U.S. patent application number 13/568021 was filed with the patent office on 2013-08-08 for semiconductor-on-diamond devices and associated methods.
The applicant listed for this patent is Chien-Min Sung. Invention is credited to Chien-Min Sung.
Application Number | 20130200394 13/568021 |
Document ID | / |
Family ID | 39318418 |
Filed Date | 2013-08-08 |
United States Patent
Application |
20130200394 |
Kind Code |
A1 |
Sung; Chien-Min |
August 8, 2013 |
SEMICONDUCTOR-ON-DIAMOND DEVICES AND ASSOCIATED METHODS
Abstract
Semiconductor-on-diamond devices and methods for making such
devices are provided. One such method may include depositing a
semiconductor layer on a semiconductor substrate, depositing an
adynamic diamond layer on the semiconductor layer opposite the
semiconductor substrate, and coupling a support substrate to the
adynamic diamond layer opposite the semiconductor layer to support
the adynamic layer.
Inventors: |
Sung; Chien-Min; (Tansui,
TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sung; Chien-Min |
Tansui |
|
TW |
|
|
Family ID: |
39318418 |
Appl. No.: |
13/568021 |
Filed: |
August 6, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11584258 |
Oct 20, 2006 |
8236594 |
|
|
13568021 |
|
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|
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Current U.S.
Class: |
257/77 ;
438/46 |
Current CPC
Class: |
H01L 33/641 20130101;
H01L 33/30 20130101; H01L 21/02595 20130101; H01L 21/3146 20130101;
H01L 21/02527 20130101; H01L 33/0093 20200501; H01L 21/02444
20130101; H01L 21/0237 20130101 |
Class at
Publication: |
257/77 ;
438/46 |
International
Class: |
H01L 33/30 20060101
H01L033/30 |
Claims
1. A method of making a semiconductor-on-diamond device,
comprising: depositing a semiconductor layer on a semiconductor
substrate; depositing an adynamic diamond layer on the
semiconductor layer opposite the semiconductor substrate; and
coupling a support substrate to the adynamic diamond layer opposite
the semiconductor layer to support the adynamic layer.
2. The method of claim 1, wherein the semiconductor substrate
includes a member selected from the group consisting of silicon,
silicon carbide, silicon germanium, sapphire, aluminum arsenide,
aluminum phosphide, gallium arsenide, gallium phosphide, gallium
nitride, and combinations thereof.
3. The method of claim 1, wherein the semiconductor layer includes
a member selected from the group consisting of silicon, silicon
carbide, silicon germanium, gallium arsenide, gallium nitride,
germanium, zinc sulfide, gallium phosphide, gallium antimonide,
gallium indium arsenide phosphide, aluminum phosphide, aluminum
arsenide, aluminum gallium arsenide, gallium nitride, boron
nitride, aluminum nitride, indium arsenide, indium phosphide,
indium antimonide, indium nitride, and combinations thereof.
4. The method of claim 1, wherein deposting a semiconductor layer
further includes: depositing a first semiconductor layer on the
semiconductor substrate; and depositing at least one second
semiconductor layer on the first semiconductor layer.
5. The method of claim 1, wherein depositing the adynamic diamond
layer further includes depositing the adynamic diamond layer as
conformal diamond coating.
6. The method of claim 1, further including removing the
semiconductor substrate from the semiconductor layer following the
coupling of the support substrate to the adynamic diamond
layer.
7. The method of claim 1, further including depositing an
additional semiconductor layer onto the semiconductor layer
opposite to the adynamic diamond layer.
8. The method of claim 1, further including depositing at least one
interdigital transducer on the semiconductor layer.
9. The method of claim 1, wherein light generated in the
semiconductor layer is emitted primarily through the semiconductor
substrate.
10. A semiconductor-on-diamond device having improved thermal
properties made by the method of claim 1, comprising: an adynamic
diamond layer disposed on a support substrate; and a semiconductor
layer disposed on the adynamic diamond layer.
11. The device of claim 10, wherein the semiconductor substrate
includes a member selected from the group consisting of silicon,
silicon carbide, silicon germanium, sapphire, aluminum arsenide,
aluminum phosphide, gallium arsenide, gallium phosphide, gallium
nitride, and combinations thereof.
12. The device of claim 10, wherein the semiconductor layer
includes a member selected from the group consisting of silicon,
silicon carbide, silicon germanium, gallium arsenide, gallium
nitride, germanium, zinc sulfide, gallium phosphide, gallium
antimonide, gallium indium arsenide phosphide, aluminum phosphide,
aluminum arsenide, aluminum gallium arsenide, gallium nitride,
boron nitride, aluminum nitride, indium arsenide, indium phosphide,
indium antimonide, indium nitride, and combinations thereof.
13. The device of claim 10, wherein the semiconductor-on-diamond
device is a light-emitting diode.
14. The device of claim 10, wherein the semiconductor-on-diamond
device is a laser diode.
15. The device of claim 10, wherein the semiconductor-on-diamond
device is an acoustic filter.
16. The device of claim 10, wherein the acoustic filter is a SAW
filter.
17. A light-emitting diode device, comprising: a sapphire
substrate; a semiconductor layer coupled to the sapphire substrate,
the semiconductor layer including a member selected from the group
consisting of gallium nitride, aluminum nitride, or combinations
thereof; and an adynamic diamond layer coupled to the semiconductor
layer opposite the sapphire substrate, wherein the light-emitting
diode device is configured such that light generated in the
semiconductor layer is emitted primarily through the sapphire
substrate.
