PCS PIRANHA plasma abatement system: Update of evaluation on 300mm Etch process

Transcription

1 PCS PIRANHA plasma abatement system: Update of evaluation on 300mm Etch process Joe Guerin/ CS CLEAN SYSTEMS AG, Ismaning, Germany

2 EPA Greenhouse Gases Reporting Rule Implications for the USA Semiconductor Industry! In response to the FY2008 Consolidated Appropriations Act, the EPA issued the Mandatory Reporting of Greenhouse Gases Rule (74 FR 5620) which requires reporting of greenhouse gas (GHG) data and other relevant information from large sources and suppliers in the United States.! Electronics or MEMS facilities that emit 25,000 metric tons or more per year of GHGs are required to submit annual reports. 2

3 EPA Greenhouse Gases Reporting Rule Semiconductor Companies Affected! The 25,000 tonne CO2-e limit encompasses 52 % of US Semiconductor Manufacturing facilities or 96% of Total Emissions Source: EPA Technical Support Document for Proposed Rule for Mandatory Monitoring of Greenhouse Gases. November

4 EPA Greenhouse Gases Reporting Rule Estimating GHG Emissions! The Final Reporting Rule foresees several clearly-defined alternatives or Tiers for estimating emissions, allowing Semiconductor companies to factor in increasing levels of process information. A few examples:! IPCC Tier 1 Method: Simplistic multiplication of manufactured silicon substrate area by default emission factors! IPCC Tier 2c Method: Provides default values which can be used for gas consumption and by-product formation for five Etch and Chamber Clean categories! IPCC Tier 3 Method: Allows for use of facility-specific data on process recipes, tool platforms, etc. 4

5 EPA Greenhouse Gases Reporting Rule Default Emission Factors for PFCs by Process Type Source: EPA Technical Support Document for Proposed Rule for Mandatory Monitoring of Greenhouse Gases. November

6 EPA Greenhouse Gases Reporting Rule Two Options for Factoring DRE due to Abatement! 1. The use of the EPA developed Default Value of 60 % DRE for abatement systems! 2. The direct and proper measurement of DRE values using the official EPA protocol EPA 430-R ! Responsibility of the Semiconductor company to ensure that the abatement system is Installed, operated and maintained in accordance with the manufacturer s specifications! EPA demands ongoing Random Sampling Abatement System Testing Program (RSASTP): 20 % systems each year over 5 years 6

7 EPA Greenhouse Gases Reporting Rule Abatement Must Account for DRE and Uptime 7

8 Semiconductor Process PFC Emissions Focus on Plasma Etching! For 300mm wafer manufacturing, CS CLEAN SYSTEMS will direct its PFC Reduction product roadmap on Plasma Etching, in the expectation that more environmentally benign sources of Fluorine will be used for 300 mm Chamber Clean.! The PCS PIRANHA is NOT intended for deployment on CVD Clean applications. 8

9 Abatement of PFC Gases! High energy input is required to break down chemically-stable PFC gases. Thermal scrubbing techniques based on fuel combustion or electrical heating have therefore found widespread use for PFC abatement.! High consumption of fuel and/ or electrical power is necessary to "burn" the stable PFC gases at high temperature.! The vast majority of abatement systems currently in use are installed downstream of the process tool and vacuum pumps 9

10 Efficient Abatement of PFC Gases Typical Post-Pump Scrubbing Situation N2 Dilution ca. 40 slm PFC from Etcher 200 sccm CF4 + 1 slm Ar, O2, etc. Dry Pump Post Pump PFC Concentration: 0.5 % Flow > 40 slm To Downstream Scrubber! Starting at the exhaust pump, unused PFC gases exiting the process chamber undergo dilution by inert gas! Higher dilution usually requires higher energy input from the abatement system and leads to a fall-off in DRE efficiency for PFCs 10

11 Efficient Abatement of PFC Gases Further Dilution by Abatement System N2 Dilution ca. 40 slm Fuel PFC from Etcher 200 sccm CF4 Dry Pump Scrubber O2/air N2 + 1 slm Ar, O2, etc.! The official EPA test measurement protocol requires mass spectrometer determination of the dilution effect of gases added to the PFC stream. This is in addition to the FT-IR measurement of PFC removal. 11

