Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal – Packaging or treatment of packaged semiconductor
Reexamination Certificate
2000-06-23
2002-01-01
Christianson, Keith (Department: 2813)
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
Packaging or treatment of packaged semiconductor
Reexamination Certificate
active
06335212
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor light-emitting device and a method of manufacturing said same device, and more particularly to a method of fabricating a semiconductor light-emitting element containing a nitride of a Group III element (hereinafter referred to as a “Group-III nitride compound semiconductor light-emitting element”).
2. Description of the Related Art
FIG. 1
is a schematic view illustrating an exemplary structure of a light-emitting diode
200
which is subjected to heat treatment according to the present invention. As shown in
FIG. 1
, a wire-bonding-type semiconductor light-emitting element
100
mounts onto an upper flat portion
203
of a lead
201
. A negative electrode
140
connects to the lead
201
by means of a wire
204
. A thick-film positive electrode
120
serving as an electrode pad for wire bonding connects to a lead
202
by means of a wire
205
. Subsequently, a body that functions as a lens is formed from an insulating resin
206
such as epoxy resin through, for example, a potting process.
FIG. 2
is a schematic cross section of the semiconductor light-emitting element
100
. Reference numeral
101
denotes a sapphire substrate;
102
denotes an aluminum nitride (AlN) buffer layer;
103
denotes an n-type gallium nitride (GaN) layer;
104
denotes an n-type (GaN) cladding layer;
105
denotes a light-emitting layer;
106
denotes a p-type aluminum gallium nitride AlGaN cladding layer;
107
denotes a p-type GaN contact layer;
110
denotes a thin-film positive electrode for dispersing current into the contact layer
107
within a wide region;
120
denotes a thick-film positive electrode serving as an electrode pad for wire bonding;
130
denotes a protective film layer; and
140
denotes a negative electrode.
The protective film layer
130
is formed from oxide film such as SiO
x
nitride film such as SiN
x
so that the protective film layer
130
has light-transmission capability and insulation capability.
After the completion of the wire bonding process, the light-emitting element
100
is sealed by the insulating resin
206
such as epoxy resin from the upper side (the protective film layer
130
side) thereof such that the protective film layer
130
and the exposed surfaces of the electrodes
120
and
140
are covered by the insulating resin
206
. Then, the insulating resin
206
is hardened at a temperature of one hundred and several tens of degrees centigrade.
When the light-emitting diode
200
is allowed to return to room temperature after the hardening of the insulating resin
206
such as epoxy resin, thermal shrinkage of the insulating resin
206
causes stresses to act on the light-emitting element
100
. Once these stresses are formed, they remain within the insulating resin
206
. When a high-load durability test (a drive test performed at a high temperature, a high humidity, and a large current for an extended period of time) is performed on the light-emitting element
100
that contains such stresses, additional stresses are generated due to a temperature gradient generated inside the light-emitting element
100
. These additional stresses act, especially, on the protective film layer
130
as well as on the thin-film positive electrode
110
and the like via the protective film layer
130
.
The temperature gradient is generated, because the p-type GaN contact layer
107
contains both a high current-density portion and a low current-density portion (see FIG.
2
). The p-type GaN contact layer
107
contains a portion that is located directly under the thin-film positive electrode
110
which has a high current density. In addition, another portion, such as a stepped portion S, which is not covered with the thin-film positive electrode
110
possesses a very low current density.
The above-described stresses raise no problem under ordinary fabrication conditions or ordinary conditions of use. However, when the light-emitting diode
200
is subjected to severe conditions; for example, when the hardening temperature of the insulating resin
206
is set to 200° C. or higher with the resultant generation of excessively large residual stresses, or when the light-emitting diode
200
is subjected to a high-load durability test requiring an extended period of time; the state of the contact surface of the protective film layer
130
in contact with the thin-film positive electrode
110
changes partially, resulting in a possibility of the light-emission characteristics being affected.
Accordingly, in order to secure reliably the light-emitting element
100
under such severe conditions, there have been demands to improve the quality of materials and to properly set (regulate) potting conditions, hardening conditions, and other conditions.
SUMMARY OF THE INVENTION
The invention overcoming these and other problems in the art relates to a device and a method of manufacturing a semiconductor light-emitting element possessing enhanced durability and reliability.
An object of the present invention is to provide a method of fabricating a reliable semiconductor light-emitting element in which the qualities of a protective film layer, a thin-film positive electrode, and other elements remain high even under severe conditions.
Another object of the present invention is to provide a method of fabricating a reliable semiconductor light-emitting element which includes stacked layers of compound semiconductors, electrodes, and a transparent, insulative protection layer. The stacked layers of compounds are sealed with an insulating resin.
In order to achieve the above object, the present invention provides a method of fabricating a semiconductor light-emitting element in which a semiconductor light-emitting element having an electrode and a protective film layer is sealed with an insulating resin. Next, the insulating resin is hardened at high temperature. Then, the semiconductor light-emitting element is heat-treated in an atmosphere of normal or higher humidity.
The heat treatment is preferably performed at a temperature of 60° C. or higher.
The atmosphere preferably has an absolute humidity of not less than 10 KPa, more preferably not less than 50 KPa.
The heat treatment is preferably performed at a pressure of 1 atm or higher.
When the method of the present invention is employed, the insulating resin absorbs moisture during the heat treatment performed after the hardening thereof, so that stresses remaining in the interior surface or on the exterior surface of the light-emitting element are relaxed greatly due to the absorption of moisture.
By virtue of the relaxation of residual stresses, even when the semiconductor light-emitting element is subjected to a high load durability test, which simulates use under severe conditions, the insulating resin
206
, the protective film layer
130
, the thin-film positive electrode
110
, and other components remain unaffected, so that stable light-emission characteristics can be obtained.
Further, the above effect greatly eases the restrictions on the material quality and the potting conditions. As a result, the productivity, as compared with conventional methods, is greatly improved.
When the heat treatment is performed at a temperature of 60° C. or higher or in a processing atmosphere having a high absolute humidity of not less than 10 KPa, remarkable effects are attained through a high degree of moisture-absorbing action. When the heat treatment temperature is set lower than 60° C., completing the heat treatment requires a greatly increased period of time, or obtaining sufficient effect of the heat treatment becomes difficult. Further, the absolute humidity of the heat treatment atmosphere is preferably not less than 10 KPa. When the absolute humidity is lower than 10 KPa, completing the heat treatment requires an increased period of time or obtaining sufficient effect of the heat treatment becomes difficult.
When the heat treatment is performed at a pressure not less than 1 atm, the moisture-absorbing action of the insulating res
Oshio Takahide
Uemura Toshiya
Christianson Keith
Pillsbury & Winthrop LLP
Toyoda Gosei Co,., Ltd.
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