JP3264256B2 - Manufacturing method and mounting structure of optical device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a structure for manufacturing an optical device, and more particularly to a method and a structure for manufacturing an optical device in which an optical fiber is mounted without adjustment so as to be coupled to an optical waveguide circuit.

[0002]

2. Description of the Related Art As a method of manufacturing an optical device combining an optical fiber mounted optical waveguide circuit with an optical element and an electric element,
Conventionally, the following methods are known.

For example, as described in JP-A-6-347665, Au, Al, which has durability to an anisotropic etching solution and can be used as an electric wiring layer,
There is a method in which a V-groove forming etching mask and electric wiring are formed on a Si substrate using a material such as a metal such as W or WSi on an Si substrate, and an optical waveguide made of a quartz glass material or the like is formed on the upper layer. In the above publication, the optical component and the electronic device mounted on the substrate on which the optical waveguide is formed, by eliminating the step process, to enable optically efficient coupling between the optical component and the optical waveguide, An optical fiber and an optical semiconductor for the purpose of providing a low-cost optical device manufacturing method by enabling mass production on a substrate scale in all manufacturing steps including formation of electric wiring and pads of an electronic device. A marker for positioning and fixing an optical component such as an element, a marker for setting an optical axis of an optical waveguide, a mask pattern for forming a groove, an electrical wiring for an optical component and an electronic device, and a pad for forming an optical waveguide. There has been proposed a method for manufacturing an optical device, which is characterized in that the optical device is formed on a substrate before.

In this conventional technique, as shown in FIG.
At the same time as forming the waveguide end face 6 by wet etching or dry etching using the optical waveguide end face forming mask 5, the Si substrate face 7a is exposed.

Then, a V-groove for mounting an optical fiber is formed on the Si substrate 1 by anisotropic etching using a V-groove forming etching mask 12.

According to this conventional technique, a V-groove forming etching mask and electric wiring can be formed without a step process after forming an optical waveguide. Therefore, mass production of optical devices on a wafer scale utilizing a photolithography process can be expected.

[0007]

However, the above-mentioned conventional manufacturing method has the following problems.

That is, the mask for anisotropic etching using a material such as the metal described above may be deteriorated by the influence of the optical waveguide forming process on the upper layer of the mask for anisotropic etching. This may be caused by heat in the optical waveguide forming process, and diffusion of dopant and moisture in the optical waveguide layer into the mask.

[0009] Due to this alteration, the anisotropic etching mask loses durability against the etchant. For this reason, it does not function as a mask, and a groove having a desired shape cannot be obtained.

As a result, there arises a problem that the optical fiber cannot be mounted in this groove with high accuracy.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems and to surely form a groove to a substrate on which an optical waveguide is formed irrespective of the method of forming an optical waveguide, and to use an optical waveguide using this groove. It is an object of the present invention to provide a method of manufacturing an optical device that can mount a fiber or a positioning guide pin of a substrate having an optical fiber guide groove with high accuracy.

[0012]

According to the present invention, there is provided an optical device comprising:
The method comprises forming an optical waveguide circuit on a substrate,
The upper optical element and the optical fiber are arranged so as to be optically coupled.
In the method for manufacturing an optical device to be placed, (a) on a substrate, a groove forming etchant of the substrate
Dry layer and second layer of durable material
A first layer of a material that is resistant to
And forming the first layer on a groove forming etching mask of the substrate.
A step of patterning the form of click, after forming the optical waveguide above (b) said first layer, edge
While forming the end face of the optical waveguide by ching,
Exposing the patterned first layer; and (c) using the exposed patterned first layer as a mask.
Etching, the second layer is etched into the groove of the substrate.
Patterning in the form of a etching mask; and (d) using the patterned second layer as a mask,
Step of forming the groove by etching the substrate
And is characterized by including.

Further, the mounting structure of the optical device of the present invention is as follows.
An optical waveguide circuit is formed on the substrate, and an optical element on the substrate and
An optical device in which optical fibers are arranged to optically couple
In the mounting structure of the chair, it is formed on a substrate,
Durability to etchant used for groove formation etching
With a thickness of 100 nm to 1 μm
A second layer and a dry layer formed on the second layer;
First layer made of a material having durability against chucking
And an optical waveguide formed above the first layer.
Layer and the second layer are used for etching to form grooves in the substrate.
Patterned in the shape of the mask and patterned
Etching the substrate using the second layer as a mask
And a light guide formed on the substrate.
The optical path of the optical fiber mounted in the groove provided on the substrate is
Characterized by being optically coupled to the axis
And Further, the second layer is made of an insulating layer, and the first layer is made of
The first layer is made of a conductive material, and the first layer is
May be formed.

