JPH0469809B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to cluster ion beam evaporation (ICB).
The present invention relates to a compound semiconductor thin film manufacturing device that forms a high-quality compound semiconductor using a method (method).

[Prior Art] In recent years, two or more elements,
For example, compound semiconductors made of - group elements such as gallium arsenide GaAs and indium phosphide InP are attracting attention for their application to semiconductor devices, taking advantage of the fact that band gaps can be easily controlled and carrier mobility is high. I'm getting used to it. For example, the above-mentioned intermetallic compound semiconductors have been put to practical use in light emitting diodes, semiconductor lasers, etc., and are about to be used in supercomputers.

FIG. 3 is a schematic diagram of a conventional compound semiconductor thin film manufacturing apparatus described in Japanese Patent Publication No. 56-41165. In FIG. 3, 1 is a substrate on which the target compound semiconductor thin film is to be formed, 2 is a substrate holder made of a conductive material and holds the substrate 1, and 3 and 4 are the substrates on which the target compound semiconductor thin film is to be deposited. Evaporated substances A and B containing component elements, such as gallium
Closed crucibles filled with Ga and arsenic As, 5 and 6 are small diameter injection nozzles provided in crucibles 3 and 4, and 35 and 36 are crucibles 3 and 4.
Thermocouples 37 and 38 are provided on the outer walls of the crucibles 3 and 4 to measure the crucible temperature, respectively.
Ionization chambers 11 and 12 are provided near the injection nozzles 5 and 6 of the crucibles 3 and 4, respectively. The ionization chambers 11 and 12 are each composed of ionization filaments 13 and 14 for thermionic emission, grids 15 and 16 for accelerating thermionic electrons emitted from the thermionic filaments 13 and 14, and shield plates 17 and 18. There is.

Further, 39 and 40 are ion accelerating power supplies that maintain the substrate holder 2 at a negative high potential with respect to the ionization chambers 11 and 12 and provide kinetic energy in the direction of the substrate 1 to positively ionized particles; Ionization filament 1 in ionization chambers 11 and 12
Heating power supplies 43 and 44 heat the grids 15 and 16 to a positive potential with respect to the ionization filaments 13 and 14, and heat the grids 15 and 16 to emit the thermoelectrons emitted from the ionization filaments 13 and 14. Ionization power supplies 45 and 46 are used to accelerate and collide particles (clusters) in the ionization chambers 11 and 12 to ionize them, and 45 and 46 are crucible heating power supplies that heat the heating elements 35 and 36 of the crucibles 3 and 4. Note that the heating power supplies 41 and 42 and the crucible heating power supplies 45 and 46 are configured such that their output voltages can be arbitrarily varied from the outside.

Next, 47 and 48 are temperature control units that control the temperatures of the crucibles 3 and 4 by the outputs of thermocouples 37 and 38 attached to the crucibles 3 and 4, respectively. The vapor pressures in the crucibles 3 and 4 are maintained at set values by the temperature control units 47 and 48, respectively.

In addition, each power source 39 to 46 and temperature control section 47
The other parts except 48 are arranged in a vacuum chamber (not shown), and when the gas in the vacuum chamber is removed by the exhaust system, they are placed in a high vacuum atmosphere of 10 ^-4 Torr or less. .

Next, the operation will be explained. First, crucible 3
and 4 are respectively filled with vapor deposition substances A and B containing component elements of the compound to be formed. Note that the vapor deposition substances A and B to be filled are -
When forming a group compound semiconductor, in crucible 3
The crucible 4 is filled with Ga, In, etc., and As, P, etc., respectively. Furthermore, the crucibles 3 and 4 may be filled with single component elements, or the crucibles 3 and 4 may be filled with compounds containing the component elements. However, in the case of a compound containing component elements, it is necessary to select a compound in which the gases of the elements other than the component elements do not have an adverse effect on others.

