Susceptibility of Different Slurry Types to Agglomeration

Transcription

1 Susceptibility of Different Slurry Types to Agglomeration Mark Litchy 1, Don Grant 1, and Reto Schoeb 2 1 CT Associates, Inc. 2 Levitronix GmbH Levitronix CMP Users Conference 29 February 1, 29 Slide 1

2 Introduction A variety of types of delivery systems are used to pressurize and circulate CMP slurry to deliver it to the process tools. Typically, the slurry passes through the equipment providing the motive force approximately 1 times before it is used to polish wafers. Some CMP slurries are susceptible to agglomeration caused by mechanical handling. limits the life of filters reduces yield by causing wafer defects Slide 2

3 Experiment performed CMP slurry was circulated in a simulated distribution loop using 3 different types of pumps to determine the effect of circulation on slurry health. A variety of slurry health parameters were monitored including: Working particle size distribution (PSD) Dynamic light scattering (Particle Sizing Systems NICOMP 38ZLS) UFA/SMPS (UltraFine Atomization/Scanning Mobility Particle Sizer) Large particle tail of the slurry PSD (.56 μm) Particle Sizing Systems AccuSizer 78 Zeta Potential Total % solids ph Specific gravity Hydrogen peroxide concentration (when applicable) Slide 3

4 Experiment details Test system volume: 12 L of slurry Pump air supply or speed was adjusted to achieve the following test conditions: Flow rate: 3 Lpm Pump outlet pressure: 3 psig Tank blanketed with humidified N 2 : RH > 9% Slurry temperature: 21 ± 2 C Pulse dampener included when applicable Nitrogen humidifier chiller flowmeter P pulse dampener T T sample port drain Slide 4

5 9 CMP Slurries Evaluated Slurry Abrasive: Silica (S1-S5) Fumed silica slurry (1) Colloidal silica oxide slurry (4) Alumina oxide slurry (A1-A2) Ceria slurry (C1-C2) Slurry Application: ILD (S1) Barrier (S2-S3) W (S4-S5) Copper (A1-A2) STI (C1-C2) Slide 5

6 Pumps Evaluated Diaphragm pump with pulse dampener Bellows pump with pulse dampener Levitronix magnetically levitated centrifugal pumps BPS-1 BPS-3 BPS-4 BPS-2 BPS-6 Slide 6

7 Pump Comparison Working PSD Large particle tail Other parameters No significant change during any of the tests Slide 7

8 Working particle size distributions (PSDs) Dynamic Light Scattering (DLS) measurements Relative Volume-Weighted Differential Concentration (%) S1 S2 S3 S4 S5 A1 A2 C1 C2 Volume-weighted Diameter (nm) Mean Size 99th Percentile Size S1 S2 S3 S4 S5 A1 A2 C1 C2 Slurry Type Slide 8

9 Silica slurry: Example of UFA/SMPS measurement UFA/SMPS technique Aerosolize the particles and measure the size using a DMA Measures both size and number concentrations Does not assume a shape of the distribution Grant DC (28). A New Method for Determining the Size Distribution of the Working Particles in CMP Slurries, 28 Levitronix CMP Users Conference Slide 9

10 S1 slurry: Working PSD measurements (DLS) 3 Volume-Weighted Diameter (nm) Mean: Bellows Mean: Diaphragm Mean: BPS-4 99th Percentile: Bellows 99th Percentile: Diaphragm 99th Percentile: BPS-4 As-received slurry plotted at 1.1 turnovers Slide 1

11 A1 slurry: Working PSD measurements (DLS) BPS-4 Diaphragm 1 1 Volume-Weighted Diameter (nm) Error bars represent ± 3σ Volume-Weighted Diameter (nm) Mean 99th Percentile Size 1 Error bars represent ± 3σ Bellows Volume-Weighted Diameter (nm) Error bars represent ± 3σ Slide 11

12 Summary of changes in working PSD Changes in Mean PSD after 1 turnovers Application Abrasive Type Centrifugal Diaphragm Bellows ILD fumed silica S1 barrier colloidal silica S2 barrier colloidal silica S3 W colloidal silica S4 W colloidal silica S5 copper alumina A copper alumina A2 STI ceria C1 STI ceria C2 Symbol - + Relative Change in Mean Size > 1% decrease < 1% change > 1% increase Slide 12

13 Large Particle Tail PSDs in As-Received Slurry S1 1 1 S2 S3 1 9 S4 S5 A1 1 8 A2 C1 1 7 C Slide 13

14 S1 slurry: BPS-2/BPS-6 Pumps 1 6 BPS BPS Slide 14

15 S1 slurry: BPS-4, bellows, and diaphragm pumps BPS Bellows Diaphragm Slide 15

16 S2 slurry BPS-4 Bellows Diaphragm Slide 16

17 1 6 BPS-4 S3 slurry 1 6 Bellows pump Diaphragm pump Slide 17

18 S4 slurry 1 6 BPS Bellows pump Diaphragm pump Slide 18

19 1 6 BPS-4 S5 slurry 1 6 Bellows pump Diaphragm pump Slide 19

20 BPS A1 slurry Bellows pump Diaphragm pump Slide 2

21 BPS A2 slurry Bellows pump Diaphragm pump Slide 21

22 BPS-4 C1 slurry Bellows pump Diaphragm pump Slide 22

23 1 11 BPS-4 C2 slurry 1 11 Bellows pump Diaphragm pump Slide 23

24 Concentration increases measured after 1 turnovers S1 S S3 BPS-4 Bellows Diaphragm Slide 24.1 S

25 Concentration increases measured after 1 turnovers (cont d) 1. S BPS-4 Bellows Diaphragm.1 A1 A Slide 25

26 Concentration increases measured after 1 turnovers (cont d) C1 C BPS-4 Bellows Diaphragm BPS-4 Bellows Diaphragm.1.1 Slide 26

27 Concentration increases measured after 1, turnovers S1 S S3 BPS-4 Bellows Diaphragm Slide 27.1 S

28 Concentration increases measured after 1, turnovers (cont d) 1. S BPS-4 Bellows Diaphragm.1 A1 A Slide 28

29 Concentration increases measured after 1, turnovers (cont d) C1 C BPS-4 Bellows Diaphragm BPS-4 Bellows Diaphragm.1.1 Slide 29

30 Summary of changes in large particle concentrations Submicron particles ( µm) after 1 turnovers Supermicron particles (> 2. µm) after 1 turnovers Application Abrasive Type Centrifugal Diaphragm Bellows Centrifugal Diaphragm Bellows ILD fumed silica S barrier colloidal silica S barrier colloidal silica S W colloidal silica S W colloidal silica S copper alumina A copper alumina A STI ceria C STI ceria C2 NA NA NA Symbol Concentration change Concentration ratio after 1, turnovers - Decrease <.5 None Increase Large Increase > 1 Slide 3

31 Summary Most silica slurries are sensitive to handling-induced particle agglomeration, but to varying degrees. Some ceria and alumina slurries were also sensitive to handling, while others did not appear to be. No significant changes were observed in all slurry properties during all pump tests with only 1 slurry. Slide 31

32 Summary of effect of pumps on slurry properties Pump Type Working PSD PSD Large Particle Tail Other Slurry Parameters BPS-4 pump Significant decrease in 1 slurry (A1) Significant increase in 1 of 9 slurries Minimal effect Diaphragm and Bellows pumps Significant decrease in 1 slurry (A1) Significant increase in 7 of 9 slurries Large increase in 4 of 5 silica slurries Large increase in at least 1 slurry of each type silica, alumina, and ceria slurry Large increase with at least 1 slurry in each application area Minimal effect Slide 32