JPH11271549A - Manufacture of optical integrated circuit with outer-surface branching mirror - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an integrated circuit with an outer-surface branching mirror in high precision through a relatively simple manufacturing process. SOLUTION: A method for the manufacture of an optical integrated circuit which has an outer-surface branching mirror on a substrate 10, is provided with a process for forming a polymer optical material film 11 constituting an optical circuit element on the substrate 10, a process for scanning the polymer optical material film 11 two-dimensionally and directly with an electron beam and a process for removing the polymer optical material film in the area where the optical circuit element is not constituted by development. In the electron beam scanning process, the area where the optical circuit element is not constituted is scanned with a temporally constant energy irradiation quantity and the area where the outer-surface branching mirror is expected to be constituted is scanned while the irradiation energy quantity is varied with the time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing an optical integrated circuit, and more particularly to a method for manufacturing an optical integrated circuit having an out-of-plane branching mirror by directly irradiating an electron beam.

[0002]

2. Description of the Related Art An optical integrated circuit in which a polymer film is formed on a substrate and various optical elements such as an optical waveguide and an optical modulator are formed using the polymer film has been put to practical use. In this optical integrated circuit, an optical coupling element such as an out-of-plane branching mirror for making external signal light incident on the optical integrated circuit or transmitting signal light from the optical integrated circuit to another optical element is required. It is.

Conventionally, when an out-of-plane branch mirror is formed as an optical coupling element in an optical integrated circuit, photolithography and etching techniques have been used. That is,
To manufacture an out-of-plane branching mirror, first, an electron beam resist is deposited on a dry plate, an electron beam is irradiated using an electron beam source, and development processing is performed, thereby manufacturing a photomask having a desired pattern. Next, a photoresist, which is a photosensitive material, is formed on the optical waveguide, and the photoresist is irradiated with ultraviolet rays through a photomask, patterned, and developed. Then, etching is performed using the photoresist as a mask, and the core portion of the optical waveguide is shaved to complete a polymer optical waveguide having a branch mirror. In addition, a method of mechanically cutting a polymer using a blade of a dicing saw has been used for manufacturing an out-of-plane branch mirror on a polymer waveguide.

[0004]

In the prior art,
The production of the out-of-plane branching mirror requires a number of steps, which has the disadvantage of complicating the manufacturing process. Further, in the process of the prior art, since a mechanical processing is required, thermally and mechanically weak materials cannot be used. Furthermore, these methods have made it difficult to realize a highly flexible mirror pattern.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method of manufacturing an optical integrated circuit which can solve the above-mentioned drawbacks and can accurately form an optical integrated circuit having an out-of-plane branching mirror in a relatively simple manufacturing process. .

Another object of the present invention is to provide a method of manufacturing an optical integrated circuit having not only a single optical coupling surface but also various types of out-of-plane branching mirrors such as a diffraction grating.

[0007]

According to the method of manufacturing an optical integrated circuit having an out-of-plane branching mirror according to the present invention, an optical integrated circuit having an out-of-plane branching mirror is formed on a substrate. Forming a polymer optical material film, forming the polymer optical material film directly two-dimensionally with an electron beam, and developing the polymer optical material film in an area where an optical circuit element is not formed. A step of removing the material film, and in the electron beam scanning step, an area not forming an optical circuit element is scanned with a temporally constant energy irradiation amount to form an out-of-plane branch mirror. It is characterized in that an area is scanned while changing the irradiation energy amount with time.

The present inventor conducted various experiments and analyzes on the polymer optical material film formed on the substrate. As a result, when the polymer film was irradiated with an electron beam and subjected to thermal development or wet development, It has been found that there is a correspondence between the thickness of the polymer film to be removed and the dose of the irradiated electron beam. In other words, it was found that when the electron beam irradiation amount per unit time was small, it was removed shallowly, and when the electron beam irradiation amount was increased, it was removed from the surface to a deeper position. According to the results of this experiment, by changing the irradiation amount of the electron beam with respect to the area where the out-of-plane branch mirror is to be formed, the mirror surface at an arbitrary angle other than 90 ° with respect to the normal to the substrate is obtained. Can be formed. The present invention is based on such recognition, and irradiates an area in which an optical circuit element such as an optical waveguide or an optical modulator of an optical integrated circuit is not formed with an electron beam having a temporally constant irradiation amount. On the other hand, in the area constituting the out-of-plane mirror, the electron beam irradiation amount is changed with time. In this case, the dose of the electron beam can be changed by changing the scanning speed of the electron beam, or can be changed by keeping the scanning speed constant and changing the dose itself over time. With this configuration, an optical integrated circuit having an out-of-plane branch mirror can be formed by one electron beam irradiation process, and the manufacturing process is further simplified.

