Chemistry: electrical and wave energy – Apparatus – Coating – forming or etching by sputtering
Reexamination Certificate
1997-06-25
2004-05-11
McDonald, Rodney G. (Department: 1753)
Chemistry: electrical and wave energy
Apparatus
Coating, forming or etching by sputtering
C204S298130
Reexamination Certificate
active
06733641
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is related to previously filed, currently pending U.S. applications Ser. No. 08/390,662, filed Feb. 17, 1995 and a divisional thereof filed Apr. 23, 1996, both having the same title as this application and naming the same inventors, and incorporated herein by reference in their entirety.
FIELD OF THE INVENTION
This invention relates to targets for plasma sputtering apparatus.
BACKGROUND OF THE INVENTION
Sputtering processes are typically performed in a vacuum chamber. The chamber includes a target comprised of material, such as Aluminum, to be sputtered. A substrate, such as a semiconductor wafer bearing integrated circuits, is placed in the chamber and the chamber is evacuated. Once the chamber is evacuated, a process gas is introduced into the chamber at a low pressure, and a voltage is applied to the target. Ionized gas in the chamber is accelerated by the electric fields of the target. When the ions impinge upon the target, atoms of sputtering material are dislodged (“sputtered”) from the target. The dislodged atoms deposit on the substrate, forming, over time, a thin film of target material on the substrate.
The sputtering process described above slowly wears material from the target until, ultimately, the target must be renewed. Typically, this is done by removing the target from the chamber and inserting a new target into the chamber.
FIG. 1
is a cross-sectional view of a typical vacuum chamber
10
for performing a sputtering process, and a target
12
mounted in this chamber. Chamber
10
is generally cylindrical or rectangular in shape, and target
12
is generally disk-shaped and mounts into a circular opening
13
in chamber
10
. Wafer
14
, which is disk-shaped, is supported inside of chamber
10
by a generally disk-shaped anode
16
. Electrical power is applied to the anode
16
with respect to the remainder of the chamber
10
.
As shown in
FIG. 1
, a typical target is manufactured of a backing plate
20
of a metal such as Copper, metallurgically bonded (e.g., soldered) to a target plate having a front face
22
of sputtering material. Backing plate
20
is affixed to a chamber cover
23
by mounting screws
24
. Cover
23
is clamped to chamber
10
by means not shown, and supports the front face
22
in a position generally opposite wafer
14
. An O-ring inserted into groove
26
prevents leakage into the chamber
10
through the target-chamber interface. During the sputtering process, material from front face
22
is removed and deposited on the wafer
14
, while backing plate
20
remains in place.
Over time, a typical target such as that shown in
FIG. 1
wears to the extent that the sputtering material on the front face
22
must be renewed. When this occurs, cover
23
is lifted from chamber
10
, and target
12
is detached from cover
23
and removed. A new target
12
is then assembled to cover
23
, and cover
23
is clamped onto chamber
10
, and processing continues.
Backing plates are typically manufactured of expensive metals, and for this reason are typically recycled after use. Once a worn target has been removed from the cover
23
, the backing plate and the remaining sputtering material soldered thereto, are returned to the manufacturer. The manufacturer removes the remaining sputtering material from the backing plate, and solders a new target plate having a front face
22
of sputtering material to the backing plate. The target
12
, consisting of the recycled backing plate and new front face of sputtering material, is then ready for resale. To ensure that processing facilities promptly return used targets to the manufacturer, manufacturers typically include a core charge in the price of each target sold; this charge is refunded upon return of the used target to the manufacturer.
This process for recycling used targets is inconvenient in that it requires regular shipment of bulky and heavy targets back to the manufacturer. Furthermore, to ensure a sufficient stockpile of targets to avoid downtime, semiconductor fabrication facilities must retain in inventory a number of new targets
12
, which involves essentially permanent payment of the core charges associated with the targets held in inventory.
SUMMARY OF THE INVENTION
In accordance with the invention, the above disadvantages are overcome by providing a target in which the sputtering material is not soldered or otherwise metallurgically bonded to a backing plate. Rather, the target is mechanically coupled (e.g., with bolts) to the chamber. As a result, the sputtering material can be easily uncoupled from the chamber and replaced, without also requiring removal and replacement of a backing plate.
Specifically, in one aspect the invention features an adapter sized for permanent mounting to the chamber at the same attachment points as the target shown in FIG.
1
. The adapter has a central aperture in which the adapter supports a target. Mechanical couplers inserted through the adapter and the target mechanically join the target to the adapter. The target is manufactured homogeneously of sputtering material, and can be separately installed into and removed from the chamber without removing the adapter. As a result, when the target is worn, the target can be replaced without requiring refurbishing of the adapter.
In specific embodiments, the adapter, which may be of Copper, has a generally cylindrical shape, with generally cylindrical supporting walls, a generally radial outer flange sized for mounting to the chamber in place of the prior art target, and a generally radial inner flange for supporting the target. Apertures through the inner flange of the adapter receive the mechanical couplers, which may be bolts. The target, which is a single piece of machined material such as Aluminum or Aluminum Oxide, Titanium, Gold, refractory metals, or other self-supporting materials, has a disk shape, and has threaded apertures in one of its disk shaped surfaces, arranged in mating relation to the apertures in the inner flange of the adapter. Bolts inserted through the apertures in the adapter are threaded into the apertures on the target and thus couple the target to the adapter.
In further aspects the invention features a target having features described above, and a modified chamber integrally incorporating the adapter therein, thus avoiding the need for a separate adapter.
The above and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof.
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patent: 4855033 (1989-08-01), Hurwitt
patent: 5009765 (1991-04-01), Qamar et al.
patent: 5066381 (1991-11-01), Ohta et al.
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patent: 5147521 (1992-09-01), Belli et al.
patent: 5244556 (1993-09-01), Inoue
patent: 5259941 (1993-11-01), Münz
patent: 5269403 (1993-12-01), Pouliquen et al.
patent: 5529673 (1996-06-01), Strauss et al.
patent: 5641389 (1997-06-01), Strauss et al.
patent: 5738770 (1998-04-01), Strauss et al.
patent: 59-170269 (1984-09-01), None
patent: 59-179784 (1984-10-01), None
patent: 2-285069 (1990-11-01), None
patent: 92-20831 (1992-11-01), None
Tokyo Electron KK,Sputtering Device Has Readily Replaceable Target, English Abstract, Japanese Document 2-285069.
Murata Seisakusho KK,Target For Sputtering, English Abstract, Japanese Document 55-89471.
Gilman Paul S.
Hunt Thomas J.
Strauss David P.
McDonald Rodney G.
Praxair S. T. Technology, Inc.
Schwartz Iurie
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