CMP Pump Effects on Filter Life

Transcription

1 CMP Pump Effects on Filter Life Rakesh K. Singh, Ph.D., P.E. Mykrolis Corporation Mykrolis Corporation, Rakesh K. Singh 1

2 Acknowledgments Slurry manufacturers for providing CMP slurry and abrasive dispersion samples for various studies Beckman Coulter for making available a LS 230 analyzer for Particle Size Distribution Measurements Levitronix GmbH for providing a magnetically levitated centrifugal pump for slurry handling studies Christopher Wargo, Craig Lazinsky, Dr. Bipin Parekh and Dr. Ben Roberts for their contributions to this work Mykrolis Corporation, Rakesh K. Singh 2

3 Overview Motivation CMP Slurry Metrology, Handling and Filtration Challenges Slurry Filtration Methodologies and Design Considerations Slurry Filtration Physics - Future Directions Effects of Extensive Pump Handling on CMP Slurries Results of Large Particle Concentration and Filter Lifetime Summary and Conclusions Mykrolis Corporation, Rakesh K. Singh 3

4 Motivation CMP processes and consumables must continue to improve Decreasing feature size and increasing number of metal layers Introduction of larger wafer, copper, ultra low-k and noble metals Lower defectivity, higher yield and reduced cost of ownership Important to maintain slurry blend consistency and quality over time Achieve more uniform and efficient global and local wafer planarization Real-time CMP slurry blend quality monitoring and control requirements Subsystems and filtration may help with slurry pot-life and time sensitivity Significantly different handling and filtration demands of newer slurries Much lower abrasive content and mean particle sizes of new slurries Stringent specifications of point-of-use and global loop slurry filtration More efficient handling, flow and large particle management of slurries Mykrolis Corporation, Rakesh K. Singh 4

5 Slurry Metrology, Handling and Filtration Challenges Challenges: Tighter blend accuracy and control requirements Quick settling characteristics and limited post-blend useful life Variability in the slurry and chemical properties of different lots Uncertainties of oxidizer decay and adjustments with time Strict particle counts, size distribution and filtration requirements Detection and removal of hard large particles at very small concentrations Development of end-pointing technique to control dishing and erosion Slurry health or quality and mix ratio monitoring parameters: Large (> 0.56 or 1.01 micron) particle counts (LPC) Particle size distribution (PSD) and zeta potential ph, ORP, conductivity, viscosity and refractive index Total dissolved solids, wt % solids and density or specific gravity Oxidizer concentration and ionic contamination Oxide slurries: agglomeration, filtration, density, PSD and LPC Tungsten and copper slurries: settling, oxidizer level, density and LPC Mykrolis Corporation, Rakesh K. Singh 5

6 CMP Slurry Filtration: Defect Reduction and Process Improvement There are large particles (>10x of d 50 ) in CMP slurries that can cause defects (microscratches) and yield losses Slurry suppliers have implemented filtration to eliminate those particles in manufacturing Large particles tend to slowly reform due to instabilities in chemistry and handling & distribution Objective of CMP Slurry Filtration To remove large particles and agglomerates from slurry that can cause defects, without changing slurry polishing performance Relative Number of Particles Bulk Particle Concentration 15 >10 Particles/ml Defect-Causing Large Particles 10 4 to 106 Particles/ml Particle Size (nm) Mykrolis Corporation, Rakesh K. Singh 6 Gel Particles

7 CMP Slurry Filtration: Changed Process Needs and Slurry Mean Particle Sizes New generation slurries filtration targets tighter retention of large particles at much smaller large-particle cut-off (e.g., 0.5 or 0.3 µm) More consistent flow and pressure drop behavior, and longer filter lifetime Minimal effects on the mean working particles for better local and global planarity, and repeatability in CMP processing D50 (mean size) D99 Earlier 0.20 µm 1 µm New Target Next Target 0.16 µm 0.5 µm 0.06 µm 0.3 µm Mykrolis Corporation, Rakesh K. Singh 7