18. The device of claim 17, further comprising a support substrate
coupled to the adynamic layer opposite the semiconductor layer.
Description
PRIORITY DATA
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/584,258, filed on Oct. 20, 2006, now issued
as U.S. Pat. No. 8,236,594, which is incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to methods and
associated devices having semiconductor-on-diamond layers.
Accordingly, the present invention involves the electrical and
material science fields.
BACKGROUND OF THE INVENTION
[0003] In many developed countries, major portions of the
populations consider electronic devices to be integral to their
lives. Such increasing use and dependence has generated a demand
for electronics devices that are smaller and faster. As electronic
circuitry increases in speed and decreases in size, cooling of such
devices becomes problematic.
[0004] Electronic devices generally contain printed circuit boards
having integrally connected electronic components that allow the
overall functionality of the device. These electronic components,
such as processors, transistors, resistors, capacitors,
light-emitting diodes (LEDs), etc., generate significant amounts of
heat. As it builds, heat can cause various thermal problems
associated with such electronic components. Significant amounts of
heat can affect the reliability of an electronic device, or even
cause it to fail by, for example, causing burn out or shorting both
within the electronic components themselves and across the surface
of the printed circuit board. Thus, the buildup of heat can
ultimately affect the functional life of the electronic device.
This is particularly problematic for electronic components with
high power and high current demands, as well as for the printed
circuit boards that support them.
[0005] Various cooling devices have been employed such as fans,
heat sinks, Peltier and liquid cooling devices, etc., as means of
reducing heat buildup in electronic devices. As increased speed and
power consumption cause increasing heat buildup, such cooling
devices generally must increase in size to be effective and may
also require power to operate. For example, fans must be increased
in size and speed to increase airflow, and heat sinks must be
increased in size to increase heat capacity and surface area. The
demand for smaller electronic devices, however, not only precludes
increasing the size of such cooling devices, but may also require a
significant size decrease.
[0006] As a result, methods and associated devices are being sought
to provide adequate cooling of electronic devices while minimizing
size and power constraints placed on such devices due to
cooling.
SUMMARY OF THE INVENTION
[0007] Accordingly, the present invention provides
semiconductor-on-diamond devices having improved thermal properties
and methods for making such devices. In one aspect, for example, a
method of making a semiconductor-on-diamond device is provided.
Such a method may include depositing a semiconductor layer on a
semiconductor substrate, depositing an adynamic diamond layer on
the semiconductor layer opposite the semiconductor substrate, and
coupling a support substrate to the adynamic diamond layer opposite
the semiconductor layer to support the adynamic layer.
[0008] Numerous materials may be utilized as semiconductor
substrates upon which the semiconductor layer is deposited.
Examples of such semiconductor substrates may include, without
limitation, silicon, silicon carbide, silicon germanium, sapphire,
aluminum arsenide, aluminum phosphide, gallium arsenide, gallium
phosphide, gallium nitride, and combinations thereof. In one
specific aspect, the semiconductor substrate may include sapphire.
In another specific aspect, the semiconductor substrate may include
silicon. Additionally, various semiconductor materials are
contemplated to utilization as a semiconductor layer. The selection
of particular semiconductor materials may depend on the type of
semiconductor device and the intended use of the device. Specific
semiconductor layer materials may include, however, silicon,
silicon carbide, silicon germanium, gallium arsenide, gallium
nitride, germanium, zinc sulfide, gallium phosphide, gallium
antimonide, gallium indium arsenide phosphide, aluminum phosphide,
aluminum arsenide, aluminum gallium arsenide, gallium nitride,
boron nitride, aluminum nitride, indium arsenide, indium phosphide,
indium antimonide, indium nitride, and combinations thereof. In one
specific aspect, the semiconductor layer may be gallium nitride. In
another specific aspect, the semiconductor layer may be aluminum
nitride. In some aspects it is also contemplated that multiple
semiconductor layers may be deposited. For example, depositing a
semiconductor layer may further include depositing a first
semiconductor layer on the semiconductor substrate and depositing
at least one second semiconductor layer on the first semiconductor
layer.
[0009] The adynamic diamond layers of the present invention are not
self supporting, and thus may require support from an associated
substrate. At least part of the adynamic nature of the diamond
layer may be a result of the thickness of the diamond layer. In one
aspect, for example, the adynamic diamond layer has a thickness of
less than about 30 microns. In another aspect, the adynamic diamond
layer has a thickness of from about 5 microns to about 20
microns.
[0010] Any type of diamond material may be utilized for making the
adynamic diamond layers. In one aspect, however, the adynamic
diamond layer may be deposited as a conformal diamond coating
having adynamic properties. Such a conformal diamond coating may be
deposited by exposing substantially all of a growth surface of the
semiconductor layer to chemical vapor deposition conditions without
an electrical bias such that a carbon film is formed upon
substantially all of the growth surface, and depositing a layer of
diamond by a chemical vapor deposition process onto the carbon film
to form the adynamic diamond layer.
[0011] In another aspect of the present invention, the
semiconductor substrate may be removed from the semiconductor layer
following the coupling of the support substrate to the adynamic
diamond layer. Following such removal, the device may be modified
in various ways. For example, in one aspect an additional
semiconductor layer may be deposited onto the semiconductor layer
opposite to the adynamic diamond layer. In another aspect, at least
one interdigital transducer may be deposited on the semiconductor
layer.
[0012] In yet another aspect of the present invention, at least a
portion of the semiconductor substrate may be retained by the
semiconductor layer. Accordingly, light generated in the
semiconductor layer may be emitted primarily through the
semiconductor substrate.
