The source of atomic hydrogen to molecular beam epitaxy

 

(57) Abstract:

Usage: semiconductor technique, molecular beam epitaxy for precipitaciones preparation of substrates, and also in the process of growing epitaxial layers. The inventive source of atomic hydrogen contains two concentric tubes, means to supply a source of gas connected to an inner tube, the beam splitter used for thermal decomposition of gas molecules, means providing supplied with electrical power splitter. The splitter is made of thin tungsten foil. From the input end he has the form of a tube, the inlet end of which is attached to the tip of the inner tube. The output ends of the strips, bent in the form of loops, continue with the external side of the tube, the beam splitter toward the input end and connected with the outer tube. Inner and outer concentric pipes are electrical contacts for power supply to the splitter. The technical result of the invention is to improve the efficiency of interaction of the gas stream from the splitter, the plot with the exception of low temperature on the output end of the splitter and exclusion article is ptx2">

The invention relates to the field of semiconductor technology and can be used in molecular beam epitaxy (MBE) for precipitaciones preparation of substrates (cleaning the surface from oxygen, carbon and other contaminants), and in the process of cultivation of certain layers.

Known sources of hydrides of arsenic and phosphorus decomposition of molecules (Japan's Bid N 1 - 224295, IPC C 30 B 23/08), consisting of a system of pipes for the supply of the gases, the working tube source containing section mixing arsina cars and phosphine, preheating the gas mixture and the section of thermal decomposition of the molecules, the heater sections are heated by the heater section of decomposition, located outside of the working tube and diaphragm placed inside the section of decomposition. Gases (arsine and phosphine) are served at the source in the specified proportions, are mixed in the mixing section, heated, flowing through the preheating section and in section heated to decomposition temperature of thermal decomposition of the molecules. To improve the efficiency of decomposition of the tube in the area of decomposition introduced aperture, which, when heated, provides a decomposition of gas molecules during collisions with the last of these diaphragms.

ewetel section of decomposition, located outside of the working tube source. For the decomposition of hydrogen molecules into atoms walls of the working tube and put in her diaphragm must be heated above 2000oC. Therefore, the temperature of the heater should be even higher. The working tube and the aperture in this case it is necessary to produce tungsten. In this case, the heater must be electrically isolated from the working tube with high temperature ceramics (e.g., beryllium). The use of ceramics creates a number of problems. First, the system containing ceramics, requires a long and thorough obezvozhivanija, and, otherwise, it is not possible to obtain pure gases at the exit of the source. Secondly, the surface of the heated bodies in this source unreasonably large: this is the total surface of the tube, diaphragms and ceramic insulators. All this leads to large losses by radiation and, therefore, creates a high heat load on the plant, which uses such a source. Finally, thirdly, the working temperature of the beryllium ceramics should not exceed 2000oC, therefore, the working tube and aperture it will have a lower temperature that will cause the low step, IPC C 23 C 14/00), containing the body of the source that includes two concentric tubes, means to supply a source of gas connected to an inner tube, the beam splitter used for thermal decomposition of gas molecules, means providing a summed electrical supply to the splitter.

Inside the inner pipe is the current conductor, made in the form of a tungsten rod, on the end of which is mounted resistive high temperature tungsten filament, twisted into a spiral, used for decomposition (splitting) of hydrogen molecules into atoms. The second end of the spiral is connected electrically with the outer tube by means of a special element in the form of a disc with holes. The gas flows through the inner tube, at its output end to wrap around the heated spiral, with the gas molecules colliding with the heated coils of the spiral, broken down into atoms. Electrical contacts for the power supply to the splitter, are tungsten rod and the outer tube.

This design has the following disadvantages.

First, small cross section of the wire - splitter (the splitter) and gas molecules. How would closely nor was wound SPIRA is P> Secondly, the presence of the heat sink from the output relative to the gas stream end of the splitter through the electrical contact. This leads to the fact that at the exit of the beam splitter is an area with a lower temperature at which it is possible to reverse the recombination of already split atoms. To prevent the recombination of hydrogen atoms on the end of the spiral is necessary to excessively heat the rest of the spiral.

