KR20020048497A - Method of manufacturing planar optical waveguides through negative etching - Google Patents

Abstract

PURPOSE: A fabrication method of a plate-type optical waveguide is provided to select any amorphous material as a material for a core of waveguide by using an engraving etching. CONSTITUTION: After forming a metal mask on a silica glass substrate(210) by a thermal deposition or a sputtering, a waveguide pattern is formed through a lithography processing. At this time, the waveguide pattern has a groove on a defined core region. A groove corresponding to the core of the waveguide is formed by etching the silica glass substrate(210). Then, an amorphous metal oxidation material(221) is filled into the groove formed on the silica glass substrate(210) by performing a sol-gel processing. An amorphous layer(250) having a similar refractive index with the silica glass substrate(210) is deposited on the entire surface of the resultant structure.

Description

Method of manufacturing planar optical waveguides through negative etching

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar optical waveguide fabrication method using intaglio etching. In particular, a planar optical waveguide material which can be used as an optical communication component is a channel oxide in which an amorphous metal oxide is formed on a dielectric substrate such as silicon or silica. It relates to a technique to implement.

1A to 1D are views illustrating a conventional planar optical waveguide manufacturing process. The conventional method most commonly used to produce flat channel waveguides is as follows. First, a film forming process such as flame hydrolysis deposition, chemical vapor deposition, sputtering, and sol-gel coating is applied, as shown in FIG. 1A. Two dense amorphous films 120 and 130 which function as clads and cores are sequentially formed on the substrate 110. In this case, if the substrate material is fused silica, which may serve as a clad with respect to the waveguide core, the lower clad film 120 may be omitted. As described above, after the metal mask 140 is coated on the substrate where the clad and the core film coexist, a process such as thermal deposition or sputtering, a waveguide pattern is formed as shown in FIG. 1B through a general lithography process. Thereafter, a reactive ion etching process is performed to the core film depth to remove portions other than the region corresponding to the waveguide core 131 as shown in FIG. 1C. Finally, the film forming process is repeated to form an amorphous film 150 having a refractive index similar to that of the lower clad on the substrate as shown in FIG. 1D.

Channel waveguides having a square or rectangular cross section of a waveguide core, a passage through which signal light passes, as shown in FIG. 1D, have an upper portion of a waveguide core having a slab shape because the mode confinement effect acts in the vertical direction as well as the horizontal direction. Compared to the ridge or strip-loaded waveguide in which the clad film is present only at the bottom, the transmission loss due to polarization is small. For this reason, channel waveguide structures are preferred in the manufacture of planar optical waveguide devices.

If you want to implement a passive optical device such as a power splitter, a wavelength division multiplexer or a waveguide open lattice elements by using the above-mentioned plate-like optical waveguide manufacturing method, the core layer composition was as in for the silica-based optical fiber SiO ₂ The / B ₂ O ₃ / P ₂ O ₅ / GeO ₂ system is mainly used and this composition is easily etched by a reactive ion etching process using gases such as CF ₄ , C ₂ F ₆ , CHF ₃ . However, in order to manufacture a waveguide for optical signal amplification rather than a low loss passive waveguide, rare earth metals such as Er, Yb, and Nd are commonly added to the core film. However, such an amorphous film to which the rare earth metal is added is a reactive ion etching process. There is a problem that is difficult to etch by.

Therefore, the method of manufacturing a plate-type optical waveguide using an intaglio etching according to the present invention for solving the above-described problems serves as a clad for the waveguide core even when an amorphous material that is difficult to be etched is applied as a material for the core of the plate-type optical waveguide. After forming a groove corresponding to the waveguide core by an etching process on the surface of the substrate capable of etching, the sol-gel process is applied to the groove to fill an amorphous metal oxide, and finally to serve as a clad for the waveguide core. It is an object of the present invention to provide a method for manufacturing a channel waveguide by a simple process of coating an amorphous material.

1A to 1D illustrate a conventional planar optical waveguide manufacturing process, and FIGS. 2A to 2D illustrate a planar optical waveguide manufacturing process according to an embodiment of the present invention.

3A to 3D are views illustrating a manufacturing process of a planar optical waveguide according to another embodiment of the present invention.

※ Explanation of codes for main parts of drawing

210: Silica Glass Substrate

221: waveguide core material

250: amorphous membrane

According to an aspect of the present invention, there is provided a method of manufacturing a plate-type optical waveguide using an intaglio etching method, the method of manufacturing a plate-type optical waveguide device usable as an optical communication component, wherein a metal mask is coated on a surface of a silica glass substrate. A first step of performing a lithography process and then forming a waveguide pattern; Etching the silica glass substrate to form a groove corresponding to the waveguide core in the silica glass substrate; A third step of applying a sol-gel process to the groove formed on the silica glass substrate to fill an amorphous metal oxide; And a fourth step of coating an amorphous film serving as a clad on the amorphous metal oxide.

