JP3843762B2 - Waveguide type optical component with thin film heater and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a waveguide type optical component with a thin film heater and a method for manufacturing the same.
[0002]
[Prior art]
In recent years, functional parts such as an optical attenuator, an optical branching unit, and an optical switch have been developed using an optical interferometer configured by a silica-based glass optical waveguide. Usually, a thin film heater for utilizing a thermo-optic effect is used for a phase shifter used in a glass waveguide type optical interferometer.
[0003]
FIG. 3A is a plan view of an optical attenuator to which a conventional method for manufacturing a waveguide-type optical component with a thin film heater is applied, and FIG. 3B is a cross-sectional view taken along line AA in FIG. is there.
[0004]
This optical attenuator is formed in parallel in the clad layer 5 and has two arm waveguides 3-1 and 3-2 having the same length, and the branch side is connected by both arm waveguides 3-1 and 3-2. Two Y branch waveguides 2-1 and 2-2, and a thin film heater 4 made of Ta ₂ N formed on one (upper side in the figure) arm waveguide 3-1.
[0005]
The signal light incident from the input waveguide 1-1 of this optical attenuator is equally distributed to the two arm waveguides 3-1 and 3-2 by one (left side in the figure) Y-branch waveguide 2-1. . The equally distributed signal light is coupled by the other (right side in the figure) Y-branch waveguide 2-2, and the optical power of the input signal light is maintained and emitted as it is through the output waveguide 1-2.
[0006]
On the other hand, when electric power is supplied to the thin film heater 4 and heated, the refractive index of the arm waveguide 3-1 changes, and the phase of the signal light propagating through the arm waveguide 3-1 changes. When the phase of the signal light changes, the intensity of the signal light coupled by the Y branch waveguide 2-2 changes. The light intensity of the signal light can be controlled by changing the power supplied to the thin film heater 4.
[0007]
[Problems to be solved by the invention]
By the way, a long-term reliability in practical use is required for the above-described conventional thin film heater used in the waveguide type optical component with a thin film heater.
[0008]
However, in actual long-term energization, there has been a problem that material deterioration due to oxidation of the surface of the thin film heater occurs, the resistance value of the thin film heater is deteriorated, or the thin film heater is disconnected.
[0009]
Accordingly, an object of the present invention is to solve the above-mentioned problems and provide a waveguide type optical component with a thin film heater having a long life of the thin film heater and a method for manufacturing the same.
[0010]
[Means for Solving the Problems]
The thin film heater with the waveguide type optical component of the present invention in order to attain the above objects, the silica based glass optical waveguide thin film heater with the waveguide type optical component to form a thin film heater made of metal on the element, the thin film heater, high silicon nitride film were sequentially formed on a silica glass waveguide element while holding a vacuum, and has a three-layer structure having a tantalum film and a silicon nitride film nitride.
[0011]
The method of manufacturing a waveguide type optical component with a thin film heater according to the present invention is a method for manufacturing a waveguide type optical component with a thin film heater, in which a thin film heater made of metal is formed on a silica-based glass optical waveguide element . A three-layer thin film heater is formed by sequentially forming a silicon nitride film, a tantalum nitride film, and a silicon nitride film on the quartz glass optical waveguide element as they are.
[0012]
In addition to the above configuration, the waveguide type optical component with a thin film heater of the present invention is preferably covered with a protective film made of SiO ₂ or silicon nitride.
[0013]
In addition to the above-described configuration, the method of manufacturing a waveguide-type optical component with a thin film heater according to the present invention uses a multi-target sputtering apparatus capable of changing a target in a high vacuum, and forms the thin film heater on a quartz glass optical waveguide element. A membrane is preferred.
[0014]
Here, when forming a Ta ₂ N film as a heater material on a glass waveguide, a multi-target sputtering apparatus capable of changing a sputtering target in a high vacuum is used, and a silicon nitride film, a tantalum nitride film, and a nitride film are used. Films were formed in the order of silicon films. After forming a heater pattern by reactive ion etching using the patterned resist by photolithography as a mask material by a plasma CVD method or RF sputtering method using a mixed gas of SiH ₄ and O _2, SiO ₂ A protective film was formed.
