JPH06122598A - Production of deposited thin film - Google Patents

Abstract

PURPOSE:To obtain a deposited thin film improved in film design and physical properties by irradiating a specific target with short-pulse energy beams. CONSTITUTION:Firstly, a target 6 containing (A) a metal capable of forming a stable compound surface through reaction with the air or a gas in the form of a vapor atmosphere and (B) another metallic element is placed on a target holder 7. Then, short-pulse energy beams 11 from an excimer laser generator 1 is introduced, via the condensing lens 4 and aperture in an optical box 2, into a vacuum chamber 3 and irradiated on the target 6 being in revolution to locally heat it for a short time and evaporated the surface of the target 6, and the resulting evaporated material is deposited on a substrate 8 placed on a substrate holder 9, thus affording the objective thin film.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a vapor-deposited thin film. More specifically, the present invention relates to a method of irradiating a raw material target with a short-pulse electromagnetic wave to evaporate it and deposit a ceramic thin film on a predetermined substrate.

[0002]

2. Description of the Related Art In recent years, the application of high-power lasers to the production of ceramic compound thin films has been actively researched and developed. As a method for producing this thin film, for example, a method known as a laser vapor deposition method (for example, JP-A-2-1768) is used.
No. 5, Applied Physics Letters Vol. 51 No. 11
Pp. 861-863), and its application to the preparation of oxide superconductor thin films, which has been actively studied since 1987, is being studied.

One of the major characteristics of the laser vapor deposition method is that the atmosphere around the substrate can be freely selected. Due to this characteristic, not only oxide superconductors but also many other ceramics such as metal elements can be used. Nitrogen, phosphorus, oxygen, fluorine,
It is considered to be useful for forming a thin film of a compound with a low boiling point element such as chlorine, bromine or iodine. In fact, the research on the production of oxide superconductor thin films by the laser deposition method is stimulated, and the laser deposition method is being applied to the production of thin films of oxides and chalcogenides other than oxide superconductors.

Under this laser vapor deposition method, particularly the condition called laser ablation, the target material is evaporated by irradiating the target with a laser pulse having a large energy density, and a thin film having a composition close to the target composition is formed on the substrate. Is believed to be an advantage. FIG. 1 is a schematic diagram showing an example of a laser vapor deposition apparatus. The laser vapor deposition method will be described while explaining the laser vapor deposition apparatus with reference to FIG.

Ultraviolet light 11 from the excimer laser generator 1 enters the vacuum chamber 3 through the nitrogen-purged optical box 2 and the window 5 of the vacuum chamber 3. As this laser, for example, another high-power laser such as a YAG laser may be used. UV light 11 is optical box 2
The light is condensed in front of the target by the condenser lens 4 inside and is irradiated onto the target 6. Normally, synthetic quartz is used as the material of the condenser lens 4, and 1 is used as the window material of the vacuum chamber 3.
A material having a thickness sufficient to support the pressure difference of atmospheric pressure and capable of transmitting the ultraviolet light 11, for example, artificial quartz single crystal, M
gF ₂ single crystal, sapphire or the like is used.

The light applied to the target 6 locally heats the target surface for a short time. For example, the excimer laser generally has a pulse width of 10 to 30 nsec.
Upon receiving this heating, evaporation starts from the target surface. This vaporized substance is discharged toward the substrate 8 arranged so as to face the target 6 and is deposited on the substrate. The target 6 is preferably rotatable by a target holder 7 supporting the target 6, and in some cases, a plurality of targets may be arranged in the target holder 7 so that each target can be rotated, and the positions of the targets can be exchanged. It may have a function. Further, it is preferable that the substrate holder 9 for holding the substrate 8 is also rotatable,
It has a substrate heating means. When a thin film is actually produced, for example, when an oxide thin film is produced, an oxidizing gas such as oxygen is supplied to the vacuum chamber 3 through the gas inlet 12.

It has been reported that such a laser deposition method can provide extremely good electrical characteristics, such as extremely high superconducting transition temperature and critical current density. Laser vapor deposition method, especially under the condition called laser ablation, because it is considered that the greatest advantage is that a thin film having a composition close to that of the target can be obtained by using a target composed of a plurality of metal elements and a low boiling point element as a target. It is most common to use a target having a composition close to that of the target thin film.

