JP2005239502A - Method for microfabricating glass, and method for producing glass optical waveguide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for smoothly patterning a glass film comprising Bi<SB>2</SB>O<SB>3</SB>or the like, and to provide a glass optical amplification waveguide using the glass film. <P>SOLUTION: In the method for producing a glass optical waveguide with a clad film 22 consisting of an upper clad film 22b and a lower clad film 22a, and a core film 21 formed on a substrate 23, the core film 21 is a core glass film containing one or more kinds of oxides selected from Bi<SB>2</SB>O<SB>3</SB>, Sb<SB>2</SB>O<SB>3</SB>, PbO, SnO<SB>2</SB>and TeO<SB>2</SB>by ≥35 mass% in total, and having a thickness of 0.3 to 10 μm, and the core glass film 21 is subjected to dry etching in a gaseous mixture atmosphere consisting mainly of gaseous argon, and to which a gaseous fluoride of 5 to 22% in a flow rate ratio is added with a W-Si alloy film comprising 25 to 65% W as a mask, so as to be patterned. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a glass fine processing method and a glass optical waveguide manufacturing method.

For the purpose of optical amplifiers used in the field of wavelength division multiplex optical communication (WDM) optical communication, research and development of glass fibers having cores doped with rare earth elements have been actively conducted. However, there is a problem that it is difficult to obtain a desired transmission capacity and it is difficult to reduce the size, and an optical fiber using an Er-doped Bi ₂ O ₃ glass core (for example, JP 2001-102661), and an optical waveguide using an optical amplification core made of the same glass on a substrate has been proposed and developed.

A silica-based glass waveguide is generally known as the glass waveguide. As a method for forming a fine waveguide pattern on quartz glass, a dry etching technique is used, and patterning is usually performed using a resist as a mask. That is, dry etching is performed using a resist pattern formed by applying, pattern exposing, developing and removing a resist on a quartz glass film to be finely processed as it is.
The manufacturing method will be described with reference to FIG. In FIG. 4, a clad film 12 is first formed on a substrate 11 made of quartz glass or Si (FIG. 4A), and then a core film 13 of 5 to 10 μm is formed on the clad film 12 (FIG. b)). 4C, a resist 14 is uniformly applied on the core film 13, and the core circuit pattern is exposed and developed with a mask aligner to generate a resist pattern to which the circuit pattern is transferred (see FIG. 4C). FIG. 4 (d)). Using the resist pattern as a mask, the core film is etched by reactive ion etching as shown in FIG. 4E, and then the resist is removed, and the clad film 15 is placed on the core to produce an optical waveguide ( FIG. 4 (f)).

  When a waveguide, diffraction grating, or the like is formed on quartz glass by fine processing, if the etching depth is as deep as 5 to 10 μm, it takes a long time during the etching. However, a metal film such as Ni or Cr may be used in place of an organic resist (for example, Japanese Patent Laid-Open No. Hei 6-27338). No., JP 2000-171650 A, JP 2000-75117 A). That is, dry etching of the core layer is performed using a patterned Ni or Cr metal mask instead of the patterned resist. The metal mask film is subjected to dry etching of the core film, and then the mask film is removed by a wet process using a dedicated etching solution. Finally, the clad film is placed on the core to produce an optical waveguide. The reason why the Ni or Cr mask is removed by the wet process is that it cannot be removed by dry etching.

  In spite of the increased number of processes compared to the resist mask in this manner, the metal film mask is used because it is difficult to form a thick film even if the resist thickness is increased in order to prevent disappearance of the mask. This is because there is a problem that the dimensional accuracy of the mask pattern is deteriorated, or that it is difficult to perform high-precision fine processing because it is easily deformed and altered by long-time etching.

One or more oxides selected from the group consisting of Bi ₂ O ₃ , Sb ₂ O ₃ , PbO, SnO ₂ and TeO ₂ , such as Er-doped Bi ₂ O ₃ based glass used for an optical amplification core of an optical waveguide When a dry etching is performed using a resist as a mask on a glass film containing a total of 35% or more in terms of mass percentage (hereinafter referred to as a Bi ₂ O ₃ other-containing glass film), the side wall of the core pattern is not smooth. A new problem has occurred. This is because the reaction product when quartz glass is dry-etched has high volatility and is quickly discharged out of the etching system, whereas it is dry-etched in the case of a glass film containing Bi ₂ O _{3 and} others. In this case, it is considered that the components of the glass film react with the resist to produce an organic metal having poor volatility, which reattaches to the side wall of the core and the peripheral portion to cause surface roughness. If a smooth core side wall cannot be obtained, a fatal problem that signal light scatters at the interface between the core and the clad and the propagation loss increases when the waveguide is used is difficult to put into practical use.

Although it is conceivable to use a metal film such as Ni or Cr in place of the organic resist, the glass film containing Bi ₂ O _{3 and the} like is much lower in chemical durability than quartz glass and is damaged by the etching solution. Therefore, the mask cannot be removed by a wet process. Therefore, metals such as Ni and Cr cannot be used as the mask film.

