JPH0652716B2 - Semiconductor crystalline film manufacturing equipment - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a semiconductor crystalline film manufacturing apparatus, and more particularly to an apparatus for forming a high quality semiconductor crystalline film at a low temperature on a semiconductor crystal surface.

[Prior art]

When a crystal thin film grows on a single crystal substrate, the phenomenon that the crystal orientation of the thin film has a specific relationship with the orientation of the substrate is called epitaxy, and various manufacturing methods have been studied from industrial importance. "Chemical vapor deposition (CVD)" is used for integrated circuit technology that uses semiconductor silicon, and "Liquid Phase Epitaxy" is used for III-V group compound semiconductors used for optical devices and high-speed devices. ) ”Has been developed and put into practical use. However, in recent years, high precision and high quality epitaxial films are required, and the crystal growth temperature is reduced, the controllability is improved (control of film thickness, impurities and composition), and the crystal size is increased to achieve economic efficiency. Beam growth method (MBE, Molecular Beam Epitaxy)
y), plasma CVD, ion beam deposition, and other new crystal growth techniques are being tried. This is a CVD
In the method, since the growth temperature is as high as 1000 ° C or higher, solid phase diffusion of about 1000Å occurs from the high concentration substrate during growth into the growth layer,
This is because autodoping causes a dripping of the impurity distribution of 1000 to 2000Å at the interface.

On the other hand, in the MBE, plasma CVD, and ion beam deposition methods, the temperature is lower than that in the CVD method (MBE is 700 to 800 ° C. in the epitaxial growth method of Si, 750 ° C. in the plasma CVD and ion deposition methods, and MBE in GaAs. 550
The epitaxial growth can be performed at a temperature of 350 to 550 ° C. by plasma CVD. Generally, these have a high substrate temperature, and there is a demand for further reduction in temperature. Of these, the ion attachment method using ion energy is particularly attracting attention because it has the possibility of lowering the temperature. In the method using a reactive gas for ion attachment, only the ions of the elements necessary for film formation are selected by the mass separator, and the deceleration system reduces the ion energy to a low ion energy suitable for attachment. However, it had the drawback of being expensive and having a small ion current. Furthermore, because it is decelerating with the energy of the ions,
There were problems such as contamination, which causes deterioration of film quality, and collision of high-speed neutral particles with the film surface.

Further, in plasma CVD using a reactive gas, a plasma is used to increase the activity at a low temperature and to increase the migration rate of elements on the surface to perform film growth. Si ₃ N ₄ , SiO 2 High quality film is formed at low temperature such as ₂ . Furthermore, epitaxial growth of semiconductor crystals such as Si, GaAs, and GaSb has been studied. However, the epitaxial (also called epi) growth condition is determined by the plasma state, so the substrate temperature can be reduced. Is naturally expected to have its limits.

[Outline of Invention]

In view of such circumstances, the present invention has been made in order to eliminate these drawbacks, and its purpose is to make a reaction gas into a plasma having high activity and to separate the surface of a material without separating it into a single element by mass separation. To the sample substrate by controlling the energy of the ions in the plasma containing the constituent elements of the grown film reaching the temperature of the growth substrate, and at the same time, the ions in the plasma not containing the constituent elements controlled to different states, or An object of the present invention is to provide a semiconductor crystalline film manufacturing apparatus capable of efficiently forming a semiconductor crystalline film on a sample substrate at a lower temperature than conventional by irradiating with light.

In order to achieve such an object, the present invention, a plasma generation chamber for generating plasma by electron cyclotron resonance by microwaves, a sample chamber provided with a sample table on which a sample substrate to be film-formed is mounted, The sample substrate has a substrate heating mechanism that maintains a predetermined temperature, and an ion energy control unit that controls the energy of ions in plasma generated in the plasma generation chamber. Separately arranged, the plasma generated in the plasma generation chamber is arranged to be transported toward the sample substrate, and when the ions in the plasma reach the sample substrate, the energy of the ions is increased. It is controlled by the ion energy controller to have a predetermined energy, of which at least one plasma generation chamber is
A plasma is generated by introducing an inert gas or H ₂ gas that does not contain the constituent elements of the crystalline film, and is used for cleaning the sample substrate or for ion bombardment during film formation, and the sample substrate is the substrate. The semiconductor crystalline film is grown while being kept at a predetermined temperature by a heating mechanism.

