Removing metal ions from wastewater

A novel process and apparatus are disclosed for cleaning wastewater containing metal ions in solution, hydrogen peroxide, and high solids, e.g., greater than about 50 mg/l particulate solids. A carbon adsorption column removes hydrogen peroxide in the wastewater feed containing high solids. A chemical precipitation unit removes the metal ions from solution. The process and apparatus remove metal ions such as copper from a high solids byproduct polishing slurry from the chemical mechanical polishing (CMP) of integrated circuit microchips to form an environmentally clean wastewater discharge.

BACKGROUND OF THE INVENTION
 1. Technical Field
 This invention relates to a process and apparatus for removing metal ions
 from wastewater. In one aspect, this invention relates to a process and
 apparatus for removing copper ions from wastewater from a chemical
 mechanical polishing (CMP) of integrated circuit microchips.
 2. Background
 Semiconductor microelectronic chip (microchip) manufacturing companies have
 developed advanced manufacturing processes to shrink electronic circuitry
 on a microchip to smaller dimensions. The smaller circuitry dimensions
 involve smaller individual minimum feature sizes or minimum line widths on
 a single microchip. The smaller minimum feature sizes or minimum line
 widths, typically at microscopic dimensions of about 0.2-0.5 micron,
 provide for the fitting of more computer logic onto the microchip.
 An advanced new semiconductor manufacturing technology involves the use of
 copper in place of aluminum and tungsten to create a copper microchip
 circuitry on a silicon wafer. The copper has an electrical resistance
 lower than aluminum, thereby providing a microchip which can operate at
 much faster speeds. The copper is introduced to ULSI and CMOS silicon
 structures and is utilized as interconnect material for vias and trenches
 on these silicon structures.
 ULSI silicon structures are Ultra Large Scale Integration integrated
 circuits containing more than 50,000 gates and more than 256K memory bits.
 CMOS silicon structures are Complimentary Metal Oxide Semiconductor
 integrated circuits containing N-MOS and P-MOS transistors on the same
 substrate.
 For fully integrated multi-level integrated circuit microchips, up to 6
 levels, copper now is the preferred interconnect material.
 A chemical mechanical polishing (CMP) planarization of copper metal layers
 is used as a part of the advanced new semiconductor manufacturing
 technology. The chemical mechanical polishing (CMP) planarization produces
 a substrate working surface for the microchip. Current technology does not
 etch copper effectively, so the semiconductor fabrication facility tool
 employs a polishing step to prepare the silicon wafer surface.
 Chemical mechanical polishing (CMP) of integrated circuits today involves a
 planarization of semiconductor microelectronic wafers. A local
 planarization of the microchip operates chemically and mechanically to
 smooth surfaces at a microscopic level up to about 10 microns (.mu.m). A
 global planarization of the microchip extends above about 10 microns
 (.mu.m) and higher. The chemical mechanical polishing planarization
 equipment is used to remove materials prior to a subsequent precision
 integrated circuit manufacturing step.
 The chemical mechanical polishing (CMP) planarization process involves a
 polishing slurry composed of an oxidant, an abrasive, complexing agents,
 and other additives. The polishing slurry is used with a polishing pad to
 remove excess copper from the wafer. Silicon, copper, and various trace
 metals are removed from the silicon structure via a chemical/mechanical
 slurry. The chemical/mechanical slurry is introduced to the silicon wafer
 on a planarization table in conjunction with polishing pads. Oxidizing
 agents and etching solutions are introduced to control the removal of
 material. Deionized water rinses often are employed to remove debris from
 the wafer. Ultrapure water (UPW) from reverse osmosis (RO) and
 demineralized water also can be used in the semiconductor fabrication
 facility tool to rinse the silicon wafer.
 INTRODUCTION TO THE INVENTION
 The chemical mechanical polishing (CMP) planarization process introduces
 copper into the process water, and governmental regulatory agencies are
 writing regulations for the discharge of wastewater from the chemical
 mechanical polishing (CMP) planarization process as stringently as the
 wastewater from an electroplating process, even though CMP planarization
 is not an electroplating process.
 The copper ions in solution in the wastewater must be removed from the
 byproduct polishing slurry for acceptable wastewater disposal.