12 Efficient Abatement of PFC Gases Multi Chamber Hook-Ups Etch Chamber #1 PFCs INACTIVE Etch Chamber #2 PFCs INACTIVE Etch Chamber #3 PFCs ACTIVE Pumps Downstream Scrubber! Synchronizing downstream scrubber operation with the duty cycles of a multi etch chamber hook-up poses a challenge to energy saving strategies. 12

13 Efficient Abatement of PFC Gases Upstream (Pre-Pump) Scrubbing N2 Dilution ca. 40 slm PFC from Etcher 200 sccm CF4 + 1 slm Ar, O2, etc. PFC Scrubber Dry Pump > 40 slm To scrubber! Scrubbing upstream of the pump allows the PFC output to be treated in its concentrated form prior to further dilution 13

14 Pre-Pump Plasma Decomposition of PFC Gases The Drawbacks! Benefit of dedicated scrubber for each chamber comes with higher initial capital expenditure! Must be weighed against Cost-of-Ownership benefit of reduced energy and facilities usage! Vacuum plasma abatement can not handle the relatively high slm flows used on CVD Clean applications 14

15 Pre-Pump Plasma Decomposition of PFC Gases Principle of Operation! A plasma is an electrically powered chemical reactor.! High-energy electrons created within the plasma break up the PFC molecule into ionic- and atomic fragments.! The addition of a scavenging gas such as O 2 or H 2 O vapor ensures that F and C fragments do not re-combine to form new PFC molecules.! Downstream of the plasma, the waste gas consists of reactive halogens and halides which can readily be removed by standard scrubbing techniques. 15

16 Pre-Pump Plasma Decomposition of PFC Gases Two Technologies Available! Inductive Plasma sources Operating frequency: MHz! Microwave Plasma sources Operating frequency: 2.45 GHz! In both cases the plasma is confined within a cylindrical ceramic chamber which is fitted in the foreline to the vacuum pump! PFC gases are converted into into reactive by-products and are not scrubbed! 16

17 PIRANHA PCS Microwave Plasma Conversion Unit Installation Schematic 17

18 Post-Pump Removal of Reactive Plasma by-products Different Customer Philosophies! Downstream PoU Dry Scrubbing! Downstream PoU Wet Scrubbing! No PoU Scrubbing - End-of-Pipe Wet Scrubber 18

19 PCS PIRANHA Major Components! Microwave Applicator! Power Supply! Controller & Interface Box 19

20 PCS PIRANHA Components Microwave Applicator (MWA) 2 kw Version Magnetron Plasma chamber! The PIRANHA PCS 2000 employs a 2.45 GHz magnetron to generate up to 2000 W of microwave power.! A waveguide conducts the microwaves into an adjacent ceramic chamber, mounted in the vacuum foreline. Here, the incoming waste gas stream is converted to a high-energy plasma in which PFC molecules become dissociated. 20

21 PCS PIRANHA Components Microwave Applicator (MWA)!!!!! Standard foreline vacuum connection DN63 ISO-LF Cooling Water connection double-sealing quick fittings High Voltage connection Electrical connection Phoenix socket 298 mm (W) x 258 mm (D) x 264 mm (H), ca. 20 kg 21

22 PCS PIRANHA Components Advantages of the Patented MWA Design! Cylindrical Plasma Chamber manufactured from proprietary ceramic which is fixed in an aluminium housing! Insensitivity to Process Gas Fluctuations: Coupling of microwave energy into chamber is intelligently designed to maintain plasma efficiency even during fluctuating gas loadings. 22

23 PCS PIRANHA Components Advantages of the Patented MWA Design! Leak-Tight Plasma Chamber Design The ceramic tube does not constitute the seal between the cooling water circuit and plasma chamber. Damage to ceramic tube cannot result in flooding of foreline.! Maintenance-Friendly Ceramic Tube No specialist instrumentation or re-calibration is required, and the work can be carried out on-site. This is a major logistics advantage when compared to systems which have to be returned to the manufacturer for re-tuning. 23