Further, the present invention, a plasma generation chamber for generating plasma by electron cyclotron resonance by microwaves,
A sample chamber in which a sample stage for mounting a sample substrate on which a film is to be formed is disposed, a substrate heating mechanism that keeps the sample substrate at a predetermined temperature, and ion energy that controls energy of ions in plasma generated in the plasma generation chamber. The plasma generation chamber is provided separately from the sample chamber, and has a control unit and light irradiation means for irradiating the sample substrate with light, and the plasma generated in the plasma generation chamber is transported in the direction of the sample substrate. When the ions containing at least one of the constituent elements of the crystalline film reach the sample substrate, the energy of the ions is controlled by the ion energy control unit so as to have a predetermined energy. A semiconductor crystalline film is grown while the substrate is kept at a predetermined temperature by a heating mechanism, and light is irradiated onto the sample substrate by the light irradiation means during the film formation. Those were. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

〔Example〕

FIG. 1 is a schematic configuration diagram showing an embodiment of a semiconductor crystalline film manufacturing apparatus according to the present invention, showing a configuration example using two plasma generation chambers. In the figure, 1 and 1a are plasma generating chambers, 2 is a vacuum sample chamber, 3 is an exhaust system, 4 and 4a are microwave introduction windows, 5 and 5a are microwave waveguides, and 6 and 6a are first gas introduction ports. , 7 and 7a are second gas inlets, 8 and 8a are magnetic coils, 9 and 9a are plasma flows, 10 and 10a are plasma outlets, 11 is a sample stage, 12 is a substrate heating mechanism, 13 is a sample substrate, 14 , 14a are power sources for controlling ion energy, 15, 15a
Is a plasma transport tube, 16 and 16a are power sources for the plasma transport tube, 17 is an electrode for extracting ions, 18 is an ion beam,
Reference numeral 19 is a quartz window, and 20 is a sample irradiation light.

The plasma generation chambers 1 and 1a are spatially separated from the sample chamber 2,
It is electrically isolated. The sample chamber 2 is connected to an exhaust system 3 and exhausts a residual impurity gas that inhibits the formation of a high quality film and a gas introduced during the film formation. A microwave source for generating plasma has, for example, a frequency of 2.4.
It is possible to use a 5 GHz magnetron, which is used as a rectangular waveguide 5 or 5 from the microwave introduction window 4 or 4a toward the outside.
a, Further, it is connected to a position through a matching device, a microwave power meter, and an isolator (not shown). The plasma generation chambers 1 and 1a are made of stainless steel (if necessary, the inside of the plasma chamber can be covered with an insulator to minimize the mixing of impurities) to prevent the temperature rise due to plasma generation. The outside is water cooled. The plasma generation chambers 1 and 1a can be installed at arbitrary angles and positions in the vacuum sample chamber 2 shown in FIG. Gas is introduced into the plasma generation chambers 1 and 1a through the first gas inlets 6 and 6a, and the rectangular waveguide 5 and
Microwaves (2.45 GHg) are introduced via 5a, and the DC magnetic field is generated by the magnetic coils 8 and 8a in the direction perpendicular to the microwave electric field under the condition of ECR (with resonance with electron cyclotron) (875 Gauss). When a magnetic field is generated, these interactions (electron cyclotron resonance) cause
The introduced gas is turned into plasma. Plasma extraction ports 10 and 10a are provided at the other ends of the plasma generation chambers 1 and 1a facing the microwave introduction windows 4 and 4a, and the magnetic coils 8 and 8a form a divergent magnetic field at the plasma extraction ports 10 and 10a. Therefore, the plasma flows 9 and 9a are drawn from the plasma drawing ports 10 and 10a. As the shape of the plasma generation chambers 1 and 1a, a microwave cavity resonator configuration is adopted, and as an example, a circular cavity resonance mode TE ₁₁₁ is adopted, and a cylindrical shape having an inner dimension of 90 mm in diameter and 100 mm in height is used , So that the microwave discharge efficiency is improved. In the plasma outlet 10,10a as 1 to 40 ^{mm phi,} and constitutes a reflecting surface for microwaves. The plasma outlet 10,
Numeral 10a is a mesh or grid-like metal plate that may reflect microwaves more efficiently. Further, by reducing the diameter of the outlets 10 and 10a, the pressure difference between the plasma generation chambers 1 and 1a and the vacuum sample chamber 2 can be increased.