For example, when an oxide is produced, a laser-irradiated vapor-deposited film has been produced by targeting an oxide sintered body having a composition close to the intended thin film in an atmosphere gas such as oxygen.

[0009]

However, in the method of using such an oxide sintered body as a target, the target deteriorates over time due to laser irradiation and gradually produces grains on the thin film, and the surface shape of the target changes. There is a problem that the vapor deposition rate varies.

[0010]

Means for Solving the Problems As a cause of the generation of grains, the present inventor has found that a composite oxide such as an oxide superconductor is decomposed and segregated by laser irradiation, and is easily melted or evaporated easily. Focusing on the fact that the part that is difficult to melt or evaporate becomes non-uniform, and the liquid or solid component mixes with the evaporating component to evaporate, and as a result of investigating sequential or simultaneous vapor deposition of a target that is as uniform and simple as possible By improving the conventional laser deposition method that uses a target composed of multiple elements, and sequentially or simultaneously irradiating the target composed of a single metal element with a laser, a thin film composed of multiple target elements can be produced. I found that I could do it. Furthermore, we examined the laser deposition method by changing the conditions of laser deposition and the manufacturing method of the target, and when the metal itself was the target, the surface shape of the target changed due to laser irradiation compared to ceramics in the case of a metal whose surface is chemically stable. It has been found that it is difficult, that is, no grains are formed on the thin film and the deposition rate is constant. As a result, the problem of particle generation, which is a drawback of the laser deposition method, can be solved, and a ceramic thin film excellent in both film shape and physical properties and useful for electronic devices can be provided.

The gist of the present invention is to provide a method for producing a thin film of a ceramic compound containing two or more kinds of metal elements on a substrate by vapor deposition, in which a metal that reacts with the atmosphere or vapor deposition atmosphere gas to form a stable compound surface. And a target containing another metal element are sequentially or simultaneously irradiated with a short pulsed energy beam to deposit a ceramic compound thin film.

As the metal target of the present invention, it is necessary that the surface of the metal target is stable in the atmosphere and the vapor deposition atmosphere. This often means that a stable oxide of the metal needs to be present, especially when making oxide thin films. Pure metals such as barium, strontium, and calcium (especially purity 99.9%
The above) have extremely high chemical activity, and since these oxides are unstable and the metal surface is also unstable, they are not suitable for this method. In addition, the thermal conductivity is preferably about 0.3 W / cm · deg so that the laser deposition can be performed at a practical speed. Further, a metal oxide having a high melting point is preferable in order to stabilize the surface due to the formation of the metal oxide on the surface of the metal target.

From the above points, particularly preferable metals are as follows. That is, the thermal conductivity of rare earth metals including scandium and yttrium (europium, gadolinium, samarium, ytterbium, etc.) is 0.15 W / cm.
-The thermal conductivity of titanium, zirconium, and hafnium is about 0.2 W / cm-deg, and that of manganese is about deg.
It is 1 W / cm · deg or less, and any of these can be laser-deposited at a sufficient rate, and a stable target surface can be obtained even after the vapor deposition. Also, lead, bismuth, etc., have a thermal conductivity of about 0.3 W / cm · deg or less,
Practical laser vapor deposition is possible.

Further, in order to reduce the thermal conductivity of the target, the target is made sufficiently thin (0.1 m).
m or less), an amorphous state, or controlled introduction of grain boundaries or defects, or means for thermally insulating the target may be provided in the target holder or in the vicinity thereof. The target ceramic compound thin film containing two or more kinds of metal elements is formed by irradiating the target of the above metal and the target containing another metal element sequentially or simultaneously. Targets containing other metal elements include other types of metal targets of the above metals,
A target such as an alloy target or a metal oxide target can be used.

As the component gas, for example, an oxide is formed.
If you do, O₂, O₃, O, NO₂, N₂Used by O etc.
If it is a sulfur compound, S, S_2n(N = 1 to 4),
SF ₆Etc. are used, and if nitride, N₂, NH₃, N
Can be used. In the target of the method of the present invention
Since the above component gas that is a low boiling point element does not enter in,
It is necessary to activate the gas more than under normal conditions.
This includes activation by a high frequency electric field (RF) and a direct current electric field.
Gas (activity such as radicals, monatoms such as oxygen atoms, ozone, etc.)
Of various molecules), and
There is a method of forming a ring or the like.

