U.S. patent application number 11/684347 was filed with the patent office on 2007-06-28 for semiconductor component which emits radiation, and method for producing the same.
Invention is credited to Johannes Baur, Dominik Eisert, Volker Harle, Frank Kuhn, Norbert Linder, Manfred Mundbrod-Vangerow, Ernst Nirschl, Reinhard Sedlmeier, Uwe Strauss, Jacob Ulrich, Ulrich Zehnder.
Application Number | 20070145402 11/684347 |
Document ID | / |
Family ID | 26004340 |
Filed Date | 2007-06-28 |
United States Patent
Application |
20070145402 |
Kind Code |
A1 |
Eisert; Dominik ; et
al. |
June 28, 2007 |
SEMICONDUCTOR COMPONENT WHICH EMITS RADIATION, AND METHOD FOR
PRODUCING THE SAME
Abstract
This invention describes a radiation-emitting semiconductor
component with the a multilayered structure that contains a
radiation-emitting active layer, and a window transparent to
radiation that has a first principal face and a second principal
face opposite the first principal face, and whose first principal
face adjoins the multilayered structure. At least one recess is
made in the window, which preferably has the form of an indentation
of the second principal face or as an edge excavation. At least one
lateral surface of the window or of the recess is provided at least
partially with a contact surface. Alternatively or cumulatively, at
least one contact surface of the component has a plurality of
openings.
Inventors: |
Eisert; Dominik;
(Regensburg, DE) ; Harle; Volker; (Laaber, DE)
; Kuhn; Frank; (Munchen, DE) ; Mundbrod-Vangerow;
Manfred; (Oxen Bronn, DE) ; Strauss; Uwe; (Bad
Abbach, DE) ; Ulrich; Jacob; (Regensburg, DE)
; Nirschl; Ernst; (Wenzenbach, DE) ; Linder;
Norbert; (Wenzenbach, DE) ; Sedlmeier; Reinhard;
(Neutraubling, DE) ; Zehnder; Ulrich; (Regensburg,
DE) ; Baur; Johannes; (Deuerling, DE) |
Correspondence
Address: |
FISH & RICHARDSON PC
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Family ID: |
26004340 |
Appl. No.: |
11/684347 |
Filed: |
March 9, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10203728 |
Dec 2, 2002 |
7205578 |
|
|
PCT/DE01/00600 |
Feb 15, 2001 |
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11684347 |
Mar 9, 2007 |
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Current U.S.
Class: |
257/98 ; 257/95;
257/99; 257/E21.314; 257/E33.068; 257/E33.074 |
Current CPC
Class: |
H01L 33/0093 20200501;
H01L 33/20 20130101; H01L 33/42 20130101; H01L 21/32139 20130101;
H01L 33/46 20130101; H01L 33/32 20130101; H01L 33/40 20130101; H01L
33/382 20130101 |
Class at
Publication: |
257/098 ;
257/099; 257/095 |
International
Class: |
H01L 33/00 20060101
H01L033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 15, 2000 |
DE |
100 06 738.7 |
May 23, 2000 |
DE |
100 25 448.9 |
Claims
1. Radiation-emitting semiconductor component with a multilayered
structure that contains a radiation-emitting active layer, and a
window transparent to radiation that has a first principal face and
a second principal face opposite the first principal face, and
whose first principal face adjoins the multilayered structure, with
the window having at least one recess to form radiation-output
surfaces running at an angle to the first principal face,
characterized by the fact that at least one lateral face of the
window and/or of the recess adjoining the second principal face is
provided, at least in part, with a first contact surface.
2. Radiation-emitting semiconductor component pursuant to claim 1,
characterized by the fact that at least one of the contact surfaces
has a plurality of openings.
3. Radiation-emitting semiconductor component with a multilayered
structure that contains a radiation-emitting active layer, and a
window transparent to radiation that has a first principal face and
a second principal face opposite the first principal face and that
adjoins the multilayered structure, with the window having at least
one recess forming radiation-output surfaces at an angle to the
first principal face, characterized by the fact that the
multilayered structure is provided at least partially with a
contact surface that has a plurality of openings.
4. Radiation-emitting semiconductor component pursuant to claim 3,
characterized by the fact that the second principal face and/or at
least one lateral face of the window and/or of the recess adjoining
the second principal face is provided at least partially with
another contact surface.
5. Radiation-emitting semiconductor component pursuant to claim 4,
characterized by the fact that the other contact surface has a
plurality of openings.
6. Radiation-emitting semiconductor component with a multilayered
structure that contains a radiation-emitting active layer, and a
window transparent to radiation that has a first principal face and
a second principal face opposite the first principal face and whose
first principal face adjoins the multilayered structure, with the
window having at least one recess forming radiation-output surfaces
at an angle to the first principal face, characterized by the fact
that the second principal face is provided at least partially with
a contact surface that has a plurality of openings.
7. Radiation-emitting semiconductor component pursuant to claim 6,
characterized by the fact that the contact surface also covers at
least partially a lateral face of the window and/or of the recess
adjoining the second principal face.
8. Radiation-emitting semiconductor component pursuant to claim 6,
characterized by the fact that the multilayered structure is
provided at least partially with another contact surface.
9. Radiation-emitting semiconductor component pursuant to claim 8,
characterized by the fact that the other contact surface has a
plurality of openings.
10. Radiation-emitting semiconductor component pursuant to claim 2,
characterized by the fact that at last some of the openings are
circular, square, rectangular, hexagonal, or in the form of crossed
slits.
