U.S. patent application number 10/427762 was filed with the patent office on 2003-10-23 for method of manufacturing optical waveguide and method of manufacturing light transmitting/receiving apparatus.
Invention is credited to Ogawa, Tsuyoshi.
Application Number | 20030196746 10/427762 |
Document ID | / |
Family ID | 16400847 |
Filed Date | 2003-10-23 |
United States Patent
Application |
20030196746 |
Kind Code |
A1 |
Ogawa, Tsuyoshi |
October 23, 2003 |
Method of manufacturing optical waveguide and method of
manufacturing light transmitting/receiving apparatus
Abstract
Disclosed is a method of manufacturing an optical waveguide,
capable of easily manufacturing an optical waveguide which can hold
an excellent light propagating characteristic irrespective of the
kind of a supporting substrate. On a transparent substrate, a
peelability promoting film obtained by setting silicone oil and an
optical waveguide made of an epoxy resin are sequentially formed.
The peelability promoting film promotes the peelability between the
transparent substrate and the optical waveguide with sufficient
adhesion that it is not peeled off from the transparent substrate
during formation of the optical waveguide. Subsequently, after
adhering a multilayer wiring board to the optical waveguide via an
adhering layer made of a photosetting resin, the adhering layer is
irradiated with light so as to be set, thereby fixing the
multilayer wiring board to the optical waveguide. When a tensile
stress is mechanically applied to the transparent substrate, the
transparent substrate is easily peeled off from the optical
waveguide together with the peelability promoting film, and the
optical waveguide is transferred onto the multilayer wiring
board.
Inventors: |
Ogawa, Tsuyoshi; (Kanagawa,
JP) |
Correspondence
Address: |
Robert J. Depke
Holland & Knight LLC
30th Floor
131 South Dearborn Street
Chicago
IL
60603-5506
US
|
Family ID: |
16400847 |
Appl. No.: |
10/427762 |
Filed: |
April 30, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10427762 |
Apr 30, 2003 |
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09615833 |
Jul 13, 2000 |
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6579398 |
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Current U.S.
Class: |
156/230 ;
156/247 |
Current CPC
Class: |
Y10T 428/2804 20150115;
Y10T 428/149 20150115; G02B 6/42 20130101; Y10T 428/1414 20150115;
G02B 6/43 20130101; G02B 6/4214 20130101; Y10S 428/914 20130101;
Y10T 428/1476 20150115; G02B 2006/12104 20130101; G02B 6/138
20130101; Y10T 428/24868 20150115 |
Class at
Publication: |
156/230 ;
156/247 |
International
Class: |
B32B 031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 13, 1999 |
JP |
P11-199023 |
Claims
What is claimed is:
1. A method of manufacturing an optical waveguide by forming an
optical waveguide on a first substrate side and then transferring
the optical waveguide on the first substrate side to a second
substrate side, comprising: a step of forming a peelability
promoting film for promoting peelability between the first
substrate and a layer to be formed on the first substrate; a step
of forming at least an optical waveguide on the peelability
promoting film; a step of fixing the optical waveguide supported by
the first substrate and the second substrate to each other; and a
step of peeling the first substrate off the optical waveguide.
2. The method of manufacturing the optical waveguide according to
claim 1, wherein in the step of peeling the first substrate off the
optical waveguide, the first substrate is peeled off by applying a
physical force to the first substrate.
3. The method of manufacturing the optical waveguide according to
claim 2, wherein the peelability promoting film is formed by using
siloxane.
4. The method of manufacturing the optical waveguide according to
claim 3, wherein the step of forming the peelability promoting film
comprises: a step of applying silicone in a liquid state; and a
step of setting the silicone by performing a heat treatment.
5. The method of manufacturing the optical waveguide according to
claim 1, wherein the peelability promoting film is made of a
material having a glass transition temperature at least lower than
that of the material of the optical waveguide and, in a step of
peeling the first substrate off the optical waveguide, the first
substrate is peeled off by performing a heat treatment at a
temperature higher than the glass transition temperature of the
material of the peeling promoting film.
6. The method of manufacturing the optical waveguide according to
claim 5, wherein the peelability promoting film is formed by using
an acrylic resin.
7. The method of manufacturing the optical waveguide according to
claim 5, wherein the heat treatment is performed at a temperature
lower than the glass transition temperature of the material of the
optical waveguide.
8. The method of manufacturing the optical waveguide according to
claim 1, wherein the step of fixing the optical waveguide and the
second substrate to each other is performed by using an
adhesive.
9. The method of manufacturing the optical waveguide according to
claim 8, wherein a light transmitting material is used as the
material of each of the first substrate and the peelability
promoting film, a photosetting material is used as the material of
the adhesive, and the step of fixing the optical waveguide and the
second substrate to each other comprises: a step of adhering the
optical waveguide and the second substrate to each other via the
adhesive; and a step of setting the adhesive by irradiating the
adhesive with light through the first substrate toward the second
substrate.
10. The method of manufacturing the optical waveguide according to
claim 8, wherein a thermosetting material is used as the material
of the adhesive.
11. The method of manufacturing the optical waveguide according to
claim 1, wherein in the step of forming at least an optical
waveguide on the peelability promoting film, a plurality of optical
waveguides which are separated from each other are formed.
12. The method of manufacturing the optical waveguide according to
claim 11, wherein the step of forming at least an optical waveguide
on the peelability promoting film includes: a step of forming an
organic material layer made of a photosetting organic material on
the peelability promoting film; a step of irradiating the organic
material layer with light and selectively exposing and setting some
regions of the organic material layer, the regions on which the
plurality of optical waveguides are to be formed; and a step of
removing unset portions in the organic material layer, thereby
forming the plurality of optical waveguides.
13. The method of manufacturing the optical waveguide according to
claim 11, wherein the step of forming at least an optical waveguide
on the peelability promoting film includes: a step of forming an
optical waveguide precursor layer on the peelability promoting film
by using the material of the optical waveguide; and a step of
selectively etching and separating the optical waveguide precursor
layer into a plurality of optical waveguides.
