JP2003171783A - Selective etching treatment method for metallic oxide film, metallic oxide film subjected to selective etching treatment by the same method, optical element, and electrically conductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a selective etching treatment method for a metallic oxide film by which the prescribed part of a metallic oxide film containing indium as the main component of metallic atoms is selectively subjected to etching, and finer working can be performed thereto. <P>SOLUTION: The selective etching treatment method for a metallic oxide film is provided with the following stages (A) and (B): the stage (A) where a structure-changed part is formed on an amorphous metallic oxide film containing indium as the main component of metallic atoms by the irradiation of a converged laser, and the stage (B) where only the amorphous part in the metallic oxide film in which the structure-changed part is formed is selectively dissolved with an etching solution. The metallic oxide film can be formed on a substrate made of glass. A laser having a pulse width of ≤10<SP>-6</SP>sec can be used. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for selectively etching an amorphous metal oxide film containing indium as a main component of a metal atom, and a metal oxide film selectively etched by the method. It also relates to an optical element and a conductive film.

[0002]

2. Description of the Related Art Metal oxides represented by indium oxide, tin oxide and zinc oxide are used as wide-gap semiconductors and are transparent and electrically conductive in the visible light region. Widely applied to. In particular, indium tin oxide (sometimes referred to as “ITO”), which is a metal oxide obtained by adding tin oxide to indium oxide, is a material having both good transparency and electrical conductivity, and therefore, a transparent electrode for a display, Touch panel metal oxide film, transparent electromagnetic shield film, transparent flat heater,
It has been applied in a very wide field as a heat ray reflective film.

The ITO film is formed on the substrate mainly by a dry process such as a sputtering method, a vacuum deposition method or an ion plating method, or a wet process such as a thermal decomposition method or a sol-gel method. Among them, the sputtering method is widely used because of its excellent film quality controllability and film thickness controllability.

Further, indium is a material having a very high sputtering rate, and it has a very high film-forming rate by the sputtering method and has excellent productivity and controllability.
A thin film can be formed.

For example, when an ITO film is used as a transparent electrode for a display, it is necessary to first form an ITO film on the entire surface of the substrate and then perform patterning using a photolithography process or the like. If the ITO film is in an amorphous state, it has a very high solubility in acid and easily dissolves, but if it is in a crystalline state, the solubility in an acid is extremely low, and the solubility is in the crystalline portion and the amorphous portion. About 1000 times different. Therefore, ITO
The amorphous state portion of the film can be dissolved and removed by utilizing the acid solubility or etching rate of the crystalline state or the state in which crystallization has progressed and the amorphous state. Therefore, for example, Japanese Patent Laid-Open No. 2000-12
Japanese Patent No. 9427 discloses a method of forming a film in a uniform amorphous state without fine crystals by controlling the partial pressure of water vapor when forming an ITO film by a sputtering method.

As described above, the amorphous metal oxide film containing indium as a main component is rapidly dissolved in an acid (for example, low-concentration hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, etc.) and has a different solubility from the crystalline state. Since it has, it is easy to perform an etching process using an acid as an etching solution, and in connection with this, the material is very widely industrially applied as a transparent electrode such as a transparent electrode for a display. ing.

Further, when a metal oxide film mainly composed of indium is formed at a high substrate temperature or after the film is formed, an annealing treatment is performed to crystallize the film, transparency and electric conductivity are improved, The etching rate for acid drops sharply. Therefore, industrially, amorphous ITO
A method is employed in which the film is patterned by etching and then annealed to be used as a transparent electrode.

When patterning is performed, the fine processing is naturally limited, and there is no problem as long as it is processing for an electrode for a display. However, an ITO film processed by this conventional patterning is extremely effective. There are almost no examples of application to optical elements such as diffraction gratings that require fine microfabrication.

On the other hand, pulse widths on the order of nanoseconds (10 ⁻⁹ seconds), picoseconds (10 ⁻¹² seconds), and even femtoseconds (10 ⁻¹⁵ seconds) are applied to transparent materials such as glass. A technique for collecting and irradiating an ultrashort pulsed laser beam and writing an induced structure in which the refractive index is modulated inside the glass by utilizing multiphoton absorption has been attracting attention, for example, Japanese Patent Laid-Open No. 2000-56112. Is disclosed in.

A metal oxide film of indium oxide or the like generally has a high refractive index, and when the film is formed by a sputtering method, direct current sputtering is possible because the target has conductivity, so that it is simple and inexpensive. It is widely used as a high-refractive index material because it can be used to form a film at a high film-forming rate in an apparatus.

[0011]

However, the pulse width of metal oxide films such as ITO, which is widely applied at present, is 10 ⁻⁶ seconds or less (for example, the pulse width is on the order of nanoseconds to femtoseconds). Irradiation with a pulsed laser and formation of an induced structure by the irradiation have not been examined.

Therefore, an object of the present invention is to selectively etch only a predetermined portion of a metal oxide film containing indium as a main component of a metal atom so that finer processing can be performed. And a metal oxide film selectively etched by the method. Another object of the present invention is to have a high refractive index, and further finely processed,
Another object is to provide an optical element or a conductive film made of a metal oxide film containing indium as a main component of metal atoms. Still another object of the present invention is to provide an optical element or conductive film that is transparent and has electrical conductivity.

