JPH0778763A - Molecular beam flux monitoring device and molecular beam epitaxy equipment provided therewith - Google Patents

Abstract

PURPOSE:To prevent material attached to the inside of the cover of a molecular beam flux monitoring device from being evaporated again so as to enable the monitoring device to accurately measure the intensity of a molecular beam. CONSTITUTION:A grid 13 is connected to a measuring electrode 14 surrounding a collector 12 in a cylindrical cover 11, a filament (ionizing hot cathode) 15 is mounted on an anti-adhesion plate 16 located on the side of the cylindrical cover 11, and the cylindrical cover 11 is set movable between a molecular beam radiating area and a non-radiating area through the intermediary of a housing 17 and a movement mechanism 18. A cooling pipe 21 connected to a cooling tube 21a is spirally wound around the cover 11. By this setup, material attached to the inside of a cover can be prevented from being evaporated again in operation, so that the intensity of a molecular beam can be accurately measured by a molecular beam flux monitoring device of this constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molecular beam flux monitoring device used for controlling the film thickness of a Knudsen cell and the like, and a molecular beam epitaxy for forming a film of a II group VI compound semiconductor provided with the molecular beam flux monitoring device. (MB
E) Regarding the device.

[0002]

2. Description of the Related Art A conventional molecular beam epitaxy apparatus is shown in FIG.
As shown in the configuration explanatory diagram of FIG. 1, a plurality of evaporation sources 2 made of Knudsen cells or the like are annularly arranged in a vacuum chamber 1 evacuated to a high vacuum, and a liquid nitrogen shroud 3 surrounds these evaporation sources 2. A metal material such as Ga or As contained in the evaporation source 2 is surrounded by a heater and heated by a heater to be ejected from the cell in the form of a molecular beam (beam),
It is made to collide with the substrate 5 placed in the vacuum chamber 1 and heated by the substrate heating heater 4, and epitaxial growth is performed while maintaining the stoichiometric composition ratio by utilizing the difference in the adhesion coefficient of each material. There is. In the figure, 6 is a shutter plate of a shutter mechanism attached near the outlet of the evaporation source 2,
The molecular beam traveling from the evaporation source 2 to the substrate 5 is mechanically blocked by the shutter 6 so that the growth can be interrupted, and each evaporation source is independently mounted. Reference numeral 7 is a shutter plate of a shutter mechanism attached to the front of the substrate 3, and 8 is a molecular beam flux monitoring device used for measuring the vapor deposition amount of vapor deposition elements emitted before opening the substrate shutter 7. Reference numeral 9 denotes a moving mechanism of the molecular beam flux monitoring device 8. The vacuum chamber 1 communicates with the preheat chamber and the substrate exchange chamber in the arrow direction. Although not shown in the figure, the molecular beam epitaxy apparatus is provided with a vacuum pump, a molecular beam flux monitor, a substrate rotating mechanism, and other necessary equipment for the molecular beam epitaxy apparatus.

As described above, in the conventional molecular beam epitaxy apparatus, an evaporation source (Knudsen cell) 2 filled with a raw material is directed toward a substrate 5 installed in a vacuum chamber 1 and heated by a substrate heater 4. By heating
The raw material evaporates and radiates in the form of molecular beams to be deposited on the substrate 5. At this time, for example, H ₂ O, CO, N _2, etc. other than the raw materials released by the maintenance of the molecular beam and heating. A liquid nitrogen shroud 3 is usually installed in order to minimize the number of molecules, and to suppress the temperature rise of the part exposed to the heating part and the position facing the raw material and the substrate.

The substrate 5 is used to start and stop the vapor deposition.
By opening and closing the shutter plates 7 and 6 of the shutter mechanism provided between the evaporation source 2 and the evaporation source 2, the vapor deposition can be started and stopped, or the raw material species can be changed.

