JP3340022B2 - Optical multilayer filter and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical multilayer filter for multiplexing or demultiplexing light of a specific wavelength in optical communication and a method of manufacturing the same.

[0002]

2. Description of the Related Art Generally, when manufacturing an optical multilayer filter of this type, a high refractive index layer made of TiO ₂ or the like and a low refractive index layer made of SiO ₂ or the like are formed on a substrate so as to have a desired wavelength selectivity. Are stacked in multiple layers, and this is cut for each chip. Here, when the multilayer film is formed on the substrate, the difference in the coefficient of thermal expansion between the substrate and each layer of the multilayer film,
Warpage occurs due to the internal stress of each layer of the multilayer film. In this case, as shown in FIG. 3, the direction of the warp of the high refractive index layer (TiO ₂₎ and the low-refractive index layer (SiO ₂₎ is reversed or, warpage TiO ₂ is greater than SiO _2.

Conventionally, as a method for preventing such a warp, as disclosed in Japanese Patent Publication No. Hei 6-90328, a substrate is formed in a curved shape in advance in anticipation of a warp, and the curved surface of the substrate is heated. A method has been proposed in which a multilayer film is formed in a state and then returned to normal temperature, and the multilayer film is flattened in a normal temperature state. Another method is disclosed in Japanese Patent Application Laid-Open No. 5-127.
As disclosed in Japanese Patent Publication No. 018, a method of symmetrically forming a multilayer film having substantially the same thickness on both front and back surfaces of a substrate has been proposed.

[0004]

However, of the above-mentioned prior art examples, the former (Japanese Patent Publication No. 6-90328).
According to the method, since the amount of curvature of the substrate is predicted from the difference in thermal expansion coefficient between the substrate and the multilayer film, and the substrate is bent in advance, the optical characteristics deteriorate due to warpage caused by the internal stress of each layer of the multilayer film. In addition, the substrate needs to be processed into a complicated shape such as an aspherical surface, which leads to an increase in cost. In addition, the latter (Japanese Unexamined Patent Application Publication No.
In the method of JP-A-127018, a multi-layer film must be formed on the front surface and the back surface of the substrate, so that there is a problem that the number of steps of forming the multi-layer film is doubled and the cost is increased.

[0005]

According to the present invention, an anti-warp layer is formed on the uppermost layer of the multilayer film except for the effective area of the filter. As described above, by forming the anti-warp layer in the uppermost layer of the multilayer film except for the effective region of the filter, the warpage during the formation of the multilayer film is canceled, and the optical characteristics of the optical multilayer filter are improved. .

With the above structure, the warpage of the multilayer film can be prevented only by adding a step of forming the warpage prevention layer on the multilayer film. Further, since the warp prevention layer is not formed in the effective area of the filter, it is possible to prevent the wavelength selectivity of the filter from being impaired.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In an optical multilayer filter according to the present invention, a warp preventing layer for canceling and flattening a warp in forming a multilayer film is provided, and an effective area of the filter in the uppermost layer of the multilayer film is defined. It was formed at the removed site. According to the optical multilayer filter configured as described above, it is possible to prevent the warpage of the multilayer film by simply adding the step of forming the anti-warp layer on the uppermost layer of the multilayer film, thereby suppressing an increase in cost. In addition, since the warp prevention layer is not formed in the effective area of the filter, it is possible to prevent the optical characteristics of the filter from being impaired.

The multilayer film is formed on a substrate. If the multilayer film and the warpage preventing layer are formed on the substrate and then cut into multilayer filter chips, an optical multilayer filter with a substrate can be obtained. . Further, using a dissolvable substrate, forming a multilayer film and an anti-warpage layer on the substrate, cutting the multilayer filter chip, and dissolving the substrate, a so-called substrate-less optical multilayer filter can be obtained. .

Further, in the method for manufacturing an optical multilayer filter according to the present invention, a film forming step of forming a multilayer film on a substrate, and the film forming step is performed on a top layer of the multilayer film except for an effective area of the filter. Forming a warp preventing layer for canceling the warpage of the substrate and the multilayer film by the step and flattening the substrate, and cutting the substrate for each multilayer filter chip. Then, an optical multilayer filter with a substrate is manufactured.

In the method for manufacturing an optical multilayer filter according to the present invention, a film forming step of forming a multilayer film on a dissolvable substrate is performed by: A step of forming a warp preventing layer for canceling and flattening the substrate and the multilayer film by the film forming step, a step of cutting the substrate for each multilayer filter chip, and dissolving the substrate And a substrate-less optical multilayer filter is manufactured by such a method.

The thickness of the warp preventing layer may be determined by simulating a warp in the case where a multilayer film is formed on a substrate in advance, but after forming the multilayer film on the substrate and then measuring the warp. By determining the thickness of the warpage prevention layer, it is possible to reliably prevent warpage during the formation of the multilayer film.

[0012]

Embodiments will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of an optical multilayer filter according to one embodiment of the present invention, and FIG. 2 is an explanatory view showing a manufacturing process of the optical multilayer filter of FIG.