An embodiment of a method of manufacturing an optical integrated circuit having an out-of-plane branching mirror according to the present invention is a method of scanning an electron beam by changing the irradiation amount of the irradiated electron beam in a stepwise manner. Out-of-plane branch mirror is formed. By changing the irradiation amount of the electron beam stepwise with time, a step-like out-of-plane branch mirror, that is, a diffraction grating-like out-of-plane branch mirror can be formed.

According to an embodiment of the method of manufacturing an optical integrated circuit having an out-of-plane branching mirror according to the present invention, in the electron beam beam scanning step, the change in energy per unit time of the irradiated electron beam is changed in two stages, It is characterized in that two surfaces having different angles from each other with respect to the normal line of the substrate surface are formed. Thus, by forming two mirror surfaces having different angles with respect to the normal line of the substrate, the signal light processed by the optical integrated circuit can be split into two beams and emitted.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, experimental results forming the basic idea of the present invention will be described. A polymer optical material film such as polymethyl methacrylate (PMMA) or polyacrylate (trade name “U-100”) is formed on a glass substrate by 0.5.
The polymer film was coated with a thickness of about 2.5 μm, and the polymer film was irradiated with an electron beam, and then subjected to a development treatment, and the development depth of the polymer film was measured. The conditions of electron beam irradiation are as follows. Electron beam irradiation amount: 10 to 30 μC / cm ² (PMMA) Beam current: 0.5 nA Beam diameter: 0.1 μm Accelerating voltage: 25 kV: Under these conditions, the PMMA film was scanned with electron beams of various energies. FIG. 1 shows the relationship between the development depth and the electron beam dose. In FIG. 1, the horizontal axis indicates the dose of the electron beam, and the vertical axis indicates the development depth (relative value). As is clear from the experimental results shown in FIG. 1, the thickness of the polymer film removed by the development processing substantially linearly corresponds to the irradiation electron dose. Therefore, by performing electron beam scanning while changing the amount of electron beam to be irradiated with time, an out-of-plane branch mirror having a desired angle with respect to the normal line of the substrate can be formed.

FIGS. 2A and 2B are micrographs taken by a microscope at a magnification of 2500 times as a diagram when a mirror surface is formed by actually irradiating the PMMA film while changing the amount of electron beam irradiation with time. Things. Figure 2A shows 45 ° and 9
It is a figure of a microscope photograph at the time of forming a 0 ° mirror surface.
As is clear from FIG. 2A, it was confirmed that approximately 45 ° and 90 ° mirror surfaces could be formed. Also, FIG.
It is a figure at the time of forming the mirror surface which opposes 5 degrees and 45 degrees. In this case as well, a 45 ° mirror surface could be formed.

FIG. 3 shows an example of the configuration of an optical integrated circuit manufactured by the method according to the present invention. FIG. 3A is a schematic plan view, and FIG. 3B is a sectional view taken along line II of FIG. 3A. In this example, an optical integrated circuit having an optical waveguide and an optical modulator will be described. A polymer optical waveguide 2 and an optical modulator 3 are formed on a substrate 1. The optical waveguide 2 has out-of-plane branch mirrors 2a and 2b at both ends thereof.
The signal light to be modulated is made incident via b, and the modulated optical signal is emitted. The optical modulator 3 has a waveguide section 3a and electrodes 4a and 4b formed on both sides of the waveguide section 3a. The optical signal propagating through the optical waveguide section 3a is supplied to these electrodes by a signal supplied from a signal source (not shown). Modulate.

FIGS. 4A to 4C are schematic sectional views showing sequential manufacturing steps when manufacturing the optical integrated circuit shown in FIG.
As shown in FIG. 4A, first, a substrate 10 is prepared, and a polymer optical material film 11 is formed on the substrate 10. As the substrate, for example, a glass substrate or a sapphire substrate can be used, and as the polymer optical material, for example, a polymer optical material such as polymethyl methacrylate or polycarbonate can be used.

