JPH0419701B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a thin film manufacturing method and an apparatus thereof, and more particularly, the present invention relates to a thin film manufacturing method and an apparatus thereof, and more particularly, to a substrate surface instantaneously heated by a laser beam, and a space in contact with the surface. A method for forming a thin film of a thermal decomposition product of a reactive gaseous substance existing in a substrate, especially various optical interference color films having an ultra-uniform film thickness of an integral multiple of the wavelength of light over the entire film-forming surface. Regarding the device.

[Conventional technology]

Conventionally, when producing a thin film on the surface of a substrate by a chemical reaction, the substrate is heated, or the entire reaction chamber containing the substrate is heated, and the reactive gas around the substrate is thermally decomposed to produce thermal decomposition products. A thin film was formed on the substrate.

[Problem to be solved by the invention]

However, in such conventional thin film formation methods,
Since the entire space around the substrate is at a high temperature, the thermal decomposition products of the reactive gas may further undergo secondary or tertiary thermal decomposition, or the thermal decomposition products may react with the undecomposed reactive gas. There was a problem in that pits of various sizes were generated in the thin film formed by this method.

In addition, since the substrate is heated strongly, the substrate may become distorted.
Disadvantages that cause a lot of damage to both the formed thin film and the substrate, such as warping, elongation, shrinkage, etc., which cause loss of dimensional accuracy due to heating, deterioration of the structure of the substrate itself, and changes in the functional structure already formed on the substrate. It was hot.

Further, the same drawbacks as described above cannot be avoided even when forming thin films by physical methods under vacuum such as vacuum evaporation, sputtering, and ion plating.

Therefore, the present invention was made to eliminate such conventional drawbacks, and it is possible to instantaneously heat only the surface of the substrate irradiated with the laser beam, inducing a thermal decomposition reaction limited only to the heated surface. Therefore, ideal "low-temperature surface reactions" are possible, and a thin film with a high quality and ultra-uniform thickness, which was previously unobtainable, can be obtained, and the functional structure of the substrate can be changed. It has the following features:

[Means to solve the problem]

That is, in the thin film manufacturing method of the present invention, a laser beam is used to sweep a substrate placed under a uniform plate-like airflow of a reactive gas to heat the substrate, and a space in contact with the heated substrate surface is heated. The method is characterized in that the reactive gaseous substance present is thermally decomposed to form a thin film having a uniform thickness of a thermal decomposition product of the reactive gaseous substance on the surface of the substrate.

Further, the thin film manufacturing apparatus of the present invention includes a substrate, a plate-shaped airflow forming means having a slit nozzle that supplies a uniform plate-shaped airflow of a reactive gas onto the substrate,
a pair of sweeping mirrors positioned on the substrate for directing a laser beam from a laser oscillator through the stream of reactive gaseous material onto the substrate, the pair of sweeping mirrors being perpendicular to each other; The present invention is characterized in that the laser beam vibrates in the direction to give the laser beam a motion that sweeps the substrate.

The method of the present invention is a method in which only the laser beam is swept by operating a mirror (laser beam reflecting mirror), and is also referred to as a mirror sweep method.

Furthermore, since the method of the present invention sweeps the substrate with a laser beam, it is also called a beam sweep method.

What is important in such a beam sweeping method is to irradiate the substrate with a laser beam having a wavelength (λ _L ) that matches the specific absorption wavelength (λ _S ) of the substrate.

Normally, the laser beam is reflected, transmitted, and
However, the laser beam is absorbed by the substrate only when λ _S and λ _L match. The larger the absorption coefficient (α) of the substrate, the more the laser beam that penetrates into the substrate is absorbed closer to the surface of the substrate, usually within 10 μm, and converted into heating energy.
Instantaneous surface layer heating occurs, typically heating the substrate surface to 500°C to 600°C.

Here, the absorption coefficient (α) of the substrate refers to the "speed at which light is absorbed" or "easiness of light absorption" of the substrate.
This means that the larger the value of α, the better the light absorption even by a thin substrate, and the less transmitted light.

Then, the light incident on the substrate is absorbed and attenuated according to the following equation.