Next, heating elements 35 and 36 of crucibles 3 and 4
are energized by the crucible heating power supplies 45 and 46, respectively, to heat the crucibles 3 and 4 and evaporate the substance A.
and B vapors Am and Bm are produced. in this case,
Temperature controllers 47 and 48 control the output voltages of crucible heating power supplies 45 and 46, respectively, so that the pressures of steam Am and Bm inside crucibles 3 and 4 are at least 100 times the pressure outside crucibles 3 and 4, respectively. control and adjust the temperatures of crucibles 3 and 4, respectively.

In this way, the steam Am in crucibles 3 and 4
and Bm are generally
Approximately 100 to 2000 atoms form clusters of atoms loosely bonded by Van der Waals forces, so-called clusters Ac and Bc, respectively.

Next, the clusters Ac and Bc enter the ionization chambers 11 and 12 as cluster beams with the kinetic energy at the time of ejection, and by interaction with the electron beams emitted from the ionization filaments 13 and 14, at least one of them is 1
atoms are ionized into positively charged ions, forming cluster ions Ai and Bi.

Then, the cluster ions Ai and Bi are accelerated in the direction of the substrate 1 by the ion accelerating power supplies 39 and 40 and given kinetic energy, respectively, to become a cluster ion beam and impinge on the substrate 1. In addition, the cluster beams of neutral clusters Ac and Bc that are not ionized in the ionization chambers 11 and 12 and move toward the substrate 1 with the kinetic energy of ejection also impinge on the substrate 1, and together with the above-mentioned cluster ion beams, the cluster beams of neutral clusters Ac and Bc travel toward the substrate 1. A thin film 33 of compound semiconductor is deposited (evaporated) on 1.
form.

In this way, since both the cluster beam emitted from the crucible and the cluster beam obtained by ionizing the cluster beam are included in the same beam, the crucible and the ionization chamber will hereinafter be collectively referred to as a beam source.

By the way, when forming a deposited film by the cluster ion beam evaporation method (ICB method) as described above,
By changing the ion acceleration voltage, the deposited film can be changed to amorphous, polycrystalline, or single crystal. In addition, since the optimum ion acceleration voltage for each material element constituting a compound semiconductor thin film to become a single crystal differs for each element, cluster ion acceleration at each beam source is
The ion acceleration voltages of Ai and Bi need to be changed for each crucible 3 and 4 and each ionization chamber 11 and 12.

[Problems to be Solved by the Invention] In the conventional compound semiconductor thin film manufacturing apparatus as described above, even if the optimum ion acceleration voltage is applied to form a single crystal of each element, the potential distribution that occurs between the ionization chamber and the substrate is There is a problem that the expected results cannot be obtained due to the influence of

That is, FIG. 4 is a diagram showing the potential distribution of the conventional compound semiconductor thin film manufacturing apparatus. In addition, the fourth
In the figure, parts that perform the same functions as those in FIG. 3 are designated by the same reference numerals, and their explanation will be omitted.
The equipotential lines indicated by dotted lines in FIG. 4 are not symmetrical with respect to the substrate 1. Therefore, even if the optimum ion accelerating voltage at which each element becomes a single crystal is applied, the cluster ions formed in the ionization chambers 11 or 12, which are kept at a higher potential, will remain at a lower potential as shown by the solid arrow. There was a problem in that the particles were drawn toward the ionization chamber 12 or 11 or even invaded the ionization chamber 12 or 11 and interfered with each other, making it impossible to provide optimal kinetic energy. In particular, the above-mentioned equipotential lines near the shield plates 17 and 18, due to the asymmetry of the potential distribution and local distortion,
Since the cluster ion beam loses its symmetry with respect to the axial direction, the ion trajectory from the time it is emitted until it reaches the substrate 1 is also greatly deviated from the axial direction or distorted, as shown by the solid line arrow in Figure 4. However, there was a problem that a homogeneous cluster ion beam could not be obtained.