11. Radiation-emitting semiconductor component pursuant to claim 2,
characterized by the fact that the openings are arranged regularly,
at least in subregions of the contact surfaces.
12. Radiation-emitting semiconductor component pursuant to claim 2,
characterized by the fact that the openings consist of crossed
slits and are arranged at least in subregions of the contact
surfaces with maximum packing density, with the distance between
the openings being no smaller than the arm width of the crossed
slits.
13. Radiation-emitting semiconductor component pursuant to claim 1,
characterized by the fact that the second principal face of the
window has a plurality of indentations.
14. Method for manufacturing a radiation-emitting semiconductor
component with a multilayered structure that contains a
radiation-emitting active layer, and a window transparent to
radiation that has a first principal face and a second principal
face opposite the first principal face, and whose first principal
face adjoins the multilayered structure, with at least one recess
being formed in the window and with at least one lateral surfaces
of the window and/or or the recess being provided at least
partially with a first contact surface, characterized by the steps
preparation of a window layer with a first principal face and a
second principal face opposite the first principal face application
of a semiconductor layer sequence to the first principal face of
the window layer structuring the window layer, with at least one
recess being produced in the second principal face production of a
contact surface on the side of the second principal face of the
window layer, completion of the semiconductor component.
15. Method pursuant to claim 14, characterized by the fact that the
contact surface is contact metallization produced by vapor
deposition.
16. Method pursuant to claim 15, characterized by the fact that a
vapor-deposition source with a preferential direction is used for
vapor deposition, and the window layer to be subjected to vapor
deposition is positioned at an angle to this preferential
direction.
17. Method pursuant to claim 14, characterized by the fact that the
semiconductor layer sequence is applied epitaxially to the window
layer.
18. Method pursuant to claim 14,characterized by the fact that the
semiconductor layer sequence is applied to the window layer by a
wafer-bonding method.
19. Method pursuant to claim 14, characterized by the fact that the
process steps are carried out in the order 1. application of a
semiconductor layer sequence, 2. structuring of the second
principal face, 3. production of the contact surface.
20. Method pursuant to claim 14, characterized by the fact that the
process steps are carried out in the order 1. structuring of the
second principal face, 2. production of the contact surface, 3.
application of the semiconductor layer sequence.
21. Method pursuant to claim 14, characterized by the fact that the
process steps are carried out in the order 1. prestructuring of the
second principal face, 2. production of the contact surface, 3.
application of the semiconductor layer sequence, 4. final
structuring of the second principal face.
22. Radiation-emitting semiconductor component with a multilayered
structure that contains a radiation-emitting active layer, and a
window transparent to radiation that is positioned exclusively on
the side of the multilayered structure facing away from a principal
direction of radiation of the semiconductor component and has at
least one lateral wall that has a lateral wall section that is
inclined, concave, or stepped relative to a mid-axis of the
semiconductor body perpendicular to the multilayered structure,
which changes to a second lateral wall section perpendicular to the
multilayered structure, i.e. parallel to the mid-axis, in its
further extension toward the back when viewed from the multilayered
structure, with the part of the window encircling the second
lateral wall section constituting a mounting base for the
semiconductor component, characterized by the fact that the
multilayered structure is provided at least partially with a
contact surface that has a plurality of openings.
23. Radiation-emitting semiconductor component pursuant to claim
22, characterized by the fact that the window is made from the
epitaxy substrate used for the epitaxial growth of the multilayered
structure.
24. Radiation-emitting semiconductor component pursuant to claim
22, characterized by the fact that the refractive index of the
material of the window is greater than the refractive index of the
material of the multilayered structure, particularly of the active
layer.
25. Radiation-emitting semiconductor component pursuant to claims
22, characterized by the fact that the window consists of silicon
carbide or is based on silicon carbide, and the multilayered
sequence is made of semiconductor materials based on nitride.
26. Radiation-emitting semiconductor component pursuant to claim
25, characterized by the fact that the multilayered sequence is
made of material based on gallium nitride.
27. Radiation-emitting semiconductor component pursuant to claim
26, characterized by the fact that the multilayered sequence
contains at least one of the compounds Al.sub.1-xGa.sub.xN,
0.ltoreq.x.ltoreq.1, In.sub.1-xGa.sub.xN, 0.ltoreq.x.ltoreq.1,
In.sub.1-xAl.sub.xN, 0.ltoreq.x.ltoreq.1, and
Al.sub.1-x-yIn.sub.xGa.sub.yN, 0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1.
28. Radiation-emitting semiconductor component pursuant to claim
22, characterized by the fact that all of the lateral faces of the
window have a first lateral wall section and a second lateral wall
section.
29. Radiation-emitting semiconductor component pursuant to claim
22, characterized by the fact that the first lateral wall section
is a planar inclined surface that makes an angle with the mid-axis
that is between 20.degree. and 30.degree. inclusive.
30. Radiation-emitting semiconductor component pursuant to claim
25, characterized by the fact that the semiconductor component has
a square lateral cross section, all four lateral flanks of the
window have a planar inclined first lateral wall section, with the
ratio of the edge length of the multilayered structure to the edge
length of the mounting base being between 1.5 and 2 inclusive, and
with special preference being 1.35.
31. Radiation-emitting semiconductor component pursuant to claim
22, characterized by the fact that at least the first lateral wall
section is roughened.
32. Radiation-emitting semiconductor component pursuant to claim
22, characterized by the fact that the openings are circular,
square, rectangular, hexagonal, or in the form of crossed
slits.
33. Radiation-emitting semiconductor component pursuant to claim
22, characterized by the fact that the openings are arranged
regularly at least in subregions of the contact surface.