In FIG. 1, a high refractive index layer 2 is provided on a substrate 1.
a and the low-refractive-index layers 2b are alternately laminated in layers to form a multilayer film 2. The material of the high refractive index layer 2a is, for example, TiO ₂ , and the material of the low refractive index layer 2b is, for example, S.
iO ₂ is used, and these can be formed by sputtering, vapor deposition, or ion plating. Note that the combination, thickness, and the like of each layer of the high refractive index layer 2a and the low refractive index layer 2b differ depending on the desired wavelength selectivity. An anti-warp layer 3 is formed on the uppermost layer of the multilayer film 2, and the anti-warp layer 3 is formed in an effective area 3a of the filter.
And the effective area 3a becomes a filter window. The warp prevention layer 3 is for canceling the warp during the formation of the substrate 1 and the multilayer film 2 and flattening, and is a light-transmitting material such as TiO ₂ or SiO _{2 of the} same kind as the multilayer film 2, or
MgF ₂ is not formed in the effective area 3a of the filter.
And the like, and these can also be formed by sputtering, vapor deposition, or ion plating.

Next, a manufacturing process of the optical multilayer filter having the above-described structure will be described with reference to FIG. FIG.
As the substrate 1 shown in (a), glass (when the substrate 1 is not removed later), NaCl or KBr (when the substrate 1 is removed later) or the like is used. Next, the substrate 1 is mounted on a susceptor for film formation, and a high refractive index layer 2a of TiO ₂ and a low refractive index layer 2b of SiO ₂ are alternately formed in a multilayer in a vacuum evaporation chamber according to a desired wavelength selectivity. Fig. 2 (b)
1, a multilayer film 2 is formed on a substrate 1. Next, as shown in FIG. 2C, the warp prevention layer 3 is formed on the uppermost layer of the multilayer film 2 except for the effective region 3a of the filter.

Here, as a method of determining the thickness of the warpage preventing layer 3, the materials and thicknesses of the respective layers of the substrate 1 and the multilayer film 2 to be used, and the direction and amount of warping with respect to the material of the warpage preventing layer 3 are shown in FIG. As shown in the figure, the warpage when the multilayer film 2 is formed on the substrate 1 and the coefficient of thermal expansion of the warpage prevention layer 3 are simulated in advance to determine the thickness of the warpage prevention layer 3. After forming the final layer, the warpage preventing layer 3 is formed based on the simulation result. As another method, after forming the multilayer film 2 on the substrate 1, the actual warpage is measured by a flatness tester or the like, and the thickness of the warpage preventing layer 3 for returning the warp to the original flat state is determined. Form a film.

After forming the warpage preventing layer 3 as described above, as shown in FIG. 2D, cutting is performed for each chip using a laser cutter, a dicing cutter, or the like, to obtain a substrate as shown in FIG. 2E. The filter element chip 10 with 1 is completed. When the substrate 1 is removed, as shown in FIG. 2F, NaCl and KBr constituting the substrate 1 are melted and removed, and only the multilayer film 2 is obtained as the filter element chip 10.

[0017]

The present invention is embodied in the form described above and has the following effects.

By forming an anti-warp layer for canceling the warpage during the formation of the multilayer film and flattening it at a position other than the effective area of the filter in the uppermost layer of the multilayer film, the warp prevention layer is simply formed. Is added to the uppermost layer of the multilayer film, the warpage of the multilayer film can be prevented, the cost can be suppressed, and the warpage prevention layer is not formed in the effective area of the filter. Therefore, it is possible to prevent the wavelength selectivity of the filter from being impaired.

A film forming step of forming a multilayer film on the substrate; and canceling a warp of the substrate and the multilayer film due to the film forming step in a portion of the uppermost layer of the multilayer film other than an effective area of the filter. Forming an anti-warp layer for flattening and cutting the substrate for each multilayer filter chip, thereby producing an optical multilayer filter with a substrate having excellent optical characteristics at low cost. can do.

A film forming step of forming a multilayer film on a dissolvable substrate; and a step of forming the multilayer film on the uppermost layer of the multilayer film except for an effective area of the filter. Excellent in optical characteristics by having a step of forming a warp preventing layer for flattening by canceling the warp, a step of cutting the substrate for each multilayer filter chip, and a step of dissolving the substrate. A substrate-less optical multilayer filter can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an optical multilayer filter according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a manufacturing process of the optical multilayer filter of FIG. 1;

FIG. 3 shows a high refractive index layer (TiO ₂ ) and a low refractive index layer (Si
O ₂₎ is an explanatory diagram showing the direction and amount of warpage of warpage of.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Multilayer film 2a High refractive index layer 2b Low refractive index layer 3 Warp prevention layer 3a Effective area of filter

Claims (4)

(57) [Claims] An anti-warp layer for canceling warpage during the formation of a multilayer film and flattening the film is formed in a portion of the uppermost layer of the multilayer film excluding an effective area of a filter. Optical multilayer filter. 2. The optical multilayer filter according to claim 1, wherein the multilayer film is formed on a substrate. 3. A film forming step of forming a multilayer film on a substrate;
Forming a warp preventing layer for canceling the warp of the substrate and the multilayer film by the film forming step and flattening the portion in a portion of the uppermost layer of the multilayer film other than the effective region of the filter; and Cutting the optical fiber for each multilayer filter chip. 4. A film forming step of forming a multilayer film on a dissolvable substrate, and a step of forming the multilayer film on the uppermost layer of the multilayer film excluding an effective area of a filter. A method for manufacturing an optical multilayer filter, comprising: a step of forming a warp preventing layer for canceling warp and flattening; a step of cutting the substrate for each multilayer filter chip; and a step of dissolving the substrate.