JPS6271218A - Thin film forming apparatus - Google Patents

Abstract

PURPOSE:To efficiently form a film on a substrate by applying charge to ultrafine particles produced by energy beam, and forcibly moving the particles to the surface of the substrate. CONSTITUTION:Electrodes 36 are mounted oppositely to a substrate 12, and a high DC voltage is applied between the electrodes 36 and the substrate 12 by a high DC voltage generator 40. The interval between the electrodes 36 and the substrate 12 is necessarily altered according to the tape of reaction gas, and set, for example, to 1-5cm. A voltage to be applied may be in a range of applying charge to the particles produced by a laser and applying kinetic energy that the particles applied with the voltage can move on the substrate, for example, 0.1-15kV. The substrate 12 is heated by a stage 11, and controlled to 50-450 deg.C. Thus, thin film forming velocity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a chemical selective processing device, and in particular, to a chemical vapor deposition reaction (Chemical Vapor Deposition reaction).
The present invention relates to a technique that uses an energy beam to selectively cause an osition.

[Background of the invention]

Conventionally, it has been known that when a laser beam is irradiated onto the surface of a substrate that is in contact with an organometallic compound, a thin metal film is formed on the surface of the substrate due to a photochemical reaction. Furthermore, it is known that a thin film of a compound semiconductor is formed on the substrate surface by irradiating the substrate surface with laser light while bringing an organometallic compound and a gas such as N 2 Ox or N t O into contact with the substrate surface.

For example, the prior art disclosed in Japanese Unexamined Patent Publication No. 58-165330 will be described with reference to FIG.

In FIG. 3, the semiconductor substrate 12 placed on the stage 11 in one reaction chamber 7 comes into contact with the gas introduced from the gas introduction port 9. As shown in FIG.

Laser light oscillated from a laser light source 1 passes through a dye 2, passes through a mirror 6 driven by a position control system 5, and is irradiated onto a semiconductor substrate 12 through an entrance window 8 of a reaction chamber 7.
A thin film is formed on the semiconductor substrate 12.

In conventional techniques for forming thin films on substrates, it is important to improve the thin film formation accuracy and the thin film formation speed. In order to improve the thin film formation rate, it is important to increase the energy density per unit area of laser light or the like irradiated onto the substrate surface.

However, when the intensity of the laser beam is increased, precipitates generated by photochemical reactions adhere not only to the semiconductor substrate surface 12 but also to the inside of the entrance window 8 of the reaction chamber 7, resulting in a decrease in the amount of laser beam transmission. , the precipitation rate does not increase.

Other methods for forming thin films include plasma chemical vapor deposition (C
VD) method is known. In this plasma CVD method, plasma is usually formed by applying high frequency waves, which decomposes the reactive gas and forms a thin film on the substrate. However, it has been pointed out that the plasma CVD method has a drawback that the substrate and the formed film are damaged by high-energy particles in the plasma.

In this way, C
In the VD method, attempts have been made to form bulk functional films in addition to semiconductor films and metal films.

[Purpose of the invention]

An object of the present invention is to provide a selective processing apparatus that can form a thin film on a substrate at a high speed.

[Summary of the invention]

The present invention was developed as a result of detailed study of the reaction process in which a thin film is formed on a substrate surface, and based on this principle, it provides a method for increasing the thin film formation speed without increasing the intensity of the energy beam. It is something.

A reaction that uses light energy to cause a chemical vapor deposition reaction is called photoCVD (Chalical l/ap).
Mercury lamps, xenon lamps, and the like have traditionally been used as light sources. In recent years, various lasers have been developed and are now widely used as light sources for optical CVD. As a reactive gas for photo-CVD, for example, a silane gas such as 5iH4pSizHs can be used to form a Si film, and a germane gas such as GeHa can be used to form a Ge film. Further, in order to form a high melting point metal film, for example, Cr (G O) s s
M o (CO)s.

Carbonyl compounds such as W(G O) 6 = Co z (CO)s can be used. Furthermore, organometallic compounds such as A Q (CHa)a, Z n (C
Ha)z.

AQ of metals by using CdCCHs) etc.

Thin films of Zn and Cd can be formed. Further, by using a mixed gas such as an organometallic compound and NxO that can serve as an oxygen source, a thin film such as A n so s v Z n O can be formed. A thin film of 5iaNa can also be formed from a mixed gas of SiH4 and NHa. Further, by mixing a gas containing an element of group 1 of the periodic table of elements and a gas containing an element of group 1, it is also possible to form a thin film of, for example, GaAs.