34. Radiation-emitting semiconductor component pursuant to claim
22, characterized by the fact that the openings are crossed slits,
and are arranged with maximum packing density at least in
subregions of the contact surfaces, with the distance between the
openings being no smaller than the arm width of the crossed
slits.
35. Radiation-emitting semiconductor component pursuant to claim
22, characterized by the fact that the contact surface is made as a
reflective contact metallization.
36. Radiation-emitting semiconductor component pursuant to claim
22, characterized by the fact that the contact surface is
transparent to radiation.
37. Radiation-emitting semiconductor component pursuant to claim
22, characterized by the fact that the contact surfaces contain
silver, gold, nickel, preferably platinum or palladium, or an alloy
of these metals.
38. Radiation-emitting semiconductor component pursuant to claim
22, characterized by the fact that the contact surfaces have a
thickness between 5 nm and 200 nm, preferably between 10 nm and 100
nm.
39. Radiation-emitting optical component with a radiation-emitting
semiconductor component pursuant to claim 22, characterized by the
fact that the optical component has a reflector trough with
inclined or parabolic lateral walls in which the semiconductor
component is mounted so that the window layer faces the bottom of
the reflector trough.
40. Radiation-emitting optical component pursuant to claim 39,
characterized by the fact that the lateral walls of the reflector
trough are coated with material that increases reflection.
41. Radiation-emitting optical component pursuant to claim 39,
characterized by the fact that the lateral walls of the reflector
trough are designed so that the radiation emitted from the
semiconductor component toward the back is reflected upward from
the inclined lateral walls in one and the same direction to the
greatest possible extent to the active layer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Pursuant to 35 U.S.C. .sctn. 120, this application is a
divisional application of U.S. application Ser. No. 10/203,728,
filed on Aug. 12, 2002, which is the U.S. National Phase
application of WIPO Application No. PCT/DE01/00600, filed on Feb.
15, 2001, which claims the benefit of foreign priority applications
filed in Germany, Serial Nos. 100 06 738.7, filed on Feb. 15, 2000,
and 100 25 448.9, filed on May 23, 2000. The contents of the prior
applications are incorporated herein by reference in their
entirety
TECHNICAL FIELD
[0002] This invention relates to a radiation-emitting semiconductor
component.
BACKGROUND
[0003] The invention relates in particular to a radiation-emitting
semiconductor component with a nitride-based active multilayered
structure applied to a silicon carbide-based epitaxial
substrate.
[0004] Radiation-emitting semiconductor components of the kind
mentioned usually have a semiconductor multilayered structure with
an active radiation-generating layer that is applied to a carrier
transparent to radiation. The radiation is output through the
carrier. In this arrangement, however, the radiation yield is
sharply reduced by total reflection of the produced radiation at
the carrier surface.
[0005] With block-shaped or cuboid carriers the fraction of totally
reflected radiation that cannot be output is especially high
because of the orthogonal arrangement of lateral faces and
principal faces of the carrier. The radiation yield can be
increased by forming recesses in the carrier whose lateral faces
are preferably inclined relative to the principal faces of the
carrier.
[0006] A form such as that specified in the priority-determining
patent application DE 25 100 067 38.7 is especially beneficial. The
contents of this patent application are explicitly incorporated in
the contents of the present patent application.
[0007] A corresponding component is shown schematically in FIG. 17.
The semiconductor component shown has a window 151 transparent to
radiation, to which is applied a radiation-producing multilayered
structure 152. At least one lateral face of the window 151 is
configured so that a first subregion 154 is inclined, concave, or
stepped relative to the normal to the multilayered structure 152,
which is adjoined by a second region 155 positioned parallel to the
normal to the multilayered structure. There are also two contact
surfaces 153a, b on the multilayered structure 152 on the one hand
and on the face of the semiconductor component facing away from the
multilayered structure 152 on the other hand.
SUMMARY
[0008] It is the purpose of this invention to provide a
radiation-emitting semiconductor component with improved
efficiency. It is also the purpose of the invention to develop a
method for manufacturing it. Finally, it is a purpose of the
invention to develop a corresponding optical component.
[0009] The invention proceeds from the assumption that the ratio of
output radiation power to the electrical power to be supplied for
it is critical for the degree of efficiency. The optical output
power depends on the degree of output, along with the current
flowing through the component. The degree of output indicates how
large is the fraction of output radiation relative to the total
radiation produced. The electrical power is determined by the
current flowing and the series resistance of the component. The
degree of efficiency can therefore be increased in particular by
lowering the series resistance and by increasing the degree of
output.
[0010] According to the invention, a first form of embodiment
provides for forming a radiation-emitting semiconductor component
with a multilayered structure, an active layer that generates
radiation within the multilayered structure, and a window
transparent to radiation with a first principal face and a second
principal face opposite the first principal face, with at least one
recess being formed in the window to constitute inclined radiation
output faces, and at least one lateral surface of the window and/or
of the recess being provided with a contact surface. The contact
surface preferably also extends over the second principal face of
the window or subregions thereof.
[0011] The current path from the contact surface to the active
layer is shortened on the average by this arrangement of the
contact surface, and thus beneficially reduces the series
resistance of the component.
[0012] The recess in the invention serves to increase the radiation
yield. Either direct output or reflection in a direction favoring
output is produced in particular by lateral faces that are inclined
relative to the principal faces of the window. A recess in the
window means both an indentation in the second principal face of
the window or removal of material from an edge of the window, as
shown for example in FIG. 15. When material is removed from the
edge, the lateral surfaces of the window and of the recess
partially coincide.
