U.S. patent application number 11/043684 was filed with the patent office on 2006-07-27 for boron-doped diamond semiconductor.
Invention is credited to Robert Linares.
Application Number | 20060163584 11/043684 |
Document ID | / |
Family ID | 36695834 |
Filed Date | 2006-07-27 |
United States Patent
Application |
20060163584 |
Kind Code |
A1 |
Linares; Robert |
July 27, 2006 |
Boron-doped diamond semiconductor
Abstract
First and second synthetic diamond regions are doped with boron.
The second synthetic diamond region is doped with boron to a
greater degree than the first synthetic diamond region, and in
physical contact with the first synthetic diamond region. In a
further example embodiment, the first and second synthetic diamond
regions form a diamond semiconductor, such as a Schottky diode when
attached to at least one metallic lead.
Inventors: |
Linares; Robert; (Sherborn,
MA) |
Correspondence
Address: |
SCHWEGMAN, LUNDBERG, WOESSNER & KLUTH, P.A.
P.O. BOX 2938
MINNEAPOLIS
MN
55402
US
|
Family ID: |
36695834 |
Appl. No.: |
11/043684 |
Filed: |
January 26, 2005 |
Current U.S.
Class: |
257/77 ;
257/E21.042; 257/E21.05; 257/E21.053; 257/E21.568; 257/E29.082;
257/E29.338; 438/931 |
Current CPC
Class: |
H01L 29/872 20130101;
H01L 29/1602 20130101; H01L 21/041 20130101; H01L 29/6603 20130101;
H01L 29/66037 20130101; H01L 21/263 20130101; H01L 21/76254
20130101 |
Class at
Publication: |
257/077 ;
438/931; 257/E29.338 |
International
Class: |
H01L 31/0312 20060101
H01L031/0312 |
Claims
1. A semiconductor device, comprising: a first synthetic diamond
region doped with boron; a second synthetic diamond region doped
with boron, the second synthetic diamond region doped with boron to
a greater degree than the first synthetic diamond region and in
physical contact with the first synthetic diamond region.
2. The semiconductor device of claim 1, further comprising a first
metal contact attached to the first synthetic diamond region and a
second metal contact attached to the second synthetic diamond
region.
3. The semiconductor device of claim 1, wherein the semiconductor
device comprises a Schottky diode.
4. The semiconductor device of claim 1, wherein at least one of the
first and second synthetic diamond regions is a synthetic
monocrystalline diamond.
5. The semiconductor device of claim 1, wherein at least one of the
first and second synthetic diamond regions comprises less than 1
ppm impurities not including a dopant.
6. The semiconductor device of claim 1, wherein at least one of the
first and second synthetic diamond regions has a thermal
conductivity greater than 2500 W/mK.
7. The semiconductor device of claim 1, wherein at least one of the
first and second synthetic diamond regions has a thermal
conductivity greater than 2700 W/mK.
8. The semiconductor device of claim 1, wherein at least one of the
first and second synthetic diamond regions has a thermal
conductivity greater than 3200 W/mK.
9. The semiconductor device of claim 1, wherein at least one of the
first and the second synthetic diamond regions is isotopically
enhanced with carbon-12 such that the resulting carbon-13
concentration is less than 1%.
10. The semiconductor device of claim 1, wherein at least one of
the first and second synthetic diamond regions is isotopically
enhanced with carbon-12 such that the resulting carbon-13
concentration is less than 0.1%.
11. The semiconductor device of claim 1, wherein at least one of
the first and second synthetic diamond regions is isotopically
enhanced with carbon-12 such that the resulting carbon-13
concentration is less than 0.01%.
12. The semiconductor device of claim 1, wherein at least one of
the first and second synthetic diamond regions has a nitrogen
concentration of less than 50 ppm.
13. The semiconductor device of claim 1, wherein at least one of
the first and second synthetic diamond regions has a nitrogen
concentration of less than 10 ppm.
14. The semiconductor device of claim 1, wherein at least one of
the first and second synthetic diamond regions has a nitrogen
concentration of less than 5 ppm.
15. The semiconductor device of claim 1, wherein the first and
second diamond regions are formed by: implanting hydrogen in a base
diamond region doped with boron to a first degree; forming a grown
diamond region on the base diamond region by chemical vapor
deposition, the grown diamond region being doped with boron to a
second degree; and separating the grown diamond region and a
portion of the base diamond region by heating the base diamond
region to cause separation at the hydrogen implant layer.