Further, in order to control the vapor deposition rate, an ionization vacuum gauge is usually used to measure the vapor deposition amount of the vapor deposition element radiated before the opening of the substrate shutter 7. The deposition rate is adjusted by measuring the molecular beam intensity and controlling the temperature of the Knudsen cell. This ionization vacuum gauge is called a molecular beam flux monitoring device.

A conventional molecular beam flux monitoring device is shown in FIG.
As shown in, a grid 13 is provided in the cylindrical cover 11 so as to surround the collector 12 in the central portion and connected to the probe electrodes 14, respectively. One side (on the left side in the figure) of the grid 13 is provided. A filament (hot cathode for ionization) 15 connected to a heating power source (not shown) is attached to the deposition preventing plate 16. These are attached to a housing 17, and the housing 17 can be moved via a moving mechanism 18 between a region where the molecular beam is emitted and a region where the molecular beam is not emitted. In the figure, reference numeral 19 is a probe electrode attached to the side of the housing 17.

The operation of the molecular beam flux monitoring device constructed as described above, that is, the principle of measurement, is that gas and vaporized molecules are ionized by thermoelectrons generated by the filament 15, and ions accelerated by the grid 13 are collected by the collector 12. Incident on the cover 11 and the molecular intensity is read as an ion current.
Has an opening in the direction of the evaporation source 2 such as the Knudsen cell in FIG. 3, and only the vapor deposition material that has passed through the opening is counted as a molecular beam intensity by a pressure value.

[0008]

The conventional molecular beam flux monitoring device (FIG. 4) described above measures the molecular beam intensity before vapor deposition and is stored in a place where the molecular beam is not emitted during vapor deposition. Then, when vapor deposition is performed again, the molecular beam flux monitoring device is again moved to the position of the substrate in the molecular beam, and measurement is performed. At this time, the vapor deposition element previously attached to the cover 11 may be re-evaporated depending on the temperature of the ionizing filament (hot cathode) 5. When re-evaporation occurs, there is a problem that the vaporized element may also be counted as a molecular beam and accurate molecular beam flux may not be measured. This phenomenon is common in high vapor pressure raw materials such as sulfur, zinc, and selenium that are vaporized at low temperatures.

The present invention solves the above-mentioned problems of the prior art, and prevents the re-evaporation of the raw material adhering to the inside of the cover of the molecular beam flux monitoring device, thereby accurately measuring the molecular beam intensity. An object of the present invention is to provide a repeatable molecular beam flux monitoring device and a molecular beam epitaxy device equipped with the molecular beam flux monitoring device.

[0010]

In order to achieve the above object, the present invention comprises a probe electrode and a filament inside a cover, ionizes gas and vapor molecules, and reads the molecular beam intensity as an ionic current. In the molecular beam flux monitoring device, the cover is provided with a cooling mechanism,
The feature is that the re-evaporation of the raw material adhering to the inside of the cover is prevented.

Further, it is characterized in that the cover is provided with a heating mechanism in place of the cooling mechanism.

Further, molecular beams are generated from a plurality of evaporation sources provided in a vacuum chamber, and epitaxial growth is performed on a heated substrate placed in the chamber by utilizing the difference in the sticking coefficient of each material. Thus, in the molecular beam epitaxy apparatus having a shutter mechanism in the vicinity of the substrate for starting and stopping the evaporation from the evaporation source, the measurement electrode and the filament are provided in front of the substrate shutter mechanism. The cover is equipped with a cooling mechanism, and a molecular beam flux monitoring device for preventing re-evaporation of the raw material attached to the cover is attached via a moving mechanism.

Further, the cover is provided with a heating mechanism in place of the cooling mechanism.

[0014]

According to the present invention, as described above, the cover of the molecular beam flux monitoring device is provided with the cooling mechanism so that the inside of the monitoring device can be cooled, so that the re-evaporation of the raw material deposited in the cover is prevented. Therefore, accurate measurement of molecular beam intensity can be repeated.