When such a reactive gas is irradiated with an energy beam such as a laser, the reactive gas is photoexcited and active species are generated, which collide with each other to generate micronuclei that are attached to the substrate. After adhesion, these micronuclei are thought to gather through migration and form a thin film.

The present inventors have completed the present invention as a result of experimental studies on the above-mentioned thin film formation process.

When a reactive gas is irradiated with a laser beam, microparticles are formed along the laser beam, and when the substrate is at room temperature,
They move slowly along with the gas flow in the reactor,
A part of it adheres to the substrate surface, and most of it moves to the exhaust system and does not participate in film formation.

In addition, a portion of it adheres to the reactor wall and does not participate in film formation on the substrate. In order to form a film from fine particles attached to a substrate, migration on the substrate is the rate-limiting process, and the film formation rate is very slow when the substrate is at room temperature.Therefore, migration on the substrate is usually To increase the speed, the substrate is heated. However, when the substrate is constantly heated, due to gas convection within the reactor, the microparticles generated by the laser beam rise along with the gas flow, reducing the number of particles that adhere to the substrate. However, the film formation rate does not increase.

Furthermore, when the temperature of the reactor wall is lower than the substrate temperature, most of the generated fine particles adhere to the inner wall of the reactor and hardly participate in film formation on the substrate.

As a result of an experimental study of the film formation process in an apparatus that forms a thin film while irradiating an energy beam, the inventors added an electric charge to the ultrafine particles generated by the energy beam and forced the particles onto the substrate surface. By moving the film to the substrate, it became possible to efficiently form a film on the substrate.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in more detail based on examples.

An embodiment of the present invention is shown in FIG. 1, and a sequence for controlling the reaction gas and applied voltage in synchronization with energy beam irradiation is shown in FIG.

A substrate 12 is supported on a stage 11 within the reaction chamber 28 . Although only one substrate is shown in this embodiment, a plurality of substrates may be installed.For example, a silicon wafer is used as the substrate. An electrode 36 is installed facing the substrate 12, and a DC high voltage is applied between the electrode 36 and the substrate 12 by a DC high voltage generator 40. The distance between the electrode 36 and the substrate 12 needs to be changed depending on the type of reaction gas, and is set to, for example, 1 to 5 cm. The voltage to be applied may be within a range that can impart a charge to the ultrafine particles generated by the laser and provide enough kinetic energy to move the charged ultrafine particles onto the substrate1, for example, 0.1 to 15 kV. The substrate 12 is heated by the stage 11 and 5
The temperature is controlled between 0 and 450°C. The substrate 12 may be heated by using a heater or by using something such as an infrared lamp. Furthermore, a laser having a wavelength in the infrared region, such as a YAG laser or a CO2 laser, may be used.

The flow rate control device 20 enters the reaction chamber 28 from the cylinder.
A reaction gas is supplied from the nozzle 26 through the nozzle 26 . In addition, the reaction gas can be not only a gas in a cylinder that is gaseous at room temperature, but also a liquid organometallic compound or a carbonyl compound.
2, gas such as hydrogen or helium can be bubbled and supplied. It is also possible to install a plurality of reaction vessels and supply a plurality of organometallic compounds into the reaction chamber 28.9 The shape of the nozzle 26 for supplying gas into the reaction chamber 28 can be any shape. It is preferable to use one that can supply gas so that the flow on the substrate 12 is close to a laminar flow. Further, in this embodiment, the nozzle 26 for supplying gas and the electrode 36 for applying DC voltage are shown separately, but they may be integrated.

Before starting the reaction, the inside of the reaction chamber 28 must be evacuated by a high vacuum exhaust system 42 to reduce background impurities as much as possible.

After the reaction starts, any reaction pressure is
For example, the pressure is controlled to be maintained at 0.01 to 50 Torr and exhausted by the exhaust system 44. Exhaust system 44 may be shared with high vacuum exhaust system 42 and pressure regulated using a butterfly valve or the like.

The laser beam oscillated from the laser light source 1 is shaped into an arbitrary beam shape via the lens system 38 and sent to the reaction chamber 2.
The inside of the reaction chamber 28 is irradiated through the window plate 32 of 8. As the laser, an excimer laser can be used, but other lasers such as a solid state laser, a gas laser, or a combination of these lasers and a dye laser can also be used. The laser used preferably has a wavelength in the ultraviolet or infrared region. In the case of ultraviolet lasers, photochemical reactions occur due to the excitation of molecules at the electronic level. On the other hand, in the case of an infrared laser, molecular dissociation occurs due to vibrational level excitation of molecules.

