Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – With housing or contact structure
Reexamination Certificate
1998-09-29
2001-12-25
Jackson, Jr., Jerome (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
With housing or contact structure
C257S081000, C257S091000, C257S098000
Reexamination Certificate
active
06333522
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a light-emitting element comprising a semiconductor multilayer film formed on an insulating substrate, to a semiconductor light-emitting device including such a semiconductor light-emitting element, and to manufacturing methods therefor. In particular, the present invention is properly applicable to a light-emitting element (LED) using a gallium-nitride-based compound semiconductor formed on a sapphire substrate and to a light-emitting device comprising such a light-emitting element.
BACKGROUND ART
As the demand for optical devices, such as liquid-crystal display devices, has grown in recent years, various light-emitting elements have found practical applications. Among them is a gallium-nitride-based compound semiconductor (In
x
Al
y
Ga
1−x−y
N, 0≦X, 0≦Y, X+Y≦1), which is not only on the current market as a high-intensity blue and green light-emitting diode (LED) but also receiving attention as a prospective material for composing a blue laser diode, a UV sensor, and a solar cell in the future.
FIG. 4A
is a plan view of a conventional GaN LED element which is commercially available.
FIG. 4B
is a cross-sectional view taken along the line B—B thereof.
FIG. 4C
is a cross-sectional view taken along the line C—C thereof. It is to be noted that the thickness of each semiconductor layer shown in the drawings does not necessarily coincide with the actual thickness thereof.
FIG. 5
is a cross-sectional view of a conventional LED lamp which is commercially available. The GaN LED element
40
has a double heterostructure including a GaN buffer layer
31
, an n-type GaN layer
32
, an InGaN active layer
33
, a p-type AlGaN layer
34
, and a p-type GaN layer
35
which are stacked sequentially in layers on the top face of a sapphire substrate
30
. The top face of the n-type GaN layer
32
has a stepped configuration consisting of an upper-level portion and a lower-level portion. An n-side electrode
36
made of Ti and Au is formed on the top face of the lower-level portion of the n-type GaN layer
32
. The aforesaid InGaN active layers
33
, the p-type AlGaN layer
34
, and the p-type GaN layer
35
are stacked sequentially in layers on the top face of the upper-level portion of the n-type GaN layer
32
. A transparent electrode
37
for current diffusion made of Ni and Au is formed on the top face of the p-type GaN layer
35
, followed by a p-side electrode
38
formed thereon. Since the GaN LED element
40
is formed by using the insulating sapphire substrate, each of the two electrodes is formed on the top face of the sapphire substrate. The top face of the GaN LED element
40
serves as a light-emitting face, which is coated with a protective film
39
except for the bonding pad portions
36
a
and
38
a
of the n-side and p-side electrodes
36
and
38
. The GaN LED element
40
is die-bonded to a die pad on the tip of a leadframe
44
a
via an insulating adhesive
43
. The n-side electrode
36
of the GaN LED element
40
is connected to the leadframe
44
a
via an Au wire
41
, while the p-side electrode
38
thereof is connected to a leadframe
44
b
via an Au wire
42
. The respective tip portions of the leadframes
44
a
and
44
b
carrying the GaN LED element
40
are molded with a transparent epoxy resin
45
to constitute the LED lamp.
The foregoing conventional light-emitting element has the following problems.
To achieve wire bonding for providing an electrical connection between the GaN LED element
40
and another element or the like as described above, each of the bonding pad portions
36
a
and
38
a
should be configured as a circle having a diameter of 100 &mgr;m or more or a square having sides of 100 &mgr;m or more. Moreover, since the two electrodes
36
and
38
are formed on the light-emitting side, the light-emitting efficiency is degraded. If the bonding pad portions
36
a
and
38
a
are provided with a sufficiently large area and the light-emitting face is provided with a sufficiently large area for emitting a sufficient amount of light, the size reduction of the light-emitting element will be limited and the scaling down of the light-emitting element will be difficult.
It is therefore a primary object of the present invention to provide a semiconductor light-emitting element and a manufacturing method therefor, which enable a reduction in the area required by the electrodes to achieve electrical connection of the light-emitting element, the scaling down of the entire light-emitting element, and improvements in the brightness and light-emitting efficiency of the light-emitting element.
Another object of the present invention is to provide a light-emitting device comprising the aforesaid light-emitting element and a manufacturing method therefor.
DISCLOSURE OF INVENTION
A light-emitting element according to the present invention comprises: a substrate; a first-conductivity-type semiconductor region formed in the semiconductor substrate; a second-conductivity-type semiconductor region formed on a portion of the first-conductivity-type semiconductor region; a first electrode formed on a portion of the first-conductivity-type semiconductor region other than the portion in which the second-conductivity-type semiconductor region is formed; and a second electrode formed on the second-conductivity-type semiconductor region, the light-emitting element further comprising a plurality of microbumps made of a conductive material and formed on the first and second electrodes, wherein the number of the microbumps formed on the first electrode is one and the number of the microbumps formed on the second electrode is one or more.
Preferably, each of the microbumps has a columnar or mushroom-like configuration, a maximum lateral dimension ranging from 5 to 300 &mgr;m, and a height ranging from 5 to 50 &mgr;m.
Preferably, a metal layer having excellent adhesion to the first-conductivity-type or second-conductivity-type semiconductor region is provided under at least one of the first and second electrodes.
Another light-emitting element according to the present invention comprises: a substrate; a first-conductivity-type semiconductor region formed in the semiconductor substrate; a second-conductivity-type semiconductor region formed on a portion of the first-conductivity-type semiconductor region; a first electrode formed on a portion of the first-conductivity-type semiconductor region other than the portion in which the second-conductivity-type semiconductor region is formed; and a second electrode formed on the second-conductivity-type semiconductor region, the light-emitting element further comprising a plurality of microbumps made of a conductive material and formed on the first and second electrodes, each of the first and second electrodes having not only a region in which the microbump is formed but also a probe region to come into contact with a probe needle.
Preferably, the probe region of the first electrode is formed to extend over a part of a dicing street.
Still another light-emitting element according to the present invention comprises: a substrate; a first-conductivity-type semiconductor region formed in the semiconductor substrate; a second-conductivity-type semi-conductor region formed in a portion of the first-conductivity-type semiconductor region; a first electrode formed on a portion of the first-conductivity-type semiconductor region other than the portion in which the second-conductivity-type semiconductor region is formed; and a second electrode formed on the second-conductivity-type semiconductor region, the light-element further comprising a plurality of microbumps made of a conductive material and formed on the first and second electrodes, the second electrode including an opening for radiating light emitted from the light-emitting element to the outside.
Preferably, the opening formed in the second electrode is configured as a circle with a diameter of 20 &mgr;m or less or as a polygon included in a circle with a diameter of 20 &mgr;m or less.
A conductive transparent e
Fukuda Yasuhiko
Inoue Tomio
Koya Kenichi
Sanada Kenichi
Jackson, Jr. Jerome
Matsushita Electric - Industrial Co., Ltd.
Nixon & Peabody LLP
Robinson Eric J.
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