[0013] The present invention also provides semiconductor-on-diamond
devices having improved thermal properties made according to the
methods disclosed herein. Such a device may include an adynamic
diamond layer disposed on a support substrate, and a semiconductor
layer disposed on the adynamic diamond layer. Various
semiconductor-on-diamond devices are contemplated having such a
configuration. For example, in one aspect the
semiconductor-on-diamond device is a light-emitting diode (LED). In
another aspect, the semiconductor-on-diamond device is a laser
diode. In yet another aspect, the semiconductor-on-diamond device
is an acoustic filter. Though various acoustic filters are
contemplated, in one aspect the acoustic filter is a SAW
filter.
[0014] In yet another aspect of the present invention, an LED
device is provided. Such a device may include a sapphire substrate,
a semiconductor layer of gallium nitride, aluminum nitride, or a
combination of gallium nitride and aluminum nitride coupled to the
sapphire substrate, and an adynamic diamond layer coupled to the
semiconductor layer opposite the sapphire substrate. Such an LED
device is configured such that light generated in the semiconductor
layer is emitted primarily through the sapphire substrate. In some
aspects, a support substrate may be further coupled to the adynamic
layer opposite the semiconductor layer.
[0015] There has thus been outlined, rather broadly, various
features of the invention so that the detailed description thereof
that follows may be better understood, and so that the present
contribution to the art may be better appreciated. Other features
of the present invention will become clearer from the following
detailed description of the invention, taken with the accompanying
claims, or may be learned by the practice of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a cross-section view of a semiconductor device
being constructed in accordance with one embodiment of the present
invention.
[0017] FIG. 2 is a cross-section view of a semiconductor device in
accordance with one embodiment of the present invention.
[0018] FIG. 3 is a cross-section view of a semiconductor device in
accordance with one embodiment of the present invention.
[0019] FIG. 4 is a cross-section view of a semiconductor device in
accordance with one embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
[0020] In describing and claiming the present invention, the
following terminology will be used in accordance with the
definitions set forth below.
[0021] The singular forms "a," "an," and, "the" include plural
referents unless the context clearly dictates otherwise. Thus, for
example, reference to "a heat source" includes reference to one or
more of such sources, and reference to "the diamond layer" includes
reference to one or more of such layers.
[0022] The terms "heat transfer," "heat movement," and "heat
transmission" can be used interchangeably, and refer to the
movement of heat from an area of higher temperature to an area of
cooler temperature. It is intended that the movement of heat
include any mechanism of heat transmission known to one skilled in
the art, such as, without limitation, conductive, convective,
radiative, etc.
[0023] As used herein, the term "emitting" refers to the process of
moving heat or light from a solid material into the air.
[0024] As used herein, "light-emitting surface" refers to a surface
of a device or object from which light is intentionally emitted.
Light may include visible light and light within the ultraviolet
spectrum. An example of a light-emitting surface may include,
without limitation, a nitride layer of an LED, or of semiconductor
layers to be incorporated into an LED, from which light is
emitted.
[0025] As used herein, "vapor deposited" refers to materials which
are formed using vapor deposition techniques. "Vapor deposition"
refers to a process of depositing materials on a substrate through
the vapor phase. Vapor deposition processes can include any process
such as, but not limited to, chemical vapor deposition (CVD) and
physical vapor deposition (PVD). A wide variety of variations of
each vapor deposition method can be performed by those skilled in
the art. Examples of vapor deposition methods include hot filament
CVD, rf-CVD, laser CVD (LCVD), laser ablation, conformal diamond
coating processes, metal-organic CVD (MOCVD), sputtering, thermal
evaporation PVD, ionized metal PVD (IMPVD), electron beam PVD
(EBPVD), reactive PVD, and the like.
[0026] As used herein, "chemical vapor deposition," or "CVD" refers
to any method of chemically depositing diamond particles in a vapor
form upon a surface. Various CVD techniques are well known in the
art.
[0027] As used herein, "physical vapor deposition," or "PVD" refers
to any method of physically depositing diamond particles in a vapor
form upon a surface. Various PVD techniques are well known in the
art.
[0028] As used herein, "diamond" refers to a crystalline structure
of carbon atoms bonded to other carbon atoms in a lattice of
tetrahedral coordination known as sp.sup.3 bonding. Specifically,
each carbon atom is surrounded by and bonded to four other carbon
atoms, each located on the tip of a regular tetrahedron. Further,
the bond length between any two carbon atoms is 1.54 angstroms at
ambient temperature conditions, and the angle between any two bonds
is 109 degrees, 28 minutes, and 16 seconds although experimental
results may vary slightly. The structure and nature of diamond,
including its physical and electrical properties are well known in
the art.
[0029] As used herein, "distorted tetrahedral coordination" refers
to a tetrahedral bonding configuration of carbon atoms that is
irregular, or has deviated from the normal tetrahedron
configuration of diamond as described above. Such distortion
generally results in lengthening of some bonds and shortening of
others, as well as the variation of the bond angles between the
bonds. Additionally, the distortion of the tetrahedron alters the
characteristics and properties of the carbon to effectively lie
between the characteristics of carbon bonded in sp.sup.3
configuration (i.e. diamond) and carbon bonded in sp.sup.2
configuration (i.e. graphite). One example of material having
carbon atoms bonded in distorted tetrahedral bonding is amorphous
diamond.