A film made of Si or an alloy of Si and W can be removed by dry etching, and may be used as a metal mask other than Ni and Cr in fine processing of quartz glass (for example, Japanese Patent Laid-Open No. 3-284707, Japanese Patent Laid-Open No. 10-311922 and JP 2001-66450 A). Therefore, there is a possibility that it can be applied as a mask film to microfabrication of Bi ₂ O _{3 and} other containing glass films. In the publications of Japanese Patent Application Laid-Open Nos. 2002-029635 and 2002-066943, Ni, Cr and It is listed as a mask film that can be applied to the core glass film containing Bi ₂ O ₃ and others. However, they are merely listed here, and no details are given, including their problems and effects, or optimal composition.

A refractory metal film such as Si or W generally has a large film stress. If the adhesion to the base is insufficient, the film does not function as a mask due to peeling due to film stress or cracks in the film. Since the constituent elements of quartz glass are Si and O, considering the bonding with Si, which is a constituent element of W-Si alloy, the alloy film of W and Si has a high affinity with the base of quartz glass and it is easy to obtain adhesion. However, it is expected that the glass containing Bi ₂ O _{3 and} others containing SiO ₂ is less compatible with quartz glass because of its lower SiO ₂ content than quartz glass, and the adhesion is expected to be weak. Is concerned.

JP 2001-102661 A Japanese Patent Laid-Open No. 6-27338 JP 2000-171650 A JP 2000-75117 A JP-A-3-284707 Japanese Patent Laid-Open No. 10-311922 JP 2001-66450 A JP 2002-029635 A JP 2002-066943 A

When glass or a glass film containing at least one of Bi ₂ O ₃ , Sb ₂ O ₃ , PbO, SnO ₂ and TeO ₂ is subjected to patterning using dry etching and a resist as a mask, it is volatile during dry etching. There is a problem in that a low organic metal is generated and reattaches to the periphery of the pattern, and the surface roughness becomes large, so that a smooth surface cannot be obtained on the side wall or the peripheral portion of the pattern, that is, smooth patterning cannot be performed. Therefore, when the glass is used for the core glass film of the glass optical waveguide, the surface roughness of the core side wall is increased, and light scattering occurs at the interface between the core and the clad, resulting in a problem of increased propagation loss. .

The present invention solves the above-described problems of the prior art, and finely patterns a glass containing at least one of Bi ₂ O ₃ , Sb ₂ O ₃ , PbO, SnO ₂ and TeO ₂ by dry etching. It aims at providing the processing method and the method of implement | achieving a glass optical waveguide with little core side wall roughness.

In order to solve the above-mentioned problems, the present invention provides a total of 35 oxides in terms of mass percentage of one or more oxides selected from the group consisting of Bi ₂ O ₃ , Sb ₂ O ₃ , PbO, SnO ₂ and TeO _2. A glass microfabrication method comprising a glass film made of the glass on a substrate, and having a composition of 25 to 60% in terms of atomic percent of W with respect to the total of W and Si. There is provided a glass fine processing method characterized in that an alloy film of Si and Si is laminated and patterned by dry etching using this as a mask. In this case, the dry etching is preferably performed by a magnetic neutral line discharge plasma etching method in a mixed gas stream containing argon gas as a main component and 5 to 22% fluoride gas in a flow rate ratio. .

Further, it is a method for producing a glass optical waveguide provided with the glass film as a core, wherein a core glass film made of the glass film is formed on a substrate, and the atomic percentage of W with respect to the total of W and Si is 25 to 60%. A method for producing a glass optical waveguide comprising a step of forming a core by laminating an alloy film of W and Si having the composition as described above and patterning by dry etching using the alloy film as a mask provide. The core glass film is dry-etched by using a magnetic neutral discharge plasma etching method in a mixed gas stream containing argon gas as a main component and 5 to 22% fluoride gas in a flow rate ratio. It is preferable that the core glass film contains Bi ₂ O ₃ in terms of mass percentage in total of 35% or more, and more preferably a core glass film containing at least one of Er and Tm. .

According to the production method of the present invention, one or more oxides selected from the group consisting of Bi ₂ O ₃ , Sb ₂ O ₃ , PbO, SnO ₂ and TeO ₂ were contained in a total of 35% or more in terms of mass percentage. The glass and the glass film can be patterned without causing the surface roughness of the peripheral portion of the side wall of the pattern.

Thereby, a glass containing a total of 35% or more of one or more oxides selected from the group consisting of Bi ₂ O ₃ , Sb ₂ O ₃ , PbO, SnO ₂ and TeO _{2 in} terms of mass percentage, particularly Bi ₂ O _With respect to a glass optical waveguide using as a core glass containing a total of 35% or more in terms of mass percentage ₃ , it has become possible to produce a low-loss optical waveguide with a smooth core side surface and less signal light scattering.