In addition, a method for manufacturing a planar optical waveguide device usable as an optical communication component, comprising: a first step of forming a thermal oxide film or an amorphous film on a surface of a silicon substrate; A second step of forming a waveguide pattern after performing a lithography process on the thermal oxide film or the amorphous film by coating a metal mask; Etching the thermal oxide film or the amorphous film to form a groove corresponding to the waveguide core in the thermal oxide film or the amorphous film; A fourth step of applying a sol-gel process to the groove formed in the thermal oxide film or the amorphous film to fill an amorphous metal oxide; And a fifth step of coating an amorphous film serving as a clad on the amorphous metal oxide.

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the manufacturing method of the plate-type optical waveguide using the intaglio etching according to the present invention,

2A to 2D are views illustrating a manufacturing process of a flat optical waveguide according to an embodiment of the present invention.

(1) First step

2A is a step of forming a waveguide pattern. First, a metal mask 240 is coated on a surface of a silica glass substrate 210 by a process such as thermal deposition or sputtering, and then a waveguide pattern is formed through a lithography process. In this case, it is to be noted that the etching is performed in the region corresponding to the waveguide core in the subsequent etching process by removing the metal film existing in the region corresponding to the waveguide core.

(2) second stage

FIG. 2B illustrates a process of forming the groove 220 corresponding to the waveguide core. The groove 220 corresponding to the waveguide core is formed by performing a reactive ion etching process on the silica glass substrate 210 on which the waveguide pattern work is completed. Make

(3) the third stage

FIG. 2C illustrates a process of filling the waveguide core material 221 in the groove 220, and applies a sol-gel process, which is one of general film forming processes, to fill the core material.

The reason why the sol-gel process is applied to fill the core material in the groove 220 corresponding to the waveguide core is as follows. In order to fill the grooves corresponding to the waveguide cores having a width and height of several μm with core material, when the hydrohydrolysis deposition method, chemical vapor deposition method, or sputtering method is applied, an amorphous film having a thickness of several μm is formed in the regions other than the grooves. The phenomenon is inevitable, and the thick film thus formed is an obstacle when designing a channel waveguide. However, in the case of applying the sol-gel process, although an amorphous film is formed in a region other than the groove corresponding to the waveguide core, the thickness does not exceed 0.5 μm even if the film forming process is repeated several times. This is because thin films are not an obstacle in the design of channel waveguides.

In the present invention, the following method was used to fill the amorphous core material by applying the sol-gel method to the groove 220 corresponding to the waveguide core formed on the silica glass substrate 210 by the intaglio etching technique. A sol solution for making a core material with a silica glass optical waveguide generally undergoes hydrolysis and condensation reaction by adding H ₂ O to an alcohol solution of tetraethylorthosilicate (TEOS) represented by the chemical formula of Si (OC ₂ H ₅ ) ₄ . It is prepared by adding a compound containing Ge, P, Al, Ti, and other components together with TEOS to increase the refractive index of the waveguide core. In addition, in addition to Ge, P, Al, Ti, and the like, a small amount of chemical substances containing rare earth metals, such as Er, Nd, and Yb, are added when manufacturing a waveguide for amplifying signal light.

In the present invention, the sol solution prepared by the same or similar method as described above is dropped on the silica glass substrate 210 in which the grooves 220 corresponding to the waveguide core are formed and then rotated at a high speed or the silica is added to the sol solution. The sol solution is filled into the grooves 220 by inserting the glass substrate 210 and then re-geling the sol solution. Thereafter, the silica glass substrate 210 in which the gelled core material is present is heat-treated at a high temperature to thermally decompose the gelled core material, and the resulting amorphous metal oxide core material is densified. On the other hand, crystallization may occur in the amorphous metal oxide core material during such a heat treatment process. Since the transmission loss of light increases in the optical waveguide by such crystallization, it is important to search for heat treatment conditions that can suppress crystallization as much as possible.

Through such a series of processes, the dense metal oxide core material in the amorphous state is filled in the groove 220 corresponding to the waveguide core formed by the intaglio etching technique as shown in FIG. 2C. In addition, in order to improve the optical waveguide manufacturing process or improve the characteristics of the manufactured optical waveguide device, a thin film of metal oxide core material existing in a region other than the groove corresponding to the waveguide core may be reacted with a reactive ion etching process or a mechanical polishing process. It can also be removed by.

(4) the fourth step

FIG. 2D illustrates a process of forming an amorphous film 250 on the silica glass substrate 210. The process may be any one of film forming processes such as flame hydrolysis deposition, chemical vapor deposition, sputtering, or sol-gel. By repeating the film formation process by selecting the process, an amorphous film 250 having a refractive index similar to that of the silica glass substrate 210 is formed on the silica glass substrate 210.

