JPS62136571A - Formation of thin film - Google Patents

Abstract

PURPOSE:To improve step coatability and to increase a film forming speed by impressing a voltage between a substrate on which a desired element is to be deposited from a gaseous raw material by irradiating energy to said material and an electrode provided to face the substrate thereby controlling the film forming speed. CONSTITUTION:The substrate 12 and the electrode 20 facing the same are installed in a reaction chamber 7 and the gaseous raw material contg. the desired element is supplied into the chamber. An energy beam of the wavelength matched with the absorption wavelength of said gas is supplied to the gaseous raw material from a laser 1 to form the pulverized particles of the film forming element. The voltage is then impressed between the substrate 12 and the electrode 20 to move the pulverized particles onto the substrate 12. The thin film forming speed is controlled by changing the intensity of the electric field or the time for impressing the voltage.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a chemical vapor deposition reaction using an energy beam (
Chemical vapor, [)epositi
The present invention relates to a method for selectively forming a thin film by using the method of the present invention.

[Background of the invention]

It is known that when the surface of a substrate that is in contact with an organometallic compound is irradiated with laser light, a thin metal film is formed on the surface of the substrate due to a photochemical reaction. It is also known that a thin film of metal oxide or metal nitride is formed when a laser beam is irradiated while an organometallic compound and a gas such as N02, N20, or PjNHs are brought into contact with the substrate surface. ing.

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

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

The laser light emitted from the laser light source 1 passes through the dye 2, passes through the mirror 6 driven by the position control system 5, passes through the entire reaction chamber 70 and the entrance window 8, and is irradiated onto the semiconductor substrate 12.
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 the laser beam irradiated onto the substrate surface.

However, when the intensity of the laser beam is increased, precipitates generated by photochemical reactions are generated not only on the semiconductor substrate surface 12 but also on the reaction chamber 70.
There is a problem in that the particles adhere to the inside of the entrance window 8, and as a result, the amount of laser light transmitted is reduced and the deposition rate is not increased.

In addition to the method using a laser as described above, a plasma chemical vapor deposition (CVD) method is known as a method for forming a thin film. 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 such a plasma CVD method has a drawback that the substrate and the film being formed are damaged by high-energy particles in the plasma.

In addition, sputtering is widely used to form thin films, but there are problems with step coverage, and as miniaturization progresses, problems such as wire breakage occur. It is expected that.

[Purpose of the invention]

An object of the present invention is to provide a thin film forming method that provides good step coverage, a high film formation rate, and allows the film formation rate t to be adjusted.

[Summary of the invention]

The present invention was developed as a result of studying a reaction process for forming a thin film on a substrate by a photoexcitation reaction using an energy beam, particularly a laser 51, and provides a method for forming a thin film using a photoexcitation reaction with a high deposition rate. It is something.

PhotoCVD (Chemical VaporJ) is a reaction that uses light energy to cause a chemical vapor deposition reaction.
)eposition), and mercury lamps, xenon lamps, and the like have traditionally been used as light sources. In recent years, the development of various lasers has progressed, and this has led to optical CV.
It has become widely used as a light source for D. When forming metal thin films such as wiring materials, organic metal compounds, metal carbonyls, and the like are often used as raw material gases, and in particular, those that are liquid at room temperature are mainly used. Furthermore, when forming a thin film of metal oxide or metal nitride, a method is used in which N20 or NH8 is supplied together with an organometallic compound or metal carbonyl.

When such a reactive gas is irradiated with an energy beam such as a laser beam, the reactive gas is excited by a photochemical reaction and active species are generated, which collide with each other in the gas phase to form micronuclei. It is thought that after the micronuclei are generated and attached to the substrate, the micronuclei aggregate on the substrate to form a thin film. The inventors conducted detailed experimental studies on the process of forming a thin film, and as a result, completed the present invention. When a reactant 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, and some of them reach the substrate surface. 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 turn fine particles attached to a substrate into a thin film, migration on the substrate is the rate-limiting process.
Film formation rate is very slow when the substrate is at room temperature1. Therefore,
Typically, the substrate is heated to increase the rate of migration on the substrate. However, when the substrate is constantly heated, the gas convection within the reactor causes the microparticles generated by the laser beam to rise due to the flow of gas, reducing the number of particles adhering to the substrate. Film formation rate does not increase. Furthermore, when the temperature of the reactor wall is lower than the substrate temperature, most of the fine particles generated above adhere to the inner wall of the reactor and hardly participate in film formation on the substrate.

