U.S. patent application number 09/916442 was filed with the patent office on 2002-04-04 for method for manufacturing laser diode chip, optical transmitting/receiving module and method for aligning positions thereof.
Invention is credited to Jun, Hong Jun, Koo, Bon Jo, Lee, Ho Sung, Shin, Ki Chul, Song, Jun Seok, Yoon, Euy Sik.
Application Number | 20020039805 09/916442 |
Document ID | / |
Family ID | 26634154 |
Filed Date | 2002-04-04 |
United States Patent
Application |
20020039805 |
Kind Code |
A1 |
Yoon, Euy Sik ; et
al. |
April 4, 2002 |
Method for manufacturing laser diode chip, optical
transmitting/receiving module and method for aligning positions
thereof
Abstract
The present invention relates an optical element used in the
field of optical communication and a method for aligning an optical
fiber to connect an external optical communication system to the
optical element. The present invention relates to an optical
transmitting module which consists of a silicon substrate, an
optical fiber fixed to the substrate and a laser diode chip, with
the first fixing groove for supporting and fixing the optical
fiber, with the second fixing groove for supporting and fixing the
laser diode chip and with a mediating groove for positioning the
optical fiber and the laser diode chip at a definite distance, said
mediating groove being formed between the first and the second
groove, all those grooves being formed on the top side of said
substrate, wherein the first and the second fixing groove are each
formed in their predetermined depths on the top side of the
substrate so that the central axis of the optical fiber exactly
agrees with the center of optical beams from the laser diode chip,
the optical fiber and the laser diode chip being received in the
first and the second groove, with the result that the relation of
mutual positions for the optical fiber and the laser diode chip is
precisely determined merely by seating the optical fiber and the
laser diode chip in the first and the second groove. Further, the
present invention also relates to a method for manufacturing a
laser diode chip which comprises the steps of: vapor-depositing a
nitride thin film(Si.sub.3N.sub.4) on the surface of a wafer on
which the n type InP, p type InP, n type InP, p type InP and InGaAs
layers are successively laminated with the completion of the
tertiary MOCVD growth, and etching the InGaAs layer by using the
mixed solution of sulfuric acid, hydrogen peroxide and distilled
water after opening an etching window by means of photolithography
to form V-mesa and V-grooves; etching an InP layer as a current
cut-off layer by using a solution based on a hydrochloric acid;
vapor-depositing a nitride thin film(SiNx) by using a PECVD
process; opening the electrode forming window to form electrodes by
means of a photolithography and forming P type electrodes on the
surface of the wafer; forming a N type electrode on the back
surface of the wafer after polishing the bottom surface.
Inventors: |
Yoon, Euy Sik; (Anyang-shi,
KR) ; Jun, Hong Jun; (Anyang-shi, KR) ; Shin,
Ki Chul; (Anyang-shi, KR) ; Song, Jun Seok;
(Anyang-shi, KR) ; Koo, Bon Jo; (Anyang-shi,
KR) ; Lee, Ho Sung; (Anyang-shi, KR) |
Correspondence
Address: |
LONG ALDRIDGE & NORMAN LLP
Suite 600
701 Pennsylvania Avenue, N.W.
Washington
DC
20004
US
|
Family ID: |
26634154 |
Appl. No.: |
09/916442 |
Filed: |
July 30, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09916442 |
Jul 30, 2001 |
|
|
|
09401922 |
Sep 23, 1999 |
|
|
|
Current U.S.
Class: |
438/42 ; 257/433;
257/98; 438/47 |
Current CPC
Class: |
H01S 5/02251 20210101;
H01S 5/02326 20210101; G02B 6/423 20130101; G02B 6/4224 20130101;
H01S 5/0202 20130101 |
Class at
Publication: |
438/42 ; 438/47;
257/98; 257/433 |
International
Class: |
H01L 021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 24, 1998 |
KR |
1998-39767 |
Dec 31, 1998 |
KR |
1998-63651 |
Claims
What is claimed is:
1. A method for manufacturing a laser diode chip comprising the
steps of: (1) vapor-depositing a nitride thin film(Si3N4) on the
surface of a wafer on which the n type InP, p type InP, n type InP,
p type InP and InGaAs layers are successively laminated with the
completion of the tertiary MOCVD growth, and etching the InGaAs
layer by using the mixed solution of sulfuric acid, hydrogen
peroxide and distilled water after opening an etching window by
means of photolithography to form V-grooves as cutting sites with a
view to control the size of laser diode chip within .+-.1 micron
(2) etching an InP layer as a current cut-off layer by using a
solution based on a hydrochloric acid; (3) vapor-depositing a
nitride thin film(SiNx) by using a PECVD process; (4) opening the
electrode forming window to form electrodes by means of a
photolithography and forming P type electrodes on the surface of
the wafer; (5) forming a N type electrode on the back surface of
the wafer after polishing the bottom surface and (6) manufacturing
laser diode chips having a desired size by cutting the V-grooves on
the chip set with a breaker, when the laser diode chip set with
V-grooves is completed through the above described steps of (1) to
(5).