16. The semiconductor device of claim 15, wherein the base diamond
region is the first synthetic diamond region and the grown diamond
region is the second synthetic diamond region.
17. The semiconductor device of claim 15, wherein the base diamond
region is the second synthetic diamond region and the grown diamond
region is the first synthetic diamond region.
18. A method of fabricating a boron-doped diamond semiconductor
device, comprising: growing a first synthetic diamond region doped
with boron; implanting hydrogen into the first synthetic diamond
region; growing a second synthetic diamond region doped with boron
in a density different that the boron doping density of the first
synthetic diamond region, the second synthetic diamond region grown
on the first synthetic diamond region; and heating at least the
first synthetic diamond region to separate the first synthetic
diamond region at the depth of hydrogen implant.
19. The method of claim 18, wherein the more heavily boron-doped
synthetic diamond region comprises an anode of a Schottky diode,
and the less heavily boron-doped synthetic diamond region comprises
a cathode of a Schottky diode.
20. The method of claim 18, further comprising forming a first
metal contact attached to the first synthetic diamond region and a
second metal contact attached to the second synthetic diamond
region.
21. The method of claim 18, wherein at least one of the first and
second synthetic diamond regions are fabricated as a
monocrystalline synthetic diamond via chemical vapor
deposition.
22. The method of claim 18, wherein at least one of the first and
second synthetic diamond regions comprises less than 1 ppm
impurities, impurities not including a dopant.
23. The method of claim 18, wherein at least one of the first and
second synthetic diamond regions comprises less than 1 ppm
nitrogen.
23. The method of claim 18, wherein at least one of the first and
second synthetic diamond regions has a thermal conductivity greater
than 2500 W/mK.
24. The method of claim 18, wherein at least one of the first and
second synthetic diamond regions has a thermal conductivity greater
than 2700 W/mK.
25. The method of claim 18, wherein at least one of the first and
second synthetic diamond regions has a thermal conductivity greater
than 3200 W/mK.
26. The method of claim 18 wherein at least one of the first and
the second synthetic diamond regions is isotopically enhanced with
carbon-12 such that the resulting carbon-13 concentration is less
than 1%.
27. The method of claim 18, wherein at least one of the first and
second synthetic diamond regions is isotopically enhanced with
carbon-12 such that the resulting carbon-13 concentration is less
than 0.1%.
28. The method of claim 18, wherein at least one of the first and
second synthetic diamond regions is isotopically enhanced with
carbon-12 such that the resulting carbon-13 concentration is less
than 0.01%.
29. The method of claim 18, wherein at least one of the first and
second synthetic diamond regions has a nitrogen concentration of
less than 50 ppm.
30. The method of claim 18, wherein at least one of the first and
second synthetic diamond regions has a nitrogen concentration of
less than 10 ppm.
31. The method of claim 18, wherein at least one of the first and
second synthetic diamond regions has a nitrogen concentration of
less than 5 ppm.
32. An integrated circuit, comprising: a first diamond region doped
with boron; a second diamond region doped with boron, the second
synthetic diamond region doped with boron to a greater degree than
the first synthetic diamond region and in physical contact with the
first synthetic diamond region
33. The integrated circuit of claim 32, further comprising a
diamond substrate.
34. The integrated circuit of claim 33, wherein the diamond
substrate is a monocrystalline synthetic diamond substrate.
35. The integrated circuit of claim 31, wherein at least one of the
first and second diamond regions is a synthetic monocrystalline
diamond.
36. The integrated circuit of claim 31, wherein at least one of the
first and the second diamond regions is isotopically enhanced with
carbon-12 such that the resulting carbon-13 concentration is less
than 1%.
37. The integrated circuit of claim 31, wherein at least one of the
first and second diamond regions is isotopically enhanced with
carbon-12 such that the resulting carbon-13 concentration is less
than 0.1%.
38. The integrated circuit of claim 31, wherein at least one of the
first and second diamond regions is isotopically enhanced with
carbon-12 such that the resulting carbon-13 concentration is less
than 0.01%.
39. The integrated circuit of claim 31, wherein at least one of the
first and second diamond regions has a nitrogen concentration of
less than 50 ppm.
