JPH07181336A - Optical waveguide circuit and its manufacture - Google Patents

Abstract

PURPOSE:To realize high function property, high reliability and lower cost by providing an optical waveguide circuit with the characteristics of both an optical waveguide circuit using a semiconductor base and an optical waveguide circuit using a glass base. CONSTITUTION:A Si base 1 is put on a lower electrode 16 with heater, and a glass base 2 containing alkali metal ion is superposed on the Si base 1. A waveguide having a clad 3 and a core 4 is formed on the glass base 2. An upper electrode 17 is pushed onto the upper part of the clad 3. It is heated by the heater of the lower electrode 16 with heater to set the electrode temperature to 100 deg.C-500 deg.C. Several hundreds V-several kV of a DC voltage 18 is applied between the upper electrode 17 and the lower electrode 16, whereby an electrostatic attractive force is generated between the Si base 1 and the glass base 2 to cause a chemical bonding on the critical surface. Thus, an optical waveguide circuit in which both the bases 1, 2 are integrally connected without using an adhesive can be constituted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide circuit constructed by bonding a semiconductor substrate such as a Si substrate and a glass substrate together and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the progress of optical fiber communication, optical circuits are required to have higher functionality, higher reliability, and lower cost. Optical waveguides are one of the optical circuit technologies that satisfy these requirements. It's getting a lot of attention.

As an optical waveguide circuit, as shown in FIG.
The structure in which the clad 3 is formed on the substrate 1 and the core 4 is embedded in the clad 3 is common. As a material of the substrate 1, a material using a semiconductor (for example, Si, InP, etc.) and a material using glass (for example, quartz glass, multi-component glass, etc.) are being studied.

In order to make an optical / electronic device based on this, it is necessary to form an optical circuit, an electronic circuit or the like in the optical waveguide circuit. In such an optical waveguide circuit, an optical passive circuit such as a star coupler, an optical branching circuit, an optical multiplexing / demultiplexing circuit, and an optical filter is formed as an optical circuit, and an optical amplifier circuit, a semiconductor laser, an optical receiving element, or the like. It is considered that an active circuit is formed. In addition, as an electronic circuit, a circuit formed in a light waveguide circuit by a hybrid instead of a monolithic is being studied.

However, since the optical circuit and the electronic circuit are manufactured by different manufacturing methods using different materials, the base substrate needs a substrate made of a material suitable for them. That is, in the optical waveguide circuit using the glass substrate, optical passive circuits such as an optical branch circuit, an optical star coupler, an optical multiplexing / demultiplexing circuit, and an optical filter circuit can be realized with low loss.

On the other hand, in an optical waveguide circuit using a semiconductor substrate, an optical active circuit such as a semiconductor laser, a light receiving element, an optical amplifier circuit, an optical modulator circuit can be easily constructed, and an electronic circuit (driving circuit, amplifier, Circuits for modulation, oscillation, logic, etc.)
Can also be configured.

Therefore, in order to form such an optical passive circuit, an optical active circuit, an electronic circuit, etc. in an optical waveguide circuit, unless a plurality of material substrates are used, other elements are fitted on a single material substrate. There is no choice but to make it a hybrid type.

[0008]

As described above, the conventional optical waveguide circuit has the following problems.

(1) There is no optical waveguide circuit formed by integrally bonding a semiconductor substrate such as a Si substrate and a glass substrate, except that using an adhesive. Those using adhesives have many defects such as peeling and thermal properties, and are not practical. Therefore, the features of the optical waveguide circuit using the Si substrate,
A defect-free optical waveguide circuit that combines the features of an optical waveguide circuit using a glass substrate has not yet been realized.

(2) Since it is inevitable to form a hybrid type in which other elements are fitted into a single material substrate, an optical waveguide circuit in which an optical circuit and an electronic circuit are formed in a monolithic or nearly monolithic form is simple, It cannot be manufactured at low cost and with high reliability.

Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the conventional technique by combining the characteristics of an optical waveguide circuit using a semiconductor substrate and the characteristics of an optical waveguide circuit using a glass substrate, and Loss, high functionality and high reliability,
Another object of the present invention is to provide an optical waveguide circuit capable of realizing cost reduction.