14. The method of manufacturing the optical waveguide according to
claim 11, wherein the step of fixing the plurality of optical
waveguides and the second substrate to each other comprises: a step
of applying an adhesive made of a photosetting material or a
thermosetting material only on the surface opposite to the first
substrate of each of the optical waveguides; a step of adhering the
optical waveguides and the second substrate to each other via the
adhesive; and a step of setting the adhesive.
15. The method of manufacturing the optical waveguide according to
claim 1, wherein the optical waveguide is made of a material
containing at least one material selected from the group consisting
of polyimide, epoxy resin, acrylic resin, polyolefine resin, and
synthetic rubber.
16. The method of manufacturing the optical waveguide according to
claim 1, wherein a substrate made of quartz or glass is used as the
first substrate.
17. The method of manufacturing the optical waveguide according to
claim 1, wherein a wiring board on which electric wiring is formed
is used as the second substrate.
18. The method of manufacturing the optical waveguide according to
claim 1, wherein a multilayer substrate containing at least one
ceramic material selected from the group consisting of aluminum
oxide (Al2O3), glass ceramic, aluminum nitride (AlN) and mullite is
used as the second substrate.
19. The method of manufacturing the optical waveguide according to
claim 1, wherein a multilayer substrate containing at least one an
organic material selected from the group consisting of a glass
epoxy resin, polyimide, a BT (bismaleimide triazine) resin, a PPE
(polyphenyl ether) resin, a phenol resin and a polyolefine resin is
used as the second substrate.
20. A method of manufacturing an optical transmitting/receiving
apparatus having an optical waveguide by forming the optical
waveguide on a first substrate side and transferring the optical
waveguide from the first substrate side to a second substrate side,
comprising: a step of forming a peelability promoting film for
promoting peelability between the first substrate and a layer to be
formed on the first substrate; a step of forming at least an
optical waveguide on the peelability promoting film; a step of
fixing the optical waveguide supported by the first substrate and
the second substrate to each other; a step of peeling the first
substrate off the optical waveguide; a step of forming at least one
of a light emitting device for converting an electric signal into a
light signal and a photodetecting device for converting a light
signal into an electric signal on the second substrate; and a step
of forming an integrated circuit for transferring/receiving an
electric signal to/from at least one of the light emitting device
and the photodetecting device on the second substrate.
21. The method of manufacturing the optical transmitting/receiving
apparatus according to claim 20, wherein a wiring board on which
electric wiring is formed is used as the second substrate.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method of fabricating an
optical waveguide through which a light signal propagates and a
method of manufacturing an optical transmitting/receiving apparatus
having such an optical waveguide.
[0003] 2. Description of the Related Art
[0004] As the technology in an IC (Integrated Circuit) and an LSI
(Large Scale Integrated) circuit progresses, their operating speed
and scale of integration are improving and, for example, the higher
performance of a microprocessor and the larger capacity of a memory
chip are rapidly being achieved. Hitherto, transmission of
information in relatively short distance, for example, between
boards in a device or between chips on a board is carried out
mainly via an electric signal. In order to further improve the
performance of an integrated circuit in the future, it is necessary
to increase the transmission rate of a signal and the density of
signal wiring. In the electric signal wiring, however, it is
difficult to increase the transmission rate of a signal and the
density of signal wiring, and a problem of a signal delay by a time
constant of CR (C: capacitance of wiring and R: resistance of
wiring) of wires arises. Since an increase in transmission rate of
the electric signal and an increase in density of the electric
signal wiring cause EMI (Electromagnetic Interference) noises, it
is indispensable to take countermeasures against the problems.
[0005] Optical wiring (optical interconnection) attracts a
considerable attention as a means for solving the problems. The
optical wiring is considered to be applicable to various situations
such as the connection between devices, between boards in a device,
or between chips on a board. Among them, for transmission of
signals over relatively short distances such as transmission
between chips, it is considered to be suitable to build a light
transmission communication system. In the system, an optical
waveguide is formed on a substrate on which chips are mounted and
is used as a transmission line. In order to spread the light
transmission communication system using the optical waveguide as a
transmission line, it is important to establish a process of
forming the optical waveguide.
[0006] As a known conventional method of fabricating an optical
waveguide, a method of forming an optical waveguide made of quartz
or a high polymer material such as PMMA (Polymethyl Methacrylate)
or polyimide on a flat substrate such as a silicon substrate or
glass substrate is known. Since the optical waveguide is formed on
a flat substrate in the method, the optical waveguide with a slight
loss in light propagation can be easily formed.
[0007] In the optical transmission communication system using the
optical waveguide as a transmission line, however, a light emitting
device for converting an electric signal into a light signal, a
photodetecting device for converting a light signal into an
electric signal, an IC chip for transmitting an electric signal
between the light emitting device and the photodetecting device,
and the like have to be provided. Supply of power to the devices
and transfer of various control signals of relatively low speed
have to be performed by electric signals as ever.
[0008] It is therefore indispensable to provide thin film
multilayer wiring as electric signal wiring on a substrate.
However, increasing the area in which the electric signal wires are
formed to a normal wiring substrate size (tens cm per side) or a
module size (a few cm per side) costs too much, and is difficult to
be put into practice, thereby causing a problem.
[0009] In order to solve the problem, it can be considered to form
an optical waveguide on a printed wiring board on which electrical
parts can be mounted. On the surface of such a wiring board
manufactured by thick film process, however, a metal thick film
formed by plating or the like is provided and the surface is
considerably uneven. When an optical waveguide is formed on the
printed wiring board, consequently, the shape of the optical
waveguide is influenced by the surface-unevenness of the board. It
causes a problem such that a light propagation loss in the optical
waveguide increases and the dimension accuracy deteriorates.
[0010] Further, in the case of forming the optical waveguide on the
wiring board, in wet etching, cleaning and the like, a process of
immersing the whole board in an acid or alkali solution, an organic
solvent, or the like is necessary. Consequently, there is a problem
such that the board may be damaged. There is also the possibility
that the board is damaged in the event of dry etching and heat
treatment at high temperature. It is therefore difficult to use an
electric wiring board formed by a thick film process such as a
printed wiring board as a board. An expensive board having
characteristics such as high heat resistance has to be used.
