JPH053748B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a hybrid optical integrated circuit in which an optical waveguide and active optical elements such as receiving and emitting elements are provided on the same substrate, and a method for manufacturing the same. .

[Summary of the Disclosure] The present invention relates to a hybrid optical integrated circuit in which an optical waveguide and an active optical element such as a receiving/emitting element are provided on the same substrate. , an optical element guide and an electrical wiring support base, a first conductive film disposed on the substrate, and an optical waveguide, an optical fiber guide, an optical element guide, and an electrical wiring support base, each of which is disposed on the upper surface of the optical waveguide, the optical fiber guide, the optical element guide, and the electrical wiring support base so as to be insulated from each other. A second conductive film is provided, and an optical fiber and an optical element are arranged along an optical fiber guide and an optical element guide, respectively, and power is supplied from the first and second conductive films to an optical element that requires power supply. This technology allows electrical wiring patterns to be freely placed without being constrained by differences in height on the substrate surface due to the formation of optical waveguides and guides, and also simplifies the manufacturing process because there is no need for the mask alignment process using multiple masks. and a method for manufacturing the same.

Note that this summary is provided solely for the purpose of quickly accessing the technical content of the present invention, and does not have any influence on the technical scope of the present invention or the interpretation of rights.

[Prior Art] Attempts have been made for a long time to realize a hybrid optical integrated circuit by incorporating active optical elements such as a light emitting element and a light receiving element on a substrate on which a low-loss optical waveguide is formed, but all of them have been based on the basic principle. Staying at the confirmation stage,
Hybrid optical integrated circuits that can be put to practical use in the field of optical communications and the like have not yet been provided.

To construct a hybrid optical integrated circuit, (1) Form an optical waveguide on the substrate.

(2) Place the active optical device at the appropriate position at the end of the optical waveguide.

(3) Provide electrical wiring for receiving and supplying power to the active optical element.

This process is necessary.

The present inventor previously applied for ``Waveguided optical module'' (Japanese Patent Application No. 167677-1982) and ``Waveguided optical module and method for manufacturing the same'' (Patent Application No. 59-1982).
209080), provided a method for simultaneously forming an optical waveguide itself and a guide for aligning the optical axis of an active optical element to an appropriate position at the end of the optical waveguide from a planar quartz-based optical waveguide film formed on a silicon substrate. .

This guiding method has greatly reduced the labor involved in aligning optical waveguides with active optical elements and input/output optical fibers, which has traditionally been a major obstacle in constructing hybrid optical integrated circuits. Electrical wiring for receiving and supplying power had to rely on spatial wiring using gold wire. As a result, in hybrid optical integrated circuits, which occupy a relatively large chip area compared to electrical ICs, the length of the gold wire is several millimeters or more, and reliability problems such as instability due to mechanical vibration occur.

In order to solve this drawback, it is possible to provide an electrical wiring pattern on the substrate, but after forming the optical waveguide and guide, there are several
There was a problem in that the difference in height was as much as 10 μm, making it extremely difficult to perform photolithography processes for forming electrical wiring patterns, such as applying photoresist. It may be possible to form an electrical wiring pattern in advance before forming an optical waveguide film on the substrate, but if the formation requires a high temperature of 1200°C or higher, such as with a quartz-based optical waveguide film, it may be necessary to form an electrical wiring pattern on the substrate. There was a problem that the pattern was destroyed.

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to solve the above-mentioned problems and provide a hybrid optical integrated circuit in which the electrical wiring pattern is configured to be suitable for practical use.

Another object of the present invention is to solve the above-mentioned problems, to form an electrical wiring pattern with high accuracy and reliability using a single photomask, and to improve assembly workability by integrating a mixed optical system. An object of the present invention is to provide a method for manufacturing a circuit.

[Means for Solving the Problems] In order to achieve these objects, the hybrid optical integrated circuit of the present invention has an electrical wiring pattern that insulates and holds not only the optical waveguide and guide on the substrate but also the electrical wiring pattern from the substrate. The support base is also constructed using the same optical waveguide film as a starting material.

In the manufacturing method of the present invention, an optical waveguide, a guide, and an electrical wiring pattern support are simultaneously formed using only one photomask containing patterns corresponding thereto.

[Function] According to the present invention, unlike conventional techniques, electrical wiring patterns can be freely arranged without being constrained by height differences on the substrate surface due to the formation of optical waveguides and guides, and there is no need for the process of mask alignment using multiple masks. Therefore, the manufacturing process is also simplified.