2. An optical transmitting module consisting of a silicon
substrate, an optical fiber fixed to the substrate and a laser
diode chip, with the first fixing groove for supporting and fixing
the optical fiber, with the second fixing groove for supporting and
fixing the laser diode chip and with a mediating groove for
positioning the optical fiber and the laser diode chip at a
definite distance, said mediating groove being formed between the
first and the second groove, all those grooves being formed on the
top side of said substrate, wherein the first and the second fixing
groove are each formed in their predetermined depths on the top
side of the substrate so that the central axis of the optical fiber
exactly agrees with the center of optical beams from the laser
diode chip, the optical fiber and the laser diode chip being
received in the first and the second groove, with the result that
the relation of mutual positions for the optical fiber and the
laser diode chip is precisely determined merely by seating the
optical fiber and the laser diode chip in the first and the second
groove.
3. The optical transmitting module according to claim 2, wherein
said laser diode chip is manufactured by the method defined in
claim 1.
4. The optical transmitting module according to claim 3, wherein
the size of the bottom surface of said second fixing groove is the
same as that of the laser diode chip, is smaller as compared to the
top width of the groove and is formed flat to stably receive the
bottom surface of the laser diode chip.
5. A method for aligning an optical transmitting module comprising
the steps of: preparing a laser diode chip manufactured by the
method defined in claim 1, in order to form the first fixing groove
for fixing an optical fiber, the second fixing groove for fixing a
laser diode chip and a mediating groove for connecting the first
and the second fixing groove on the top surface of a silicon
substrate, forming patterns corresponding to those grooves by
using. a photolithography; etching the first fixing groove, the
second groove and the mediating groove by using potassium hydroxide
solution; forming metal patterns on the first fixing groove and the
second fixing groove, each formed by etching process; and
positioning the optical fiber and the laser diode chip in the first
and the second fixing groove formed with the metal patterns,
followed by fixing of the fiber and the chip.
6. The method according to claim 5, wherein said second fixing
groove has its base which corresponds in size to the bottom surface
of the laser diode chip, is smaller in size in comparison to the
top width of the groove and is formed flat to stably receive the
laser diode chip.
7. An optical receiving module consisting of a silicon substrate,
an optical fiber fixed to the substrate and a photodiode chip, with
the first fixing groove for supporting and fixing the optical
fiber, with the second fixing groove for supporting and fixing the
photodiode chip and with a mediating groove for positioning the
optical fiber and the photodiode chip at a definite distance, said
mediating groove being formed between the first and the second
groove, all those grooves being formed on the top side of said
substrate, wherein the first and the second fixing groove are each
formed in their predetermined depths on the top side of the
substrate so that the light emitting from the optical fiber can be
transmitted to the photodiode chip without loss, with the result
that the relation of mutual positions for the optical fiber and the
photodiode chip is precisely determined merely by seating the
optical fiber and the photodiode chip in the first and the second
groove.
8. The optical receiving module according to claim 7, wherein on
the central area of the base of the second fixing groove, a laser
beam guiding slot which extends in line with the first fixing
groove, in a location corresponding to the bottom surface of the
photodiode chip, and which has its base at the same elevation as
the first fixing groove is further formed, so that the laser beams
from the optical fiber may be correctly guided.
9. The optical receiving module according to claim 8, wherein the
top width of the laser beams guiding groove is larger than the size
of the light receiving window on the photodiode chip.
10. The optical receiving module according to claim 9, wherein the
first and the second fixing groove are arranged in opposed relation
in contact with the opposite ends of the mediating groove.
11. The optical receiving module according to claim 10, wherein the
first and the second fixing groove extend in a straight line and
the mediating groove extends at the right angle to the first fixing
groove.