[0015]
When electric power is supplied to the Ta ₂ N heater, the temperature of the heater film rises. At this time, if the surface of the heater film is exposed to the atmosphere, the film surface is oxidized by oxygen in the atmosphere. By sequentially forming a silicon nitride film, a tantalum nitride film, and a silicon nitride film while maintaining a high vacuum state, oxygen is prevented from being adsorbed on the surface of the tantalum nitride film. Furthermore, by forming a SiO ₂ protective film on the surface of the heater film by plasma CVD or RF sputtering, it is possible to prevent the progress of oxidation during energization.
[0016]
In the case where a silicon nitride film, a tantalum nitride film, and a silicon nitride film are formed, oxygen and moisture in the atmosphere are adsorbed on the film surface by exposure to the atmosphere after each film is formed. As a result, oxygen and moisture are taken into the heater film, and oxidation of the film during energization cannot be prevented. In addition, a SiO ₂ protective film that covers the entire heater film is necessary to prevent oxidation from the side surface of the heater film.
[0017]
That is, according to the present invention, since the thin film heater has a three-layer structure of a silicon nitride film, a tantalum nitride film, and a silicon nitride film, oxygen and moisture are prevented from being taken into the tantalum nitride film, and the thin film heater A waveguide type optical component with a thin film heater having a long lifetime can be obtained.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0019]
FIG. 1A is a plan view of a waveguide type optical component with a thin film heater to which the method for manufacturing a waveguide type optical component with a thin film heater of the present invention is applied, and FIG. FIG. In addition, the same code | symbol was used for the member similar to the member shown to Fig.3 (a), (b).
[0020]
This waveguide type optical component with a thin film heater is a waveguide type optical component with a thin film heater in which a thin film heater 40 made of a metal is formed on the clad layer 5 of a silica-based glass optical waveguide element, for heating the waveguide 3. The thin film heater 40 has a three-layer structure of silicon nitride film 8-1 / tantalum nitride film 9 / silicon nitride film 8-2. The thin film heater 40 is covered with the protective film 7 together with the cladding layer 5. Reference numerals 6-1 and 6-2 denote electrode pads for connecting the thin film heater 40 and wiring (not shown).
[0021]
In this waveguide type optical component with a thin film heater, the thin film heater 40 has a three-layer structure of silicon nitride film 8-1 / tantalum nitride film 9 / silicon nitride film 8-2. Moisture is prevented from being taken in, and the life of the thin film heater 40 is prolonged.
[0022]
【Example】
Hereinafter, specific numerical values will be described. However, the present invention is not limited to this.
[0023]
Example 1
A thin film heater 40 having a three-layer structure is formed by sequentially forming a Si nitride film 8-1, a Ta ₂ N film 9 and a Si nitride film 8-2 on the cladding layer 5 of the silica glass optical waveguide device, and a protective film. The thin film heater 40 was covered with a SiO ₂ film 7 having a thickness of about 2 μm. The Si nitride film 8-1, the Ta ₂ N film 9, and the Si nitride film 8-2 are formed by a multi-target reactive sputtering apparatus (not shown) capable of changing the target in a high vacuum, and photolithography is performed. Reactive ion etching processing was performed using a resist patterned using the technique as a mask material. After the formation of the thin film heater 40, the protective film 7 made of SiO ₂ was formed using a plasma CVD method using a mixed gas of SiH ₄ and O ₂ . The temperature during the film formation was 300 ° C. Thereafter, the manufactured optical waveguide device was heat-treated in He gas at 700 ° C. for 30 minutes.
[0024]
FIG. 2 is a characteristic diagram showing the result of conducting an energization test for 500 hours by supplying 1 W of power to various samples. The horizontal axis indicates the energization time axis, and the vertical axis indicates the resistance change rate axis. In the figure, a characteristic curve L1 is a sample in which a thin film heater is constituted by only a Ta ₂ N film, and a characteristic curve L2 is exposed to the atmosphere when a Si nitride film, a Ta ₂ N film, and a Si nitride film are formed. In this case, the characteristic curve L3 relates to a sample in which a Si nitride film / Ta ₂ N film / Si nitride film was formed while maintaining a high vacuum, and a 500-hour energization test was performed by supplying 1 W of power. It is a characteristic curve which shows a result.