I(x)=I ₀ e ^- 〓 ^x However, I(x): Intensity of light that has traveled the distance x from the substrate surface.

I ₀ : Intensity of incident light on the substrate surface.

α: extinction coefficient.

x: distance from the surface.

Usually, the extinction coefficient α is about 10 ⁶ cm ^-1 . Therefore, the intensity of light drops to about 0.01 at x=10 ^-4 cm, that is, 10 μm from the surface. In other words, 99% of it is absorbed.

In the present invention, a substrate placed under a plate-like airflow of a reactive gas as described above is swept with a laser beam.

FIG. 1 is a partial explanatory diagram showing an embodiment of a thin film manufacturing apparatus used in the mirror sweeping method of the present invention, in which a laser beam generated from a laser oscillator is reflected by a reflecting mirror 1 toward a substrate 3. This reflected beam is successively reflected by a pair of sweeping mirrors, an X mirror 4 and a Y mirror 5, which have mounting axes facing each other and perpendicular to each other at a lower position, and reaches the bottom substrate surface. . These sweep mirrors are vibrated in advance at appropriate speeds in appropriate rotation angle ranges around the mirror mounting axis. Therefore, the X mirror 4, which first receives the reflected beam, draws a straight line of the beam on the opposing Y mirror 5 surface, creating a linear light source that irradiates the substrate 3 placed below. Since the Y mirror 5 vibrates at a constant rotation angle, it uniformly sweeps the entire substrate surface by reciprocating linear irradiation on the substrate surface.

The reactive gas existing in the space in contact with the substrate 3 is instantaneously thermally decomposed, and a thin film of thermal decomposition products is deposited at the beam passage point A. The thickness of the film material on this A changes depending on the passing speed of the beam,
As the passage rate increases, the membrane material deposition rate decreases.

Therefore, in order to keep the thickness of the deposited film constant, the beam energy must be increased as the passing speed of the sweeping laser beam increases.

By the way, according to the inventors' study results, the beam energy E (watts) and the beam movement speed u
(cm/sec) was found to have the following relationship.

Eu4/5 That is, it can be seen that in order to form a uniform film surface over the entire substrate surface, it is necessary to always keep the beam moving speed constant at a given laser beam energy.

On the other hand, since the laser beam sweeps the substrate surface by the rotational vibration of the X mirror 4 and the Y mirror 5, the speed of the beam changes between the center and the periphery of the substrate, causing uneven heating.

Therefore, the vibration angle of the mirrors 4 and 5 is suppressed to within ±20°, and the change in the moving speed of the beam on the substrate is suppressed to within 3%.

As a result, for example, if the mounting height of the sweep mirrors 4 and 5 is 2 m, a uniform film can be produced on a large substrate of 1.5 m x 1.5 m. The size of the sweep mirrors 4 and 5 is preferably three times or more the beam diameter.

Furthermore, it is necessary to select the frequencies of the X mirrors 4 and 5 at an appropriate ratio. If this ratio is too large or too small, the heating on the substrate will be striped, and the surface of the formed film will also be striped.

According to the study results of the inventors, when forming a uniform film surface on a substrate surface of lcm x lcm using a laser beam with a diameter of dcm, the frequency fx (Hz) of the X mirror and the frequency fy (fy) of the Y mirror are Hz) ratio (σ) is given by the following equation from the experimental results.

σ=fz/fy=al/d where a is a flattening coefficient, and when a=2, the striped pattern disappears and a uniform film surface is obtained. Usually 2<a<
The range is 20.

The laser irradiation conditions essential for heating have been described in detail above, but at the same time, in order to form a uniform film layer, it is absolutely necessary to achieve a uniform distribution of reactive gaseous substances on the substrate.

In particular, this is essential when the film thickness has ultra-uniformity over the entire area of the film formation surface and is an integral multiple of the wavelength of light, and it is possible to form various light interference color films.

Therefore, in the present invention, a special method has been taken to address this point as an important element of the invention configuration. That is, a thin plate-shaped uniform airflow 6 of reactive gaseous material is created, and it is flowed in parallel at a height of 5 to 20 mm without touching the surface of the substrate 3, and is directed from the bottom of this flat airflow toward the substrate surface. A reactive gaseous substance is fed downward to create a uniform concentration distribution. This uniform thin plate-like airflow 6 flows into the nozzle chamber 7.
Occurs due to This nozzle chamber 7 has a long strip-shaped spray plate 8 on the front surface. Figure 2 shows the injection plate 8.
Show details.