The plasma streams 9 and 9a drawn from the plasma outlets 10 and 10a of the plasma generation chambers 1 and 1a are arranged so as to reach the sample stage 11. At this time, if a reaction gas that is easily decomposed is introduced from the second gas introduction ports 7 and 7a, this gas is also ionized and transported toward the sample stage 11. Sample table 11
Incorporates a heating mechanism 12 such as a heater so that the sample substrate 13 can be heated up to about 1000 ° C. At this time, in order to control the energy of the ions contained in the plasma flows 9 and 9a reaching the sample substrate 13, for example, a voltage Ve from the ion energy control power supply 14 is applied between the plasma generation chamber 1 and the sample substrate 13. Is applied, or an electrode 17 for extracting ions (one mesh electrode, one multihole electrode coated with an insulator, etc.) is placed near the sample substrate 13 of the plasma flow 9a, and the plasma generating chamber 1a is extracted. Power supply 14 for controlling ion energy between the electrode 17
The ion energy of the substrate sample 13 can be controlled by applying Ve from a. For example, even if the distance between the plasma generation chambers 1 and 1a and the substrate sample 13 is 20 cm, 20 ^eV to 2 ^KeV
(Microwave power less than 200W, plasma outlet 1
0 ^{mm phi)} ion current density of 0.1 mA / cm ² or less at a lower energy range is obtained. As a method of controlling the ion energy, if a rectangular pulse or an alternating current (including a high frequency) is applied, electrons are also irradiated, and it can be compensated when the accumulation of ionic charges becomes a problem.

Needless to say, high frequency power may be applied to the sample substrate 13 to generate a self-bias on the sample substrate to control the ion energy according to the same principle as that of the high frequency sputtering device. In addition, the plasma transport pipes 15 and 15a
Is to control the spread of the plasma flows 9 and 9a.
The spread of 9a can be reduced. In this way, the first gas inlets 6,6a (or the second gas inlets 7,7a)
The introduced gas is turned into plasma, and the plasma flow 9,
In addition, since the ion energy in the plasma can be controlled as low ion energy by the ion energy control power supplies 14 and 14a, the crystalline thin film can be formed with the ion energy suitable for the temperature of the sample substrate 13.

Further, in FIG. 1, the sample substrate 13 can be irradiated with the light 20 for exciting the sample surface (or for heating the substrate) through the quartz window 19.

For example, irradiation with a high-pressure mercury lamp light or an excimer laser light can promote adsorption of gas molecules to the surface and decomposition and diffusion on the surface, further improving the crystal growth rate and crystallization at low temperature. You can improve your sex. Also,
By heating the surface of the substrate with the CO ₂ laser Ar laser, it is possible to suppress the mixing of impurities from the substrate and the generation of stress during cooling. This substrate irradiation can be incorporated as needed.

Since high-frequency discharge is used in ordinary plasma CVD, the gas pressure used is 10 ^{-2 to} 1 Torr, and it is difficult to maintain discharge at a gas pressure of 10 ^-3 Torr or less.