[0025]
The resistance change rate after elapse of 500 hours was about 7% for the sample in which the Si nitride film / Ta ₂ N film / Si nitride film was formed while maintaining a high vacuum.
[0026]
As is clear from FIG. 2, the thin-film heater having a three-layer structure obtained by forming a Si nitride film / Ta ₂ N film / Si nitride film while maintaining a high vacuum can suppress the rate of change in resistance. I understand.
[0027]
(Example 2)
For a sample manufactured by the same method as described in Example 1 except that the protective film of the thin film heater having a three-layer structure composed of a Si nitride film / Ta ₂ N film / Si nitride film is Si ₃ N ₄ , An energization test similar to that in Example 1 was performed. The change in resistivity after about 500 hours was about 7%.
[0028]
(Comparative Example 1)
A thin film heater having a two-layer structure of a nitrided Si film / Ta ₂ N film is formed by a multi-target reactive sputtering apparatus capable of changing the target in a high vacuum, patterned by the method described in Example 1, and then SiO ₂ A protective film was formed. As a result of supplying 1 W of power in the energization test, a 10% increase in resistance occurred in 500 hours. This is because oxygen and moisture adsorbed when the surface of the Ta ₂ N film is exposed to the atmosphere deteriorate the heater surface.
[0029]
(Comparative Example 2)
A thin film heater having a two-layer structure of a Si nitride film / Ta ₂ N film is formed by a multi-target reactive sputtering apparatus in which the target can be changed in a high vacuum, and patterned by the same method as described in the first embodiment. After that, a protective film made of SiO ₂ was formed. As a result of supplying 1 W of power in the energization test, a 10% increase in resistance occurred in 500 hours. This is because oxygen and moisture in the atmosphere adsorbed on the substrate side before the heater film formation deteriorates the heater surface.
[0030]
As described above, according to the present embodiment, material deterioration of the thin film heater used for the optical waveguide element can be reduced, resistance fluctuation, disconnection, and the like can be suppressed, and the life of the thin film heater can be extended.
[0031]
【The invention's effect】
In short, according to the present invention, the following excellent effects are exhibited.
[0032]
It is possible to provide a waveguide type optical component with a thin film heater having a long life of the thin film heater and a manufacturing method thereof.
[Brief description of the drawings]
FIG. 1A is a plan view of a waveguide type optical component with a thin film heater to which the method for manufacturing a waveguide type optical component with a thin film heater according to the present invention is applied, and FIG. It is line sectional drawing.
FIG. 2 is a characteristic diagram showing the results of conducting an energization test for 500 hours by supplying 1 W of power to various samples.
3A is a plan view of an optical attenuator to which a conventional method for manufacturing a waveguide type optical component with a thin film heater is applied, and FIG. 3B is a cross-sectional view taken along line AA in FIG.
[Explanation of symbols]
1 Silica-based glass optical waveguide element 3 Waveguide 7 Protective film (SiO ₂ film)
8-1, 8-2 Silicon nitride film (Si nitride film)
9 Tantalum nitride film (Ta ₂ N film)
40 Thin film heater

Claims (4)

In a waveguide type optical component with a thin film heater in which a thin film heater made of metal is formed on a silica glass optical waveguide element, the thin film heater is sequentially formed on the silica glass optical waveguide element while being held in a high vacuum . A waveguide-type optical component with a thin film heater, characterized by having a three-layer structure including a silicon nitride film, a tantalum nitride film, and a silicon nitride film. The waveguide type optical component with a thin film heater according to claim 1, wherein the entire thin film heater is covered with a protective film made of SiO ₂ or silicon nitride. The method of manufacturing a thin-film heater with a waveguide-type optical components for forming a thin film heater made of metal on a silica-based glass optical waveguide element, while holding a high vacuum before Symbol silica based glass optical waveguide element on the silicon nitride film, nitride A method of manufacturing a waveguide type optical component with a thin film heater, comprising forming a thin film heater having a three-layer structure by sequentially forming a tantalum film and a silicon nitride film. Change Target in high vacuum using a multi-target sputter apparatus capable, on SL thin film heater of the thin film heater with the waveguide type optical component according to claim 3 formed on said silica glass optical waveguide device Production method.

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