JPH0620461U - Molecular beam generator - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a molecular beam generator capable of doping carbon into a compound semiconductor with a good controllability of carbon concentration, improving the life of the carbon filament, and extending the operating time. A plate-shaped insulator having a pair of electrodes fixed to one end side, a molecular beam source cell fixed to the other end side of the insulator formed as a container having a discharge hole in one part, and an electrode at one end A plurality of conductive columns that are electrically connected to and fixed to the insulator and housed in the molecular beam source cell, and are connected in parallel with the carbon filament plate with the tungsten filament plate facing down and fixed to the other end of the column. And a composite filament group,
A molecular beam generator that emits a sublimated carbon molecular beam from an emission hole when electricity is applied to the electrode from the outside.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a molecular beam generator for a molecular beam epitaxial device, and more particularly to an improvement of the molecular beam generator for obtaining a stable molecular beam.

[0002]

[Prior art]

 A conventional molecular beam generator of this type will be described with reference to FIGS. FIG. 4 is a vertical sectional view of a conventional molecular beam generator. FIG. 5 is a top view of the carbon filament plate. The molecular beam generator shown in FIG. 4 is provided in a small chamber (not shown) connected to the epitaxial growth chamber kept in an ultrahigh vacuum of the molecular beam epitaxial device.

In FIG. 5, a carbon filament plate 10 is provided with a connecting portion 13 having a screw hole 12 and a connecting portion 15 having a screw hole 14 at both ends of a filament portion 11 having a small width. In FIG. 4, the connecting portion 13 is fixed to the upper end surface 22 of the support column 20 with the tungsten screw 16 that passes through the screw hole 12, and the connecting portion 15 is the tungsten screw that passes through the screw hole 14 in the upper end surface 23 of the support column 21. It is fixed at 17.

In FIG. 4, a tungsten screw 40 fixes an L-shaped tungsten stopper 30 fixed to the lower end of the carbon support column 20 to an end face 51 of an insulator 50, and at the same time, an end face 52 of the insulator 50. A tungsten electrode 60 is fixed to the. Similarly, the tungsten screw 41 fixes the L-shaped tungsten stopper 31 fixed to the lower end of the carbon column 21 to the end face 51 of the insulator 50, and at the same time, to the end face 52 of the insulator 51, the tungsten electrode. 61 is fixed.

Therefore, the column 20 and the electrode 60 are electrically connected to each other via the insulator 50, and the column 21 and the electrode 61 are electrically connected to each other via the insulator 50, so that the electrodes 60 and 61 are electrically connected. The carbon filament plate 10 can be energized via the. Further, the molecular beam source cell 70 is a container having an emission hole 71 for emitting a molecular beam at one end surface thereof, and the columns 20, 21 and the carbon filament plate 10 are housed in the end surface 51 of the insulator 50. It is fixed.

Next, the operation of the molecular beam generator will be described. When a filament current is supplied between the electrode 60 and the electrode 61, the temperature of the carbon filament plate 10 rises, and when the temperature reaches about 2000 ° C, the carbon sublimes. In ultrahigh vacuum, the mean free path of the molecule becomes large, so the sublimated carbon molecule goes straight in the form of a beam from the emission hole 71 of the molecular beam source cell 70 to the compound semiconductor substrate (not shown) in the epitaxial growth chamber. Reach).

In this case, the concentration of carbon molecules (carrier concentration) reaching the compound semiconductor substrate is controlled by the temperature of the carbon filament plate 10, and the temperature of the carbon filament plate 10 is controlled by the filament current. Therefore, the concentration of carbon molecules is controlled by the filament current.