[0013]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that indium is contained as a main component of a metal atom and is condensed on a metal oxide film in an amorphous state. When irradiated with a laser, a multi-photon absorption creates an extremely fine inductive structure in the irradiated area.
It can be formed with excellent controllability, and when the entire metal oxide film on which the fine inductive structure is formed is subjected to etching treatment, only the non-irradiated portion is selectively dissolved, and extremely fine patterning processing is performed. The inventors have found that the above can be achieved and have completed the present invention.

That is, the present invention is a method for selectively etching a metal oxide film containing indium as a main component of metal atoms, which comprises the following steps (A) to (B). This is a selective etching method for the metal oxide film. Step (A): A step of forming a structure-changed portion having a changed structure by irradiating a focused laser beam on a metal oxide film containing indium as a main component of a metal atom and being in an amorphous state. A step of selectively dissolving only the amorphous state portion of the metal oxide film having the structure-changed portion with an etching solution

The amorphous metal oxide film containing indium as a main component of metal atoms is
It preferably contains at least one metal atom selected from tin, zirconium, zinc, titanium, cerium, tantalum, germanium, vanadium, yttrium and niobium. Further, a metal oxide film containing indium as a main component of metal atoms and in an amorphous state is formed by a sputtering method in a film forming atmosphere having a water vapor partial pressure of 5 × 10 ^{−4 to} 5 × 10 ⁻² Pa. Is preferred. Furthermore, a metal oxide film containing indium as a main component of metal atoms and in an amorphous state may be formed on the glass substrate.

The laser may have a pulse width of 10 ^-6 seconds or less. Further, as the laser, coherent light due to multi-beam interference can be preferably used.

Further, the present invention is produced by subjecting an amorphous metal oxide film containing indium as a main component of a metal atom to a selective etching treatment by the selective etching treatment method of the metal oxide film. A metal oxide film that has been selectively etched is provided. Furthermore, the present invention provides an optical element or a conductive film in which the metal oxide film subjected to the selective etching treatment is used as a constituent element.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail with reference to the drawings as necessary. In addition, the same code | symbol may be attached | subjected about the same member. [Selective Etching Treatment Method for Metal Oxide Film] The selective etching treatment method for a metal oxide film of the present invention is a selective etching treatment for a metal oxide film containing indium as a main component of a metal atom. Specifically, the method includes the following steps (A) and (B). Step (A): A metal oxide film containing indium as a main component of metal atoms and in an amorphous state (“amorphous IO
(May be referred to as a "system film"), a step of forming a structure-changed portion whose structure is changed by irradiation of a focused laser beam. Step (B): Metal oxide having a structure-changed portion formed by the step (A) Step of selectively dissolving only an amorphous state part in a material film (sometimes referred to as “partial structural change IO-based film”) with an etching solution

[Step (A)] In the step (A), the amorphous I
Irradiate a focused laser to a predetermined part of the O-based film,
Optical processing is performed to change the structure of the irradiated part of the focused laser to form a structural change part in which the structure is partially changed in the amorphous IO-based film, and the irradiated part of the focused laser A partially-structure-changed IO-based film having a changed structure is manufactured. The amorphous IO-based film is usually formed on the substrate. In the present invention, the amorphous IO-based film can be subjected to optical processing while being formed on a substrate (for example, a glass substrate).

(Amorphous IO-based film) In the amorphous IO-based film, the material (or material) is not particularly limited as long as it is a metal oxide containing indium as a main component of metal atoms. In the metal oxide, indium, which is the main component of metal atoms, is 70 wt% or more, preferably 90 wt% or more, and more preferably 95 wt% with respect to the total amount of metal atoms.
It is important that it is included.

Specifically, in the metal atom of the metal oxide as the material of the amorphous IO-based film, the main component is indium, and the other contained components (subcomponents) are tin, zirconium, zinc, Metal atoms such as titanium, cerium, tantalum, germanium, vanadium, yttrium, and niobium can be used. These other components may be used alone or in combination of two or more. As other components contained in the metal atom, tin and zinc are preferable,
Tin is particularly suitable. The amorphous IO-based film is made of a metal oxide, and indium as a main component of metal atoms is contained in the form of indium oxide. Further, the metal atom of the other contained component may be contained in the form of metal oxide. Specifically, a metal oxide (indium tin oxide: ITO) in which indium oxide and tin oxide are mixed can be preferably used as the metal oxide that is the material of the amorphous IO-based film.

It is important that the amorphous IO-based film that is subjected to optical processing by the focused laser has an amorphous state (amorphous). The amorphous IO-based film preferably has a completely amorphous state, but may have a partially crystalline state (particularly a microcrystalline state). The method for forming the amorphous IO-based film is not particularly limited, and a known or common film forming method can be used. More specifically, as a film forming method, for example, a sputtering method,
A dry process such as a vacuum deposition method or an ion plating method, or a wet process such as a thermal decomposition method or a sol-gel method can be used.

In these film forming methods, the amorphous I
An O-based film can be formed. The substrate is not particularly limited as long as it is a known or commonly used substrate (for example, a glass substrate, a plastic substrate, a metal substrate, etc.), but a glass substrate (glass substrate) can be preferably used. The material (glass) of the glass substrate is not particularly limited.

