Chemistry: electrical and wave energy – Apparatus – Coating – forming or etching by sputtering
Reexamination Certificate
2001-04-23
2002-12-17
VerSteeg, Steven H. (Department: 1753)
Chemistry: electrical and wave energy
Apparatus
Coating, forming or etching by sputtering
C204S192110, C204S192120, C204S298030, C204S298040, C204S298110, C427S008000, C427S569000, C427S255500, C118S730000, C118S712000, C118S720000, C118S7230VE, C118S7230ER, C118S504000
Reexamination Certificate
active
06495010
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to thin film deposition and etching systems. In particular, the present invention relates to methods and apparatus for depositing thin films with very high uniformity. The present invention also relates to methods and apparatus for etching material at highly uniform etch rates.
BACKGROUND OF THE INVENTION
There are three common techniques used to deposit thin films onto substrates. These techniques are evaporation, ion beam deposition, and magnetron sputtering.
FIG. 1
illustrates a schematic diagram of a prior art electron beam evaporation deposition system
10
. The evaporation system
10
is enclosed in a vacuum chamber
12
. An electron gun
14
generates an electron beam
16
that is used to heat a crucible
18
containing the deposition material to a temperature that causes the deposition material to evaporate. The electron beam is deflected with a magnet
20
that causes the electron beam to strike the desired location in the crucible
18
. Typical evaporation systems have multiple crucibles.
Some Evaporation systems include multiple sources and multiple electron guns that produce deposition material from two or more sources and deposit the deposition material simultaneously onto a substrate. Alternatively, a thermal heating element (not shown) is used to heat the crucible
18
. A substrate support
22
that typically supports multiple substrates
23
is positioned in the path of the evaporated material. In some known evaporation systems, the substrate support
22
is rotated with a motor
24
in order to increase the uniformity of the deposited thin film.
FIG. 2
illustrates a schematic diagram of a prior art ion beam sputter deposition system
50
. The ion beam sputter deposition system
50
is enclosed in a vacuum chamber
52
. An ion source
54
generates an ion beam
56
that is directed to one or more targets
58
. The ion beam
56
strikes the target
58
and sputters neutral atoms from the target
58
with a stutter flux
60
. A substrate support
62
that typically supports multiple substrates
64
is positioned in the path of the sputter flux
60
. The sputter flux
60
bombards the substrates, thereby depositing a sputtered thin film. In order to increase the uniformity of the sputtered thin film, the substrate support
62
may be rotated with a motor
66
. Ion beam sputtering is advantageous because it permits independent control over the energy and current density of the bombarding ions.
FIG. 3
illustrates a schematic diagram of a prior art magnetron sputter deposition system
80
. The magnetron sputter deposition system
80
is enclosed in a vacuum chamber
82
. The magnetron sputter deposition system
80
includes a diode device having an anode
84
and a cathode
86
. A magnet
88
is positioned behind the cathode
86
. Two ring-shaped cathodes and a disk-shaped anode are shown, but there are several other known configurations.
The cathode
86
is biased to a negative potential that is high enough to induce a breakdown in the surrounding gas and to sustain a plasma
90
. The magnet
88
generates a magnetic field
92
behind the cathode
86
that traps electrons generated by the cathode
86
. The electrons lose energy in spiral paths in the plasma
90
and are collected by the anode
84
. The electrons enhance the bombarding efficiency of ions
94
in the plasma
90
. Neutral atoms
96
are sputtered fit the cathode
86
with a sputter flux
98
. The sputter flux
98
bombards the substrates
64
, thereby depositing a sputtered thin film onto the substrate
64
.
The substrates
64
in known systems are typically placed at a distance from the cathode
86
ranging between two and ten inches. In order to increase the uniformity of the sputtered film, the substrate support
62
may be rotated with a motor
66
. Magnetron sputtering is advantageous because it has relatively high deposition rates, large deposition areas, and low substrate heating.
The deposition thickness uniformity achieved with these known techniques is limited by the flux uniformity achieved at the substrate plane and the type of substrate rotation. The flux uniformity can be adversely affected by target or deposition material imperfections that cause hot and cold spots, which affect the deposition rate. Typically, the flux uniformity changes with time. The flux uniformity can be improved somewhat by using a large target and/or by using a long distance from the target to the substrate. However, there are practical limits to the size of the target and the distance from the target to the substrate. Some applications, such as optical filters for high-speed optical communication systems, require thin film uniformities that cannot be achieved with these prior art techniques.
SUMMARY OF THE INVENTION
The present invention relates to methods and apparatus for depositing thin films using a differentially-pumped deposition source and deposition chamber, where the pressure in the deposition source is substantially higher than the pressure in the deposition chamber. The present invention also relates to methods and apparatus for using an ion source that generates an ion beam for ion beam assisted processing of the deposited thin films. In one embodiment, the ion beam and the deposition flux do not overlap and the ion beam is used for out-of-phase ion-beam-assisted processing. Both the deposition source and the ion beam source can be positioned a relatively short distance from the substrate, thereby exposing the substrate to a relatively high density of sputter flux and ion beam flux.
One embodiment of the deposition system of the present invention is a differentially-pumped magnetron sputtering system. The magnetron sputtering system has numerous advantages over known deposition systems. For example, the magnetron sputtering system deposits high purity, high-density films at high deposition rates with a high degree of uniformity and run-to-run consistency. In addition, the magnetron sputtering system has a long target lifetime and is relatively easy to maintain. Thin film uniformity can be improved by aperturing sputter flux from the sputter deposition source and then moving the substrates relative to the sputter flux with a dual-scan motion, such as a two dimensional motion. Thin film uniformity can also be improved by scanning one motion much faster than the other motion. Also, thin film uniformity can be improved by over-scanning.
Accordingly, the present invention features a differentially pumped deposition system that includes a deposition source that is positioned in a first chamber. In one embodiment, the deposition source is a magnetron sputter source. In another embodiment, the deposition source is an evaporation source. The deposition source generates deposition flux comprising neutral atoms and molecules.
A shield defines an aperture that is positioned in a path of the deposition flux. The shield passes the deposition flux through the aperture and substantially blocks the deposition flux from propagating past the shield everywhere else. The aperture may be shaped to increase the transmitted deposition flux. The aperture may also be shaped to reduce the over-scan area. A substrate support is positioned in a second chamber adjacent to the shield. The pressure in the second chamber is lower than the pressure in the first chamber.
The deposition system also includes a dual-scanning system that scans the substrate support relative to the aperture with a first and a second motion. The dual-scanning system may be a mechanical scanning system. The scan rate of the first motion. maybe substantially greater than the scan rate of the second motion The scan rate of at least one of the first motion and the second motion may also vary with time during deposition. In one embodiment the dual-scanning system comprises a rotational scanning system and a translational scanning system, wherein the first motion comprises a rotational motion having a rotation rate and the second motion comprises a translational motion having a translation rate. Th
Rauschenbach Kurt
Rauschenbach Patent Law Group
Unaxis USA Inc.
VerSteeg Steven H.
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