[0013] A second contact surface on the multilayered structure is
preferably provided for in the invention. This provides for current
being fed in close to the active layer within the multilayered
structure. It is especially advantageous for this contact surface
to be largely transparent to radiation, so that radiation output is
also possible through the second contact surface. This can be
achieved, for example, by appropriately thin metallization or
suitable transparent, electrically conductive films.
[0014] In a preferred refinement of the invention, the first
contact surface is a reflector. Because of this, the portions of
the radiation that strike the contact surface from inside the
window are not absorbed, but are reflected back, so that subsequent
output is possible. Thus a contact surface that is transparent to
radiation and one that is reflective contribute to increasing the
radiation yield, since they assist the output of radiation either
directly or indirectly.
[0015] A second embodiment of the invention provides forming a
radiation-emitting semiconductor component with a multilayered
structure, an active layer within the multilayered structure
serving to generate radiation, and a window transparent to
radiation, with a first principal face and a second principal face
opposite the first principal face, with at least one recess being
formed in the window to form an inclined radiation output surface.
The component here has at least one contact surface with a
plurality of openings.
[0016] It is preferred for at least one of the window surfaces to
be provided, at least in part, with a first contact surface and for
the multilayered structure to be provided, at least in part, with a
second contact surface, with at least one of the contact surfaces
having a plurality of openings.
[0017] It is advantageous also for a plurality of openings to be
formed in each of the two contact surfaces.
[0018] These contact surfaces transparent to radiation, called
perforated contact surfaces below, have the advantage over thin
contact surfaces transparent to radiation, of higher long-term
stability, particularly in a casting composition, for example such
as epoxy resin. These perforated contact surfaces can also be made
so that they have high transmission in the area of the openings and
high reflection in the areas coated with contact material, so that
absorption and therefore radiation loss is slight on these contact
surfaces.
[0019] Perforated contact surfaces on the multilayered structure
also have the advantage that they do not seal off the multilayered
structure, so that for example gases such as hydrogen that reach
the multilayered structure during manufacture can diffuse out of
it. This also reduces the risk of such gases aggregating at the
interface between the multilayered structure and the contact
surface, passivating the contact surface, and thus increasing
contact resistance and series resistance.
[0020] The openings in the contact surface(s) are preferably
circular, square, rectangular, hexagonal, or in the shape of
crossed slits. These forms are especially suitable for a regular
arrangement and are comparatively easy to make technically. The
openings are preferably packed tightly provided that the
intermediate areas of the contact surfaces form a continuous
network and the width of the areas meet the requirements for
current input into the component. Of course the shapes mentioned do
not constitute a limitation of the invention thereto.
[0021] In an advantageous configuration of the invention in both
forms of embodiment, the recess is made in the form of an
indentation in the second principal face of the window. It is
beneficial that no change of the basic window enveloping shape is
necessary, so that in particular production systems, which are
often designed for a given basic window shape, can continue to be
used without change. A plurality of indentations can also be made
in the second principal face, whereby the radiation yield is
further increased. This configuration is advantageous especially
for large-area semiconductor components, since the ratio of area to
circumference rises with increasing chip area, and thus more
indentations can be placed in the surface than
circumferentially.
[0022] In a preferred refinement of the invention, the indentation
in the second principal face is designed with a triangular,
trapezoidal, or semicircular cross section (section perpendicular
to the second principal face). The cross section can also have the
shape of a rectangle with added triangle, trapezoid, or semicircle.
In general the formation of recesses with at least one lateral face
not in an orthogonal position to the principal faces is
advantageous.
[0023] Depending on the specific form of embodiment, the angle of
incidence of the radiation produced relative to the normal to the
lateral faces, and thus the fraction of totally reflected
radiation, is thereby lowered, or reflection toward the flanks of
the window is brought about, so that direct output or at least
output after further reflections can take place. The latter applies
in particular to the lateral faces of the indentation that are
provided with a reflective contact surface.
[0024] The indentation in the second principal face of the window
is preferably in the form of a trough with one of the
aforementioned cross-sectional shapes. Such an indentation can be
made, for example, by sawing into the window from the second
principal face and using a saw blade with shaped rim. If this
sawing is performed in the wafer composite, then a plurality of
windows can advantageously be structured in one production
step.
[0025] Alternatively, the indentations can also be etched in place.
In this form of embodiment in particular, spatially isolated
indentation shapes bordered all around can be formed. The
structuring of a plurality of windows in the wafer composite in one
production step is also advantageously possible here.
[0026] In an especially preferred refinement of the invention, the
recess that increases radiation yield is formed at the edge of the
second principal face and is so shaped that the window is tapered
down toward the second principal face. It is preferred for the
recess to be made so that the lateral faces of the recess have a
first subregion inclined relative to the normal to the multilayered
structure in the vicinity of the multilayered structure, that
changes at greater distance from the multilayered structure to a
second subregion running parallel to the normal to the multilayered
structure.
[0027] The window is preferably formed as a parallelepiped in the
section corresponding to the second region. It is advantageous that
the radiation yield is increased by the inclined subregion, while
the remaining area of the window has a square basic shape and thus
can easily be mounted. In this case in particular, the lateral
faces [of] the second subregion are provided with a contact
surface. The contact surface can also extend over the first
subregion of the lateral faces, and can then preferably be made
reflective, so that the radiation yield toward the multilayered
structure is increased by reflection of the radiation produced.
