Benefits and Limitations of Slurry Particle Analysis and the Need for Next Generation Capabilities. Budge Johl

Size: px

Start display at page:

Download "Benefits and Limitations of Slurry Particle Analysis and the Need for Next Generation Capabilities. Budge Johl"

Janis Douglas
5 years ago
Views:

1 Benefits and Limitations of Slurry Particle Analysis and the Need for Next Generation Capabilities Budge Johl th Annual Levitronix CMPUG Symposium

Particle size analysis can also play an integral part in evaluation of various parts and slurry distribution

2 Particle Analyzers Particle size analysis can play a major role in slurry troubleshooting, filtration and manufacturing optimization and wafer defect reduction. Particle size analysis can also play an integral part in evaluation of various parts and slurry distribution components. Pumps, valves, distribution systems and slurry piping designs are only a couple of examples of where particle analyzers can be beneficial in the evaluation of various components of fab systems.

3 Mean Particle Analysis Dynamic Light Scattering (DLS) also known as Photon Correlation Spectroscopy (PCS) 117µ (Animation Courtesy of Agilent Technologies, Particle Sizing Systems Division)

4 Large Particle Analysis has shown to be more beneficial in slurry troubleshooting and evaluations than analyzers that only give mean results Common Large Particle Tool Detector Large Particle Counters (Animation Courtesy of Agilent Technologies, Particle Sizing Systems Division)

5 Slurry Trouble Shooting Methods Large Particle Analysis One of the Most Important Analyses Typical Problem Encountered Associated Cause of Problem Troubleshooting Method Wafer Defects (i.e. scratching) Large Particles in Slurry Particle Counting Tools SEM Analysis EDX (Elemental Signature) Change in Polishing Performance Change in Mean Particle Size Distribution or other parameter Mean Particle Analyzer % Solids Measurement Density ph Conductivity % Assay Viscosity Zeta Potential Short or Reduced Filter Lifetime Gel Content of Slurry Delta p measurement SEM analysis of used filter ESEM analysis of slurry Large Particle Counters 30N50

6 Typical CMP Issues Typical field CMP Issues Encountered: High defects/scratches on wafer Change in polishing performance (RR, WIWNU) Shorter filter lifetime or reduction in lifetime Associated causes: Poor slurry handling methods (i.e. lack of humidified nitrogen blankets), which may lead to increased LPC s and gels Lack of slurry distribution PM s Filtration not optimized Slurry particle size analysis plays an instrumental role in troubleshooting these issues

7 Terminology of Particles Observed with SEM, ESEM & Light Microscope Particle: single solid sphere or other geometry Aggregate: multiple particles chemically attached to each other (chain) Agglomerate : particles and aggregates come together into closepacked clumps Micro gels: aggregates link together and form three dimensional network with water trapped within (Filter Plugging Problems) Particles Aggregate Agglomerate Microgel Ref.: R. Iler, Chapter One, The Chemistry of Silica, John Wiley & Sons, 1979

8 Oxide Defects: Large Particles in Slurry May Create Micro- Scratches & Embedded Particles on Wafer Typical defects in oxide CMP Ref.:C. Dennison, KLA-Tencor, Micro, February 1998

9 Possible Sources of Large Particle Issues Agglomerations

slurry was diluted with ph adjusted water,

10 Gels: Another Source of Large Particle Issues Membrane with Wet Gel & Particles Same Membrane with Dry Gel & Particles Wet Gels Dry Gels Large Particles Silica slurry was diluted with ph adjusted water, then filtered through a 3 micron Isopore membrane.

11 Large Particles & Cu-CMP Defects Optical image (Compass) SEM image (SEMVision) Large Chatter Marks Gouge Micro Scratch

12 Large Particles & Cu-CMP Defects Large Scratch

13 Possible Sources of Large Particle Issues Slurry shear (i.e. certain valves, pumps, piping design) Lack of humidification (wet N 2 blankets) Temperature issues during shipping or storage Settling Improper mixing of incoming slurry containers (pails, drums, totes) Large # of unnecessary turnovers ph shock during dilution Poor cleanliness of various system components (i.e. dip tubes, bung lids, filter housings systems, etc.) Agglomerations

14 Possible Sources of Large Particle Issues Lack of humidified nitrogen blankets Control + Humidified N 2 - Humidified N 2 Field Example: Fab unaware that system was off.