The same operation can be performed by providing the cover with a heating mechanism instead of the cooling mechanism.

On the other hand, by providing any one of the above molecular beam flux monitoring devices in front of the substrate shutter mechanism of the molecular beam epitaxy device, the deposition amount of the vapor deposition element emitted before the shutter plate of the shutter mechanism is opened. Since accurate measurement is possible, the evaporation rate in the molecular beam epitaxy apparatus can be adjusted accurately by controlling the temperature and control of the evaporation source based on the measurement result.

[0017]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a side view showing a cross-section of a part of a molecular beam flux monitoring device showing an embodiment of the present invention.
The same reference numerals as those shown in FIG. 4 indicate the same or similar parts.

In the figure, a grid 13 is provided in the cylindrical cover 11 so as to surround the collector 12 in the central portion and connected to the probe electrodes 14, respectively.
A filament (hot cathode for ionization) 15 connected to a heating power source (not shown) is attached to the deposition preventive plate 16 on one side (on the left side in the drawing). And these are housing 1
7 is attached to the housing 7, and the housing 17 can be moved via a moving mechanism 18 between an area where the molecular beam is emitted and an area where the molecular beam is not emitted. Although not different from FIG. 4), in this embodiment, a cooling pipe 21 for circulating a coolant such as cooling water or liquid nitrogen is spirally attached to the outside of the cover 11 described above. It is connected to an external cooling device (not shown) via the cooling pipe 21a.

Similarly, a cooling pipe 22 is spirally attached to the outside of the cover 11A, which is provided on the side of the housing 17 at a right angle to the cover 11 and has the probe electrode 19 inside, and the cooling pipe 22 is spirally attached. A cooling medium is circulated through 22a.

As described above, since the cooling pipe 21 is attached to the outside of the cover 11, the cover 11 is cooled when the molecular beam intensity is measured, and therefore the cover 1
Since the re-evaporation of the raw material adhering to the inside of the cover 1 is prevented, only the molecular beam that has passed through the opening of the cover 11 becomes the measured value of the molecular beam intensity as the pressure value. Therefore, at the time of use, the molecular beam intensity can be accurately measured even if the evaporation raw material adheres to the molecular beam flux monitoring device.

FIG. 2 is a partial cross-sectional side view showing another embodiment of the present invention, in which the same reference numerals as those shown in FIG. 1 denote the same or like parts.

This embodiment differs from the previous embodiment (FIG. 1) in that the heating heaters 31 and 32 are wound around the outsides of the covers 11 and 11A, and is the same in other respects. .

Also in this embodiment, as in the previous embodiment (FIG. 1), the re-evaporation of the raw material adhering to the inside of the cover 11 is prevented, so that only the molecular beam passing through the opening of the cover 11 is prevented. Is the measured value of the molecular beam intensity as a pressure value, and therefore, even when the vaporized raw material adheres to the molecular beam flux monitoring device during use, the molecular beam intensity can be accurately determined.

The molecular beam flux monitoring device shown in both the above embodiments (FIGS. 1 and 2) is applied to the monitoring device 8 provided in front of the substrate shutter plate 7 in the molecular beam epitaxy device as shown in FIG. When used by heating the evaporation source (Knudsen cell) 2 filled with the raw material toward the substrate 5 installed in the vacuum chamber 1 and heated by the substrate heater 4, the raw material evaporates, The molecular beam is radiated and vapor-deposited on the substrate 5. At this time, the molecular beam intensity radiated before opening the substrate shutter plate 7 is measured by the molecular beam flux monitoring device. Since the cover 11 is cooled or heated in the apparatus, re-evaporation of the evaporation raw material adhering to the inside of the cover 11 is prevented, and only the molecular beam passing through the opening of the cover 11 is measured. Since the temperature control of the evaporation source 2 is correctly performed.

In the above-mentioned two embodiments, the description has been made with respect to the II VI group compound semiconductor, but the present invention is not limited to this, and of course, it can be applied to III V group compound semiconductors, metals, and all other vapor deposition devices. .

