JPH0499875A - Laser film forming device - Google Patents

Abstract

PURPOSE:To stably start the formation of a film by a laser beam with a low heat input at the time of thermally decomposing a gaseous organometallic compd. by a laser beam to form a film on a substrate by previously generating an electric discharge between a couple of discharge electrodes to decompose the gaseous compd. and depositing the product on the substrate with the decomposed metal as a nucleus. CONSTITUTION:A reaction vessel 7 in which a substrate 18 to be coated with a thin film is set, a light-transmissive window 12 for being incident a laser beam L in the range of visible or near IR radiation for irradiating and heating the substrate in the reaction vessel, an inlet hole 16 for introducing the gaseous organometallic compd. to be thermally decomposed by the laser beam in the reaction vessel toward the substrate 18 in the vessel and a couple of discharge electrodes 20 and 21 provided between the inlet hole and substrate, generating a discharge prior to the thermal decomposition of the gaseous organometallic compd. and decomposing the compd. are provided. The particulate acting as the nucleus in the film forming stage is formed at the area where a film of the metal and metallic compd. formed by the decomposition of the gaseous organometallic compd. by the discharge energy generated between the discharge electrodes begins to be formed, and a film is stably formed from the nucleus with a low heat input.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a laser film forming apparatus for thermally decomposing an organometallic gas to produce a metal film on a substrate.

(Prior Art) In a semiconductor manufacturing process, a thin metal film is formed between elements or patterns formed on the surface of an St substrate.

One known method for producing a metal film is to use laser light as a heat source, thermally decompose organometallic gas with the laser light, and deposit metal on a substrate.

As the organometallic gas, metal carbonyl (Cr(Co)
b, Mo (Co) 6, W (Co) b l are often used, and the laser used is a visible or near-infrared laser, for example, an argon ion laser (hereinafter abbreviated as Ar laser). There are many.

Examples of such prior art include J, Vac, Sci.

Technol, B, Vol. 5. No.2. Mar/A
pr 1987. That is, in this known document, a substrate on which a film is to be formed is placed in a reaction vessel.

Inside this reaction vessel, organometallic gases are N2 (nitrogen), Ar
(argon), N2 (hydrogen), and other carrier gases. A light-transmitting window is formed in the reaction container, and the laser beam focused through this window is made to enter the reaction container. Then, the laser beam is scanned to a location on the substrate where the film is to be formed, thereby forming the film on the substrate.

In that case, as shown in FIGS. 4 and 5, it is said that the film formation on the substrate a proceeds while forming a nucleation region C in front of the heating spot of the laser beam.

Even if the above substrate a is a glass substrate that is transparent to laser light and can hardly be expected to absorb laser light, it is possible to form a film by starting film formation on a pattern that can be heated. be.

The problem with such a film formation method is to improve the stability of film formation at the starting point. For example, when film formation is started from a Cr (chromium) film, there is almost no problem with its stability because the Cr film absorbs laser light relatively well. However, when film formation is started from a part, such as an i (aluminum) film, which has a high reflectance of laser light and good thermal conductivity, the film formation is often unstable.

The reason for this is that in order to form a film on AI, heating is difficult and relatively high power is required. The power level is nearly five times the power required to form a tungsten (W) film on a 5 in 2 surface. l
Once a film such as Cr, MOsW, etc. is formed thereon, the absorption rate of laser light is greatly improved by the presence of these films.

Therefore, an input of nearly five times the power will cause excessive heat input, which will damage the underlying Aρ film.

In order to prevent damage to the Aρ film, there is a method of feedback control of the laser output according to changes in the absorption rate of the film forming part, and a method of applying UV (ultraviolet) laser light to the starting point of film formation on the A and Q films in advance. Methods to facilitate film formation by forming a homogeneous film and using it as a nucleus during film formation, and improving absorption rate.
Possible methods include forming a film using V laser light.

However, according to the former method, it is difficult to select an information source for monitoring changes in absorption rate, and in the latter two methods, which use UV laser light, the photodissociation effect of UV laser light causes damage not only on the substrate. Because a film is formed on the window, it becomes difficult for UV laser light to pass through the window, making it impossible to stably irradiate the film-forming area of the glass substrate with UV light. Not an available method.

As a method to obtain the same effect as the method using UV laser light, the above-mentioned publicly known material states that W (CO) b is introduced into the reaction vessel and irradiated with a UV lamp for about 10 seconds, and this irradiation causes the glass substrate to be heated. It has been shown that it is possible to form a film even on a glass substrate where it is difficult to form a film only by irradiation and heating with laser light from an Ar laser.

According to such a method, it is possible to improve the film-forming property on a rise that is difficult to heat, such as the Aj) film, to the same extent as in the case of film-forming using UV laser light.

However, similarly to the method using UV laser light, the method using a UV lamp progresses film formation on the window due to the dissociation effect of the UV light from the lamp, and is not practical.

(Problems to be Solved by the Invention) As described above, in the conventional film formation method using laser light, when film formation is started from a location where laser light is difficult to absorb, the stability of film formation at that starting point is poor. That happened.