[Example] The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the hybrid optical integrated circuit of the present invention, and this example is an example in which a multiplexer/demultiplexer for wavelength division multiplexing communication is configured. Here, 1 is a silicon (Si) substrate,
2 is a silica optical waveguide, 3 is an optical fiber guide,
4 is an input/output optical fiber, 5 is a filter guide,
6 is an interference film filter chip, 7 is a laser guide, 8 is a laser diode, 9 is a microreflector, 1
0 is an advanced photodiode (APD), 11
are amplifier chips for APD10, 12a, 12b,
12c, 12d, 12e, 12f, 12g, 12
Reference numerals h, 12i, and 12j are electrical wiring pattern support stands, the upper surfaces of which are coated with metal conductors to form electrical wiring patterns. The vacant surface of the Si substrate 1 is coated with a metal conductor film to constitute a common electrode surface 13. The gold wire illustrated with reference numeral 14 is a short-distance auxiliary wiring that connects the electric wiring pattern and the laser diode.

The optical fiber 4 is housed and fixed in the optical fiber guide 3, and its optical axis is aligned with the end surface of the optical waveguide 2. The laser diode 8 is bonded by a laser guide 7 onto the substrate 1 at a proper position of the end 2a of the optical waveguide 2. The interference film filter chip 6 is held by a filter guide 5 so as to form an appropriate angle with the optical waveguide 2.

The micro-reflector 9 is arranged at the other end 2b of the optical waveguide 2, and is used to guide the emitted light from the optical waveguide 2 by changing the traveling direction by 90 degrees to the APD 10 installed at one end of the electrical wiring pattern support stands 12a, 12b. It is something. The APD 10 has two power supply pads 15a and 15b on its lower surface, which are electrically coupled to the conductive surfaces on the supports 12a and 12b. A portion of the support stands 12a and 12b also serves as a guide for installing the micro-reflector 9 and a marker for mounting the APD 10 at a proper position.

In FIG. 1, an amplifier chip 11 and electrical wiring patterns 12a, 12b, 12c, 12d, 1
2e, 12f, and 12g are connected using gold wire auxiliary wiring, but if the amplifier chip 11 is equipped with appropriate bonding terminals, it can be connected directly to these electrical wiring patterns without going through auxiliary wiring. Of course, they can be combined.

In FIG. 1, an optical waveguide 2, guides 3, 5,
7, and electrical wiring pattern support stands 12a to 12
j are constructed using the same quartz-based glass film as a starting material.

The entire substrate of FIG. 1 can be packaged in a suitable container (not shown in FIG. 1).

To operate the optical multiplexer/demultiplexer _shown in FIG. Introduce. This signal light is reflected by the interference film filter chip 6 and guided to the optical fiber 4.

On the other hand, the signal light (wavelength λ ₂ ) introduced into the optical waveguide 2 via the optical fiber 4 passes through the interference film filter chip 6 , undergoes optical path conversion by the microreflector 9 , and is guided to the APD 10 . An electrical wiring pattern 12 is connected to the APD 10 via an amplifier chip 11.
A bias voltage is applied by terminals a and 12b, and the signal voltage is amplified by an amplifier chip 11 and output to electrical wiring patterns 12c and 12d. The electrical wiring patterns 12f and 12g are electrical wiring patterns for applying a power supply voltage to the amplifier chip 11.

As described above, in the hybrid optical integrated circuit of the present invention, the optical waveguide, the guide, and the electrical wiring pattern support are collectively constructed based on the same silica-based glass optical waveguide film, so that the structure is simple and the circuit is simple. It is easy to design and suitable for mass production. Compared to the conventional technology, which required long-distance connections using gold wires to reach the leads of the package container, the present invention can minimize the amount of auxiliary wiring using gold wires, greatly improving reliability. Improved. Moreover, since the electrical wiring patterns are provided on the supports 12a to 12j made of quartz glass,
It is electrically completely insulated from the Si substrate 1, and is effective in suppressing crosstalk between the APD output signal and the laser diode drive signal.

Figures 2A to 2D show an embodiment of the method for manufacturing a hybrid optical integrated circuit according to the present invention, and are cross-sectional views taken along line AA' of the configuration diagram of the hybrid optical circuit shown in Figure 2A. , FIGS. 2B, C, and D show the sequential manufacturing steps.

In FIG. 2A, 21 is a Si substrate, 22 is an optical waveguide, 23 is an optical fiber guide, and 24 is an electric wiring pattern support, on the upper surface of which a metal conductor film is formed.

To manufacture such a hybrid optical integrated circuit, as shown in FIG. 2B, first, a silica-based glass film 25 is formed on a Si substrate 21. This quartz-based glass film 25 includes a buffer layer 25A (15 μm thick), a core layer 2
5B (45 μm thick) and cladding layer 25C (10 μm thick)
It consists of a three-layer structure (thickness). Since the total thickness of the quartz-based glass film is as thick as approximately 70 μm, it is preferable to use a soot process for its formation. That is, glass fine particles synthesized by a flame hydrolysis reaction of a glass-forming raw material gas containing _SiCl4 as a main component are deposited on the Si substrate 21, and then heated in an electric furnace.
By heating to about 1300° C., the glass particles are sintered and made into transparent glass, thereby forming the glass film 25. Here, the above-mentioned three-layer structure can be realized by temporally changing the dopant concentration in the glass-forming raw material gas during deposition of glass fine particles. This three-layered quartz-based glass film acts as an optical waveguide film.