[0030] As used herein, "diamond-like carbon" refers to a
carbonaceous material having carbon atoms as the majority element,
with a substantial amount of such carbon atoms bonded in distorted
tetrahedral coordination. Diamond-like carbon (DLC) can typically
be formed by PVD processes, although CVD or other processes could
be used such as vapor deposition processes. Notably, a variety of
other elements can be included in the DLC material as either
impurities, or as dopants, including without limitation, hydrogen,
sulfur, phosphorous, boron, nitrogen, silicon, tungsten, etc.
[0031] As used herein, "amorphous diamond" refers to a type of
diamond-like carbon having carbon atoms as the majority element,
with a substantial amount of such carbon atoms bonded in distorted
tetrahedral coordination. In one aspect, the amount of carbon in
the amorphous diamond can be at least about 90%, with at least
about 20% of such carbon being bonded in distorted tetrahedral
coordination. Amorphous diamond also has a higher atomic density
than that of diamond (176 atoms/cm.sup.3). Further, amorphous
diamond and diamond materials contract upon melting.
[0032] As used herein, "adynamic" refers to a type of layer which
is unable to independently retain its shape and/or strength. For
example, in the absence of a mold or support layer, an adynamic
diamond layer will tend to curl or otherwise deform when the mold
or support surface is removed. While a number of reasons may
contribute to the adynamic properties of a layer, in one aspect,
the reason may be the extreme thinness of the layer.
[0033] As used herein, "growth side," and "grown surface" may be
used interchangeably and refer to the surface of a film or layer
which is grows during a CVD process.
[0034] As used herein, "interdigital transducers" (IDT) and
"electrodes" may be used interchangeably and refer to conductive or
semi-conductive contacts which are coupled to a piezoelectric
semiconductor layer as known by those skilled in the art in order
to create an acoustic filter such as a SAW filter or other
electronic device. In one aspect of the present invention, the IDT
may be coupled to the piezoelectric semiconductor layer on an
outside surface thereof, or on the interface surface thereof.
[0035] As used herein, "substrate" refers to a support surface to
which various materials can be joined in forming a semiconductor or
semiconductor-on-diamond device. The substrate may be any shape,
thickness, or material, required in order to achieve a specific
result, and includes but is not limited to metals, alloys,
ceramics, and mixtures thereof. Further, in some aspects, the
substrate may be an existing semiconductor device or wafer, or may
be a material which is capable of being joined to a suitable
device.
[0036] As used herein, the term "substantially" refers to the
complete or nearly complete extent or degree of an action,
characteristic, property, state, structure, item, or result. For
example, an object that is "substantially" enclosed would mean that
the object is either completely enclosed or nearly completely
enclosed. The exact allowable degree of deviation from absolute
completeness may in some cases depend on the specific context.
However, generally speaking the nearness of completion will be so
as to have the same overall result as if absolute and total
completion were obtained. The use of "substantially" is equally
applicable when used in a negative connotation to refer to the
complete or near complete lack of an action, characteristic,
property, state, structure, item, or result. For example, a
composition that is "substantially free of" particles would either
completely lack particles, or so nearly completely lack particles
that the effect would be the same as if it completely lacked
particles. In other words, a composition that is "substantially
free of" an ingredient or element may still actually contain such
item as long as there is no measurable effect thereof.
[0037] As used herein, the term "about" is used to provide
flexibility to a numerical range endpoint by providing that a given
value may be "a little above" or "a little below" the endpoint.
[0038] As used herein, a plurality of items, structural elements,
compositional elements, and/or materials may be presented in a
common list for convenience. However, these lists should be
construed as though each member of the list is individually
identified as a separate and unique member. Thus, no individual
member of such list should be construed as a de facto equivalent of
any other member of the same list solely based on their
presentation in a common group without indications to the
contrary.
[0039] Concentrations, amounts, and other numerical data may be
expressed or presented herein in a range format. It is to be
understood that such a range format is used merely for convenience
and brevity and thus should be interpreted flexibly to include not
only the numerical values explicitly recited as the limits of the
range, but also to include all the individual numerical values or
sub-ranges encompassed within that range as if each numerical value
and sub-range is explicitly recited. As an illustration, a
numerical range of "about 1 to about 5" should be interpreted to
include not only the explicitly recited values of about 1 to about
5, but also include individual values and sub-ranges within the
indicated range. Thus, included in this numerical range are
individual values such as 2, 3, and 4 and sub-ranges such as from
1-3, from 2-4, and from 3-5, etc., as well as 1, 2, 3, 4, and 5,
individually.
[0040] This same principle applies to ranges reciting only one
numerical value as a minimum or a maximum. Furthermore, such an
interpretation should apply regardless of the breadth of the range
or the characteristics being described.
[0041] The Invention
[0042] The present invention provides semiconductor devices having
incorporated diamond layers and methods of making such devices.
Semiconductor devices are often challenging to cool, particularly
those that emit light. Much of the heat generated by such devices
may be associated with the surface that emits the light. For
example, an LED may consist of a plurality of nitride layers
arranged to emit light from a light-emitting surface. Because heat
sinks cannot interfere with the function of the nitride layers or
the light-emitting surface, they are often located at the junction
between the LED and a supporting structure such as a circuit board.
Such a heat sink location is relatively remote from the
accumulation of much of the heat, namely, the light-emitting
surface and the nitride layers. Additionally, in both semiconductor
devices that emit light and those that don't, heat may be trapped
within the semiconducting layers due to the relatively poor thermal
conductivity of materials that often make up these layers. The
inventor has developed semiconductor devices incorporating thin
adynamic layers of diamond that provide, among other things,
improved cooling properties to the device. Such a thin adynamic
layer of diamond increases the flow of heat laterally through the
semiconductor device to thus reduce the amount of heat trapped
within the semiconductor layers. This lateral heat transmission may
thus effectively improve the thermal properties of many
semiconductor devices. Additionally, it should be noted that the
beneficial properties provided by the adynamic diamond layer may
extend beyond cooling, and as such, the present scope should not be
limited thereto.
