Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Treating process fluid by means other than agitation or...
Reexamination Certificate
2000-02-22
2002-04-16
Gorgos, Kathryn (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Treating process fluid by means other than agitation or...
C204S267000, C204S269000, C205S574000, C205S771000, C205S772000, C451S060000, C451S287000
Reexamination Certificate
active
06372111
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to chemical mechanical planarization (CMP) and electroplating of a metal film on semiconductor devices, and more particularly, to a method and apparatus for reclaiming a metal from the effluent of a CMP process and using said reclaimed metal in an electroplating process.
2. Description of Related Art
Electroplating or electrodeposition, is a well-known process used to deposit metals such as copper from a chemical solution onto an electrode called a cathode and is described in the following articles, that are hereby incorporated by reference:
1. Loweheim, F. A., ed.,
Modem Electroplating,
3
rd
edition, Electrochemical Society, 1974.
2. Paunovic, M. and Schlesinger, M.,
Fundamentals of Electrodeposition,
Electrochemical Society Series, John Wiley and Sons, 1998.
Electroplating has recently received a tremendous amount of attention as a process for depositing a metal such as copper onto the surface of a semiconductor device. Prior art
FIG. 1
is a schematic representation of the typical components of an electroplating system. In this representation, an electroplating chemical solution
205
is fed from a larger storage chamber (not shown) into an electroplating chamber
210
. The electroplating chamber
210
contains an anode
215
and a cathode
220
, both of which are immersed in the chemical solution
205
. The anode
215
and cathode
220
may be constructed of copper, platinum, carbon, steel, or other conductive materials typically used for electrodeposition. Electricity is generated from a power source
225
and is passed between the anode
215
and cathode
220
such that electrons flow from the anode
215
, through the wire
230
, to the cathode
220
. The power source
225
may be a battery, a potentiostat or other potential creating device that is well known in the industry.
As is well known in electrodeposition, this will cause a reduction reaction to occur at the cathode
220
and an oxidation reaction to occur at the anode
215
. In electroplating, the reduction reaction is a chemical reaction where a species which is on the surface of the electrode, or is dissolved in the chemical solution
205
, such as a positively charged metal ion (M
+
), gets reduced, i.e. charged by at least one electron as represented by the following reaction:
M
+
+e
−
→M
This causes the metal (M) to become “plated” onto the cathode so that a metal film is grown onto the surface of the cathode
220
. The metal may be any conductive material such as copper, tungsten, aluminum, iron, nickel, titanium, tantalum, palladium, iridium, platinum, silver, or metal alloys. In the semiconductor industry, a semiconductor wafer containing semiconductor devices is typically used as the cathode
220
causing a film of metal to become plated onto the semiconductor devices on the wafer.
An oxidation reaction is a chemical reaction where a species at the anode
215
gives up at least one electron. The species in an oxidation reaction might be a species in the chemical solution
205
such as negatively charged ions (An
−
) which become oxidized as represented by the following reaction:
An
−
→An+e
−
,
The species in an oxidation reaction might also be the metal material of the anode
215
. In this case, during processing the metal loses at least one electron and becomes dissolved in the chemical solution
205
as is represented by the following reaction:
M→M
+
+e
−
CMP is a well-known process used to remove and planarize materials on a semiconductor device such as copper, tungsten, aluminum, silicon, silicon dioxide, or silicon nitride. As part of the semiconductor device fabrication process, these types of materials are normally deposited on the surface of a semiconductor device by typical methods such as electroplating or chemical vapor deposition and then removed and planarized using a CMP process. Prior art
FIG. 2
is a perspective view of a CMP system used to perform a conventional CMP process with an exploded cross-sectional view
9
of a semiconductor device being planarized. In
FIG. 2
, the CMP system
5
includes a polishing pad
10
, placed on a rotating table
12
. The semiconductor wafer
14
containing the semiconductor device is held in a rotating carrier
16
, and the front surface
17
of the semiconductor device on the wafer
14
is rubbed against the polishing pad
10
to planarize the semiconductor device.
During a conventional CMP process, a chemical liquid
18
is also required and is delivered to the CMP system
5
by a first delivery device
7
. Although not shown, typically a fine particle abrasive such as alumina or silica, normally already mixed into the chemical liquid
18
and known conventionally as a slurry, is also required for the CMP process. The diameter of the abrasive particles typically ranges from ten nanometers to ten microns. The abrasive particles need not be already mixed in the chemical liquid
18
, but rather may be embedded in the polishing pad
10
. Alternatively, the abrasive particles may also be separately delivered to the CMP system
5
by a second delivery device (not shown) and mixed with the chemical liquid
18
on the polishing pad
10
. In operation, the chemical liquid
18
and/or slurry is used to continuously wet the polishing pad
10
while the pad
10
is mechanically rubbed against the front surface
17
of the semiconductor device enabling removal and planarization of the deposited material on the wafer
14
.
Recently, CMP and electroplating have received a tremendous and growing amount of investigation and engineering as enabling technologies for manufacturing high-speed semiconductor devices. This is because high-conductivity copper is now being used as the interconnect material (replacing aluminum) to connect multiple semiconductor devices on a semiconductor device. Electroplating has been used to deposit copper on semiconductor wafers. With the use of copper, more and more layers are formed on a single semiconductor device and in a more compact area. With the additional layers, the CMP and the electroplating processes are both used more frequently since each such layer requires metal deposition and planarization prior to adding subsequent layers. Thus, the electroplating and CMP processes are becoming increasingly more necessary as more layers are formed and increasingly more important to the overall semiconductor manufacturing process.
Two areas of concern in both the CMP and electroplating processes are the high cost of consumables used and the environmental impact of discarding used CMP and electroplating chemical liquids. In electroplating, the high cost of consumables generally stems from items that are “consumed” during processing such as the electroplating chemical solution or the anode material that becomes dissolved during processing as described in FIG.
1
. In CMP, the high cost of consumables generally stems from items such as the chemical liquid or slurry and polishing pads of
FIG. 2
, to name a few. For example, a copper CMP process may require about 600 cubic centimeters of chemical liquid for each semiconductor wafer processed. At this rate, a semiconductor manufacturing facility that produces 5,000 completed semiconductor wafers each week, and that requires six copper CMP processes for each completed semiconductor wafer, may require about one million liters of chemical liquid each year for the copper CMP process. At current slurry costs of about $10.00 per liter, this translates to a cost of over ten million dollars annually.
As mentioned above, disposal of the used CMP chemical liquids or the CMP effluent is another concern in CMP processing. Prior art
FIG. 3
is a typical disposal system for CMP effluent in a semiconductor manufacturing facility. In Prior Art
FIG. 3
, a chemical liquid or slurry
20
contained in storage tank
25
is sent to the CMP system
30
, such as the CMP system
5
of prior art FIG.
2
. The “used” slurry or chemical liquid
Gorgos Kathryn
Leader W. T.
LandOfFree
Method and apparatus for reclaiming a metal from a CMP... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for reclaiming a metal from a CMP..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for reclaiming a metal from a CMP... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2925700