8 CMP Slurry Filtration Methodology and Mechanisms Slurry Filtration Process CMP filtration is actually a separation process Filters have difficulty separating particles that are less than 1 order of magnitude different in size Don t think of filters as strainers working only by size exclusion, there are other important mechanisms Inertial impaction, Interception, Adsorption/Adhesion, Diffusion, Gravitational settling There are also effects tied to how the media is arranged in the filter 100% Retention Ideal filter with sharp cut-off Typical retention curve 0 Particle Size Mykrolis Corporation, Rakesh K. Singh 8

9 Filter Design and Particle Retention Filter Design Filter design is set by the needs of the fluid challenge: particle size distribution affects the optimum design Goal is to fill the available cylindrical volume uniformly with particles As the particle concentration increases in an area the flow rate decreases in that area Capture of particle in a narrow particle size range calls for use of pleated cartridge designs Capture of particle in a wide particle size range calls for depth of media accommodated by wrapped or layered designs Mykrolis Corporation, Rakesh K. Singh 9

10 Filter Media and Configurations Filter Media Flow Core Wraps Vent Flow Out Cartridge element Tighter filter media More open media Drain Flow In Tighter filter media More open media Typical graded density depth media for CMP slurry filtration Typical depth filter housing arrangement and a pleated depth filter configuration Mykrolis Corporation, Rakesh K. Singh 10

11 Filtration Physics - Extending Filter Lifetime Filter Retention Flow Out 100% Retention Ideal filter with sharp cut-off Effect of each new layer Tighter filter media More open media 0 Particle Size (a) (b) Flow In Each layer improves the probability of capture at the larger sizes faster than it does for the smaller particle sizes Sharper curves improve separation and increase life As a filter loads the compression of the media will change the filtration performance making it more retentive Designs that prevent this in-use compression will also have longer life Mykrolis Corporation, Rakesh K. Singh 11

12 Filtration Physics - Extending Filter Lifetime (Cont...) Layering of media also provides far greater depth than traditional designs 100% Flow Out 80% Retention 60% 40% 20% CMP5 & CMP3 Solaris SLR03 Tighter filter media More open media 0% Particle Size (mm) Planargard CMP3 & CMP5 are typical graded-density wrapped depth media filters Solaris is a multiple layered design providing extreme depth for extended lifetime Mykrolis Corporation, Rakesh K. Singh 12 Flow In

13 Slurry Filtration Physics - Future Directions Multiple layered designs can be optimized further: Conduct more experiments with layering to improve performance Employ designs with lower face velocities and shapes that fit into equipment more easily Pursue better media: Filter theory shows that finer fibers provide better retention at a constant pressure drop Currently the smallest diameter fibers used in CMP are meltblown nonwovens Other technologies exist that can provide finer fibers (non-glass), but for now they are not cost effective/practical Consider other filtration models: With significantly more dilute slurries, it may be possible to consider TFF designs With more chemically aggressive slurries: There may be better designs for both ease of use and elimination of stainless steel from wetted flow paths Mykrolis Corporation, Rakesh K. Singh 13

14 Slurry Filtration Characterization Retention/Flow and Pressure Drop Test Retention test conducted with PSL beads solution and CMP slurries and pressure drop tests at 0, 1, 2, 3, 4 GPM using a differential pressure unit Lifetime Test Testing with CMP slurries and pressure drop and flow rate measurements till pressure drop reaches a specified limit Recirculation Loop Test Evaluation of global loop and POU filters using a vacuum-pressure dispense system as well as bellows, diaphragm, a magnetically levitated centrifugal pumps Collaborative Testing with Slurry Vendors and Customers Field returned filter analysis and troubleshooting Extent of filter plugging/remaining lifetime by p and weight gain SEM and ESEM (environmental SEM, for wet sample imaging) analysis Filter Related Troubleshooting at Site Mykrolis Corporation, Rakesh K. Singh 14

