Further Evaluation of Two Plasma Technologies for PFC Emissions Reduction

Transcription

1 SSA 2000 Annual Conference, Arlington, Virginia Further Evaluation of Two Plasma Technologies for PFC Emissions Reduction Walter Worth Program Manager, ESH April 27, 2000

2 Background Perfluorocompounds (PFCs) are potent greenhouse gases In April of 1999, World Semiconductor Council (WSC) established international PFC emissions reduction goal -- 10% absolute reduction by 2010, over 1995 baseline To meet aggressive goal, fabs will need a 95% PFC utilization or destruction for PECVD chamber cleans and, selectively, some etch tools Currently, plasma technologies appear to offer the most cost-effective way of achieving this goal p:\955\a-pfc_us\ssa200.ppt 2

3 Growth of Emissions with No Action (linear extrapolation of data for U.S.EPA MOU Partners) 3.0 Emissions (MMTCE) % Goal '95 '96 '97 '98 '99 '00 '01 '02 '03' 04' 05' '06 '07 '08 '09 '00 Year p:\955\a-pfc_us\ssa200.ppt 3

4 PFC Emissions Reduction Options Alternative Chemicals Destruction/ Decomposition Global Warming Gas Reduction Process Optimization Recovery & Recycle Combustion Plasma Thermal/ Chemical p:\955\a-pfc_us\ssa200.ppt 4

5 Introduction At the SSA 99 Conference, we reported the results from preliminary evaluations of: AMAT s µclean microwave plasma technology for PECVD chamber cleaning Litmas Rf plasma abatement device for etch tool emissions Both were first-time evaluations of these technologies in a manufacturing environment The results were very encouraging, but the tests were short and long-term reliability was still a question The results presented today are from evaluations of commercial, improved versions of these two devices p:\955\a-pfc_us\ssa200.ppt 5

6 Different Technology Options NF 3 /Ar Remote Plasma To House Scrubber Alternative Chemistries (e.g., dilute NF 3 ) Turbo Pump Pre-Pump Abatement CVD/Etch TOOL Dry Pump Post-Pump Abatement p:\955\a-pfc_us\ssa200.ppt 6

7 Evaluation of Applied Materials Remote Clean Technology for DxZ Chambers

8 Applied Materials Remote Clean Technology Utilizes low-field toroidal plasma to generate atomic F upstream of CVD chamber Input gases: NF 3 and Argon (1:2 ratio) Compact, lid-mountable unit No additional rack components Has foreline clean endpoint detector Optical emission spectrometer monitoring SiF 4 p:\955\a-pfc_us\ssa200.ppt 8

9 Remote Clean Unit on DxZ Lid p:\955\a-pfc_us\ssa200.ppt 9

10 Demonstration Goals Conduct two 1000 wafer marathons with depositions in DxZ TM chamber PETEOS and doped PETEOS films Measure film parameters and particles Utilize endpoint detector to determine clean time Conduct Design of Experiments (DOE) Optimize clean time, NF 3 and Ar flows Characterize emissions Verify > 99% NF 3 utilization Quantify F 2 emissions p:\955\a-pfc_us\ssa200.ppt 10

11 Summary of Marathon Results Both 1000 marathons completed successfully NF 3 = 700 sccm, Ar = 1400 sccm Clean time for 1 µm PETEOS film = 55 seconds did not vary throughout marathons All film parameters within specification limits No particle issues p:\955\a-pfc_us\ssa200.ppt 11

12 10KÅ Film Thickness/Uniformity PETEOS 10, Thickness (A) 10,100 10,000 9, Non-Uniformity (%) 9, Wafer # Thickness (A) % Non-uniformity p:\955\a-pfc_us\ssa200.ppt 12

13 Particles - PETEOS Particle Adders Wafer # P articles p:\955\a-pfc_us\ssa200.ppt 13

14 Film Stress/Refractive Index PETEOS Stress R efrac tive Index Film stress Refractive Index Wafer # Stress - 4K Stress - 8K wafer # R efrac tive Index p:\955\a-pfc_us\ssa200.ppt 14

15 DOE Results for 1µm Oxide Film NF 3 NF 3 Clean Used Flow Rate Time (scc) (sccm) (sec.) Min. NF 3 Usage Baseline Clean * 55 Min. Clean Time *used 700 sccm and 55 sec. for marathon p:\955\a-pfc_us\ssa200.ppt 15

16 Baseline Conditions for Remote Clean Process NF 3 Consumption = 610 scc/wafer Time (sec) NF (sccm) Argon (sccm) Pressure (Torr) 3 p:\955\a-pfc_us\ssa200.ppt 16