SUMMARY OF THE INVENTION
[0011] The present invention has been achieved in consideration of
the problems and its object is to provide a method of easily
forming an optical waveguide capable of holding an excellent light
propagating characteristic irrespective of the kind of a supporting
board.
[0012] According to the invention, there is provided a method of
manufacturing an optical waveguide by forming an optical waveguide
on a first substrate side and then transferring the optical
waveguide on the first substrate side to a second substrate side,
comprising: a step of forming a peelability promoting film for
promoting peelability between the first substrate and a layer to be
formed on the first substrate; a step of forming at least an
optical waveguide on the peelability promoting film; a step of
fixing the optical waveguide supported by the first substrate and
the second substrate to each other; and a step of peeling the first
substrate off the optical waveguide.
[0013] According to the invention, there is also provided a method
of manufacturing an optical transmitting/receiving apparatus having
an optical waveguide by forming the optical waveguide on a first
substrate side and transferring the optical waveguide from the
first substrate side to a second substrate side, comprising: a step
of forming a peelability promoting film for promoting peelability
between the first substrate and a layer to be formed on the first
substrate; a step of forming at least an optical waveguide on the
peelability promoting film; a step of fixing the optical waveguide
supported by the first substrate and the second substrate to each
other; a step of peeling the first substrate off from the optical
waveguide; a step of forming at least one of a light emitting
device for converting an electric signal into a light signal and a
photodetecting device for converting a light signal into an
electric signal on the second substrate; and a step of forming an
integrated circuit for transferring/receiving an electric signal
to/from at least one of the light emitting device and the
photodetecting device on the second substrate.
[0014] In the method of manufacturing the optical waveguide and the
method of manufacturing the optical transmitting/receiving
apparatus according to the invention, the peelability promoting
film and the optical waveguide are sequentially formed on the first
substrate. After that, the optical waveguide and the second
substrate are fixed to each other. By peeling the first substrate
off the optical waveguide by using the peelability promoting film,
the optical waveguide is transferred from the first substrate to
the second substrate.
[0015] Other and further objects, features and advantages of the
invention will appear more fully from the following
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIGS. 1A and 1B are cross sections for explaining a process
in a method of manufacturing an optical transmitting/receiving
apparatus according to a first embodiment of the invention.
[0017] FIGS. 2A and 2B are cross sections for explaining a
manufacturing process subsequent to FIGS. 1A and 1B.
[0018] FIGS. 3A and 3B are cross sections for explaining a
manufacturing process subsequent to FIGS. 2A and 2B.
[0019] FIGS. 4A and 4B are cross sections for explaining a
manufacturing process subsequent to FIGS. 3A and 3B.
[0020] FIGS. 5A and 5B are cross sections for explaining a
manufacturing process subsequent to FIGS. 4A and 4B.
[0021] FIGS. 6A and 6B are cross sections for explaining a
manufacturing process subsequent to FIGS. 5A and 5B.
[0022] FIG. 7 is a cross section for explaining a manufacturing
process subsequent to FIGS. 6A and 6B.
[0023] FIGS. 8A and 8B are cross sections for explaining a process
in a method of manufacturing an optical transmitting/receiving
apparatus according to a second embodiment of the invention.
[0024] FIGS. 9A and 9B are cross sections for explaining a
manufacturing process subsequent to FIGS. 8A and 8B.
[0025] FIGS. 10A and 10B are cross sections for explaining a
manufacturing process subsequent to FIGS. 9A and 9B.
[0026] FIGS. 11A and 11B are cross sections for explaining a
manufacturing process subsequent to FIGS. 10A and 10B.
[0027] FIGS. 12A and 12B are cross sections for explaining a
manufacturing process subsequent to FIGS. 11A and 11B.
[0028] FIGS. 13A and 13B are cross sections for explaining a
manufacturing process subsequent to FIGS. 12A and 12B.
[0029] FIGS. 14A and 14B are cross sections for explaining a
process in a method of manufacturing an optical
transmitting/receiving apparatus according to a third embodiment of
the invention.
[0030] FIGS. 15A and 15B are cross sections for explaining a
manufacturing process subsequent to FIGS. 14A and 14B.
[0031] FIGS. 16A and 16B are cross sections for explaining a
process in a method of manufacturing an optical
transmitting/receiving apparatus according to a fourth embodiment
of the invention.
[0032] FIGS. 17A and 17B are cross sections for explaining a
manufacturing process subsequent to FIGS. 16A and 16B.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] Embodiments of the invention will be described in detail
hereinbelow by referring to the drawings.
[0034] (First Embodiment)
[0035] Referring now to FIGS. 1A and 1B to FIG. 7, a method of
manufacturing an optical transmitting/receiving apparatus according
to a first embodiment of the invention will be described. Since a
method of fabricating an optical waveguide according to the
embodiment is embodied by the method of manufacturing the optical
transmitting/receiving apparatus according to the embodiment, it
will be also described hereinbelow. Each of FIGS. 1A and 1B to FIG.
7 shows a manufacturing process in the method of manufacturing the
optical transmitting/receiving apparatus. FIGS. 1A to 6A are cross
sections perpendicular to the longitudinal direction of the optical
waveguide. FIGS. 1B to 6B are cross sections parallel to the
longitudinal direction of the optical waveguide. Each of FIGS. 1A
to 6A is a cross section taken along line nA-nA (n denotes Roman
numerals corresponding to each of FIGS. 1B to 6B). FIG. 7 is a
cross section parallel to the longitudinal direction of the optical
waveguide.
[0036] In the embodiment, first, as shown in FIGS. 1A and 1B, a
very flat transparent substrate 11 made of a material such as
quartz or glass which sufficiently transmits light from the
ultraviolet region to the visible region is prepared. The
transparent substrate 11 corresponds to an example of "first
substrate" of the invention. On the transparent substrate 11, for
example, liquid silicone (such as silicone oil) as a kind of
siloxane is applied by spin coating and is subjected to a heat
treatment at 150.degree. C. for 30 minutes to 1 hour so as to be
set, thereby forming a peelability promoting film 12. The
peelability promoting film 12 is used to promote the peelability
between the transparent substrate 11 and an optical waveguide 16
(refer to FIG. 3) which will be described hereinlater. While the
optical waveguide is formed on the transparent substrate 11, the
peelability promoting film 12 has the minimum adhesion of a degree
at which the optical waveguide is not peeled off partially or
totally from the transparent substrate 11.