[0014]

The principle and operation of the present invention will be described below. In the present invention, the formation of the end face of the optical waveguide and the exposure of the etched surface of the substrate are simultaneously performed by dry etching. At this time, the first layer which has durability against dry etching and is patterned in the shape of a groove forming mask functions as a mask for dry etching of the second layer thereunder. I do. For this reason, the second layer remains in the shape of the groove forming etching mask pattern. The material of this second layer is durable to the etchant of the substrate.

As described above, the material which is originally not durable to the etchant or the material which loses the durableness to the substrate etchant due to the deterioration accompanying the waveguide forming process on the first layer is replaced with the first layer. Can be used to form a groove forming pattern without damage.

Therefore, the groove forming mask can be formed with high accuracy and certainty without depending on the optical waveguide circuit forming process method.

By using a material such as a metal having good electrical characteristics such as high-frequency characteristics as the material of the first layer, Si
It is possible to form electric wiring insulated from the substrate.

[0018]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a view for explaining an example of steps of a method for manufacturing an optical device according to an embodiment of the present invention in the order of steps.

First, a second layer 2 is formed on a substrate 1 such as Si. As a material of the second layer 2, a material that is durable to an etchant used for etching for forming a groove in the substrate 1, for example, a quartz glass mainly containing SiO ₂ or the like is used.

The intended effect of the present invention can be obtained even if a CVD method or a sputtering method is used as a method for forming the SiO ₂ film forming the second layer 2.

However, the thermally oxidized SiO 2 formed by annealing the Si substrate 1 in an H ₂ O atmosphere, etc.
_{The two} films have higher durability against the above etchant than the CVD film and the sputtered film. Therefore, even if the film thickness is reduced, it functions as a mask for etching a substrate in a later step.

On the other hand, immediately before the substrate etching in a later step, considering that at the time of patterning the SiO ₂ film in the shape of the groove forming an etching mask by etching, is better to reduce the thickness of the SiO ₂ film Since the side etching of the film is reduced, the pattern forming accuracy is improved.

For the above reasons, it is preferable to use a thermally oxidized SiO ₂ film rather than a CVD film or a sputtered film.

When thermally oxidized SiO ₂ is used as the second layer 2, the film thickness is usually about 100 nm (in consideration of the selectivity between SiO ₂ and Si when forming a groove using KOH as an etchant in a later step). 1000 angstrom) to 1
μm.

Further, as another material of the second layer 2, thermally nitrided Si ₃ N ₄ formed by annealing the Si substrate 1 in an NH ₃ atmosphere instead of the above SiO ₂ , or a CVD method or a sputtering method It is also possible to use Si ₃ N ₄ by the above method.

Next, the first layer 3 is formed by sputtering or vapor deposition.

The first layer 3 is made of a C _x F _y system or C _x Cl _y
It is made of a material whose etch rate is sufficiently lower (higher in selectivity) than dry etching by reactive gas ions, radicals or neutral molecules in a system or the like as compared with the optical waveguide layer.
Specifically, for example, a film of Au, Al, W, WSi, Cr or the like having a thickness of several hundred nm (several thousand angstroms) to about 1 μm can be used.

Then, the first layer 3 is formed by photolithography and wet etching using chemical
As shown in FIG. 1A, a pattern is formed into a desired groove forming etching mask (see 3a) by an ECR plasma etching method using ion plasma or the like.

When the above-described metal material is used for the first layer 3, the first layer 3 can be used also as an electric wiring layer that can handle a high-speed signal region.

As shown in FIG. 2, a desired electric wiring pattern 1 is formed separately from the groove forming etching mask pattern 8a.
By patterning the first layer 3 in the form of
An electric wiring insulated from the substrate 1 such as i can be formed.

Then, an optical waveguide is formed on the second layer 2 and the patterned first layer 3 (see FIG. 1B). This optical waveguide is formed by, for example, forming a cladding layer and an optical waveguide core layer of a silica-based glass containing P, Ge, B, or the like using a CVD method or a flame deposition method, and RIE dry etching. It is performed by combining the etching of the optical waveguide core layer by a method or the like.

As shown in FIG. 1B, the optical waveguide layer usually has a structure in which an optical waveguide core 4a on an optical waveguide lower cladding 4c is embedded with an optical waveguide upper cladding 4d.

