U.S. patent application number 12/813146 was filed with the patent office on 2010-09-30 for apparatus for and method of continuous hts tape buffer layer deposition using large scale ion beam assisted deposition.
This patent application is currently assigned to SUPERPOWER, INC.. Invention is credited to Srinivas Sathiraju, Venkat Selvamanickam.
Application Number | 20100248970 12/813146 |
Document ID | / |
Family ID | 33540815 |
Filed Date | 2010-09-30 |
United States Patent
Application |
20100248970 |
Kind Code |
A1 |
Selvamanickam; Venkat ; et
al. |
September 30, 2010 |
APPARATUS FOR AND METHOD OF CONTINUOUS HTS TAPE BUFFER LAYER
DEPOSITION USING LARGE SCALE ION BEAM ASSISTED DEPOSITION
Abstract
The present invention is a high-throughput ion beam assisted
deposition (IBAD) system and method of utilizing such a system that
enables continuous deposition of thin films such as the buffer
layers of HTS tapes. The present invention includes a
spool-to-spool feed system that translates a metal substrate tape
through the IBAD system as the desired buffer layers are deposited
atop the translating substrate tape using an e-beam evaporator
assisted by an ion beam. The system further includes a control and
monitor system to monitor and regulate all necessary system
parameters. The present invention facilitates deposition of a
high-quality film over a large area of translating substrate.
Inventors: |
Selvamanickam; Venkat;
(Wynantskill, NY) ; Sathiraju; Srinivas;
(Riverside, OH) |
Correspondence
Address: |
LARSON NEWMAN & ABEL, LLP
5914 WEST COURTYARD DRIVE, SUITE 200
AUSTIN
TX
78730
US
|
Assignee: |
SUPERPOWER, INC.
Schenectady
NY
|
Family ID: |
33540815 |
Appl. No.: |
12/813146 |
Filed: |
June 10, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10609250 |
Jun 26, 2003 |
7758699 |
|
|
12813146 |
|
|
|
|
Current U.S.
Class: |
505/310 ;
427/62 |
Current CPC
Class: |
C23C 14/562 20130101;
C23C 14/541 20130101; C23C 14/083 20130101; C23C 14/54
20130101 |
Class at
Publication: |
505/310 ;
427/62 |
International
Class: |
H01L 39/24 20060101
H01L039/24 |
Claims
1. A process for continuous deposition of a coating of an HTS tape,
comprising: loading a substrate into a deposition chamber;
translating the substrate through the deposition chamber;
depositing a coating material from a deposition source on the
substrate to thereby form the coating while translating the
substrate, the coating being a buffer layer over which an HTS layer
is formed, the buffer layer having a biaxial texture; impinging an
ion beam from an ion source on the substrate during depositing;
monitoring the biaxial texture of the coating during depositing;
and adjusting the power level of at least one of the ion source and
the deposition source during depositing based on the monitoring of
biaxial texture.
2. The process of claim 1, wherein the buffer layer has an in-plane
texture of not greater than 20 degrees.
3. The process of claim 2, wherein the buffer layer has an in-plane
texture of not greater than 15 degrees.
4. The process of claim 3, wherein the buffer layer has an in-plane
texture of not greater than 14 degrees.
5. The process of claim 1, wherein the coating material is
generated by vaporizing a material source in the deposition
chamber, vaporization being carried out by energizing an energy
source.
6. The process of claim 5, wherein the energy source is selected
from the group consisting of electron beam energy, ion beam energy,
and magnetron energy.
7. The process of claim 1, wherein the substrate is translated
through the deposition chamber by a reel-to-reel system.
8. The process of claim 1, wherein a substrate block and the
substrate are in a heat transfer relationship, the substrate block
being maintained at a temperature below 50.degree. C.
9. The process of claim 1, wherein the tape is translated through
the deposition chamber at a speed within a range of about 0.4 to
300 meters/hour.
10. The process of claim 1, wherein the coating material is
selected from the group consisting of MgO and YSZ.
11. The process of claim 1, wherein the coating material is
deposited with the assist of an ion beam.
12. The process of claim 1, wherein the substrate comprises a
nickel alloy.
13. A process for continuous deposition of a coating of an HTS
tape, comprising: loading a substrate into a deposition chamber;
translating the substrate through the deposition chamber;
depositing a coating material from a deposition source on the
substrate to thereby form the coating while translating the
substrate, the coating being a buffer layer over which an HTS layer
is formed, the buffer layer having a biaxial texture; impinging an
ion beam from an ion source on the substrate during depositing;
monitoring the biaxial texture of the coating, a number of ions
from the ion beam impinging on the substrate, and a thickness of
the coating during depositing; and adjusting the power level of at
least one of the ion source and the deposition source during
depositing based on the monitoring of biaxial texture.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] The present application is a continuation of U.S. patent
application Ser. No. 10/609,250, filed Jun. 26, 2003, entitled
"APPARATUS FOR AND METHOD OF CONTINUOUS HTS TAPE BUFFER LAYER
DEPOSITION USING LARGE SCALE ION BEAM ASSISTED DEPOSITION," naming
inventors Venkat Selvamanickam and Srinivas Sathiraju, which
application is incorporated by reference herein in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to ion beam assisted
deposition (IBAD) system and method of utilizing such a system.