[0037] On the peelability promoting film 12, an epoxy resin
containing bisphenol as a main component is applied so as to be
about 20 .mu.m thick by spin coating. After that, a heat treatment
is performed to set the resin, thereby forming a cladding layer 13
of the optical waveguide having a refractive index of, for example,
1.52. Subsequently, on the cladding layer 13, a core layer 14A of
the optical waveguide having a refractive index of, for example,
1.54 and a thickness of about 30 .mu.m is formed by using a
material (such as epoxy resin) whose refractive index is higher
than that of the material of the cladding layer 13 in a manner
similar to the method of forming the cladding layer 13.
[0038] Subsequently, a photoresist film (not shown) having a
pattern, for example, in a strip shape in plan view is formed and
anisotropic dry etching such as RIE (Reactive Ion Etching) is
performed by using the photoresist film as a mask. By the etching,
as shown in FIG. 2A, a plurality of cores 14 which are apart from
each other and each of which has a strip shape in plan view are
obtained from the core layer 14A.
[0039] As shown in FIGS. 3A and 3B, for example, on the entire
surface of the transparent substrate 11, a cladding layer 15 having
a thickness of about 20 .mu.m is formed on the cores 14 by using
the same material as that of the cladding layer 13 in a manner
similar to the method of forming the cladding layer 13. In such a
manner, the buried optical waveguide 16 comprising the cladding
layers 13 and 15 and the cores 14 is formed.
[0040] Each of the cladding layers 13 and 15 and the cores 14 may
be formed by applying a photosetting resin on the underlayer and
irradiating the photosetting resin with light to set the resin.
[0041] As shown in FIGS. 4A and 4B, for example, light reflecting
portions 16A and 16B each constructed by an inclined face are
formed at both ends in the longitudinal direction of the optical
waveguide 16. The exterior angle formed between each of the
reflecting portions 16A and 16B with the transparent substrate 11
is an obtuse angle (in this case, about 135.degree.). The exterior
angle formed between the optical waveguide 16 and the transparent
substrate 11 denotes the exterior angle of a figure when the cross
section along the light propagating direction of the optical
waveguide 16 is regarded as a closed figure. An example of the
method of forming the light reflecting portions 16A and 16B will be
described specifically. First, a photoresist film (not shown) is
formed on the cladding layer 15 and is subjected to predetermined
exposing and developing processes, thereby processing the
photoresist film in a predetermined pattern. The patterned
photoresist film is heated, for example, at the glass transition
temperature or higher to thereby incline the edge portions of the
photoresist film. Subsequently, by using the photoresist film
having inclined edges as a mask, anisotropic etching is performed
on the optical waveguide 16 by an RIE system or ECR (Electro
Cyclotron Resonance) system to thereby form the light reflecting
portions 16A and 16B. After that, the photoresist film is
removed.
[0042] As shown in FIGS. 5A and 5B, an arbitrary board such as a
multilayer wiring board 17 having an electric wire 17A and an
insulator 17B is prepared. In desired areas on the multilayer
wiring board 17, an adhering layer 18 having a thickness of about
10 .mu.m made of an adhesive containing a photosetting material
such as epoxy resin is formed by a method such as spin coating, dip
coating, spraying or printing. The adhering layer 18 plays not only
the role of adhering the optical waveguide 16 and the multilayer
wiring board 17 and but also the role of planarizing the rough
surface of the multilayer wiring board 17. The multilayer wiring
board 17 corresponds to an example of "second substrate" of the
invention.
[0043] As the multilayer wiring board 17, for example, a ceramic
multilayer wiring board in which the insulator 17B is made of an
inorganic material such as alumina (Al.sub.2O.sub.3),
low-temperature sintering glass ceramic, glass ceramic, aluminium
nitride (AlN), or mullite is used. As the multilayer wiring board
17, the following may be also used; a glass epoxy multilayer wiring
board in which the insulator 17Bis made of a glass epoxy resin such
as FR-4; what is called a built-up multilayer wiring board in which
a high density pattern can be formed by a photolithography
technique using a photosensitive epoxy resin or the like on a
regular glass epoxy interconnection board; a flexible multilayer
wiring board using a polyimide film or the like as the insulator
17B; and a multilayer wiring board using an organic material such
as BT (bismaleimide triazine) resin, PPE (polyphenyl ether) resin,
phenol resin, or polyolefine resin (Teflon made by DuPont).
Besides, what is called a printed wiring board obtained by
disposing a printed board on which an electric wiring pattern is
printed at high density onto a core substrate made of a dielectric
material or the like can be also used.
[0044] Then the transparent substrate 11 on which the optical
waveguide 16 is formed is turned upside down. The multilayer wiring
board 17 on which the adhering layer 18 is formed is adhered to the
optical waveguide 16 while they are aligned. Since both the
transparent substrate 11 and the optical waveguide 16 are
transparent, they are easily aligned to the multilayer wiring board
17. Subsequently, in a state where the optical waveguide 16 on the
transparent substrate 11 side and the multilayer wiring board 17
are adhered to each other, the transparent substrate 11 is
irradiated with light L and the light L travels toward the
multilayer wiring board 17 side. By the irradiation, the
photosetting resin as the adhesive constructing the adhering layer
18 is set and the multilayer wiring board 17 is fixed in a desired
position in the optical waveguide 16. At this time, when the light
L of a large quantity is applied for short time, a distortion
occurs in the optical waveguide 16 and a light propagation loss
increases. The light L of a relatively small quantity is therefore
applied for long time. For example, in the case of using a mercury
lamp of very high pressure (wavelength; center of G string (436
nm)), light is emitted with an output of 10 mW/cm.sup.2 for three
minutes. After that, by heating the adhering layer 18 as necessary,
a thermosetting process is performed on the adhesive.