15 Settling Improper mixing Possible Sources of Large Particle Issues

16 Possible Sources of Large Particle Issues Foreign particles (e.g. drum stirrers not properly adjusted can scrape the side of the drums and introduce large plastic particles)

Example: Drum was left open to atmosphere A lot of dry

17 Possible Sources of Large Particle Issues Local drying in shipping container, tank, and fittings Field Example: Drum was left open to atmosphere A lot of dry slurry particles all over the top of the drum and the manual pump.

18 Possible Sources of Large Particle Issues Local drying of tote dip tube and lack of PM s. Source of particle introduction

19 Filter Housing Cleanliness Another source of large particles that may be introduced during filter change out

20 Large Particle Counters Play Integral Part in Pump and New Technology Evaluations

published back in July 1998 1, 2 Vacuum-Pressure

21 Large Particle Size Plays Role in Pump Selection Technology has come a long way since the below graph published back in July , 2 Vacuum-Pressure Technology Diaphragm Pump Technology Bellows Pump Technology

22 Correlating LPC s to Defectivity and RR Large Particle Counters Play a Critical Role in Evaluating Alternative Technologies Cumulative Counts > Diameter Large Particle Size Response of Oxide Slurry (MagLev Pump) T0hrs T336hrs (1700 TO) Particle Diameter (microns) Normalized Values Defectivity and RR Response Oxide Slurry STANDARD (Time 0) MagLev (Time 336 Hour) = 1,700 Turnovers Defect Counts RR Wafer Results

23 LPC s Key for Valve Technology Evaluations OLD TECHNOLOGY Tongue & Groove caused areas for Slurry to cake-up and cause premature failure and leak-by NEW! TECHNOLOGY Enhanced Flow Characteristics No Areas for Entrapment or Agglomeration Slide Courtesy of Parker Hannifin Corp.

Large Particle Analysis Plays Critical Role in Filter Ratings Filter Ratings Beta Ratio β = Nu / Nd where Nu is the number of particles / ml from the unfiltered upstream Nd is the number of particles

24 Large Particle Analysis Plays Critical Role in Filter Ratings Filter Ratings Beta Ratio β = Nu / Nd where Nu is the number of particles / ml from the unfiltered upstream Nd is the number of particles / ml from the filtered downstream LRV (Log Reduction Value) LRV = Log ([Feed] / [Filtrate] in particles/ml Percent Retention or Retention Efficiency % Retention = (1 (Filtrate/Feed)*100 or if know beta ratio is same as (1 1/β)*100 Efficiency can be derived from a known Beta ratio Ex = (βx 1) / βx * 100 where Ex is the efficiency for a given particle size Note: All these methods rely on large particle analysis

25 Large Particle Analysis is Critical for Creating Retention Curves Filter Retention Curves Play an Integral Role in Filter Selection 100 CMP1 Retention Efficiency Curves for Planargard CMP Filters 80 CMP3 Percent Retention CMP5 CMP7 CMP9 CM11 CM13 CM Particle Size (microns) 100% 90% PureFlo CMP Capsule Filter Retention 1 um 3 um 5 um 10 um Retention 80% 70% 60% 50% (Retention Curves Courtesy of Entegris and ZenPure) 40% Particle Size (um)

26 Large Particle Role in Filter Optimization Blue Unfiltered Sample Red Single Pass Global Loop Filtered Black Multiple Pass Global Loop Filtered

27 Defectivity Improvement Normalized Defect Data Respect to Day 0 ( >0.1 μm) Dynamic 3 µms Global Loop Filtered Unfiltered (Static) Point-of-Use 1.5 µms Filtered (Static) Time (Hours) Defectivity Correlates with Large Particle Analysis Note: However, this is not always the case. It is possible to have large soft particles that do not increase wafer defects.