On the other hand, in the present invention, since plasma generation by electron cyclotron resonance excitation with respect to microwaves is used, the ionization rate is high, and stable discharge is possible at a low gas pressure of 10 ⁻⁵ to 10 ⁻³ Torr. Therefore, even if the plasma is transported, the decrease in the plasma density (the number of ions) due to the collision is small. Further, since a mechanism for generating thermoelectrons such as a thermal filament is not required, stable discharge is maintained even for a reactive gas, and in principle, there is no element that defines the life. Further, since the plasma flows 9 and 9a are divergent magnetic fields of the magnetic coils 8 and 8a, electrons and ions in the plasma flow are prevented from being dissipated in the direction perpendicular to the lines of magnetic force, and the plasma is diffused toward the sample substrate 13. Transported without being done. Further, the spread during the transportation can be suppressed not only by the magnetic field but also by the voltage control of the plasma transportation tubes 15 and 15a. In this way, the plasma flow 9, 9a
Reaches the sample substrate 13 without colliding with the side wall, so that it is possible to reduce the generation of water and impurities due to the collision with the side wall.
Therefore, if the residual impurity gas is sufficiently removed before the film formation (for example, the gas pressure in the vacuum sample chamber 2 is set to 10 ⁻⁸ Torr or less), and then a high-purity gas is introduced, the impurities are obstructed. It is possible to form a high quality crystalline thin film.
Further, since plasma can be transported without lowering the plasma density, it is advantageous to place the ion extracting electrode portion near the substrate, and the configuration shown in FIG. 1 is desirable. Generally, low-energy ions are Coulomba, so the ion beam spreads with distance. Therefore, neutralization by thermal filament is usually performed, but this method is not the optimum method for reactive gas (mixing of impurities,
The life of thermal filament becomes a problem. ).

In this way, the reaction gas is ionized and its energy is reduced to 2
Since it can be controlled with a low energy of 0 to 500 eV, the crystalline thin film can be grown at a low temperature.

That is, migration of ions on the surface, activation of constituent elements,
Due to the effect of nucleation-promoting electric charge and the removal of unstable and unbonded elements, the single crystal can be easily moved to the position where the elements that make up the crystal should exist (difficult to enter the interstitial space) even at low temperature. Since the film stress can be controlled by changing the ion energy, the growth of the heteroepitaxial film becomes easy. In addition to controlling low-energy ions, an electrode for extracting high voltage is added to the plasma generation chambers 1 and 1a so that 10 KV or more of ions are irradiated so that substance synthesis can be performed in a form similar to ion implantation. Changing the device is easy.

As described above, the gas introduction system has the first gas introduction ports 6 and 6a for introducing gas into the plasma generation chambers 1 and 1a and the second gas introduction systems 7 and 7a for introducing gas from the outside. The introduction of gas and the plasma generation chamber can be selected according to the type of film to be formed and the type of gas to be supplied. As the gas, various gases such as an inert gas, a hydroxide, a halide and an organometallic compound gas can be selected. For example, when forming a Si single crystal film, SiH _{4 is} introduced into the first gas inlet 6 or Ar, Kr, and H ₂ gases are introduced into the first gas inlet 6 and SiH _{4 is} introduced into the second gas inlet 6a.
Should be introduced. Further, in order to obtain a doped Si film, gases such as PH ₃ , AsH ₃ and B ₂ H ₆ are mixed from the same position as the SiH ₄ gas inlet by increasing the number of gas inlets, or by using another plasma. If a doping gas mixed with an inert gas is used in the first gas inlet 6 using the generation chamber, the ion energy for film formation and the ion energy for doping can be controlled independently, so that film formation with better controllability can be achieved. (Control of impurity concentration, etc.) becomes possible. With such selection, Si, GaAs, InSb, GaAsP, GaAlAs InP, Z
It is possible to form crystalline thin films of various compound semiconductors such as nSe, SiC, GaN, AlN, and Al ₂ O ₃ .

Another advantage of this method is that the substrate can be cleaned and ions can be irradiated during film formation. That is, in order to grow a single crystal thin film, the sample substrate 13
Since a deposit or a natural oxide film is formed on the crystal substrate to be formed, it is necessary to clean the substrate surface before forming the crystal film. For example, in the case of Si, in order to remove the natural oxide film, the natural oxide film is removed, and a thin oxide film is artificially formed by chemical treatment, and then it is removed by heating at about 800 ° C. immediately before the film formation to remove a clean oxide. I am making a surrender. The existing method can also be used in the case of this device, but not only by heating, but also by making a gas such as Kr, Ar, or H ₂ gas into plasma, and using this ion sputtering as well,
The substrate surface can be efficiently cleaned at a low temperature. Irradiating ions such as an inert gas such as Ar or Kr during film formation is effective in controlling internal stress of the grown film and improving film quality. For these purposes, it is often simple and efficient to arrange a plasma chamber for film formation and another plasma chamber. As another advantage, since the ion energy can be easily changed during film formation, by changing the ion energy at the interface (during initial film formation) and the ion energy at the time of film formation, of
It becomes easier to match various semiconductor thin films such as Si and GaAs.
It is considered that the adhesion of the thin film is improved.