3A to 3D are views illustrating a manufacturing process of a planar optical waveguide according to another embodiment of the present invention.

In the method of manufacturing a plate-type optical waveguide using intaglio etching according to the present invention, an optical waveguide may be made using a silicon substrate instead of the silica glass substrate as described in FIG. 2. In order to make an optical waveguide using the silicon substrate, a thermal oxidation layer 340 of silicon having a thickness of several μm or more is present on the surface of the silicon substrate as shown in FIG. 3A, or a hydrohydrolysis deposition method or a chemical vapor deposition method. A dense silica-based amorphous film 340 capable of cladding with respect to the waveguide core should be formed by a film forming process such as a sputtering method or a sol-gel method. By performing a lithography and etching process following a metal mask forming operation on the amorphous film 320 having a thickness of several μm or more, grooves 320 corresponding to the waveguide core are formed as shown in FIG. The sol-gel process described in step 2 is applied to fill the amorphous metal oxide core material 321 as shown in FIG. 3C. Finally, any one of a film forming process such as flame hydrolysis deposition, chemical vapor deposition, sputtering, or sol-gel method is selected, and the amorphous metal oxide core is formed in the groove 320 corresponding to the waveguide core as shown in FIG. 2. By repeating the film forming process on the surface of the silicon-filled material, a dense amorphous film 350 capable of cladding with respect to the waveguide core is formed on the silicon substrate 310 as shown in FIG. 3D. In this case, when the sol-gel method is selected as the film forming process, the sol solution for the waveguide is filled in the grooves 320 corresponding to the waveguide core, followed by the drying process, and immediately after coating the sol solution for the waveguide clad, the drying process and the high temperature. By performing the heat treatment step, repetition of the high temperature heat treatment step can be avoided.

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

As described above, the method of manufacturing a plate type optical waveguide using an intaglio etching according to the present invention has an advantage of selecting an amorphous material that is difficult to etch as well as an amorphous material that can be etched by a reactive ion etching process as a material for the waveguide core. With this advantage, a low loss passive waveguide and a waveguide for signal light amplification can be integrated on the same substrate. In addition, when a silica glass substrate or a silicon substrate having a thermal oxide film having a thickness of several μm or more is used as the substrate, since the substrate hardly bends even after the channel waveguide is finally formed on the substrate, the refractive index anisotropy decreases, thereby polarizing the waveguide. This has the advantage of reducing dependencies.

Claims (9)

In the manufacturing method of a flat plate optical waveguide device usable as an optical communication component, Applying a metal mask to the surface of the silica glass substrate, performing a lithography process, and then forming a waveguide pattern; Etching the silica glass substrate to form a groove corresponding to the waveguide core in the silica glass substrate; A third step of applying a sol-gel process to the groove formed on the silica glass substrate to fill an amorphous metal oxide; And And a fourth step of coating the amorphous metal serving as a clad on the amorphous metal oxide. The method of claim 1, The second step, The method of manufacturing an optical waveguide, characterized in that to use a reactive ion etching during the etching process on the silica glass substrate on which the waveguide pattern is formed. The method of claim 1, The third step, In the sol-gel process, an optical waveguide manufacturing method comprising an aqueous solution or an alcohol solution of metal organic compounds such as an inorganic metal salt or a metal alkoxide as a starting material. . The method of claim 1, The third step, And a reactive ion etching process or a mechanical polishing process is added to remove the amorphous film formed in the region other than the groove corresponding to the waveguide core after completion of the sol-gel process. In the manufacturing method of a flat plate optical waveguide device that can be used as an optical communication component, Forming a thermal oxide film of silicon or an amorphous film based on silica on the surface of the silicon substrate; A second step of forming a waveguide pattern after performing a lithography process on the thermal oxide film or the amorphous film by coating a metal mask; Etching the thermal oxide film or the amorphous film to form grooves corresponding to the waveguide cores in the thermal oxide film or the amorphous film; A fourth step of applying a sol-gel process to the groove formed in the thermal oxide film or the amorphous film to fill an amorphous metal oxide; And And a fifth step of coating the amorphous metal serving as a clad on the amorphous metal oxide. The method of claim 5, The third step, The method of manufacturing an optical waveguide, characterized in that using reactive ion etching during the etching process for the thermal oxide film or amorphous film having the waveguide pattern formed. The method of claim 5, The fourth step, In the sol-gel process, an optical waveguide manufacturing method comprising an aqueous solution or an alcohol solution of metal organic compounds such as an inorganic metal salt or a metal alkoxide as a starting material. . The method of claim 5, The fourth step, And a reactive ion etching process or a mechanical polishing process is added to remove the thermal oxide film or the amorphous film formed in the region other than the groove corresponding to the waveguide core after completion of the sol-gel process. The method of claim 5, The thermal oxidation film or the amorphous film is an optical waveguide manufacturing method, characterized in that the thickness is 5㎛ or more used.