In any case, it is necessary to irradiate the target reaction gas with a laser having a wavelength that is absorbed. In the case of a pulsed laser, a signal synchronized with the oscillation pulse signal can be sent to the control device 48, and the reaction gas can be supplied and the voltage can be applied in synchronization with the signal. In the case of a continuous wave laser other than a pulsed laser, a mechanism such as a chopper that pulses the laser light can be provided and a synchronization signal can be sent to the control device 48. In addition, energy beams other than lasers, such as mercury lamps, xenon lamps, 5OR (Synch
rotoron 0rbital radiation
, synchrotron radiation), etc., similar effects can be obtained.

Furthermore, the direction of irradiation of the substrate 12 with this laser light, etc. may be parallel to the substrate 12, or may be irradiated perpendicularly to the substrate 12, or a combination of these two methods will also be the same. It is also possible to irradiate the substrate 12 with two types of laser light.

The basis of the present invention is a method in which an incident energy beam adds a charge to ultrafine particles generated from a reaction gas, and the ultrafine particles are efficiently attached to a substrate by an electric field. Any method of beam incidence and application of the electric field may be used.

A purge gas such as helium is introduced from a purge nozzle 34 into the window plate 32 of the reaction chamber 28 into which the laser beam is incident, so that deposits can be prevented from adhering to the window plate 32. Further, the inside of the window plate 32 may be coated with fluororesin oil or the like.The laser power of the laser light emitted from the reaction chamber 28 can be constantly monitored by a power meter 52.

In this apparatus, the introduction of the reaction gas and the control of the applied voltage are performed in synchronization with the laser irradiation into the reaction chamber 28 using the control bag W148. This sequence is shown in FIG. 2. Before the laser irradiation time Δtx time, the flow control device
The reaction gas supply time is the time required for the reaction gas to reach the substrate 12 in the reaction chamber 28, and the laser beam is irradiated in synchronization with this. Ru. Laser beam is 25×2Ill1
It has a rectangular shape of 11 and is adjusted to a height of 2 cm above the board.

The effect is the same even if the shape of this laser beam is made into any shape by the lens system. Furthermore, the distance between the substrate and the laser beam can be arbitrarily changed. When the laser beam is irradiated into a space where the zero-reactant gas exists, the one-reactant gas is excited by the laser beam and a photodecomposition reaction begins. An organometallic compound such as trimethylaluminum is used as a reaction gas in A, Q (CHa)s −1→A (
1+ product AΩ atoms produced in this reaction by collision.

Ultrafine particles are generated and float along the optical path of the laser beam, and if no manipulation is applied, they float and move along with the gas flow within the reaction chamber 28.

In the present invention, in order to move the thus generated ultrafine particles onto the substrate 12 in a short time and improve the film formation speed on the substrate 12, after the laser beam irradiation, in synchronization with the laser beam irradiation, the ultrafine particles are placed between the substrate 12 and the electrode 36. By applying a voltage, the generated ultrafine particle nuclei can be charged and the ultrafine particle nuclei can be smoothly collected on the substrate 12.

When a voltage is applied between two electrodes under vacuum.

It is known that glow discharge occurs due to the pressure inside the reaction chamber, and a cathode dark area is formed near the cathode, and that the thickness d of the cathode dark area and the pressure P inside the reaction chamber have a relationship as shown in the following equation. There is.

P -dn=A Here, P: Reactant gas pressure (Torr) dn: Thickness value of the dark part of the cathode) A: Constant determined by the type of reaction gas (Torr-al) Also, positive ions exist near the anode. , which is attracted to the cathode and moves.

When an organometallic compound such as TMAQ is irradiated with a laser beam when no voltage is applied between the electrodes, neutral radicals are first generated, and these radicals react with each other in the gas phase to generate ultrafine particle nuclei. do. At this stage, when a voltage is applied between the substrate and the electrode, the gas used as a carrier for a reactive gas such as TMAQ (Ar, He, H2, etc.)
The positive ions generated by ionization move to the cathode part, adhere to the ultrafine particle nuclei, and as a result, move to the IIa pole part and adhere to the substrate. If no voltage is applied, these ultrafine particle nuclei will fall due to gravity alone and adhere to the substrate, but the rate of adhesion to the substrate will be much greater when a voltage is applied. it is obvious.