[0043] Accordingly, in one aspect of the present invention, a
method of making a semiconductor-on-diamond device is provided.
Such a method may include depositing a semiconductor layer on a
semiconductor substrate, depositing an adynamic diamond layer on
the semiconductor layer opposite the semiconductor substrate, and
coupling a support substrate to the adynamic diamond layer opposite
the semiconductor layer to support the adynamic layer. Any type of
semiconductor device known to generate heat would be considered to
be within the scope of the present invention. Specific examples may
include, without limitation, LEDs, laser diodes, acoustic filters
such as surface acoustic wave (SAW) and bulk acoustic wave (BAW)
filters, integrated circuit (IC) chips, etc.
[0044] Diamond materials have excellent thermal conductivity
properties that make them ideal for incorporation into
semiconductor devices. The transfer of heat that is present in the
semiconductor device can thus be accelerated from the device
through an adynamic diamond layer. It should be noted that the
present invention is not limited as to specific theories of heat
transmission. As such, in one aspect the accelerated movement of
heat from inside the device can be at least partially due to heat
movement into and through the adynamic diamond layer. Due to the
heat conductive properties of diamond, heat can rapidly spread
laterally through the diamond layer and to the edges of the
semiconductor device. Heat present around the edges will be more
rapidly dissipated into the air or into surrounding structures,
such as heat spreaders or device supports. Because the thermal
conductivity of diamond is greater that the thermal conductivity of
the semiconductor layer, a heat sink is established by the adynamic
diamond layer beneath the semiconductor layer. As such, heat that
builds up in the semiconductor layer is drawn into the adynamic
diamond layer and spread laterally to be discharged from the
device. Such accelerated heat transfer may result in semiconductor
devices with much cooler operational temperatures. Additionally,
the acceleration of heat transfer away from a light-emitting
surface not only cools the semiconductor device, but may also
reduce the heat load on many electronic components that are
spatially located near the semiconductor device.
[0045] In some aspects of the present invention, the edges of the
adynamic diamond layer may be exposed to the air. In such aspects,
the accelerated movement of heat away from the semiconductor layer
may be at least partially due to heat movement from the diamond
layer to air. For example, a diamond material such as diamond-like
carbon (DLC) has exceptional heat emissivity characteristics even
at temperatures below 100.degree. C., and as such, may effectively
radiate heat directly to the air. As has been discussed, many
semiconductor materials that comprise the device may conduct heat
much better than they emit heat. As such, heat can be conducted
through the semiconductor layer to the adynamic DLC layer, spread
laterally through the adynamic DLC layer, and subsequently emitted
to the air along the edges. Due to the high heat conductive and
radiative properties of DLC, heat movement from the DLC layer to
air can be greater than heat movement from the semiconductor layer
to air. Also, heat movement from the semiconductor device to the
adynamic DLC layer can be greater than heat movement from the
semiconductor device to the air. As such, the layer of DLC can
serve to accelerate heat transfer away from the semiconductor layer
more rapidly than heat can be transferred through the semiconductor
device itself, or from the semiconductor device to the air.
[0046] As has been suggested, various diamond materials may be
utilized to provide accelerated heat transferring properties to a
semiconductor device. Non-limiting examples of such diamond
materials may include diamond, DLC, amorphous diamond, and
combinations thereof. It should be noted, however, that any form of
natural or synthetic diamond material that may be utilized to cool
a semiconductor device is considered to be within the present
scope.
[0047] Generally, diamond layers may be formed by any means known,
including various vapor deposition techniques. Any number of known
vapor deposition techniques may be used to form these diamond
layers. The most common vapor deposition techniques include CVD and
PVD, although any similar method can be used if similar properties
and results are obtained. In one aspect, CVD techniques such as hot
filament, microwave plasma, oxyacetylene flame, rf-CVD, laser CVD
(LCVD), metal-organic CVD (MOCVD), laser ablation, conformal
diamond coating processes, and direct current arc techniques may be
utilized. Typical CVD techniques use gas reactants to deposit the
diamond or diamond-like material in a layer, or film. These gases
generally include a small amount (i.e. less than about 5%) of a
carbonaceous material, such as methane, diluted in hydrogen. A
variety of specific CVD processes, including equipment and
conditions, as well as those used for boron nitride layers, are
well known to those skilled in the art. In another aspect, PVD
techniques such as sputtering, cathodic arc, and thermal
evaporation may be utilized. Further, specific deposition
conditions may be used in order to adjust the exact type of
material to be deposited, whether DLC, amorphous diamond, or pure
diamond. It should also be noted that many semiconductor devices
such as LEDs may be degraded by high temperature. Care man need to
be taken to avoid damage during diamond deposition by depositing at
lower temperatures. For example, if the semiconductor contains InN,
deposition temperatures of up to about 600.degree. C. may be used.
In the case of GaN, layers may be thermally stable up to about
1000.degree. C. Additionally, preformed layers can be brazed,
glued, or otherwise affixed to the semiconductor layer or to the
support substrate of the semiconductor device using methods which
do not unduly interfere with the heat transference of the diamond
layer or the functionality of the device.
[0048] An optional nucleation enhancing layer can be formed on the
growth surface of the semiconductor layer in order to improve the
quality and deposition time of the adynamic diamond layer.