12. A method for aligning an optical receiving module comprising
the steps of: forming patterns corresponding to those grooves by
using a photolithography, wherein the pattern for the mediating
groove is so formed that the mediating groove extends perpendicular
to the optical axis, in order to form the first fixing groove for
fixing an optical fiber, the second fixing groove for fixing a
photodiode chip and a mediating groove for connecting the first and
the second fixing groove on the top surface of a silicon substrate;
etching the first fixing groove, the second groove and the
mediating groove by using potassium hydroxide solution, wherein the
second fixing groove is formed in such a manner that its bottom
surface lies a little higher than the base surface of the first
fixing groove; forming further a laser beam guiding slot, which
extends in line with the first fixing groove and which has its base
at the same elevation as the first fixing groove, on the central
area of the base of the second fixing groove; forming metal
patterns on the first fixing groove and the second fixing groove;
and seating the optical fiber with its bottom in the first fixing
groove, followed by fixing thereof and seating the photodiode chip
with its bottom surface in the laser beam guiding groove, followed
by fixing thereof.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an optical element used in
the field of optical communication and a method for aligning an
optical fiber, laser diode chip or photodiode chip to connect an
external optical communication system to the optical element.
[0002] Particularly, the present invention also relates to a method
for manufacturing a laser diode chip which is used to convert
electric signals into optical waves in the communication system
using optical fibers.
[0003] Further, the present invention relates to a method for
aligning the positions between a laser diode chip and an optical
fiber as well as between a photodiode chip and an optical fiber in
the optical fiber communication system.
BACKGROUND OF THE INVENTION
[0004] For an optical communication, an optical transmitting module
to convert electric signals into optical signals for transmitting
as well as an optical receiving module to convert optical signals
into electric signals for receiving are essential.
[0005] In addition, the art with which a variety of optical
elements for generating, detecting, modulating and distributing
functions of a light are attached with optical fibers and packaged
is essential for commercializing all sorts of communicating
elements.
[0006] In the process for packaging optical modules, one of the
most difficult and costly steps is that of aligning and fixing an
optical fiber in the wave guiding path of an optical element which
represents a determinant factor for the cost of an optical
communication module.
[0007] That rests on the difficulty in spatially aligning an
optical element and an optical fiber, and holding the both in the
aligned position without displacement in view of the very small
area for the optical input or output of an optical element in the
order of a few square micrometers and also the small area for the
optical input or output of an optical fiber in the order of several
tens of square micrometers.
[0008] The conventional methods for aligning an optical
transmitting module and an optical receiving module may be broadly
divided into an active aligning method and a passive aligning
method.
[0009] However, the active aligning method has a difficulty in cost
reduction because it needs a long processing time and many parts
due to the use of lenses and an expensive laser welder.
[0010] On the other hand, the passive aligning methods can be
performed without the use of those lenses and laser welders and
therefore are coming to the front as new methods for reducing the
price of the optical communication modules.
[0011] According to a conventional passive aligning method as shown
in FIG. 14, after the chip marker 1022 on the bottom surfact of a
laser diode chip 1010 is caused to match the substrate marker 1014
on the top surface of a substrate 1000, the laser diode chip 1010
is bonded to the metal junction layer 1012 of the silicon substrate
1000 by using a flip chip bonder.
[0012] The method using markers as described above is not much more
advantageous in the point of the required time for process as
compared to the active aligning method and also has a drawback of
an increased installation cost for the equipment like a flip chip
bonder.
[0013] Another conventional passive aligning method is shown in
FIG. 15.
[0014] In this method, first a support 2040 loaded with a laser
diode chip 2010 is fixed bonded on the surface of a substrate 2030
and then mounts 2050 and 2060 are fixed to the substrate 2030.
Subsequently, the optical fiber 2020 is caused to be received, with
its end close to the laser diode chip 2010, in the groove 2051
formed on the mount 2050 and then the optical fiber 2020 is aligned
in its position with regard to the laser diode chip 2010 by
adjusting the position of the end of the optical fiber 2020, which
end positions on the side of the mount 2050. When the optical fiber
2020 has been precisely aligned in position through those
procedures, the optical fiber 2020 is fixed to the mount 2060, for
example, through soldering.