In the present invention, the amorphous IO-based film is preferably formed by a sputtering method.
For example, in the case of forming a film by a sputtering method, in order to suppress the growth of fine crystals and obtain a uniform amorphous structure, a moisture content such that the partial pressure of water vapor is 5 × 10 ^{−4 to} 5 × 10 ⁻² Pa is formed. It can be introduced into the film atmosphere. In particular, when the power applied to the target (metal oxide) during sputtering is increased to increase the film formation rate, the substrate temperature rises due to radiant heat associated with film formation, recoil atoms, etc.
Microcrystals are easily generated, but they can be suppressed by introducing water under the above conditions. The method of introducing water and other film forming conditions are not particularly limited, but it is sufficient that the selective etching property relating to the method of the present invention is sufficiently obtained. In particular, a film in a uniform amorphous state without microcrystals is required. Conditions that allow formation are preferred.

The amorphous IO film is a film (or layer) having a flat upper surface, but the upper surface may be flat or uneven, and the size of the upper surface may be different. (Area) is also not particularly limited. Furthermore, the thickness (or layer thickness) of the amorphous IO-based film is, for example, 0.01 to 50.
It can be selected from the range of about μm (preferably 0.05 to 30 μm, more preferably 0.1 to 10 μm). If the thickness of the amorphous IO-based film is less than 0.01 μm, it becomes difficult to obtain a planarly continuous amorphous IO-based film, and if it exceeds 50 μm, cracks occur in the amorphous IO-based film. Problems such as occurrence may occur.

The amorphous IO-based film may have either a single-layer structure or a multi-layer structure. Furthermore, the amorphous IO-based film may contain other materials, additives, and the like, if necessary, in addition to the metal oxide.

Further, the amorphous IO type film usually has excellent transparency, but it is in the visible light wavelength region (for example, 400 n
It is desirable that the total light transmittance is 10% or more (preferably 50% or more, more preferably 85% or more) in (m to 800 nm). In this way, when the light transmittance is 10% or more, laser processing can be easily performed by irradiation with a laser having a wavelength in the visible light wavelength region.

(Concentrated Laser) In the present invention, it is important to use a focused laser (sometimes referred to as “focused laser”). By irradiating a focused laser from outside the amorphous IO-based film, amorphous I
It is possible to change the structure of the irradiation portion irradiated with the focused laser of the O-based film and its peripheral portion, and it is possible to form a fine structure change portion (induced structure portion). For example, when the wavelength of the laser to be irradiated is 800 nm, when the laser that is not focused is irradiated to the amorphous IO-based film,
The substrate does not change at all, but when the focused laser is irradiated, multiphoton absorption (for example, two-photon absorption, three-photon absorption, four-photon absorption, five-photon absorption, etc.) occurs. It becomes possible to form an induced structure in the amorphous IO-based film.
The probability that such multiphoton absorption occurs increases in proportion to the intensity of light, and the higher the intensity, the more likely multiphoton absorption occurs.

In particular, in the present invention, by appropriately adjusting the intensity of the laser beam and the degree of focusing thereof, the substrate (in particular, the glass substrate) is not affected (that is, no induced structure is generated). However, the induced structure can be formed only in the amorphous IO-based film. The energy band gap of a metal oxide film such as an amorphous IO-based film is about 3.5 eV, depending on the materials and additives. on the other hand,
The energy band gap of the substrate is, for example, about 8.9 eV depending on the type of glass and additives in the case of a glass substrate, and the energy of a metal oxide film such as an amorphous IO-based film. It is larger than the band gap by about 5.4 eV. Therefore, for example, when the substrate is a glass substrate, in order to cause multiphoton absorption in the glass substrate, multiphoton absorption of approximately 6 photons or more needs to occur, and extremely high intensity laser irradiation is required. Become. Therefore, the substrate having an energy band gap of 5.0 eV or more (preferably 7.0 eV or more, more preferably 8.0 eV or more) is preferable.

Therefore, in the present invention, the intensity of the laser beam and the degree of focusing thereof are appropriately adjusted by irradiation of the focused laser to form an induced structure in the portion irradiated with the focused laser. Moreover, even if the thickness of the amorphous IO-based film formed on the substrate is smaller (or smaller) than the size of the focused spot diameter of the focused laser, the amorphous IO-based film is amorphous. The induced structure can be formed only in the IO-based film.

Such a laser is not particularly limited, but has a pulse width of 10 ⁻⁶ seconds or less (for example, 1 × 10 6).
^-6 seconds to 1 × 10 ⁻¹⁵ seconds) laser can be used, preferably 1 × 10 ⁻⁹ seconds to 1 × 10 ⁻¹⁵ seconds, and particularly 1 × 10 ⁻¹² seconds to 1 × 10 ^{−. A 15} second laser (sometimes referred to as an "ultrashort pulse laser") is preferred. Small pulse width (especially pulse width 1 × 1
An ultrashort pulse laser of 0 ^-12 seconds to 1 x 10 ^-15 seconds) is preferable because high light intensity can be easily obtained. Also,
It is also possible to form a finer induction structure portion.

The pulse width is 1 × 10 ⁻¹² seconds to 1 × 1.
An ultrashort pulse laser having a pulse width of 0 ^-15 seconds has a pulse width of 10 × 10 ^-15 seconds to 500 × 10 ^-15 seconds (preferably 5 × 10 ^-15 seconds).
A pulse laser of about 0 × 10 ⁻¹⁵ seconds to 300 × 10 ⁻¹⁵ seconds) is suitable. Such an ultra-short pulse laser can be obtained, for example, by reproducing and amplifying a laser or dye laser using a titanium-sapphire crystal as a medium.