More specifically, the present invention relates to large-scale ion
beam assisted deposition of thin films, such as the buffer layers
of high-temperature superconducting (HTS) tapes.
BACKGROUND OF THE INVENTION
[0003] Wire forms the basic building block of the world's electric
power system, including transformers, transmission and distribution
systems, and motors. The discovery of revolutionary HTS compounds
in 1986 led to the development of a radically new type of wire for
the power industry; this discovery is the most fundamental advance
in wire technology in more than a century. However, to date only
short samples of the HTS tape used in the manufacture of
next-generation HTS wires have been fabricated at high performance
levels. In order for HTS technology to become commercially viable
for use in the power generation and distribution industry, it will
be necessary to develop techniques for continuous, high-throughput
production of HTS tape.
[0004] IBAD, such as is described in Neumuller et al., U.S. Pat.
No. 6,258,472, dated Jul. 10, 2001, and entitled Product Having a
Substrate of a Partially Stabilized Zirconium Oxide and a Buffer
Layer of a Fully Stabilized Zirconium Oxide, and Process for its
Production has shown great promise in creating desirable buffer
layer characteristics as a support for a functional layer of a
ceramic superconducting material, such as
yttrium-barium-copper-oxide (YBCO) atop the buffering layers of
yttrium-stabilized zirconia (YSZ) and cerium oxide (CeO.sub.2).
During IBAD, a vacuum-deposition process that combines physical
vapor deposition (PVD) with ion-beam bombardment occurs: a vapor of
coating atoms is generated with an electron-beam evaporator and
deposited on a substrate. Ions are simultaneously extracted from a
plasma and accelerated into the growing PVD film at energies of
several hundred to several thousand electronvolts (eV). The ions
impart substantial energy to the coating and coating/substrate
interface. This achieves the benefits of substrate heating (which
generally provides a denser, more uniform film) without
significantly heating the substrate material and degrading bulk
properties. The ions also interact with the coating atoms, driving
them into the substrate and producing a graded material interface,
which enhances adhesion. These factors combine to allow the
deposition of uniform, adherent, low-stress films of virtually any
coating material on most substrates, including the buffer layers of
HTS tapes. In addition, concurrent ion beam bombardment of a
growing film has been shown to impart biaxial texture. IBAD has
been specifically used for this purpose to achieve a high-degree of
biaxial texture in materials used as buffer layers for HTS
tapes.
[0005] While such prior art IBAD processes are well known for their
rapid deposition rates, they are also prone to process variations.
The high-throughput continuous deposition of buffer layers
necessary to enable cost-effective and, consequently, widespread
adaptation of HTS materials in the electricity
transmission/distribution industry necessitates deposition runs
that can take upwards of one week to complete, during which time
process variations sufficiently severe to disrupt the process are
likely to occur. HTS films are extremely sensitive to such
variations in system parameters and conditions such as chamber
pressure and temperature. As a result, prior art HTS materials have
been successfully fabricated only on a small scale.
[0006] It is thus an object of this invention to provide a
high-throughput IBAD system and method for its use that enables
continuous deposition of high quality thin films such as the buffer
layers of HTS tapes.
BRIEF SUMMARY OF THE PRESENT INVENTION
[0007] The present invention is a high-throughput IBAD or other
deposition system and method of utilizing such a system that
enables deposition of thin films such as the buffer layers of HTS
tapes on a continuously moving substrate.
[0008] The present invention includes a spool-to-spool feed system
that translates a metal substrate tape through the IBAD system as
the desired buffer layers are deposited atop the translating
substrate tape using an e-beam evaporator assisted by an ion beam.
The system further includes a control and monitor system to monitor
and regulate all necessary system parameters.
[0009] The consistency of application of the thin film coating by
the use of a cooling block having a minor but important curvature
on the surface in contact with the moving substrate. An essential
part of the innovative systems resides in the introduction of
oxygen through orifices in the contact surface of the cooling
block.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1A is a block diagram of the IBAD system of the present
invention depicting the functional relationships between the
subsystems of the IBAD system.
[0011] FIG. 1B is a front view of the IBAD system of the present
invention.
[0012] FIG. 1C is a cross-sectional view of the IBAD system taken
along line A-A of FIG. 1B.
[0013] FIG. 1D is a cross-sectional view of the IBAD system taken
along line B-B of FIG. 1B.
[0014] FIG. 1E is a cross-sectional view of the IBAD system taken
along line C-C of FIG. 1B.
[0015] FIG. 2 illustrates a method of use of the IBAD system of the
present invention.
[0016] FIG. 3 is a cross sectional view of the substrate block FIG.
4 is a graph of the in-plane texture of a coated substrate showing
the difference when oxygen is injected.
[0017] FIG. 5 is a graph of the in-plane texture of the coated
substrate at various rates of oxygen flow.
DETAILED DESCRIPTION OF THIS INVENTION
[0018] FIG. 1A illustrates a logical representation of the IBAD
system 100 of the present invention in block diagram form,
depicting the functional relationships between each subsystem. The
IBAD system 100 includes a controller 118 a vacuum pump 112, a DC
E-beam source 114, an ion source 116, a reel system 120, a sensor
system 122 and a gas supply 124.