[0045] The epoxy resin used in the embodiment is a light
transmitting resin that transmits about 90% of light in the near
ultraviolet and visible regions. As already described above, the
transparent substrate 11 is sufficiently transparent in the range
from the ultraviolet region to the visible region. For example, the
light L emitted from the mercury lamp of very high pressure
therefore transmits the transparent substrate 11 and the optical
waveguide 16 and sufficiently reaches the adhering layer 18.
Consequently, the adhering layer 18 made of an epoxy region or the
like is completely set. Preferably, the adhesion between the
optical waveguide 16 and the multilayer wiring board 17 is stronger
than that between the optical waveguide 16 and the transparent
substrate 11, which is lowered by the peelability promoting film
12.
[0046] As shown in FIGS. 6A and 6B, a physical force F such as
tensile stress is applied to the transparent substrate 11 to
separate the transparent substrate 11 from the optical waveguide
16. By the operation, the optical waveguide 16 is transferred to
the multilayer wiring board 17. In this case, the peelability
between the transparent substrate 11 and the optical waveguide 16
has been promoted by the peelability promoting film 12 provided
between the transparent substrate 11 and the optical waveguide 16.
The transparent substrate 11 is therefore easily peeled off
together with the peelability promoting film 12 from the optical
waveguide 16. A part or the whole of the peelability promoting film
12 may remain on the optical waveguide 16.
[0047] As shown in FIG. 7, a semiconductor laser 21, a photo diode
22, and IC chips 23 and 24 are mounted on the multilayer wiring
board 17 by, for example, flip-chip bonding. Besides the
semiconductor laser 21, photodiode 22 and IC chips 23 and 24, other
devices such as a chip resistor, a capacitor and an inductor can be
mounted. The semiconductor laser 21 corresponds to an example of
"light emitting device" of the invention. The photodiode 22
corresponds to an example of "photodetecting device" of the
invention. Each of the IC chips 23 and 24 corresponds to an example
of "integrated circuit" of the invention.
[0048] Finally, although not shown, the semiconductor laser 21,
photodiode 22 and IC chips 23 and 24 that are mounted and the
multilayer wiring board 17 are sealed by a sealing resin such as an
epoxy resin. It improves the connecting reliability between the
semiconductor laser 21, photodiode 22 and IC chips 23 and 24 and
the electric wiring 17A of the multilayer wiring board 17.
[0049] In the optical transmitting/receiving apparatus manufactured
in such a manner, the semiconductor laser 21, photodiode 22 and IC
chips 23 and 24 are made operative by the power supplied from the
electric wiring 17A of the multilayer wiring board 18. In such a
state, when an electric signal is outputted from the IC chip 23 to
the semiconductor laser 21, the semiconductor laser 21 converts the
electric signal into a light signal and outputs the light signal.
The outputted light signal is totally reflected by the light
reflecting portion 16A in the direction almost orthogonal to the
incident direction and enters the optical waveguide 16. After that,
the light signal propagates through the core 14 and reaches the
light reflecting portion 16B. The light signal is totally reflected
by the light reflecting portion 16B, for example, in the direction
almost orthogonal to the light propagating direction, goes out from
the optical waveguide 16 and enters the photodiode 22. The light
signal incident on the photodiode 22 is converted into an electric
signal and the electric signal is supplied to the IC chip 24. In
such a manner, the signal to be transferred at high speed between
the IC chips 23 and 24 is transferred at high speed as a light
signal. A signal that can be transmitted at relatively low speed
such as a low-speed control signal is transmitted as an electric
signal via the electric wire 17A of the multilayer wiring board
17.
[0050] According to the method of manufacturing the optical
transmitting/receiving apparatus according to the embodiment, after
preliminarily forming the optical waveguide 16 on the very flat
transparent substrate 11, the optical waveguide 16 is transferred
onto the multilayer wiring board 17. Consequently, even in the case
of using the multilayer wiring board 17 having the rough surface as
a supporting substrate, an optical transmitting/receiving apparatus
having the optical waveguide 16 in which the light propagation loss
is small can be manufactured. Since the peelability promoting film
12 is provided between the transparent substrate 11 for forming an
optical waveguide and the optical waveguide 16, the peelability
between the transparent substrate 11 and the optical waveguide 16
is promoted. The transparent substrate 11 can be therefore easily
peeled from the optical waveguide 16.
[0051] (Second Embodiment)
[0052] A second embodiment relates to a method of manufacturing an
optical transmitting/receiving apparatus. The optical
transmitting/receiving apparatus as the object is similar to that
of the first embodiment except that optical waveguides are
separated from each other. Referring to FIGS. 8A and 8B to FIGS.
13A and 13B, the method of manufacturing the optical
transmitting/receiving apparatus of the embodiment will be
described. FIGS. 8A to 13A are cross sections orthogonal to the
longitudinal direction of the optical waveguide. FIGS. 8B to 13B
are cross sections parallel to the longitudinal direction of the
optical waveguide. Each of FIGS. 8A to 13A is a cross section taken
along line nA-nA (n denotes Roman numerals corresponding to each of
FIGS. 8B to 13B, respectively). The same components as those of the
first embodiment are designated by the same reference numerals and
their detailed description is omitted here.
[0053] In the embodiment, first, as shown in FIGS. 8A and 8B, the
peelability promoting film 12 made of silicone oil or the like is
formed on the transparent substrate 11. On the peelability
promoting film 12, a photosetting epoxy resin layer containing
bisphenol as a main component is formed so as to be about 20 .mu.m
thick by, for example, spin coating. By using a mask having a
predetermined aperture pattern and a mercury lamp of very high
pressure, the epoxy resin layer is irradiated with light with an
output of 10 mW/cm.sup.2 for three minutes. The exposed part in the
epoxy resin layer is thereby set and becomes a cladding layer 33 of
the optical waveguide, which has a refractive index of, for
example, 1.52. The other part remains unset. Subsequently, the
unset part of the epoxy resin layer is selectively dissolved and
removed by acetone or ethanol. In such a manner, a plurality of
cladding layers 33 which are apart from each other are formed. The
epoxy resin layer corresponds to an example of "organic material
layer" of the invention.