 The chemical mechanical polishing planarization of the microchip produces a
 byproduct "grinding" (polishing) slurry wastewater which contains copper
 ions at a level of about 1-100 mg/l. The byproduct polishing slurry
 wastewater from the planarization of the microchip also contains solids
 sized at about 0.01-1.0 .mu.m at a level of about 500-2000 mg/l (500-2000
 ppm).
 An oxidizer of hydrogen peroxide (H.sub.2 O.sub.2) typically is used to
 help dissolve the copper from the microchip. Accordingly, hydrogen
 peroxide (H.sub.2 O.sub.2) at a level of about 300 ppm and higher also can
 be present in the byproduct polishing slurry wastewater.
 A chelating agent such as citric acid or ammonia also can be present in the
 byproduct polishing slurry to facilitate keeping the copper in solution.
 A chemical/mechanical slurry wastewater will discharge from the chemical
 mechanical polishing (CMP) tool at a flow rate of approximately 10 gpm,
 including rinse streams. This chemical/mechanical slurry wastewater will
 contain dissolved copper at a concentration of about 1-100 mg/l.
 Fabrication facilities operating multiple tools will typically generate a
 sufficient quantity of copper to be an environmental concern when
 discharged to the fabrication facility's outfall. A treatment program is
 needed to control the discharge of copper present in the copper CMP
 wastewater prior to introduction to the fabrication facility's wastewater
 treatment system.
 A conventional wastewater treatment system at a semiconductor fabrication
 facility often features pH neutralization and fluoride treatment. An
 "end-of-pipe" treatment system typically does not contain equipment for
 removal of heavy metals such as copper. An apparatus and method for
 providing a point source treatment for copper removal would resolve a need
 to install a costly end-of-pipe copper treatment system.
 Considering equipment logistics as well as waste solution characteristics,
 a point source copper treatment unit is needed which is compact and which
 can satisfy the discharge requirements of a single copper CMP tool or a
 cluster of copper CMP tools.
 Iron sulfate (FeSO.sub.4) or aluminum sulfate (Al.sub.2 (SO.sub.4).sub.3)
 can be used to co-precipitate copper ions and produce a sludge. This
 precipitation process raises the pH to precipitate iron hydroxide and
 copper hydroxide with a remainder of a silica, alumina wastewater slurry.
 The byproduct polishing slurry wastewater containing copper ions from the
 CMP of semiconductor microelectronic chips containing copper can be passed
 through a microfilter to remove solids in the form of a silica, alumina
 wastewater slurry.
 Medford et al., U.S. Pat. No. 3,301,542, disclose treating copper
 contaminated acidic etching solutions from the manufacture of printed
 circuit boards. The acidic etching solutions wastewater is neutralized
 with sodium hydroxide.
 Leach et al., U.S. Pat. No. 4,010,099, disclose extracting copper by
 contacting with an organic liquid ion exchange reagent.
 Stephens, U.S. Pat. Nos. 3,912,801, and Marquis et al, 5,348,712, disclose
 extracting metals with cyclic organic carbonates.
 Spinney, U.S. Pat. Nos. 3,440,036; Swanson, 3,428,449; and Dalton,
 4,231,888, disclose extracting copper using organic oximes as the
 extraction agent.
 The permeate from the microfilter containing permeate copper ions can be
 reacted with sodium sulfide (NaS.sub.2) or an organic precipitating
 solution of a dithiocarbamate to precipitate the copper.
 The dithiocarbamate precipitating solution is used to pull the copper ions
 away from the complexing agent.
 Siefert et al., U.S. Pat. No. 5,346,627, disclose a method for removing
 metals from a fluid stream with a water soluble ethylene dichloride
 ammonia polymer that contains dithiocarbamate salt groups to form
 complexes with the metals.
 If hydrogen peroxide (H.sub.2 O.sub.2) is present, the dithiocarbamate
 reacts with the hydrogen peroxide (H.sub.2 O.sub.2) before the
 dithiocarbamate operates to pull the copper ions from the complexing
 agent. Accordingly, hydrogen peroxide present in the precipitating step
 makes it difficult to precipitate the copper, and a large amount of the
 dithiocarbamate organic precipitating solution is required to be used.