[0019] The vacuum pump 112 is a commercially available vacuum pump
capable of maintaining a vacuum of pressure in the order of
magnitude of 10.sup.-5, preferably 10.sup.-7 Ton. One example of
such a pump is an APD Cryogenics, [1833 Vultee Street, Allentown,
Pa. 18103] Marathon 16 cryopump.
[0020] The DC E-beam source 114 is a commercially available
electron source having the capabilities to dynamically control the
trajectory of the electrons. One example of a commercially
available E-beam source is a Thermionics source manufactured by
Thermionics Vacuum Products [231 Otto St., Port Townsend, Wash.
98368] and having a power rating of 10 kW watts.
[0021] The ion source 116 is a commercially available ion source.
One example is a Veeco-Ion Tech, RF 6*22 linear source,
manufactured by Veeco-Ion Tech, Inc. [2330 East Prospect Rd., Fort
Collins, Colo. 80525] and using a voltage of 1990 volts and having
a power rating of 500 W.
[0022] The controller 118 is a controller with a plurality of
inputs and outputs that meet the requirements of the peripherals
described in FIG. 1B. The controller 118 may be a micro-controller
or a PC with appropriate hardware & software.
[0023] The reel system 120 is a tape transport system that serves
to translate an extended length of tape through the IBAD system 100
and to take up tape on which an HTS film has been deposited. The
reel system 120 is described in FIG. 1B, FIG. 1C, FIG. 1D and FIG.
1E.
[0024] The sensor system 122 includes sensors disposed in and
around the IBAD chamber that monitor process conditions and
parameters of the HTS tape deposition system 100, as described
further in FIG. 1B. The sensor system 122 may include a pressure
gauge, film thickness sensor, faraday cup, and a
temperature-sensing unit, as described below.
[0025] The gas supply 124 is a gas injection system that provides
gas at a flow rate to meet process specifications stored in the
controller 118. Supplied gases may include argon, nitrogen and
oxygen. The gas supply 124 is described below in FIG. 1B.
[0026] Functional connections exist between the vacuum pump 112,
the DC E-beam source 114, the RF ion source 116, the reel system
120, the sensor system 122, the gas supply 124, and the IBAD
chamber (described below). Similarly, the controller 118 is
electrically coupled to the vacuum pump 112, the DC E-beam source
114, the ion source 116, the reel system 120, the sensor system 122
and the gas supply 124.
[0027] FIG. 1B illustrates the IBAD system 100, in accordance with
the invention that includes IBAD chamber 110, a tank farm 126, a
valve/flowmeter 134, a pipe 128, a valve/flowmeter 136, a pipe 130,
a valve/flowmeter 138, a pipe 132, a coolant line 140, a support
142, a substrate block 144, a faraday cup 146, a film thickness
sensor 148, a pressure gauge 150, a temperature unit 152, an MS
(Metal Substrate) spool 154, a collector spool 156, a protective
tape 164, a tape 160, an IBAD-buffered spool 162, a protective tape
158, an applicator spool 166, a strain gauge 168, a detector 170, a
valve 172, vacuum pump 112, an evaporation source 174, a gas line
166, and DC E-beam source 114.
[0028] The IBAD chamber 110 is a pressurized vacuum chamber. The
IBAD chamber 110 may be constructed of any non-corroding metal such
as 304 stainless steel. The IBAD Chamber 110 includes all the
necessary gaskets, seals and seal plates to maintain a vacuum to
the order of 10.sup.-7 Torr.
[0029] The pressure gauge 150 is a device capable of accurately
measuring pressure ranging from 10.sup.-9 Ton to 1000 Ton such as a
Pirani gauge or ionization gauge. The pressure gauge 150 is an
element of the sensor system 122.
[0030] The tank farm 126 is a series of gas supply tanks and is a
part of the gas supply 124 subsystem. Supplied gases may include
argon, nitrogen and oxygen.
[0031] The valve/flowmeters 134, 136, and 138 are elements of the
gas supply 124 subsystem that consist of gas flow units containing
electrically controlled gas flow valves along with corresponding
flowmeters such as manometers to control/monitor gas flow and
partial pressures. Examples of such a valve and flowmeter are MKS
1179 and MKS Baratron respectively manufactured by MKS Instruments,
Inc. [789 Grove Rd., Suite 111 Richardson, Tex. 75081].
[0032] The pipes 128, 130, and 132 are gas supply lines that are
included in the gas supply 124 subsystem. The pipes 128, 130, and
132 may be constructed from a variety of materials such as
stainless steel.
[0033] The coolant line 140 is a pipe containing a supply line and
a return line through which a coolant such as water or a glycol
solution is transported. The coolant line 140 may be constructed
from any of a number of materials such as stainless steel or
copper.
[0034] The support 142 is a metal support having appropriate
mounting brackets at both longitudinal ends, as well as an internal
passageway capable of containing piping and/or wiring. The support
142 may be constructed from stainless steel or any corrosion
resistant metal.
