Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal – Packaging or treatment of packaged semiconductor
Reexamination Certificate
2000-09-07
2001-07-03
Picardat, Kevin M. (Department: 2822)
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
Packaging or treatment of packaged semiconductor
C438S029000, C438S046000, C438S111000, C257S099000, C257S100000
Reexamination Certificate
active
06255129
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
The present invention relates to a light-emitting diode (LED) device and the method of manufacturing the same. More particularly, the present invention relates to an LED device, made of GaN-based compound semiconductor materials, whose sidewalls and bottom surface are both covered with a conductive layer, and the method of manufacturing the same.
B. Description of the Related Art
In recent years, the GaN-based compound semiconductor has received more and more attention to use of a material for manufacturing blue, green, blue-green light-emitting devices, such as blue LEDs or blue laser diodes (LDs). The blue LED, for example, generally has a structure including at least one n-type GaN-based compound semiconductor layer, an active layer made of an intrinsic or doped GaN-based compound semiconductor material, and at least one p-type GaN-based compound semiconductor layer, which are sequentially laminated on a substrate.
In manufacturing the conventional blue LED, transparent sapphire is usually used as a material of the substrate of the blue LED. Different from the semiconductor substrate used for other semiconductor light-emitting devices, sapphire is an electrically insulating material. Consequently, it is impossible to directly form the n-type electrode on the sapphire substrate. As a solution to this problem, the n-type GaN-based compound semiconductor layer is partially exposed by means of etching the blue LED so as to provide a conductive surface where an n-type electrode is effectively to be formed.
Referring to
FIG. 1
for a more specific understanding of the conventional blue LED described above, the conventional blue LED mainly includes a sapphire substrate
101
, an n-type GaN-based compound semiconductor layer
102
, an active layer
103
made of an intrinsic or doped GaN-based compound semiconductor material, and a p-type GaN-based compound semiconductor layer
104
. As described above, an n-type electrode
105
is formed on the exposed surface of the n-type GaN-based compound semiconductor layer
102
, while a p-type electrode
106
is formed on the p-type GaN-based compound semiconductor layer
104
.
The conventional blue LED shown in
FIG. 1
, however, has several disadvantages as described in the following. First of all, the insulating sapphire substrate
101
of the blue LED fails to form an electrical connection with a cup-type lead frame
107
when mounted on the surface of the cup-type lead frame
107
. In order to electrically connect the blue LED with the cup-type lead frame
107
, it is necessary to use a metal bonding wire
108
for electrically bonding the n-type electrode
105
to the surface of the cup-type lead frame
107
, as shown in FIG.
2
. Since another metal bonding wire
109
needs to electrically bond the p-type electrode
106
. to a separate lead frame
110
, the wire bonding process must be performed twice for completely bonding the conventional blue LED. In addition, the metal bonding wire
109
is bonded on the p-type electrode
106
preferably through a bonding pad
111
. As a result of the two-wire-bonding characteristic, the complication of the conventional process of manufacturing the blue LED and the die size of the blue LED are both greatly increased, which result in a high fabrication cost.
Moreover, the structure and arrangement of the electrodes
105
,
106
of the conventional blue LED is asymmetric as shown in
FIG. 3
, which is the top view of the blue LED shown in FIG.
1
. As a result, the electric current in the conventional blue LED does not flow in a symmetric and top-down direction. Therefore, it is very difficult for the conventional blue LED to achieve a uniform A current spreading characteristic. Since the current spreading characteristic is non-uniform, several high current density points exist in the conventional blue LED, which are easily damaged during the operation.
Furthermore, the well-known electrostatic discharge (ESD) problem inevitably occurs in the insulating sapphire substrate
101
. The above-mentioned disadvantages greatly reduce the performance and reliability of the conventional blue LED.
Accordingly, it is desirable to provide a blue LED that achieves a one-wire-bonding characteristic without greatly increasing the complication of the manufacturing process and the fabrication cost. It is also desirable to provide a blue LED that achieves a uniform current spreading characteristic and is free from the ESD problem. Furthermore, it is desirable to provide a blue LED provided with a mirror-like reflector formed on its bottom surface, thereby increasing the light-emitting efficiency of the blue LED.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a light-emitting diode device which achieves a one-wire-bonding characteristic. The complication of the manufacturing process is thus simplified and the fabrication cost is reduced.
Another object of the present invention is to provide a light-emitting diode device with a uniform current spreading characteristic.
Still another object of the present invention is to provide a light-emitting diode device which is free from the electrostatic discharge (ESD) problem.
Yet still another object of the present invention is to provide a light-emitting diode device with a mirror-like reflector formed on the bottom surface.
According to a first aspect of the present invention, a light-emitting diode device comprises: an insulating substrate; a laminated semiconductor structure having a first GaN-based semiconductor layer formed on the top surface of the insulating substrate; an active layer formed over the first GaN-based semiconductor layer for generating light; and a second GaN-based semiconductor layer formed over the active layer, wherein an annular trench is formed to separate the second GaN-based semiconductor layer into a central second GaN-based semiconductor layer and a peripheral second GaN-based semiconductor layer and to separate the active layer into a central active layer and a peripheral active layer; a first electrode formed on the central second GaN-based semiconductor layer without electrically connecting to the peripheral second GaN-based semiconductor layer; and a conductive layer coated to cover the sidewalls and the bottom surface of the insulating substrate and to ohmically contact with the first GaN-based semiconductor layer.
The method of manufacturing the light-emitting diode device according to the first aspect of the present invention comprises: preparing an insulating substrate; forming a first GaN-based semiconductor layer on the insulating substrate; forming an active layer over the first GaN-based semiconductor layer for generating light; forming a second GaN-based semiconductor layer over the active layer; forming an annular trench to separate the second GaN-based semiconductor layer into a central second GaN-based semiconductor layer and a peripheral second GaN-based semiconductor layer and to separate the active layer into a central active layer and a peripheral active layer; forming a first electrode on the central second GaN-based semiconductor layer without electrically connecting to the peripheral second GaN-based semiconductor layer; and coating a conductive layer to cover the sidewalls and the bottom surface of the insulating substrate and to ohmically contact with the first GaN-based semiconductor layer.
According to a second aspect of the present invention, an adhesion layer is formed on the sidewalls and the bottom surface of the insulating substrate, which is followed by forming the conductive layer over the adhesion layer. The adhesion layer is used to enhance the adhesive property between the insulating substrate and the conductive layer.
According to a third aspect of the present invention, the conductive layer is a light-transmissive layer. As the light-transmissive conductive layer, an indium-tin-oxide layer, a cadmium-tin-oxide layer, a zinc oxide layer, or a thin metal layer, with a thickness in the range from 0.001 &mgr;m to 1 &mgr;m, made o
Highlink Technology Corporation
Martine & Penilla LLP
Picardat Kevin M.
LandOfFree
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