Thirdly, the tube wall of the pipeline within which is located the beam splitter, are lower than the splitter, temperature. When confronted with them can also occur recombination of hydrogen atoms, which reduces the efficiency of cleavage.

All this reduces the efficiency of the device and leads to excessive thermal load on the chamber MBE.

The technical result of the invention is:

- increase of efficiency of interaction of the gas stream from the splitter;

the plot with the exception of low temperature on the output end of the splitter;

- elimination of collisions of gas molecules with elements having a lower temperature than the splitter.

The technical result is achieved by the fact that the source of atomic, and the other external, the money supply in the gas source connected to an inner tube, the beam splitter used for thermal decomposition of gas molecules, means providing supplied with electrical power splitter, the beam splitter is made of very thin tungsten foil (the thinner the foil, the lower the current required to heat the splitter up to operating temperature). This splitter has an input and output ends. From the input end he has the form of a tube, the inlet end of which is inserted into a special sleeve and with the sleeve mounted on the tip of the inner pipe (pipeline), providing gas supply to the splitter. The output ends of the strips, bent in the form of loops, so that the strips continue on the outside of the tube, the beam splitter back to the input end, near which they are connected with the two concentric pipes, which is external. Inner and outer concentric pipes are electrical contacts for power supply to the splitter.

In addition, the source of atomic hydrogen for MBE splitter made of two strips of thin tungsten foil, one of which offormula the end to the tip of the inner tube, and attached to it; the other part is input to the end of the splitter in the form of two strips, bent to form loops in the direction of the input end and continue along the tubular portion of the splitter from the outside.

Use source helical element, which is a strip of tungsten foil, twisted in a spiral, allows you to increase the frequency of collisions of gas molecules with the walls of the tubular part of the splitter.

The invention is illustrated in the following description and the accompanying figures, where Fig. 1 shows the proposed design of the source of atomic hydrogen, in Fig. 2 shows the beam splitter of hydrogen molecules in Fig. 3 shows a variant of the design of the splitter of Fig. 4 shows separately the spiral element and the tip with the inserted helical element.

In Fig. 1-5 shows:

1 - splitter,

2 - input end of the splitter,

3 - the output end of the splitter,

4 - the tubular part of the splitter,

5 two bands, which divides the output part of the splitter;

items 2-5 are an integral part of the splitter;

6 - internal pipe leading to the water splitter is the IR of the pipeline (6),

9 - Bush,

10 - Bush,

11 - Bush,

the inner tube (6) with a tip (8), the outer tube (7) and bushing (9-11) are the means of power supply to the splitter (1);

12 is a ceramic sleeve,

13 - ring

14 - screws

15 is a spiral element (may be absent),

16 is a screen aperture.

Money supply in the gas source connected to an internal pipe in the figures are not shown, as are the standard elements of any gas sources.

The beam splitter (1), used for thermal decomposition of hydrogen molecules into atoms, made of thin tungsten foil. He has a tubular part (4), the input and output ends (2 and 3, respectively). The input end of the tubular part serves as an entrance end of the splitter (2). He put on the tip (8) leading to the splitter hydrogen pipeline (6) and tightly against him special sleeve (9). The output end of the splitter (3) is divided into two bands (5), which are curved in the form of loops in the direction of the input end, continue along the tubular portion of the splitter out the latest and clamped between the outer conical surface of the bushing (10) and the inner conical surface of the sleeve (11). This Col is regima, thus, the input end (2) of the splitter to the tip (7).

The inner tube (6) with a tip (8) and nut (9) and sleeve (10, 11) connected with the outer tube (7) with screws (14) and ring (13), serve as means providing electrical power to the splitter. Ceramic sleeve (12) serves to isolate the means of power supply from each other.