That is, slit nozzles 9 in the form of narrow grooves are dug in the injection plate 8, and fumarole holes 10 reaching into the nozzle chamber are placed at regular intervals on the bottom surface of the slit nozzles 9.

In order to obtain the thin plate-like airflow 6 of the required thickness, the necessary number of slit nozzles 9 are arranged vertically. In order to make the concentration distribution of the air flow 6 uniform, the depth of the slit nozzle 9 should be set to Z ₂ and the length of the injection hole 10 should be set to Z ₁
In this case, it is preferable that Z ₂ ≧Z ₁ ≧5 mm.

Further, it is preferable that the width W of the slit nozzle 9 and the diameter Q of the injection hole 10 satisfy W<1 mm, Q<1 mm, and W≧Q. Generally, W and Q are as small as possible, and the higher the gas pressure inside the nozzle, the more uniform the thin plate airflow 6 can be obtained. The width of the thin plate-like airflow 6 is determined by the length of the slit, and can easily be made to have a width of 1 m or more. The length of the air stream 6 can also be increased by increasing the pressure within the slit nozzle.

The thickness of the thin plate airflow 6 is suitably 5 to 50 mm. Further, the speed of the airflow is within the range of several to several tens of m/sec.

In other words, the mirror sweep method generates a uniform thin plate-shaped reactive gas flow that covers the substrate surface, and uses this in conjunction with a substrate heating beam driven by a vibrating mirror to create an ultra-uniform film surface on any substrate. will be formed.

Therefore, this mirror sweeping method is suitable for film surface coating or pattern coating on a stationary substrate, a substrate that moves intermittently.

In particular, when producing fine patterns, by focusing the beam using an optical system,
Alternatively, it is also possible to form a highly precise film surface with a line width smaller than that. In addition, the film deposition rate is 500 Å/sec or more,
A film thickness of several μm can be achieved in a short time.

As the substrate used in the present invention, all substrates used in conventional thin film forming methods can be used, such as glass plates, metal plates, quartz plates,
Examples include ceramic plates.

A reactive gaseous substance is a gaseous substance that is thermally decomposed very quickly when it comes into contact with the heated substrate surface, that is, a gaseous or fume-like thermally decomposable raw material, and the thermal decomposition products are generated on the substrate surface. A clean thin film is formed.

The laser used may be continuous wave or pulse wave as long as it has an output of several tens of mW or more.

Preferably, the laser beam has a large heat-generating effect when irradiated onto the substrate, in other words, the substrate efficiently absorbs the laser beam. Therefore, an optimal combination exists between the substrate and the laser beam.

For example, for Si substrates, Ar laser (wavelength 0.48 μm), krypton laser (0.53 μm), and ruby laser (0.69 μm) are used, and for ceramics and glass, YAG laser (1.06 μm), HF/DF
Chemical lasers (2.5-4.06 μm) and _CO2 lasers (10.6 μm) are utilized. The greatest advantage of the present invention is its versatility in that, like conventional high temperature chemical vapor deposition methods, any reactive chemical can be used as a reactive gaseous source.

Therefore, the thin film materials that can be manufactured are extremely wide-ranging. For example, metals such as Al, Si, Cr, Ni, Cd, Fe, MoSi ₂ , WSi ₂ , TaSi ₂ , PtSi ₂ , NbSi ₂ ,
NiCr, SnCu, ZnCu, InSb, CaSb, LaG,
Alloys such as NbNi, Nb ₃ Al, NbSn, BiTe, etc.
Compound materials include SiO ₂ , Al ₃ O ₃ , TiO ₂ , ZrO ₂ ,
Oxides such as SnO ₂ , In ₂ O ₃ , Fe ₂ O ₃ , SiC, TiC,
B ₄ C, WC, VC, carbides such as ZrC, TiN, BN,
Nitrides such as AlN, Tan, Si ₃ N ₄ , CrW, VN, etc.
_{Almost all electronic and _}
Covers surface and functional membrane materials for information, energy machinery, and chemical industries.