Next, as an example of semiconductor crystalline thin film formation using the device of the present invention, epitaxial growth of Si will be described. Using the plasma generation chamber 1, epitaxial growth of Si was performed. The gas pressure in the vacuum sample chamber 2 is set to 10 ^-8 to 10 ^-9 Torr or less to reduce residual impurities such as O ₂ and C.
After introducing SiH ₄ gas from the gas inlet 6, SiH ₄ gas
CR discharge was performed to form plasma, the plasma generation chamber was set to a positive voltage, and the sample substrate 13 was set to the ground potential. The ion energy control power source 14 controlled the energy of ions of 20 eV or more. After forming a SiO ₂ passivation film using a H ₂ SO ₄ —H ₂ O ₂ solution using a Si (111) substrate, the substrate temperature is 400 to 800 ° C. and the ion energy is 600 to 1200 eV inside the vacuum sample chamber 2. The substrate was cleaned by a method of spattering under the conditions. FIG. 2 shows the relationship between the substrate temperature and ion energy required for epitaxial growth on a Si (111) substrate. Confirmation of epitaxial growth is RH
By observing EED (reflection high-speed electron beam diffraction) pattern.
The backside temperature of the sample table 11 is measured by a thermocouple as the substrate temperature, and the actual temperature of the sample substrate 13 is considered to be lower than this temperature (especially, the difference becomes larger as the temperature becomes higher). As is clear from the figure, epitaxial growth at low temperature is possible by controlling the ion energy. Even at a substrate temperature of 400 ° C., epitaxial growth was possible with the present invention.

FIG. 3 shows another embodiment of the present invention, which is a schematic configuration example in which an evaporation source of solid elements and a plasma generation chamber are combined. In FIG. 3, the same or corresponding parts as in FIG. 1 are designated by the same reference numerals, 21 is a Knudsen cell, 22 and 24 are liquid nitrogen shrouds, and 23 is a solid evaporation source using an electron gun. Here, the Knudsen cell 21 and the solid evaporation source 23 using an electron gun are often used in the MBE apparatus, and are known as an evaporation source with little contamination of impurities and good controllability.

This device is designed to supply solid elements instead of using a reactive gas. For example, Al, Ga, Zn, Si
Various elements such as can be evaporated. For example, by evaporating Al by the solid evaporation source 21 or 23 and supplying O ₂ or N ₂ gas from the plasma generation chamber 1, it is possible to form a single crystal film of Al ₂ O ₃ , AlN or the like. Further, by irradiating ions of Kr, Ar, etc. during film formation as in the case of FIG. 1 (it is easy to add a plasma generation chamber if necessary), the film stress is controlled. Therefore, a higher quality film can be formed. Another advantage of this method is that since the apparatus can be operated on the order of 10 ⁻⁵ to 10 ⁻⁶ Torr, it has good compatibility with an MBE apparatus, enables growth at low temperatures, and does not easily grow by the MBE method (for example,
It is considered to be particularly effective for materials such as II-VI compounds). It is also effective for forming another crystalline film on an amorphous substrate.

In the above embodiment, the plasma generation chambers 1 and 1a are
Although plasma was generated by electron cyclotron resonance using microwaves, it goes without saying that the same effect can be obtained by using other plasma generation as long as it makes use of the gist of the present invention.

〔The invention's effect〕

As described above, according to the present invention, it is possible to perform epitaxial growth at a lower temperature than before by converting the reaction gas into plasma and controlling the energy of the plasmatized ions. Further, since deposition can be performed even at low energy without lowering the ion current density, a deposition rate similar to that of plasma CVD can be achieved at a higher speed than conventional ion deposition. Further, since the film is formed by ionization, M
Unlike adhesion in a thermal equilibrium state such as BE, the problems of segregation and adhesion probability are improved. Further, various combinations of the plasma generation chamber and the gas inlet can be configured, and the present invention is an effective device for various materials.

