JPS62279303A - Production of optical waveguide layer - Google Patents

Abstract

PURPOSE:To enable the control of a film thickness with good uniformity and the reduction of substrate warpage by subjecting an Si-contg. gas and O-contg. gas to a plasma cracking, thereby forming an SiO2 film on a substrate. CONSTITUTION:A substrate holder 3 having heating means such as, for example, a heater 7, is provided in a vacuum vessel (sample chamber) 1. The substrate (sample) 2 is imposed on the holder 3 and is heated to <=500 deg.C. The pressure in the vacuum vessel is regulated by an evacuation system. The Si-contg. gas and the other gaseous raw materials as well as the gaseous O2 are introduced respectively through introducing pipes 8 and 9 into the vacuum vessel 1. The Si-contg. gas, the other gaseous raw materials and the gaseous O2 are cracked by the plasma wave introduced through a waveguide 5 from a microwave source 6 into the vacuum vessel and deposit SiO2 on the substrate surface by reaction on the surface of the substrate 2 in the vacuum vessel 1. The above-mentioned formation is combined with the formation of a pattern by a known method, by which the optical waveguide layer is obtd.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention is directed to optical couplers, optical multiplexing and demultiplexing, which are essential for the diversification and advancement of optical communication systems and optical information systems. The present invention relates to a method of manufacturing an optical waveguide that is advantageous for reducing the cost, size, and stability of optical components such as devices.

[Prior art] Conventional optical components consist of microscopic optical components such as prisms.
Optical axis alignment and assembly are difficult.

Therefore, various waveguides have been proposed in order to avoid these complicated operations by creating optical waveguides on a plane.

Examples of materials used for optical waveguides include semiconductor crystals, dielectric crystals, glass, and polymer materials. To create an optical waveguide using these materials, after forming a core layer and a cladding layer on a substrate (which can also be used as a cladding layer), a structure as shown in Figure 3 is created using an etching method, exposure method, etc. Then, do all the trapping of the light. In FIG. 3, 2 is a substrate (or cladding), 10 is a core layer, and 11 is a cladding layer.

By the way, thermal CVD methods and flame direct deposition methods have conventionally been used to form these core layers and cladding layers.

What is the thermal CVD method?5As shown in a schematic diagram in FIG.
CL< , Ti C14,02, etc. are introduced, glass fine particles are synthesized by an oxidation reaction, and the substrate 2 on the holder 14 is
In this method, the synthetic glass particles are deposited on top of the reactor, and the reaction temperature is about 1200° C. at the highest point, and by creating a temperature gradient in the furnace 15, the deposition of the glass particles is promoted due to the thermophoretic effect. Note that 16 indicates the exhaust system.

The flame direct deposition method is, as shown in FIG.
iCt, etc. are introduced into a glass fine particle synthesis torch 18 having a concentric nozzle, and glass fine particles are synthesized by a flame hydrolysis reaction in an oxyhydrogen frame 19 which has been formed in advance. This is a method in which gold is deposited directly on the substrate 2 where gold is moving.

In order to make the thickness of the deposited glass particle film uniform, the torch 18
is caused to reciprocate in the radial direction of the turntable 17.

[Problem that the invention seeks to solve]

However, in conventional techniques such as the thermal C"i'D method and the flame direct deposition method, the substrate temperature'(i
- Keeping the temperature at a high temperature of ~1200°C makes it difficult to maintain a uniform substrate temperature9, and the refractive index changes due to fluctuations in the gas flow rate during deposition and the condition of the exhaust system9, and non-uniformity in film thickness. This has disadvantages such as increased propagation loss and presence of warp metal on the substrate.

The present invention aims to solve the problems of the prior art and provide a new method that can easily manufacture a low-loss optical waveguide.

[Means to solve the problem]

Instead of the conventional method of holding the substrate at a high temperature, the present inventors used a gas containing S1 and O6 as fc raw materials, decomposed the S1-containing gas and O-containing gas with low-temperature plasma, and reacted on the substrate surface. By this method, it is possible to deposit an optical waveguide layer made of 8102 on the substrate by keeping the substrate at a low temperature of 500° C. or lower.
The inventors have discovered that it is possible to solve the above-mentioned drawbacks and obtain an optical waveguide layer with low loss, and have thus arrived at the present invention.

That is, the present invention provides a gas containing S1y@ and a gas containing 0? 8102 on the substrate by glazma decomposition
This is a method of manufacturing an optical waveguide layer, which is characterized in that it is formed by conversion.

In a particularly preferred embodiment of the invention, the plasma decomposition is microwave plasma decomposition and the substrate is heated to a temperature of 500°C.
The above-mentioned method is listed below.

In the present invention, in order to excite the gas and activate other components, a so-called plasma decomposition method is used in which radio frequency (RF) is applied to the gas to transform the gas into a plasma state and decompose it. For example, using SiH4 as the gas containing Si gold and ζ)zk as the gas containing Ω, the reaction mechanism of the present invention in this case is as follows.

RF * o2-1 → 20 * El i H4 → S1 + 4H a H-2H2 (pF air) 1556 MHz as high frequency modification for normal plasma decomposition
However, in Unkaimei, 2. is preferably used.
45 GHz MA/F [marked on the ion source via the gold source/special tube? j [1 (to be distinguished from the conventional one by Koshu He, herein it is referred to as microwave plasma decomposition). The electrons in the ion source are held at high speed by this microwave, but at this time, the microphone CI
When a magnetic field parallel to the direction of movement is applied, 9 electrons drift due to the interaction between the magnetic field and the electric field caused by micro-reactions. The strength of the field a is 875 Gaussian, the conditions for electron cyclotron resonance are adjusted, and the electrons are accelerated in the ion source. Therefore, the probability of ionization of neutral particles (gas) due to the electron surface sK in the ion source is becomes higher.