Another object of the present invention is to provide a method for manufacturing an optical waveguide circuit in which a semiconductor substrate and a glass substrate can be easily attached to each other and they are not easily peeled off.

[0013]

According to a first aspect of the present invention, a glass substrate containing alkali metal ions is bonded to the surface of a semiconductor substrate, and the refractive index is higher than that in the clad on the glass substrate. In the optical waveguide circuit, a core having a substantially rectangular cross section is embedded.

A second aspect of the present invention constitutes an optical waveguide circuit in which a clad is formed on a semiconductor substrate and a core having a refractive index higher than that of the clad and having a substantially rectangular cross section is embedded in the clad. A clad is formed on a glass substrate containing ions, and another optical waveguide circuit in which a core having a substantially rectangular cross section is embedded is formed in the clad, and these optical waveguide circuits are integrated through a metal film. It is a laminated optical waveguide circuit.

According to a third aspect of the present invention, a glass substrate containing alkali metal ions is bonded to both the front surface and the back surface of the semiconductor substrate, the refractive index is higher than that in the clad on the glass substrate, and This is an optical waveguide circuit having a rectangular core embedded therein.

A fourth invention is an optical waveguide circuit according to any one of the first to third inventions, characterized in that an electronic circuit is integrated on a semiconductor substrate.

According to a fifth aspect of the invention, in the optical waveguide circuit of the first to fourth aspects, at least one active optical element such as a light emitting element or a light receiving element, and a passive element such as a lens, a filter or an optical fiber are mounted. The optical waveguide circuit is characterized in that

A sixth invention is the optical waveguide circuit according to any one of the first to fifth inventions, which is an optical waveguide circuit having a core and a clad, an optical branch circuit, an optical star coupler, an optical multiplexer / demultiplexer, an optical ring resonator, The optical waveguide circuit is characterized in that at least one of optical circuits such as an optical filter, an optical switch, and an optical modulator is formed.

A seventh invention is the optical waveguide circuit according to the first to sixth inventions, wherein the semiconductor substrate is a Si substrate, GaAs, and I.
An optical waveguide circuit characterized by using any one of nP substrates.

An eighth aspect of the present invention is a method for manufacturing an optical waveguide circuit by integrally bonding a glass substrate and a semiconductor substrate, wherein when the glass substrate and the semiconductor substrate are integrally bonded, the semiconductor is placed on the electrode. An optical waveguide circuit characterized in that a substrate and a glass substrate are superposed and heated to a predetermined temperature, and a predetermined voltage is applied between the electrode and the glass substrate to integrally bond the semiconductor substrate and the glass substrate. Is a manufacturing method.

[0021]

In the optical waveguide circuit of the present invention, the optical waveguide circuit using the glass substrate and the optical waveguide circuit using the semiconductor substrate are integrally bonded, so that the characteristics of the respective optical waveguide circuits can be matched. it can.

That is, in the optical waveguide circuit using the glass substrate, it is possible to realize an optical passive circuit such as an optical branch circuit, an optical star coupler, an optical multiplexing / demultiplexing circuit and an optical filter circuit with low loss.
On the other hand, in an optical waveguide circuit using a semiconductor substrate, an optical active circuit such as a semiconductor laser, a light receiving element, an optical amplifier circuit, and an optical modulator circuit can be easily configured, and an electric circuit (drive circuit, amplification, modulation, oscillation, Circuits such as logic) can also be configured.

As described above, the optical waveguide circuit of the present invention can have the functions of both the optical waveguide circuits, and can achieve higher functionality than ever before. Further, since the optical passive circuit and the optical active circuit can be integrated with high density, high performance and low cost can be achieved.

Moreover, the glass substrate and the semiconductor substrate are integrally bonded by the anodic bonding method. That is,
A semiconductor substrate and a glass substrate are superposed on the heater electrode, and a predetermined voltage (several hundred V to several) is applied between the heater electrode and the glass substrate.
kV) is applied and the substrate is heated by a heater to a predetermined temperature (100 to several hundreds of degrees Celsius) to generate an electrostatic attractive force between the semiconductor substrate and the glass substrate, thereby causing a chemical bond at the interface to bond them. I have to.