24 PCS PIRANHA Components High Voltage Supply (HVS)! Purpose! to provide the MWA2000 with electrical energy in a safe fashion! to serve as the master controller for the microwave power, ON-OFF timing, and safety interlocking! Power Supply 400 VAC 3-phase 24

25 PCS PIRANHA Components Control Interface Box (CIB)! The CIB is a standard accessory which adds an additional level of comfort and safety to the PCS PIRANHA system. User-friendly controls are provided to set and display microwave power and other parameters without using the CAN interface of the HVS2000.! CIB and HVS boxes are usually housed in pairs within a 19" rack cabinet 25

26 PCS PIRANHA Components Control Interface Box, Functions! Transforms signals to and from the HVS into field-ready signals, and communicates with the tool and / or central monitoring system. Allows the user to manually adjust and display microwave power.! Provides on-demand supply of O2 to PCS by control of shut-off valve and MFC.! Primary (Safety) Interlock. Ensures that PCS cannot be switched on at pressures above 10 mbar (e.g. because the tool's process chamber is open for maintenance). Pressure signal from foreline is supplied by a Pirani vacuum gauge. Prevents microwaves from exiting the applicator.! Secondary Interlock. Ensures PCS cannot be run with insufficient gas loading. Not relevant to human safety, but prevents the MWA2000 from damage due to out-of-spec operation. 26

27 PCS PIRANHA Components Control Interface Box - Failsafe Interlocks.. CIB2000 (continued)! Interface for communication with tool. For instance, ensuring that the PCS is only active during Etch recipe steps where PFC gases are in use.! Allows two distinct operating conditions (power/ O2 flow) to be stored and individually triggered. A useful energy-saving function for Etch recipes with alternating low- and high flows of PFC gases.! Enables ON-Time to be recorded: e.g. to comply with EPA requirements for the inclusion of abatement systems in GHG Reporting. 27

28 PIRANHA PCS Tool Interlocking: Energy Saving PCS only ON while PFC gases are active: typically 30 % of recipe! ON/OFF control of PIRANHA can be synchronised with PFC usage using a communication protocol from the Etch tool. As a simple alternative, P/E switches can be used to trigger volt-free inputs to the PIRANHA when PFC valves are opened (schematic above). 28

29 PCS PIRANHA Packages For single chamber etcher. Rack cabinet for 1-4 chambers! RC001! ready-to-go package with 3-phase power cord! installs easily on top of CLEANSORB scrubber! 570 x 540 x 300 mm! RC004! houses up to 4 HVS CIB combos! power distribution panel with common 3-phase supply available on request! 600 x 800 x 1600 mm 29

30 PCS PIRANHA 2000 Consumables! Process Media! Electricity! Cooling water! Oxygen or H2O vapor! Replaceable Components! Ceramic liner tube of plasma chamber! Magnetron! O-rings 30

31 PIRANHA PCS 2000 Installation Photo: 2-chamber with dry bed absorber 31

32 PIRANHA PCS 2000 Typical Foreline Installation at Customer Site 32

33 PIRANHA PCS 2000 Installation Photo: 6 x units in Pump Forelines 33

34 PIRANHA PCS 2000 Installation Photo: at Outlet of 300mm Etch Chamber 34

35 PIRANHA PCS 2000 Installation Photo: 2 x units Mounted Horizontally 35

36 PIRANHA PCS 2000 Installation Photo: Photovoltaic Etching Turbomolecular pump PCS

37 PCS PIRANHA On-Site FT-IR Measurements of Destruction removal Efficiency (DRE) for PFC Gases 37

38 On-Site Evaluation: FT-IR Analytical Set-Up Etcher Extract O 2 Plasma Pump CS dry bed absorber for reactive byproducts N 2 Ballast FT-IR Spectrometer N 2 38

39 On-Site Measurement of DRE Notes on FT-IR Analytical Setup! Small prefilter used to protect FT-IR from reactive compounds (F 2, HF, COF 2, SiF 4, etc.), PFCs, hydrocarbons and CO will pass through.! Analysis of PFC DRE and GWP reduction by monitoring the process with PIRANHA on and off. 39

40 On-Site Measurement of DRE CF4 Concentration Downstream of PCS CF4 Inlet = 4,500 ppm 200 (Peaks correspond to wafer starts) Concentration (ppm) Time (min) 40