  The glass optical waveguide produced by the production method of the present invention is suitable for an optical amplification waveguide, nonlinear optical waveguide, etc. in a wavelength band of 0.4-2 μm, for example, signal light of C band (1530-1565 nm) A light having a wavelength of 1.45 to 1.64 μm can be amplified and a compact optical waveguide can be obtained.

<Method for forming substrate and glass film>
The glass for performing microfabrication of the present invention may be a glass film formed on a substrate by various methods, or may be a glass substrate itself.

The substrate preferably has a Young's modulus of 50 GPa or more. This is because when the Young's modulus of the substrate is low, when stress is generated in the film formed on the substrate, the stress causes warping or deformation, and the waveguide shape is likely to deviate from the design value. Examples of such substances include crystals such as Si, GaAs, Al ₂ O ₃ , MgO, and sapphire, and glasses such as quartz glass, soda lime silica glass, and alkali-free glass.
The material of the substrate is not limited to the material exemplified above, but during the series of steps, the core glass film is annealed or other elements are formed on the same substrate. In the case where a high temperature processing step is included such as necessary, it is necessary to have heat resistance to withstand it.

  The shape of the substrate in the present invention is not limited, but the surface on which the glass thin film is formed is typically a flat surface. Typically, the substrate is a rectangular substrate having a size and shape of 2 mm × 10 mm to 200 mm × 200 mm, and a circular substrate having a diameter of 50 to 203.2 mm, and has a thickness of 0.3 to 2 mm. The thickness of the glass film is typically 0.3 to 10 μm, but is not limited thereto.

  As a means for forming a glass film on the substrate, physical vapor condensation (PVD) or chemical vapor condensation is used. Examples of physical vapor condensation methods include sputtering, laser ablation, electron beam evaporation, and vacuum evaporation, and examples of chemical vapor condensation include plasma CVD and MOCVD.

  When producing a glass thin film having 4 or 5 components, it is preferable to use a sputtering method. When a film is formed by sputtering, the composition of the film may not match the target composition. In that case, it is desirable to use a target whose composition is adjusted so as to obtain a desired film composition.

  For example, the target is prepared by mixing powders of constituent oxides at a desired composition ratio, dry-mixing with a rough machine, melting in an electric furnace heated to 1150 ° C., and then flowing out onto a stainless steel plate Is processed into a desired thickness and outer dimensions, and bonded to the backing plate using indium or the like. In addition, a material obtained by simply mixing oxide powder without being melted in an electric furnace or a material obtained by pulverizing glass melted in an electric furnace may be sintered and molded by a method such as hot pressing.

<Composition of glass film>
The glass film to be microfabricated in the present invention is one or more oxides selected from the group consisting of Bi ₂ O ₃ , Sb ₂ O ₃ , PbO, SnO ₂ and TeO ₂ , more preferably Bi _2. It has a composition containing 35% or more of O ₃ in terms of mass percentage. More preferably, essentially Bi ₂ O ₃ 35-90%, SiO ₂ 2-40%, Ga ₂ O ₃ 0-55%, Al ₂ O ₃ 0-50%, Er ₂ O ₃ 0-10%, tm ₂ O _{3 0~10%,} is preferably a _Yb 2 O 3 _0~10% a composition. Moreover, you may contain another component in 25% or less in total, Preferably it is 15% or less of range.

Bi ₂ O ₃ , Sb ₂ O ₃ , PbO, SnO ₂ and TeO ₂ are components for increasing the refractive index, and at least one of these five components must be contained. Bi ₂ mass percentage content of O ₃ (hereinafter, simply referred to in accordance with this or less for the content of components other than _.BI 2 _{O 3,} referred to as the content of _{Bi 2 O 3.), Sb} 2 O 3 When the total of the content of PbO, the content of PbO, the content of SnO _{2 and} the content of TeO ₂ is less than 35%, the optical amplification factor or the nonlinearity decreases. The total is preferably 90% or less. If it exceeds 90%, vitrification becomes difficult.

When the method of the present invention is applied to the production of optical amplification waveguides, nonlinear optical waveguides and the like, it is preferable to contain Bi ₂ O ₃ in an amount of 35 to 90%. If it is less than 35%, the optical amplification factor or non-linearity decreases. More preferably, it is 60% or more. If it exceeds 90%, vitrification becomes difficult. More preferably, it is 85% or less.

Although SiO ₂ is not essential, it is preferred to contain in order to increase the glass stability, the content thereof is more preferably 2 to 40%. If it is less than 2%, the effect of stabilizing the glass is small. More preferably, it is 3% or more. If it exceeds 40%, the refractive index becomes small and the optical amplification factor or nonlinearity may be lowered. More preferably, it is 15% or less.
Ga ₂ O ₃ is not essential, but may be contained up to 55% in order to enhance thermal stability. If it exceeds 55%, crystallization tends to occur.
Al ₂ O ₃ is not essential, but may be contained up to 50% in order to enhance thermal stability. If it exceeds 50%, crystallization tends to occur.