 Misra et al., U.S. Pat. No. 5,599,515, disclose treating heavy metal
 ion-containing wastewaters generated by printed circuit board
 manufacturing (Col. 1, line 20; Col. 14, lines 40-42) and removing copper
 ions from wastewater with a dithiocarbamate to precipitate the copper in
 wastewater. Misra et al. disclose that several compounds can be used to
 form insoluble metal complexes with heavy metal ions. All exert a stronger
 attraction to the metal ion than the chelants normally occurring with the
 metals in the wastewaters. Such complexing agents include
 dithiocarbamates. These complexing agents are disclosed as quite
 expensive. (Col. 3, lines 33-48.) Ferrous sulphate is disclosed to replace
 toxic heavy metal ions that are bonded by chelating agents, but large
 amounts of ferrous ions can be required, which produces significant
 quantities of sludge. (Col. 4, lines 16-49.) The Misra et al. Example V
 discloses the influence exerted by chelating agents and ammonium ions on a
 200 mg/L copper solution. Hydrogen peroxide is added as a strong oxidizer.
 (Col. 12, lines 37-41.)
 Guess, U.S. Pat. No. 5,298,168, discloses removing copper ions using
 dithiocarbamate to precipitate the copper from wastewater that has been
 filtered through carbon. Mercury is precipitated by dithiocarbamates.
 (Col. 4, lines 30-50.) Activated carbon is disclosed. (Col. 4, lines
 58-59.) The Guess patent discloses that heavy metals present in the
 solution, such as copper, compete with mercury for the carbamate in
 forming a stable complex for precipitation. (Col. 7, lines 1-8.)
 Kennedy, Jr., U.S. Pat. No. 4,629,570, discloses cleaning wastewater
 (boiler scale) using dithiocarbamate as a copper precipitate and carbon
 filtration. In the Kennedy, Jr. U.S. Pat. No. 4,629,570, chelated copper
 is removed by dithiocarbamates added in stoichiometric amounts to the
 amount of dissolved copper. (Col. 3, lines 18-26.) Activated charcoal then
 can be used. (Col. 3, lines 27-30.)
 Asano et al., U.S. Pat. No. 3,923,741, in Example 3 pass a copper solution
 through a granular active carbon column. Flow resistance is measured and
 reported. The solution then is passed through an ion exchange resin
 column. (U.S. Pat. No. 3,923,741, Col. 6, lines 35-65.)
 Koehler et al., U.S. Pat. No. 3,914,374, disclose removing residual copper
 from acid nickel solutions by activated carbon which absorbs the copper.
 Hayden, U.S. Pat. No. 5,464,605, discloses removing peroxides from liquids
 by activated carbon.
 Conventional pretreatment practice for granular activated carbon beds
 principally requires the removal of contaminants such as excess amounts of
 suspended solids. Suspended solids, including bacteria, in amounts
 exceeding about 50 mg/l are required to be removed prior to operating the
 carbon bed.
 Wastewaters from non-copper CMP processes are generally discharged to the
 semiconductor fabrication facility end-of-pipe where the wastewater is
 neutralized prior to discharge. With the advent of copper technology,
 these slurry wastewaters will contain copper.
 Copper present in the fabrication facility outfall can pose problems. Some
 fabrication facilities must control the amount of suspended solids in the
 out fall. Accumulation in the receiving POTW's (Publicly Owned Treatment
 Works) sludges result in increased cost for municipal sludge disposal and
 environmental concerns to eliminate copper in the municipal sludge.
 Bio-toxicity problems in the municipal biological systems are caused by
 mass loading of copper.
 Environmental discharge limits for copper result in non-compliance at the
 fabrication facility.
 A process and apparatus are needed to remove the copper from the waste
 slurries near the point of generation and permit a copper-free waste to
 pass to discharge and neutralization in the conventional manor.
 A process and apparatus are needed to remove copper ions from solution for
 acceptable wastewater disposal of byproduct polishing slurries containing
 high amounts of suspended solids and to remove the copper ions from
 solution containing high amounts of suspended solids efficiently and
 economically.
 It is an object of the present invention to provide a novel process and
 apparatus for removing metal ions from solution.
 It is an object of the present invention to provide a novel process and
 apparatus for removing metal ions from solutions containing high amounts
 of suspended solids.
 It is an object of the present invention to provide a novel process and
 apparatus for removing copper ions from solution.
 It is an object of the present invention to provide a novel process and
 apparatus for removing copper ions from solutions containing high amounts
 of suspended solids.
 It is an object of the present invention to provide a novel process and
 apparatus for removing copper ions from solution from a byproduct
 polishing slurry for acceptable wastewater disposal.