[0015] For the optical communication module according to FIG. 15 as
described above, the positions in which the mounts and the support
will be fixed are not exactly determined and therefore a great deal
of time is spent to find optimum fixing positions at the time of
mounting work. Nevertheless there arise deviations in the fixing
positions depending on the individual products because the mounts
or the supports are not exactly positioned.
[0016] Accordingly, the position alignment operation for the
optical fiber with regard to the laser diode chip is not only
difficult but the fixing positions of the mounts and supports with
unduly high errors can also cause the problem that the optical
fiber is not properly lined up with the axis of the laser diode
chip.
[0017] An improved optical communication module intended to solve
the above-described problem is disclosed in the Korean Patent
Application No. 1997-044417.
[0018] Referring to FIG. 16 concerning the corresponding art, the
art is characterized in that the position determining means 3091,
3092 and 3093 to define the positions in which the support 3040 and
the mounts 3050 and 3060 are to be fixed are provided.
[0019] In particular, the support 3040 on which the laser diode
chip 3010 is mounted is inserted into the first position
determining groove 3091 on the substrate 3030 and fixed there
through bonding or the like. Then, the mount 3050 is inserted into
the second position determining groove 3092 and the mount 3060 is
inserted into the third position determining groove 3093 on the
substrate 3030 and then fixed through bonding.
[0020] Subsequently, after the optical fiber 3020 is placed on the
mount 3050 with its end close to the laser diode chip 3010 received
in the groove 3051, the optical fiber 3020 is brought into a
correct position for alignment with the laser diode chip 3010 by
adjusting the position of the optical fiber 3020 at its end part on
the side of the mount 3050.
[0021] When the optical fiber 3020 has been precisely set in its
desired position, the optical fiber 3020 is fixed to the mount 3060
through soldering or the like.
[0022] Because the support 3040 and the mounts 3050 and 3060 are
fixed after they were inserted into their respective position
determining grooves 3091, 3092 and 3093 in the assembling operation
as described above, even in the case of mass production of optical
communication modules, the positions of the support 3040 and the
mounts 3050 and 3060 relative to that of the substrate 3030 can
always be maintained definite.
SUMMARY OF THE INVENTION
[0023] The primary object of the present invention is to provide a
process for manufacturing laser diode chips on a large scale, which
diodes can be controlled within the order of .+-.1 micron in the
tolerance of size, through an etching step.
[0024] The second object of the present invention is to improve the
structure of a silicon substrate on which an optical fiber and a
laser diode chip are positioned so that the optical fiber and the
laser diode chip can be exactly aligned with each other.
[0025] The third object of the present invention is to provide a
passive aligning method for an optical communication module which
permits a precise positioning of an optical fiber and a laser diode
chip on a substrate.
[0026] The fourth object of the present invention is to reduce the
manufacturing cost for an optical communication module by enabling
an optical fiber and a laser diode chip to be aligned in a passive
manner on a silicon substrate without
[0027] the use of high-priced bonding equipment.
[0028] The fifth object of the present invention is to improve the
construction of a silicon substrate on which an optical fiber and a
photodiode chip is positioned so that an exact alignment of the
optical fiber with the photodiode chip can be achieved.
[0029] The sixth object of the present invention is to provide a
passive method for aligning an optical receiving module which
permits an exact positioning of an optical fiber and a photodiode
chip on a silicon substrate.
[0030] The seventh object of the present invention is to reduce the
cost for manufacturing an optical receiving module through aligning
an optical fiber and a photodiode chip on a silicon substrate in a
passive manner without the use of an expensive boding
equipment.
[0031] Finally, the eighth object of the present invention is to
improve the exactness of packaging process and to reduce the
required time in making the optical transmitting module and the
optical receiving module packagable.
[0032] The above described objects are achieved by a method for
manufacturing a laser diode chip according to an embodiment of the
invention which comprises the steps of: (1) vapor-depositing a
nitride thin .sub.film(Si.sub.3N.sub.4) on the surface of a wafer
on which the n type InP, p type InP, n type InP, p type InP and
InGaAs layers are successively laminated with the completion of the
tertiary MOCVD growth, and etching the InGaAs layer by using the
mixed solution of sulfuric acid, hydrogen peroxide and distilled
water after opening an etching window by means of photolithography
to form V-grooves as cutting sites with a view to control the size
of laser diode chip within .+-.1 micron ; (2) etching an InP layer
as a current cut-off layer by using a solution based on a
hydrochloric acid; (3) vapor-depositing a nitride thin film(SiNx)
by using a PECVD process; (4) opening the electrode forming window
to form electrodes by means of a photolithography and forming P
type electrodes on the surface of the wafer; (5) forming a N type
electrode on the back surface of the wafer after polishing the back
surface of the wafer and (6) manufacturing laser diode chips having
a desired size by cutting the V-grooves on the chip set with a
breaker, when the laser diode chip set with V-grooves is completed
through the above described steps of (1) to (5).