In the laser (in particular, ultrashort pulse laser), its wavelength is preferably, for example, in the visible light wavelength region (for example, 400 to 800 nm). Moreover, as the repetition, for example, 1 Hz to 8
Can be selected from the range of 0MHz, usually 10H
It is about z to 500 kHz.

The average output power or irradiation energy of the laser (especially, ultrashort pulse laser) is not particularly limited, and may be appropriately selected according to the size of the target structure change portion and the degree of structure change. Can be done, for example, 50
0 mW or less (for example, 1 to 500 mW), preferably 5
˜300 mW, more preferably 10 to 100 mW. Thus, in the present invention, the irradiation energy of the laser (in particular, the ultrashort pulse laser) may be low.

In the present invention, the laser may use coherent light due to multi-beam interference (for example, two-beam interference or interference of three or more light beams). By using coherent light due to multi-beam interference such as two-beam interference as the laser, it is possible to easily control and form a periodic structure of a wavelength order of laser light into a desired periodic structure. For example, in the case of irradiation by two-beam interference, it is also possible to control the interval of the periodic structure by controlling the angle between the beams. Furthermore, a complex periodic structure can be freely formed by appropriately scanning the amorphous IO-based film or substrate during irradiation, or by using a plurality of light beams, and these methods are also particularly limited. Not a thing.

The method for focusing the laser is not particularly limited, and for example, a method using a condenser lens can be preferably adopted. Such a condenser lens is not particularly limited, and can be appropriately selected according to the material of the amorphous IO-based film, the size of the target structural change portion, the degree of structural change, and the like.

The irradiation spot diameter of the focusing laser is
It is not particularly limited and can be appropriately selected according to the size of the target structural change portion, the degree of structural change, the size of the condenser lens, the numerical aperture or the magnification, and for example, 1.0 to
It can be selected from the range of about 50 μm (preferably 10 to 30).

(Irradiation Method) The method of irradiating the converging laser is not particularly limited, and, for example, irradiates only one point or any point on an arbitrary site (or site), or while moving the focus position. It is possible to adopt a method of irradiating the particles in a circular shape. The line shape when irradiating the focused laser light while moving the focus position of the focused laser light is not particularly limited, and may be any line shape, for example, a linear shape or a curved shape. Can be mentioned. Also,
The focus position of the condensed laser light can be moved continuously or intermittently. By irradiating the focused laser light under computer control, it is possible to irradiate the focused laser light while moving the focal position of the focused laser light, even in any complicated line shape.

FIG. 1 is a schematic bird's-eye view showing an example of the method of irradiating the focused laser beam of the present invention. In FIG. 1, 1 is a partially structurally changed IO-based film, 11 is an amorphous IO-based film, 2 is a structurally changed portion, 3 is an amorphous state portion (amorphous portion), and 4 is a substrate. Further, 51 is an ultrashort pulse laser having a pulse width of 10 ⁻¹² seconds or less (sometimes referred to as “laser”), 52 is a condenser lens, and 5 is a condenser laser. The partially structurally changed IO-based film 1 is made of an amorphous IO-based film 11, and the structurally changed portion 2 is a portion whose structure is changed by the irradiation of the focused laser 5, and The crystalline portion 3 is a portion that is not affected by the irradiation of the concentrated laser 5 and retains the original amorphous state (structure unchanged portion).

The amorphous IO-based film 11 is formed by being formed on the substrate 4, and the upper surface of the amorphous IO-based film 11 is a plane and parallel to the XY plane. , Or perpendicular to the Z axis.

A focusing laser 5 is focused and irradiated on a predetermined portion of the amorphous IO-based film 11. The condenser laser 5 is a laser in which the laser 51 is condensed by the condenser lens 52.

Reference numeral 6a denotes an initial position or a central position (in some cases referred to as "irradiation start position") at which focus is applied when the irradiation of the collective laser 5 is started, and 6b denotes irradiation of the collective laser 5. When the focus is finished, the final focused position or its center position (may be referred to as "irradiation end position"), 6c is the focus of irradiation of the converging laser 5 or its center position (simply referred to as "focus position"). Is a moving direction in which the irradiation start position 6a moves to the irradiation end position 6b. Reference numeral 6 denotes a locus (sometimes referred to as a “focal position locus”) along which the focal position of irradiation of the converging laser 5 or the central position of the focal point has moved. That is, in FIG. 1, the focal position of the condensing laser 5 is changed from the irradiation start position 6a to the irradiation end position 6a.
It is continuously and linearly moved in the moving direction 6c of the focus position over b, and the locus of the moved focus position is the focus position locus 6.

Specifically, the amorphous IO film 11 is irradiated with the focusing laser 5, and the structure at each focal position on the focal position locus 6 of the focusing laser 5 and its peripheral portion (near portion). Due to this partial structural change, the partial structural change IO-based film 1 has a linear structural changed portion 2 and an amorphous portion 3 in the original state.

Further, since the position of the focal point is continuously moved during irradiation of the focusing laser 5, the amorphous I
On the O-based film 11, the structure-changed portion 2 is formed, which is formed by a portion whose structure is changed and which is also moved continuously in accordance with the movement of the focal point position and which is extended and changed in the moving direction. As shown in FIG. 1, the focus position of the focusing laser 5 is set to the moving direction 6
When the irradiation start position 6a is moved in this direction to the irradiation end position 6b, the structural change portion 2 formed along the movement direction 6c can be formed. Therefore, the longitudinal direction of the structure changing portion 2 is the moving direction 6c.

