Optical waveguides – Integrated optical circuit
Reexamination Certificate
2003-05-06
2004-12-28
Healy, Brian M. (Department: 2883)
Optical waveguides
Integrated optical circuit
C385S129000, C385S130000, C385S131000, C346S107100, C346S135100
Reexamination Certificate
active
06836579
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a surface optical device apparatus which can be readily fabricated with good yield and is suitable for use in a structure constructed in a one- or two-dimensional array, its fabrication method, an optoelectronic device in which the surface optical device is integrated together with a Si integrated circuit (Si-IC), an optical wiring device using the surface optical device apparatus, an optical recording apparatus using the surface optical device apparatus, and related structures and devices.
2. Related Background Art
In recent years, the development of surface light emitting devices arranged in two-dimensional arrays has been desired. Among such devices, a vertical cavity surface emitting laser (VCSEL) is strongly expected since its threshold is low (approximately 1 mA), its power consumption is small, and it can be easily arrayed. Moreover, when a VCSEL is integrated with a Si-IC, the VCSEL can be speedily driven, and the device can be presented in a small package. Accordingly, such a structure can be advantageously applied to signal transmission between Si-IC's, to optical recording on a recording medium, and similar uses.
There are several methods of integrating an optical device and a Si-IC. In one method, an optical device is bonded to a Si substrate wherein Si-IC has been formed. In another method, a Si-IC and an optical device are integrated in a hybrid manner on a supporting substrate, such as a Si substrate, a printed circuit board (PCB), or a ceramic substrate.
As an example of the former method, there exists, as disclosed in Japanese Patent Application Laid-Open No. 9(1997)-223848, a method in which an epitaxial growth surface of a laser radiating layer is bonded to a Si-IC via a polyimide adhesive, and a GaAs growth substrate, on which the laser radiating layer had been grown, is removed by etching to obtain a surface emitting laser.
FIG. 1
illustrates a cross section of this structure. An electrode of the surface emitting laser
100
B fabricated by the above process is connected to an electrode
200
A on the Si-IC substrate
200
via electrical wiring
400
. Another electrode
100
D is connected to a wiring pattern formed on the insulating layer
300
of polyimide. In such a structure, no alignment is needed between the optical device and the Si-IC. Further, additional processing, such as photolithography, can be conducted even after the integration, since only a functional layer of the optical device without its growth substrate is arranged on the Si and a step of the surface is hence small (about 5 &mgr;m). In
FIG. 1
, a light receiving device
100
A, an electrode
100
C of the device
100
A and a layer
1000
of optical devices are illustrated as well.
As an example of the latter method, there exists, as disclosed in Japanese Patent Application Laid-Open No. 7(1995)-30209, a method in which a semiconductor substrate of an optical device is removed, the optical device in chip form is bonded to a film or the like, and the optical device is aligned with an electrode of an electronic circuit substrate and implemented in a flip-chip manner.
FIGS. 2A
to
2
H illustrate the fabrication steps according to this method. After a functional layer
1106
is epitaxially grown on the semiconductor substrate
1101
as illustrated in
FIG. 2A
, an electrode
1109
for driving the optical device
1111
is formed as illustrated in FIG.
2
B. The devices
1111
are then separated as illustrated in
FIG. 2C
, and the semiconductor substrate
1101
is removed by etching as illustrated in FIG.
2
D. The devices
1111
are bonded to an extensible film
1114
as illustrated in
FIG. 2E
, and the film
1114
is extended to obtain chips of the optical device
1111
with only the functional layer
1106
as illustrated in FIG.
2
F. The optical device
1111
is affixed at a desired area of an electronic circuit board
1117
with a pressing jig
1116
. Thus, an optoelectronic multi-chip-module (MCM), in which the optical device
1111
is placed on the electronic circuit substrate
1117
in a hybrid integration manner, as illustrated in
FIG. 2H
, can be obtained. In
FIGS. 2A
to
2
H, there are also illustrated a buffer layer
1102
, a lower mirror
1103
, an active layer
1104
, an upper mirror
1105
, an anode
1107
, a cathode
1108
. a mesa groove
1110
, a separating groove
1112
, a protective layer
1113
, a spacing
1115
, and an electrical wiring
1118
.
There are significant problems with the structure disclosed in Japanese Patent Application Laid-Open No. 9(1997)-223848, however. Its thermal radiation characteristic is poor, and its luminary characteristics, such as light radiation efficiency and light output, are inferior to those of ordinary implementation structures, since the polyimide layer
300
is interposed between the optical devices
100
A and
100
B and the Si substrate
200
. Further, since the fabrication process of the optical devices
100
A and
100
B is performed only after the functional layers of the optical devices are transferred to the Si substrate
200
, limitations on the freedom of the process (i.e., on processing temperature, plasma processing, and the like) arise, due to concerns with preventing damage to the IC. Accordingly, the configurations of the optical devices
100
A and
100
B are also restricted.
Concerning the structure of Japanese Patent Application Laid-Open No. 7(1995)-30209, its mechanical strength is low due to a small thickness (ordinarily about 5 &mgr;m) of the functional layer
1106
without the substrate, though its thermal conductivity is good due to direct bonding between the electrodes. Accordingly, its handling is difficult, and its performance characteristics are likely to be decreased due to the introduction of crystallographic defects therein, and the like. Furthermore, two electrodes must be aligned for each device since the electric contact should be established on the side of the circuit board
1117
only. Therefore, high alignment precision is required, and costs increase accordingly.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an apparatus with a surface optical device, in which characteristics of the surface optical device are not decreased with the integration of the surface optical device and the electronic device, where no high precision of alignment is required at the time of implementation, and whose productivity is high. It is a further object of the present invention to provide a method of fabricating such an apparatus, as well as other apparatuses which use such an apparatus, such as an optoelectronic MCM, an optical wiring apparatus and an optical recording apparatus, and related structures and methods.
The present invention is generally directed to a surface optical device apparatus including a surface optical device, and a second substrate. The surface optical device includes a functional layer grown on a first substrate, which acts as a supporting substrate needed for fabricating the functional layer thereon, with the first substrate being later thinned or removed, and a first electrode formed on at least one of the surfaces of the functional layer. The surface optical device emits or receives light in a direction approximately perpendicular to the first substrate, and the first electrode has a function for electrically controlling the light emission or reception. The second substrate includes a second electrode formed thereon, and the surface optical device is bonded to the second substrate with the first electrode and the second electrode being in electrical contact with each other. In the apparatus of this invention, the first substrate is removed or thinned by etching or the like after the optical device is bonded to the second substrate, such as a Si substrate or a circuit substrate, with the first and second electrodes electrically connected, and another electrode is led from a surface of the optical device exposed after the first substrate is removed or thinned. Accordingly, the the
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Healy Brian M.
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