When an electrode is provided facing the substrate in the reactor and the laser beam is fully irradiated between the substrate and the electrode, a charge is given to the microparticles generated by the laser beam, and as a result, the microparticles are attached to the substrate by the electric field. It has become clear that the fine particles formed in the gas phase are efficiently collected on the substrate and the film formation rate is improved. The biofilm velocity at this time is proportional to the electric field strength, and increases as the voltage application time becomes longer.

Furthermore, when a voltage is applied between the substrate and the electrode, surface charges are concentrated on the through-hole portions of the substrate, and the biofilm speed at that portion is significantly increased and step coverage is also improved. In addition, when forming the entire wiring metal film on the interlayer connection part, charges are concentrated on the underlying metal part, for example, Al, and the formation rate of the metal thin film is relatively high compared to the insulating film part. This also improves the embedding of metal into the connection holes.

[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. A substrate 12 is supported on a stage 11 within the reaction chamber 7 .

For example, a silicon wafer can be used as the substrate.

An electrode 20 is installed facing the substrate 12, and a voltage is applied between the electrode 20 and the substrate 12 by a high voltage control device 24 and via a high voltage application device 22. stage 11
The electrode 20 is insulated from the reaction chamber 7, and DC voltage, DC alternating voltage, etc. are used. To prevent any buildup of charge on the substrate 12, it is desirable to use a full alternating voltage.

A laser beam emitted from the laser 1 is processed into an arbitrary laser beam shape by a lens system 21 and irradiated between the electrode 20 and the substrate 12. The raw material gas is supplied to the raw material gas adjustment device 26.
The gas composition is adjusted to a desired value and supplied to the reaction chamber 7 using a nozzle or the like. The reaction chamber 7 is connected to a vacuum evacuation system 34, and the background wand is e.g.
It is exhausted to r order. When forming a thin film, the inside of the reaction chamber 7 is adjusted to, for example, IX I Q-'' to 10 TOrr, and the raw material gas is supplied. By-products are prevented from being deposited inside the laser beam entrance window 8 of the reaction chamber 7. For this purpose, a purge gas 36 is supplied, but in order to reduce the concentration of the source gas near the laser beam entrance window 8 as much as possible, it is desirable that the direction of incidence of the laser beam and the flow direction of the source gas are countercurrent.

The raw material gas is decomposed by a photochemical reaction by laser light, and microparticles that become the raw materials for film formation are generated. 1. The voltage applied between the electrode 20 and the substrate 12 imparts an electric charge to these microparticles, which move onto the substrate. It is sufficient to apply kinetic energy within the range of 0.1 to 15 KV, for example. This optimum voltage varies depending on the reactivity during film formation, but conditions in which glow discharge occurs are not preferred. This is because if a voltage higher than necessary is applied, high-energy ion species are generated and collide with the substrate at high speed, potentially damaging the substrate.

The film formation rate on the substrate 12 is monitored by a film thickness monitor 28, and this signal is used to control the voltage control device 22 via the control device 24 to change the electric field strength or voltage application time to control the film formation on the substrate 12. Control membrane speed. The deposition rate is proportional to the electric field strength, other things being the same, and
When the electric field strength is the same, it is proportional to the voltage application time, so
Either one may be used as the overall control index.

A crystal film thickness monitor can be used as the film thickness monitor 28. If the film to be formed is transparent, optical monitoring devices such as laser light interferometry can also be used.

FIG. 2 shows another embodiment of the invention. In this example, a method of simultaneously forming a film on a plurality of substrates (three substrates are shown in the figure) was shown. Each substrate (12a to 12
C) has electrodes (20a to 20C) facing each substrate.
) are installed, and film thickness monitors (28a to 28C) are installed.
is installed. While monitoring the film formation rate on each substrate, it is possible to control the voltage applied to the electrodes facing each substrate.

Laser light oscillated by the laser source 1 is shaped into an optimal shape by a lens system, and is irradiated horizontally onto the substrate. The source gas is adjusted to a predetermined gas composition from the source gas adjustment device 26 in the countercurrent direction to the laser beam irradiation direction! ! It is supplied freshly. The gas pressure in the reaction chamber 7 is, for example, lXl0-~
Adjusted to lo'l'orr.

The substrates (12a to 12C) are heated to, for example, 200 to 450°C by heating means such as the heater 13.

Although this embodiment shows a case in which the laser beam is irradiated parallel to the substrate, the entire substrate may be directly irradiated with the laser beam using an optical system or the like. Furthermore, even when a plurality of energy beams are used, it is within the scope of the present invention to control the film formation rate by the gold applied voltage.