40. The integrated circuit of claim 31, wherein at least one of the
first and second diamond regions has a nitrogen concentration of
less than 10 ppm.
41. The integrated circuit of claim 31, wherein at least one of the
first and second diamond regions has a nitrogen concentration of
less than 5 ppm.
42. An electronic device, comprising: a synthetic diamond
semiconductor element comprising a first region doped with boron,
and further comprising a second region doped with boron, the second
synthetic diamond region doped with boron to a greater degree than
the first synthetic diamond region and in physical contact with the
first synthetic diamond element region.
43. The electronic device of claim 42, wherein the synthetic
diamond semiconductor element comprises a Schottky diode.
44. The electronic device of claim 42, wherein the synthetic
diamond semiconductor element comprises an integrated circuit.
45. The electronic semiconductor device of claim 44, wherein the
integrated circuit further comprises a synthetic monocrystalline
diamond substrate.
Description
FIELD OF THE INVENTION
[0001] The invention relates generally to diamond fabrication, and
more specifically to fabricating boron-doped diamond semiconductor
devices.
BACKGROUND OF THE INVENTION
[0002] A wide variety of semiconductor devices are used as basic
electronic building blocks to form electronic devices from
computers to cellular telephones, home entertainment systems, and
automobile control systems. Other devices use semiconductors for
purposes not related to computing or processing power, such as
audio amplifiers, industrial control systems, and for other such
purposes.
[0003] Modern semiconductors are typically based on silicon, with
various elements doped to change their electrical properties. For
example, doping silicon with phosphorous creates a surplus of
electrons resulting in n-type semiconductor material due to the
fifth valence electron not present in silicon, which has only four
valence electrons. Similarly, doping silicon with boron creates
p-type silicon having a surplus of "holes", or an absence of
electrons, because boron has only three valence electrons which is
one fewer than silicon.
[0004] When n-type and p-type silicon are in contact with one
another, electricity flows in one direction across the junction
more easily than in the other direction. More complex
configurations of n-type and p-type material can be assembled to
form various types of transistors, integrated circuits, and other
such devices.
[0005] But, the performance of certain semiconductor devices is
limited by the properties inherent in the semiconductor materials
used. For example, a processor's speed is limited by the amount of
power that can be dissipated in the transistors and other devices
that make up the processor integrated circuit, which can literally
melt if operated too fast. Reduction in size is also limited,
because as more transistors dissipating a certain amount of power
are packed into a smaller area, the amount of heat dissipated in a
certain area increases. Even simple devices such as diodes used in
high-frequency, high-power applications suffer from power
limitations, since the physical size of an individual transistor or
diode is typically very small.
[0006] Semiconductor devices enabling greater power dissipation and
higher semiconductor device densities are desirable to provide
higher performance, smaller electrical devices.
SUMMARY
[0007] The present invention provides in one example embodiment
first and second synthetic diamond regions doped with boron. The
second synthetic diamond region is doped with boron to a greater
degree than the first synthetic diamond region, and in physical
contact with the first synthetic diamond region. In a further
example embodiment, the first and second synthetic diamond regions
form a diamond semiconductor, such as a Schottky diode.
BRIEF DESCRIPTION OF THE FIGURES
[0008] FIG. 1 shows a boron-doped diamond seed crystal with a
hydrogen ion implant layer, consistent with an example embodiment
of the present invention.
[0009] FIG. 2 shows a boron-doped diamond seed crystal with grown
boron-doped diamond, consistent with an example embodiment of the
present invention.
[0010] FIG. 3 shows a boron-doped diamond seed crystal with grown
diamond separated at a hydrogen implant level, consistent with an
example embodiment of the present invention.
[0011] FIG. 4 shows a Schottky diode formed from the boron-doped
diamond seed crystal with grown boron-doped diamond, consistent
with an example embodiment of the present invention.
[0012] FIG. 5 shows a method of forming a boron-doped diamond
semiconductor, consistent with an example embodiment of the present
invention.
[0013] FIG. 6 shows an integrated circuit having first and second
boron-doped diamond semiconductor regions, consistent with an
example embodiment of the present invention.
[0014] FIG. 7 shows an electronic device utilizing a boron-doped
diamond semiconductor, consistent with an example embodiment of the
present invention.