The speed (moving speed) for moving the focus position of the focusing laser 5 is not particularly limited, and the amorphous IO-based film 1
It can be appropriately selected according to the material of No. 1, the irradiation energy of the condensing laser 5, and the like. By controlling the moving speed, it is possible to control the size and the like of the structural change portion 2.

The focus position of the condenser laser 5 can be moved by moving the relative position between the laser 51 and the condenser lens 52 and the amorphous IO-based film 11, for example, the laser 51 and the condenser lens 52. And / or amorphous IO
This can be done by moving the system film 11.
Specifically, for example, an amorphous IO-based film (irradiation sample) is placed on a stage that can be precisely moved in a two-dimensional or three-dimensional direction, and the laser generator and the condenser lens are set to the amorphous state. The structure-changed part is produced at an arbitrary part of the amorphous IO-based film by fixing the IO-based film so that it is in focus (any part may be enough), and moving the stage to move the focus position. can do.

As described above, the partially structurally changed IO-based film is
Irradiate a focused laser (in particular, a laser focused with an ultra-short pulse laser with a pulse width of 10 ^-12 seconds or less), and move the focal point position as needed. It can be produced by forming a site having a changed structure (structure-changed part).

Further, in FIG. 1, the focus position of the focusing laser 5 is moved while being held on the upper surface of the amorphous IO-based film 11 or in the vicinity thereof. However, even if the focus position of the focused laser beam 5 moves up and down to some extent and the focus position shifts to the substrate, the intensity of the focused laser beam 5 remains unchanged.
By adjusting the strength so that the induced structure is formed on the substrate (such as multiphoton absorption) and the induced structure is not formed on the substrate (glass substrate, etc.) 4, it is extremely excellent. It is possible to form the linear induced structure portion (structure change portion 2) only in the amorphous IO-based film 11 with reproducibility.

In FIG. 1, the structure changing portion 2 is continuously formed in the moving direction by moving the focal position of the focusing laser 5, and the moving direction of the focal position is the longitudinal direction. . Therefore, the length of the structure changing portion 2 in the longitudinal direction can be adjusted, for example, in accordance with the moving distance by which the focal position of the condenser laser 5 is moved.
For example, when the focus position of the focusing laser 5 is linearly moved, the length of the structure changing portion 2 in the focus moving direction is equal to or almost equal to the moving distance of moving the focus position of the focusing laser 5. Can be

Further, in the present invention, the degree of structural change in the structural change portion 2 may be uniform or non-uniform. Therefore, the structurally changed portion 2 may have a uniform degree of structural change, and further, from the end on the amorphous portion side toward the inside or the focus position or the center thereof,
The structure may be changed so that the degree of the structure change gradually and continuously increases. In the present invention, the interface (or boundary) between the structurally changed portion 2 and the amorphous portion 3 may be clear or unclear, but is preferably clear.

The size of the structural change portion is not particularly limited, and the diameter or the length of one side is 1 mm or less (preferably 5 mm).
Even if it is extremely small (less than or equal to 00 μm), it can be formed with precise control. In particular, by using an ultrashort pulse laser as the laser, it becomes possible to control the structural change portion more precisely.

In the present invention, the number of structure-changed portions in one partial structure-changed IO-based film is not particularly limited, and may be either a single number or a plurality. When a plurality of structure changing portions are provided, they can be formed with an appropriate interval. The space between the structural change portions can be arbitrarily selected. The space between the structural change portions is, for example,
It is preferably 5 μm or more. If the distance between the structure-changed portions is less than 5 μm, the structure-changed portions may be fused with each other during the production of the structure-changed portions, and it may not be possible to form a plurality of independent structure-changed portions.

The size and shape of the structurally changed portion, the degree of structural change, etc. are determined by the irradiation time of the focusing laser, the moving direction and speed of the focal point of the focusing laser, the material of the amorphous IO-based film. , The pulse width of the laser, the irradiation energy, the numerical aperture and magnification of the condenser lens, and the like.

The structure-changed portion may have a different structure from the amorphous portion (structure-unchanged portion), and examples of the different structure include, for example, a change in density (eg, a higher density). Alternatively, it may have a different structure due to densification or desorption of oxygen atoms. Therefore,
The structure-changed portion may have a higher density than the amorphous portion and may be in a state where crystallization is progressing. The structure-changed portion may not be in a completely crystallized state as long as crystallization is more advanced than in the amorphous portion, but it is preferably in a completely crystallized state. In the present invention, the structure-changed portion formed by the irradiation of the focused laser has a lower solubility in the etching solution than the amorphous portion, and crystallization progresses to the extent that selective etching is possible. is important.

(Step (B)) In the step (B), only the amorphous state portion which is the non-irradiated portion of the focused laser in the partially structurally changed IO-based film is selectively dissolved by the etching solution. By selectively melting only this amorphous state portion, a metal oxide film subjected to selective etching is produced.

As described above, the metal oxide film (IO-based film) containing indium as a main component of the indium-based film such as the partially structurally-modified IO-based film has an amorphous state part and a structure-changed part in which crystallization has progressed. Since it has a different solubility from the (crystallization progressing portion), it is a non-irradiated portion of the focused laser due to the etching liquid (for example, the etching liquid capable of dissolving the IO-based film in the amorphous state portion). It is possible to selectively dissolve only the amorphous state portion and leave only the structural change portion (crystallization progressing portion), which is the irradiation portion of the focused laser, where crystallization has progressed to a certain extent or more.

