Transcript No Slide Title

Treatment of CMP Waste Streams
B.M. Belongia, Y. Sun
Dr. J.C. Baygents, Dr. S. Raghavan
The University of Arizona
Joe O’Sullivan
Pall Corp.
 1999 Arizona Board of Regents for The University of Arizona
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Outline
• Background
• Treatment Strategies
• Electrocoagulation/Electrodecantation Studies
– pH Effects & Electrode Compartments
– Solid/Liquid Separation
– Copper Removal
• Cross-flow filtration
– MicrozaTM UF Systems
• Summary
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Significance
• Large quantities of waste slurry generated from CMP
– ~ 6 L of waste slurry generated per wafer
– 0.1 - 0.5 % solids and ~ 40 ppm copper ions
• Efficient disposal or recycle strategies need to be
developed to comply with environmental regulations.
• Recycling would require that the dilute waste slurry be
concentrated to the initial slurry solids content and the
particle size remain unchanged.
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Slurry Types
• Oxide slurry
– Silica is the abrasive material
– Suspension is stabilized with either NH4OH or KOH;
pH = 10 - 11
– Used to polish oxide layers
– Particle size: 50-100 nm
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Slurry Types (cont’d)
• Metal
– Abrasive is primarily aluminum oxide, but some
contain silica
– Contains an oxidizer, either ferric nitirate, potassium
iodate or hydrogen peroxide
– pH = 3 - 5
– Used to polish tungsten and copper (recently popular)
interconnects
– Particle size: 100 - 300 nm
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Why Treat CMP Wastewater?
• Suspended solids too high to discharge to sewer
• Traditional flocculation and clarification requires large
tanks and lots of chemical addition
• A need to reclaim water at the individual facility
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NEW SLURRY
6–10wt% solids
RINSE
WATER
WATER TO
POLISHING
LOOP
SLURRY
POLISHING
TOOL
WATER
USED
SLURRY
MIRACULOUS PROCESS!
0.02–0.5wt% solids
2 –40ppm Cu
SOLIDS
WASTE
SOLIDS
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Treatment Objective
• To develop a generic methodology for the treatment of
CMP waste streams.
e.g. a copper CMP waste may contain:
• 0.02 – 0.5% solids
• 2 – 40ppm copper ions
• An organic complexant (e.g. EDTA, Citric Acid)
• A corrosion inhibitor (e.g. BTA)
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Treatment Strategies
1. Electrocoagulation/Electrodecantation (EC/ED)
– University of Arizona research
– Possible follow on to ultrafiltration
2. Cross-flow filtration
– Pall MicrozaTM ultrafiltration system
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EC/ED
• Electrocoagulation
– used to treat waste steams; electric field applied for a
short period, suspension allowed to settle in absence
of field — rate of settling was found to be enhanced
• Electrodecantation
– used to concentration proteins, viruses, natural rubber
latex, and various inorganic sols
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EC/ED Apparatus
Sample Port
Cathode (-)
(Stainless Steel)
Suspension
Membrane
Water
Anode (+)
(Stainless Steel)
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Electrode Reactions
Membrane
(+) Electrode
2H20 
4H+ + 4e- + O2
Water
pH decreases
(-) Electrode
2H+ + 2e-  H2
or
2H2O + 2e- 
H2 + 2OHSuspension
pH increases
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pH Changes
4
3.5V/cm
1
0
pH
8
Cathode Chamber
Anode Chamber
6
4
2
0
3
6
9
Time (min)
1
2
1
5
Electrophoretic Mobility of Al2O3
cm2/V·s  10-4
1
2
3
2
1
0
1
2
3
1mM KNO3
4
23456789
1
0
1
1
1
2
pH
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EC/ED of Al2O3
1
.
0
Membrane
0
.
9
Liquid
Level
0
.
8
0
.
7
c/c0
0
.
6
Anode
0
.
5
Clarified
Liquid
(Sample Zone)
Cathode
Solids
0
.
4
0
.
3
 1.75V/cm
 3.50V/cm
 7.00V/cm
 14.00V/cm
0
.
2
0
.
1
0
.
0
0 1
53
04
56
07
59
0
Time (min)
Initial Cond.  1300 mS/cm
Initial pH  6.0
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Copper Removal during EC/ED
1
.
0
Initial Cond.  1300 mS/cm
Initial pH  6.0
0
.
9
0
.
8
cCu/c0Cu
0
.
7
0
.
6
0
.
5
0
.
4
0
.
3
0
.
2
0
.
1
0
.