A case in which Al wiring is formed on a substrate will be described. Trimethyl aluminum (TMA) was used as the source gas, and an excimer laser was used as the laser. TMA
Using a laser beam having a wavelength of 1931 m (ArF) based on the ultraviolet absorption spectrum of , it was formed into a shape of 25 mm x 2 mm using a cylindrical lens, and was irradiated onto a position 2 mm above the substrate.

The distance between the substrate and the electrode was about 33 mm, and the pressure inside the reactor was maintained at I'l'orr. The substrate temperature was 250° C. and the applied voltage was 350V. In this case, the Al film formation rate on the substrate was 3.00 OA/min, which was more than double the film formation rate compared to a normal method in which no voltage was applied. In particular, the state of Al precipitation on the Al portions on the substrate was good, and the step coverage was far superior to that of ordinary sputtering methods.

Although this example shows the case where trimethylaluminum gas is used, the same effect can be obtained when using a mixed gas in which a predetermined amount of gas containing other elements such as Cu and 'l'i is added to TMA. can get.

When forming a metal thin film on a substrate, especially when forming a wiring metal film, in addition to A/, for example, Cu,
It is necessary to form a thin film of an alloy to which elements such as Ti are added. In such a case, a mixed gas of a gaseous organometallic compound, halide, metal carbonyl, etc. containing the metal to be deposited on the substrate is used as the source gas. In such a case, a plurality of laser beams having wavelengths matching the absorption characteristics of each source gas are mixed and irradiated.

The laser beam can be oscillated at an optimum wavelength by combining an excimer laser, a YAG laser, or the like with a dye laser.

By applying a voltage, the degree of concentration of surface charges differs between the insulating film portion and the metal portion on the substrate, and when forming a wiring metal film, the film formation rate at each portion differs. The surface charge is concentrated in the metal part, and the film formation rate in that part is high, which is effective for filling the interlayer connection hole with metal.

When a substrate is placed horizontally in a reaction chamber, an electrode is placed facing it, and a voltage is applied while irradiating an energy beam to form a film, the particulate nuclei generated in the gas phase by the energy beam will be attached to the electrode plate. The phenomenon of adhesion is also observed. In this case, there is a possibility that a mass of particle nuclei adhering to the t1 area may fall onto the substrate and contaminate the substrate. On the other hand, the same effect as the present invention can be obtained even if the substrate is installed vertically and electrodes are provided facing the substrate.

In the figure, 3 is a diffraction grating, and 10 is a gas inlet.

13 is a heating coil, 14.15 is a pair of electrodes connected to a high frequency power source, 16.18 is a laser, 30 is a film thickness measuring device, 32 is a substrate heating device, and 34 is an exhaust system.

〔Effect of the invention〕

According to the present invention, since it is possible to form a film while controlling the applied voltage, it is possible to achieve good step coverage, uniformity, and high-speed film formation.Furthermore, the film formation rate between substrates in the reaction chamber is constant. This increases throughput.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of one embodiment of the present invention, FIG. 2 is a schematic diagram of another embodiment of the invention, and FIG. 3 is a schematic diagram showing a prior art. 1...Laser, 7...Reaction chamber, 8...Incidence window, 1
1... Stage, 12... Semiconductor substrate, 13...
Heating coil, 20... Electrode, 21... Lens system, 22... High voltage application device, 24... High voltage control device, 26... Source gas adjustment device, 28... Film thickness monitor , 30... Film thickness measuring device, 32... Substrate heating device, 34... Exhaust system.

Claims (1)

[Claims] 1. Forming a desired thin film on the substrate by irradiating an energy beam that matches the absorption wavelength of the source gas while supplying a source gas containing the desired element to be deposited on the substrate. In the method, an electrode is provided facing the substrate, a voltage is applied between the substrate and the electrode, and the electric field strength or voltage application time between the substrate and the electrode is changed to control the thin film formation rate. Characteristic thin film formation method. 2. A thin film forming method according to claim 1, characterized in that the energy beam is irradiated between the substrate and the electrode. 3. The thin film forming method according to claim 1, wherein the substrate and the electrode facing the substrate are installed vertically. 4. In claim 1, the thin film is formed on the substrate using a laser beam as the energy beam and a gas containing a metal element such as Al, W, Cr, or Mo as the source gas. A thin film forming method characterized by: 5. Claim 1, characterized in that a wiring metal film is formed on the substrate using a plurality of mixed gases containing a gas containing Al and gases such as Cu and Ti as the raw material gas. Thin film formation method. 6. A thin film forming method according to claim 1, comprising forming a wiring metal film containing a desired metal element in an interlayer connection hole of a multilayer wiring structure.