15 Test Set-up for Single Pass POU Operation Pump Depth Filter Pressure Gauge, P1 Pressure Gauge, P2 Weight Scale Slurry Supply Tank Mykrolis Corporation, Rakesh K. Singh 15

16 Slurry and Filter Characterization in a Simulated Recirculation Loop Discharge Dampener 25 Foot Long PFA Tubing Coil Pump DI Water Pinch Valve Chiller Supply Tank Collection Tank Distribution Loop Filter POU Filter In Centrifugal Pump Test Only Schematic of Recirculation Loop Test Set-Up Mykrolis Corporation, Rakesh K. Singh 16

17 Filter Lifetime Monitoring Pressure Drop Across the Filter Filter lifetime can be monitored by Differential pressure across the filter Flowrate through the filter under a given system pressure Filter change-out region Time or Volume Given Filter s lifetime depends on Gel concentration and particle loading in slurry Batch-to-batch variability Flowrate Delivery system pressure characteristics Mykrolis Corporation, Rakesh K. Singh 17

18 Effects of Extensive Pump Handling on CMP Slurries Mykrolis Corporation, Rakesh K. Singh 18

19 PSD and LPC data for silica slurry 1 under extensive handling in a bellows pump loop at 36 turnovers/hr Differential Volume (%) Hours in pump loop 0 hour, source 1 5 minutes 2 hours 8 hours 20 hours 31 0 hours 361 hours Normalized # of Particles (> = Diameter) source 20 hours 69.5 hours 213 hours 310 hours 334 hours (Courtesy of BOC Edwards: Singh & Roberts, ASMC 2001) Mykrolis Corporation, Rakesh K. Singh 19

20 PSD and LPC data for silica slurry 1 during handling in a vacuum-pressure dispense pump loop at 36 turnovers/hr Differential Volume (%) hour, source 1 5 minutes 2 hours 8 hours 21 hours 70 hours hours 1 65 hours Normalized # of Particles (> = Diameter) source 1 h o u r 21 hours 70 hours hours 193 hours (Courtesy of BOC Edwards: Singh & Roberts, ASMC 2001) Mykrolis Corporation, Rakesh K. Singh 20

21 PSD and LPC data for alumina slurry 1 under extensive handling in a bellows pump loop at 14.5 turnovers/hr Differential Volume (%) source 5 minutes 5 hours 42.5 hours 90 hours Normalized # of Particles (> = Diameter) Hours in pump loop 0 hour 2 minutes 1 hour 65.5 hours 90 hours (Courtesy of BOC Edwards: Singh & Roberts, ASMC 2001) Mykrolis Corporation, Rakesh K. Singh 21

22 PSD and LPC data for alumina slurry 2 under extensive handling in a bellows pump loop at 37.5 turnovers/hr Differential Volume (%) source 5 minutes 1 hour 64 hours 128 hours Normalized # of Particles (> = Diameter) Hours in pump loop 0 hour 1.5 hour 3 hours 21 hours 39 hours 51 hours 64 hours 1 28 hours (Courtesy of BOC Edwards: Singh & Roberts, ASMC 2001) Mykrolis Corporation, Rakesh K. Singh 22

23 LPC and PSD data for ceria slurry 1 and silica slurry 2 under extensive handling in bellows pump loop LPC data for ceria slurry 1 in bellows pump loop at 41.3 turnovers/hr PSD data for silica slurry 2 in bellows pump loop at 85 turnovers/hr Normalized # of Particles (> = Diameter) Source, 0 hours 5 minutes 1 hour 7 hours 31 hours 54 hours hours hours Differential Volume (%) source 6 hours 69 hours hours (Courtesy of BOC Edwards: Singh & Roberts, ASMC 2001) Mykrolis Corporation, Rakesh K. Singh 23

