The evaporation crucible

 

(57) Abstract:

The invention relates to semiconductor technology and can be used in molecular beam epitaxy to reduce the density of defects in epitaxial structures. The essence of the invention: in the evaporation crucible containing the volume of evaporated substances and fastened on his neck, separator element, separator element is designed in the form of an insert with a screw channel. The use of the invention reduces the probability of residual vapor vacuum volume in the crucible of the molecular source without a significant reduction in the conductivity of the crucible and significantly reduce the defect density in epitaxial structures. The use of the invention is possible to reduce the defect density in the film of cadmium telluride with a value of 2 to 103cm-2to a value less than 1 to 102cm-2. 2 Il.

The invention relates to semiconductor technology and can be used in molecular beam epitaxy to reduce the density of defects in epitaxial structures.

When the molecular beam-epitaxy binary semiconductors and solid solutions based on them are almost always ELEH where epitaxial growth, in the composition of the residual vapor is always composed of molecules of some or all items, spray volume. Molecules of the same element can get to the source of another element to form a semiconductor compound. This process is most intensive at a time when sources of heat or cooling by direct growth. Very often the temperature in the source below the temperature of decomposition of the formed connection, so the connection will accumulate in the form of small amorphous or polycrystalline clusters, particles, lumps, flakes, etc. During the growth of semiconductor compounds such particles will be carried away by the flow of the evaporated substance and get on the substrate, thereby causing the formation of defects in the growing film.

Partially this problem can be solved mechanical valves, which are supplied molecular sources. In the application Japan 1-278494 IPC C 30 B 23/08, H 01 L 21/203 presents the mechanism of source molecular beam. Source molecular beam contains a crucible, and places the source material. To obtain molecular beam material in the crucible is heated in the oven with a heater. The source beam is equipped with a valve, aterial of the beam on the surface of the flap, it has an embedded heater to heat the surface of the valve to the temperature exceeding the temperature of the material in the crucible.

The disadvantage of this design is that the mechanical shutter closes the source only when heating or cooling source and opens it directly in their growth, thereby preventing the penetration of molecules of another element, paratragedy from the heated elements of the vacuum volume, molecular source and the formation of flakes.

Known source - the Japan patent 59-251517 IPC C 30 B 23/08, C 23 C 14/24, H 01 L 21/203, which describes the evaporation crucible. The crucible is a cylindrical glass, which from the open part on the inner wall in the direction of depth made the tabs. The crucible is provided with a detachable screens with openings, mating with the protrusions, and outlet openings for gas. The screens are installed in the cavity of a cylindrical Cup from its open part. The holes in the screens are arranged so that the holes of adjacent screens do not overlap each other, thus preventing a direct hit paratragedy molecules in the source and direct the contents of the source in the growth zone.

Onryo proportional to the diameter of the hole in the square, see L. N. Rozanov. "Vacuum technology". M.: Vysshaya SHKOLA, 1990, 320 S. prerequisite that all openings of the two closest plates do not overlap between them, imposes a limitation on the diameter of the holes and their number on the plate. In the limiting case, when the plate has a single hole with a diameter of two times smaller than the diameter of the crucible, the system of three such plates reduces the conductivity of 12 times. With increasing number of holes on the plate and, accordingly, with even greater reduction of their diameter, the conductivity of the whole system will be reduced even greater number of times. In addition, the molecular flux arising out of the hole with a small diameter, undergoes adiabatic expansion, pereohlajdenia and is condensed on the plates and the walls of the crucible.

The technical result of the invention is to reduce the probability of residual vapor vacuum volume in the crucible of the molecular source without a significant reduction in the conductivity of the crucible.

The technical result is achieved by the fact that in the evaporation crucible containing the volume of evaporated substances and fastened on his neck, separator element, separator element is designed in the form of an insert with screw bentovim channel (screw), placed in the cavity of the crucible from its open part. The shape of this insert is a spiral, the outer diameter of which is chosen such that the insert tightly inserted into the crucible. Insert a screw channel prevents direct passage of molecules from the vacuum volume of the crucible and back, preventing the formation of chemical compounds in the crucible of the molecular source.

In Fig. 1 presents a view of the crucible with an insert with a screw channel, where 1 - insert with screw channel, 2 - mounting ears, 3 - the crucible of molecular source. Ears 2 does not allow to fail the insert 1 in the crucible 3 and fix it in position.

To obtain molecular beam evaporation crucible is placed in a molecular source. Heater molecular source heats the mouth of the crucible 3 with the insert 1 to a temperature above the decomposition temperature of semiconductor compounds obtained in this vacuum volume. The volume of the vacuum installation, in which the growth of semiconductor compounds, much greater than the volume of the individual crucible molecular source, and the pressure of the residual vapor in the vacuum unit by several orders of magnitude less than the vapour pressure of the substance loaded the insert, do not fall into the crucible molecular source, and the molecules of the evaporated substance after multiple reflections from the walls of the crucible and the surface of the insert out of the crucible of the molecular source. Even if the molecules of the residual atmosphere of the vacuum volume will fall into the crucible and form it flakes chemical compounds, these flakes will not be able to fly from the crucible, as they will settle on the surface of the insert with screw channel.

There are no fundamental restrictions on the thickness of the blade insert with a screw channel. The blades and the mounting ears inserts with screw channel can be anything thin, but the design does not lose its rigidity. So we can assume that the thickness of the blades and the mounting ears a lot less than the diameter of the crucible, and that the insert does not reduce bore diameter of the crucible, and only increases the effective length of the span of the molecules. It is known that the conductivity of the steam line is inversely proportional to its length, see L. N. Rozanov. "Vacuum technology". M.: Vysshaya SHKOLA, 1990, 320 C. To insert the screw channel with two coils, the effective length is increased three times, and then insert a screw channel reduces the conductivity of the crucible is also three times.

Insert to insert all the molecular sources helped to reduce the defect density in the film of cadmium telluride with a value of 2 to 103cm-2to a value less than 1 to 102cm-2. It was also studied the effect insert with screw channel on the directivity pattern of the molecular source. In Fig. 2 presents the distribution of film thickness of tellurium on the surface of the glass plate, positioned on the substrate in the chamber MBE. Deposition of tellurium was carried out at room temperature, the average film thickness is 1000 angstroms, the thickness distribution was determined by the absorption of the laser beam. Curve 4 is the distribution of tellurium from a source without insert, curve 5 - distribution of tellurium from a source with an insert. From the data shown in Fig. 2, it is seen that the insert with a screw channel does not substantially affect the pattern of molecular source.

The evaporation crucible containing the volume of evaporated substances on the neck of which is assigned a separating element, characterized in that the separating element is designed in the form of an insert with a screw channel.

 

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SUBSTANCE: claimed method includes vacuum-plasma application of layered coat wherein for continuous cutting (Ti,Zr)N is coated as upper layer, TiCN is coated as intermediate layer, and TiN is coated as bottom layer. In particular embodiments of invention upper layer (Ti,Zr)N has thickness of 15-25 %, and intermediate layer TiCN has thickness of 25-35 % as reduced to total coat thickness.

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2 cl, 2 tbl, 1 ex

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