The specific dimensions of the optical waveguide include, for example, a thickness of the lower cladding 4c of the optical waveguide of 10 to 20 μm, a cross section of the core of the optical waveguide core 4a of about 5 × 5 μm, and a thickness of the upper cladding layer 4d of the upper optical waveguide. Preferably, the thickness is about 10 μm.

The refractive index of the core (optical waveguide core 4a) is set slightly higher than the cladding (lower and upper cladding layers 4c and 4d) so that the relative refractive index difference Δn is, for example, about 5%. Thus, a single mode optical waveguide is obtained.

In the manufacturing method according to the present invention, the optical waveguide is not limited to a single mode, but may be a multi-mode optical waveguide. Further, the material of the optical waveguide is not limited to the quartz glass, but may be, for example, PMMA or fluorine polyimide.

Next, an optical waveguide end face forming mask 5 is formed on the optical waveguide layer 4 thus formed. The optical waveguide end face forming mask 5 is made of, for example, a metal such as Cr or Ti having a thickness of several tens to several hundreds of nm (several hundreds to several thousand angstroms), and a metal having a thickness of several μm to several tens μm. It is formed by laminating a photoresist and leaving it in a desired mask pattern shape by photolithography or the like. Further, the formation position of the mask 5 for forming the end face of the optical waveguide is so as to cover the upper part of the portion of the optical waveguide layer 4 to be left as shown in FIG. What should I do?

After that, the optical waveguide layer 4 and the second layer 2 are etched in a portion not covered with the optical waveguide end face forming mask 5. This etching is performed until the substrate surface 7 is exposed to form the end face 6 of the optical waveguide.
(D)).

In the case of the waveguide layer 4 made of quartz glass as an example, the above-mentioned etching is usually performed by, for example, a C _x F _y -based or C _x C _y -based reactive gas in order to reduce side etching. Is performed by dry etching using ions, radicals and neutral molecules. At this time, the first layer 3 (3a) formed in the shape of the pattern 8 of the groove forming etching mask on the substrate 1 is more etched than the optical waveguide layer 4 by dry etching using the reactive gas. Since it is made of a material having a sufficiently low rate (high selectivity), it is hardly etched and remains as a dry etching mask.

As a result, the lower second layer 2 is also
As shown in (D), the pattern is formed in the shape of a groove forming etching mask 8 of the substrate 1.

Since the patterned second layer 2a is preferably made of a quartz-based glass material containing SiO ₂ or the like as a main component, the substrate 2 made of Si or the like is etched with respect to the substrate etchant (for example, KOH solution). The etch rate is significantly lower than 1. This etch rate is applied to the second layer 2
Although it depends on the film formation method such as whether it is a Si thermal oxide film, a CVD deposited film or a sputtered film, and the impurity concentration in the film, for example, thermal oxide SiO ₂ is used for the second layer 2 and KOH is used for the etchant. when using the ratio of the etch rate is approximately Si: SiO ₂ = several hundred to 1000: is about 1.
Therefore, the patterned second layer 2 can be used as a mask for etching for forming a groove in the substrate 1.

In the dry etching, for example, reactive ion etching (RIE) having excellent verticality
Since the side etching is reduced by using the method, the groove forming etching mask 8 can be formed with high accuracy faithfully to the original pattern.

As a result, a groove forming etching mask 8 of the substrate 1 is formed in the groove forming portion 10 of FIG.
The substrate surface 7 is exposed at locations other than the mask.

It is also possible to use a method in which part of the dry etching step is replaced with wet etching.

That is, when etching a quartz glass optical waveguide, for example, first, as shown in FIG. 1F, by wet etching using buffered hydrofluoric acid (a mixed aqueous solution of ammonium fluoride and hydrogen fluoride) or the like. Next, the optical waveguide layer 4 is etched to a certain depth. In this case, “a certain depth” refers to the second layer 2
Refers to a depth that is not exposed. Specifically, an optical waveguide layer of about several tens nm (several hundred angstroms) to about 1 μm is usually left in consideration of variations in the thickness and etching rate of the optical waveguide layer. After this wet etching, dry etching is performed. As a result, the groove forming etching mask 8 of the substrate can be formed with high precision.

Then, the substrate 1 is etched by using the groove forming etching mask 8 to form the groove 9 in the substrate 1 (see FIG. 1E).

As an example of groove formation, when performing anisotropic etching of a Si substrate, KOH, NaO
H, CsOH aqueous solution, ethylenediamine / pyrocatechol mixed aqueous solution, hydrazine or the like may be used.

Finally, an optical fiber is mounted using the obtained groove 9 as a guide groove.