Specifically, the adynamic diamond layer can be formed by
depositing applicable nuclei, such as diamond nuclei, on the
diamond growth surface of the semiconductor layer and then growing
the nuclei into a film or layer using a vapor deposition technique.
In one aspect of the present invention, a thin nucleation enhancer
layer can be coated upon the semiconductor layer to enhance the
growth of the diamond layer. Diamond nuclei are then placed upon
the nucleation enhancer layer, and the growth of the adynamic
diamond layer proceeds via CVD.
[0049] A variety of suitable materials will be recognized by those
in skilled in the art which can serve as a nucleation enhancer. In
one aspect of the present invention, the nucleation enhancer may be
a material selected from the group consisting of metals, metal
alloys, metal compounds, carbides, carbide formers, and mixtures
thereof. Examples of carbide forming materials may include, without
limitation, tungsten (W), tantalum (Ta), titanium (Ti), zirconium
(Zr), chromium (Cr), molybdenum (Mo), silicon (Si), and manganese
(Mn). Additionally, examples of carbides include tungsten carbide
(WC), silicon carbide (SiC), titanium carbide (TiC), zirconium
carbide (ZrC), and mixtures thereof among others.
[0050] The nucleation enhancer layer, when used, is a layer which
is thin enough that it does not to adversely affect the thermal
transmission properties of the adynamic diamond layer. In one
aspect, the thickness of the nucleation enhancer layer may be less
than about 0.1 micrometers. In another aspect, the thickness may be
less than about 10 nanometers. In yet another aspect, the thickness
of the nucleation enhancer layer is less than about 5 nanometers.
In a further aspect of the invention, the thickness of the
nucleation enhancer layer is less than about 3 nanometers.
[0051] Various methods may be employed to increase the quality of
the diamond in the nucleation surface of the diamond layer which is
created by vapor deposition techniques. For example, diamond
particle quality can be increased by reducing the methane flow
rate, and increasing the total gas pressure during the early phase
of diamond deposition. Such measures, decrease the decomposition
rate of carbon, and increase the concentration of hydrogen atoms.
Thus a significantly higher percentage of the carbon will be
deposited in a sp.sup.3 bonding configuration, and the quality of
the diamond nuclei formed is increased. Additionally, the
nucleation rate of diamond particles deposited on the growth
surface of the semiconductor layer or the nucleation enhancer layer
may be increased in order to reduce the amount of interstitial
space between diamond particles. Examples of ways to increase
nucleation rates include, but are not limited to; applying a
negative bias in an appropriate amount, often about 100 volts, to
the growth surface; polishing the growth surface with a fine
diamond paste or powder, which may partially remain on the growth
surface; and controlling the composition of the growth surface such
as by ion implantation of C, Si, Cr, Mn, Ti, V, Zr, W, Mo, Ta, and
the like by PVD or PECVD. PVD processes are typically at lower
temperatures than CVD processes and in some cases can be below
about 200.degree. C. such as about 150.degree. C. Other methods of
increasing diamond nucleation will be readily apparent to those
skilled in the art.
[0052] In one aspect of the present invention, the diamond layer
may also be a conformal diamond layer. Conformal diamond coating
processes can provide a number of advantages over conventional
diamond film processes. Conformal diamond coating can be performed
on a wide variety of substrates, including non-planar substrates. A
growth surface can be pretreated under diamond growth conditions in
the absence of a bias to form a carbon film. The diamond growth
conditions can be conditions that are conventional CVD deposition
conditions for diamond without an applied bias. As a result, a thin
carbon film can be formed which is typically less than about 100
angstroms. The pretreatment step can be performed at almost any
growth temperature such as from about 200.degree. C. to about
900.degree. C., although lower temperatures below about 500.degree.
C. may be preferred. Without being bound to any particular theory,
the thin carbon film appears to form within a short time, e.g.,
less than one hour, and is a hydrogen terminated amorphous
carbon.
[0053] Following formation of the thin carbon film, the growth
surface may then be subjected to diamond growth conditions to form
the adynamic diamond layer as an adynamic conformal diamond layer.
The diamond growth conditions may be those conditions which are
commonly used in traditional CVD diamond growth. However, unlike
conventional diamond film growth, the diamond film produced using
the above pretreatment steps results in a conformal diamond film
that typically begins growth substantially over the entire growth
surface with substantially no incubation time. In addition, a
continuous film, e.g. substantially no grain boundaries, can
develop within about 80 nm of growth. Adynamic diamond layers
having substantially no grain boundaries may move heat more
efficiently than those layers having grain boundaries.
[0054] The adynamic diamond layer may be of any thickness that
would allow cooling according to the methods and devices of the
present invention. Thicknesses may vary depending on the
application and the semiconductor device configuration. For
example, greater cooling requirements may require a slightly
thicker adynamic diamond layer. The thickness may also vary
depending on the material used in the diamond layer. That being
said, in one aspect an adynamic diamond layer may be less than
about 30 microns. In another example, an adynamic diamond layer may
be from about 5 microns to about 20 microns.
[0055] FIG. 1 shows selected steps of constructing a
semiconductor-on-diamond device according to particular aspects of
the present invention. A semiconductor substrate 12 is provided
upon which further layers of the semiconductor device are
deposited. The semiconductor substrate 12 may be made from a
semiconducting material or a non-semiconducting material, depending
on the intended use of the device. Non-limiting examples of
semiconducting materials that may be used include silicon, silicon
carbide, silicon germanium, sapphire, aluminum arsenide, aluminum
phosphide, gallium arsenide, gallium phosphide, gallium nitride,
and combinations thereof. In one specific aspect, the semiconductor
substrate may be silicon. In another aspect, the semiconductor
substrate may be sapphire. Non-limiting examples of
non-semiconducting materials may include glass, metals, ceramics,
graphite, and combinations thereof.