[0035] The substrate block 144 is a metal, preferably copper, block
having an internal coolant passageway loop so as to increase the
heat transfer capacity. In an alternative embodiment, the substrate
block 144 also includes a gas manifold and internal gas passageways
from the manifold, which terminate in multiple orifices located in
the bottom of the substrate block.
[0036] The use of orifices through which gas is ejected on the
backside of the translating substrate has been found to provide a
significant convective cooling effect on the substrate, thereby
promoting the deposition of a consistent coating layer on the
substrate. Any gas at ambient temperature, for example, is useful
for this purpose.
[0037] In addition to the beneficial cooling effect, when oxygen is
utilized as the cooling gas significant additional beneficial
results in producing a better textures coating may be obtained. In
a series of experiments the effect of oxygen introduced through the
substrate block orifices was compared to oxygen introduced into the
deposition chamber at other locations. The results demonstrate
[FIG. 4] that oxygen introduced into the chamber through the
cooling block directly onto the backside of the substrate produces
a superior coating.
[0038] Further experiments demonstrated that the beneficial effect
is responsive to changes in the oxygen flow rate and that the most
dramatic effect occurs at about 1 sccm.
[0039] It is possible that a higher oxygen partial pressure could
be achieved by flowing an increased amount of oxygen in the chamber
background. However, that would necessitate increased pumping
capacity in order to maintain the same total pressure. Also, where
a substrate cooling block of a design similar to that described is
used, some other gas will have to be used for convective cooling,
further adding load to the vacuum pumps.
[0040] Thus, there are two benefits obtained by having the oxygen
injected into the deposition chamber through orifices in the
cooling block: improved texture and better cooling of the
substrate.
[0041] It is well known that the substrate tape has to be held flat
in the deposition zone. The ion arrival angle has to be maintained
close to 55 degrees to the substrate normal in order to achieve
good texture. Inclination in the tape is not desired since it
affects the ion arrival angle.
[0042] It is easy to maintain a stationary substrate flat against a
cooling block. However, where the substrate is a moving substrate,
it is difficult to maintain good contact on a flat block. It has
now been determined that a substrate cooling block with a gentle
negative curvature provides increased stability of angle and
contact with the moving tape.
[0043] It has been determined that the benefits of curvature of the
substrate cooling block must be held within a specific range of
values to obtain the benefits of increased stability of angle and
contact while at the same time minimally affecting the ion arrival
angle the at the edges of the substrate block. The specified
benefits are obtained when the radius of curvature is in the range
of about 2 m to 25 m, preferably from about 3 m to about 15 m and
most preferably from about 5 m to about 10 m
[0044] The substrate block 144 incorporates all necessary mounting
holes and coolant connectors. In addition, the substrate block 144
includes a shutter (not shown) that can be opened or closed to
expose the deposition zone to the chamber environment. The
substrate block 144 is positioned within the IBAD chamber 110 so
that a deposition zone for the tape 160 is created at the surface
of the substrate block 144.
[0045] FIG. 3 is a cross-sectional view of the substrate block 144.
This view shows the substrate block 144, through which is disposed
a gas inlet 324 (fed by the gas inlet from the tank farm) that
branches into multiple rows of multiple gas holes 316, each of
which are approximately 0.025 to 0.4 mm, preferably about 0.05 to
about 0.25 inches and most preferably is in the range of from about
0.075 to about 0.175 inches in diameter, and terminates in one of a
plurality of nozzles 340 disposed through a bottom edge 338 of the
substrate block 144. The substrate block 144 is further shown to
include a manifold header 328. The manifold header 328 is a
metallic, preferably copper, block; a cavity machined in the
manifold header 328 covers all the gas holes 316. Each gas hole 316
is drilled completely through the substrate block. The remained of
the substrate block may be a unitary structure or it may be built
of layers. A liquid coolant channel 320 is machined through the
solid substrate block.
[0046] As shown in FIG. 1B, faraday cup 146 is a device capable of
collecting and detecting ions. It includes a coaxial cable bent at
to an angle of 55 degrees, an ion collector plate and a metallic
shield/collector. The faraday cup is an element of the sensor
system 122.
[0047] The film thickness sensor 148 is a quartz crystal with which
the film deposition thickness can be monitored through the decrease
in the resonant frequency as the film accumulates on the crystal
surface. One example of a film thickness gauge is produced by
Inoficon, Inc. [Two Technology Place, East Syracuse, N.Y. 13057].
The film thickness sensor 148 is an element of the sensor system
122.
[0048] The temperature unit 152 is a temperature-monitoring element
included in the sensor system 122. The temperature unit 152 may
include a variety of temperature measuring devices such as
thermocouples and/or an optical pyrometer.
[0049] The MS spool 154 is a spool on which a metal substrate, or
the tape 160, is wound. The diameter and width may vary with the
dimensions of the desired product. The MS spool 154 may be
constructed from a variety of materials capable of withstanding
vacuum chamber conditions. The MS spool 154 is an element of the
reel system 120.
[0050] The collector spool 156 is a spool, similar to the MS spool
154, on which the protective tape 164 is wound. The collector spool
156 may be constructed from a variety of materials capable of
withstanding IBAD vacuum chamber conditions. The collector spool
156 is an element of the reel system 120.