DETAILED DESCRIPTION
[0015] In the following detailed description of example embodiments
of the invention, reference is made to the accompanying drawings
which form a part hereof, and in which is shown by way of
illustration specific sample embodiments in which the invention may
be practiced. These embodiments are described in sufficient detail
to enable those skilled in the art to practice the invention, and
it is to be understood that other embodiments may be utilized and
that logical, mechanical, electrical, and other changes may be made
without departing from the substance or scope of the present
invention. The following detailed description is, therefore, not to
be taken in a limiting sense, and the scope of the invention is
defined only by the appended claims.
[0016] One example of the invention provides first and second
synthetic diamond regions doped with boron. The second synthetic
diamond region is doped with boron to a greater degree than the
first synthetic diamond region, and in physical contact with the
first synthetic diamond region. In a further example embodiment,
the first and second synthetic diamond regions form a diamond
semiconductor, such as a Schottky diode.
[0017] FIGS. 1-4 illustrate a method of producing a monocrystalline
synthetic diamond Schottky diode, which is one example of a diamond
semiconductor device such as can be produced using the present
invention. FIG. 1 illustrates a diamond seed crystal that is
heavily doped with boron, which has only three valence electrons
relative to carbon's four valence electrons, making the diamond a
strongly p-type semiconductor material. The absence of electrons in
sites in the diamond that contain boron leaves a "hole" that is
receptive to electrons, making what is in effect a mobile positive
charge. The negatively charged boron atom is fixed in the diamond
lattice, meaning that the boron atoms cannot move but contribute
holes as electron receptors to the electrical conduction
process.
[0018] In some examples, the boron is grown into the diamond as the
diamond is formed by chemical vapor deposition or via another
process, while other examples use ion implantation to implant boron
into diamond, whether the diamond is synthetic or naturally
occurring. The diamond contains boron doping through at least a top
region of the seed diamond 101 extending a half micron to a few
microns, such that a top layer has a relatively uniform
distribution of boron atoms distributed to a desired density.
[0019] The seed 101 is polished to have a flat top surface, and the
edges of the seed are trimmed such as with a laser or cutting tool,
and are cleaned, etched, and polished. Hydrogen atoms are then
implanted to a desired depth, as is shown in FIG. 1 at 102. The
hydrogen atoms are implanted under various conditions in various
examples, but in one example are implanted at an angle of ten
degrees relative to the diamond surface, and at a dose rate of
approximately one microamp per square centimeter. The electrons are
implanted with an energy of approximately 200 KeV, until the total
dose of approximately ten to the seventeenth atoms per square
centimeter are implanted into the diamond 101. Varying the
parameters of the hydrogen implant will vary the depth and density
of the resulting hydrogen implant layer. The hydrogen implant layer
is shown as the dotted layer 102 of FIG. 1.
[0020] Once the hydrogen implantation into the boron-doped diamond
seed is completed, more diamond is grown on the seed, such as via a
chemical vapor deposition plasma reactor. Various technologies that
can be employed for diamond formation in other examples, including
microwave plasma reactors, DC plasma reactors, RF plasma reactors,
hot filament reactors, and other such technologies. The formation
of synthetic diamond can be achieved through a variety of methods
and apparatus, such as that described in U.S. Pat. No. 6,582,513,
titled "System and Method for Producing Synthetic Diamond", which
is incorporated by reference.
[0021] The diamond grown in one example is a monocrystalline
synthetic diamond uses a stream of gas, such as methane or other
gas, to provide the precursor material for the plasma reactor to
produce a plasma that precipitates to form diamond. The gas in some
examples or in some layers of the diamond contains various
impurities, such as boron dopants or various isotopes of carbon.
For example, diamonds having a greater than average purity of
carbon-12 and a corresponding reduced concentration of carbon-13
isotopes are known as isotopically enhanced, and are particularly
thermally conductive. This makes them well-suited for applications
such as semiconductor device fabrication, enabling higher power and
higher density than can otherwise be achieved. Isotopic enhancement
of the diamond CVD precursor gases with carbon-12 can result in a
diamond having significantly less than the typical 1.1% carbon-13
concentration, resulting in thermal conductivity as high as 3300
W/mK. Other examples of methods of producing synthetic diamond with
high thermal conductivity include growing diamond in a low nitrogen
environment, growing synthetic diamond in an environment rich in
hydrogen, and using boron doping resulting in an increase in
thermal conductivity.