The method of selectively dissolving is not particularly limited as long as it is a method that can bring the partially structurally changed IO-based film into contact with the etching solution, but the partially dissolved IO-based film is partially dissolved in the etching solution. The method of immersing is preferably used.

The etching solution is particularly preferably one that can sufficiently obtain the selective etching property between the amorphous state portion and the structural change portion of the metal oxide film (IO-based film) containing indium as the main component of the metal atom. It can be used without limitation. That is, a metal oxide film (IO-based film) containing indium as a main component has a high solubility in the amorphous state portion and a low solubility in the structural change portion (dissolution of the amorphous state portion and the structural change portion). Those with a large difference in sex) can be used. The etching solutions may be used alone or in combination of two or more. Specifically, as the etching solution, for example, an aqueous solution of an inorganic acid such as an aqueous solution of hydrochloric acid, an aqueous solution of sulfuric acid, an aqueous solution of nitric acid, an aqueous solution of oxalic acid can be preferably used. The aqueous solution of these inorganic acids preferably has a low concentration. When the etching solution is, for example, an aqueous hydrochloric acid solution, the concentration of hydrochloric acid is 0.5 to 30% by weight (preferably 1 to 10% by weight).
It can be selected from a range of degrees. The amount of etching liquid used is not particularly limited.

The time of immersion in the etching solution is not particularly limited and can be appropriately selected depending on the type and concentration of the etching solution. However, only the amorphous state portion is dissolved and the structural change portion (crystallization progresses). It is important that the period of time is such that no part or part is dissolved.

[Selective Etching-Processed Metal Oxide Film] The selective etching-processed metal oxide film of the present invention is produced by the above-described selective etching process of the metal oxide film, that is, the amorphous IO-based film. Partial structural change by changing the structure of a predetermined part of the film by irradiation of a focused laser I
It can be manufactured by obtaining an O-based film and selectively dissolving only an amorphous state part (amorphous part) in the partially structurally changed IO-based film with an etching solution.

When such a non-crystalline IO-based film was irradiated with a focused laser, the structurally changed portion (particularly, crystallization proceeded) in the irradiated portion of the focused laser due to the change in the structure of the metal oxide. (Structural change portion) is formed, and as shown in FIG. 2, a partially structurally changed IO-based film having a structural change portion and an amorphous state portion is produced. FIG. 2 is a schematic cross-sectional view showing an example of a partially structurally changed IO-based film. In FIG. 2, 1 to 4 are, similarly to FIG. 1, a partially structurally changed IO-based film, a structurally changed portion, an amorphous state portion, and a substrate, respectively. The partially structurally changed IO-based film 1 has a structurally changed portion 2
And the amorphous state portion 3 and are formed on the substrate 4.

By performing an etching process on the partially structurally changed IO-based film 1, the amorphous state portion 3 is formed.
Only the structure-changed portion 2 is left by selectively dissolving and removing only the metal oxide film, and a metal oxide film subjected to selective etching is obtained. As shown in FIG. 3, the metal oxide film subjected to such selective etching treatment has voids or air. FIG. 3 is a schematic cross-sectional view showing an example of the metal oxide film subjected to the selective etching treatment of the present invention. In FIG. 3, 7 is a metal oxide film that has been subjected to selective etching, 8 is a void portion, 9 is a metal oxide portion, and 4 is a substrate as in FIG. 1 or 2. The metal oxide film 7 that has been subjected to the selective etching includes a void portion 8 and a metal oxide portion 9. The refractive index of the void portion 8 is usually about 1, while the refractive index of the metal oxide portion 9 is about 2. Therefore, the difference in refractive index between the void portion 8 and the metal oxide portion 9 is as large as about 1, and the metal oxide film 7 subjected to the selective etching can obtain an optical response due to a large difference in refractive index which has never been obtained.

The metal oxide film which has been subjected to the selective etching treatment of the present invention is appropriately laser-processed by a focusing laser according to the required function and the required characteristics. Also,
It may be used as it is as a metal oxide film, or may be used in combination with other members. Furthermore, the metal oxide film that has been subjected to the selective etching can be subjected to any processing or treatment (various post-treatments or the like). Since the metal oxide film subjected to the selective etching has a metal oxide portion and a void portion having different refractive indexes from each other, for example, see “Kikuta et al., Optics, Vol. 27, No. 1, p12,”.
Optical elements such as a diffraction grating, a polarizing element, a retardation plate, a polarizing beam splitter, a wavelength selection filter, and an optical waveguide as described in "1998", an optical element to which conductivity is imparted, a conductive film ( In particular, it can be suitably used as a transparent conductive film, etc. In particular, it can be applied to a photonic crystal or the like by utilizing a large difference in refractive index between a metal oxide portion and a void portion.

[0064]

According to the selective etching treatment method of the present invention, the metal oxide film containing indium as a main component of the metal atom is subjected to selective etching treatment in which finer processing is performed. A film is obtained. The metal oxide film subjected to the selective etching has a high refractive index.
Moreover, it is transparent and has electrical conductivity. Therefore, an optical element or a conductive film having an excellent function can be easily manufactured.