[0033] The above described objects are also achieved by an optical
transmitting module according to another embodiment of the
invention which consists of a silicon substrate, an optical fiber
fixed to the substrate and a laser diode chip, with the first
fixing groove for supporting and fixing the optical fiber, with the
second fixing groove for supporting and fixing the laser diode chip
and with a mediating groove for positioning the optical fiber and
the laser diode chip at a definite distance, said mediating groove
being formed between the first and the second grooves, all those
grooves being formed on the top side of said substrate, wherein the
first and the second fixing groove are each formed in their
predetermined depths on the top side of the substrate so that the
central axis of the optical fiber exactly may agree with the center
of optical beams from the laser diode chip, the optical fiber and
the laser diode chip being received in the first and the second
groove, with the result that the relation of mutual positions for
the optical fiber and the laser diode chip is precisely determined
merely by seating the optical fiber and the laser diode chip in the
first and the second groove.
[0034] The above described objects are also achieved by a method
for aligning an optical transmitting module according to another
embodiment of the present invention which comprises the steps of:
preparing a laser diode chip manufactured by the method defined in
claim 1, in order to form the first fixing groove for fixing an
optical fiber, the second fixing groove for fixing a laser diode
chip and a mediating groove for connecting the first and the second
fixing groove on the top surface of a silicon substrate, forming
patterns corresponding to those grooves by using a
photolithography, etching the first fixing groove, the second
groove and the mediating groove by using potassium hydroxide
solution, forming metal patterns on the first fixing groove and the
second fixing groove, each formed by etching process, positioning
the optical fiber and the laser diode chip in the first and the
second fixing groove formed with the metal patterns, followed by
fixing of the fiber and the chip.
[0035] The above described objects are also achieved by an optical
receiving module according to still other embodiment of the present
invention which consists of a silicon substrate, an optical fiber
fixed to the substrate and a photodiode chip, with the first fixing
groove for supporting and fixing the optical fiber, with the second
fixing groove for supporting and fixing the photodiode chip and
with a mediating groove for positioning the optical fiber and the
photodiode chip at a definite distance, said mediating groove being
formed between the first and the second groove, all those grooves
being formed on the top side of said substrate, wherein the first
and the second fixing groove are each formed in their predetermined
depths on the top side of the substrate so that the light emitting
from the optical fiber can be transmitted to the photodiode chip
without loss, with the result that the relation of mutual positions
for the optical fiber and the photodiode chip is precisely
determined merely by seating the optical fiber and the photodiode
chip in the first and the second groove.
[0036] The above described objects are also achieved by a method
for aligning an optical receiving module according to still other
embodiment of the present invention which comprises the steps of:
in order to form the first fixing groove for fixing an optical
fiber, the second fixing groove for fixing a photodiode chip and a
mediating groove for connecting the first and the second fixing
groove on the top surface of a silicon substrate, forming patterns
corresponding to those grooves by using a photolithography, wherein
the pattern for the mediating groove is so formed that the
mediating groove extends perpendicular to the optical axis, etching
the first fixing groove, the second groove and the mediating groove
by using potassium hydroxide solution, wherein the second fixing
groove is formed in such a manner that its bottom surface lies a
little higher than the base surface of the first fixing groove,
forming further a laser beam guiding slot, which extends in line
with the first fixing groove and which has its base at the same
elevation as the first fixing groove, on the central area of the
bottom surface of the second fixing groove, forming metal patterns
on the first fixing groove and the second fixing groove, and
seating the optical fiber with its bottom surface in the first
fixing groove, followed by fixing thereof and seating the
photodiode chip with its bottom surface in the laser beam guiding
groove, followed by fixing thereof.
[0037] The present invention allows the use of simpler equipments
and a passive type alignment method for speedy alignment mainly
through the enabled control of the size of the laser diode chip
within 1 micron thanks to cutting of laser diode chips under the
use of etching process.