24 LPC data for silica slurry 3 under extensive handling in a vacuum-pressure dispense system and bellows pump loop LPC data for silica slurry 3 a vacuum-pressure dispense system at 17.1 turnovers/hr LPC data for silica slurry 3 in bellows pump recirculation loop at 60 turnovers/hr hour 5 minutes 24 hours 72 hours 140 hours 162 hours hour 5 minutes 2 hours 18 hours 24 hours 42 hours (Ref: Singh, Conner and Roberts, SST 2004) Mykrolis Corporation, Rakesh K. Singh 24

25 LPC data for silica slurry 4 under extensive handling tests in BPS-3 3 magnetically levitated centrifugal pump loop Test 1: 8000 rpm, 28 psi back pressure, 31.7 turnovers/hr, 8 lpm, up to 45 hr samples Test 1: 8000 rpm, 28 psi back pressure, 31.7 turnovers/hr, up to 4.5 hr samples (0.05 ml slurry added in 30 ml Accusizer flask) (0.05 ml slurry added in 30 ml Accusizer flask) 1.2E E E E E E+04 0 Turnovers 63.4 Tunovers 143 Turnovers 523 Turnovers 761 Turnovers 1427 Turnovers 1.0E E E E E+03 0 Turnovers 63.4 Tunovers 143 Turnovers Mykrolis Corporation, Rakesh K. Singh 25

26 LPC data for silica slurry 4 under extensive handling tests in BPS-3 3 magnetically levitated centrifugal pump loop Test 1: 8000 rpm, 28 psi back pressure, 31.7 turnovers/hr, 8 lpm, up to 330 hr samples Test 2: 8000 rpm, 28 psi back pressure, 63.4 turnovers/hr, 8 lpm, up to 20 hr samples (0.02 ml slurry added in 30 ml Accusizer flask) (0.02 ml slurry added in 30 ml Accusizer flask) 2.0E E E E+04 0 Turnovers 143 Tunovers 2156 Turnovers 2948 Turnovers Turnovers 2.0E E E E+04 0 Turnovers 31.7 Tunovers 63.4 Turnovers 127 Turnovers 1270 Turnovers Mykrolis Corporation, Rakesh K. Singh 26

27 LPC data for silica slurry 4 under extensive handling tests in BPS-3 3 magnetically levitated centrifugal pump loop Test 1: 8000 rpm, 28 psi back pressure, Test 2: 8000 rpm, 28 psi back pressure, turnovers/hr, 8 lpm, up to 4.5 hr samples turnovers/hr, 8 lpm, up to 2 hr samples 4.0E E E E+03 0 Turnovers 143 Tunovers 4.0E E E E+03 0 Turnovers 31.7 Tunovers 63.4 Turnovers 127 Turnovers Mykrolis Corporation, Rakesh K. Singh 27

28 LPC data for silica slurry 4 under extensive handling tests in BPS-3 3 magnetically levitated centrifugal pump loop Test 2: 8000 rpm, 28 psi back pressure, 63.4 turnovers/hr, 8 lpm, up to 20 hr samples Test 3: 5000 rpm, 10 psi back pressure, 39.6 turnovers/hr, 5 lpm, up to 24 hr samples (0.02 ml slurry added in 30 ml Accusizer flask) (0.02 ml slurry added in 30 ml Accusizer flask) 6.0E E E E E E+04 0 Turnovers 31.7 Tunovers 63.4 Turnovers 127 Turnovers 1270 Turnovers 6.0E E E E E E+04 0 Turnovers 19.8 Tunovers 39.6 Turnovers 851 Turnovers 950 Turnovers 3.0E E E E E E+02 0 Turnovers 31.7 Tunovers 63.4 Turnovers 127 Turnovers 1270 Turnovers 3.0E E E E E E+02 0 Turnovers 19.8 Tunovers 39.6 Turnovers 851 Turnovers 950 Turnovers Mykrolis Corporation, Rakesh K. Singh 28