[0065]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. (Example 1) Commercially available soda-lime glass substrate and having a diameter of 15
Inch ITO target [97 parts by weight of indium oxide and tin oxide (indium oxide): 3 parts by weight (tin oxide)
Of a metal oxide mixed in the ratio of the
(Made by Nippon Vacuum Co., Ltd.). 4 × 1 in the vacuum chamber
After evacuating to 0 ^-4 Pa, use argon gas at 30 SC
By introducing CM and oxygen gas at 0.5 SCCM and adjusting the opening / closing degree of the main valve of the high vacuum pump, the pressure can be adjusted to 0.4
It was adjusted to Pa. However, argon gas was introduced by bubbling distilled water contained in a cleaning bottle. As a result, the partial pressure of water vapor in the vacuum chamber was maintained at 3 × 10 ⁻³ Pa. Then, a DC power source was applied to the ITO target to apply power of 300 W, and the thickness of 100 W was applied to the glass substrate.
nm indium tin oxide film (ITO film) is formed.
A sample (irradiated sample A) in which an O film was formed on a glass substrate was obtained.

A titanium-sapphire femtosecond pulse laser device and an objective lens (magnification: 10) are focused from the upper surface of the ITO film formed on the glass substrate of this irradiation sample A to or near the upper surface. Ultra short pulse laser (irradiation wavelength: 800 nm, pulse width: 150 × 10 ⁻¹⁵ seconds, repetition: 200 kHz)
Was irradiated while moving the irradiation sample A in a direction perpendicular to the irradiation direction at a moving speed of about 500 μm / sec under the conditions of irradiation energy (average output): 60 mW and irradiation spot diameter: about 20 μm. Only in the ITO film part, a structural change having a different structure from the original ITO film from the focus position (irradiation start position) where the irradiation of the ultrashort pulse laser is started to the focus position (irradiation end position) where the irradiation is stopped A metal oxide film having a portion (induced structure portion) was obtained.

When the cross section of the irradiated sample A irradiated with this ultrashort pulse laser was observed, the width of the structurally changed portion was about 20 μm, and the entire irradiated portion had a structural change in the film thickness direction ( That is, the thickness of the structurally changed portion is 100 nm). That is, the width is about 20 μm and the thickness is 1
A line-shaped structural change portion having a cross section of 00 nm was formed.

Further, the sample having this structurally changed portion was immersed in a 3 wt% hydrochloric acid aqueous solution for 30 seconds, then taken out and washed with distilled water. As a result, only the structurally changed part (induced structure part) observed by the above-mentioned cross-section observation remains on the glass substrate, and the other non-irradiated parts (unstructured part) are completely melted from the glass substrate. Then, it disappeared and became a void. The structure-changed portion was a portion where crystallization proceeded.

Therefore, the selective-etched ITO having the inductive structure and the void is formed on the glass substrate.
A film was formed.

Comparative Example 1 A commercially available glass substrate (thickness: 1.5 mm) similar to that in Example 1 was irradiated with an ultrashort pulse laser under the same conditions as in Example 1, and the glass substrate was observed. No structural change occurred.

Comparative Example 2 Ultrashort pulse laser irradiation was performed under the same conditions as in Comparative Example 1 except that the intensity (irradiation energy) of the ultrashort pulse laser was increased to 500 mW. Along the inside, a structural change occurred over a range of width 20 μm and length 100 μm. That is, the induced structure formed was a structure that was long in the vertical direction in the irradiated portion of the ultrashort pulse laser.

Therefore, it is apparent from Example 1 and Comparative Examples 1 and 2 that the induction structure can be selectively formed only on the ITO film by the method of Example 1.

Comparative Example 3 An ITO film having a thickness of 100 nm was formed on a glass substrate in the same manner as in Example 1 except that argon gas was directly introduced into the vacuum chamber without bubbling. Then, the sample at 200 ℃,
After annealing for 5 hours, under the same conditions as in Example 1,
Irradiated with ultra-short pulse laser. As a result, the original ITO
A metal oxide film having a structure change portion having a structure different from that of the film was obtained. However, when the sample having this metal oxide film was immersed in a 3% by weight hydrochloric acid aqueous solution for 30 seconds, then taken out and washed with distilled water, it was dissolved regardless of whether the ultrashort pulse laser was irradiated or not. However, the same sample as before dipping in the hydrochloric acid aqueous solution was obtained.

Comparative Example 4 An ITO film having a thickness of 100 nm was formed on a glass substrate in the same manner as in Example 1 except that argon gas was directly introduced into the vacuum chamber without bubbling. Then, the sample at 200 ℃,
After annealing for 5 hours, under the same conditions as in Example 1,
The sample was irradiated with an ultrashort pulse laser, and then the sample was annealed at 200 ° C. for 5 hours. Then, this sample was immersed in a 3% by weight hydrochloric acid aqueous solution for 30 seconds, then taken out and washed with distilled water. It did not dissolve regardless of whether the ultrashort pulse laser was irradiated or not, and it was immersed in a hydrochloric acid aqueous solution. The same sample as before was obtained.

(Example 2) In the same manner as in Example 1, a sample (irradiated sample B) in which an ITO film having a thickness of 1.5 μm was formed on a glass substrate was prepared. When this irradiation sample B was irradiated with an ultrashort pulse laser under the same conditions as in Example 1, 15 lines having a width of 20 μm and a length of 8 mm were formed at intervals of 15 μm, and a diffraction grating of about 0.5 mm ( A diffraction grating A) was produced.

Then, the diffraction grating A was immersed in a 5% by weight hydrochloric acid aqueous solution for 60 seconds, then taken out and washed with distilled water. As a result, only the portion of the ITO film irradiated with the ultrashort pulse laser remained on the glass substrate, and a diffraction grating (diffraction grating B) having a periodic uneven structure was obtained.