Furthermore, although the - group compound semiconductor is a high melting point compound, the vapor pressure of its component V group phosphorus P or arsenic As is extremely high. In other words, the crucible temperature required to evaporate phosphorus P or arsenic As is 500°C.
~600°C, whereas gallium Ga or indium In of the group requires a crucible temperature of about 1000 to 1200°C. Therefore, the radiant heat from the crucible filled with group V elements heats the crucible filled with group V elements, causing the group V substances with high vapor pressure to escape, making it extremely difficult to control the deposition rate. There was a problem.

The present invention was made to solve the above-mentioned problems, and in particular, by improving the potential distribution in the ion acceleration space from the shield plate to the substrate and solving the problem of thermal interference between crucibles. Then,
An object of the present invention is to provide an apparatus for manufacturing a compound semiconductor thin film that can obtain a high-quality compound semiconductor with excellent crystallinity on a substrate.

[Means for Solving the Problems] A compound semiconductor thin film manufacturing apparatus according to the present invention includes each evaporation source that emits a cluster beam of a plurality of component elements of a compound semiconductor, and a cluster beam provided near the evaporation source. an ionization chamber that generates cluster ions by electron bombarding the ionization chamber; and an ion accelerating means that applies a predetermined voltage to each of the ionization chambers to impart impact energy to the cluster ions against a substrate on which a film is to be formed at a ground potential. This is an apparatus for manufacturing compound semiconductor thin films by the cluster ion beam evaporation method, in which each beam source consisting of an evaporation source and an ionization chamber is connected to an accelerating electrode at a ground potential and having an ejection port for emitting a cluster beam and a cluster ion beam. It has a structure in which it is surrounded by a shield plate formed integrally with the shield plate.

[Function] In the present invention, a ground potential ion accelerating electrode having a beam outlet is provided in the beam emission region of each ionization chamber, and a shield plate integrally formed with this electrode is used to accelerate each beam consisting of an evaporation source and an ionization chamber. Since the cluster ion beam is configured to surround the source, firstly, the area where the cluster ion beam is accelerated by the above-mentioned accelerating electrode is limited to a narrow range of the emission part of the beam source. The cluster ions travel in the set beam axis direction without being affected by the electric fields of other beam sources.
This action also serves to impart only optimal kinetic energy to each cluster ion. Furthermore, the shield plate integrally formed with the accelerating electrode not only does not affect the electric field on other beam sources, but also has a heat shielding effect that suppresses radiant heat to other beam sources, so for example, the temperature of each evaporation source Do not interfere with the control.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of a compound semiconductor thin film manufacturing apparatus according to the present invention. In FIG. 1, 1 is a substrate on which the target compound semiconductor thin film is to be formed;
is a substrate holder that holds the substrate 1; 3 and 4 are crucibles (evaporation sources) filled with substances to be evaporated A and B containing each component element of the target compound; 5 and 6 are crucibles 3 and 4; 7 and 8 are crucible heating filaments disposed near the crucibles 3 and 4, respectively; 9 and 10 are heat shield plates for the crucible heating filaments 7 and 8; 11 and 12 are heat shield plates for the crucible heating filaments 7 and 8; ionization chamber, 13 and 14 are ionization filaments for thermionic emission, 15 and 16 are grids, 17 and 1
8 is a shield plate, 19 and 20 are earth potential ion accelerating electrodes provided above the grids 15 and 16, 21 and 22 are earth potential shield plates that surround the entire beam source, and 23 and 24 are crucible heating filaments. 25 and 26 are DC power sources that bias the crucibles 3 and 4 to a positive potential with respect to the crucible heating filaments 7 and 8; 27 and 28 are energizing and heating the ionizing filaments 13 and 14; AC power supply, 2
9 and 30 are DC power supplies that bias the grids 15 and 16 to a positive potential with respect to the ionizing filaments 13 and 14; 31 and 32 are the DC power supplies that bias the grids 15 and 16 and the crucibles 3 and 4 with respect to the accelerating electrodes 19 and 20, which are at ground potential; This is a DC power supply that biases the ions to a positive potential, that is, supplies an acceleration voltage for ions.