Examples of the present invention will be described below.

〔Example〕

Figure 3 shows SnO ₂ in the atmosphere using the mirror sweep method.
An overview of the equipment used to fabricate the membrane is shown. A CO ₂ laser 32 and a beam sweep device 33 are installed on a triaxial movable rail combination mount 31, and a sample substrate 3 is
A laser beam was projected onto the surface of 6. The beam sweeping device 33 includes a beam reflecting mirror 37 (corresponding to 1 in FIG. 1) and X and Y sweeping mirrors (4 and 5 in FIG. 1), and redirects the horizontally incident beam downward. At the same time, two-dimensional vibration was applied to this beam to uniformly sweep and heat the sample substrate surface 36.

The maximum output of the laser beam is 55 watts, and the beam diameter is 6 mmφ. The diameter of the reflecting mirror 37 of the beam sweeping device 33 is 30 mmφ, and the X mirror (4 in Figure 1)
The dimensions of the and Y mirror (5 in Figure 1) are
The size is 30mm x 20mm, and the mirror-polished stainless steel surface is plated with gold. The distance between the CO ₂ laser beam 32 and the beam sweep device 33 is approximately 1 m, and the beam sweep device 33
The distance between the lower end of the sample table 38 and the sample stage 38 is approximately 70 cm.

The plate-shaped airflow CVD device 34 has a metal rectangular nozzle chamber (150 mm x 40 mm x 30 mm) 39 and an exhaust device (intake opening 150 mm x 150 mm) 40 facing each other across a sample stand (150 mm x 150 mm) 38 attached to a mount. It was then deployed. In the injection plate of the nozzle chamber 39 (8 in Fig. 1 and Fig. 2), three injection grooves with a width of 1 mm and a length of 100 mm were dug at intervals of 3 mm, and blowholes were opened at regular intervals in the bottom of the grooves. Ta. Furthermore, a reaction gas generator 42 incorporating an evaporator 41 and a laser beam component gas source is provided.
was provided to supply reactive raw material gas to the nozzle chamber 39.

First, the evaporator 41 was filled with volatile organometallic tin ((CH ₃ ) ₂ SnCl ₂ ) to generate steam at about 100°C.

Next, a pirate board (50 mm
x 50 mm x 91 mm) was placed on the sample stage 38, and a stream of reactive gaseous material containing vapor of (CH ₃ ) ₂ Snl ₂ was injected from the nozzle chamber 39. The speed of the airflow is approximately 3m/
sec, the composition of the airflow is Ar3/min, O ₂ 3/min,
(CH ₃ ) ₂ SnCl ₂ saturation Ar was 0.5/min. The airflow has a plate shape with a width of about 100 mm and a thickness of about 10 mm, and covers the surface of the Pyrex plate 36 on the sample stage, passing through it at a height of about 10 mm without touching it.

When irradiation with the laser beam started, a continuous film surface appeared as the beam swept. The beam output at this time is approximately 45 watts, X mirror (4 in Figure 1)
The frequency of the vibration was fx = 2Hz, the frequency of the Y mirror (5 in Figure 1) was fy = 0.02Hz, and the mirror vibration ratio σ = 100. The film surface deposition time was 2 minutes, the film thickness was approximately 1000Å,
The entire surface exhibited a single golden interference color and a light transmittance of over 90%. Further, no thermal damage such as deformation of the Pyrex board due to irradiation occurred. Thus,
It was confirmed that a high-quality film surface could be formed at a low substrate temperature.

Furthermore, under the same beam irradiation conditions, the film thickness was increased to 3000 Å (first-order green interference color) and 5300 Å by sequentially increasing the concentration of the reactive gaseous substance ((CH ₃ ) ₂ SnCl ₂ ).
It was possible to increase the color to Å (tertiary red). Figure 4 shows beam outputs of 40 watt and 50 watt, bead diameter of 6 mm, mirror frequency fx = 5 x 10 ^-1 Hz,
The growth characteristics of SnO ₂ film with respect to time on a Pyrex substrate of 50 × 50 mm ² when fy = 3.3 × 10 ^-3 Hz are illustrated.