Er ₂ O ₃ and Tm ₂ O ₃ are not essential as mere glass components, but it is necessary to contain one or both of them when optical amplification is performed. When either Er ₂ O ₃ or Tm ₂ O ₃ is contained alone, its content, and when both are contained, the total content thereof is 0.01 to 10% is preferable. On the other hand, if it exceeds 5%, concentration quenching occurs and the optical amplification factor tends to decrease, so it is more preferably 0.01 to 5%. More preferably, it is 0.1 to 2%.
Yb ₂ O ₃ is not essential, but may be contained up to 10% in order to suppress concentration quenching or in combination with Er ₂ O ₃ or Tm ₂ O ₃ to increase the light amplification factor. If it exceeds 10%, vitrification becomes difficult. More preferably, it is 0.1 to 5%.

The composition of the core glass film of the optical amplification waveguide is typically Bi ₂ O ₃ 40-85%, SiO ₂ 2-40%, Ga ₂ O ₃ 5-25%, Al ₂ O ₃ 0-5%, Er ₂ O ₃ and total _0.01% to _10% of the _Tm 2 _{O 3,} a composition consisting essentially of _Yb 2 O 3 _0~10%. Moreover, you may contain another component in 25% or less in total, Preferably it is 15% or less of range.
Crystals are not precipitated in the glass or glass film of the present invention. That is, no diffraction peak is observed in the X-ray diffraction pattern.

<Glass film or glass patterning>
A mask film made of an alloy of W and Si is formed on the glass film. As a method for forming the mask film, a sputtering method is preferably used, but other film forming methods can also be used. Subsequently, a resist film is formed on the mask film by a spin coat method or the like, and a desired pattern is exposed and developed by irradiating with ultraviolet rays to form a desired pattern on the resist film. Using this resist pattern, the mask film is patterned by dry etching, and then the resist film is removed by dry etching (ashing treatment) using oxygen gas or by wet removal using a stripping solution to obtain a desired pattern. A formed mask is obtained.

The composition of the mask film is 25 to 60% in terms of atomic% of W with respect to the total of W and Si.
When the W content exceeds 60 atomic%, the adhesion between the mask film and the glass film becomes insufficient, and the film is peeled off from the substrate or cracked in the film due to the stress of the mask film. There is a fear. Moreover, since the tungsten bullion is expensive, the material cost increases, which is not preferable in terms of cost.
If the W amount is less than 25 atomic%, the selection ratio, that is, the ratio of the etching rate between the glass film and the mask film is small, so that the amount of wear by which the mask film is etched during patterning of the glass film increases. For this reason, it is necessary to increase the thickness of the mask film, which causes a problem that it takes a long time to form the mask film and the material cost increases due to the thick film.
The selection ratio is preferably 2.5 or more. More preferably, it is 3 or more.

  When forming the mask film made of the alloy of W and Si by sputtering, the purity of the target used is preferably 99.5% or more. If an element that is difficult to dry-etch is included as an impurity, there is a possibility that glass patterning cannot be performed smoothly and as designed. More preferably, it is 99.9% or more.

The mask film formation by sputtering is preferably performed in an argon gas, but there is no problem if it is in an inert gas. When an oxidizing gas is mixed, the alloy is oxidized, and when the glass film is dry-etched, the mask film is etched and wear increases, and a desired selectivity may not be obtained. The purity of the gas used is preferably 99.995% or more. More preferably, it is 99.999% or more.
The film forming pressure is preferably 0.2 to 10 Pa. If the pressure is less than 0.2 Pa, the plasma tends to become unstable, or the film stress tends to increase and the film tends to peel off. If it exceeds 10 Pa, the film quality is deteriorated, and the wear of the mask film is increased, so that a desired selection ratio may not be obtained.

Sputtering is preferably DC sputtering rather than RF sputtering. This is because DC sputtering is less prone to film peeling. Further, the input power density (power applied to the target size) is preferably 2.5 to 7 W / cm ² . If it is less than 2.5 W / cm < ² >, the time for obtaining a desired film thickness will become very long, and productivity will be inferior. On the other hand, if it exceeds 7 W / cm ² , abnormal discharge is likely to occur, and pinholes are generated in the mask film, which tends to cause patterning defects.
The substrate temperature when forming the mask film is preferably in the range from room temperature to 300 ° C. When heated to 300 ° C. or higher, film peeling is likely to occur during the cooling process.

  The thickness of the mask film is inevitably determined by the processing depth and selectivity of the glass to be dry-etched. There is a tendency that patterning defects are likely to occur due to acceleration of wear due to etching of the mask material. On the other hand, if the thickness of the mask film exceeds 3 μm, the resist thickness required for patterning the mask film tends to be large and patterning as designed tends to be difficult. Therefore, 0.1 to 3 μm is preferable.