By adopting the above manufacturing method, the first
Even if a material originally having no durability against the etchant or a material losing the durability against the substrate etchant due to deterioration in the waveguide forming process on the first layer 3 is used as the layer 3 of the second layer, The groove forming etching mask 8 made of 2 can be formed with high accuracy and certainty without depending on the optical waveguide forming process method.

Also, by using a material such as a metal having excellent electrical characteristics such as high-frequency characteristics for the material of the first layer 3,
The feature of the embodiment of the present invention is that it has an advantage that an electric wiring insulated from the substrate 1 such as Si can be formed.

Actually, the WSi film of the first layer 3 is patterned in the form of a V-groove forming etching mask on the Si substrate on which the thermally oxidized SiO ₂ film of the second layer 2 is formed, and quartz is formed on this upper layer. A system glass optical waveguide 4 was formed.

Then, a desired portion of the optical waveguide layer 4 and the second layer 2 which is a V-groove forming portion is removed by buffered hydrofluoric acid and RIE dry etching. Patterning was performed with an accuracy of about sub-μm, which is equivalent to the accuracy.

Based on this, anisotropic etching of the Si substrate 1 was performed in a KOH aqueous solution to which isopropyl alcohol was added. The etching mask (2a) for V-groove formation using the thermally oxidized SiO ₂ film of the second layer 2 has almost no shape collapse due to immersion in the anisotropic etchant described above.
Functioned as a high-precision mask. As a result, a desired V groove was obtained with a yield of about 95% or more.

However, if left as is, the (111) surface 14 (see FIG. 1 (E) and FIG. 3) which is formed by anisotropic etching and which is the edge of the Si (111) surface and whose edge 6 is the edge of the optical waveguide portion. ) When the optical fiber end hits
The end of the optical fiber cannot be completely brought into contact with the end face 6 of the optical waveguide.

For this reason, as shown in FIG. 3, a cutting groove 15 deeper than the V-groove having a groove width of about 100 to 200 μm is provided between the V-groove forming portion 10a and the optical waveguide portion 13 by a dicing saw or the like. Then, the (111) surface 14 where the optical fiber end (not shown) collides obliquely was removed (the cross-sectional shape of the portion where 15a is removed is shown in the figure).

Thereafter, by mounting the optical fiber in the V-groove 9a, the silica glass optical waveguide and the optical fiber could be mounted without adjustment.

The present invention is not limited to the case where the guide groove for mounting the optical fiber is provided on the same substrate on which the optical waveguide is formed. For example, when a substrate for forming an optical fiber guide groove such as a V-groove is prepared separately from a substrate for forming an optical waveguide, and a groove for mounting guide pins for alignment between the substrates is provided on the substrate for forming the optical waveguide. The present invention can be similarly applied.

In the above embodiment of the present invention, the groove of the substrate has been described mainly on the assumption that a V groove is formed by anisotropic etching of a (100) Si substrate. Since it is sufficient that the Si substrate is obtained, the Si substrate used in the present invention includes:
For example, it may be a (110) substrate. When a (110) substrate is used, the groove shape is not V-shaped, but even in this case, the mask for groove formation etching is formed reliably and with high accuracy by the manufacturing method according to the present invention.

The material of the substrate is not limited to Si. By selecting an appropriate etchant, for example, the present invention can be applied to a case where a substrate such as an InP or GaAs crystal is used.

The embodiment of the present invention has been described above.
As described above, the present invention is not limited to this embodiment, but includes various forms and modifications according to the principle of the present invention.

[0061]

As described above, according to the present invention,
There is an effect that a guide groove for mounting an optical fiber or the like can be reliably and accurately formed on a substrate without depending on an optical waveguide forming process method. For this reason, since the optical fiber can be mounted on the substrate on which the optical waveguide is formed with high precision without any adjustment, a reduction in device manufacturing cost by mass production can be expected.

Further, in the present invention, by using a material such as a metal having good electrical characteristics such as high-frequency characteristics for the material of the first layer, the electric wiring insulated from the substrate such as Si can be formed on the same substrate. Since it can be formed by a manufacturing process, a further reduction in manufacturing cost by mass production can be expected.

[Brief description of the drawings]

FIG. 1 is a diagram for schematically explaining a method for manufacturing an optical device according to an embodiment of the present invention in the order of steps.

FIG. 2 is a view showing a state in which a pattern of a trench forming etching mask and an electric wiring pattern are collectively formed in a method for manufacturing an optical device according to an embodiment of the present invention.

FIG. 3 is a schematic view of the shape of an optical device after a cutting groove is provided between a V-groove forming portion and an optical waveguide portion, viewed from a direction perpendicular to the optical waveguide and parallel to a substrate surface, in one embodiment of the present invention. FIG.