Note that the substrate 1, substrate holder 2, crucibles 3, 4,
Crucible heating filaments 7, 8, heat shield plates 9, 10, ionization chambers 11, 12, ionization filaments 13, 14, grids 15, 16, shield plates 17, 18, accelerating electrodes 19, 20, earth potential shield plate 21 , 22 are housed in a vacuum chamber (not shown), and when the gas in the vacuum chamber is removed by an exhaust system, they are placed in a high vacuum atmosphere of 10 ^-4 Torr or less.

Next, the operation of the compound semiconductor thin film manufacturing apparatus according to the present invention will be explained. First, the crucibles 3 and 4 are filled with deposited substances A and B (eg, Ga and As) containing constituent elements of the target compound, respectively.

Next, the crucible heating filaments 7 and 8 are electrically heated by the AC power supplies 23 and 24, respectively, and the crucibles 3 and 4 are kept at a more positive potential than the crucible heating filaments 7 and 8 by the DC power supplies 25 and 26, respectively. Thermionic electrons ejected from the filaments 7 and 8 are accelerated and collided with the crucibles 3 and 4, heating the crucibles 3 and 4, respectively, and producing vapors Am and B of the substances A and B to be evaporated.
Generate Bm respectively. In this case, the crucibles 3 and 4 have a double heat shielding effect of the heat shield plates 9 and 10 and the outer shield plates 21 and 22, so that group V elements with high vapor pressure are removed from other evaporation sources. prevents it from escaping by radiation and
The pressures of Am and Bm make it possible to control the temperature of each crucible 3 and 4 separately to match the stoichiometry of the compounds constituted by them.

In this way, due to the cooling phenomenon based on adiabatic expansion when the vapors Am and Bm ejected from the crucibles 3 and 4 are ejected from the small-diameter injection nozzles 5 and 6, approximately 100 to 2000 atoms are They form clusters of atoms loosely bonded by force, so-called clusters Ac and Bc, respectively.
When these clusters Ac and Bc enter the ionization chambers 11 and 12 due to the kinetic energy at the time of ejection, the clusters Ac and Bc enter the ionization chambers 11 and 12, respectively.
At least one atom constituting the clusters Ac and Bc, respectively, is ionized by colliding with thermionic electrons emitted from the ionization filaments 13 and 14, respectively, and accelerated by the grids 15 and 16, respectively, to form cluster ions Ai and Bi. become.

Next, the cluster ions Ai and Bi are moved toward the substrate 1 by electric field lenses formed by potential gradients formed between the grids 15 and 16 and the acceleration electrodes 19 and 20, respectively, by the DC power supplies 31 and 32. Each is energized and accelerated.

FIG. 2 is a diagram showing how an electric field lens is formed. Note that in FIG. 2, parts that perform the same functions as those in FIG. 1 are designated by the same reference numerals, and their explanations are omitted. The electric field lens forms an equipotential surface as shown in Figure 2, and the cluster ions Ai and Bi
are respectively guided in one direction of the substrate. This situation is strikingly clear when compared with the trajectory of the cluster ions shown in FIG. 4, indicating that a homogeneous cluster ion beam is formed and hits the substrate 1. .

The cluster ions Ai and Bi, along with the neutral clusters Ac and Bc that are not ionized in the ionization chambers 11 and 12 and move toward the substrate 1 due to the kinetic energy of the ejection, impinge on the substrate 1. A thin film 33 of a compound semiconductor with good crystallinity is formed thereon. In this case, the region where the cluster ions are accelerated is the shield plates 21 and 22 and the acceleration electrodes 19 and 2 where the evaporation sources are at ground potential, even if the acceleration voltages applied to the individual evaporation sources are different.
0 respectively, the effect is limited to the effect of the electric field lenses formed between the grids 15 and 16 and the accelerating electrodes 19 and 20. Therefore, the optimum kinetic energy for forming a crystal thin film can be imparted to the cluster ions without being influenced by other electric fields.