[0054] As shown in FIG. 9, a core 34 is selectively formed on each
of the cladding layers 33. Specifically, for example, an epoxy
resin layer containing bisphenol as a main component is formed on
the whole surface of the transparent substrate 11 so as to be about
30 .mu.m thick by spin coating. After that, by using a mask having
a predetermined aperture pattern and, for example, a mercury lamp
of very high pressure as a light source, the epoxy resin layer is
selectively irradiated with light at an output of 10 mW/cm.sup.2
for three minutes. The exposed portions in the epoxy resin layer
are set and become the cores 34 of the optical waveguide, of which
refractive index is, for example, 1.54. The other portion remains
unset. Subsequently, the unset portion in the epoxy resin layer is
selectively dissolved and removed by, for example, acetone or
ethanol. After that, light reflecting portions 34A and 34B are
formed as inclined surfaces at both ends in the longitudinal
direction of each of the cores 34 in a manner similar to the method
of creating the light reflecting portions 16A and 16B. The exterior
angle formed between the transparent substrate 11 and each of the
light reflecting portions 34A and 34B is an obtuse angle (in this
case, about 135.degree.). The epoxy resin layer for forming the
core 34 also corresponds to an example of "organic material layer"
of the invention.
[0055] As shown in FIGS. 10A and 10B, a cladding layer 35 having a
refractive index of, for example, 1.54 is formed by using a
material similar to that of the cladding layer 33 in a manner
similar to the method of forming the cladding layer 33 so as to
cover the whole area except for the light reflecting portions 34A
and 34B of the core 34, thereby forming a plurality of optical
waveguides 36 which are apart from each other. Each of the optical
waveguides 36 is constructed by the core 34 and the cladding layers
33 and 35. In the optical waveguide 36, the light reflecting
portions 34A and 34B are in contact with air having a refractive
index of 1.00, so that the critical angle of the total reflection
can be made small and a light loss in the light reflecting portions
34A and 34B can be also made small.
[0056] As shown in FIGS. 11A and 11B, a very flat substrate 41 to
which an adhesive is to be applied is prepared. A liquid
photosetting adhesive 42 such as an epoxy resin is applied on, for
example, the whole surface of the substrate 41. After that, the
transparent substrate 11 on which the optical waveguide 36 is
formed is turned upside down so that the surface of the cladding
layer 35 comes into contact with the adhesive 42, thereby adhering
the cladding layer 35 to the adhesive 42. In a state where the
adhesive 42 is adhered to the cladding layer 35, as shown in FIGS.
12A and 12B, the multilayer wiring board 17 and the optical
waveguide 36 are adhered to each other via the adhesive 42 and the
transparent substrate 11 is irradiated with parallel light Lp which
travels toward the multilayer wiring board 17. When the accumulated
light quantity of the irradiated parallel light Lp reaches, for
example, few thousands mJ/cm.sup.2, the adhesive 42 is set and the
multilayer wiring board 17 is fixed to the optical waveguide
36.
[0057] In the case of using the adhesive 42 in a liquid state, when
the viscosity is low, it is feared that the adhesive 42 is adhered
also to side faces of the optical waveguide 36. In order to avoid
the unnecessary adhesion, the adhesive 42 in the form of a gel or
solid film sheet can be used. Such an adhesive generally has a
thermosetting property. Consequently, the cladding layer 35 and the
adhesive are once attached to each other and are subjected to a
heat treatment (temporary curing), for example, at 80.degree. C.
for a few seconds, thereby adhering the adhesive 42 to the cladding
layer 35. After that, the multilayer wiring board 17 and the
optical waveguide 36 are closely attached to each other via the
adhesive and are subjected to a heat treatment (curing in full
gear), for example, at 150.degree.C. for 30 to 60 minutes, thereby
fixing the multilayer wiring board 17 to the optical waveguide 36.
In the case of using the thermosetting adhesive, the alignment to
the multilayer wiring board 17 can be carried out by using infrared
rays. Consequently, in place of the transparent substrate 11, a
substrate made of silicon or the like can be also used.
[0058] After fixing the multilayer wiring board 17 to the optical
waveguide 36, as shown in FIGS. 13A and 13B, a physical force F
such as tensile stress is applied onto the transparent substrate 11
to separate the transparent substrate 11 from the optical waveguide
36. By the operation, the optical waveguide 36 is transferred to
the multilayer wiring board 17. Although there is a case such that
the peelability promoting film 12 partially or entirely remains on
the optical waveguide 36 side, in such a case as well, the
transparent substrate 11 is easily peeled off from the optical
waveguide 36. Preferably, the peelability promoting film 12 is not
left between the optical waveguides 36 since the remains become an
obstacle in the event of disposing a light emitting device, a
photodetecting device and the like later.
[0059] After that, although not shown, in a manner similar to the
first embodiment, the semiconductor laser, photodiode, IC chip and
the like are mounted on the multilayer wiring board 17 by, for
example, flip-chip bonding. Further, by using a resin for sealing,
the semiconductor laser, photodiode, IC chips and the like are
sealed.
[0060] As described above, according to the method of manufacturing
the optical transmitting/receiving apparatus of the embodiment, the
optical waveguides 36 which are separated from each other are
formed via the peelability promoting film 12 on the very flat
transparent substrate 11 and then transferred to the multilayer
wiring board 17. Consequently, the plurality of optical waveguides
36 on the transparent substrate 11 can be excellently and easily
transferred onto the multilayer wiring board 17.
[0061] Although the case of forming the plurality of optical
waveguides 36 each having a strip shape in plan view has been
described above, by using the manufacturing method of the
embodiment, optical waveguides 36 each having an arbitrary shape in
plan view (such as L shape, U shape, or circular shape) formed on
the transparent substrate 11 can be transferred onto the multilayer
wiring board 17. For example, the optical waveguide is not
transferred to a region where the optical waveguide is not desired
to be transferred such as an electrode forming area in the
multilayer wiring board 17 but can be transferred to only desired
regions.