FIG. 4 is a view for explaining an example of a method of manufacturing a groove forming etching mask according to a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Substrate 2 2nd layer made of the material which has the durability with respect to the groove forming etchant of the substrate 2a Patterned second layer 3 1st layer made of the material which has the durability with respect to dry etching 3a 1 layer 4 optical waveguide layer 4a optical waveguide core 4b optical waveguide clad 4c optical waveguide lower clad 4d optical waveguide upper clad 5 optical waveguide end face forming mask 6 optical waveguide end face 6a optical waveguide core end face 7 substrate surface 7a Si substrate surface 8 groove Forming etching mask 8a Groove forming etching mask pattern 9 Groove 9a V groove 10 Groove forming portion 10a V groove forming portion 11 Electrical wiring pattern 12 V groove forming etching mask 13 Optical waveguide portion 14 End face 6 of optical waveguide portion (111) surface to be the edge 15 Cutting groove 15a Portion to be removed

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-29638 (JP, A) JP-A-7-86693 (JP, A) JP-A-7-176717 (JP, A) 347665 (JP, A) JP-A-4-313710 (JP, A) JP-A-2-211406 (JP, A) JP-A-2-157805 (JP, A) JP-A-61-117513 (JP, A) US Patent 5,217,568 (US, A) European Patent Application Publication 682276 (EP, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6/12-6/14 G02B 6/30 G02B 6 / 42-6/43

Claims (9)

(57) [Claims] An optical waveguide circuit formed on a substrate;
So that the optical elements and optical fibers on the plate are optically coupled
In the method for manufacturing an optical device to be arranged, (a)On the substrate, the groove forming etchant of the substrate
Dry layer and second layer of durable material
A first layer of a material that is resistant to
FormingThe first layer is formed by etching a groove for etching a substrate.
(B) patterning in the shape ofAfter forming an optical waveguide above the first layer,
While forming the end face of the optical waveguide by ching,
Exposing the patterned first layer;  (c)The exposed patternedThe first layer is a mask
Etching, the second layer is etched into the groove of the substrate.
Patterning in the form of a etching mask; and (d) using the patterned second layer as a mask,
Step of forming the groove by etching the substrate
And a method for manufacturing an optical device. 2. The method according to claim 2, wherein said second layer is formed of thermally oxidized SiO ₂ or thermally nitrided.
2. The optical device according to claim 1 , wherein the nitrided Si ₃ N ₄ is used.
Vice manufacturing method. 3. The method according to claim 1, wherein said second layer has a thickness of 100 nm to 1 μm.
m.
Vice manufacturing method. 4. The method according to claim 1, wherein the second layer is used for forming a groove in a substrate.
The step of patterning in the form of a mask is performed by wet etching.
Performing in the order of the ching process and the dry etching process
The method for manufacturing an optical device according to claim 1, wherein: 5. The method according to claim 1, wherein the substrate is a (100) Si substrate,
The optical waveguide is made of quartz glass, and the second
Wherein the step of patterning the layer in the form of a mask for forming a groove on a substrate includes a dry etching step, wherein the groove provided in the substrate is formed by anisotropic etching of the substrate. 2. The method for manufacturing an optical device according to 1 . 6. The method according to claim 1, wherein the first layer is made of a conductive member.
A wiring pattern formed as wiring
The method for manufacturing an optical device according to claim 1 . 7. The method according to claim 1, wherein the first layer comprises Cr, Au, W, and W.
_{2. The} method for manufacturing an optical device according to claim 1, comprising at least one of xSi1 _-x (x = 0 to 1). 8. An optical waveguide circuit is formed on a substrate, and
So that the optical elements and optical fibers on the plate are optically coupled
In the mounting structure of an optical device to be arranged, the optical device is formed on the substrate and used for etching for forming a groove in the substrate.
Materials that are resistant to
A second layer having a thickness of 100 nm to 1 μm and a second layer formed on the second layer,
A first layer made of a material having high durability and an optical waveguide formed above the first layer , wherein the first layer and the second layer are formed on a groove of the substrate.
Pattern in the shape of an etching mask for
The substrate using the second layer formed as a mask as a mask
A groove formed by etching, the optical waveguide formed on the substrate,
Optical axis and position of the optical fiber mounted in the provided groove
Light characterized by being combined and optically coupled
Device mounting structure. 9. The method according to claim 1, wherein the second layer is made of an insulating layer,
Layer is made of a conductive member, and the first layer is
9. A pattern formed on a line.
The mounting structure of the described optical device.