[0051] The protective tape 158 and the protective tape 164 are
polymeric tapes having protective properties such as scratch
resistant surfaces. The dimensions of the protective tape 158 and
the protective tape 164 correspond to the tape 160, as described
below. The protective tape 158 and the protective tape 164 are
elements included in the reel system 120.
[0052] The tape 160 is a metal tape formed from a variety of metals
capable of withstanding temperatures up to 900 C, such as stainless
steel or a nickel alloy such as Inconel. The dimensions of the tape
160 may vary to meet the desired finished product and system
limitations. For example, the tape 160 may have a thickness of 25
microns, a width of 1 cm and a length of 100 meters.
[0053] The IBAD-buffered spool 162 is constructed from similar
material and dimensions to the MS spool 154. The IBAD-buffered
spool 162 is the spool on which the tape 160 is wound and is an
element of the reel system 120.
[0054] The applicator spool 166 is of similar material and
dimensions to the collector spool 156 and is the spool on which the
protective tape 158 is collected. The applicator spool 166 is an
element of the reel system 120.
[0055] The strain gauge 168 is a device capable of measuring the
tension in a tape strung between two points. Such sensors are
commercially available from a variety of vendors. The strain gauge
168 is an element of the sensor system 122.
[0056] The detector 170 is a device that uses x-ray diffraction
capable of monitoring the texture of a HTS substrate and is an
element of the sensor system 122.
[0057] The valve 172 is a commercially available valve capable of
controlling the exit flow of a vacuum chamber. One example of such
a valve is a throttle valve produced by MeiVac, Inc. [6292-A San
Ignacio Ave., San Jose, Calif. 95119].
[0058] The evaporation source 174 is a commercially available
deposition source materials such as Yttria-Stabilized Zirconium
(YSZ) or Magnesium Oxide (MgO) for exposure to electron
bombardment. The evaporation source 174 is a consumable.
[0059] The IBAD chamber 110 exists within the IBAD system 100. The
pressure gauge 150 is functionally integrated into the IBAD chamber
110, such that a seal is maintained between the pressure gauge 150
and the IBAD chamber 110. The tank farm 126 is functionally and
independently connected to the valves 134, 136 and 138. The valves
134, 136 and 138 are in turn functionally connected to the pipes
128, 130 and 132 respectively, which in turn pass into the IBAD
chamber 110. Consequently, three separate, sealed gas flow lines
are formed between the tank farm 126 and the IBAD chamber 110 by
the valve 134 and the pipe 128, the valve 136 and the pipe 130, and
the valve 138 and the pipe 132.
[0060] The support 142 is fixedly attached to the IBAD chamber 110
and to the substrate block 144. The coolant line 140 travels from a
coolant source (not shown) into the IBAD chamber 110, through the
support 142 where it functionally connects to the substrate block
144 such that a sealed connection is formed between the coolant
line 140 and the substrate block 144. The Faraday cup 146 is
mechanically fastened to a surface of the substrate block 144, as
described in further detail in FIG. 1C. Similarly, the film
thickness sensor 148 is fixedly attached to a surface of the
substrate block 144, as described in further detail in FIG. 1C. The
temperature unit 152 is fixedly attached to a surface of the
substrate block 144.
[0061] The MS spool 154 and the collector spool 156 exist inside
the IBAD chamber 110 as further described in FIG. 1B. The
protective tape 158 is wound on the collector spool 156, from which
it spans to the MS spool 154. The protective tape 158 is unwound
simultaneously from the tape 160 from the MS spool 154, such that
for every unwinding of the tape 160 a layer of protective tape is
unwound on to the collector spool 156. The tape 160 spans from the
MS spool 154 to where it contacts a surface of the substrate block
144, then contacts the strain gauge 168 and continues to the
IBAD-buffered spool 162. The IBAD-buffered spool 162, as well as
the applicator spool 166, exist in the IBAD chamber 110 as
described in further detail in FIG. 1D. The tape 160 is wound
simultaneously with the protective tape 164 onto the IBAD-buffered
spool 162, such that for every winding of the tape 160 exists a
winding protective tape 164 on top of it. The protective tape 164
then spans from the applicator spool 166 to where it is wound on
the IBAD-buffered spool 162.
[0062] The detector 170 is functionally integrated into the IBAD
chamber 110, such that the detector 170 exists on the vertical
level on which the substrate block 144 contacts the tape 160.
Similarly, the valve 172 is functionally integrated into the IBAD
chamber 110. The valve 172 is then functionally connected to the
vacuum pump 112. The evaporation source 174 exists in the IBAD
chamber 110 such that its top surface horizontally aligned with the
substrate 144. Similarly, the DC E-beam source 114 exists in the
IBAD chamber 110 and houses the evaporation source 174 as per the
DC E-beam source 114 manufacturer's specifications.
[0063] FIG. 1C illustrates a cross-sectional view of the IBAD
system 100 taken along line A-A of FIG. 1B, that includes the IBAD
chamber 110, the MS spool 154, the collector spool 156, a shaft
176, a shaft 178, a feed-though 180, a feed-through 182, a
motor/tach 184 and a motor/tach 186.