[0062] (Third Embodiment)
[0063] Referring now to FIGS. 14A and 14B, FIGS. 15A and 15B and
the figures referred in the first embodiment, a method of
manufacturing an optical transmitting/receiving apparatus according
to a third embodiment of the invention will be described. The
optical transmitting/receiving apparatus as the object is similar
to that in the first embodiment. FIGS. 14A and 15A are cross
section orthogonal to the longitudinal direction of the optical
waveguide and FIGS. 14B and 15B are cross sections parallel to the
longitudinal direction of the optical waveguide. FIGS. 14A and 15A
are cross sections taken along lines XIVA-XIVA and XVA-XVA of FIGS.
14B and 15B, respectively. The same components as those of the
first embodiment are designated by the same reference numerals and
their description is omitted here.
[0064] First, as shown in FIGS. 14A and 14B, a photosetting acrylic
resin is applied on the transparent substrate 11 by, for example,
spin coating. The acrylic resin is irradiated with ultraviolet rays
of a light quantity of 2000 mJ/cm.sup.2 so as to be set, thereby
forming a peelability promoting film 52 having a thickness of 20
.mu.m. Subsequently, the optical waveguide 16 constructed by the
cladding layers 13 and 15 and the core 14 is formed on the
peelability promoting film 52 by, for example, a method similar to
that of the first embodiment. When a photosetting resin is used as
the material of the peelability promoting film 52, the resin is
irradiated with light so as to be set.
[0065] The peelability promoting film 52 is used to promote the
peelability between the transparent substrate 11 and the optical
waveguide 16 in a manner similar to the peelability promoting film
12 of the first embodiment. The peelability promoting film 52 is
excellently adhered to the cladding layer 13 at ordinary
temperature. As the material of the peelability promoting film 52,
a material having a glass transition temperature lower than that of
the material (such as epoxy resin) of the optical waveguide 16 is
used. The glass transition temperature denotes a temperature range
in which the viscosity of a solid substance decreases and the
material comes to have fluidity. The glass transition temperature
of the acrylic resin used in the embodiment is, for example, about
80.degree. C. and that of the epoxy resin is about 150 to
250.degree.C. It is suitable to use the combination of the
resins.
[0066] In a manner similar to the process shown in FIGS. 5A and 5B
of the first embodiment, the optical waveguide 16 and the
multilayer wiring board 17 are fixed to each other via the adhesive
layer 18 made of, for example, an epoxy resin.
[0067] Subsequently, a heat treatment is conducted at a temperature
which is higher than the glass transition temperature of the
material (acrylic resin) of the peelability promoting film 52 and
lower than the glass transition temperature of the material (epoxy
resin in this case) of the optical waveguide 16, for example, at
100.degree. C. Further, it is preferable to carry out the heat
treatment at a temperature lower than the glass transition
temperature of the multilayer wiring board 17. When the temperature
of the peelability promoting film 52 becomes higher than the glass
transition temperature of the film 52, the peelability promoting
film 52 exhibits glass transition to a liquid state. As shown in
FIGS. 15A and 15B, the transparent substrate 11 is easily peeled
off from the optical waveguide 16 together with the peelability
promoting film 52. Since the heat treatment is conducted at a
temperature lower than the glass transition temperature of each of
the materials of the optical waveguide 16, multilayer wiring board
17 and adhering layer 18, there is no possibility that the optical
waveguide 16, multilayer wiring board 17 and adhesive layer 18 are
damaged by the heat treatment.
[0068] After that, although not shown, in a manner similar to the
first embodiment, the semiconductor laser, photodiode, IC chip and
the like are mounted on the multilayer wiring board 17 by, for
example, flip-chip bonding. Further, by using a sealing resin, the
semiconductor laser, photodiode, IC chip and the like are
sealed.
[0069] As described above, according to the method of manufacturing
the optical transmitting/receiving apparatus of the embodiment, for
a reason similar to the first embodiment, the optical
transmitting/receiving apparatus having the optical waveguide 16 in
which the light propagation loss is small can be manufactured. The
peelability promoting film 52 made of a material having a glass
transition temperature lower than that of the material of the
optical waveguide 16 is provided between the transparent substrate
11 for forming the optical waveguide and the optical waveguide 16,
in a post process. Therefore, when a heat treatment is performed at
a temperature which is higher than the glass transition temperature
of the forming material of the peelability promoting film 52 and is
lower than the glass transition temperature of the forming material
of the optical waveguide 16, the transparent substrate 11 can be
easily peeled off from the optical waveguide 16 without damaging
the optical waveguide 16.
[0070] (Fourth Embodiment)
[0071] The fourth embodiment relates to a method of manufacturing
an optical transmitting/receiving apparatus. In the optical
transmitting/receiving apparatus as the object, like the second
embodiment, optical waveguides are separated from each other.
Referring now to FIGS. 16A and 16B and FIGS. 17A and 17B, the
method of manufacturing the optical transmitting/receiving
apparatus of the embodiment will be described hereinbelow. FIGS.
16A and 17A are cross sections orthogonal to the longitudinal
direction of the optical waveguide. FIGS. 16B and 17B are cross
sections parallel to the longitudinal direction of the optical
waveguide. FIG. 16A is a cross section taken along line XVIA-XVIA
of FIG. 16B and FIG. 17A is a cross section taken along line
XVIIA-XVIIA of FIG. 17B. The same components as those of the first
to third embodiments are designated by the same reference numerals
and the detailed description is omitted here.
[0072] First, as shown in FIGS. 16A and 16B, the peelability
promoting film 52 made of an acrylic resin or the like is formed on
the transparent substrate 11. Subsequently, on the peelability
promoting film 52, in a manner similar to the second embodiment, a
plurality of optical waveguides 36 which are apart from each other
are formed. Each of the optical waveguides 36 is constructed by the
cladding layers 33 and 35 and the core 34. Then, in a manner
similar to the second embodiment, the adhesive 42 is applied on the
optical waveguides 36, and the optical waveguides 36 are adhered to
the multilayer wiring board 17. After that, the transparent
substrate 11 is irradiated with parallel light that travels toward
the multilayer wiring board 17, thereby fixing the optical
waveguides 36 and the multilayer wiring board 17 to each other.