[0028] The described structure can be formed advantageously at low
production cost, for example by sawing a wafer with a saw blade
with shaped edge to isolate the semiconductor bodies, and then
singling the semiconductor bodies by breaking the wafer. Prior
sawing of the wafer is desirable to facilitate singling by
breaking. The described window shape can be excavated at the same
time by using a suitable saw blade with shaped edge. Other
advantageous configurations in this regard are specified in DE 100
067 38.7, to which this invention refers in particular.
[0029] A manufacturing method pursuant to the invention begins with
preparation of a window layer, from which the actual window will
later be produced.
[0030] A semiconductor layer sequence corresponding to the
multilayered structure is applied to the window layer. It is
preferably applied epitaxially or in the context of a wafer-bonding
procedure. In epitaxy, the window layer at the same time
advantageously represents the epitaxy substrate. In a wafer-bonding
procedure, the semiconductor layer sequence is produced first on a
suitable substrate, and is then bonded to the window layer.
Materials that are unsuitable for an epitaxial process can also
advantageously be used here as window material.
[0031] In another step the window layer is structured to develop
the recess in a suitable manner. Structuring can be accomplished,
for example as described, by sawing or etching the window layer.
Structuring can also be performed in multiple steps, not
necessarily in succession. Thus, with regard to the mechanical
breakage stability of the window layer, it is advantageous to first
prestructure the window layer and to perform the final structuring
only at a later stage of the production process.
[0032] In a further step the contact surfaces are applied to the
window layer. The contact surfaces are preferably vapor-deposited
or sputtered on for contact metallization.
[0033] Finally, the semiconductor components are completed. This
includes in particular the singling of the composite of window
layer and semiconductor layer sequence into a plurality of windows
with multilayered structure located thereon. The singling is
performed preferably by sawing and/or breaking the window layer.
Additional contact surfaces, for example contact metallizations,
can also be applied to the multilayered structure in the course of
completion.
[0034] To perform the contact metallization, vapor deposition
systems are ordinarily used, from which the metal vapor originates
with a given preferential direction. It is advantageous in this
case to arrange the surface of the window layer to be subjected to
vapor deposition at an angle to this preferential direction. In
this way, deposition of the metal vapor on the second principal
face of the window layer and also on the lateral faces of the
recesses formed by the structuring is achieved.
[0035] With regard to the sequence of the described manufacturing
steps, three alternatives described below are distinguished by
particular advantages:
[0036] In the first advantageous alternative, the semiconductor
layer sequence is first applied to the window layer, the window
layer is then structured, and finally it is subjected to vapor
deposition to develop the contact surfaces. Especially in case of
epitaxial production of the semiconductor layer sequence, existing
production equipment can be used for this without changes, since
with epitaxy the window layer does not yet differ from window
layers pursuant to the state of the art. Furthermore, the window
layer is structured only at the end of the manufacturing process,
so that the risk of breakage of the window layer in the preceding
steps is comparatively slight.
[0037] A process in which the window layer is first structured and
provided with contact surfaces represents a second advantageous
alternative. The semiconductor layer sequence is then applied. In
this case, higher temperatures such as those necessary for
sintering certain contact metallizations can be used to perform the
contact metallization. These temperatures are usually so high that
the semiconductor layer sequence would be damaged by them.
Therefore, such damage is avoided by performing the contact
metallization at the beginning of the manufacturing process.
[0038] In a third advantageous alternative manufacturing process,
the structuring of the window layer takes place in two steps. To
this end, the window layer is first prestructured to the extent
necessary for developing the contact surfaces on the lateral faces.
The contact surfaces are then developed, for example by vapor
deposition. The semiconductor layer sequence is then applied to the
window layer prestructured in this way and provided with contact
surfaces. The window layer is then subjected to final structuring.
This second structuring step is preferably combined with isolation
of the components, for example by sawing the window layer with a
shaped saw blade, and then breaking it apart. To minimize the risk
of breaking the structured window layer, the window layer can also
be mounted on a suitable auxiliary support.
[0039] Other features, benefits, and suitabilities of the invention
will be explained below with reference to examples of embodiment in
combination with FIGS. 1 to 16.
DESCRIPTION OF DRAWINGS
[0040] FIG. 1 a schematic cross sectional illustration of a first
example of embodiment of a semiconductor component pursuant to the
invention,
[0041] FIG. 2 a schematic cross sectional illustration of a second
example of embodiment of a semiconductor component pursuant to the
invention,
[0042] FIG. 3 a schematic cross sectional illustration of a third
example of embodiment
[0043] FIG. 4 a schematic cross sectional illustration of a fourth
example of embodiment of a semiconductor component pursuant to the
invention,
[0044] FIG. 5 a schematic cross sectional illustration of a fifth
example of embodiment of a semiconductor component pursuant to the
invention,
[0045] FIG. 6 a schematic cross sectional illustration of a sixth
example of embodiment of a semiconductor component pursuant to the
invention,
[0046] FIG. 7 a schematic cross sectional illustration of a seventh
example of embodiment of a semiconductor component pursuant to the
invention,
[0047] FIG. 8 a schematic cross sectional illustration of an eighth
example of embodiment of a semiconductor component pursuant to the
invention,
[0048] FIG. 9 a schematic cross sectional illustration of a ninth
example of embodiment of a semiconductor component pursuant to the
invention,
[0049] FIG. 10 a schematic cross sectional illustration of a tenth
example of embodiment of a semiconductor component pursuant to the
invention,
[0050] FIG. 11 a schematic cross sectional illustration of an
eleventh example of embodiment of a semiconductor component
pursuant to the invention,
[0051] FIG. 12 a schematic perspective illustration of a twelfth
example of embodiment of a semiconductor component pursuant to the
invention,
[0052] FIG. 13 a schematic illustration of a thirteenth example of
embodiment of a semiconductor component pursuant to the
invention,
[0053] FIG. 14 a schematic illustration of a first example of
embodiment of a manufacturing process pursuant to the invention in
five intermediate steps,
[0054] FIG. 15 a schematic illustration of a second example of
embodiment of a manufacturing process pursuant to the invention in
six intermediate steps,
[0055] FIG. 16 a device for implementing an intermediate step in
the examples of embodiment of a manufacturing process pursuant to
the invention, and
[0056] FIG. 17 a schematic illustration of a radiation-emitting
semiconductor component pursuant to the priority-determining Patent
Application DE 100 067 38.7.