〔Effect of the invention〕

As described above, according to the present invention, obvious effects not found in the prior art can be achieved.

That is, only the very surface layer of the substrate is heated to a high temperature by the sweeping irradiation of the laser beam until a chemical change is caused. The thickness of the surface heating layer is within 10 μm. Therefore, the temperature of the substrate itself does not rise, high-temperature reactions occur only in the surface layer, and the substrate is cooled in a short time. In other words, the temperature of the thin film manufacturing process has been reduced.

Therefore, there are almost no secondary or tertiary decomposition reactions or side reactions, unlike in conventional thin film manufacturing methods in which the entire substrate or the entire substrate and surrounding raw material gas is heated. , it is possible to preferentially carry out only the desired thin film forming reaction. The produced film is of high quality and has excellent adhesion, which is characteristic of a film produced by a high-temperature reaction.

Further, according to the present invention, a uniform plate-shaped airflow is formed by the plate-shaped airflow forming means having a slit nozzle, and the uniform plate-shaped airflow of the reactive gas is supplied onto the substrate.

Therefore, over the entire area of film formation on the substrate,
It is possible to form various optical interference color film surfaces with ultra-uniform film thicknesses having a uniform film thickness that is an integral multiple of the wavelength of light. In other words, these uniform film surfaces have a film thickness of 400~
Silvery white at 500Å, gold at ~1000Å, ~1500
Purple at Å, yellow at ~2200Å, pink at ~2900Å, yellow at ~3500Å, red at ~4000Å, ~4600
It exhibits a green interference color in Å, and has excellent controllability and reproducibility of film thickness.

Furthermore, when fabricating an oxide film according to the present invention, there is the advantage that it can be carried out in the atmosphere. Moreover, it is also possible to continuously manufacture large-area membrane surfaces. When the reactive thin plate gas flow is stabilized or a special gas atmosphere or reduced pressure or vacuum is required, the process can also be carried out in a closed room or a persier.

Note that the laser beam is introduced into the sealed chamber through a window provided in the wall of the chamber. A crystal material with high transmittance to the laser beam is used as the window material.
Crystal plates that can be used whether the laser beam wavelength is in the infrared or visible range include ZnSe,
Examples include MgF ₂ , LiF, CaF ₂ , NaCl, KCl, KBr and the like. In particular, SiO ₂ , LiF, MgF ₂ and the like exhibit good performance in the visible range.

[Brief explanation of drawings]

FIG. 1 is a partial explanatory diagram showing an embodiment of the thin film manufacturing apparatus according to the present invention, FIG. 2 is an explanatory diagram of the waist part thereof, and FIG.
The figure is a schematic diagram showing another embodiment of the thin film manufacturing apparatus of the present invention, and FIG. 4 is a diagram showing the relationship between time and SnO ₂ film thickness in the mirror sweep method of the present invention. 2... Laser oscillator, 3... Substrate, 4, 5...
Sweeping mirror, 6...Plate air flow of reactive gaseous substance,
9...Slit nozzle.

Claims (1)

[Claims] 1. A laser beam sweeps a substrate placed under a uniform plate-like airflow of a reactive gas to heat the substrate, and the reaction existing in the space in contact with the heated substrate surface is heated. 1. A method for producing a thin film, comprising the step of thermally decomposing a reactive gaseous substance to form a thin film having a uniform thickness of a thermal decomposition product of the reactive gaseous substance on the surface of the substrate. 2. A substrate, a plate-shaped airflow forming means having a slit nozzle that supplies a uniform plate-shaped airflow of a reactive gaseous substance onto the substrate, and a plate-shaped airflow forming means having a slit nozzle that supplies a uniform plate-shaped airflow of a reactive gaseous substance onto the substrate, and a plate-shaped airflow forming means that passes a laser beam from a laser oscillator through the airflow of the reactive gaseous substance. a pair of sweep mirrors located on the substrate for guiding the laser beam onto the substrate, and the pair of sweep mirrors vibrate at right angles to each other to give the laser beam a motion to sweep the substrate. Features of thin film manufacturing equipment.