[0073] A heat treatment is performed at a temperature which is
higher than the glass transition temperature of the material
(acrylic resin in this case) of the peelability promoting film 52
and lower than the glass transition temperature of the material of
each of the optical waveguide 36 and the multilayer wiring board
17. By the heat treatment, as shown in FIGS. 17A and 17B, the
transparent substrate 11 is easily peeled off together with the
peelability promoting film 52 from the optical waveguide 36. The
subsequent processes are similar to those of the first to third
embodiments.
[0074] In a manner similar to the second embodiment, although there
is a case such that the peelability promoting film 52 partly or
entirely remains on the optical waveguide 36 side, in such a case
as well, the transparent substrate 11 is easily peeled off from the
optical waveguide 36.
[0075] As described above, according to the method of manufacturing
the optical transmitting/receiving apparatus of the embodiment, for
a reason similar to the second embodiment, the plurality of optical
waveguides 36 on the transparent substrate 11 can be excellently
and easily transferred onto the multilayer wiring board 17. The
optical waveguides 36 can be transferred only in the necessary
portions of the multilayer wiring board 17. Since the peelability
promoting film 52 comprising a material having a glass transition
temperature lower than that of the optical waveguide 36 is provided
on the transparent substrate 11, when a heat treatment is conducted
in a post process at a temperature which is higher than the glass
transition temperature of the material of the peelability promoting
film 52 and is lower than the glass transition temperature of the
material of the optical waveguide 36, the transparent substrate 11
can be easily peeled off from the optical waveguide 36 without
damaging the optical waveguide 36.
[0076] Although the invention has been described above by some
embodiments, the invention is not limited to the foregoing
embodiments but can be variously modified. For example, although
the peelability promoting film 12 is made of liquid silicone in the
first and second embodiments, the peelability promoting film 12 can
be made of silicone in a gel state, or other materials such as
siloxane that can promote the peelability between the transparent
substrate 11 and the optical waveguide.
[0077] Although the peelability promoting film 52 is formed by
applying the acrylic resin on the transparent substrate 11 in the
third and fourth embodiments, the peelability promoting film 52 may
be formed by laminating a film sheet made of an acrylic resin or
the like on the transparent substrate 11. The material of the
peelability promoting film 52 is not limited to the acrylic resin.
Any material can be used as long as its glass transition
temperature is lower than that of the material of the optical
waveguides 16 and 36.
[0078] Further, although the adhering layer 18 is applied on the
electric wiring substrate 17 side in the first and third
embodiments, the adhering layer 18 may be applied on the optical
waveguide 16 side.
[0079] In the second and fourth embodiments, the optical waveguide
36 is fabricated by forming the cladding layers 33 and 35 and the
core 34 by selectively exposing the epoxy resin layer.
Alternatively, in a manner similar to the first embodiment, it is
possible to form the cladding layers 13 and 15 and the core 14
which are used as an optical waveguide precursor layer and to
perform a process of dry etching such as RIE using an oxygen (O)
plasma on the optical waveguide precursor layer to obtain a
plurality of optical waveguides which are apart from each other.
Further, the optical waveguides may be also split by another
mechanical method such as etching using powders.
[0080] In the second and fourth embodiments, after adhering the
adhesive 42 on the substrate 41 to the cladding layer 33, the
multilayer wiring board 17 and the cladding layer 33 are fixed to
each other via the adhesive 42. Alternatively, it is possible to
adhere the multilayer wiring board 17 and the optical waveguide 36
to each other by applying a photosetting adhesive on the whole
surface of the multilayer wiring board 17 and by selectively
exposing and setting the adhering layer only, in the region in
which the optical waveguide 36 is formed, by using a shielding film
or the like.
[0081] Although the case where the material of each of the adhering
layer 18 and the adhesive 42 has the photosetting property has been
described in each of the embodiments, each of the adhering layer 18
and the adhesive 42 may be made of a thermosetting material. In
this case, a proper heat treatment is performed to set the
thermosetting material.
[0082] Further, although each of the cladding layer and the core
layer is made of an epoxy resin in each of the embodiments,
polyimide, an acrylic resin such as PMMA, a polyolefine resin such
as polyethylene or polystyrene, a synthetic rubber or the like can
be used. Further, it is also possible to increase transparency by
using a material obtained by adding fluorine to any of the above
resins.
[0083] As described above, in the method of manufacturing the
optical waveguide or the method of manufacturing the optical
transmitting/receiving apparatus according to one aspect of the
invention, the optical waveguide formed on the first substrate is
transferred to the second substrate. Consequently, the optical
waveguide that can be conventionally formed only on an expensive
substrate having an excellent heat resisting property can be formed
on a less expensive substrate made of an arbitrary material in an
arbitrary shape. By using a very flat substrate as the first
substrate, the optical waveguide in which the light propagation
loss is small can be fabricated. Further, since the peelability
between the first substrate and the optical waveguide is promoted
by providing the peelability promoting film between the first
substrate and the optical waveguide, the first substrate can be
easily peeled off from the optical waveguide.
[0084] In the method of manufacturing the optical waveguide
according to another aspect of the invention, the peelability
promoting film made of a material having a glass transition
temperature lower than that of the material of the optical
waveguide is provided between the first substrate and the optical
waveguide, and in a later step of peeling the first substrate off
from the optical waveguide, the heat treatment is performed at a
temperature higher than the glass transition temperature of the
material of the peelability promoting film. Consequently, while
assuring the adhesion of the optical waveguide to the first
substrate, the transfer of the optical waveguide to the second
substrate can be facilitated.
[0085] In the method of manufacturing the optical waveguide
according to further another aspect of the invention, a plurality
of optical waveguides which are separated from each other are
formed on the first substrate and are transferred from the first
substrate side to the second substrate side. Thus, the plurality of
optical waveguides that are separated from each other can be
transferred to desired regions in an arbitrary substrate.
[0086] Obviously many modifications and variations of the present
invention are possible in the light of the above teachings. It is
therefore to be understood that within the scope of the appended
claims the invention may be practiced otherwise than as
specifically described.
* * * * *