The diffraction grating B has a wavelength of 632.8 nm.
When a He-Ne (helium-neon) laser was irradiated, the appearance of transmission diffraction spots was confirmed. Also,
When a similar diffraction spot was confirmed for the sample in which the distance between the irradiated lines was appropriately changed, it was confirmed that the diffraction spot changed as in the classical theory.

Example 3 Commercially available glass substrate (thickness:
1.5 mm), and a thickness of 200
Sample with a 20 nm ITO film (irradiation sample C)
Got This irradiation sample C was subjected to laser irradiation by irradiation with two light fluxes using the optical system shown in FIG. The laser generator used was the same titanium sapphire femtosecond pulse laser device as in Example 1, with irradiation energy (average output) of 20 mW and irradiation time of 10 seconds.
The angle (θ) formed by the two light fluxes was set to 75 °, and periodical structural changes were written on the ITO film by using the interference of laser light as shown in FIG. As a result, the diameter is about 60 μm
A periodic structure corresponding to the optical interference is formed in the circular area of
The period was about 800 nm.

Then, the sample having this periodic structure was dipped in a 3% by weight aqueous hydrochloric acid solution for 30 seconds, taken out and washed with distilled water. The irradiation part had a fine structure in the wavelength order of 800 nm. An ITO film having only a periodic structure was obtained. In other words, the selective etching treatment yielded an ITO film having a periodic structure in which only extremely fine irradiated parts remained.

When natural light was incident on the sample having the fine periodic structure from the upper surface of the ITO film,
As in the classical theory, it was confirmed that the light acts in the wavelength region corresponding to the periodic structure as a quarter-wave plate.

In the examples and comparative examples, the morphology and shape of the cross section of the ITO film having the induced structure portion was observed using a scanning electron microscope.

[Brief description of drawings]

FIG. 1 is a schematic bird's-eye view showing an example of a focused laser beam irradiation method of the present invention.

FIG. 2 is a schematic cross-sectional view showing an example of a partially structurally changed IO-based film.

FIG. 3 is a schematic cross-sectional view showing an example of a metal oxide film subjected to selective etching treatment of the present invention.

FIG. 4 is a schematic diagram showing an optical system of two-beam interference.

FIG. 5 is a schematic diagram showing interference of laser light.

[Explanation of Codes] 1 Partial structural change IO-based film 11 Amorphous IO-based film, 2 Structural change part 3 Amorphous state part (amorphous part) 4 Substrate 5 Focused laser 51 Pulse width 10 ^-12 Ultra short pulse laser 52 which is less than or equal to seconds 52 Focusing lens 6 Focus position locus 6a of focusing laser 5 Irradiation start position 6b of focusing laser 5 Irradiation end position 6c of focusing laser 5 Moving direction of focusing position of focusing laser 5 7 Metal oxide film that has been subjected to selective etching 8 Void portion 9 Metal oxide portion

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masakatsu Urairi             1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto             Electric Works Co., Ltd. (72) Inventor Mika Horiike             1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto             Electric Works Co., Ltd. (72) Inventor Kazuyuki Hirao             8-94 Tanaka Shimoyanagicho, Sakyo Ward, Kyoto City, Kyoto Prefecture F-term (reference) 4G059 AA08 AB07 AB11 AC12 AC30                       EA03 EB04                 4K057 WA11 WB20 WC10 WE08 WN01

Claims (9)

[Claims] 1. A method of selectively etching a metal oxide film containing indium as a main component of a metal atom, comprising the following steps (A) to (B): Method for selectively etching a material film. Step (A): A step of forming a structure-changed portion having a changed structure by irradiating a focused laser beam on a metal oxide film containing indium as a main component of a metal atom and being in an amorphous state. A step of selectively dissolving only the amorphous state portion of the metal oxide film having the structure-changed portion with an etching solution 2. The amorphous metal oxide film containing indium as a main component of metal atoms is at least one selected from tin, zirconium, zinc, titanium, cerium, tantalum, germanium, vanadium, yttrium and niobium. The method for selectively etching a metal oxide film according to claim 1, wherein the metal oxide film contains the metal atom. 3. A sputtering method in which a metal oxide film containing indium as a main component of a metal atom and in an amorphous state has a water vapor partial pressure of 5 × 10 ^{−4 to} 5 × 10 ⁻² Pa. 1 or 2 formed by
A method for selectively etching a metal oxide film according to claim 1. 4. The metal oxide according to claim 1, wherein an amorphous metal oxide film containing indium as a main component of metal atoms is formed on a glass substrate. A method for selectively etching a film. 5. The method for selectively etching a metal oxide film according to claim 1, wherein the laser has a pulse width of 10 ⁻⁶ seconds or less. 6. The method for selectively etching a metal oxide film according to claim 1, wherein the laser is coherent light due to multi-beam interference. 7. A metal oxide film which contains indium as a main component of metal atoms and is in an amorphous state.
7. A metal oxide film subjected to selective etching, which is produced by performing a selective etching treatment by the selective etching treatment method for a metal oxide film according to any one of items 1 to 6. 8. An optical element in which the metal oxide film subjected to selective etching according to claim 7 is used as a constituent element. 9. A conductive film in which the metal oxide film subjected to the selective etching according to claim 7 is used as a constituent element.