By using this anodic bonding method, it is possible to integrally bond two or more optical waveguide circuits by interposing a metal film for bonding between the optical waveguide circuits. Alternatively, glass substrates can be integrally attached to the front and back of the semiconductor substrate.

Therefore, the two substrates can be adhered to each other with good adhesion, and an integrated optical waveguide circuit close to monolithic can be realized. Moreover, since an adhesive agent is not used at the interface and they can be bonded in a clean atmosphere in an extremely short time (within 10 minutes), it is possible to realize a highly reliable optical waveguide circuit.
Further, since the optical waveguide circuit of the present invention is configured by integrally bonding two substrates made of different materials, the optical waveguide circuit having the function and performance more than double the area of the conventional optical waveguide circuit. Can be easily and quickly created, resulting in high functionality
A high-performance optical waveguide circuit can be realized at low cost.
Therefore, it is possible to realize a high-performance waveguide having both functions of a glass waveguide and a semiconductor waveguide.

If the semiconductor substrate is a Si substrate, the structure of the light receiving diode or the electronic circuit will be easy, and if the semiconductor substrate is a GaAs substrate or the InP substrate, the structure of the semiconductor laser or the light emitting diode will be easy.

[0028]

FIG. 2 shows a first embodiment of the optical waveguide circuit of the present invention. This is a cross-sectional view. In this embodiment, Si is used for the substrate 1, but other than this, GaAs or I
nP may be used. A glass substrate 2 containing alkali metal ions (Na, K, Li, etc.) is integrally bonded on a Si substrate 1. Since the glass substrate 2 contains alkali metal ions, the Si substrate 1 and the glass substrate 2
As will be described later, can be easily bonded by using an anodic bonding technique.

For the glass substrate 2 containing the alkali metal ions, for example, borosilicate glass (product name 7740, 7040, 7050, 7760, etc.) manufactured by Corning, USA is used. A waveguide including a core 4 and a clad 3 (here, the waveguide is used separately from an optical waveguide circuit including the substrate) is provided on a glass substrate 2 containing alkali metal ions. For example, a SiO _x N _y H _z film is used for the core 4 and the clad 3, and N is used for the core 4.
A SiO _x N _y H _z film having a concentration of 20 atomic% (refractive index 1.55) and a SiO _x N _y H _z film having an N concentration of 4 atomic% are used for the cladding 3. The pattern of the core 3 having a substantially rectangular cross section is composed of a combination of straight lines, parallel lines, curves, Y-shapes, rings, etc., and an optical branching / multiplexing circuit, an optical star coupler, an optical multiplexing / demultiplexing circuit, an optical interference circuit, An optical ring resonator, an optical switch circuit, etc. are configured. FIG. 3 shows a second embodiment of the optical waveguide circuit of the present invention. A cross-sectional view is shown as in FIG. 2. The difference from FIG. 2 is that a buffer layer 5 is provided between the glass substrate 2 containing the alkali metal ions and the cladding 3. The buffer layer 5 can be made of glass such as silica glass containing no alkali metal ions. The insertion of the buffer layer 5 is effective in reducing the propagation loss of the optical waveguide circuit.

FIG. 4 shows an optical waveguide circuit according to a third embodiment devised for attaining high functionality, based on the basic structure shown in FIGS. That is, the electronic circuit 6 is previously formed on the Si substrate 1.
-1 and 6-2 are integrated. These electronic circuits are, for example, pulse drive circuits that apply a pulse voltage to the thin film heaters 7-1 and 7-2 provided on the front and back sides of the waveguide including the core 4 and the clad 3.

These heaters 7-1 and 7-2 are for thermally changing the relative refractive index difference between the core 4 and the clad 3 forming the waveguide, and are for the polarization of the optical signal propagating in the core 4. It is used for controlling the wavefront or for tuning the optical frequency to be demultiplexed in a Mach-Zehnder type optical circuit.