The mask film is dry-etched by reactive ion etching using chlorine or fluoride gas such as Cl ₂ , CF ₄ , CHF ₃ , C ₃ F ₈ , C ₄ F ₈ , NF ₃ and SF _6. Reactive Ion Ethching, Reactive Ion Beam Etching, Inductively Coupled Plasma Etching (hereinafter referred to as ICP etching), Magnetic Neutral Discharge Etching (Neutral Loop Disch etching) Etc.).
Subsequently, desired patterning is performed on the glass film or glass by dry etching.

The glass film or glass is preferably etched by NLD etching in a mixed gas atmosphere of fluoride gas such as CF ₄ , CHF ₃ , C ₃ F ₈ , and C ₄ F ₈ and Ar gas. At this time, the flow rate ratio of the fluoride gas to the total flow rate of the fluoride gas and the Ar gas is preferably 5 to 22%. If the flow rate ratio of the fluoride gas is larger than 22%, the number of particles may increase and light scattering may be increased when the optical waveguide is formed, or the dry etching rate may be decreased. On the other hand, if it is less than 5%, streaky roughness is generated on the side surface subjected to dry etching, which may cause light scattering when used as an optical waveguide.

As an example of the conditions for dry etching of the glass or glass film, the apparatus used: plasma etching apparatus NLD500 manufactured by Nippon Vacuum Co., Ltd., Ar gas and C ₃ F ₈ gas flow rates of 45 cm ³ / min in terms of standard state, respectively. 5 cm ³ / min, pressure is 0.2 Pa, antenna power is 1200 W, bias power is 250 W, the current of three neutral magnetic field generating coils in the longitudinal direction of the chamber is 10 A, 16.7 A, 10 A from above, and the substrate temperature is 20 ° C. Illustrated. Under this condition, the glass film having a thickness of 4 μm could be etched in 15 minutes. Of course, the conditions listed here are merely examples, and the present invention is not limited to these.

After patterning the glass or glass film, the mask film is removed by dry etching using a chlorine-based or fluoride-based gas. In dry etching, chlorine such as Cl ₂ , CF ₄ , CHF ₃ , C ₃ F ₈ , C ₄ F ₈ , NF ₃ , and SF ₆ is formed by reactive ion etching, reactive ion beam etching, ICP etching, NLD etching, and the like. In a gas atmosphere of a system or fluoride system. Oxygen may be added to the etching gas.

<Formation of glass optical waveguide>
By the microfabrication method of the method of the present invention, it is possible to form a glass optical amplification waveguide used for WDM optical communication by patterning a glass film containing Bi ₂ O _{3 and} others to form a core. In this optical amplification waveguide, signal light having a wavelength of, for example, 1.45 to 1.64 μm that propagates through the core glass in the presence of excitation light is amplified. The optical waveguide formed by the microfabrication method of the present invention is not limited to this, and may be applied to the formation of a nonlinear optical waveguide, for example.

The refractive index n ₁ of the glass film serving as the core is preferably 1.7 or more. This is because the above-described light amplification by the glass is caused by stimulated emission of light of the signal light wavelength, which is induced by the excitation light, and the gain coefficient is larger as the refractive index is larger. If the refractive index is less than 1.7, the optical gain or nonlinearity may be reduced. More preferably, it is 1.8 or more. Moreover, it is typically 2.3 or less.

The clad is not particularly limited as long as it can confine light in the core, but the refractive index n ₂ of the clad is determined when the refractive index difference n ₁ -n ₂ between the core and the clad is Δn.
0.0003 ≦ Δn / n ₁ ≦ 0.1
Is preferably satisfied. That is, if Δn / n ₁ is less than 0.0003, it becomes difficult to confine light in the core. More preferably, it is 0.001 or more, Most preferably, it is 0.003 or more. If it exceeds 0.1, it becomes difficult to propagate light in a single mode. More preferably, it is 0.08 or less, Most preferably, it is 0.05 or less.

When the core is in the typical composition range described above, the cladding is preferably in the same range as the composition range except that it does not contain any of Er ₂ O ₃ and Tm ₂ O ₃ . If the composition range is different between the core and the clad, the glass transition point, expansion coefficient, softening point, etc. will be different, so thermal stress will be generated in the process of heating and cooling, film peeling will occur in the process of producing the waveguide, and residual stress May occur. Of course, the clad is not limited to the composition range as long as the thermal properties are not greatly different and the refractive index can be adjusted within the range.

  In the optical amplification waveguide, the core is formed on the lower clad, and after the core is finely processed by the method of the present invention, the upper clad is formed thereon. The thicknesses of the core and the cladding are preferably 0.3 to 10 μm and 8 to 60 μm, respectively. Typically, the thickness of the lower cladding is 4 to 30 μm, and the thickness of the upper cladding is 4 to 30 μm. It is not limited to.

  As a method for forming the lower clad film and the upper clad film, various methods mentioned in the method for forming the core glass film can be applied. As with the core glass film, glass having 4 or 5 or more components. Sputtering is preferred because it is a film.

