter of 28 mm, inner 12 mm, with a crystallographic orientation of [111]. The original grade silicon ingot KP-4 had a diameter of 28 mm, the Seed - crystal silicon-section 3×3 mm, length 70 mm, a resistance of 50.0 Ohms doped with phosphorus. Used a circular coil of copper water-cooled tube with a diameter of 4; the inner diameter of 30 mm, the Rod was rotated with a speed of 31 rpm and shifted vertically with a speed of 2 mm/min Upper stem is shifted in a horizontal plane on the value of 8 mm, and the inductor 4 mm During the growing hollow crystal - tube - ring melt had a width of 8 mm, and the diameter of the melt - 8 mm Obtained hollow silicon single crystals with an external diameter of 28 mm, inner 12 mm with a crystallographic orientation of [111] and a dislocation density of 10-2cm-2

Thus, the present invention allows for the standard equipment for growing semiconductor crystals by the method of BZP to receive tubular dislocation of the single crystal silicon with a crystallographic orientation of [111] high purity, on the basis of which can be made of a semiconductor is the new generation devices.

Sources of information

1. Avestian. A new way of obtaining products (sheets, pipes, rods of various profiles and so on) directly from the melt. ITF, t, issue 3, 1959, s.

2. Wminda, Vigorously, Dgitnikov. Induction heating in the production of high purity materials. Library tweeter-workstation. L.: engineering, 1980, p.40 (prototype).

The method for obtaining hollow silicon single crystal, comprising growing single crystals by using a seed crystal, wherein the cultivation is carried out using vertical floating zone melting, including the creation located vertically of the original ingot of silicon droplets of the melt through the inductor, the seeding of the grown single crystal on the seed crystal, as oriented in the [111] direction of the single crystal silicon, razresevanje conical part of the grown single crystal to a specified diameter at the offset of the original ingot and inductor in a horizontal plane and when growing conditions, providing a convex solidification front in the growing single crystal and, at the moment of achievement of the specified diameter of the grown crystal, the output face (111) on the surface in the center of the melt, and then growing a hollow single crystal at the position of the melt, connecting resting on growing monocrystalline melt with a drop on the original ingot, between the edge faces (111) and the cylindrical surface of the growing crystal.



 

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