[0056] A semiconductor layer 14 may be deposited on the
semiconductor substrate 12 using a variety of techniques known to
those of ordinary skill in the art. One example of such a technique
is MOCVD processes. The semiconductor layer 14 may comprise any
material that is suitable for forming electronic devices,
semiconductor devices, or the like. Many semiconductors are based
on silicon, gallium, indium, and germanium. However, suitable
materials for the semiconductor layer can include, without
limitation, silicon, silicon carbide, silicon germanium, gallium
arsenide, gallium nitride, germanium, zinc sulfide, gallium
phosphide, gallium antimonide, gallium indium arsenide phosphide,
aluminum phosphide, aluminum arsenide, aluminum gallium arsenide,
gallium nitride, boron nitride, aluminum nitride, indium arsenide,
indium phosphide, indium antimonide, indium nitride, and composites
thereof. In one aspect, however, the semiconductor layer can
comprise silicon, silicon carbide, gallium arsenide, gallium
nitride, gallium phosphide, aluminum nitride, indium nitride,
indium gallium nitride, aluminum gallium nitride, or composites of
these materials. In some additional embodiments, non-silicon based
devices can be formed such as those based on gallium arsenide,
gallium nitride, germanium, boron nitride, aluminum nitride,
indium-based materials, and composites thereof. In another
embodiment, the semiconductor layer can comprise gallium nitride,
indium gallium nitride, indium nitride, and combinations thereof.
In one specific aspect, the semiconductor material is gallium
nitride. In another specific aspect, the semiconductor material is
aluminum nitride. Other semiconductor materials which can be used
include Al.sub.2O.sub.3, BeO, W, Mo, c-Y.sub.2O.sub.3,
c-(Y.sub.0.9La.sub.0.1).sub.2O.sub.3, c-Al.sub.23O.sub.27N.sub.5,
c-MgAl.sub.2O.sub.4, t-MgF.sub.2, graphite, and mixtures thereof.
It should be understood that the semiconductor layer may include
any semiconductor material known, and should not be limited to
those materials described herein. Additionally, semiconductor
materials may be of any structural configuration known, for
example, without limitation, cubic (zincblende or sphalerite),
wurtzitic, rhombohedral, graphitic, turbostratic, pyrolytic,
hexagonal, amorphous, or combinations thereof. As has been
described, the semiconductor layer 14 may be deposited by any
method known to one of ordinary skill in the art. Various known
methods of vapor deposition can be utilized to deposit such layers
and that allow deposition to occur in a graded manner.
[0057] In one aspect of the present invention, the semiconductor
layer 14 may be gallium nitride (GaN). GaN semiconductor layers may
be useful in constructing LEDs and other semiconductor devices. In
some cases it may be beneficial to gradually transition between the
semiconductor substrate 12 and the semiconductor layer 14. For
example, gradually transitioning an indium nitride (InN)
semiconductor substrate into a GaN semiconductor layer may occur by
fixing the concentration of the N being vapor deposited and varying
the deposited concentration of Ga and of In such that a ratio of
Ga:In gradually transitions from about 0:1 to about 1:0. In other
words, the sources of Ga and In are varied such that as the In
concentration is decreased, the Ga concentration is increased. The
gradual transition functions to greatly reduce the lattice mismatch
observed when depositing GaN directly on InN.
[0058] In another aspect, the semiconductor layer 14 may be a layer
of aluminum nitride (AlN). The MN layer may be deposited onto the
semiconductor substrate 12 by any means known to one of ordinary
skill in the art. As with the GaN layer described above, gradually
transitioning between semiconductor layers may improve the
functionality of the semiconductor device. For example, in one
aspect MN may be deposited onto a semiconductor substrate of InN by
gradually transitioning the layer of InN into the layer of AlN.
Such a gradual transition may include, for example, gradually
transitioning the layer of InN into the layer of MN by fixing the
concentration of N being deposited and varying the deposited
concentration of In and of Al such that a ratio of In:Al gradually
transitions from about 0:1 to about 1:0. Such a gradual transition
may greatly reduce the lattice mismatch observed when depositing MN
on InN directly. Surface processing may be performed between any of
the deposition steps described in order to provide a smooth surface
for subsequent deposition. Such processing may be accomplished by
any means known, such as by chemical etching, polishing, buffing,
grinding, etc.
[0059] Returning to FIG. 1, an adynamic diamond layer 16 may be
deposited on the semiconductor layer 14. A description of the
adynamic diamond layer and the creation thereof are discussed
further herein. A support substrate 18 can then be deposited on the
adynamic diamond layer 16 in order to support the adynamic diamond
layer. The support substrate 18 can be any material that provides
support to the adynamic diamond layer 16. Non-limiting examples of
materials that may be used as support substrates may include
metals, glass, polymeric materials, resins, ceramics, etc. and
combinations thereof. The support substrate 18 may be coupled to
the adynamic diamond layer 16 by any known method. Examples of
methods of coupling may include, without limitation, vapor
deposition, adhesives, brazing, etc. In one aspect, for example,
the support substrate 18 may be vapor deposited onto the adynamic
diamond layer 16 by vapor deposition means. In another aspect, the
diamond layer 16 may be formed on the support substrate 18 and
subsequently glued or brazed to the semiconductor layer 14.