 Another object of the present invention is to provide a novel process and
 apparatus for removing copper ions from solution from a byproduct
 polishing slurry from the chemical mechanical polishing (CMP) of
 integrated circuits.
 It is a further object of the present invention to provide a novel process
 and apparatus for removing copper ions from solutions containing high
 amounts of suspended solids economically and efficiently.
 These and other objects and advantages of the present invention will become
 more apparent to those skilled in the art in view of the following
 detailed description and the accompanying drawing.
 SUMMARY OF THE INVENTION
 The process and apparatus of the present invention remove metal ions from
 wastewater by providing a first step carbon adsorption bed for receiving a
 wastewater feed containing metal ions in solution, wherein the wastewater
 feed contains solids sized in the range of about 0.01-1.0 .mu.m in an
 amount higher than about 50 mg/l, in combination with providing a second
 step chemical precipitation unit operation for receiving a carbon bed
 product stream from the carbon adsorption bed and for removing the metal
 ions from solution. The process and apparatus of the present invention
 remove metal ions from wastewater containing solids in an amount higher
 than about 100 mg/l, preferably in an amount higher than about 500 mg/l,
 e.g., by way of example in an amount in the range of about 500-2000 mg/l.
 A wastewater feed containing hydrogen peroxide and metal ions in solution
 is passed to the carbon column to reduce the concentration of the hydrogen
 peroxide and form a carbon bed effluent having concentration levels of
 hydrogen peroxide less than about 1 mg/l (1 ppm). In one aspect, the metal
 ions are copper ions. In one aspect, the metal ions are copper ions at a
 concentration level in the range of about 1-100 mg/l.
 The chemical precipitation unit operation includes means for contacting
 copper ions in the carbon bed product stream metal ions with an organic
 carbamate to precipitate the copper ions. In one embodiment, the organic
 carbamate includes dithiocarbamate.
 In an alternative embodiment, the chemical precipitation unit operation
 includes means for contacting copper ions in the carbon bed product stream
 with an inorganic iron sulfate (FeSO.sub.4) or aluminum sulfate (Al.sub.2
 (SO.sub.4).sub.3) to co-precipitate the copper ions at a neutral or
 elevated pH.
 The process and apparatus of the present invention operate to remove metal
 ions from a wastewater from a byproduct polishing slurry. In one
 embodiment, the process and apparatus of the present invention operate to
 remove metal ions, e.g., such as copper metal ions, from a wastewater from
 a byproduct polishing slurry from the chemical mechanical polishing (CMP)
 of integrated circuit microchips to precipitate the metal ions and form an
 environmentally clean water discharge product.

DETAILED DESCRIPTION
 The process and apparatus of the present invention provide for a removal of
 metal ions through a combination of steps including passing a wastewater
 solution containing metal ions first through a carbon adsorption column,
 preferably without prior micro-filtration or ultra-filtration removal of
 suspended solids, to remove hydrogen peroxide (H.sub.2 O.sub.2)
 catalytically and then reacting the wastewater solution containing metal
 ions with an organic precipitating solution to remove the metal ions from
 solution.
 Solids are defined herein using Standard Methods 302 A, Preliminary
 Filtration for Metals (1985, 16.sup.th ed.).
 In an alternative embodiment, the wastewater solution containing metal ions
 passing from the carbon column can be reacted with an inorganic
 precipitating solution to remove the metal ions from solution.
 In one aspect, the process and apparatus of the present invention provide a
 novel process and apparatus for the removal of copper ions including
 passing a wastewater solution containing copper ions first through a
 carbon column, preferably without prior micro-filtration or
 ultra-filtration removal of silica, alumina slurry solids, to remove the
 hydrogen peroxide (H.sub.2 O.sub.2) catalytically and then reacting the
 wastewater solution containing copper ions with an organic dithiocarbamate
 to precipitate the copper.
 In one aspect, the process and apparatus of the present invention provide a
 novel apparatus and process for the removal of copper ions including
 passing a wastewater solution containing copper ions first through a
 carbon adsorption column, preferably without prior
 micro-filtration/removal of silica, alumina slurry solids, to remove
 catalytically the hydrogen peroxide (H.sub.2 O.sub.2) and then reacting
 the wastewater solution containing copper ions with an inorganic ferrous
 sulfate or aluminum sulfate to precipitate the copper.