Next, the quartz-based glass film 25 is etched by a photolithography process using reactive ion etching.
By removing unnecessary portions, an optical waveguide 22, an optical fiber guide 23, and an electrical wiring pattern support 24 are formed as shown in FIG. 2C. The side surfaces of the optical waveguide 22 and the like after reactive ion etching are approximately vertical.

Incidentally, a side cladding may be formed on the side surface of the optical waveguide 22 if necessary. In this case, it is effective to deposit a SiO ₂ glass film to a thickness of about several μm by means such as sputtering, CVD, or plasma CVD.

It is recommended to selectively remove the SiO ₂ glass film attached to the silicon substrate surface other than the side surfaces by performing reactive ion etching using fluorine-based gas for a short period of time. This is desirable when the silicon substrate is expected to have an efficient heat sink effect for the like.

Next, as shown in FIG. 2D, an Al/Au composite film is vacuum-deposited as a metal conductor material from the upper surface of the substrate 21 to form an electrical wiring pattern 26 and a common electrode surface 2.
form 7. The metal conductor material slightly attached to the side surfaces of the optical waveguide 22 and the support base 24 can be removed by immersing the substrate in a metal etching solution for a short time.

Note that the metal conductor material is formed not only on the upper surface of the support base 24 but also on the upper surface of the optical waveguide 22 and the upper surface of the guide 23, but this does not pose a practical problem and the optical waveguide 2
2 or the guide 23 may also serve as a part of the electrical wiring pattern support base 24.

After the process shown in FIG. 2D is completed, the optical fibers, laser diodes, etc. are placed in appropriate positions guided by the guide 23, auxiliary wiring is provided with gold wire as necessary, and finally the device is placed in a container. , completes the fabrication of the hybrid optical integrated circuit of the present invention.

When housing the hybrid optical integrated circuit of the present invention as described above in a container, the upper surface of the hybrid optical integrated circuit is
Covering with a low refractive index resin such as silicone resin or silicone bonding agent is suitable for preventing Fresnel reflection at the optical fiber connection portion and the insertion portion of the interference film filter chip. This also has the effect of preventing an increase in optical loss due to minute irregularities on the side surface of the optical waveguide.

In fact, when molded with a silicone bonding agent with a refractive index matched to SiO ₂ glass, the optical loss of the optical waveguide decreases from 0.5 dB/cm (with exposed sides) to 0.1 dB/cm at a wavelength of 1.3 μm. and decreased.

In order to more actively reduce the optical loss of the optical waveguide, in the step shown in FIG. 2, after the reactive ion etching is completed, a few micrometers of SiO ₂ is deposited on the side surface of the optical waveguide 23 before the vacuum deposition of the metal conductor material. By adding a step of forming a glass film (side cladding layer), the hybrid optical integrated circuit of the present invention can be housed in a high refractive index resin (such as an epoxy resin) other than silicone resin or silicone bonding agent. It becomes possible.

In order to form such a side cladding layer, in the process shown in FIG. 2C, after the reactive ion etching is completed, high frequency sputtering or silane gas (SiH ₄ ) is applied to the entire upper surface of the substrate 21 targeting the quartz glass plate. After forming a SiO ₂ film with a thickness of several μm using the CVD method or plasma CVD method as a raw material, reactive ion etching is performed for a short time to remove the SiO ₂ film deposited on the side surfaces of optical waveguides, etc. A method of removing unnecessary SiO ₂ film on the surface can be used.

Leaving an unnecessary SiO ₂ film on the surface of the silicon substrate 21 is undesirable because it becomes an obstacle when bonding a laser diode or the like to the substrate surface in a later step. This is because the SiO ₂ film interferes with the heat sink effect of the silicon substrate. Since reactive ion etching has high etching anisotropy depending on the direction of ion irradiation, by controlling the direction in which the substrate is placed during the etching process, it is possible to selectively leave the SiO ₂ film on the side surface of the optical waveguide.

Incidentally, since a SiO ₂ film is formed on the side surface of the optical fiber guide 23 as well as on the side surface of the optical waveguide 22, it is necessary to design the interval between the guides 23 taking into account the thickness of the SiO ₂ film. Of course there is.

