JPH0815542A - Bleach mask - Google Patents

Abstract

(57) Abstract [Objective] To provide a simplified method by which a pattern of laterally defined waveguide channels can be created in a polymer optical waveguide. A refractive index of an uncovered portion of the waveguiding material is provided by providing the waveguiding material with a mask that selectively covers the portion of the waveguiding material, and irradiating the waveguiding material through the mask. In a method of making a polymer optical waveguide component that employs a waveguiding material that undergoes a change in refractive index when exposed to radiation of an appropriate wavelength, including the step of varying A developed photoresist that is not optically transparent.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to optical waveguides.
Such a waveguide is typically a light confinement of the waveguiding material surrounded by a material that has a lower refractive index than the waveguiding material.
It is designed to allow light to propagate in (confinement).

The present invention provides an uncovered waveguiding material by providing the waveguiding material with a mask that selectively covers portions of the waveguiding material, and then irradiating the waveguiding material through the mask. A polymer optical waveguide component that employs a waveguiding material (ie, a bleachable polymer) that undergoes a change in refractive index when exposed to an appropriate wavelength, including the step of changing the refractive index of a portion of the material. It is aimed at how to make it.

More particularly, the present invention relates to a laminated polymer optical waveguide structure that includes a light guiding layer of bleachable polymer sandwiched between two polarizing layers of lower refractive index than the light guiding layer. The present invention relates to a laminated waveguide component including. Thus, the wave confinement in the vertical direction (ie, perpendicular to the layers) is determined by the layered structure. The waveguide channel is laterally defined by selectively changing the refractive index of the bleachable polymer in the light guiding layer.

[0004]

The above method is described in US Pat. No. 5,142,6.
No. 05 (and corresponding European Patent No. 358,476)
Publication), which is incorporated herein by reference for all purposes. The change in index of refraction is usually the amount of reduction such that the waveguide channel can be created by illuminating the material surrounding the desired wave confinement. It is stated that selective exposure of the polymeric material to radiation can occur through a mask having portions that are transparent and portions that are non-transparent to the applied radiation.

In practice, the only known workable mask is a metal mask. Metals, typically gold or aluminum, very effectively prevent bleaching radiation from reaching the parts of the waveguiding polymer that must not be bleached,
On the other hand, the use of metal masks has various drawbacks.

One such drawback is that the process is lengthy and complex. It is usually
Including the following steps: That is, (a) making a laminated waveguide,
(B) applying a metal film on the waveguide, (c)
Providing the metal film with a photoresist layer, (d)
Selectively exposing the photoresist through a mask that defines the desired pattern of lateral wave confinement, (e)
Developing the photoresist to selectively expose the metal, (f) etching away the exposed metal to create an opening, (g) stripping the photoresist, (h) waveguide Irradiating the waveguide through the opening using irradiation where the refractive index of the ionic polymer is changed, and (i) etching away the metal.

If an electro-optically active waveguide is made, the metal mask can be used as an electrode, so that it is possible to stop removing the metal mask. But,
In that case, the electrodes would have the same shape as the bleach mask. This is a severe design limitation. For passive waveguide components and thermo-optic waveguide components, the metal layer is always extra and must be removed.

Such a method involving the application and removal of expensive precious metals is cumbersome and uneconomical. Moreover, it requires the use of expensive equipment. Also, undesired metal residues usually remain after removal of the metal mask.

Several additional drawbacks apply. Etching metal with a photoresist mask will usually result in "underetching". That is, the resulting strip of metal, and thus the resulting wave confinement, will have a narrower width than the strip of resist above it. Moreover, metal etching may result in walls with undesired roughness. Therefore, it is desirable to provide a method by which wave confinement can be more accurately defined. Furthermore, the etchants used for metals may be detrimental to the waveguide polymer, so it would be advantageous if their use could be avoided.

[0010]

It is an object of the present invention to provide a bleaching method which does not suffer from these drawbacks.

[0011]

SUMMARY OF THE INVENTION For the above purposes, the present invention is directed to a method as described in the "Industrial Application" section in which the mask is not substantially transparent to the irradiation wavelength. It is to be a photoresist which was made.