 The process and apparatus of the present invention provide a novel process
 and apparatus for the removal of copper ions from a byproduct polishing
 slurry wastewater solution containing copper from the chemical mechanical
 polishing (CMP) of integrated circuits of semiconductor microelectronic
 chips.
 Referring now to the FIGURE, a process schematic diagram shows the metal
 ion removal process and apparatus of the present invention. A chemical
 mechanical polishing (CMP) planarization tool 10, e.g., such as in an
 integrated circuit microchip fabrication facility, discharges a wastewater
 stream 20 containing metal ions in solution, e.g., such as copper ions in
 solution. The wastewater stream 20 containing copper ions also contains
 hydrogen peroxide at levels up to about 300 ppm and higher. The hydrogen
 peroxide is used as an oxidizer to help dissolve the copper from the
 microchip. The wastewater stream 20 containing copper ions and hydrogen
 peroxide also contains suspended solids, e.g., such as silica, alumina
 slurry solids, at nominal particle diameter sizes of about 0.01-1.0 .mu.m
 and at concentration levels above about 50 mg/l (50 ppm), e.g, such as by
 way of example, in the range of about 500-2000 mg/l (500-2000 ppm)
 The wastewater stream 20 is passed to a carbon column 30. The carbon column
 30 contains granular activated carbon particles sized in the range of
 about 8.times.40 mesh. A suitable carbon is 8.times.30 mesh acid washed
 available from U.S. Filter Westates Carbon--Arizona Inc. in Parker, Ariz.
 The hydrogen peroxide of the wastewater stream 20 passes down-flow in the
 carbon column 30 and is adsorbed onto the granular activated carbon in the
 carbon column 30. A back-flow stream 32 provides for rinse and
 regeneration of carbon column 30.
 A product stream 34 from the carbon column 30 containing copper ions in
 solution and grinding (polishing) solids from the carbon column 30 is
 passed to a chemical unit operation 40. A chemical feed stream 42 passes a
 chemical feed, e.g., such as an organic dithiocarbamate to chemical unit
 operation 40 for precipitation and removal of the copper ions.
 Precipitated copper and some slurry solids may be removed through
 discharge 44. Environmentally clean wastewater slurry passes through
 wastewater discharge 46 to a municipal drain 50.
 Copper CMP wastewater contains oxidizers, dissolved copper, copper
 etchants, alumina particles, silica particles and sometimes a corrosion
 inhibitor. These constituents are contained in a background of deionized
 water. The following constituent concentrations are common.

Dissolved copper -- 5.0 mg/l
 Total suspended solids -- 1000.0 mg/l
 Oxidizing agents -- 300.0 mg/l
 Etchants -- 200.0 mg/l
 Complexing agents -- 400.0 mg/l
 DI water background -- 99%+
 TDS -- 800
 pH -- 6 to 7
 Oxidizers such as nitric acid, hydrogen peroxide, ferric nitrate, and
 ammonium persulfate are chemicals for enhancing the copper corrosion rate
 of a slurry. Other complexing agents such as citric acid or ammonium
 hydroxide help to etch the copper.
 A multiple copper CMP tool cluster generates about 100 gpm of wastewater.
 The wastewater can be fed by gravity to an influent collection tank having
 a retention time, e.g., of about 10 minutes. The collected CMP wastewater
 can be pressurized in a lift station prior to feeding to the process and
 apparatus of the present invention.
 Prior to an actual reduction to practice, it was thought that the silica,
 alumina slurry solids would foul the bed and plug the carbon column in a
 matter of hours.
 However, it has been found that the process and apparatus of the present
 invention operate unexpectedly without fouling and have been observed to
 run for 10 days and more with no pressure increase and no plugging. The
 hydrogen peroxide (H.sub.2 O.sub.2) is decomposed catalytically in the
 carbon column. Significantly less dithiocarbamate organic precipitating
 solution is required to precipitate the copper.
 The process and apparatus of the present invention remove hydrogen peroxide
 (H.sub.2 O.sub.2) and dissolved copper ions from a byproduct "grinding"
 (polishing) slurry wastewater from the metal chemical mechanical polishing
 (CMP) of integrated circuits, including high speed semiconductor
 integrated circuit microelectronic chips containing copper metal.
 EXAMPLE
 A treatability study was conducted on a series of grinding wastes from a
 variety of chemical mechanical polishing (CMP) operations for producing
 integrated circuit semiconductor microelectronic chips. Treatments were
 performed on the CMP grinding wastes received from various integrated
 circuit semiconductor microchip manufacturers. Treatments were performed
 on the CMP grinding wastes to investigate and determine copper removal
 from an alumina slurry.