Further, according to the present invention, when a high-pressure mercury lamp, an excimer laser, or the like is used as the light irradiation means, by irradiating the sample substrate with these lights during film formation, absorption of gas molecules on the surface and Can promote the decomposition and diffusion of
The crystal growth rate can be further improved, and the crystallinity at low temperature can be improved. In addition, by heating the surface of the sample substrate with a CO2 laser or Ar laser, it is possible to suppress the mixing of impurities from the substrate and the generation of stress during cooling.

On the other hand, by controlling a gas such as Kr, ar or H ₂ gas into plasma and irradiating the sample substrate with the ions, the internal stress of the grown film can be controlled and the film quality can be improved. Is made of a material having the same composition as that of the film to be epitaxially grown. However, according to the present invention, the temperature of the epitaxial growth is low. Since the stress due to the difference in thermal expansion from the growth layer is small, various types of heteroepitaxial growth are possible. It is also effective for forming a polycrystalline film on an amorphous substrate (including a low melting point glass substrate).

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a semiconductor crystalline film manufacturing apparatus according to the present invention, FIG. 2 is a diagram showing experimental data for epitaxial film growth conditions by the apparatus of the present invention, and FIG.
The figure is a schematic configuration diagram of another embodiment of the semiconductor crystalline film manufacturing apparatus of the present invention. 1, 1a ... Plasma generation chamber, 2 ... Vacuum sample chamber, 3 ...
... Exhaust system, 4, 4a ... Microwave introduction window, 5, 5a ...
… Microwave waveguides, 6, 6a …… First gas inlet,
7, 7a ... Second gas inlet, 8,8a ... magnetic coil, 9,9a ... plasma flow, 10,10a ... plasma outlet, 11 ... sample stage, 12 ... substrate heating mechanism, 13
…… Sample substrate, 14, 14a …… Ion energy control power supply, 15,15a …… Plasma transport tube, 16,16a …… Plasma transport tube power supply, 17 …… Ion extraction electrode, 18
...... Ion beam, 19 ・ ・ ・ Quartz window, 20 ・ ・ ・ Sample irradiation light, 21 ・ ・ ・ Knudsen cell, 22,24 ・ ・ ・ Liquid nitrogen shroud, 23 ・ ・ ・ Solid evaporation source using electron gun.

Claims (2)

[Claims] 1. Two or more plasma generation chambers for generating plasma by electron cyclotron resonance by microwaves, a sample chamber in which a sample stage for mounting a sample substrate on which a film is to be formed is disposed, and the sample substrate, It has a substrate heating mechanism that maintains a predetermined temperature and an ion energy control unit that controls the energy of ions in the plasma generated in the plasma generation chamber, and the plasma generation chamber is provided separately from the sample chamber. The plasma generated in the plasma generating chamber is arranged so as to be transported toward the sample substrate, and when the ions in the plasma reach the sample substrate, the energy of the ions has a predetermined energy. As described above, at least one plasma generation chamber is controlled by the ion energy control unit, and an inert gas containing no constituent element of the crystalline film is used. , By plasma generated by introducing such as H ₂ gas, is maintained at a predetermined temperature by which used for ion bombardment during washing or membrane generation of said sample substrate, and the sample substrate is a heating mechanism An apparatus for producing a semiconductor crystalline film, wherein the semiconductor crystalline film is grown in a state. 2. A plasma generation chamber for generating plasma by electron cyclotron resonance by microwaves, and a sample chamber in which a sample table on which a sample substrate on which a film is to be formed is placed is disposed.
A substrate heating mechanism that keeps the sample substrate at a predetermined temperature, an ion energy control unit that controls the energy of ions in plasma generated in the plasma generation chamber, and a light irradiation unit that irradiates the sample substrate with light. The plasma generation chamber is arranged separately from the sample chamber, and the plasma generated in the plasma generation chamber is arranged to be transported toward the sample substrate. When the ions containing at least one element among the elements reach the sample substrate, the energy of the ions is controlled by the ion energy control unit, and the sample substrate is controlled by the heating mechanism. The semiconductor crystalline film is grown while being kept at the temperature of
An apparatus for producing a semiconductor crystalline film, wherein the sample irradiating means irradiates the sample substrate with light during the film formation.