The resulting method comprises the following steps: That is,
(A) making a laminated waveguide, (b) applying a photoresist layer on the waveguide, (c) exposing the photoresist through a mask that defines the desired pattern of lateral wave confinement. Using (d) developing the photoresist to create openings, ie, selectively exposing the waveguide, and (e) irradiating to change the refractive index of the guiding layer polymer. Irradiating the waveguide through the opening, and (f) stripping the photoresist.

The present invention also provides a pattern of one or more waveguide channels in a flat optical waveguide by illuminating the waveguide with illumination within a wavelength or range of wavelengths. A method of using a photoresist that is substantially opaque to light within a wavelength or range of wavelengths to define.

This surprisingly simple method is enabled by the use of photoresists which have a low transmission for the irradiation wavelength. A transmission of about 50% is sufficient to achieve a refractive index contrast between the bleached and unbleached polymers of about 0.003, based on which the preferred waveguide channel is obtained. Is. It can generally be stated that, as an indicator for determining the suitability of a photoresist, it must have an opacity of at least 50% (ie a transmission of at most 50%). However, depending on the wavelength as well as the bleaching sensitivity of the guiding layer polymer, a substantially higher transmission (eg 75%) will still give an acceptable refractive index contrast, or the photoresist will show It will be appreciated that the transmission must be much lower (e.g. 25%) to be substantially non-permeable. Generally, suitable photoresists are those that will absorb energy at the bleaching wavelength. Preferably, it is accomplished by employing a photoresist that contains dye molecules that have absorption bands in the proper wavelength. Photoresists including metal or semiconductor particles such as silicon-containing resists may also be used.

The wavelength to be used depends on the polymer utilized in the guiding layer. Suitable polymers are mentioned above all in EP 358,476. The present invention is not limited to any particular type of polymer as long as the polymer undergoes a change in refractive index when exposed to a wavelength or a range of wavelengths.

Bleaching radiation is usually ultraviolet light or visible light, where blue light is preferred in most cases. In general, a suitable photoresist is a "dye-resist (dye
d resists) ". They are all 4
AZ 6618-2DG, AZ 6 absorbing at 36 nm
218B-3DG, and AZ75 absorbing at 365 nm
Includes those sold by Hoechst Limited under the trademark 10-2DG. Other dye-containing resists are trademarks of microposit (S1813-J2, S181).
8-J2, S1400-27 D1, S1400-31
D1) marketed by Shipley. If bleaching irradiation is 200-300 nm
Many conventional photoresists can be employed as bleaching masks, provided they have wavelengths in the range. Templates that are partially transparent and partially non-transparent to UV radiation are described in DE 114717 for use in the manufacture of printed wiring boards. .

The photoresist needs to be developable by a developer that does not damage the polymer to which it is applied (usually the top deflection layer). The above photoresists can be developed using metal ion free or metal ion based developers. Suitable developers are usually recommended by photoresist manufacturers.

Basically, the method of the present invention can be used to make all types of polymer optical waveguide components.
For example, electro-optical components (where the bleachable polymer can be made electro-optically active (ie, NLO polymer)),
These are thermo-optical components and passive components. Such parts are generally known to the person skilled in the art and do not require further explanation here for the purposes of the present invention.

The method of the present invention is further illustrated in the accompanying drawings, which should not be construed as limiting the invention in any way.

FIG. 1 illustrates the method of the present invention, and FIG. 2 illustrates the conventional prior art method. In both figures, successive process steps are indicated also with the letters used above. That is, the method of the present invention comprises steps (1a) to (1f), while the prior art method comprises steps (2a) to (2i).
including. In both figures, the structures represented for each stage are cross-sectional views of the layers perpendicular to the light guiding direction.

First, FIG. 1 relating to the present invention will be described.

In FIG. 1a, the substrate (1), the lower deflection layer (2), the wave guiding layer (3) and the top deflection layer (4).
A laminated waveguide including is shown. It is also possible to omit the top deflection layer at this stage and apply it after the wave confinement has been formed. In FIG. 1b the same structure is shown in which a photoresist layer (11) has been applied on the top deflection layer (4).

In FIG. 1c it is shown how the photoresist layer (11) is exposed through the mask (7), where hν-E is used to activate the photoresist layer. Exposure exposure (usually about 3-5 seconds).