DETAILED DESCRIPTION
[0057] The example of embodiment shown in FIG. 1 has a window 1
with a first principal face 2 and a second principal face 3. A
multilayered structure 4 with an active layer 5 that emits
radiation during operation is applied to the first principal face 2
and is coated with a contact metallization 6.
[0058] The window 1 itself is formed from a cuboid base form 7
rectangular in cross section that has recesses 8 on its
circumference. The window flanks 10 thus produced also correspond
to the lateral faces of the recess and have a first subregion 10a
that is arranged at an angle to the principal faces 2, 3 of the
window and that changes into a second subregion 10b orthogonal to
the principal faces at a greater distance from the multilayered
structure 4.
[0059] In this second subregion 10b, the window flanks are provided
with reflective contact metallization 11 that also covers the
second principal face 3 of the window 1. The current paths 12 from
the active layer to the contact surface 11 are shortened on the
average by the contact surface 11 raised on the window flank 10b,
and thus the series resistance of the component is advantageously
lowered. The radiation is preferably output in the inclined region
10a of the window flanks.
[0060] In the example of embodiment shown in FIG. 2 the contact
metallization 11 extends over the inclined subregions 10a of the
window flanks. This achieves a further shortening of the current
paths 12 and thus a reduction of series resistance. Of course the
subregions 10a are then no longer available for direct radiation
output. In this example of embodiment, therefore, the contact
metallization 11 is made reflective so that the fractions of
radiation emitted into the window for the most part are again
reflected toward the multilayered structure 4 and are subsequently
output. This is made clear by way of example by the beams 13a and
13b. Alternatively, the corresponding contact surfaces can also be
perforated.
[0061] In the third example of embodiment shown in FIG. 3, in
contrast to the examples of embodiment described above, the recess
8 runs through the center of the second principal face 3 as a
central indentation. The contact metallization 11 is developed over
the entire area over the second principal face 3 and the lateral
faces of the indentation 8. The current path 12 to the active layer
is shortened in this way within the indentation 8, and the series
resistance of the component is reduced. The contact metallization
can again be made reflective to increase the radiation yield.
[0062] FIG. 4 shows a fourth example of embodiment, in which the
envelope of the first example of embodiment is advantageously
combined with the central indentation of the third example of
embodiment. In this way the series resistance is advantageously
lowered by the shortening of the current path 12 as in the third
example of embodiment, with the window flank being available at the
same time for output of radiation. In addition, because of the
central indentation 8 with reflective contact metallization 11, the
radiation yield is increased by the radiation fractions 13
reflected out laterally.
[0063] In the firth example of embodiment shown in FIG. 5, the
contact metallization 11 extends both across the central
indentation 8 in the second principal face of the window 1 and
across subregions of the window flanks 10. Compared to the fourth
example of embodiment, the series resistance is lowered further in
this way, with this entailing a reduced radiation yield in the area
of the contact metallization. Depending on how the parameters of
series resistance and radiation yield are weighted, the fourth or
the fifth example of embodiment may be more advantageous, with the
transition between these two examples of embodiment being
continuous depending on the extent of the contact metallization on
the window flanks.
[0064] The radiation yield can be increased by reflection at the
central indentation 8 in the second principal face 3 in various
ways. One possibility has already been shown in the context of the
fourth example of embodiment in FIG. 4, beam 13c. If the angle of
opening of the central indentation 8 is enlarged, the result is to
increase reflection toward the multilayered structure 4 and thus
output through the multilayered structure 4.
[0065] This is illustrated in the sixth example of embodiment in
FIG. 6 with reference to the beam 13d. Aside from the central
indentation 8, this example of embodiment corresponds to the fourth
example of embodiment, FIG. 4. The central indentation 8, on the
other hand, is cut distinctly deeper than in FIG. 4 and has a
five-cornered cross section, which is composed of a rectangle with
added triangle. The angle of opening of the triangle is greater
than shown in the example of embodiment illustrated in FIG. 4 and
causes increased reflection toward the multilayered structure 4. It
is advantageous in this case to perforate the contact surface 6 on
the multilayered structure and thus enlarge the output through this
contact surface.
[0066] The deeply cut and completely metallized recess 8 also leads
to an especially great shortening of the current path 12 because of
the closeness of the bottom face of the recess to the multilayered
structure 4.
[0067] In the seventh example of embodiment illustrated in FIG. 7,
in contrast to the sixth example of embodiment, the angle of
opening of the central recess is chosen to be smaller. This leads
to increased reflection toward the inclined lateral window face
sections 10a, and in connection with this to increased output on
the part of the multilayered structure 4. It is also advantageous
here to perforate the contact surface 6 on the multilayered
structure 4. Various beam paths are shown schematically by the
beams 13.