[0038] The present invention, wherein individual laser diode chips
are formed from the chip set through a step of etching and V
grooves are formed on the silicon substrate for alignment of the
laser diode chip, does not need provision of markers for the
purpose of alignment as in the conventional art and permits use of
an ordinary die bonder for mounting the laser diode chip, whereby
the reduction in the required processes and the saving in the
installation cost of equipments are achieved.
[0039] Furthermore, the present invention, in which a groove is
already provided to receive a photodiode chip, contrary to the
conventional art, and a direct and ready mounting of a photodiode
chip on a silicon substrate is possible, has the advantage of
lesser constituting parts and simpler process as compared to the
prior art.
[0040] Other objects and advantages of the invention will be
understood from the following description of some preferred
embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 shows the state of a wafer on which V grooves are
etched to manufacture laser diode chips,
[0042] FIGS. 2 through 6 show the processing steps to manufacture
laser diode chips,
[0043] FIG. 7 shows the perspective view of a laser diode chip
manufactured according to the invention,
[0044] FIG. 8 shows the arrangement of an optical transmitting
module, illustrating the optical fiber is aligned, according to an
embodiment of the invention.
[0045] FIG. 9 shows a set of laser diode chips before cutting,
featuring V-grooves according to the invention,
[0046] FIG. 10 shows the arrangement of patterns for etching, to be
applied in an optical transmitting module according to the
invention,
[0047] FIG. 11 shows the mounted state for a laser diode chip, to
be applied in an optical transmitting module according to the
invention.
[0048] FIG. 12 shows a plan view of a silicon substrate to be used
in an automatic aligning and mounting method for a photodiode chip
according to an embodiment of the invention,
[0049] FIG. 13 shows a perspective view of an optical receiving
module according to the invention,
[0050] FIG. 14 shows a silicon substrate and a laser diode chip
before the alignment according to a conventional art,
[0051] FIG. 15 shows schematically the exploded perspective view of
a conventional optical communication module and
[0052] FIG. 16 shows schematically the exploded perspective view of
another conventional optical communication module.
DETAILED DESCRIPTION OF THE INVENTION
[0053] The present invention is described below with regard to some
preferred embodiments in conjunction with the attached
drawings.
[0054] It is noted that the following description will be
restricted to the parts essential for understanding the
construction and function of the invention and so the rest parts
will be excluded to clarify the substance of the invention.
[0055] A. Manufacture of a laser Diode Chip.
[0056] The improvement of the conventional active and passive
methods for aligning an optical fiber and a laser diode chip
requires an art for controlling the size of a laser diode chip
within the controllable range of 1 .mu.m.
[0057] Thus, the inventors of the present invention have developed
a process for manufacturing a diode chip which permits controlling
the size of a laser diode chip to be a desired size by improving
the conventional scribing and breaking processes based on the
mechanical cutting of chips.
[0058] According to the present invention, as shown in FIG. 1, in
order to manufacture a chip bar from a wafer 11 on which the
tertiary MOCVD growth has been completed, V mesas 12 are formed in
the direction of <110> on an edge of the wafer through a
chemical etching process under the use of mask, instead of the
conventional method wherein the scribing is conducted with a
diamond cutter in the direction of <110>. And instead of the
conventional method wherein the scribing is conducted with a
diamond cutter in the direction of <110> to cut chips out
from the chip bar, V grooves 13 in almost vertical direction are
formed in the direction of <110> through a chemical etching
process under the use of mask.
[0059] The numeral 15 not mentioned yet stands for the active
area.
[0060] The manufacturing process for a laser diode chip according
to the invention will be described below with reference to FIGS. 2
through 7.
[0061] A P type InP 18, N type InP 19, and P type InP 20 layers are
successively formed on a N type InP substrate 17 by means of MOCVD
process and subsequently an InGaAs layer 21 is vapor-deposited on
the surface of the layer 20.
[0062] When the tertiary MOCVD growth has been finished as
described above, a Si.sub.3N.sub.4 thin film 22 is vapor-deposited
on the InGaAs layer 21. When the deposition of the nitride thin
film 22 is completed, the etching window for etching V mesas and V
grooves is opened with the photolithography process.
[0063] The V grooves 13 described in the foregoing serve as cutting
sites at which cutting takes place to produce individual laser
diode chip with the desired size.