29 LPC data for silica slurry 4 under extensive handling tests in BPS-3 3 centrifugal pump and diaphragm pump 1 Test 2: 8000 rpm, 28 psi back pressure, 8 lpm, 63.4 turnovers/hr, 20 hr test, BPS-3 3 pump Test 4: 28 psi back pressure, 8 lpm, 63.4 turnovers/hr, 24 hr test, diaphragm pump 1 (0.02 ml slurry added in 30 ml Accusizer flask) (0.02 ml slurry added in 30 ml Accusizer flask) 2.0E E E E+04 0 Turnovers 31.7 Tunovers 63.4 Turnovers 127 Turnovers 1270 Turnovers 2.0E E E E+04 0 Turnovers 31.7 Tunovers 63.4 Turnovers 127 Turnovers 380 Turnovers 1395 Turnovers Mykrolis Corporation, Rakesh K. Singh 29

30 LPC data for silica slurry 4 under extensive handling tests in diaphragm pump 1 at different turnover rates Test 5: 28 psi back pressure, 31.7 turnovers/hr, Test 4: 28 psi back pressure, 63.4 turnovers/hr, 8 lpm, diaphragm pump 1, up to 184 hr samples 8 lpm, diaphragm pump 1, 24 hr test 2.5E E E E E+04 0 Turnovers 31.7 Tunovers 143 Turnovers 761 Turnovers 1427 Turnovers 5833 Turnovers 2.5E E E E E+04 0 Turnovers 31.7 Tunovers 63.4 Turnovers 380 Turnovers 1395 Turnovers 1522 Turnovers Mykrolis Corporation, Rakesh K. Singh 30

31 LPC data for silica slurry 4 under extensive handling tests in diaphragm pumps 1 and 2 at same turnover rates Test 4: 28 psi back pressure, 63.4 turnovers/hr, Test 6: 28 psi back pressure, 63.4 turnovers/hr, 8 lpm, diaphragm pump 1, 6 hr samples 8 lpm, diaphragm pump 2, 6 hr samples 5.0E E E E E+04 0 Turnovers 31.7 Tunovers 63.4 Turnovers 127 Turnovers 380 Turnovers 5.0E E E E E+04 0 Turnovers 31.7 Tunovers 63.4 Turnovers 127 Turnovers 380 Turnovers Mykrolis Corporation, Rakesh K. Singh 31

32 LPC data for silica slurry 4 in single-pass POU filtration tests with fresh and extensively handled slurry Test 7: Fresh silica slurry 4 feed and fltrate LPC for Planargard CMP3 and CMP5 filters 3.0E E E E E E+04 Feed CMP5 Filtrate CMP3 Filtrate Feed CMP5 Filtrate CMP3 Filtrate Test 8: Slurry feed and fltrate LPC for CMP3 and CMP5 filters (6 hour diaph pump 2 Test 6: 63.4 turnovers/hr handling of silica slurry 4) 3.0E E E+04 Mykrolis Corporation, Rakesh K. Singh 32 Feed Test 6 CMP5 Filtrate CMP3 Filtrate Test 8: p at ~ 542 ml/min, CMP5 ~ 1.8 psi, CMP3 ~ 4.1 psi Test 7: p at ~ 557 ml/min, CMP5 ~ 1.8 psi, CMP3 ~ 4.4 psi

33 LPC data for silica slurry 4 in single-pass POU filtration tests with BPS-3 3 pump (2 speeds) extensively handled slurry Test 9: Slurry feed and fltrate LPC for CMP3 Test 10: Slurry feed and fltrate LPC for CMP3 and CMP5 filters (20 hour Test 2: 8000 rpm, and CMP5 filters (24 hour Test 3: 5000 rpm, 63.7 turnovers/hr handling of silica slurry 4) 39.6 turnovers/hr handling of silica slurry 4) 3.0E+03 Feed Test 2 3.0E+03 Feed Test 3 2.0E E+03 CMP5 Filtrate CMP3 Filtrate 2.0E E+03 CMP5 Filtrate CMP3 Filtrate Test 9: p at ~ 529 ml/min, CMP5 ~ 1.7 psi, CMP3 ~ 3.9 psi Test 10: p at ~ 548 ml/min, CMP5 ~ 1.9 psi, CMP3 ~ 4.1 psi Mykrolis Corporation, Rakesh K. Singh 33