[0068] In the eighth example of embodiment shown in FIG. 8, in
contrast to the prior examples of embodiment, only the second
principal face 3 and the multilayered structure 4 are provided with
contact surfaces, with the contact surface 6 on the multilayered
structure being perforated. This achieves particularly high
radiation output through the lateral faces 10. The central
indentation 8 is designed so that total reflection occurs on a
portion of its lateral faces.
[0069] In the examples of embodiment shown in FIGS. 9 and 10, the
lateral faces of the window are partially provided with perforated
contact surfaces. With these, radiation output is also
advantageously possible in the area of these contact surfaces, with
series resistance being beneficially reduced by the reduction of
the distance between the contact surfaces 6 and 11. In the example
of embodiment shown in FIG. 9, the contact surface also extends
over the central recess 8. In the example of embodiment according
to FIG. 10, on the other hand, the central recess is uncoated, to
reduce manufacturing costs, and the radiation 13 is totally
reflected on the inside of the central recess 8.
[0070] FIG. 11 illustrates another example of embodiment, which in
contrast to the previously described examples of embodiment has two
central recesses 8a, b. The recesses 8a, b and the contact
metallization 11 on them correspond in shape to the sixth example
of embodiment; naturally combination with the other shown examples
of embodiment is likewise possible. The multiple arrangement of
recesses in the second principal face 3 is advantageous especially
for large-area semiconductor components, since both the series
resistance of the component can be lowered and the radiation yield
over the entire component can be increased with a plurality of
recesses. Of course more than the two recesses 8a, b can also be
made if the stability of the component permits.
[0071] In the examples of embodiment, the window 1 preferably
consists of silicon carbide onto which a gallium nitride-based
multilayered structure is applied. Silicon carbide is preferably
used as the epitaxy substrate for gallium nitrite-based
semiconductor elements. Gallium nitride-based materials here,
besides GaN itself, means materials derived from or related to GaN,
in particular ternary or quaternary mixed crystal systems such as
AlGaN (Al.sub.1-xGa.sub.xN, 0.ltoreq.x.ltoreq.1), InGaN
(In.sub.1-xGa.sub.xN, 0.ltoreq.x.ltoreq.1), InAlN
(In.sub.1-xAl.sub.xN, 0.ltoreq.x.ltoreq.1), and AlInGaN (AlInGaN
(Al.sub.1-x-yIn.sub.xGa.sub.yN, 0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1).
[0072] The epitaxial production of such gallium nitride-based
components requires a substrate largely matching the gallium
nitride lattice, for which silicon carbide is especially
suitable.
[0073] Of course silicon carbide has a very high index of
refraction of about 2.7, so that the total reflection losses are
correspondingly high and the degree of output is correspondingly
low. The shown examples of embodiment advantageously increase the
radiation yield, especially because of the inclined lateral faces.
The series resistance of the component, increased in principle by
the reduced cross section of the window, is compensated for, or
furthermore even lowered, by the laterally raised contact surfaces.
Providing reflective, semi-transparent or perforated contact
metallizations contributes to further increasing the radiation
yield.
[0074] However, the invention is not limited to gallium
nitride-based systems, but can also be used with other
semiconductor systems, for example such as materials based on
gallium arsenide, gallium phosphide, or zinc selenide. Here also, a
substantial fraction of the radiation generated remains in the
multilayered structure-window arrangement because of total
reflection and is ultimately absorbed.
[0075] The invention is also beneficial for window materials other
than those mentioned so far, for example materials based on quartz
glass, diamond, ITO (indium tin oxide), or on zinc oxide, tin
oxide, indium oxide, or gallium phosphide, since as a rule with all
of these windows there is a transition to an optically thinner
medium by which total reflection can occur and the degree of output
is accordingly reduced.
[0076] The invention is also advantageous for potted semiconductor
bodies and windows or for those otherwise provided with a covering,
since the covering as a rule has a lower index of refraction so
that in this case also, the radiation yield is reduced by total
reflection.
[0077] A window made of the materials mentioned can be applied to
the multilayered structure after the multilayered structure is
produced. In epitaxial production of the multilayered structure,
this is possible, for example, by detaching the epitaxy substrate
after the epitaxy and bonding the window to the multilayered
structure in its place by a wafer-bonding process.
[0078] Alternatively, the window can also be applied to the
epitaxially manufactured semiconductor surface and the epitaxy
substrate then detached thereafter. This procedure has the
advantage that the epitaxy substrate can be reused, which leads to
a clear cost benefit especially in the case of expensive materials,
for example silicon carbide substrates in this case.
[0079] FIG. 12 illustrates schematically a first example of
embodiment of a manufacturing method with reference to five
intermediate steps 12a to 12c.
[0080] A window layer 20 from which the window 1 will later be made
is first made ready, FIG. 12a. The window layer 20 can be in the
form of a silicon carbide substrate, for example.
[0081] A semiconductor layer sequence 21 is applied to the window
layer 20; in particular it contains an active semiconductor layer
that generates radiation in operation. The semiconductor layer
sequence 21 corresponds to the multilayered structure 4 of a
semiconductor component pursuant to the invention. The sequence of
layers is preferably grown epitaxially or applied by a
wafer-bonding method. An epitaxy process advantageously reduces the
number of manufacturing steps, since attachment to the window layer
20 already occurs with the epitaxial production of the
semiconductor layer sequence 21. On the other hand, a wafer-bonding
process has the advantage that materials unsuitable for epitaxy but
otherwise beneficial can also be used for the window layer. In
addition, the epitaxy substrate used in the manufacture of the
semiconductor layer sequence can be reused, and the manufacturing
costs can thus be reduced.