17 Sampling Apparatus To Acid Exhaust FTIR PI SAMPLE PUMP CALIBRATION SYSTEM 750 torr PI SAMPLE PUMP TO CORROSIVE EXHAUST N2 PURGE PROCESS PUMP MASS SPECTROMETER Tool Exhaust GASES p:\955\a-pfc_us\ssa200.ppt 17

18 Emissions from Standard TEOS Process (per wafer pass) Film 2.5K Å 6.5K Å 10K Å NF 3 IN (scc) NF 3 (scc) SiF 4 (scc) F 2 (scc) HF (scc) Utilization (% ) F-B alance p:\955\a-pfc_us\ssa200.ppt 18

19 Comparison of PFC Emissions Global Warming Potential lbs (C eq)/wp In situ C 2 F 6 RF Clean Remote Plasma NF 3 Clean p:\955\a-pfc_us\ssa200.ppt 19

20 Comparison of HAP Emissions Hazardous Air Pollutants lbs (HF eq)/wp In situ C 2 F 6 RF Clean Remote Plasma NF 3 Clean p:\955\a-pfc_us\ssa200.ppt 20

21 Simplified Cost of Ownership Throughput (continuous) 55 wafers/hour Availability 90% Utilization 70% Gross throughput 291,060 wafers/year Retrofit capital costs $47,290/year Unit retrofit capital $0.16 Installation cost $0.00 Clean gas cost $0.52 Consumables cost $0.15 Total $0.83/wafer Assumptions: TEOS oxide film deposition = 1µm A chamber clean after every wafer 4-chamber Centura PECVD tool Retrofit capital cost/chamber = $59,900 Installation labor cost/chamber = $3,360 Capital & labor amortized over 5 years NF 3 and argon are available at tool Cost of NF 3 = $110/lb Maintenance kit = $11,000/yr/chamber p:\955\a-pfc_us\ssa200.ppt 21

22 Summary Remote Clean is viable alternative to in-situ C 2 F 6 clean Virtually eliminates PFC emissions No negative effects on deposition process Only negatives are: Cost of NF 3 is high Tool retrofit cost is significant By-product is large amounts of F 2 p:\955\a-pfc_us\ssa200.ppt 22

23 Reliability Study of Litmas Plasma Abatement Device

24 Test Program DRE/By-Product Evaluation DOE and 1050 wafer marathon on dielectric etch tool Blanket I-line photoresist wafers High flow tests for CF 4, NF 3, SF 6 and C 4 F 8 Analysis by extractive FTIR (10 cm) and QMS Long-Term Operation Evaluation Exposure of pump internals to HF and H 2 O Effect of repeated cycling on device (e.g., plasma tube) Service requirements Process Impact Evaluation Foreline pressure increase Process drift, particle generation Evidence of back-streaming p:\955\a-pfc_us\ssa200.ppt 24

25 Litmas Plasma Abatement Device Specifications: 1200 watts of RF power (1800 W supply) MHz variable frequency Solid-state match (no moving parts) ms typical plasma strike time 1.92 i.d. x 9 Al 2 O 3 tube 4 lpm cooling water 16 status and power LED s plasma turned on & off by tool variable shutoff delay p:\955\a-pfc_us\ssa200.ppt 25

26 Turbomolecular Pump Auxiliary Gas Isolation Valve Metering Valve Medium Density Oxide Etcher Tool Effluent O 2 In Isolation Valve To Scrubbed Exhaust Schematic of the Device Installation Water Infusion System Cooling Water Ports Power Supply and Matching Circuitry To FTIR mtorr Signal From Tool Final Valve N 2 Purge Gate Valve Dry Pump p:\955\a-pfc_us\ssa200.ppt 26 MF MFC C N 2 Purge 45 slm

27 Results from the DOE CF 4 CHF 3 Argon CF 4 Emission Matrix Flow Flow Flow DRE Reduction Point (sccm) (sccm) (sccm) (%) (% Kg CE) center p:\955\a-pfc_us\ssa200.ppt 27

28 FTIR Spectra for Centerpoint Etch Recipe Abatement OFF 5 sccm CF 4 50 sccm CHF 3 60 sccm Ar 166 mtorr pressure Absorbance HF 134 ppm CF 4 CHF HF Abatement ON 1200 W power 150 sccm H 2 O 300 mtorr pressure Absorbance CO 2CO H 2 O 4 ppm CF 4 0 p:\955\a-pfc_us\ssa200.ppt Wavenumber (cm -1 )