Although the details of the mechanism by which a film is formed from ultrafine particle nuclei collected on a substrate have not been clarified, it is known that step coverage is improved when a film is formed using a photoexcitation process. Therefore, by adding a voltage application process to the photoexcitation process as in the present invention, a film forming apparatus with good step coverage and high film forming rate can be obtained.

Furthermore, when the substrate is at room temperature, the film formation rate on the substrate is slow, and the adhesion of the film itself is weak, so heating the substrate (
For example, 50 to 400°C) is preferable.

Furthermore, when using an insulator for the substrate, by using a high frequency power source instead of a DC power source between the substrate and the electrode,
Positive ions and electrons alternately collide with the insulator surface, and the positive ions hit the insulator surface? I: Can prevent electricity.

Collection of particle nuclei onto the substrate can be efficiently performed by repeating this operation in synchronization with laser beam irradiation. The substrate may be heated continuously during this operation, or the substrate may be heated to form a film after forming the ultrafine particle layer on the substrate.

An embodiment of the present invention will be described using trimethylaluminum (TMA) as a reaction gas. TNA is a liquid at room temperature and is supplied into the reaction chamber 28 using Hz gas as a carrier. An excimer laser was used as the laser.

The ultraviolet absorption spectrum of TMA is as shown in Figure 4, and in order to carry out an efficient photochemical reaction, ArF (193
It is necessary to use a laser beam of wavelength (nm). In this case, the energy per pulse was approximately 200 mJ. This laser beam was irradiated to a position 2+m above the substrate using a lens system using a cylindrical lens at a size of 25 mm×2+am. 0.5 seconds before laser beam irradiation, TMA was applied to the substrate at 5 Torr using the flow rate control device 20.
I supplied it so that it would be. Simultaneously with laser irradiation (Δtz~
A DC voltage of 500 V was applied between the electrode and the substrate (several ns). In this case, the substrate temperature was kept at 200°C. By repeating the operations of supplying a reactive gas and applying a voltage simultaneously with laser irradiation, it was possible to efficiently form a metal AQ film on the substrate. Film deposition rate is 2,500 people/mi
n, the film formation rate was more than double that of the case where the reactant gas supply was not controlled and no voltage was applied, and the properties of the formed film were almost the same.

Another advantage of the present invention is that the ultrafine particles generated by the laser beam in the reaction chamber 28 are efficiently collected on the substrate, which greatly reduces the amount of by-products deposited inside the laser entrance window. What you can do is reduce it. If a precipitate is formed inside the laser entrance window, the incident power of the laser beam will be extremely reduced, and the efficiency of film formation will be greatly reduced, so it is a great advantage to be able to prevent this.

8 Showing Other Embodiments of the Invention Multiple gases can be used as the reactant gases, including TMA as the organometallic compound and nitrous oxide (NzO) as the organometallic compound. TMA was supplied to the reaction chamber 28 using helium as a carrier.

It is well known that in order to cause a photochemical reaction using a laser, there must be light absorption by the reactant gas. T
The spectra of MA and 4NZO in the ultraviolet region are shown in FIG. To cause a photochemical reaction with an excimer laser, KrF (248 nm) or ArF (1
Unless a laser beam of KrF (248 nm) is used, there is no absorption for these gases.
Since the absorption of the reactant gas is small with the laser beam, one reaction rate is slower than when the ArF (193 nm) laser beam is irradiated even if the same amount of gas is supplied.

TMA and N! It is known that O reacts according to the following formula.

T M A + N z O → AuzOa + product This reaction is complex and the pre-reaction is not precisely known, but the precipitate is alumina and other gaseous substances are produced as by-products.

The mixed gas of TMA and N z O is N z
It was necessary to add O twice or more, and it was supplied so that the total pressure in the reaction chamber 28 was 5 Torr.

ArF (193 nm) was used as the laser, and a lens system was used to create a laser beam with a width of 25 as x 3 m on the substrate.
irradiated at - position. The energy per laser pulse was 200 mJ. The temperature of the board is 350℃,
By repeating the operation of the invention, a thin film of alumina was formed. Silicon was used as the substrate, and it became clear that this alumina had sufficient performance as an insulating film.

Apart from this example, when the substrate temperature was maintained at 100° C., an ultrafine alumina particle layer was formed on the substrate.

In this case, the substrate used was 5US304, 1 inch thick. It was possible to form a porous layer of alumina made of fine particles smaller than the ICO human diameter on this substrate.