0
0 1
53
04
56
07
59
0
 1.75V/cm
 3.50V/cm
 7.00V/cm
 14.00V/cm
Time (min)
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Copper Distribution
Membrane
Initial Suspension
220ml @ 34ppm Cu
165 ml
4.2ppm Cu (9.7%)
97 ml
16.0ppm Cu (20.5%)
Anode
Cathode
Plated Cu (16.3%)
44ml
68.0ppm Cu (39.4%)
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Effect of EDTA and Cu on Al2O3
Particle Charge
+
2
Al2O3
1
0
+
+
+
+
-
-
-
pH  6
-+
-
1
-
Al2O3
2
-
+
Cu2+
Electrophoretic Mobility
cm2/V·s  10-4
3
+
+
Cu2+
4
3
4
2
1
1
1
0
1
23456789
pH
 Al2O3
 Al2O3 + 184ppm EDTA
 Al2O3 + 40ppm Cu
+ 184ppm EDTA
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Copper Distribution
pH  6
Membrane
Cu2+
(EDTA)2[(EDTA)Cu]-
OH
OH
OH
Cu(OH)2
OH
OH
OH
OH
Anode
OH
OH
OH
Cathode
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EC/ED of Concentrated
Al2O3 Wastes
1
.
0
0
.
9
Membrane
c0 12% solids
0
.
8
Clarified
Liquid
0.5% solids
c/c0
0
.
7
0
.
6
0
.
5
Cathode
0
.
4
0
.
3
Anode
0
.
2
Solids 29%
0
.
1
0
.
0
Initial pH  6.0
0 1
53
04
56
07
59
0Initial Cond.  1300 mS/cm
Time (min)
3.50V/cm
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Filtration and EC/ED in Tandem
Recirculated
Suspension
Waste
Highly Concentrated
Suspension
Cross-flow
filtration
Water
Electrocoagulation
Apparatus
Permeate
Solids
 Pall Corp. patented technology to treat CMP waste.
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Summary of EC/ED Method
• Alumina suspension can be dewatered by EC/ED.
• Copper can be simultaneously removed from the
clarified layer.
– plating out onto the cathode
– in situ precipitation?
• pH changes are critical to the success of the EC/ED
process.
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Work (kW·hr/l)  10-3
Cost and Power Consumption
3
0
0
(Using $0.05/kWhr)
2
8
0
 1.75V/cm
2
6
0
 3.50V/cm
2
4
0
 7.00V/cm
For 7.0V/cm, 90mins
2
2
0
2
0
0
Cost: $0.014/l
1
8
0
$0.08/wafer
1
6
0
1
4
0
@ 6 l/wafer
1
2
0
1
0
0
For 3.5V/cm, 90mins
8
0
6
0
Cost: $0.002/l
4
0
$0.01/wafer
2
0
0
@ 6 l/wafer
0 1
53
04
56
07
59
0
Time (min)
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What is Ultrafiltration?
Feed
Retentate
Membrane
Solute A
Solute B
Permeate
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Factors Affecting Separations
10
MICROFILTERS
SIZE
DIFFUSIVITY
IONIC CHARGE
DENSITY
1
Micron (µm)
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Cross Section of MicrozaTM Hollow
Fiber Membrane
Uniform outer surface skin further
improves mechanical properties,
facilitates design and provides extra
assurance of removal efficiency
Macroporous regions allow low
pressure differential and
enhanced flow rate.
Uniform skinned membrane with
narrow pore range for highly
efficient separation
characteristics.
Dense porous layer provides
exceptional mechanical strength
and fiber reliability.
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MicrozaTM UF Systems
• Process dilute CMP wastewater
– 0.02% to 0.1% total suspended solids
• Treat oxide, metal or mixture of waste
• Concentrate all suspended solids
– up to 15-17%
• Permeate is free of suspended solids
– can pretreat to remove ferric ion and soluble silica
– can use as RO makeup water
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Challenges of Treating CMP Wastewater
• Abrasive material
– expect 18-24 months service life on UF modules
• Broad pH range
– oxide, metal or mixed waste
– polyacrylonitrile membrane, pH 2-10
• Prevention of membrane fouling
– high linear velocity
– reverse filtration
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Portable MicrozaTM CMP Test System with
Single 0.1 m2 UF Module
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Chemical Treatment for Removal of
Soluble Silica
• Formation of silicate
• Precipitation of magnesium/iron silicate
– iron silicates pH 8-9
– magnesium silicates pH 10.5-11
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Silica Solubility vs. pH
900 1000
,
Silica Solubility (mg/L)
800
700
600
500
400
,
300
200
, , ,
100
0
0
2
4
,
6
pH
,
,
,
8
10
12
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Chemical Treatment for Removal of
Soluble Silica (cont’d)
• Holding tank upstream of UF system
• Typical reaction time of 30 minutes
-
SiO2
+
2KOH
NaOH + MgCl
Mg (OH)2
+ H2 SiO3
SiO3
(silicate) + 2K
+
Mg (OH)2
MgSiO3 (s) + 2H2 O
Magnesium
Silicate
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Chemical Treatment for the Removal of
Ferric Ion