[0064] The process is described in detail step by step by referring
to FIGS. 2 to 6.
[0065] When the etching window is opened, a part of the InGaAs
layer 21 on the top of the substrate is removed with the mixed
solution of sulfuric acid, hydrogen peroxide and distilled
water.(Refer to FIG. 2).
[0066] With the completion of etching for the InGaAs layer, a part
of the InP layers 18, 19 and 20 as current cut-off layers are
etched off by using a solution based on hydrochloric acid. (Refer
to FIG. 3).
[0067] After the InP layers 18, 19 and 20 are etched, the nitride
thin film in the form of SiNx 22 is deposited in the PECVD process.
(Refer to FIG. 4).
[0068] With the nitride thin film 22 deposited, the
photolithography is employed to open the etching window for forming
electrodes and P type electrodes 25 are formed. (Refer to FIG.
5).
[0069] With the P type electrodes 25 formed, the wafer is polished
on its back surface to be provided with a N type electrode 27.
(Refer to FIG. 6).
[0070] When both the P type electrode and the N type electrodes are
finished, the wafer is divided into respective chips through a
breaking process, whereby the laser diode chips which have been
subjected to the control in the size are completed. A finished
laser diode chip is illustrated in a perspective view in FIG.
7.
[0071] B. Method for Aligning an Optical Transmitting Module and an
Optical Transmitting Module.
[0072] FIG. 8 shows an external perspective view of an optical
transmitting module according to the invention.
[0073] The optical transmitting module 100 consists of a silicon
substrate 110, the first fixing groove 121 formed on the substrate,
the second fixing groove 131, a mediating groove 111, a laser diode
chip 130 as an optical source and an optical fiber 120 for
providing a wave path.
[0074] The first fixing groove 121 is intended to retain the
optical fiber and the second fixing groove 131 is intended to
retain the laser diode chip as an optical source.
[0075] The mediating groove 111 is formed between the first and the
second fixing groove 121 and 131 to keep apart the optical fiber
120 and the laser diode chip 130 at a definite distance.
[0076] The first fixing groove 121 and the mediating groove 111 are
both substantially in V form but the former is bored deeper than
the latter.
[0077] As for the second fixing groove 131, the dimension of its
base corresponds to that of the bottom surface of the laser diode
chip, its top width is larger than its bottom width and its base
surface is flat so that the bottom surface of the diode chip may be
stably received. Thus side walls of the second fixing groove 131
are inclined inwardly with depth.
[0078] Particularly, it was found that the inclination of. the side
walls of the second fixing groove 131 at about 54.7.degree.
relative to the vertical line is preferable.
[0079] The first and the second fixing groove 121 and 131 face each
other, with the mediating groove 111 interposed therebetween.
[0080] The first and the second fixing groove 121 and 131 are
aligned in the same line or in the same vertical plane so that the
light beams emitted from the laser diode chip 130 can be input into
the optical fiber 120 without any loss.
[0081] The numeral 140 not mentioned so far indicates a metal
pattern layer.
[0082] The laser diode chip 130 which was made according to the
manufacturing process depicted in FIGS. 2 through 6 is adjusted to
be constant in its width.
[0083] Referring to FIG. 9, the cutting sites 170 in V form with a
predetermined width and depth are formed through an etching process
on the diode chip sets 150 for precise control of the width of
laser diode chips while the diode chips were usually divided by
means of a scriber in the prior art.
[0084] As the etchant, the hydrochloric acid based solution is
used, and the etching depth is decided in the range of ca. 3-5
.mu.m.
[0085] Thus, when an external stress is acted on a cutting site 170
formed on the laser diode chip set 150, a shear force is generated
along the dotted line extended down from the notch, as shown in the
drawing, whereby the individual laser diode chips 130 with a preset
size are provided through breaking at each notch site.
[0086] Next, the process for providing the laser diode chip 130 and
the optical fiber 120 on a silicon substrate 110. is described by
referring to FIGS. 10 and 11.
[0087] When the silicon nitride thin film is coated by the plasma
enhanced chemical vapor deposition(PECVD) under the use of masking
on the top surface of silicon substrate 110, an optical fiber
pattern area 110A for the position of the optical fiber 120, a
laser diode chip pattern area 110B for the place of the laser diode
chip 130 and a mediating groove pattern area 110C to space the
optical fiber 120 and the laser diode chip 130 are formed.