 A novel method and apparatus provided a first step carbon adsorption
 removal of hydrogen peroxide from a wafer CMP planarization grinding waste
 combined with a second step chemical precipitation of complexed copper in
 the wafer planarization grinding waste. The wafer planarization grinding
 waste contained many particulate alumina solids which otherwise, i.e., if
 not for the copper, could be disposed via a municipal drain or sewer.
 Samples used during this Example were CMP wastes associated with computer
 microchip manufacturing. Several samples were used in the testing.
 Table 1 lists the samples.
 TABLE 1
 Samples Received
 Source Label
 A CMP Waste
 B CMP Waste
 C CMP Waste
 The carbon used during all carbon column testing was Calgon RX 8.times.40
 mesh (Lot 04033) available from Calgon Carbon Co. in Pittsburgh, Pa. A
 suitable equivalent carbon is 8.times.30 mesh acid washed available from
 U.S. Filter Westates Carbon--Arizona Inc in Parker Ariz. The carbon was
 prepared by degassing and rinsing. Prior to the experimental, the carbon
 was conditioned by mixing in deionized water for ten minutes to allow for
 degassing and cleaning. The carbon was allowed to settle, and the
 suspended fines were decanted off with the supernatant. This conditioning
 was repeated until the supernatant was clear and colorless with no visible
 suspensions.
 For column loading, the conditioned carbon was slurried and poured into a
 Plexiglas column having dimensions of about 1 inch diameter and 60 inches
 height. The final bed depth of the carbon was 36 inches. Deionized water
 was put through the column counter-currently to classify the carbon and
 remove any residual carbon dust.
 Three samples were put through the carbon column, "A," "B," and "C,"
 representing different manufacturing companies and separate facilities.
 One of the samples used during this test was "A" slurry previously
 concentrated using a Membralox Silverback.RTM. microfilter purification
 system available commercially from U.S. Filter Wastewater Systems, Inc. in
 Warrendale, Pa. The concentrate was re-diluted with deionized water to
 simulate as-received characteristics.
 Hydrogen peroxide was added to all of the slurry samples to accurately
 simulate expected concentrations of about 400 mg/l (400 ppm) total.
 The CMP slurry solutions containing hydrogen peroxide were passed through
 the carbon filter bed without prior removal of any of the alumina, silica
 particles in the CMP slurry solutions. During this stage of experimental,
 an influent pressure and a hydrogen peroxide content were monitored.
 A peristaltic pump was used to transfer the sample from a 55 gallon drum
 into the carbon column. The flow rate was monitored to be consistent
 throughout the experimental testing.
 During the course of the experimental testing operation, it was noted that
 gas bubbles would be forced out through the bottom effluent tube column
 rather than gassing up through the top of the carbon bed. This was
 consistent throughout the experimental testing.
 Early in the experimental, the flow was stopped overnight. Several times
 the upper portion of the carbon bed would be dry. Retaining a higher
 liquid head space prior to shutting of the pump eliminated this undesired
 condition. It is believed that gassing continued while stationary, and
 subsequently the liquid volume would fall.
 After an initial period of time, an ammonium citrate/copper solution was
 added to the slurry.
 Table 2 summarizes the results of the carbon column testing.