Examples of the short pulsed energy beam used include electromagnetic waves such as laser beams and electron beams, and usually laser beams are used. The wavelength of the laser light need not be ultraviolet light as long as it can be absorbed by the target, but generally light from 190 nm to 350 nm is easily absorbed by many substances, and a laser with a large output per pulse is easily obtained. .

As a source of such a laser, an excimer laser, a YAG laser combined with a non-linear optical element to shorten the wavelength, an Ar ion laser, a carbon dioxide gas laser or the like is used. Particularly, a combination of an excimer laser and a YAG laser with a non-linear optical element is most preferable. Laser power is 10 per pulse
About 1000 mJ is preferable, and more important is the energy density on the target, which is 0.01 to 10 J / cm.
² , generally about 1 J / cm ² . This pulse width is usually about 10 to 100 nsec.

An electron element for which it is effective to use the method of the present invention
As a ceramic compound thin film for a child, copper oxide superconductivity
The body and its analogues, eg LnBa₂(Cu_1-xTm_x)₃
O₇, (Ln_1-yMy)₂(Cu_1-xTm_x) O_Four , Bi₂Sr
₂(Ca_1-yLn_y)_n-1(Cu_1-xTm_x)_nO_{2n + 4}(Where L is
n represents a rare earth element such as Y, Sm, Eu, Gd, and Yb.
, M represents Ba, Sr, Ca or Ce, and Tm is copper
Other than transition metals, especially 3d metal elements such as Fe, Ni, Co
Represents a prime. ), An oxide magnetic material such as LnTmO ₃ , Rare
Soil garnet oxide, orthoferrite, dielectric, eg
BaTiO₃ , SrTiO₃ , PLZT [(Pb, L
a) (Ti, Zr) O_x] Is mentioned.

As the substrate, glass, plastic, Si, Ge, GaA is used in the case of producing an amorphous vapor-deposited thin film.
It may be a compound semiconductor such as s or a metal, but when the substrate is heated from room temperature in order to produce a polycrystalline vapor-deposited thin film, it is important that it does not react with the vapor-deposited thin film at the substrate temperature used, such as a sapphire substrate or YSZ ( A stable and inexpensive substrate such as yttrium-doped zirconia oxide) is used even at high temperatures. In addition, MgO, SrTiO ₃
You may use what formed the intermediate | middle layers, such as.

Lattice matching with the vapor-deposited thin film is further important for producing a single crystal thin film. For example, in the case of a copper oxide superconductor, MgO, SrTiO ₃ , LaAlO ₃ , Nd.
GaO _{3 and the} like are preferably used.

[0021]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Comparative Example 1 99.9% of Y ₂ O ₃ and MnO ₂ powder were mixed and allowed to stand at room temperature for 20
Press in a pressure of 0 kg / cm ² and in air 95
A YMnO ₃ sintered body target was produced by sintering at 0 ° C. for 10 hours. Using this target, the distance between the MgO single crystal substrate and the target was 8 cm, and the substrate was about 1 cm.
A mass flow meter (flowmeter) was used to heat the flow rate to 100 in the vacuum chamber while heating to 50 ° C and keeping the pressure below 2 × 10 ^-6 torr.
Oxygen gas (purity 99.5 at 96 mtorr in sccm)
%) (Orifice opened 17.5%).

In this state, the output power from the laser was operated at 170 mJ per pulse at an effective 2 Hz for 20 minutes. The average energy density per pulse in the energy beam irradiation part on the target was about 1 J / cm ² . When the obtained thin film was observed with an optical microscope at a magnification of 1,000 times and 400 times, grains having a size of several μm were 200 μm × 200 μm square and the average was about 10 μm.
Seen individually. It should be noted that the target surface had irregularities sufficiently recognized on an optical microscope level. Under the same conditions, the substrate temperature was changed to 720 ° C, but in the X-ray diffraction, C-axis oriented YM
It was found that a thin film corresponding to nO ₃ was obtained.