34 LPC data for silica slurry 4 under extensive handling tests in BPS-3 3 and diaphragm pump 1 Test 9: Slurry feed and fltrate LPC for CMP3 Test 11: Slurry feed and fltrate LPC for CMP3 and CMP5 filters (20 hour BPS-3 3 Test 2: 8000 and CMP5 filters (24 hour diaphragm pump 1 rpm, 63.4 turnovers/hr of silica slurry 4) Test 4: 63.4 turnovers/hr of silica slurry 4) 3.0E E E+03 Feed Test 2 CMP5 Filtrate CMP3 Filtrate 3.0E E E+03 Feed Test 4 CMP5 Filtrate CMP3 Filtrate Test 9: p at ~ 529 ml/min, CMP5 ~ 1.7 psi, CMP3 ~ 3.9 psi Test 11: p at ~ 546 ml/min, CMP5 ~ 2.3 psi, CMP3 ~ 4.3 psi Mykrolis Corporation, Rakesh K. Singh 34

35 Summary and Conclusions Current and next generation CMP slurries target tighter retention of large particles at much smaller large-particle cut-off (e.g., 0.5 or 0.3 µm) and well-characterized graded density depth filters can effectively manage large particles in these slurries. Optimum slurry delivery and filtration should consider slurry abrasive type and composition, chemical additives, LPC, PSD, wt % solids, viscosity, abrasive settling, target retention level, pressure-drop, flow rate, filter lifetime, and the distribution system pump characteristics. Bellows and diaphragm pump recirculation tests show that silica-based (shear-sensitive) CMP slurries generate significant large particles, whereas alumina and ceria-based STI CMP slurries do not generate large agglomerates under extensive shearing/handling. A vacuumpressure dispense technology pump was found to generate fewer large particles as compared to a bellows pump in a silica slurry handling test. A magnetically levitated centrifugal pump (Levitronix BPS-3) was found to generate far fewer large particles (> 1 micron) as compared to diaphragm and bellows pumps in silica slurry tests for the comparable turnovers. Almost no increase in large particle was seen for this pumps at moderate speed and back pressure in a silica slurry extensive handling test. Mykrolis Corporation, Rakesh K. Singh 35

36 Summary and Conclusions (Cont...) As expected, in extreme repeated handling situations with limited slurry in the system and very high pump speeds, large growth in particles > 0.5 and < 1 micron was noticed in the BPS-3 tests. It is important to note that such handling conditions are not likely to occur in most practical applications. The above behavior of LPC may be attributed to the cumulative effects of low-intensity uniform shear application at very high pump speeds. Since, BPS-3 pump generated far fewer >1 micron particles in shear sensitive slurry, the filter lifetime for this pump based slurry delivery systems should be longer than other approaches, when relatively open filters are used in global distribution loop. However, more extensive fab based studies would be needed to confirm this behavior. Results of present study demonstrate the significant advantages of magnetically levitated centrifugal pumps in handling shear sensitive CMP slurries under normal turnovers expected in a typical fab operation. This pump can provide stable low-pulsation slurry delivery with limited large particle growth when used in optimally designed systems. Mykrolis, Processgard, Planargard and Solaris are registered trademarks of Mykrolis Corporation Planarcore is a trademark of Mykrolis Corporation 2005 Mykrolis Corporation. All rights reserved Mykrolis Logo Isopore is a trademark of Millipore Corporation Levitronix is a registered trademark of Levitronix GmbH AccuSizer is a trademark of Particle Sizing Systems LS 230 is a trademark of Beckman Coulter, Inc. Mykrolis Corporation, Rakesh K. Singh 36

37 Enabling the processes that enable the future Mykrolis Corporation, Rakesh K. Singh 37