• Form hydroxy complexes in acidic media
– yellow-orange in color
• Neutralization results in hydrous ferric oxide
– reddish-brown precipitate
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Chemical Treatment for the Removal of
Ferric Ion (cont’d)
• Caustic injection upstream of UF system
• Instantaneous reaction
2 Fe (H2 O)5 (OH)2+ +
yellow-orange in color
4 OH-
Fe2 O3 . 13 H2 O
hydrous ferric oxide
reddish-brown
precipitate
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Copper CMP Waste
•
•
•
•
•
Abrasive is primarily aluminum oxide
Contains an oxidizer, typically hydrogen peroxide
pH = 3
Used to polish copper interconnects
particle size: 100-300 nm
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Treatment of Copper CMP Waste
• Soluble copper
– Assuming 5000 wafer starts per week with five levels
of copper results in 6 kg of copper per week
– Classified as both metal finishing waste and
semiconductor waste
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Removal of Soluble Copper
• Precipitation of Cu(OH)2 by Addition of Caustic
• Removal of Copper by I/E
– Conventional treatment method in Printed Circuit
Board Industry and Plating Industry
– Achievable Effluent Levels of < 0.1 ppm of copper
– 10K Gallons of Water per cubic foot of resin at a
influent level of 10 ppm copper
– Electrowinning of copper
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Turn-key System for Treatment of
Copper CMP Waste
• Removal of suspended solids by UF
• Removal of Soluble copper by I/E and possibly
electrowinning
• Further treatment required to generate RO-ready water
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Schematic of a Water Reclamation System
from CMP Waste Slurry
CMP WASTE
SLURRIES
from
POLISHERS
BUFFER
TANK
MICROZA
UF System
PERMEATE
REVERSE
OSMOSIS
and/or
ION EXCHANGE
REJECT
RECLAIMED
RECLAIMED
WATER
WATER
TO WASTE
TREATMENT
CONCENTRATION
CONCENTRATE
PRE-TREATMENT
FILTER
PRESS
FILTRATE
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Dewatering of UF Concentrate
• UF Concentrate
– Maximum of 17% Total Suspended Solids
• Dewatering Via a Filter Press for Landfill Disposal
– Treat with Fluoride Waste
– Treat Separately
• RCRA Paint Filter Test
• Non-Hazardous Material
• pH Adjustment
• Addition of coagulant
• Addition of flocculant
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Flux Profile for UF System
Typical for Mixed CMP Slurry Waste
Flux vs. Concentration Factor (X)
90
45.0
Flux
40.0
X (2ndY)
70
35.0
60
30.0
50
25.0
40
20.0
30
15.0
20
10.0
10
5.0
0
Conc Factor
Flux, lmh
80
0.0
0
1
2
3
4
5
6
7
Time, hr
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Buffered Tank Management
Sized for 20 m3/hr of Mixed CMP Waste
35
Tank Volume (liters x 1,000)
PROCESS TANK FILL @
CONCENTRATION START
Feed/Process Tank
30
Buffer Tank
25
BUFFER TANK
TANK REFILLING
UF CONCENTRATION
& PROCESS TANK FILLING
20
FEED TANK CMP SLURRY
PROCESSING VOLUME
STOP PROCESS
TANK FILL
15
10
UF CONCENTRATION
IN PROCESS TANK
5
UF DRAIN
& RINSE
0
0
1
2
3
4
5
6
7
8
Time (hours)
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Typical MicrozaTM CMP Waste Slurry
Concentrating Installation
(Single UF Module Skid)
WASTE SLURRY FEED
FROM CMP TOOLS
UF RINSE
TRANSFER
BUFFER
TANK
PERMEATE
FORWARD
RF PERMEATE
PROCESS PERMEATE
PREFILTER
F-1
FEED
RETENTATE
UF RACK
No.1
FEED/BATCH
TANK
TRANSFER
PUMP
FEED RECIRCULATION
PUMP
PUMP
UF RACK
No.2
REVERSE
FILTRATION
TANK
RF/PERMEATE
PUMP
DRAIN
CONCENTRATE DRAIN
PUMP
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MicrozaTM CMP Waste Slurry Installation
(Multiple UF Module Skids)
WAST E SLURRY FEED
FROM CMP T OOLS
RF PERMEAT E
PROCESS PERMEAT E
UF RINSE
T RANSFER
PERMEATE
FORWARD
PREFILTER
F-1
BUFFER
TANK
FEED
RET ENT AT E
UF SKID
No.1
FEED/BATCH
TANK
UF SKID
No.2
REVERSE
FILTRATION
TANK
RECIRC ULATION
PUMP
TRANSFER
PUMP
RF/PERMEATE
PUMP
FEED
PUMP
DRAIN
CONCENTRATE
DRAIN
PUMP
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Microza UF System Sizing
Oxide CMP Waste
Initial Conc
VCF
Percent
Recovery
0.1 %
10X
90
20
5
0.1%
50X
98
20
6
0.2%
10X
90
20
5
0.1%
10X
90
50
13
0.1%
50X
98
50
16
Flowrate (GPM) # of Modules
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Microza UF System Sizing
Mixed Oxide and Mixed Metal CMP Waste
Percent Flowrate (GPM)
Recovery
# of
Modules
Initial Conc
VCF
0.1 %
10X
90
20
7
0.1%
50X
98
20
8
0.1%
10X
90
50
18
0.1%
50X
98
50
21
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