  That is, on the substrate, a first film to be a base cladding film (corresponding to the glass thin film 22a in FIG. 1) is first formed by sputtering, and then a first film to be a core (corresponding to the core 21 in FIG. 2). Two films are formed. At this time, a target whose composition is adjusted so as to obtain a desired film composition is used. In order to protect the core film from damage due to the dry etching process, an upper cladding film described later may be formed as a protective film on the core. When using a protective film, the thickness is preferably 25 to 1000 nm. If it is thicker than 1000 nm, the thickness of etching the core film and the protective film by dry etching becomes thick, and the dry etching time is greatly increased. If it is thinner than 25 nm, the effect may not be sufficiently obtained when it is necessary to protect the core film from damage.

A mask film made of an alloy of W and Si is formed on the second film or the protective film.
As a method for forming a mask film made of an alloy of W and Si, a sputtering method is preferably used. Subsequently, a resist film is formed on the mask film by using a spin coat method, and a desired pattern is formed on the resist film by irradiating and developing an ultraviolet ray using a photomask having a desired pattern. The mask is formed using the resist pattern. The film is dry-etched, and finally, a mask formed in a desired pattern is obtained through dry etching (ashing treatment) using oxygen gas or removal of the resist film by wet removal using a stripping solution.

The mask film is dry-etched using reactive gases such as Cl ₂ , CF ₄ , CHF ₃ , C ₃ F ₈ , C ₄ F ₈ , NF ₃ , SF _6, or other chlorine-based or fluoride-based gases. Etching, reactive ion beam etching, ICP etching, NLD etching, or the like can be used.
Subsequently, the second film is dry-etched in the same manner as in the etching of the glass film described above to form a desired core pattern. When the protective film is used, the protective film is patterned together by dry etching.

Subsequently, the mask film is removed by dry etching in the same manner as in the etching of the glass film described above, and an upper cladding film (corresponding to the glass thin film 22b in FIG. 2) is formed by sputtering. After forming the upper cladding film, annealing may be performed in an oxygen atmosphere.
If necessary, other elements are formed on the substrate and finally cut to a desired dimension.

The present invention will be described more specifically with reference to examples. However, the following description does not limit the present invention.
The composition shown by mass percentage display in Table 1 is a powdery reagent Bi ₂ O ₃ (purity 99.999%, particle size 20 μm) manufactured by High Purity Chemical Laboratory, SiO ₂ (purity 99.9%, particle size 4 μm). , Ga ₂ O ₃ (purity 99.9%), Al ₂ O ₃ (purity 99.9%), B ₂ O ₃ (purity 99.9%), La ₂ O ₃ (purity 99.9%), Er ₂ O ₃ (purity 99.9%) and CeO ₂ (purity 99.9%) were mixed and then dry-mixed with a cracker and dissolved in an electric furnace heated to 1150 ° C., then on a stainless steel plate The glass having a diameter of 101.6 mm was obtained. The obtained glass was ground to a thickness of 3 mm, and then bonded to a sputtering backing plate using indium as an adhesive to produce sputtering targets T1, T2, and T3.

  The glass film formed using this target was patterned by dry etching and evaluated. Examples 1 and 2 are examples, and examples 3, 4, and 6-8 are comparative examples.

[Example 1]
The target T1 was sputtered under the following conditions to form a glass film 32 having a thickness of 4 μm on a soda lime silica glass circular substrate 33 (thickness 1 mm, diameter 76.2 mm). That is, the substrate temperature was 20 ° C., argon and oxygen respectively flow 30 cm ³ / min calculated in the standard state as a sputtering gas, 0.75 cm ³ / min, the pressure is 0.3 Pa, put RF power 100W, sputtering time is 24 Sputtering was performed under the conditions of time. When the X-ray diffraction pattern of the glass film F1 formed on the substrate was measured, no diffraction peak was observed.
Next, a mask film 31 having a thickness of 1 μm was formed on the glass film 32 by using a W ₆ Si ₄ target having a diameter of 101.6 mm. That is, sputtering was performed under the conditions of a substrate temperature of 20 ° C., argon as a sputtering gas at a flow rate of 10 cm ³ / min in terms of a standard state, a pressure of 2 Pa, an input DC power of 300 W, and a sputtering time of 100 minutes.

  One of several samples prepared was extracted from the process, and the peel strength between the mask film and the underlying glass film was measured. The peel strength was determined from the critical load value at which the mask film was broken by scratch by performing a scratch test using an ultra-thin scratch tester (Reska, CSR-02 type tester). As a result, a peel strength of 60 mN was obtained.