This invention was made based on the above circumstances, and its purpose is to stably start film formation even when starting film formation from a location that is difficult to absorb laser light. An object of the present invention is to provide a laser film forming method that enables the following.

[Structure of the Invention] (Means and Effects for Solving the Problems) In order to solve the above problems, the present invention provides a reaction vessel in which a substrate on which a thin film is formed is installed, and the above-mentioned A translucent window that allows visible or near-infrared laser light to enter the reaction vessel to irradiate and heat the substrate, and a translucent window that allows the organometallic gas to be thermally decomposed by the laser light to enter the reaction vessel. An introduction part is provided between the introduction part and the substrate to introduce the gas toward the substrate in the container, and a discharge is generated before the organic metal gas is thermally decomposed by the laser beam. It is characterized by comprising a pair of discharge electrodes that decompose gas.

According to such a configuration, when the organometallic gas is decomposed by the discharge energy generated between the pair of discharge electrodes, the metal and metal compound formed by the decomposition are used to form a film on the substrate at a location where film formation is to be started. If a film is formed using a pure metal with low heat input, the fine particles generated by sputtering during discharge can be used as impurities in the deposited film. Therefore, a highly pure film can be formed.

In addition, when an electrode with a dielectric layer formed on the surface is used as one of the discharge electrodes and an alternating current is applied between the two electrodes to form an ozonizer discharge, the high dissociation ability of the ozonizer discharge makes it difficult to use a normal glow discharge. It is possible to efficiently form a core substance even for organometallic gases that are difficult to dissociate.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. The laser film forming apparatus shown in FIG. 2 includes a laser device 1, such as an Ar laser, which oscillates laser light in the visible or near-infrared region. This laser device 1
The laser beam oscillated in the horizontal direction from the laser beam passes through the A,0 (acousto-optic element) shutter 2, and then is reflected in the vertical direction by the dichroic mirror 4. The laser light reflected by the dichroic mirror 4 is focused by the objective lens 5 and enters the reaction vessel 7 placed on the XY table as described below. The XY table 6 is controlled by a control section 9 via an interface 8, and the A and O shutters 2 are also controlled by control signals from the control section 9. A window 12 is formed in the wall 11 of the section. There is. This window 12 consists of a cylindrical body 14 that is hermetically fitted into a mounting hole 13 bored in the upper wall 11, and a transparent material such as glass or quartz that is hermetically fitted into the upper opening of this cylindrical body 14. It is formed from a transparent window member 15. Therefore, the laser light focused by the objective lens 5 is made to enter the reaction vessel 7 through the window member 15.

The cylindrical body 14 is formed with an introduction hole 16 as an introduction part, which has one end opened at its upper end surface and the other end opened at a midway part of the inner circumferential surface. This introduction hole 16 is connected to a gas supply source (not shown), from which the organometallic gas is introduced alone or together with a carrier gas. The organometallic gas introduced into the reaction vessel 6 through the introduction hole 16 flows toward the lower end opening of the cylindrical body 4, as shown by the arrow in FIG. At the inner bottom of the reaction vessel 7 below the lower end opening of the cylindrical body 14, a substrate 18 having, for example, an AN pattern 17 formed on its upper surface is installed. In addition, a second
As shown in the figure, an exhaust pipe] 9 is connected. This exhaust pipe 19 is connected to an exhaust pump (not shown), whereby the organic metal gas or carrier gas introduced into the reaction vessel 7 and thermally decomposed by laser light as described later is exhausted. There is.

A cathode 20 and an anode 21 are provided in the lower part of the circumferential wall of the cylindrical body 14 along the radial direction, with their tips facing each other and separated from each other. These cathode 20 and anode 21 are made of the same high-purity metal as the metal forming the thin film, and the switching element 2
3 to a DC high voltage power supply 24. A capacitor 25 is connected in parallel to this DC high voltage power supply 24 .

A control pulse P for controlling on/off of the switching element 23 is inputted from a discharge control section (not shown). When the switching element 23 becomes conductive, corona discharge is ignited between the cathode 20 and the anode 21 due to the charge stored in the capacitor 25. This corona discharge is pulsed, but the capacitor 25
It can be discharged repeatedly by charging.

Next, the All pattern 17 on the substrate 18 is coated with, for example, W (tungsten) using the laser film forming apparatus having the above configuration.
The case of producing a thin film will be described with reference to FIGS. 3(a) to 3(c). First, the substrate 18 is placed inside the reaction container 7.
Once the substrate 18 is installed, the XY child table is controlled and moved so that the portion of the substrate 18 where the film is to be formed is irradiated with the laser light that passes through the window 12.

In this state, when a mixed gas M containing W(Co)6 as an organic metal gas and H2 gas as a carrier gas is supplied into the reaction vessel 7 from the introduction hole 16, a pulse signal P is sent to the switching element 23. input, and this switching element 23 is brought into conduction. As a result, the charges accumulated in the capacitor 25 flow to the cathode 2o and the anode 21 as shown in FIG. 3(a), and corona discharge is ignited between them, so that the discharge energy causes W ( Co) 6
is decomposed. Since the W generated by the decomposition is transferred toward the substrate 18 along with the flow of the mixed gas shown by the arrow M in FIG.
And a nucleus 31 of the W compound is formed.