Next, the substrate is placed in a chamber of an electron beam irradiation apparatus, and electron beam irradiation is performed. When irradiating with electron beam,
In the present invention, an optical circuit element such as an optical waveguide or an optical modulator is formed by two-dimensionally scanning the substrate 10 using an electron beam.
In electron beam scanning, areas where optical circuit elements are not formed are irradiated with a constant amount of irradiation at an amount of energy at which the polymer film is completely removed by a subsequent development process. However, the area forming the optical waveguide is not irradiated with an electron beam, and the area forming the out-of-plane branching mirror is irradiated with light so that the mirror surface is formed at a desired angle with respect to the normal of the substrate. Perform while changing. The scanning by the electron beam can be performed by computer control. The irradiation amount can be changed by changing the scanning speed over time or by changing the irradiation energy amount over time while keeping the scanning speed constant.

FIG. 4B shows a mode in which the electron beam is irradiated along the areas a to e shown in FIG. 3B. For the area a where no optical element is formed, scanning is performed while irradiating with the highest irradiation amount at a temporally constant irradiation amount. Next, scanning is performed on the area b constituting the out-of-plane branching mirror 2b so that the irradiation amount of the electron beam gradually decreases with time. Next, the area c corresponding to the optical waveguide 2 is not irradiated with the electron beam.
Next, scanning is performed on the section d constituting the out-of-plane branching mirror 2a while increasing the irradiation amount of the electron beam with time. Further, the scanning is performed while irradiating the area e where the optical element is not formed with the temporally constant irradiation amount at the highest irradiation amount.

After the completion of the electron beam irradiation, a developing process is performed to remove the polymer optical material from the area irradiated with the electron beam according to the amount of the electron beam irradiation. As the development processing, for example, thermal development or wet development in which the substrate to which the electron beam irradiation has been completed is heated to near the glass transition point of the polymer optical material and then rinsed is performed. As described above, in the present invention, the polymer optical material can be removed in accordance with the energy amount of the irradiated electron beam, so that an optical circuit having the form shown in FIG. 4C can be formed after the development processing.

FIGS. 5A and 5B are diagrammatic sectional views showing a modification of the out-of-plane split mirror formed according to the present invention. FIG. 5A
In the example shown in FIG. 1, an out-of-plane branching mirror obtained when the dose of the electron beam to be irradiated is changed stepwise over time is shown. In this case, the out-of-plane branch mirror is formed like a diffraction grating. In the example shown in FIG. 5B, the mirror surface is composed of two surfaces having different angles with respect to the normal line of the substrate. Also in this case, it can be easily formed by changing the temporal change of the electron beam irradiation amount in two stages. By forming such a mirror surface, the signal light can be emitted as two light beams.

[Brief description of the drawings]

FIG. 1 is a graph showing an experimental result of a relationship between a dose amount of an irradiated electron beam and a developing depth.

FIG. 2 is a diagrammatic sectional view showing a micrograph showing the structure of an out-of-plane branch mirror actually manufactured according to the present invention.

FIG. 3 is a plan view and a schematic cross-sectional view showing a configuration of an example of an optical integrated circuit formed according to the present invention.

FIG. 4 is a schematic sectional view showing a sequential manufacturing process of the optical integrated circuit shown in FIG. 3;

FIG. 5 is a schematic sectional view showing a modification of the out-of-plane split mirror formed according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Optical waveguide 2a, 2b Out-of-plane branching mirror 3 Optical modulator 11 Substrate 12 Polymer optical material film

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideki Nakayama 5-22 Bunkacho, Hamamatsu City, Shizuoka Prefecture (72) Inventor Naoki Tomaru 558-3 Furuichicho, Maebashi City, Gunma Prefecture

Claims (3)

[Claims] In forming an optical integrated circuit having an out-of-plane branching mirror on a substrate, a step of forming a polymer optical material film constituting an optical circuit element on the substrate; A step of directly two-dimensionally scanning with an electron beam; and a step of removing a polymer optical material film in an area where an optical circuit element is not formed by a developing process. It is characterized in that a region where no element is formed is scanned with a constant energy irradiation amount over time, and an area where an out-of-plane branch mirror is to be formed is scanned while changing the irradiation energy amount over time. A method for manufacturing an optical integrated circuit. 2. The optical integration according to claim 1, wherein in the electron beam scanning step, the irradiation amount of the electron beam is changed stepwise to form a step-like out-of-plane branching mirror. Circuit manufacturing method. 3. In the scanning step of the electron beam,
2. The method according to claim 1, wherein the energy of the irradiated electron beam per unit time is changed in two stages to form two branch mirror surfaces having different angles with respect to the normal to the substrate surface. Manufacturing method of an optical integrated circuit.