[0026]

As described above, according to the present invention,
A molecular beam flux monitoring device equipped with a probe electrode and a filament inside the cover, which ionizes gas and vapor molecules and reads the molecular beam intensity as an ion current. Since the inside of the apparatus can be cooled, it is possible to prevent re-evaporation of the raw material adhering to the inside of the cover and repeat the accurate measurement of the molecular beam intensity.

The same effect can be obtained by providing the cover with a heating mechanism instead of the cooling mechanism.

By providing any of the above molecular beam flux monitoring devices in front of the substrate shutter mechanism of the molecular beam epitaxy device, the deposition amount of the vapor deposition element radiated before the shutter plate of the shutter mechanism is opened can be accurately measured. Since the measurement can be performed, the evaporation rate in the molecular beam epitaxy apparatus can be accurately adjusted by controlling the temperature and control of the evaporation source based on the measurement result.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional side view of a molecular beam monitoring apparatus showing an embodiment of the present invention.

FIG. 2 is a partial cross-sectional side view of a molecular beam monitoring apparatus showing another embodiment of the present invention.

FIG. 3 is a structural explanatory view of a molecular beam epitaxy apparatus.

FIG. 4 is a partial cross-sectional side view of a conventional molecular beam flux monitoring device.

[Explanation of symbols]

 1 Vacuum Chamber 2 Evaporation Source 3 Liquid Nitrogen Shroud 4 Substrate Heating Heater 5 Substrate 6,7 Shutter Plate 8 Molecular Beam Flux Monitoring Device 9 Moving Mechanism 11, 11A Cover 12 Collector 13 Grid 14 Measuring Element Electrode 15 Filament 16 Adhesion Plate 17 Housing 18 Moving mechanism 19 Measuring element electrode 21,22 Cooling pipe 21a, 22a Cooling pipe 31,32 Heater for heating

Claims (4)

[Claims] 1. A molecular beam flux monitoring apparatus comprising a probe electrode and a filament inside a cover, ionizing gas and vapor molecules, and reading the molecular beam intensity as an ion current, wherein the cover is provided with a cooling mechanism. A molecular beam flux monitoring device characterized by preventing re-evaporation of the raw material attached to the inside of the cover. 2. A molecular beam flux monitoring device comprising a probe electrode and a filament inside a cover, ionizing gas and vapor molecules, and reading the molecular beam intensity as an ionic current, wherein the cover is provided with a heating mechanism. A molecular beam flux monitoring device characterized by preventing re-evaporation of the raw material attached to the inside of the cover. 3. A molecular beam is generated from a plurality of evaporation sources provided in a vacuum chamber, and epitaxial growth is performed on a heated substrate placed in the chamber by utilizing the difference in sticking coefficient of each material. Thus, in the molecular beam epitaxy apparatus having a shutter mechanism in the vicinity of the substrate for starting and stopping the evaporation from the evaporation source, the measurement electrode and the filament are provided in front of the substrate shutter mechanism. A molecular beam epitaxy apparatus, characterized in that a molecular beam flux monitoring device, which is provided with a cooling mechanism on the cover and prevents re-evaporation of the raw material adhering to the inside of the cover, is attached via a moving mechanism. 4. A molecular beam is generated from a plurality of evaporation sources provided in a vacuum chamber, and is epitaxially grown on a heated substrate placed in the chamber by utilizing the difference in sticking coefficient of each material. Thus, in the molecular beam epitaxy apparatus having a shutter mechanism in the vicinity of the substrate for starting and stopping the evaporation from the evaporation source, the measurement electrode and the filament are provided in front of the substrate shutter mechanism. A molecular beam epitaxy apparatus, characterized in that a molecular beam flux monitoring device, which is equipped with a heating mechanism on the cover and prevents re-evaporation of the raw material attached to the cover, is attached via a moving mechanism.