Once the nucleus 31 is formed on the All pattern 17 in this manner, the laser device 1 is operated to oscillate laser light. This laser light is focused by the objective lens 5,
When W(Co)6 passes through the window member 15 of the window 12 and enters the reaction vessel 7, the heat of this laser light decomposes W(Co)6, and the W generated by the decomposition causes the W(Co)6 to decompose as shown in FIG. 3(b). A W film 32 is produced on the Aj7 pattern 17. Therefore, by moving the substrate 18 using the XY child table, the W wiring 33 can be formed as shown in FIG. 3(c).

That is, according to the laser film forming apparatus having the above configuration, the AΩ pattern 17 is formed by discharge prior to film formation by laser light.
Since a nucleus 31 of W and a W compound is formed on the surface in advance, the generation of the W film 32 can be stably started from the position of the nucleus 31. Moreover, even when forming a film on the Aρ pattern 17, which is difficult to heat and easily damaged due to its low melting point, the core 31 can be formed in advance without increasing the power of the laser beam. , it becomes possible to form a film.

In addition, since the flow direction of W (C, O) 6 is set in one direction from the window 12 toward the substrate 18, the nuclei 31 generated by the discharge are reliably transferred toward the substrate 18, and
It does not adhere to the window member 15. Therefore, since the film is not deposited on the window member 15, the power of the laser light entering the reaction vessel 7 is stabilized, and not only can the film be uniformly deposited, but also the window member 15 can be cleaned. is also no longer necessary.

FIG. 6 shows the configuration of the apparatus when ozonizer discharge is used as the discharge. Ozonizer discharge has a high electron temperature and a high dissociation ability. Generally, this can be caused by interposing a dielectric layer in the discharge path and applying alternating current.

Therefore, in the configuration shown in FIG. 6, the pair of electrodes 31, 32
This is achieved by forming a dielectric layer 33 on the surface of one of the electrodes 32 and connecting these electrodes 31 and 32 to an AC power source 34 via a switching element 23. This method is an effective method for dissociating organometallic gases that have high binding energy and are difficult to dissociate using corona discharge or glow discharge.

Note that this invention is not limited to the above-mentioned embodiment, and can be modified in various ways. For example, in the above embodiment, the organometallic gas is supplied into the reaction vessel together with the carrier gas, but the organometallic gas may be depressurized and directly introduced into the reaction vessel. In that case, the same effect can be obtained even if the discharge ignited between the electrodes is a glow discharge.

In addition, the laser device is not limited to Ar laser, but also YA laser.
It may be a G laser or the like, and in short, any laser device that can oscillate laser light in the visible or near-infrared region may be used.

[Effects of the Invention] As described above, the present invention provides the following effects when forming a film on a substrate.
Before thermally decomposing the organometallic gas with a laser beam, a discharge is ignited between a pair of discharge electrodes, the discharge energy decomposes the organometallic gas, and the decomposed metal is attached to the substrate as a core. Therefore, film formation using laser light can be stably started from the core with low heat input.

Therefore, even if the starting point of film formation is difficult to heat, such as an AΩ pattern, and has a low melting point and is easily damaged, film formation can be reliably started using a low-power laser beam. Furthermore, since the organometallic gas is made to flow toward the substrate from the inlet, it is possible to prevent the core metal separated by the discharge from adhering to the window into which the laser light is incident.

This stabilizes the power of the laser light that enters through the window, allowing stable film formation.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of a part of a reaction vessel showing an embodiment of the present invention, FIG. 2 is a block diagram of the entire apparatus, and FIG.
a) to (c) are explanatory diagrams sequentially showing the process of film formation, Fig. 4 is an explanatory diagram of the general starting point of film formation, and Fig. 5 is 2 of Fig. 4.
FIG. 6 is a block diagram of an apparatus showing another embodiment of the present invention. It is. 7...Reaction container, 16...Introduction hole (introduction part) 18.
... Substrate, 20... Cathode, 21... Anode. Applicant's agent Patent attorney Takehiko Suzue

Claims (3)

[Claims] (1) A reaction vessel in which a substrate on which a thin film is to be formed is installed, and a transparent transducer installed in the reaction vessel that allows visible or near-infrared laser light to enter the reaction vessel to irradiate and heat the substrate. an optical window, an introduction part provided in the reaction vessel and for introducing an organometallic gas to be thermally decomposed by the laser beam toward the substrate in the reaction vessel, and between the introduction part and the substrate; A laser film forming apparatus comprising: a pair of discharge electrodes which generate a discharge prior to thermal decomposition of the organometallic gas by the laser beam, and decompose the organometallic gas with the discharge energy. (2) The laser film forming apparatus according to claim 1, wherein the pair of discharge electrodes is made of the same high purity metal as the metal forming the thin film. (3) One of the pair of electrodes is a metal electrode with a dielectric layer formed on the surface thereof, and an ozonizer discharge is formed by applying an alternating current between the pair of electrodes. 1) The laser film forming apparatus according to item 1).