[0022] FIG. 2 shows the see diamond of FIG. 1 with a hydrogen
implant layer 201 that has another synthetic diamond layer 202 that
is boron-doped grown on the surface that was implanted with
hydrogen. In some examples, the seed 201 is polished flat before
hydrogen implantation or at some other point before growth of the
second synthetic diamond region 202, and is trimmed to a desired
size or shape such as by laser cutting before or after growth of
the second synthetic diamond region. The top layer is grown to a
desired thickness, such as 100 microns in one example, and is then
polished and cut to form the diamond assembly shown in FIG. 2.
[0023] The assembly of FIG. 2 is then heated to a temperature
sufficient to cause separation of the first diamond region 101 at
the hydrogen implant level, resulting in a portion of the seed
diamond region 101's becoming detached with the grown synthetic
diamond region 202. This operation results in a seed diamond 301
that is somewhat smaller than the original seed diamond 101, due to
the more heavily boron-doped diamond portion 302 that is removed
with the more lightly boron-doped portion 303. The resulting
structure of 302 and 303 forms the semiconductor portion of a
Schottky diode, which is able to operate at particularly high
voltage and power levels due to the characteristics of diamond when
compared to other semiconductor materials such as silicon. In other
examples, the grown region will be more heavily doped with boron
than the seed region, the thicknesses of the diamond regions will
differ, and other structural and design changes will be made.
[0024] FIG. 4 shows the diamond assembly formed by 302 and 303 in
FIG. 3 that was lifted off the diamond seed region at 401, with
electrical leads attached at 402 and 403. The metal attached is
selected based on the metal's work function or fermi function and
the desired characteristics of the Schottky diode, and will
typically be a metal such as aluminum or platinum. This forms a
completed Schottky diode, which is similar to other types of diode
in its ability to rectify some signals, or to pass current in only
one direction under certain circumstances. Looking at the Schottky
diode of FIG. 4, the terminal 403 is known as the anode, and
terminal 402 is known as the cathode. When the anode is at a
potential that is higher than that of the cathode by a certain
voltage level, current will flow through the diode, but when the
anode is lower in potential or voltage than the cathode current
doesn't flow through the diode. This property makes a diode useful
for a wide variety of electronic applications, including detection,
filtering, and shaping electrical signals.
[0025] The rectifying portion of the Schottky diode is actually the
metal-to diamond semiconductor contact, rather than the interface
between semiconductor materials as is the case in most other types
of diodes such as p-n semiconductor diodes. The theory of Schottky
diode operation is well-understood but relatively complex, and
results in a number of significant advantages over regular
semiconductor diodes for many applications. The forward voltage
drop across a Schottky diode is typically much less than across a
typical p-n junction semiconductor diode, with typical values of
0.2 Volts drop across a Schottky diode and 0.6-0.7 Volts drop
across a silicon p-n junction diode. The capacitance across a
Schottky diode is also significantly lower, and the carrier
recombination at the metal interface forming the Schottky diode
barrier region is significantly faster than in p-n semiconductor
junctions, on the order of ten picoseconds. This makes Schottky
diodes particularly well-suited for applications such as
high-frequency detection, mixing, and other such applications. The
low noise characteristics of Schottky diodes relative to
semiconductor p-n junction diodes further makes them desirable for
use in low-level detection applications, such as radar or other
radio detection.
[0026] FIG. 5 is a flowchart of a method of making a boron-doped
diamond semiconductor device such as that of FIG. 4. At 501, a
boron-doped seed diamond is created. This can be achieved by ion
implantation into a natural or synthetic diamond, by growing a
synthetic diamond in an environment that is rich in boron, or by
any other suitable method. Grown diamond can be produced by high
pressure high temperature (HPHT) methods, by chemical vapor
deposition, or by any other suitable method. The boron-doped seed
diamond surface is polished at 502, to prepare a flat diamond
crystal surface of a desired crystal orientation. For example, the
diamond may be polished in the 100 plane, tilted two degrees toward
the 110 plane, to produce a polished surface slightly off the 100
plane of the diamond. The edges of the seed may be cut and various
other facets are polished or shaped in various examples, and the
surfaces are cleaned with an acid wash, water rinse, and solvent
dry.