The electronic circuits 6-1 and 6-2 may be circuits for amplification, oscillation, modulation, logic, etc. other than the drive circuits. In this way, the waveguide and the electronic circuit can be separately prepared in advance on the glass substrate 2 and the Si substrate 1 and integrated later, so that the highly functional optical / electronic integrated device can be manufactured at low cost and with high reliability. You will be able to make it better. In FIG. 4, the electronic circuits 6-1 and 6-2 and the heater 7 are
Although not shown, the lead conductors or lead wires for connecting -1, 7-2 are actually provided by appropriate means.

FIG. 5 shows a fourth embodiment of the high-performance optical / electronic device of the present invention. This is a Si substrate 1 in which an electronic circuit 6 for driving a semiconductor laser is integrated in advance,
A glass substrate 2 having a waveguide formed of a core 4 and a clad 3 is integrally bonded, and a single semiconductor laser 11 and an optical fiber 8 are further mounted. The electronic circuit 6 is integrated on the surface of the Si substrate 1 corresponding to the mounting position of the semiconductor laser 11.

The semiconductor laser 11 is fitted into one end of the waveguide on the glass substrate 2, and the optical fiber 8 is connected to the other end of the waveguide so that the light of the semiconductor laser 1 driven by the electronic circuit 6 is guided into the waveguide. It is propagated in the core 4 and is coupled in the core 10 of the optical fiber 8 to achieve high functionality and high performance. In the figure, 9 is a clad of the optical fiber 8. In addition,
Lead conductors for connecting the electronic circuit 6 and the semiconductor laser 11 are omitted.

As the optically active element, in addition to the semiconductor laser 11, a light receiving element, an optical amplifying element or the like can be mounted. Further, a passive optical component such as a spherical lens or a rod lens can be mounted between the semiconductor laser 11 and the waveguide including the core 4 and the clad 3. By inserting such a passive optical component, the light of the semiconductor laser 11 can be coupled into the core 4 with higher efficiency.

FIG. 6 shows a fifth embodiment in which an optical waveguide circuit is combined. This is the core 13 on the Si substrate 1.
A first optical waveguide circuit is formed by providing a waveguide composed of the cladding 12 and the clad 12, and the WSi film 14 is formed thereon. On the other hand, a waveguide including the core 4 and the clad 3 is provided on the glass substrate 2 containing alkali metal ions to form a second optical waveguide circuit. The first optical waveguide circuit and the second optical waveguide circuit are integrally bonded with the WSi film 14.

Therefore, in this embodiment, two optical waveguide circuits having different functions can be integrated on the same area as the conventional one, so that the optical signal processing function more than double that of the conventional one can be provided. . The WSi film 14 functions as a film for bonding the two optical waveguide circuits by the anodic bonding method. Other than the WSi film, a metal film of Au, Ag, Al or the like may be used. Further, the number of optical waveguide circuits to be bonded may be three or more. In this case, Si substrate, glass substrate, Si
It is preferable that the Si substrate and the glass substrate are alternately bonded to each other like a substrate, but the same substrate may be continuous.

FIG. 7 shows a sixth embodiment according to another composite optical waveguide circuit of the present invention. In each of the above-mentioned embodiments, the glass substrate is bonded only to the surface of the Si substrate 1. In the present embodiment, not only the front surface of the Si substrate 1 but also the back surface thereof is integrally bonded with the glass substrate 2 containing alkali metal ions. A clad 3 is formed on each glass substrate 2, and a core 4 having a higher refractive index and a substantially rectangular cross section is embedded in the clad 3. With such a configuration, it is possible to achieve high functionality and high performance similar to those in FIG.

FIG. 8 shows a seventh embodiment of the high-performance optical / electronic device of the present invention. The difference from FIG. 5 is that
The point is that an InP substrate 15 serving as a base of a semiconductor laser is mounted on an end portion of the Si substrate 1 which is exposed by removing a part of the waveguide, and the semiconductor laser 11 is formed thereon. An electronic circuit 6 for driving the semiconductor laser 11 is integrated on the back surface side of the Si substrate 1. The lead conductor is omitted. As described above, when the InP substrate, which is the base of the semiconductor laser, is directly mounted on the Si substrate 1, the linear expansion coefficient of the same semiconductor is similar to that when the semiconductor laser is mounted on the glass substrate. Less core coupling loss due to temperature change.