[0064] The shaft 176 and the shaft 178 are commercially available
drive shafts capable of supporting the loads and stresses of the MS
spool 154 and the collector spool 156 respectively. The shaft 176
and the shaft 178 are elements of the reel system 120.
[0065] The feed-through 180 and the feed-through 182 are
commercially available feed-throughs such as those produced by
Ferrofluidics [Ferrotec (USA) Corporation, 40 Simon St., Nashua,
N.H. 03060-3075], and are elements of the reel system 120.
[0066] The motor/tach 184 and the motor/tach 186 are commercially
available motor and tachometer systems capable of the translating
tape 160 at speeds between 0.1 and 50 meters/hour at an accuracy
within +/-1% of the linear speed. The motor/tach 184 and the
motor/tach 186 are elements of the reel system 120.
[0067] The IBAD chamber 110 exists within the IBAD system 100. The
MS spool 154 exists within the IBAD chamber 110. The MS spool 154
is functionally connected to the shaft 176, which passes through
the feed-through 180 while still maintaining a vacuum seal. The
shaft 176 is then functionally connected to the motor/tach 184. The
feed-through 180 is functionally integrated into the IBAD chamber
110, such that a seal is maintained between the feed-through 180
and the IBAD chamber 110. Similarly, the collector spool 156 exists
within the IBAD chamber 110. The collector spool 156 is
functionally connected to the shaft 178, which passes through the
feed-through 182 while still maintaining a vacuum seal. The shaft
178 is then functionally connected to the motor/tach 186. The
feed-through 182 is functionally integrated into the IBAD chamber
110, such that a seal is maintained between the feed-through 182
and the IBAD chamber 110.
[0068] FIG. 1D illustrates a cross-sectional view of the IBAD
system 100 taken along line B-B of FIG. 1B, that includes the IBAD
chamber 110, the substrate block 144, the Faraday cup 146, the
evaporation source 174, a wire 188, a feed-through 190, electronics
192 and the ion source 116.
[0069] The wire 188 is any commercially available, shielded wire
capable of transmitting an electrical signal. The wire 188 may
include a high-temperature resistant sheath such as Teflon.
[0070] The feed-through 190 is a commercially available
feed-through that is capable of allowing a signal wire to pass
through while still maintaining a vacuum seal.
[0071] The electronics 192 is a system of electronics that detects
an ion charge and generates a corresponding electric signal.
[0072] The IBAD chamber 110 exists within the IBAD system 100. The
substrate block 144 exists within the IBAD chamber 110. The film
thickness sensor 148 is fixedly attached to a surface of the
substrate block 144, such that the film thickness sensor 148 is not
in a direct line of site of the ion source 116. Similarly, the
Faraday cup 146 is fixedly attached to a surface of the substrate
block 144 such that the Faraday cup 146 is aligned with the
direction of propagation of ions from the RF ion source 116. The
Faraday cup 146 is electrically coupled to the wire 188, which in
turn pass through the feed-through 190 and is electrically coupled
to the electronics 192. The feed-through 190 is functionally
integrated into the IBAD chamber 110, such that a seal is
maintained between the feed-through 190 and the IBAD chamber 110.
The electronics 192 exist outside of the IBAD chamber 110.
[0073] The evaporation source 174 exists in IBAD chamber such that
its top surface is horizontally aligned with the substrate block
144. The ion source 116 exists within the IBAD chamber 110 such
that the ion source 116 is aligned with the substrate block 144 to
at an angle of 55 degrees from the tape normal.
[0074] FIG. 1E illustrates a cross-sectional view of the IBAD
system 100 taken along line C-C of FIG. 1B, that includes the IBAD
chamber 110, the IBAD-buffered spool 162, the applicator spool 166,
a shaft 194, a shaft 195, a feed-through 196, a feed-through 197, a
motor/tach 198 and a motor/tach 199.
[0075] The shaft 194 and the shaft 195 are commercially available
drive shafts capable of supporting the loads and stresses of the
IBAD-buffered spool 162 and the applicator spool 166
respectively.
[0076] The feed-through 196 and the feed-through 197 are
commercially available feed-throughs such as those produced by
Ferrofluidics.
[0077] The motor/tach 198 and the motor/tach 199 are commercially
available motor and tachometer systems capable of translating the
tape 160 at speeds between 0.1 and 50 meters/hour at an accuracy
within +/-1% of the linear speed.
[0078] The IBAD chamber 110 exists within the IBAD system 100. The
IBAD-buffered spool 162 exists within the IBAD chamber 110. The
IBAD-buffered spool 162 is functionally connected to the shaft 194,
which passes through the feed-through 196 while still maintaining a
vacuum seal. The shaft 194 is then functionally connected to the
motor/tach 198. Similarly, the applicator spool 166 exists within
the IBAD chamber 110. The applicator spool 166 is functionally
connected to the shaft 195, which passes through the feed-through
197 while still maintaining a vacuum seal. The shaft 195 is then
functionally connected to the motor/tach 199.