Next, a 2.4 μm-thick positive resist film was formed on the mask film 31 by using a spin coating method. The positive resist film is calcined on a hot plate at 96 ° C., and then irradiated with ultraviolet rays having a wavelength of 436 nm using a mask aligner. A linear shape having a width of 3 to 8 μm and a length of 50 to 76 mm is formed on the positive resist film. A pattern in which 30 core patterns were formed at a pitch of 125 μm was formed. The ultraviolet-irradiated portion of the positive resist film was removed with a developer, and then dry etching was performed by ICP etching. In the dry etching, the flow rates of CHF ₃ gas and SF ₆ gas are 25 cm ³ / min, 5 cm ³ / min, pressure 0.5 Pa, antenna power 800 W, bias power 20 W, substrate temperature 20 ° C. Patterning of the mask film 31 was performed for 8 minutes under the conditions.

Next, after removing the resist from the mask film 31 with a stripping solution, an ashing process was performed by inductively coupled plasma under the following conditions. That is, ashing was performed for 5 minutes under the conditions of a substrate temperature of 20 ° C. and oxygen as an ashing gas in terms of standard conditions of 20 cm ³ / min, pressure of 1 Pa, antenna power of 300 W, and bias power of 10 W, and the resist was removed. .

Next, dry etching was performed using a magnetic loop discharge (Neutral Loop Discharge) plasma etching apparatus NLD500 to pattern the glass film F1. The dry etching was performed in a mixed gas stream in which fluoride gas was added to Ar gas at a flow rate ratio of 10%. That each flow rate of the Ar gas and _C 3 _{F 8} gas is 45cm ³ / min calculated in the standard state was set to 5 cm ³ / min. At that time, the pressure is 0.2 Pa, the discharge power is antenna power 1200 W, bias power 250 W, the current of three neutral magnetic field generating coils in the longitudinal direction of the chamber is 10 A, 16.7 A, 10 A, the substrate temperature from the top. The temperature was 20 ° C. The dry etching process was performed for 15 minutes under the above conditions. SEM observation of the core cross section after dry etching was performed. Compared with the comparative example, there was no deposit around the core side wall, and the etching was performed smoothly. FIG. 3 is a conceptual diagram overlooking the core cross section.

[Example 2]
The target T2 was sputtered under the same conditions as in Example 1 to form a glass film 42 having a thickness of 4 μm on the soda lime silica glass substrate 43. Next, a mask film 41 having a thickness of 1 μm was formed on the glass film 42 by sputtering under the same conditions except that a WSi ₂ target was used instead of the W ₆ Si ₄ target of Example 1.

Next, a positive resist was applied on the mask film 41 under the same conditions as in Example 1, exposed and developed to form a linear core pattern, and the mask film 41 was patterned by ICP etching. The dry etching, CHF ₃ 20 cm ³ / min gas and SF ₆ gas flow rate calculated in the standard state, respectively, 10 cm ³ / min, the pressure is 0.5 Pa, the antenna power 800 W, bias power 20W, substrate temperature 20 ° C., of The treatment was performed for 8 minutes under the conditions.

Subsequently, after removing the resist from the mask film 41 under the same conditions as in Example 1, the glass film 42 was NLD etched under the same conditions as in Example 1 using the patterned mask film 41. When the SEM observation of the core cross section after etching was performed and compared with the comparative example, there was no deposit around the side wall, and the etching was smooth.
In the same manner as in Example 1, immediately after forming the mask film, one of several prepared samples was extracted from the process and subjected to peel strength measurement. As a result, the peel strength was 200 mN.

[Example 3]
A target T3 was sputtered under the same conditions as in Example 1 to form a glass film 52 having a thickness of 4 μm on a soda lime silica glass substrate 53. Next, a mask film 51 having a thickness of 1 μm was formed on the glass film 52 by sputtering under the same conditions except that a Si target was used instead of the W ₆ Si ₄ target of Example 1.

Next, a positive resist was applied onto the mask film 51 under the same conditions as in Example 1, exposed and developed to form a linear core pattern, and the mask film 51 was patterned by ICP etching. The dry etching was performed for 10 minutes under the conditions of a Cl ₂ gas flow rate of 100 cm ³ / min in terms of a standard state, a pressure of 2.7 Pa, an antenna power of 1000 W, a bias power of 50 W, and a substrate temperature of 20 ° C.

  Subsequently, after removing the resist from the mask film 51 under the same conditions as in Example 1, the glass film 52 was NLD etched under the same conditions as in Example 1 using the patterned mask film 51. When the SEM observation of the core cross section after the etching was performed and compared with the comparative example, there was no deposit around the side wall and the etching was smooth.

[Example 4]
The target T1 was sputtered under the same conditions as in Example 1 to form a glass film 62 having a thickness of 4 μm on the soda lime silica glass substrate 63. Next, a positive resist 61 is applied on the glass film 62 under the same conditions as in Example 1, and the resist is processed into a linear core pattern by exposure and development. The film 62 was NLD etched.
When SEM observation of the core cross-section after dry etching was performed, the side wall of the core and the entire peripheral surface were uneven, and surface roughness occurred. FIG. 3 is a conceptual diagram overlooking the core cross section.