41 On-Site Measurement of DRE Comparison of PFC Conc. with Plasma ON Vs OFF 2,0 1,8 1,6 Blue: PIRANHA off RED: PIRANHA on CO CF 4 1,4 C 2 H 2 Absorbance 1,2 1,0 0,8 C 2 H 4 0,6 0,4 0,2 C 2 H 2 0, Wavenumbers (cm -1 )

42 Trials with Customer 200mm Recipes 100 sccm CF4 100 sccm CF sccm O 2 Concentration (ppm) Q = 0 W 100 sccm O 2 Q = 1000 W 200 sccm O 2 Q = 1000 W 150 sccm O 2 Gases off Q = 1000 W Q = 0 W! 100 sccm CF 1000 W, 100 sccm O 2! DRE = 92% Time (min) 42

43 Summary of 200mm Recipe Evaluations! A plasma power of W is fully adequate for Etch recipes with low PFC flows.! At this power range and an O 2 flow of approx. 150 sccm, the following DREs were attained: Gas Flow DRE CF 4 50 sccm 97% 100 sccm 92% CHF sccm > 99% SF 6 50 sccm > 99% 43

44 First Trials of 3kW PIRANHA PCS Evaluated at Test Lab of Major Etch Tool Vendor! Tested against industry standard 300mm Etch processes and parameters! Design of Experiment included several PFC gases, pressure and flow regimes! Partner gas was H 2 O vapor! DRE was determined using mass spectroscopy and FT-IR! First unit supplied had to be changed out due to leak; Evaluation was continued with Rev. 2 system which reduced the time window available for testing 44

45 300mm Etch Trials of 3kW PIRANHA PCS Overview of DRE at Various CF4 Test Flows! As expected, the primary parameter influencing DRE was the microwave power setting.! The ratio of H2O vapor to PFC flow is also significant 45

46 300mm Etch Trials of 3kW PIRANHA PCS Stability of DRE Behaviour Vs Partner Gas Ratio! With vapor flow adjusted to the optimised setting, no significant drift in the DRE occurred over an 85 hour observation period with plasma ON at full power. Borderline PFC/ H2O vapor settings resulted in drift of DRE over time 46

47 300mm Etch Trials of 3kW PIRANHA PCS Reliability Comparison with Inductive Plasma Device! The condition of the microwave chamber compared favorably to that of an inductive plasma system under the same test conditions despite a considerably longer trial period. 47

48 300mm Etch Trials of 3kW PIRANHA PCS Condition of Ceramic Liner at Test Completion! Due to other project commitments, it was necessary to conclude the trial after a period of 91 plasma hours. Inspection of the plasma chamber showed that it was still in very good condition. 48

49 300mm Etch Trials of 3kW PIRANHA PCS Overview of DRE at Various CF4 Test Flows! Detailed test recipe parameters are proprietary: Selected data quoted here are for the gas CF4 only: Power CF4 Flow DRE 2500 W 200 sccm 90.8 % 2500 W 300 sccm 84.4 % 3000 W 200 sccm 96.5 % 3000 W 300 sccm 92.4 % 49

50 300mm Etch Trials of 3kW PIRANHA PCS Next Steps! The Etch Tool manufacturer would like to see further marathon testing of the 3000 W unit to > 1,200 Plasma ON hours corresponding to 22,000 wafer cycles! CS CLEAN SYSTEMS has already commenced testing the 3kW unit under comparable challenge conditions in its own R&D lab! Investigate the necessity of revising power upwards to provide reserve power margin at upper end of operating scale.! If necessary, various modifications to cabling and connections to facilitate on-board integration into Etch tool as an OEM item. 50

51 PCS PIRANHA Microwave Plasma for PFC Abatement Advantages! High Perfomance on Etch applications with high PFC flows! Easily retrofitted to all existing etch tool installations! High conversion efficiency prior to rough pump dilution! Easily controllable, turn on only as needed! Fast response time, excellent plasma stability! Suitable for use with dry scrubber: environment friendly! Improved fab safety with no flames or fuel usage! On-site service: No need for off-site calibration! Amenable to on-site analytical testing! Favorable cost of ownership 51