The outer part of the beam splitter (5), curved in the form of loops in the direction of the output end, not only can eliminate the reduced temperature of the output end (3) of the splitter compared to his rest, but also provide additional heating.

The screen aperture (16) is used to reduce radiative energy losses, and to reduce exposure of the processed substrate by the radiation of the beam splitter.

Money supply in the gas source not shown.

Screw-shaped element (15) being inserted into the tip (8) of the pipeline (7), is designed to expand the beam of hydrogen molecules coming out of the pipeline through the tip into the splitter. As a result of increasing the proportion of the constituent molecules in the beam splitter at large angles to its axis, and consequently increases the number of collisions is delno in Fig. 4.

In Fig. 3 shows that the beam splitter (1) of the form described above, having a tubular portion and an output end that is divided into two strips may be made of two strips of thin tungsten foil. From the input (2) end of a strip is formed as two halves of the cylinder, which, when stacked together, form a tubular part (4). Both halves of the tubular part, put together, inserted the input end into the sleeve (9) and with it attached to the tip (8) (not shown in Fig. 3). The output end of the splitter is divided into two bands (5), which are curved in the form of loops in the direction of the input end and continue along the tubular portion of the splitter outside the latter, as described above and shown in Fig. 1, 2.

The source operates as follows. Electric current flows through the inner tube (6), beam splitter (1), the outer tube (7) and heats when the splitter to a temperature of more than 2000oC. the Hydrogen supplied to the source through the feed in the source gas flowing through the inner tube, is fed into the splitter. The hydrogen molecule, leaving the tip (8) inner tube (6) in the beam splitter (1), faced with the heated walls of the tubular part resepimasakan displayed in the camera setup MBE, heading for the surface of the plate.

In this source the use of tubular splitter with the output end, divided into two bands, curved in the form of loops, provides the following benefits:

First, it increases the cross section for the interaction of hydrogen molecules with the heated splitter, as the flow of hydrogen molecules flowing not near the heated spiral and passes through the tube with heated walls. Thus, increasing the proportion of hydrogen molecules, which can be decomposed into atoms at a given temperature of the splitter, and can be reduced the temperature of the splitter, which allows to obtain a given fraction of unfolded molecules.

Secondly, excluded the presence of sites with low temperature at the output end of the splitter, because the output end of the not directly connected with the corresponding electrical contact, and is divided into two curved strips. These strips run along the tubular portion of the splitter (see the drawings and their description above). Therefore, the output end of the splitter not only has a low temperature, but additionally heated by these bands.

Thirdly, are excluded collision of molecules and at the to the splitter itself is a continuation of the tube, the gas pipeline. This increases the efficiency of the splitting of hydrogen molecules into atoms. This helps to reduce the input to a source of electrical power and, consequently, to reduce thermal load on the chamber MBE.

1. The source of atomic hydrogen to molecular beam epitaxy, comprising the body of the source that contains two concentric tubes, the inner and outer, means submission to the gas source connected to an inner tube, the beam splitter, and means providing a summed electrical supply to the splitter, wherein the splitter, made of tungsten, has a thin-walled tubular part, the input and output end and an input end attached to the tip of the inner tube and mounted thereon, and the output end is divided into two strips of the same thickness as the wall of the tubular part, which are curved in the form of loops in the direction of the input end and continue along the tubular portion of the splitter from the outside, while the inner tube with the tip and the outer tube to provide power supply to the splitter.

2. The source of atomic hydrogen under item 1, characterized in that the beam splitter is made of two thin strips in AWT the two halves of the tube, wearing its input end to the tip of the inner tube and mounted thereon, and the other part represents the output end of the splitter in the form of two strips, bent in the form of loops in the direction of the input end and continue along the tubular portion of the splitter from the outside.

3. The source of atomic hydrogen on PP.1 and 2, characterized in that the tip of the inner pipe has a screw-shaped element, made of twisted in a spiral strips of tungsten foil.

 

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