FIG. 1 shows an embodiment of a method for manufacturing an optical waveguide circuit according to the present invention. This uses a conventionally known anodic bonding method. The Si substrate 1 is placed on the lower electrode 16 with a heater, and the cladding 3 is placed on the Si substrate 1.
And a glass substrate 2 containing an alkali metal ion in which a waveguide including a core 4 is formed is placed and superposed. The upper electrode 17 is pressed against the upper portion of the clad 3. The heater and the power source may be separate bodies.

Then, the heater of the heater-equipped lower electrode 16 is heated to set the electrode temperature to 100 ° C. to 500 ° C. DC voltage 18 of several hundreds V between upper electrode 17 and lower electrode 16
-Si substrate 1 and glass substrate 2 by applying several kV
An electrostatic attractive force is generated between them to cause a chemical bond at the interface to bond them.

Using this anodic bonding method, the optical waveguide circuits shown in FIGS. 2 to 8 were prototyped. A specific example of these prototype results will be described. First, in order to realize the optical waveguide circuit of FIG. 2, a Si substrate 1 having a diameter of 3 inches and a thickness of 0.45 mm is used, and the glass substrate 2 is made of the above-mentioned borosilicate glass (product name 7740, diameter 3 inches). , Thickness 1 mm) was used. The core 4 and the clad 3 are made of the same SiO _x as described above.
It was constructed using N _y H _z films.

Then, the lower electrode 16 with a heater was heated to 200 ° C., and a DC voltage of 1 kV was applied between the upper and lower electrodes 17 and 16. As a result, the joining could be completed in 7 minutes and 20 seconds. Further, as another experiment in which the temperature was changed, when the lower electrode 16 was heated to 500 ° C. and a DC voltage of 1 kV was applied, it was possible to complete the bonding in 6 minutes 31 seconds.

Further, as a method of manufacturing the composite optical waveguide circuit of FIG. 6, a WSi film 14 having a waveguide (thickness 1
The Si substrate 1 with a (μm) is placed on the lower electrode 16, the glass substrate 2 is placed thereon, and the upper electrode 17 is pressed against it, and a DC voltage of 1 kV is applied while the lower electrode 16 is heated to 200 ° C. It was possible to completely bond in just 5 minutes. Similarly, the optical waveguide circuits shown in FIGS. 3, 4, 5, 7, and 8 could be joined.

As described above, according to this embodiment, a semiconductor substrate such as a Si substrate and a glass substrate can be integrally bonded by an anodic bonding method to form an optical waveguide circuit. Of the optical waveguide circuit using
An optical waveguide circuit having the characteristics of the optical waveguide circuit using a glass substrate can be realized. In addition, this optical waveguide circuit is integrated in a nearly monolithic form, simple, low cost,
And it can be made with high reliability.

The present invention is not limited to the above embodiment. First, the cores 4 and 13 and the claddings 3 and 12 are made of SiO _x N.
Instead of _y H _z , SiO ₂ glass, multi-component glass,
A polymer material or the like may be used.

Particularly when a polymer material is used, a very low cost optical waveguide circuit can be realized. For example, polyimide is preferable as the polymer material, and when this is used, the polyimide can also serve as a heat treatment for cross-linking during anodic bonding and can be manufactured more efficiently. Furthermore, the so-called poling phenomenon occurs in which the orientation of the polyimide is aligned due to the discharge between the electrodes during the anodic bonding, and it is possible to give the polyimide core a non-linear effect.

Further, the Si substrate 1 may have an SiO ₂ oxide film formed on its front surface, rear surface, or both surfaces.

[0049]

According to the optical waveguide circuit of the present invention, the following effects can be obtained.

(1) According to the optical waveguide circuit according to the first to seventh aspects, the characteristics of the optical waveguide circuit using the semiconductor substrate and the characteristics of the optical waveguide circuit using the glass substrate can be combined.

(2) According to the optical waveguide circuit according to the second and third aspects, it is possible to realize a high-performance and high-performance optical waveguide circuit having the same area as that of the conventional optical waveguide circuit but more than double the size. .

(3) According to the optical waveguide circuit of claims 4 to 6, a highly functional optical / electronic device in which an optical waveguide type passive circuit, an optical active element, or an electronic circuit element is integrated is highly reliable. It can be easily realized at low cost.