[0008]

[Problems to be solved by the device]

 In such a conventional technique, a crystal defect existing in the carbon filament plate 10 or a stress generated by fixing the carbon filament plate 10 to the upper end faces 22 and 23 of the columns 20 and 21 is a cause. A phenomenon occurs in which the resistance of a part (hot spot) of the carbon filament plate 10 becomes high. When the resistance increases, the temperature of the hot spot rises accordingly, and the resistance further increases as the temperature rises, which causes positive feedback, making it difficult to control the temperature of the carbon filament plate 10. Therefore, there is a problem that it becomes difficult to control the concentration of carbon when the compound semiconductor is doped. Further, there is a problem that the local temperature rise in the hot spot causes the carbon filament plate 10 to be cut and the operating time of the device is shortened. The present invention has been made in view of the above-mentioned problems of the prior art. The purpose of the present invention is to dope the compound semiconductor with carbon in a well-controlled concentration and to improve the life of the carbon filament plate. The purpose of the present invention is to provide a molecular beam generator that can prolong operating time.

[0009]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention provides a plate-shaped insulator having a pair of electrodes fixed to one end side and a container having a discharge hole partially formed and fixed to the other end side of the insulator. A molecular beam source cell, a plurality of conductive columns having one end electrically connected to the electrode and fixed to the insulator and housed in the molecular beam source cell, and a carbon fiber with a tungsten filament plate facing down. A composite filament group connected in parallel with a filament plate and fixed to the other end of the column, and the sublimated carbon molecular beam is emitted from the emission hole by energizing the electrode from the outside. It is a molecular beam generator.

[0010]

[Action]

 In the present invention, the tungsten filament plate 100 shunts the filament current to the tungsten filament plate 100 side rather than the carbon filament plate 10 due to the difference in the specific resistance between carbon and tungsten, so that the carbon filament plate 10 self-heats. The carbon filament plate 10 is indirectly heated by the self-heating of the tungsten filament plate 100 to sublimate the carbon, ignoring the local temperature rise and resistance increase in the hot spot of the carbon filament plate 10. It can be so. The temperature of the carbon filament plate 10 is stably controlled by the filament current, and the concentration of carbon molecules reaching the compound semiconductor substrate (carrier concentration) is stably controlled by the filament current. Further, the tungsten filament plate 100 reinforces the mechanical strength of the carbon filament plate 10, makes it difficult for the carbon filament plate 10 to be cut, and prolongs the operating time of the apparatus.

[0011]

【Example】

 Next, an embodiment of the present invention will be described with reference to the drawings. In the drawings below, the same parts as those in FIGS. 4 and 5 are designated by the same reference numerals, and the description thereof will be appropriately omitted. FIG. 1 is a vertical sectional view of a specific embodiment of the present invention. FIG. 2 is a top view of the tungsten filament plate. In FIG. 2, reference numeral 100 is the tungsten filament plate of the present invention. The tungsten filament plate 100 has the same shape as the carbon filament plate 10 in FIG. 5, and has a connecting portion 103 having a screw hole 102 and a connecting portion 105 having a screw hole 104 at both ends of a ladder-shaped narrow filament portion 101. It is provided.

In FIG. 1, the composite filament group 110 is constituted by stacking the carbon filament plate 10 on the tungsten filament plate 100, and the connecting portions 13 and 103 are provided with screw holes on the upper end surface 22 of the column 20. Tungsten screws 16 that pass through 12, 102 are fixed, and the connection portions 15 and 105 are fixed to the upper end surface 23 of the column 21 by tungsten screws 17 that pass through the screw holes 14 and 104.

Next, the operation of the molecular beam generator will be described. FIG. 3 is a diagram showing the relationship between the filament current and the carrier level. When a filament current is supplied between the electrode 60 and the electrode 61, the current is shunted to the carbon filament plate 10 and the tungsten filament plate 100, but at a temperature of about 2000 ° C at which carbon sublimes, the carbon ratio Since the resistance is about 10 times that of tungsten (the specific resistance of carbon is about 1000 uΩcm and the specific resistance of tungsten is about 80 uΩcm), the current flowing through the carbon filament plate 10 is a tungsten filament. It is about one tenth of the current flowing through the plate 100.