[0027] Next, an implantation angle, energy, and dose are selected,
and hydrogen ion implantation is performed at 503. The implantation
parameters are configured to implant a selected density of hydrogen
atoms at a selected depth in the seed diamond, as shown and
described in FIG. 1. After hydrogen implantation, the implanted
seed diamond is used as a seed for growing additional diamond, such
as by chemical vapor deposition. The grown diamond in some examples
includes either a higher or lower boron concentration than the seed
diamond, as shown and described in FIG. 2. The diamond is grown
until a desired thickness is reached, such as 500 microns
thickness, or between 10 and 15,000 microns thick.
[0028] Once the growth process is complete, the diamond assembly is
removed from the grower, and edges are trimmed with a laser cutter
at 505. In other examples, the edges are trimmed using other
methods, and may be polished or ground. The edges of the seed are
thereby also trimmed to desired dimensions, such as back to the
original seed dimensions before growth on top of the seed diamond
region.
[0029] The resulting diamond assembly is heated in a non-oxidizing
environment, such as in hydrogen or an inert gas, to an elevated
temperature designed to cause the seed diamond region of the
diamond assembly to separate at the area of hydrogen implantation.
This separation occurs in one example at about 1200 degrees
Celsius, while in other examples occurs within a range of 1100 to
2400 degrees Celsius. Once the seed and the grown diamond-seed
diamond assembly separate, the grown diamond-see diamond assembly
remains, as is shown in FIG. 3, with a portion of the seed diamond
above the hydrogen implant layer attached to the grown diamond. The
separation occurs spontaneously at elevated temperatures in some
examples, but is cause by application of pressure across the
hydrogen implant layer in other examples.
[0030] The result is a boron-doped semiconductor device that can be
trimmed and polished further at 507, and that can be attached to
wire leads and packaged for use as a semiconductor device as is
shown at 509.
[0031] Other embodiments of semiconductor devices consistent with
various embodiments of the present invention include forming an
integrated circuit, as is shown in FIG. 6. This figure shows
generally a diamond semiconductor substrate at 601, which has at
least a region or portion 602 that is boron-doped. A second region
603 is grown, implanted, or otherwise formed in contact with the
diamond region 602, but with a different boron doping density. This
forms the semiconductor portion of a Schottky diode, but similar
processes can be used to form transistors and various other
components. The elements 602 and 603 are coupled to a circuit using
metallic wire having an appropriate work function, and in further
examples are connected using polysilicon or other conductor or
semiconductor elements to other portions of the integrated
circuit.
[0032] FIG. 7 illustrates an example of an electronic device that
may be constructed, consistent with some example embodiments of the
present invention. A radar apparatus 701 uses Schottky diodes for
low-level, high-frequency radio detection, and for mixing in
further example applications such as Doppler radar. The electronic
device benefits from the increased performance possible with
boron-doped diamond semiconductors, such as improved power
handling, higher density, and higher performance relative to
traditional semiconductors such as silicon.
[0033] Boron-doped diamond is also distinct from silicon-based
semiconductors in that it is largely transparent, with a bluish
tint. This makes boron-doped diamonds particularly well-suited for
applications such as blue LED or laser semiconductor devices in
configurations where light is emitted from other than an external
surface of a semiconductor junction, in addition to other
applications such as traditional LED or laser diodes.
[0034] Schottky barrier junctions are further usable in a variety
of applications other than Schottky diodes, including in use in
bipolar junction transistors where a Schottky junction is located
between the base and collector of the transistor. This prevents the
transistor from saturating too deeply, resulting in faster
switching times for the transistor. Metal-semiconductor field
effect transistors (MESFETs) also use a reverse-biased Schottky
barrier to provide the depletion region in the transistor, ans
works similarly to a JFET. Still other devices, including high
electron mobility transistors (HEMTs) use Schottky barriers in a
heterojunction device to provide extremely high conductance in a
transistor.
[0035] It is anticipated that the methods and devices described
here will apply not only th Schottky diodes and related devices,
but to other semiconductors, integrated circuits, and electronic
devices. Although specific embodiments have been illustrated and
described herein, those of ordinary skill in the art will
appreciate that a variety of arrangements which are calculated to
achieve the same purpose may be substituted for the specific
embodiments shown. This application is intended to cover any
adaptations or variations of the invention. It is intended that
this invention be limited only by the claims, and the full scope of
equivalents thereof.
* * * * *