29 Effect of Rf Power on CF 4 DRE CF 4 DRE vs. Applied Abatement Power CF 4 DRE (%) Pow er (Watts) 5ccm CF 4 50 sccm CHF 3 60 sccm Ar 75 Watt increments 1200W p:\955\a-pfc_us\ssa200.ppt 29

30 Effect of Water Concentration on CF 4 DRE CF4 DRE (%) CF 4 DRE (%) W a te r Conce ntra tion (ppm ) Optimum Water Concentration ~3300 ppm p:\955\a-pfc_us\ssa200.ppt 30

31 Destruction of CF 4 at High Flows* Foreline CF 4 Flow Ar Flow CF 4 DRE P re ssure sccm sccm % m Torr * with 150 sccm of H 2 O injection p:\955\a-pfc_us\ssa200.ppt 31

32 Destruction of Other Gases at High Flows Foreline Gas Flow Ar Flow DRE Pressure Gas sccm sccm % mtorr a NF b SF c C 4 F > a with 100 sccm O 2 addition b with 150 sccm O 2 addition c with 130 sccm of H 2 O addition p:\955\a-pfc_us\ssa200.ppt 32

33 C 4 F 8 /CF 4 By-products Input: 8 sccm C 4 F 8, 12 sccm CF 4, 140 sccm H 2 O Abatement OFF Abatement ON Absorbance ppm C 4 F 8 49 C 3 F 8 17 C 2 F 6 40 CF CO 770 SiF 4 10 HF CO CF 4 C 4 F 8 Absorbance HF ppm ppm CF H 2 O 529 CO 1702 HF 2408 CO 2 97 SiF 4 12 COF 2 13 CO 2 CO CF Wavenumber (cm -1 ) Wavenumber (cm -1 ) p:\955\a-pfc_us\ssa200.ppt 33

34 SF 6 By-Products (no etching in tool, abatement ON, H 2 O addition) 12.5 sccm SF sccm H 2 O 50 sccm SF sccm H 2 O Absorbance HF H 2 O ppm SF 6 0 SO HF 1426 H 2 O 1386 H 2 O Absorbance HF ppm SF 6 50 SO HF 2401 H 2 O 177 SO 2 F 2 SO 2 SF 6 SOF Wavenumber (cm -1 ) Wavenumber (cm -1 ) p:\955\a-pfc_us\ssa200.ppt 34

35 High Resolution OES Spectrum of CF 4 /Ar Plasma During H 2 0 Backstreaming Tests High Resolution Charge-Coupled Device (CCD) OES Spectrum No peaks detected for H and OH (H at 286.1,656.2 nm; OH at 282.9, 308, nm) Signal Counts Wavelength (nm) p:\955\a-pfc_us\ssa200.ppt 35

36 Pump Inspection Results Etch tool processed 11,500 wafers over 8 months Plasma in Litmas device was on for 357 hours Pump was disassembled and visually inspected at end of test. Found: no visible corrosion in inlet no particles or films in foreline no pump inlet o-ring degradation no particles or films in silencer no visible contamination of bearing grease p:\955\a-pfc_us\ssa200.ppt 36

37 Close-up of Dry Pump Claw Indicating No Teflon Degradation p:\955\a-pfc_us\ssa200.ppt 37

38 Close-up of Lobes & Stator Surfaces Showing No Abraison or Film Buildup p:\955\a-pfc_us\ssa200.ppt 38

39 Summary 8-month performance of device was excellent: Totally integrated with etch tool; plasma on when gases flow Required no service over the whole period Refilling of water reservoir was only requirement Increased foreline pressure and H 2 O addition had no effect on etch tool performance: No increase in particles No backstreaming was observed Emission reduction for CF 4 /CHF 3 /Ar etch recipe was ~ %; for CF 4 /C 4 F 8 /Ar ~ At CF 4 flows > 50 sccm, DRE drops off significantly There was no visible impact on pump hardware p:\955\a-pfc_us\ssa200.ppt 39

40 Acknowledgements The following persons participated in the evaluations and the preparation of the reports. Their extraordinary efforts are greatly appreciated: Applied Materials Remote Plasma Device Laura Mendicino, Paul Thomas Brown & Stan Filipiak (Motorola) Alan Atherton, Martin Seamons, BipinThakur, Heath DeShong, Toni Vaughan, Thomas Nowak & D.Silvetti (Applied Materials) Andrew Johnson & Richard Pierce (Air Products) Litmas Abatement Device Victor Vartanian, Laurie Beu, T.Stephens, J.Rivers & B. Perez (Motorola) Eric Tonis, Mark Kiehlbauch & David Graves (U of CA at Berkley) p:\955\a-pfc_us\ssa200.ppt 40