In this way, the cluster ions Ai and Bi are accelerated by the respective acceleration electrodes 19 and 20, respectively. This makes it possible to control the state of adhesion of each cluster ion Ai and Bi to the substrate 1, and the pressure of the vapor in the crucibles 3 and 4 is well controlled, resulting in less deviation from the stoichiometric composition. Compound semiconductor thin film 33
can be formed.

In this embodiment, an electron impact method using a filament for heating the crucibles was employed as heating means for the crucibles 3 and 4, but a conventional resistance heating method may also be used.

In addition, in the above embodiment, an example was explained in which two crucibles were provided to manufacture thin films of binary compound semiconductors such as GaAs and InP. However, when manufacturing ternary or more compound semiconductors, it is necessary to use a multilayer instead of a compound. It can also be applied to cases where elemental thin films are continuously formed.

[Effects of the Invention] As explained above, according to the present invention, each beam source of a cluster beam emitted from an evaporation source of each component element of a compound semiconductor and a cluster ion beam obtained by ionizing this cluster beam is A cluster ion accelerating electrode with a beam outlet in the center was provided nearby, and at the same time it was surrounded by a shield plate formed integrally with this electrode. Since the region where the beam is accelerated is limited to a narrow area above each beam source, the cluster ion beam is emitted directly toward the substrate without being affected by the electric fields of other beam sources, forming a homogeneous beam. By doing so, a high quality compound semiconductor thin film can be formed. The effect of eliminating the adverse effects of this electric field is to impart optimal kinetic energy to the cluster ions, which greatly contributes to the formation of a thin film of a compound semiconductor made of a good single crystal.

In addition, the shield plate integrally formed with the accelerating electric field described above not only prevents each beam source from being affected by the electric field, but also prevents other beam sources from being affected by its heat shielding effect. Since it suppresses radiant heat, it does not have an unfavorable effect on the temperature control of each beam source, so it has the effect of forming a thin film of a compound semiconductor with good crystallinity made of elements with different physical and thermodynamic properties. .

Further, an effect can be obtained that a thin film of a compound semiconductor can be formed at low cost without going through a complicated process such as a crystal drawing method.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a compound semiconductor thin film manufacturing apparatus according to the present invention, FIG. 2 is an explanatory diagram of an electric field lens formed by the compound semiconductor thin film manufacturing apparatus shown in FIG. 1, and FIG. 3 is a conventional diagram. FIG. 4 is a schematic configuration diagram of a compound semiconductor thin film manufacturing apparatus, and FIG. 4 is a potential distribution diagram of a conventional compound semiconductor thin film manufacturing apparatus. In the figure, 1 is a substrate, 2 is a substrate holder, 3 and 4 are crucibles, 5 and 6 are injection nozzles, 7 and 8 are crucible heating filaments, 9 and 10 are heat shield plates, 1
1, 12 are ionization chambers, 13, 14 are ionization filaments, 15, 16 are grids, 17, 18
is a shield plate, 19, 20 is an accelerating electrode, 21, 2
2 is a shield plate with earth potential, 23, 24, 2
7, 28 are AC power supplies, 25, 26, 29, 30,
31 and 32 are DC power supplies, and 33 is a thin film. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1.Each evaporation source that emits a cluster beam of a plurality of component elements constituting a compound semiconductor, and an ionization device that is provided near each evaporation source and that bombards the cluster with electrons to generate cluster ions. A cluster ion beam evaporation method comprising: a chamber; and an ion accelerating means for obtaining a cluster ion beam in which a predetermined voltage is applied to each of the ionization chambers to impart impact energy to the cluster ions against a substrate to be deposited at a ground potential to obtain a cluster ion beam. An apparatus for manufacturing a compound semiconductor thin film according to the present invention, wherein each beam source consisting of the evaporation source and the ionization chamber is integrally formed with an accelerating electrode at a ground potential and having an ejection port for emitting the cluster beam and the cluster ion beam, and the accelerating electrode. 1. An apparatus for manufacturing a compound semiconductor thin film, characterized in that each of the thin films is surrounded by a shield plate.