[0079] In operation, with regard to the IBAD system 100 as
described in FIG. 1A, FIG. 1B, FIG. 1C, FIG. 1D and FIG. 1E, the
sensor system 122 continuously monitors conditions and system
parameters within the IBAD system 100. The sensor system 122
transmits the observed data as electric signals to the controller
118. The controller 118 then processes the electric signals
received from the sensor system 122 using a set algorithm or
program embedded in the controller's 118 memory to optimize the
IBAD system 100 performance. The controller 118 then sends a
separate and appropriate electric signal to the vacuum pump 112,
the DC E-beam source 114, the ion source 116, the reel system 120,
the sensor system 122 and the gas supply 124, thereby controlling
the devices' performance appropriately.
[0080] The controller 118 commands the tank farm 126 to supply
gases through the pipe 128, the pipe 130, and the pipe 132 to the
IBAD chamber 110 or to the surface of the translating tape through
orifices in substrate block 144. The controller 118 regulates and
monitors gas flow through the pipe 128, the pipe 130, and the pipe
132 with the valve/flowmeter 134, the valve/flowmeter 136 and the
valve/flowmeter 138, respectively. The coolant line 140 completes a
supply and return coolant loop in which a coolant flows through the
substrate block 144 in order to increase the heat transfer
properties of the substrate block 144. Upon command from the
controller 118, the sensor system 122 monitors the resonant
frequency of the crystal in the film thickness sensor 148, and
calculates the thickness of deposited film based on calibration
measurements. Similarly, upon command from the controller 118, the
temperature unit 152 monitors the temperature at the substrate
block 144.
[0081] The Faraday cup 146 detects ions released from the ion
source 116 at the substrate block 144, and forms an electric
current in proportion to the amount of ions impinging upon the
Faraday cup 146. This electric signal is transmitted via the wire
188, through the feed-through 190 to the electronics 192. The
electronics 192 convert the electric current to a signal
proportional to the amplitude of the electric current sensed by the
Faraday cup 146 and transmit a new electric signal to the
controller 118, as described in FIG. 1A. The film thickness sensor
148 detects the deposition rate at substrate block 144 and sends an
electric signal to the controller 118 as described in FIG. 1A.
Similarly, the detector 170 monitors the texture of the tape 160
and sends an electric signal to the controller 118 as described in
FIG. 1A. From this, the controller 118 adjusts the power level of
the DC E-beam source 114 and the ion source 116 to optimize
deposition.
[0082] The motor/tach 184 rotates the shaft 176 that passes through
the feed-through 180 and in turn rotates the MS spool 154.
Similarly, the motor/tach 186 rotates the shaft 178 that passes
through the feed-through 182 and in turn rotates the collector
spool 156. The motor/tach 186 and the collector spool 156 rotate in
such a manner that as the protective tape 158 unwinds from the MS
spool 154, the protective tape 158 simultaneously winds onto the
collector spool 156 at an equal rate. The controller 118 controls
and monitors the motor/tach 184 and the motor/tach 186 as described
in FIG. 1A.
[0083] The tape 160 then contacts the substrate block 144, at which
point the tape 160 is bombarded by ions emitted from the ion source
116 as well exposed to vapor emitted from the evaporation source
174. The evaporation source 174 emits a vapor upon bombardment by
electrons from the DC E-beam source 114. The tape 160 then contacts
the strain gauge 168. The strain gauge 168 detects a force, which
the tape 160 applies against it. The strain gauge 168 forms an
electric signal proportional to the amplitude of the strain induced
in it by the reel, and transmits this electric signal to the
controller 118 as described in FIG. 1A.
[0084] The motor/tach 198 rotates the shaft 194 that passes through
the feed-through 196 and in turn rotates the IBAD-buffered spool
162. Similarly, the motor/tach 199 rotates the shaft 195 that
passes through the feed-through 197 and in turn rotates the
applicator spool 166. The motor/tach 198 and the applicator spool
166 rotate in such a manner that as the protective tape 164 unwinds
from the applicator spool 166, the protective tape 164
simultaneously winds onto the IBAD-buffered spool 162 at an equal
rate. Similarly, the tape 160 winds onto the IBAD-buffered spool
162, such that for every wind of the tape 160 on the IBAD-buffered
spool 162 exists a wind of the protective tape 164 on wound on top
of it. The controller 118 controls and monitors the motor/tach 198
and the motor/tach 199 as described in FIG. 1A.
[0085] Upon command from the controller 118, the pressure gauge 150
monitors the pressure inside the IBAD chamber 110. The controller
118 then sends a control signal to the vacuum pump 112 and the
valve 172 to increase or decrease the exhaust flow accordingly to
maintain a desired chamber pressure.
[0086] FIG. 2 illustrates a method of use 200 of the IBAD system
100, in accordance with the invention, including the following
steps:
[0087] Step 210: Loading Spool
[0088] In this step, the MS spool 154, on which the protective tape
158 and the tape 160 are wound, is loaded into the IBAD chamber
110. The tape 160 is then fed from the MS spool 154 to the
IBAD-buffered spool 162.
[0089] Step 212: Loading Target
[0090] In this step, a material that is to be evaporated, such as
YSZ or MgO, is loaded into the E-beam evaporator 174.