[0088] Then, on the respective pattern areas 110A, 110B and 110C,
the first and second fixing grooves 121 and 131 as well as the
mediating groove 111 are formed by an etching process using KOH
solution.
[0089] As described previously, preferably the second fixing groove
131 for receiving the laser diode chip 130 is so shaped that its
base width coincides with that of the bottom surface of the laser
diode chip 130 in the etching step.
[0090] Further, as the inner side walls of the second fixing groove
is inclined at a definite angle, enabled by the anisotropic
property of silicon, favorably for receiving a chip, a precise
mounting of the laser diode chip 130 is realized even with a usual
die bonder. (Refer to FIG. 11).
[0091] Now, a mere placing of the optical fiber 120 and the laser
diode chip 130 on the corresponding first and second fixing grooves
121 and 131 of the silicon substrate 110 means the completion of
the desired alignment of the optical fiber 120 and the laser diode
chip 130.
[0092] Therefore, the aligning method according to the present
invention eliminates the need for troublesome matching of the
alignment markers and the use of the expensive flip chip bonder in
the conventional art.
[0093] Moreover, the use of the laser diode chips 130 which were
clearly cut following etching step permits the precise mounting,
whether the epi-surface faces downward or upward.
[0094] C. Method for Aligning an Optical Receiving Module and an
Optical Receiving Module.
[0095] FIG. 12 shows a plan view illustrating a method for
automatically aligning and mounting the optical detector of an
optical receiving module for optical communication according to the
present invention. FIG. 13 shows a perspective view of the optical
receiving module according to the present invention.
[0096] Referring to FIGS. 12 and 13, the embodiment of optical
receiving module includes the first fixing groove 221 for mounting
an optical fiber on a silicon wafer 210, a mediating groove 211
which extends at the right angle to the first fixing groove and
which has its base surface positioned a little lower than the first
fixing groove, the second fixing groove 231 in a rectangular form
behind the mediating groove, with its base surface positioned a
little higher than the first fixing groove and a laser beam guiding
slot 232 which extends, at the right angle to the mediating groove
and in line with the first fixing groove 221, up to the central
area of the second fixing groove 231 and which has its base at
about the same elevation as the first fixing groove 221 and which
is gold-plated.
[0097] The numeral 240 stands for the gold-plated area through
metal patterning.
[0098] FIG. 12 and 13 illustrate the construction of consisting of
the second fixing groove 231 for seating the photodiode chip 230
and an additional laser beam guiding slot 232 for guiding the
incidence of the light emitting from the optical fiber 220 into the
photodiode chip 230.
[0099] The manufacture of such a structure needs two steps of at
first, etching the first fixing groove 221 for an optical fiber on
the silicon substrate 210 and next, etching the second fixing
groove 231 for receiving a photodiode chip 230.
[0100] In preparing such a silicon substrate, the photolithography
process with masks having desired patterns and the etching process
with KOH solution are employed.
[0101] As the light receiving window of a photodiode chip 230
usually has a diameter of 70-80 microns in size, the laser beam
guiding slot 232 for guiding the light from an optical fiber 220
should have its top width which is larger than the size of the
light receiving window.
[0102] As the masking material, the silicon nitride thin film
deposited through PECVD growth is used, and as the corresponding
etchant for silicon, potassium hydroxide solution is used. Because
the control on the groove size is most important in etching a V
type groove or slot, the concentration and temperature of the
etching solution and the stirring state of the solution should be
carefully regulated.
[0103] The metal layer 240 for mounting the photodiode chip 230 and
the optical fiber 220 on the silicon substrate 210 so prepared is
then vapor-deposited before those chip and fiber are mounted.
[0104] As in the former embodiments, it is possible to mount the
photodiode chip in an exact place with an ordinary die bonder
because the V type groove of the diode chip has the configuration
fitted to stably retain the diode chip, including the features of
tapering cross section for the bore with the inner side walls
inclined inwardly 54.7.degree. with the depth and the base of the
groove matching with the bottom surface of the laser diode
chip.
[0105] It is to be understood that, while the invention was
described with respect to some specific embodiments, the invention
is never restricted to those embodiments and a variety of
modifications and alterations would be possible to a man skilled in
the art by referring to the description or drawings presented here
and within the spirit of the invention and thus those modifications
or alterations are to fall within the scope of the invention, which
scope should be limited only by the attached claims.
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