[0060] As has been described, various semiconductor devices are
contemplated. For example, FIG. 2 shows a specific aspect of the
present invention whereby the semiconductor device is an LED device
20. In one example of such a device, the semiconductor substrate
may be a sapphire substrate 22 having a semiconductor layer 24
deposited thereon, where the semiconductor layer is GaN, MN, or a
combination thereof. An adynamic diamond layer 26 is deposited on
the semiconductor layer 24, and a support substrate 28 is deposited
on the adynamic diamond layer 26 to provide support and
manipulation convenience. Such a configuration allows the direction
of the LED to be reversed as compared to present LEDs, such that
light generated in the semiconductor layer 24 can be emitted
primarily through the sapphire substrate 22 as shown at 29. Light
emission from such a configuration may be facilitated by applying a
reflector layer to the adynamic diamond layer prior to application
of the support substrate (not shown). Such a layer would allow
light emitted toward the support substrate to be reflected back
towards the sapphire substrate and from the device. Numerous
materials may be utilized to create a reflective layer, all of
which should be considered to be within the present scope. In one
example, however, a chromium layer can be sputtered onto the
adynamic diamond material to form such a reflective layer.
[0061] FIG. 3 shows a semiconductor device constructed as shown in
FIG. 1, but having the semiconductor substrate (not shown) removed
from the semiconductor layer 14. In this aspect, an additional
semiconductor layer 32 may be deposited onto the semiconductor
layer 14. The additional semiconductor layer 32 may be constructed
of any semiconductor material known, and may be deposited by any
known method, as has been described herein. Additionally, in one
aspect, the additional semiconductor layer 32 may be a plurality of
additional semiconductor layers. In one particular aspect of the
present invention the semiconductor and/or the additional
semiconductor layer can be nitride layers for use as LED
devices.
[0062] As they have become increasingly important in electronics
and lighting devices, LEDs continue to be developed that have ever
increasing power requirements. This trend of increasing power has
created cooling problems for these devices. These cooling problems
can be exacerbated by the typically small size of these devices,
which may render heat sinks with traditional aluminum heat fins
ineffective due to their bulky nature. Additionally, such
traditional heat sinks would block the emission of light if applied
to the light-emitting surface of the LED. The inventor has
discovered that depositing an adynamic diamond layer within the LED
package allows adequate cooling even at high power, while
maintaining a small LED package size. Additionally, in one aspect
the maximum operating wattage of an LED may be exceeded by drawing
heat from the semiconductor layers of the LED with an adynamic
diamond layer in order to operate the LED at an operating wattage
that is higher than the maximum operating wattage for that LED.
[0063] In another aspect, as shown in FIG. 4, a semiconductor
device constructed as in FIG. 1 can be used to construct an
acoustic filter 40 by first removing the semiconductor substrate
(not shown) from the semiconductor layer 14. In the case of SAW
filters, the semiconductor layer 14 may be a piezoelectric layer.
Interdigital transducers 42 can be coupled to the surface of the
piezoelectric semiconductor layer to form the SAW filter.
EXAMPLES
[0064] The following examples illustrate various techniques of
making a semiconductor device according to aspects of the present
invention. However, it is to be understood that the following are
only exemplary or illustrative of the application of the principles
of the present invention. Numerous modifications and alternative
compositions, methods, and systems can be devised by those skilled
in the art without departing from the spirit and scope of the
present invention. The appended claims are intended to cover such
modifications and arrangements. Thus, while the present invention
has been described above with particularity, the following Examples
provide further detail in connection with several specific
embodiments of the invention.
Example 1
[0065] A GaN LED crystal is formed on a sapphire substrate. An
adynamic diamond film is coated on top of the GaN layer. The
adynamic diamond film is deposited by microwave enhanced plasma CVD
with methane (1%) and hydrogen (99%) as the gas mixture (100 torr).
The adynamic diamond film is then sputter coated with Cr as a
reflector and brazed to a silicon support substrate. With such an
LED, light generated in the GaN layer is emitted primarily through
the sapphire substrate.
Example 2
[0066] An adynamic diamond layer is deposited onto a Si wafer as
described in Example 1. The adynamic layer is polished to a smooth
surface. A thin layer of Si is sputtered onto the adynamic layer. A
GaN LED crystal formed on a sapphire substrate is wafer bonded to
the thin layer of Si. Light generated in the GaN layer is thus
emitted primarily through the sapphire substrate.
Example 3
[0067] An adynamic diamond layer is deposited onto a Si wafer as
described in Example 1. The adynamic layer is polished to a smooth
surface. A thin layer of Si is sputtered onto the adynamic layer. A
GaN LED crystal formed on a sapphire substrate is wafer bonded to
the thin layer of Si using a gold-tin alloy to form a reflector to
more effectively direct light generated in the GaN layer through
the sapphire substrate.
[0068] Of course, it is to be understood that the above-described
arrangements are only illustrative of the application of the
principles of the present invention. Numerous modifications and
alternative arrangements may be devised by those skilled in the art
without departing from the spirit and scope of the present
invention and the appended claims are intended to cover such
modifications and arrangements. Thus, while the present invention
has been described above with particularity and detail in
connection with what is presently deemed to be the most practical
and preferred embodiments of the invention, it will be apparent to
those of ordinary skill in the art that numerous modifications,
including, but not limited to, variations in size, materials,
shape, form, function and manner of operation, assembly and use may
be made without departing from the principles and concepts set
forth herein.
* * * * *