[0091] Step 214: Calibration Monitors
[0092] In this step, the sensor system 122 such as the Faraday cup
146, the pressure gauge 150, and the temperature unit 152 are
calibrated.
[0093] Step 216: Pumping Down System
[0094] In this step, the controller 118 sends a command to the
vacuum pump 112, in collaboration with the valve 172 and the
pressure gauge 150 to pump down the IBAD chamber 110 to a pressure
not greater than 10.sup.-5, preferably 10.sup.-7 Torr.
[0095] Step 218: Injecting Oxygen
[0096] In this step, upon command from the controller 118 oxygen is
injected into the IBAD chamber 110 from the gas supply 124 via a
pipe such as the pipe 128.
[0097] Step 220: Starting Ion Beam
[0098] In this step, the controller 118 commands the ion source 116
to turn on to a pre-determined power level and trajectory.
[0099] Step 222: Soaking Target
[0100] In this step, the DC E-beam source 114 bombards the target
material contained within the evaporation source 174 with electrons
for a given period of time. A typical period would be about one
hour.
[0101] Step 224: Processing
[0102] A shutter (not shown) that covers a portion of the tape 160,
which exists at the substrate block 144. A process is then
initiated in which the tape 160 is fed through a deposition zone
where the evaporation source 174 and the ion source 116 deposit a
thin-film onto the tape 160 as per a pre-determined recipe that is
stored in the memory of the controller 118.
[0103] Step 226: Process Completed
[0104] In this step, the controller 118, or a user, monitors and
analyzes system the sensor system 118 and detects if the process is
complete or not. If the process is completed, then proceed to the
step 240. If the process is not completed, then return to the step
224.
[0105] Step 228: Ending Process
[0106] In this step, the controller 118 closes a shutter (not
shown) and shuts down the IBAD system 100 including all control and
feedback peripherals.
Example 1
[0107] Example 1 demonstrates the effect of oxygen injected into
the deposition chamber at different locations.
Yttria-stabilized-zirconia (YSZ) was deposited by an ion beam
assisted deposition process on 18 cm long polished inconel-625
substrates in a stationary mode.
[0108] Two experiments were conducted. In the first experiment, 20
sccm of oxygen was injected into the deposition chamber adjacent to
the wall of the deposition chamber and away from the substrate. In
the second experiment, 20 sccm of oxygen was injected into the
deposition chamber through the orifices in the substrate cooling
block. In this case, the oxygen was injected behind the back
surface of the substrate as it was held in tension against the
substrate block. All other deposition conditions were about the
same in both experiments.
[0109] FIG. 4 shows the in-plane texture of yttria-stabilized
zirconia deposited under the 2 conditions.
[0110] As FIG. 4 demonstrates, the in-plane texture of the YSZ film
deposited with the oxygen injected through the cooling block was
less than that of the film deposited with the oxygen flowing the
chamber background.
[0111] The average texture value of the YSZ film deposited with the
oxygen flow through the cooling block was approximately 20% less
[about 3 degrees] than that of the film deposited with the oxygen
injected into the chamber background. Also, the uniformity of the
texture of the YSZ film deposited with the oxygen flow through the
cooling block was better, over the 18 cm tape length.
[0112] Uniform texture is important because the texture of a buffer
film deposited on a moving tape has been found to be determined not
by the average texture value of buffer film deposited on a
stationary tape but rather, by the highest texture value. As such,
one could expect that the texture of a YSZ film deposited with the
oxygen flowing through the cooling block, in a moving mode, would
be approximately, 15-16 degrees, which is the highest texture value
measured in the film deposited in a stationary mode as shown in
FIG. 4.
[0113] On the same reasoning, it was expected that the texture of a
YSZ film deposited with the oxygen flowing in the background, in a
moving mode, would be approximately, 21-22 degrees, which is the
highest texture value measured in the film deposited in a
stationary mode as shown in FIG. 1.
[0114] In such a case, the difference in the texture of a buffer
film deposited in a moving mode with the oxygen flowing through the
block would be about 40% [6 degrees] lower than the texture of a
buffer film deposited in a moving mode with the oxygen injected
into the chamber background.
[0115] Low in-plane texture values in buffer films are important
since they greatly affect the critical current density of
superconductor films that are grown epitaxially over them.
[0116] One possible explanation for the better in-plane texture
when the oxygen is injected into the chamber through the orifices
in the cooling block is the higher oxygen partially pressure in the
vicinity of the substrate. Since the substrate is held in tension
against the curved cooling block, the local pressure of the oxygen
gas as it exits the orifices is expected to be higher than the
oxygen partial pressure in the chamber background.
Example 2
[0117] Another experiment was conducted with different amounts of
oxygen injected into the chamber through the substrate block during
deposition of YSZ films on stationary substrates.
[0118] FIG. 5 shows the in-plane texture of 3 films deposited with
oxygen flows of 1, 6, and 20 sccm. The results obtained and
reported in FIG. 2 demonstrate that the in-plane texture is
unchanged from 20 to 6 sccm, but increases substantially in the
film deposited at 1 sccm. These results are considered to confirm
that the oxygen partial pressure in the vicinity of the substrate
is an important factor in producing well-textured YSZ films.
* * * * *