(4) According to the optical waveguide circuit of claim 7, any one of Si, GaAs, and InP is used for the semiconductor substrate. Therefore, an electronic circuit, a light receiving element, a light emitting element, or a semiconductor is selected according to the substrate material. A device such as a laser can be easily configured.

(5) According to the method of manufacturing an optical waveguide circuit described in claim 8, since a composite type optical waveguide circuit can be manufactured by a low temperature process, the optical active element and the electronic circuit element are damaged. Never. In addition, since it is possible to bond two kinds of waveguide substrates made of different materials in a clean atmosphere for a short time, it goes without saying that the adhesive strength is strong.
A highly functional optical waveguide circuit with low loss and high reliability can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a method of manufacturing an optical waveguide circuit of the present invention by an anodic bonding method.

FIG. 2 is a sectional view showing a first embodiment of the optical waveguide circuit of the present invention.

FIG. 3 is a sectional view showing a second embodiment of the optical waveguide circuit of the present invention.

FIG. 4 is a sectional view showing a third embodiment of the optical waveguide circuit of the present invention.

FIG. 5 is a sectional view showing a fourth embodiment of the optical waveguide circuit of the present invention.

FIG. 6 is a sectional view showing a fifth embodiment of the optical waveguide circuit of the present invention.

FIG. 7 is a sectional view showing a sixth embodiment of the optical waveguide circuit of the present invention.

FIG. 8 is a sectional view showing a seventh embodiment of the optical waveguide circuit of the present invention.

FIG. 9 is a cross-sectional view showing a conventional optical waveguide circuit.

[Explanation of symbols]

 1 Si substrate 2 Glass substrate containing alkali metal ions 3 Clad 4 Core 16 Lower electrode with heater 17 Upper electrode 18 DC voltage

Claims (8)

[Claims] 1. A semiconductor substrate on which a glass substrate containing alkali metal ions is integrally bonded, a clad is formed on the glass substrate, and the clad has a higher refractive index than that of the clad and has a substantially rectangular cross section. An optical waveguide circuit having a core embedded therein. 2. An optical waveguide circuit, in which a clad is formed on a semiconductor substrate, and a core having a refractive index higher than that of the clad and having a substantially rectangular cross section is embedded in the clad, the optical waveguide circuit including alkali metal ions. A clad is formed on a glass substrate, another optical waveguide circuit in which a core having a substantially rectangular cross section is embedded is formed in the clad, and these optical waveguide circuits are integrally bonded through a metal film. An optical waveguide circuit characterized by. 3. A glass substrate containing alkali metal ions is integrally bonded to both the front surface and the back surface of a semiconductor substrate, a clad is formed on each glass substrate, and a refractive index is higher than that in the clad. An optical waveguide circuit having a high core and a substantially rectangular cross section embedded therein. 4. The optical waveguide circuit according to claim 1, wherein an electronic circuit is formed on the semiconductor substrate. 5. The optical waveguide circuit according to claim 1, wherein at least one active optical element such as a light emitting element or a light receiving element, or a passive element such as a lens, a filter or an optical fiber is mounted. An optical waveguide circuit characterized in that 6. The optical waveguide circuit according to claim 1, wherein an optical branch circuit, an optical star coupler, an optical multiplexer / demultiplexer, and an optical ring resonance are provided in the optical waveguide circuit having the core and the clad. An optical waveguide circuit in which at least one of optical circuits such as an optical device, an optical filter, an optical switch, and an optical modulator is formed. 7. The optical waveguide circuit according to claim 1, wherein the semiconductor substrate is a Si substrate or GaAs.
An optical waveguide circuit characterized by using either a substrate or an InP substrate. 8. A method of manufacturing an optical waveguide circuit by integrally bonding a glass substrate and a semiconductor substrate, wherein the semiconductor substrate and the glass substrate are placed on electrodes when the glass substrate and the semiconductor substrate are integrally bonded. Is superposed and heated to a predetermined temperature, and a predetermined voltage is applied between the electrode and the glass substrate, whereby the semiconductor substrate and the glass substrate are integrally bonded to each other, and a method for manufacturing an optical waveguide circuit.