28 Limitations and Future Needs

29 Some Limitations There are many particle counters available on the market today (i.e. disc centrifuge, light scattering, light extinction, acoustic spectroscopy and CHDF technologies) Some counters are not as user-friendly and there is a lot of art involved in getting good repeatable data. Data can vary greatly from operator to operator. Critical to have good training programs covering techniques and SOP s. Many tools lack good SOP s and therefore on many occasions need to be developed in house. Some tools are prone to cavitation and degassing liquids more than others. This can skew results and decrease repeatability. Challenge when comparing data from tool to tool. However, with that said, Large Particle Analysis is still one of the best analytical methods of choice: To aid in slurry trouble-shooting Slurry filter optimization and recommendations Equipment and component evaluations

30 Future Needs Analyzers that can detect large particles at lower micron ranges. Sub 0.1µ detection capability is needed for future nodes of chip technology with high resolution capability. Better tool-to-tool repeatability is needed. One area of limitation: particle hardness. (Large soft particles that do not impact wafer defectivity) Soft vs. hard particles is one area missed by large particle counters. Therefore, can t assume a larger particle tail will automatically give poor wafer results. Furthermore, cannot assume the slurry is bad because the LPC s were higher on one tool compared to another. Optimized liquid stream handling for improved results and efficiency. A method to determine particle hardness in a liquid stream would be of great benefit to the industry if one can be developed.

31 References [1] J. Bare, B. Johl, T. Lemke, Comparison of Vacuum-Pressure vs. Pump Dispense Engines for CMP Slurry Distribution, Semi Workshop, July 1998 and Semiconductor International, January [2] J. Bare, B. Johl, T. Lemke, CMP Slurry Distribution: Vacuum-Pressure vs. Pump Dispense NCCAVS, October, [3] B. Johl, M. Litchy, R. Schoeb, Effect of a Maglev Centrifugal Pump on Slurry Health and Defect Rates PacRim Int. Conference, Korea, [4] B. Johl, R. Singh, Optimum Process Performance Through Better CMP Slurry Management, Solid State Technology, August [5] B. Johl, et al., Dynamic Pot-Life and Handling Evaluation of EPL2362 First Step Copper Slurry, Proc. 8th Int. CMP Conference, Marina Del Ray, CA, February [6] B. Johl, T. Buley, Dynamic Pot-Life and Handling Evaluation of Rodel CUS1351 Copper Barrier Slurry, Proc. 7th Int. CMP Conference, San Jose, [7] B. Johl, et al., Accelerated Aging and Handling Evaluation of Rodel CUS1201 Second Step Slurry in BOC Edwards Bulk Delivery System, Proc. VMIC Conference, [8] R. Singh, B. Johl, Characterization of a Silica Based STI CMP Slurry in a Vacuum-Pressure Dispense Slurry Delivery System and Pump Loop, Proc. VMIC Conference, [9] J.P. Bare, B. Johl, Accelerated Aging and Handling Evaluation of Rodel ILD1300 Oxide CMP Slurry, Proc. AVS N. Calif. CMPUG Annual Symposium, [10] J.P. Bare, B. Johl, Comparison of Humidified vs. Non-humidified Vacuum Pressure CMPS Slurry Distribution System, Proc. VMIC Conference, [11] B. Johl, Slurry Handling, Troubleshooting and Filtration, Levitronix CMP Users Conference, Santa Clara, CA, February [12] B. Johl, H. Porter, Investigation of Valve Effects on Wafer Defectivity using an Oxide Slurry, Levitronix CMP Users Conference, Santa Clara, CA, February 2006.

Challenges of Large Particle Size Analysis in CMP Slurries, and Opportunities for Improved Reliability

Challenges of Large Particle Size Analysis in CMP Slurries, and Opportunities for Improved Reliability Budge Johl 29 th European CMP Users Symposium Spring 2013, Zurich, Switzerland Outline Background