In FIG. 1d it is shown how exposure and development of the photoresist layer (11) through the mask results in openings (12).

Illustrated in FIG. 1e is the irradiation of the waveguide through the opening (12) in the photoresist layer (11), where hν-B is the desired refractive index in the guiding layer polymer. The bleaching irradiation (typically about 4-12 hours) employed to cause the change is shown.

In FIG. 1f, the photoresist has been stripped and the guiding layer (3) has been properly bleached to include wave confinement (9) surrounded by bleached material (10). Is shown.

Next, FIG. 2 relating to a conventional prior art will be described for comparison.

In FIG. 2a, the substrate (1), the lower deflection layer (2), the wave guiding layer (3) and the top deflection layer (4).
A laminated waveguide including is shown. Again, it is also possible at this stage to omit the top deflection layer and apply it after the wave confinement has been formed.

In FIG. 2b the same structure is shown in which a metal layer (5) is applied on the top deflection layer (4).

In FIG. 2c it is shown that a photoresist layer (6) has been applied on the metal layer.

In FIG. 2d it is shown how the photoresist layer (6) is exposed through the mask (7), where hν-E is to activate the photoresist layer (6). The exposure irradiation (usually about 3 to 5 seconds) employed in (3) is shown.

In FIG. 2e it is shown how the exposure and development of the photoresist layer (6) through the mask results in the metal being selectively exposed.

In FIG. 2f it is shown that the exposed metal parts are etched away, creating openings (8) in the metal layer (5).

In FIG. 2g it is shown that the photoresist has been stripped. The waveguide remains covered by a mask containing metal (5) and openings (8).

Illumination of the waveguide through the opening is depicted in FIG. 2h, where hν-B is the bleaching radiation employed to cause the desired refractive index change in the guiding layer polymer. (Usually about 4-12 hours).

In FIG. 2i, the metal has been etched away,
The guiding layer (3) is then bleached (1
It was shown to be properly bleached to include wave confinement (9) surrounded by 0).

[0037]

The present invention provides a simplified method by which a laterally defined waveguide channel pattern can be created in a polymer optical waveguide.

[Brief description of drawings]

FIG. 1 shows a method for manufacturing a polymer optical waveguide component of the present invention.

FIG. 2 illustrates a method of making a conventional prior art polymer optical waveguide component.

[Explanation of symbols]

 1. Substrate 2. Lower deflection layer 3. Wave guiding layer 4. Top deflection layer 5. Metal layer 6. Photoresist layer 7. Mask 8. Opening 9. Wave confinement 10. Bleached substances 11. Photoresist layer 12. Aperture

Claims (5)

[Claims] 1. A mask for selectively covering a portion of the waveguiding material is provided on the waveguiding material, and by irradiating the waveguiding material through the mask, the portion of the waveguiding material not covered is covered. In a method of making a polymer optical waveguide component that employs a waveguiding material that undergoes a change in refractive index when exposed to an appropriate wavelength of irradiation, including the step of changing the refractive index, a mask And a developed photoresist that is not substantially transparent. 2. A method of making a pattern of laterally defined waveguide channels in a polymer optical waveguide, comprising:
The next step is to provide a waveguide having a laminated structure including (a) a polymer guiding layer (3) sandwiched between two deflection layers (2, 4) having a lower refractive index than the guiding layer. , (B) a photoresist layer (11) on the laminated waveguide
(C) exposing the photoresist through a mask (7) that defines the desired pattern,
(D) developing photoresist to create openings (12) defining the pattern of the covered and exposed portions of the laminated waveguide; (e) changing the refractive index of the guiding layer polymer. Irradiating the patterned waveguide with a wavelength of, provided that the developed photoresist is not substantially transparent to the wavelength of irradiation. 3. Process according to claim 1 or 2, characterized in that the developed photoresist substantially absorbs the wavelength used. 4. The method of claim 3, wherein the photoresist contains dye molecules that absorb energy of a suitable wavelength. 5. To define a pattern of one or more waveguide channels in a flat optical waveguide by illuminating the waveguide with illumination at a wavelength or within a range of wavelengths. , Using a photoresist that is substantially non-transparent to light at a wavelength or within a range of wavelengths.