  In Examples 1 to 3, the ratio of these etching rates from the depth at which the glass film and the mask film were etched by NLD etching, obtained by SEM observation of the core cross section after the NLD etching of the glass film, The selectivity was determined. Here, the etching amount of the mask film was obtained from the difference between the mask thickness measured in advance and the mask thickness after NLD plasma etching.

  Table 2 summarizes the selectivity for each mask film material and the peel strength described in Examples 1-3. As can be seen from this, the peel strength decreases as the W content of the mask film increases. If the W content exceeds 60%, the peel strength is low, and there is a possibility that the mask film may peel off or crack. In addition, since the selection ratio is lower than 25% or Si, the thickness of the mask material needs to be increased, and it takes a long time to form and etch the mask, resulting in decreased productivity and patterning accuracy. There is a possibility that problems such as lowering may occur.

  In addition, when a glass film is formed by sputtering in the above example, a glass film sample is simultaneously prepared on a platinum substrate, and the obtained film is dissolved with an acid and quantitatively analyzed by ICP emission spectroscopy. The composition of was analyzed. Table 3 shows the results of the composition mass percentage display of the glass films obtained when the target compositions are T1 and T3, respectively. As can be seen from this, a glass film having almost the same composition as the target composition is obtained.

[Examples 5 to 9]
Table 3 summarizes the results of examining the effect of the etching gas composition when performing NLD etching on the core glass film by changing the flow rates of C ₃ F ₈ gas and argon gas in Example 1.
When the flow rate ratio of C ₃ F ₈ gas in the total flow rate of C ₃ F ₈ gas and argon gas is reduced from 10% of the condition of Example 1, the core after NLD etching is less than 4.0%. Streaks appear on the side walls. This streaky roughness is undesirable because it causes scattering of the optical waveguide.

Next, the C ₃ F ₈ gas flow rate ratio is increased from 10%. If it exceeds 25%, the amount of redeposits on the core side wall and the periphery of the side wall increases, and a lot of deposits are generated on the chamber wall of the apparatus. did. The rough side wall of the core is not preferable because it causes scattering loss of the optical waveguide. Further, the deposit on the chamber wall of the apparatus causes particle defects and also causes an increase in light scattering, which is not preferable. Further, when the C ₃ F ₈ gas flow rate ratio was increased, the etching rate decreased, and the core glass film was hardly etched under the condition of 90%.

  The glass optical waveguide produced by the production method of the present invention is suitable for an optical amplification waveguide, a nonlinear optical waveguide, etc. in a wavelength band of 0.4 to 2 μm.

It is a conceptual diagram of the cross section of the optical waveguide of this invention. It is the schematic diagram which looked down at the cross section after the core glass film etching by the example 1 of this invention. It is the schematic diagram which looked down at the cross section after the core glass film etching by the example 2 of this invention. It is sectional drawing which shows the preparation methods of a general optical waveguide.

Explanation of symbols

11: Substrate 12: Underlying clad film 13: Core film 14: Resist film 15: Upper clad film 21: Core 22: Clad 22a: Lower clad film 22b: Upper clad film 23: Glass substrate 31: Mask 32: Core glass film 33: Substrate 51: Mask 52: Cocoa glass film 53: Glass substrate 61: Mask 62: Core glass film 63: Glass substrate

Claims (6)

A glass microfabrication method containing one or more oxides selected from the group consisting of Bi ₂ O ₃ , Sb ₂ O ₃ , PbO, SnO ₂ and TeO ₂ in a mass percentage display of a total of 35% or more,
A glass film made of the glass is formed on a substrate, and an alloy film of W and Si having a composition of 25 to 65% in terms of atomic percent of W with respect to the total of W and Si is laminated thereon, and this is used as a mask. A method for finely processing glass, characterized in that patterning is performed by dry etching.   The dry etching is performed by a magnetic neutral line discharge plasma etching method in a mixed gas stream containing argon gas as a main component and 5 to 22% fluoride gas in a flow rate ratio. Glass fine processing method. A glass film made of glass containing a total of 35% or more of one or more oxides selected from the group consisting of Bi ₂ O ₃ , Sb ₂ O ₃ , PbO, SnO ₂ and TeO _{2 in} terms of mass percentage is provided as a core. A method of manufacturing a glass optical waveguide,
A core glass film made of the glass is formed on a substrate, and an alloy film of W and Si having a composition of 25 to 60% in terms of atomic percent of W with respect to the total of W and Si is laminated thereon, and this is masked. A method for producing a glass optical waveguide, comprising: a step of patterning by dry etching to form a core.   The dry etching of the core glass film according to claim 3 is a mixed gas in which argon gas is a main component and a fluoride gas having a flow rate ratio of 5 to 22% is added thereto using a magnetic neutral discharge plasma etching method. A method for producing a glass optical waveguide performed in an air current. The method according to core glass film of claim 3 or 4 wherein the glass optical waveguide is a glass containing a total of 35% or more of Bi ₂ O ₃ in mass percentage. The manufacturing method of the glass optical waveguide in which the core glass film of Claims 3-5 contains at least any one of Er and Tm.

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