Examples of gases having Si Mira used in the present invention include SiH4, 812H4, 5iHC4, F31H
Examples of the gold-containing gas include 2C8iO24 and SiF4, and examples of the gold-containing gas include 1-I'02*N20. In the present invention, other raw material gases to be added to the glass include 1, for example, N2, NH3,
G 8 H4.

82H4, PH3, etc. may also be used. The flow rate of these gases is, for example, 5 to 20 for Sl-containing gas and 0-containing gas.
cc/min The raw material gas for doping is 10 of the above 0-containing gas.
This is done at about 20 times, but the conditions are not particularly limited. The degree of vacuum in the general chamber in the present invention is such that plasma can be generated (,1
(] Bow ~10-” Torr, usually 10-’ Torr
This is nothing special.

The temperature of the substrate in the present invention may be at room temperature or higher, preferably at room temperature to 500°C. Although this is possible even at 500°C or higher, this is because uniform heating is easy at about 50°C. The heating means is ordinary resistance heating using light, and uniform heating is possible, so the film thickness is not limited to t2. - or warping of the board does not occur.

The plasma conditions in the present invention include, for example, 2.45 GHz microwave to IKW, magnet current 0 to 30 A, and the like.

When the present invention is carried out under the above conditions, a good CvD rate (film deposition rate) of 200 to 1000 A/min can be obtained.

The explanation will be given below with reference to all the drawings. FIG. 1 is a schematic diagram illustrating an embodiment of the present invention. In FIG. 1, 1 is a vacuum chamber (sample chamber), inside of which is provided a substrate holder 5 having a heating means such as a heater 7, and a substrate (sample) 2 is placed on the substrate holder 3. and heated to a temperature of 500° C. or less. The pressure inside the vacuum chamber 1 is regulated by an exhaust system, and a Sl 2 -containing gas, other raw material gas, and 02 gas are introduced into the vacuum chamber 1 through seven inlet pipes 8 and 9, respectively. The S1-containing gas, other raw material gases, and O2 gas are decomposed by plasma waves introduced into the vacuum chamber 1 from the microphone wave source 6 through the waveguide 5, and react on the surface of the substrate 2. Then, KSiO2'i is deposited on the substrate surface.

As described above, the 8101 layer or Sin is formed on the substrate.

An optical waveguide layer can be obtained by forming a layer containing an additive and patterning it by a known method.

〔Example〕

An optical waveguide layer can be produced according to the present invention using the apparatus having the configuration shown in FIG. The interior of the sample chamber was maintained at 5 x 10-' Torr, a round quartz substrate with a diameter of 100 m was placed on a substrate holder, and the substrate temperature was maintained at 300°C. SiH in the sample chamber
420 cc/min and 0.225 cc/min were introduced, the microwave power was set to 200 W, and the 8102 layer serving as the cladding layer was deposited on the substrate to a total thickness of 1 μm for 20 minutes. Next, the substrate temperature and microwave power were the same under the same conditions.
02 G30 2 layers were deposited to a total thickness of 10 μm. For the substrate on which the 5102 cladding layer and the 5i020e02 core layer obtained above were completely formed, a pattern was created by a conventional method, and then a cladding layer was further formed under the same conditions as for the above cladding layer creation to obtain an optical waveguide layer.

The loss of the optical waveguide of the present invention obtained from the above is α1d
The loss was lower than that of conventional products manufactured using B/Kyn and thermal C'7D methods. Also, the loss distribution in that cross section is
As shown in FIG. 2(a), the same value (11aB/Km) was obtained in the 90-diameter bleached round part of the n part, showing an extremely high uniformity of ±5 coefficient. For comparison, thermal CV
The loss distribution in the cross section of the conventional product obtained by method D is shown in Figure 2 (b).
It was extremely non-uniform within ±45%. In Figures 2 (a) and (b), the white areas are loss [1l
bB/Km or less, satin part Q, 24871m or less,
The shaded area means α34871m or less. It can be seen that the product of the present invention has excellent uniformity.

〔Effect of the invention〕

As described above, in the present invention, by depositing the waveguide layer while keeping the substrate temperature low, it is possible to control the film thickness with good uniformity.
Warpage of the board can also be reduced.

Moreover, since the deposition rate can be controlled by the plasma power density, degree of vacuum, and gas flow rate, the reproducibility of film thickness and film quality is improved. In the conventional technology, the refractive index changes due to fluctuations in the gas flow rate during deposition and the state of parallel fibers, and propagation loss increases due to non-uniformity of the film thickness. Low-temperature plasma O with easy flow and temperature control
By using VD, the above-mentioned lack/ik can be suppressed.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an embodiment of the present invention. FIGS. 2(a) and 2(b) are cross-sectional views showing the loss distribution in the radial direction of four optical wave paths, in which (a) shows the product of the present invention, (
B) is a diagram of a conventional product made by the thermal OVD method. FIG. 3 is a cross-sectional view illustrating the entire optical waveguide layer, FIG. 4 is a conceptual diagram illustrating the entire conventional thermal C''/D method, and FIG. 5 is a conceptual diagram illustrating the conventional flame direct deposition method.

Claims (3)

[Claims] (1) A method for manufacturing an optical waveguide layer, which comprises forming an SiO_2 film on a substrate by plasma decomposing a gas containing Si and a gas containing O. (2) The method for manufacturing an optical waveguide layer according to claim (1), wherein the plasma decomposition is microwave plasma decomposition. (3) The method for manufacturing an optical waveguide layer according to claim (1) or (2), wherein the substrate is maintained at a temperature of 500° C. or lower.