In order to form a film over a wide area on the substrate, the laser beam may be scanned or the substrate may be slightly moved. Furthermore, various types of lasers, infrared lamps, etc. may be used as heating means for the substrate.

The formed fine-particle alumina layer can also be used as a catalyst carrier, for example, as an electrode plate for a fuel cell.

The thus formed alumina support layer was fed as a first step with nickel carbonyl (N i (Co)4) together with a hydrogen carrier according to the operation of the present invention. N1
(Co)a is photolyzed by a laser to produce ultrafine Ni particles, which adhere to the alumina carrier layer. The Ni-supported alumina layer can be used as a catalyst for steam reforming, for example as an electrode for internal reforming molten carbonate fuel cells. In this case, methane and steam can be introduced directly into the fuel cell.

Obviously, many other variations are possible. In particular, besides the aforementioned organometallic compounds.

By using dimethyl cadmium and dimethyl zinc, metal films of Cd and Zn can also be made of Cr.

By using carbonyl compounds such as Mo and W, these metal thin films can be formed.

Silane-based compounds, such as S i Ha, S 1
By using zHe and ammonia, Cx Hz,
A film of S 1aNa, S i C can be formed. Furthermore, by using a mixed gas containing elements of groups 1 and 2 of the periodic table, a compound semiconductor of group 1-V can also be formed.

In any case, the scope of the present invention includes a method of efficiently forming a film by using light as excitation energy and applying a potential to a reaction field of a reaction gas generated thereby.

In the present invention, as a method of applying a potential to a field where a reaction gas reacts by laser beam irradiation, an electrode is installed facing the substrate, and the reaction gas is supplied from a nozzle between the electrode and the substrate. If a reaction gas supply nozzle and an electrode can be integrated, the device can be made more compact by using it. Also,
The potential applied between the electrode and the substrate can be positive or negative, in short.

Any material may be used as long as it promotes the movement of the ultrafine particle nuclei generated by the laser beam toward the substrate.

As a method of imparting electric charge to the ultrafine particle nuclei generated by the laser beam, a device that generates thermoelectrons may be provided. In this case, a negative charge can be given to the ultrafine particle nuclei generated by the laser beam, and this can be collected on the substrate surface by a potential applied between the substrate and the electrode. Furthermore, an alternating current voltage may be applied between the substrate and the electrodes in order to prevent charged particles from gathering on the substrate and concentration of charge on the substrate surface.

In order to increase the throughput of substrates on which thin films are formed, it is preferable to provide a sample front chamber and a rear chamber in one reaction chamber so that the substrate can be moved under vacuum.

In the present invention, a method has been shown in which an electrode is provided parallel to the substrate and an energy beam is irradiated between the substrate and the electrode. By allowing natural irradiation, the energy of the energy beam can be used as energy for film formation on the substrate, and the heating temperature of the substrate can be further lowered.

〔Effect of the invention〕

According to the present invention, the film formation rate on the substrate can be increased by more than twice that of the conventional method without increasing the power of the energy beam 11, and throughput can also be improved.

[Brief explanation of drawings]

Fig. 1 shows the system Ml\Xl of an embodiment of the present invention, Fig. 2 shows the control sequence diagram of Fig. 1, Fig. 3 shows a system diagram showing the conventional technology, and Fig. 4 shows the ultraviolet spectrum of the reaction gas. It is a characteristic diagram. 1... Laser, 2... Dye, 3... Diffraction grating, 4
...Laser light of selected excitation wavelength, S...position control system, 6...mirror, 7...reaction chamber, 8...incidence window, 9, 10...gas inlet, Output port, 11... Stage, 12... Semiconductor substrate, 13... Heating coil, 14.15... A pair of electrodes connected to a high frequency power source, 16... Laser A, 18... Laser B, 20...
・Flow rate control device, 22...Cylinder, 24・
... Constant temperature chamber, 26 ... Nozzle, 28 ... Reaction chamber, 3
0...Exhaust nozzle, 32...Window plate. 34... Purge nozzle, 36... Electrode, 38...
Lens system, 40... DC high voltage application device, 42
...High vacuum exhaust system, 44...Exhaust system,
46... Heater control device.

Claims (1)

[Claims] 1. In a device that selectively forms a thin film on a substrate in contact with a reactive gas using an energy beam output from an energy source, an electrode is provided facing the substrate; irradiating the energy beam between the electrodes to decompose the reactive gas;
A thin film forming apparatus characterized in that a thin film is formed by applying a voltage between the substrate and the electrode.