Therefore, although the self-heating of the carbon filament plate 10 is low, the self-heating of the tungsten filament plate 100 is high, and the carbon filament plate 10 is indirectly heated by the heat and the carbon is sublimated. . Since the mean free path of the molecule becomes large in the ultra-high vacuum, the sublimated carbon molecule becomes a beam and goes straight, from the emission hole 71 of the molecular beam source cell 70 to the compound semiconductor substrate (not shown) in the epitaxial growth chamber. ) To reach.

In this case, the current flowing through the carbon filament plate 10 is as small as about 1/10 of the current flowing through the tungsten filament plate 100, and the temperature of the carbon filament plate 10 is indirectly supported by the tungsten filament plate 100. Since they are arranged, even if a hot spot occurs on the carbon filament plate 10 and the resistance becomes high, the local temperature rise due to the positive feedback at the hot spot becomes negligible.

Therefore, it becomes possible to stabilize and control the temperature of the carbon filament plate 10 by the filament current, and the concentration of carbon molecules reaching the compound semiconductor substrate (carrier concentration) is as shown in FIG. When the filament current is increased, the carrier concentration is increased, and when the filament current is decreased, the carrier concentration is decreased, and the carrier concentration can be stably controlled by the filament current.

Further, the tungsten filament plate 100 reinforces the mechanical strength of the carbon filament plate 10, and when the carbon filament plate 10 is fixed to the upper end faces 22 and 23 of the columns 20 and 21, the carbon filament plate 10 is fixed. It is possible to increase the resistance to the load applied to 10. Therefore, the carbon filament plate 10 is less likely to be cut, and the operating time of the device can be lengthened.

It is to be noted that the carbon filament plates are vertically connected in parallel using a plurality of columns to form a multilayer structure, and the effective area of the filament portion viewed from the compound semiconductor substrate is increased to increase the molecular beam generation efficiency. The structure of the composite filament group of the present invention can also be applied to the line generator.

[0019]

[Effect of device]

 As described above, the present invention provides a plate-shaped insulator having a pair of electrodes fixed to one end side, and a molecule fixed to the other end side of the insulator formed as a container having a discharge hole in part. A radiation source cell, a plurality of conductive columns, one end of which is electrically connected to the electrode and which is fixed to the insulator and housed in the molecular beam source cell, and a carbon filament plate with a tungsten filament plate facing down. A composite filament group connected in parallel and fixed to the other end of the support column is configured to discharge the sublimated carbon molecular beam from the emission hole by energizing the electrode from the outside. Therefore, it is possible to provide a molecular beam generator capable of doping a compound semiconductor with carbon with good controllability of the concentration and improving the life of the carbon filament and prolonging the operating time.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a specific embodiment of the present invention.

FIG. 2 is a top view of a tungsten filament plate.

FIG. 3 is a diagram showing a relationship between a filament current and a carrier level.

FIG. 4 is a vertical cross-sectional view of a conventional molecular beam generator.

FIG. 5 is a top view of a carbon filament plate.

[Explanation of symbols]

 10 Carbon Filament Plate 20, 21 Support 50 Insulator 60, 61 Electrode 70 Molecular Beam Source Cell 71 Emission Hole 100 Tungsten Filament Plate 110 Composite Filament Group

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiromi Kamata 2-932 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. (72) Shinji Kobayashi 2-932 Nakamachi, Musashino City, Tokyo Horizontal Inside Kawakawa Electric Co., Ltd. (72) Tsuyoshi Yagihara 2-932 Nakamachi, Musashino City, Tokyo Yokokawa Electric Co., Ltd. (72) Atsushi Nonoyama 2-932 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. (72) Creator Tadashige Fujita 2-932 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. A plate-shaped insulator having a pair of electrodes fixed to one end side, and a molecular beam source cell fixed to the other end side of the insulator formed as a container having a discharge hole in a part thereof. A plurality of conductive columns, one end of which is electrically connected to the electrode and fixed to the insulator and housed in the molecular beam source cell, and the column which is connected in parallel with the carbon filament plate with the tungsten filament plate facing down. And a composite filament group fixed to the other end of the same, and the sublimated carbon molecular beam is emitted from the emission hole by energizing the electrode from the outside.