 TABLE 2
 Carbon Column Testing
 Bed Inlet Feed Effluent Influent Effluent
 Volumes Pressure H2O2 H2O2 Cu Cu
 8 &lt;1 -- -- &lt;1 --
 40 &lt;1 428 &lt;1 &lt;1 --
 50 &lt;2 -- &lt;1 &lt;1 --
 80 2.75 420 &lt;1 &lt;1 --
 115 2.2 -- &lt;1 &lt;1 --
 123 &lt;2 -- &lt;1 &lt;1 --
 164 2.2 -- &lt;1 &lt;1 --
 Citric Acid/Copper added
 172 &lt;2 -- &lt;1 6.9 --
 204 &lt;2 -- &lt;1 -- 0.35
 212 &lt;2 -- -- -- --
 370 &lt;2 &lt;1 -- --
 520 &lt;2 412 -- -- 5.16
 New feed ("A" slurry + 400
 H2O2 + Cu)
 529 &lt;2 -- &lt;1 -- --
 544 &lt;2 -- &lt;1 -- --
 592 &lt;2 -- &lt;1 -- 7.4
 650 &lt;2 -- &lt;1 -- 7.6
 663 &lt;2 -- &lt;1 -- --
 694 &lt;2 -- &lt;1 -- 7.1
 710 &lt;2 -- &lt;1 -- --
 726 &lt;2 -- -- -- --
 742 &lt;2 -- &lt;1 -- --
 758 &lt;2 -- -- -- --
 766 &lt;2 -- -- -- --
 774 &lt;2 -- &lt;1 -- --
 790 &lt;2 -- -- -- --
 806 &lt;2 -- -- -- --
 822 &lt;2 -- &lt;1 -- --
 838 &lt;2 -- -- -- --
 864 &lt;2 -- -- -- --
 880 &lt;2 -- &lt;1 -- --
 896 &lt;2 -- &lt;1 -- --
 912 &lt;2 -- -- -- --
 936 &lt;2 -- &lt;1 -- --
 944 &lt;2 -- &lt;1 -- --
 952 &lt;2 -- -- -- --
 968 &lt;2 -- &lt;1 -- --
 984 &lt;2 -- -- -- --
 1000 &lt;2 -- &lt;1 -- --
 The results of Table 2 showed that carbon could remove hydrogen peroxide
 from CMP slurry solutions without entrapping the alumina, silica particles
 within the filter bed.
 The novel process and apparatus of the present invention have applications
 to the precipitation and removal of metal ions other than copper from
 chemical planarization wastewater solutions. The novel process and
 apparatus of the present invention have applications to the precipitation
 and removal of metal ions such as copper, gold, platinum, palladium, iron,
 cobalt, nickel, ruthenium, rhodium, silver, osmium, iridium, and mixtures
 thereof. Preferred embodiments of the process and apparatus of the present
 invention have applications to the precipitation and removal of metal ions
 such as copper and gold.
 The process and apparatus of the present invention remove metal ions from
 wastewater by providing a carbon bed for receiving a wastewater feed
 containing metal ions in solution, wherein the wastewater feed contains
 solids sized in the range of about 0.01-1.0 .mu.m in an amount higher than
 about 100 mg/l, in combination with providing a chemical precipitation
 unit operation for receiving a carbon bed product stream from the carbon
 bed and for removing the metal ions from solution. The process and
 apparatus of the present invention remove metal ions from wastewater
 containing solids in an amount higher than about 500 mg/l, e.g., by way of
 example in an amount in the range of about 500-2000 mg/l.
 A wastewater feed containing hydrogen peroxide and metal ions in solution
 is passed to the carbon column to reduce the concentration of the hydrogen
 peroxide and form a carbon bed effluent having concentration levels of
 hydrogen peroxide, preferably to a level less than about 1 mg/l (1 ppm).
 In one aspect, the metal ions are copper ions. In one aspect, the metal
 ions are copper ions at a concentration level in the range of about 1-100
 mg/l.
 The chemical precipitation unit operation includes means for contacting
 metal ions in the carbon bed product stream with an organic carbamate to
 precipitate the copper ions. In one embodiment, the organic carbamate
 includes dithiocarbamate.
 In an alternative embodiment, the chemical precipitation unit operation
 includes means for contacting metal ions in the carbon bed product stream
 with an inorganic iron sulfate (FeSO.sub.4) or aluminum sulfate (Al.sub.2
 (SO.sub.4).sub.3) to precipitate the copper ions.
 The process and apparatus of the present invention operate to remove metal
 ions from a wastewater from a byproduct polishing slurry. In one
 embodiment, the process and apparatus of the present invention operate to
 remove metal ions, e.g., such as copper metal ions, from a wastewater from
 a byproduct polishing slurry from the chemical mechanical polishing (CMP)
 of integrated circuits to precipitate the metal ions and form an
 environmentally clean water discharge product. By environmentally clean is
 meant a wastewater discharge stream to a municipal wastewater treatment
 plant such that the wastewater discharge stream contains copper ions in a
 concentration less than about 0.5 mg/l (0.5 ppm).
 While the invention has been described in conjunction with several
 embodiments, it is to be understood that many alternatives, modifications,
 and variations will be apparent to those skilled in the art in light of
 the foregoing description. Accordingly, this invention is intended to
 embrace all such alternatives, modifications, and variations which fall
 within the spirit and scope of the appended claims.