Comparative Example 2 A thin film was prepared in the same procedure as in Comparative Example 1 using Cu having a purity of 99.99% and a thickness of 1 mm as a target. During the vapor deposition, almost no emission of evaporates characteristic of laser vapor deposition was observed. After the completion of vapor deposition, it was visually observed that no film was formed. The attached matter was identified by fluorescent X-ray, but again Cu was below the detection limit (20 to 30 Å or less). The surface of the Cu target remained extremely smooth.

Comparative Example 3 As in Example 1, Ba having a purity of 99.9% was melted by an arc melting method to prepare a target. The surface was covered with a white layer believed to be BaO. Using this target, a thin film was formed in the same procedure as in Comparative Example 1. During vapor deposition, light green emission peculiar to the excited Ba oxide was observed in the same manner as in Comparative Example 1, and when this thin film was observed with an optical microscope at a magnification of 1,000 times and 400 times, grains of a size of several μm were observed. 200 μm ×
About 10 pieces were observed on an average of 200 μm square.

The surface of the target irradiated with the laser had a thicker oxide layer, and the surface roughness was visually recognized. Further, after that, the same experiment was conducted three times in one week, but there was a tendency that the density increased about twice as much as the above grain density. It is considered that this is because the surface of Ba was unstable and the surface was changed. Comparative Example 4 A thin film was prepared in the same procedure as in Comparative Example 1 using a target prepared by firing BaO having a purity of 99.9% at about 300 ° C. A light green emission characteristic of excited Ba oxide was seen during deposition. When this thin film was observed with an optical microscope at a magnification of 1,000 times and 400 times, grains of several μm size were 200 μm × 200.
About 50 pieces were observed on average in the squares of μm. The target surface was also rough.

Example 1 A Y pellet having a purity of 99.9% was used as a target and vapor deposition was performed in the same procedure as in Comparative Example 1. A red emission characteristic of the excited Y oxide was seen during deposition, suggesting that Y was evaporating. When this thin film was observed with an optical microscope at a magnification of 1,000 times and 400 times, particles having a size of several μm were found to be on average about 1 or less in a 200 μm × 200 μm square, and the Y target surface remained extremely smooth.

A thin film having a composition of YCuO _x was produced by successively irradiating the target and the alloy target of YCu _{2 with} a laser. Other conditions were the same as in Comparative Example 1. When this thin film was observed with an optical microscope, particles having a size of several μm were found to be on average about 1 or less in a 200 μm × 200 μm square. Example 2 Targeting Y and Mn having a purity of 99.9%, Y and M
A thin film was prepared by sequentially irradiating n with a laser. Other conditions were the same as in Comparative Example 1. When this thin film was observed with an optical microscope at magnifications of 1,000 and 400, several micron
Only about 1 or less m-sized grains were observed on a 200 μm × 200 μm square, and the Y and Mn target surfaces remained extremely smooth. Although the substrate temperature was changed to 720 ° C. under the same conditions, it was found by X-ray diffraction that a thin film corresponding to YMnO ₃ was obtained.

[0028]

INDUSTRIAL APPLICABILITY The present invention is a target which can be laser-deposited and has solved the problem of grain when producing ceramic thin films such as oxide thin films such as oxide superconductor thin films and nitride thin films by the laser deposition method. By using, a thin film having high characteristics and excellent film shape suitable for an electronic device is provided.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a laser vapor deposition apparatus used in the present invention.

[Explanation of symbols]

 1 Excimer laser generator 2 Optical box 3 Vacuum chamber 4 Condenser lens 5 Ultraviolet light transmitting window 6 Target 7 Target holder 8 Substrate 9 Substrate holder 10 Shutter

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 39/24 ZAA B 9276-4M

Claims (2)

[Claims] 1. In a method for producing a thin film of a ceramic compound containing two or more kinds of metal elements on a substrate by vapor deposition, a metal target which reacts with the atmosphere or vapor atmosphere gas to form a stable compound surface, and others. A method for producing a vapor-deposited thin film, which comprises irradiating a target containing a metal element with a short pulsed energy beam sequentially or simultaneously to deposit a ceramic compound thin film. 2. The metal which reacts with the atmosphere or vapor deposition atmosphere gas to form a stable compound surface is rare earth metal, Ti,
The method for producing a vapor-deposited thin film according to claim 1, which is Zr, Hf, V or Mn.