If the thickness of SiO ₂ is less than 1 μm, the side cladding effect is insufficient and the optical electric field spreads to the outside of the side cladding layer, so molding with high refractive index resin such as epoxy resin is not desirable. . The reason for this is that the light propagating in the optical waveguide passes through the side cladding layer, which is too thin, and transfers to the resin portion. Conversely, the thickness of the SiO ₂ film is 10 μm.
Exceeding this value tends to cause cracks in the SiO ₂ film, and the dimensional changes of the guide portion become drastic, making prospective design difficult. This method is unsuitable because it becomes difficult to selectively remove the unnecessary SiO ₂ film by reactive ion etching. Necessary and minimum amount determined experimentally
The SiO ₂ film thickness was approximately 2 μm. In fact, using a quartz glass plate as a target, a 2 μm thick layer was formed as a side cladding layer using the high frequency sputtering method.
The optical loss of an optical waveguide formed with a SiO ₂ film is 1.3μ at a wavelength of
The optical propagation loss was 0.1 dB/cm or less at m, and no increase in optical propagation loss was observed even when molded with epoxy resin.

In the manufacturing method shown in the above embodiment, the optical waveguide 22, the guide 23, and the electrical wiring pattern support 24 can be formed simultaneously using only one photomask pattern, and the electrical wiring pattern 26 can be formed simultaneously. Since it can be formed all at once by a simple process of subsequent vacuum evaporation, both reliability and economical efficiency are greatly improved.

Although the structure and operation of the present invention have been explained above using a quartz-based optical waveguide on a Si substrate as an example, the present invention can also be applied to the structure and manufacture of hybrid optical integrated circuits using other substrate materials and optical waveguide materials. Of course, it can also be applied.

[Effects of the Invention] As explained above, according to the present invention, in addition to a guide for installing optical waveguides, optical fibers, and active optical elements on a substrate, electrical wiring patterns can be accurately formed using a single photomask. , which improves assembly workability and reliability, making it possible to realize a practical hybrid optical integrated circuit.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of an optical multiplexer/demultiplexer as an embodiment of the present invention, FIG. 2A is a perspective view showing an example of a hybrid optical integrated circuit obtained by the manufacturing method of the present invention, and FIG. Figures B to D are cross-sectional views showing an example of the steps of the manufacturing method. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Optical waveguide, 3... Optical fiber guide, 4... Optical fiber, 5... Filter guide, 6... Interference film filter chip, 7...
Laser guide, 8... Laser diode, 9...
...Microreflector, 10...Avalanche photodiode, 11...Amplifier chip, 12a, 12b,
12c, 12d, 12e, 12f, 12g, 12
h, 12i, 12j...Electric wiring pattern and support stand, 13...Common electrode surface, 14...Auxiliary wiring (gold wire), 21...Substrate, 22...Optical waveguide, 23
...Optical fiber guide, 24...Electric wiring pattern support stand, 25...Quartz-based glass film, 25A...
...Buffer layer, 25B... Core layer, 25C... Clad layer, 26... Electrical wiring pattern, 27...
Common electrode surface.

Claims (1)

[Scope of Claims] 1. An optical waveguide, an optical fiber guide, an optical element guide, and an electrical wiring support, which are formed of the same member on a substrate and arranged in a convex shape with approximately equal height; a first conductive film disposed on at least the upper surface of the electrical wiring support and insulated from the first conductive film; and a second conductive film disposed along the optical fiber guide and the optical element guide, respectively. 1. A hybrid optical integrated circuit comprising an optical fiber and an optical element, wherein power is supplied from the first and second conductive films to the optical element that requires power supply. 2. A step of forming an optical waveguide film on the substrate; a step of etching the waveguide film to form a convex optical waveguide, an optical fiber guide, an optical element guide, and an electrical wiring support; and a step of forming a conductive film on at least the upper surface of the electrical wiring support, a step of arranging the optical fiber and the optical element along the optical fiber guide and the optical element guide, respectively, and requiring power supply. A method for manufacturing a hybrid optical integrated circuit, comprising the step of forming a power supply path through the conductive film in an optical element. 3. In manufacturing a hybrid optical integrated circuit by forming an optical waveguide on a substrate and coupling an active optical element to the optical waveguide, the steps include: forming an optical waveguide film on the substrate; and etching the optical waveguide film. Thereby, the step of simultaneously forming the optical waveguide, a guide for positioning the optical fiber and the active optical element with respect to the optical waveguide, and an electric wiring pattern support for receiving and supplying power to the active optical element; A method for manufacturing a hybrid optical integrated circuit, comprising the steps of: coating a conductor film on an electrical wiring pattern support; and fixing the optical fiber and the active optical element to the guide. 4. The substrate is a silicon substrate, and after forming a quartz-based optical waveguide film on the silicon substrate, the optical waveguide, the guide, and the electrical wiring pattern support are formed by reactive ion etching. A method for manufacturing a hybrid optical integrated circuit according to claim 3.