[0082] After attaching the semiconductor layer sequence 21, the
window layer 20 is structured, FIG. 12b. In the example of
embodiment shown, the window layer 12 for this purpose is sawed at
the parting planes 24 intended for later singling. The saw blade
has a shaped edge that is complementary in cross section in the
sawing region to the recess 23 to be formed. To make a central
indentation, as illustrated by way of example in the third example
of embodiment, the sawing would have to occur only between the
parting planes 24.
[0083] Overall metallization 25 is then performed on the structured
window layer 20. This step will be explained in greater detail
below.
[0084] The composite of semiconductor layer sequences 21 and window
layer 20 is then divided into individual semiconductor components
by breaking it at the parting planes 24, with the parts of the
window layer 20 constituting the window 1 and the parts of the
semiconductor layer sequence 21 applied thereto constituting the
multilayered structure 4.
[0085] FIG. 13 shows a second example of embodiment of a
manufacturing method pursuant to the invention. Again, the process
begins with preparation of a window layer 20, FIG. 13a. The window
layer 20 has a first principal face 26 that is intended for the
attachment of a semiconductor layer sequence. Structuring is
carried out on the second principal face 27 of the window
layer.
[0086] The window layer 20 is then prestructured before attaching
the semiconductor layer sequence 21, FIG. 13b. For this purpose the
window layer 20 is sawed into on the second principal face 27 at
the intended parting planes 24, so that a plurality of recesses 23
is produced, for example with rectangular cross sections. The depth
of sawing and the depth of the recesses 23 are chosen so that the
lateral faces to be provided with a contact surface are just
exposed. A more extensive, deeper structuring takes place only in a
later step of the manufacturing process, so that the mechanical
stability of the window layer is largely retained initially.
[0087] The recesses 23 formed in this way and the remaining areas
of the second principal face 27 are then provided with continuous
contact metallization 25. Since there are still no semiconductor
layers on the window layer 20, the contact metallization 25 can
preferably be developed at substantially higher temperatures than
in the previous example of embodiment. This simplifies or permits
sintering of the contact metallization, for example, which likewise
advantageously lowers the series resistance of the component.
[0088] In the next step, as in the example of embodiment described
previously, a semiconductor layer sequence 21 that contains an
active layer 24 is applied to the first principal face 26 of the
window layer 20. Since the contact metallization 25 has already
been formed, sensitive semiconductor structures in particular can
also be formed, for example multiple quantum well structures with
low structural thicknesses, which degrade easily at higher
temperatures.
[0089] This is followed by another structuring step in which the
structuring of the window layer 20 already begun is completed. The
recesses 23 already formed are deepened and further shaped by
sawing again, for example by forming inclined flanks in the window
layer to increase radiation output. In addition, the semiconductor
layer sequence 21 is also divided into individual multilayered
structures 4. An etching method using a known masking technique,
for example, is suitable for the structuring of the semiconductor
layer sequence 21.
[0090] In the last step, FIG. 13f, the composite of window layers
and multilayered structure is singled, as in the preceding example
of embodiment.
[0091] In the described manufacturing method it is necessary to
provide structured surfaces, for example the surface 27 and the
recesses 23 formed in it in FIG. 12, with a uniform contact
surface. These structured surfaces are composed of a plurality of
individual surfaces joined at an angle, which makes it difficult to
develop a contact surface. A suitable device for applying contact
metallization is shown in FIG. 14. The device contains a source of
metal vapor 30 from which the metal vapor 32 escapes in a
preferential direction. An electron beam vaporizer with a target
and an electron beam aimed at this target can be used as the source
of metal vapor 30, for example.
[0092] The surface of a window layer 20 to be vapor-metallized is
turned toward the vapor source 30, with the surface to be
metallized being arranged at an angle to the preferential direction
of the source of metal vapor 32. The metal vapor 32 therefore is
deposited on both the principal face 27 and the insides of the
recesses 23. The metallized region within the recesses is
determined essentially by shadows of projecting edges. The depth to
which the metal layer is developed inside the recesses 23 varies
with the slope of the surface to be metallized relative to the
preferential direction of the metallization source.
[0093] FIG. 15 shows in perspective another example of embodiment
of the invention, with the window having flanks with an inclined
region 10a to increase radiation output. The multilayered structure
4 is also provided with a perforated contact surface 6 that has a
plurality of circular openings 14. The contact surface itself can
be a thick, reflective platinum or palladium contact layer, for
example, with the preferred thickness being between 10 nm and 30
nm.
[0094] Alternatively, the contact layer 6 can also be of thin form,
so that the contact layer 6 is transparent to radiation. The
radiation generated is then beneficially output through the
openings 14 as well as through the contact layer also.
[0095] FIG. 16 shows two plan views of an example of embodiment of
the invention with perforated contact surface. In the example of
embodiment illustrated in FIG. 16a, the openings in the contact
layer 6 are circular in shape. Alternatively, the openings can also
be formed of crossed slits, for example, as shown in FIG. 16b. It
is preferred for the openings to be tightly packed. So that the
intermediate regions of the contact surface do not become too
narrow and thus impair conduction of current into the component,
the crossed-slit openings in FIG. 16b are arranged so that their
mutual separation is no smaller than the arm width a.
[0096] The diameter or arm width a of the openings 14 is
advantageously of such a dimension that current propagation
produces a largely homogeneous current density in the active
layer.
[0097] The explanation of the invention with reference to the shown
examples of embodiment naturally does not represent any limitation
of the invention to these examples of embodiment.
* * * * *