Semiconductor device manufacturing: process – Bonding of plural semiconductor substrates – Subsequent separation into plural bodies
Reexamination Certificate
1999-05-10
2001-07-10
Lee, Eddie C. (Department: 2815)
Semiconductor device manufacturing: process
Bonding of plural semiconductor substrates
Subsequent separation into plural bodies
C438S455000, C438S125000, C438S046000, C438S026000, C414S935000, C206S710000
Reexamination Certificate
active
06258699
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a light emitting diode with a permanent substrate of transparent glass or quartz and the method for manufacturing the same.
BACKGROUND OF INVENTION
The trend of current light emitting diode of visible light is that the intensity of illumination of light emitting diode is more and more stronger, while the volume is more and more compact.
U.S. Pat. Nos. 5,008,718 and 5,233,204 disclosed a light emitting diode with a transparent window layer. By this kind of light emitting diode, the crowding effect occurring in the conventional light emitting diode is reduced, wherein the current spread to emit light from the light emitting diode is increased. As a result, the illumination of the light emitting diode is apparently enhanced.
Moreover, U.S. Pat. No. 5,237,581 and No. 4,570,172 disclosed a light emitting diode having a semiconductor multilayer reflector, namely, DBR (distributed Bragg Reflector). By this light emitting diode, the light transmitting to the substrate is reflected backwards so as to penetrate through the light emitting diode. Accordingly, the light illumination of the light emitting diode is increased.
A cross sectional view of a conventional light emitting diode is illustrated in FIG.
1
. The light emitting diode
100
includes a semiconductor substrate
102
, a second ohmic contact electrode
101
formed on the rear side of the semiconductor substrate
102
, a light generating region
103
formed on the semiconductor substrate
102
, and a first ohmic contact electrode
106
formed on the light generating region
103
. Because of the current crowding effect, critical angle of the emitting light and light absorption of the substrate, the illumination in this light emitting diode is not suitable. The light generating region
103
is formed by a P type region and an N type region, and then the light generating region
103
is grown on the gallium arsenide substrate
102
. Therefore, the crystal lattice constants in most of the light generating region
103
are matched with that of the gallium arsenide substrate. Namely, the light emitting diode of visible light is directly fabricated on the gallium arsenide substrate
102
. However, since the energy gap of the gallium arsenide is 1.43 eV which is smaller than that of the visible light and the light emitted from the diode is non-isotropic, part of the light enters the substrate and is absorbed by the gallium arsenide. U.S. Pat. Nos. 5,008,718 and No. 5,233,204 disclosed a transparent window layer structure for increasing the output light of a light emitting diode. Referring to
FIG. 2
, the structure of the light emitting diode
200
is formed by a transparent window layer
204
is grown on the light emitting diode
100
shown in FIG.
1
. The proper material suitable for the transparent window layer
204
includes GaP, GaAsP, and AlGaAs, etc., whose energy gap is larger than those of the materials in the AlGaInP light generating region. Under this condition, the optic critic angle can be increased and the current crowding effect is reduced so as to enhance the illumination of the light emitting diode. However, in the electric property, since the materials on the uppermost layer of the transparent window layer
204
and the AlGaInP light generating region have a hetero junction, the energy gap difference causes the positive foward bias voltage V
f
of the light emitting diode to increase. As a result, the power loss of using the light emitting diode is increased.
The U.S. Pat. Nos. 5.237,581 and 4,570,172 disclosed a light emitting diode
300
with a multilayer reflecting structure, as shown in FIG.
3
. The structure of
FIG. 3
includes a semiconductor substrate
302
, a lower multilayer reflector
305
formed on the semiconductor substrate
302
, a light generating region
303
formed on the lower multilayer reflector
305
, an upper multilayer reflector
304
formed on the light generating region
303
, a first ohmic contact electrode
306
on the upper multilayer reflector
304
, and a second ohmic contact electrode
301
on the rear side of the semiconductor substrate
302
. In this prior art light emitting diode, the lower multilayer reflector
305
serves to reflect 90% of the light emitted from the light generating region to the light absorption substrate, while the upper multilayer reflector serves to guide light to the upper surface of the light emitting diode. Therefore, the problem of light absorption by the substrate is improved, and the problem of bad illumination from enlarging the critical angle is also improved. However, since the multilayer reflector has many hetero junctions, the effect of energy gap difference is enlarged. As a consequence, although the aforesaid DBR structure disclosed in U.S. Pat. Nos. 5.237,581 and 4,570,172 can reflect the light impinging on the substrate by the DBR structure, the DBR has a high reflective index only for normal incident light (shown in D
1
of FIG.
3
), while for oblique incident light (such as D
2
, D
3
, and D
4
shown in
FIG. 3
) the reflective index is very small. Thus it is only a slight improvement to the illumination of a light emitting diode in the visible light band. Whereas the DBR structure increase the cost and difficulty of growing the thin film epitaxial layer. U.S. Pat. No. 5,376,580 disclosed a light emitting diode with wafer bonding, wherein a gallium arsenide substrate serves as a temporary substrate to grow a light emitting diode structure (including a confinement layer, an active layer and another confinement layer). Then the light emitting diode structure is adhered to a transparent substrate, and the GaAs substrate is removed. Therefore, the light absorption by the substrate can be solved completely. Whereas the transparent substrate disclosed in the aforementioned U.S. Pat. No. 5,376,580 is made by GaP which is very expensive and has an orange color. The light from LED to the substrate has a slight color. Further, in high temperature, the GaP as a transparent substrate needs to be processed for a long period of time (about 600~700° C. for at least one hour), this results in a bad effect to the p-n junction of LED.
SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to provide a method for manufacturing a light emitting diode with a permanent substrate of transparent glass or quartz. Transparent glass or quartz is used as a permanent substrate, and metal is employed as a bonding agent. An LED element is adhered to the transparent glass. After being adhered, an etching agent serves to remove the GaAs substrate. Therefore, the problem of light absorption by the substrate is improved, and the problem of the p-n junction being affected by temperature is resolved completely. The illumination is doubled.
Another object of the present invention is to provide a light emitting diode with a permanent substrate of transparent glass or quartz. The light emitting region of the light emitting diode with a permanent substrate of transparent glass or quartz is a conventional light emitting region structure. For example, it may be light emitting region of dual hetero structures with an upper cladding layer/an active layer/a lower cladding layer, a light emitting region of a single hetero structure, or a light emitting structure of a homostructure. The permanent substrate of transparent glass of the present invention can be applied to all kinds of conventional light emitting region and thus it has wide applications.
A further object of the present invention is to provide a method for manufacturing a light emitting diode with a permanent substrate of transparent glass or quartz comprising the steps of selecting a temporary substrate so as to grow an LED light emitting region on the temporary substrate for forming an LED element; selecting a permanent substrate, and adhering the LED element to the permanent substrate by a metal bonding agent; removing the temporary substrate adhered by the permanent substrate/LED element by mechanic grinding or chemical etching; manufacturing a pl
Chang Kuo-Hsiung
Chen Lung-Chien
Horng Ray-Hua
Huang Man-Fang
Lin Kun-Chuan
Lee Eddie C.
Richards N. Drew
Visual Photonics Epitaxy Co., Ltd.
LandOfFree
Light emitting diode with a permanent subtrate of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Light emitting diode with a permanent subtrate of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Light emitting diode with a permanent subtrate of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2493015