Advances in Radio Frequency q yPlasma Power Delivery Systems
D. Carter & D. M. ShawAdvanced Energy gyIndustries, Inc.
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai1
Outline
• Introduction• RF Power Delivery Systems: Overview• Impedance Matching Techniques
– Fixed f, Pdel Regulation w/Fixed Match– Fixed f, Pdel Regulation w/Variable Match– Variable f, Pdel Regulation w/Variable Match
Variable Frequency Process Example• Variable Frequency Process Example• RF Power Pulsing
S / C l i
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai2
• Summary / Conclusion
RF Power Delivery System: OverviewDelivered
RF Match
Forward Power
Power
RFGenerator
Match Network
Plasma Chamber
Reflected
Coaxial Cable
Impedance ChamberPower Impedance(VSWR)• Purpose
– Enable reliable and consistent plasma ignition– Accurately deliver RF power to changing plasma conditionsAccurately deliver RF power to changing plasma conditions
• Components– RF generator – Coaxial cable
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai3
– Matching network– Plasma chamber
Impedance Matching Techniques
• Fixed f, Pdel Regulation w/Fixed Match• Fixed f, Pdel Regulation w/Variable Match• Variable f, Pdel Regulation w/Variable Match, del g
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai4
Fixed f, Pdel Regulation, Fixed Match
•Tune match for “central” impedance point T l h l diff t•Tool may have several different
“central” impedance points depending on range of recipes
Delivered
Fixedmatch
RFGenerator
Match Network
Forward Power
Coaxial Cable
Delivered Power
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai5
Plasma Chamber
Reflected Power
Impedance(VSWR)
Fixedfrequency
Fixed f, Pdel Regulation, Fixed Match
•Very fast—relies on generator’s fast electronics rather than slow mechanical matchmechanical match•No moving parts (no variable capacitors)—minimizes component wear-outp•Generator’s ability to handle reflected power is critical—typically requires “oversized”
tgenerator•Limited range depending on magnitude of impedance change for each process
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai6
for each process
Impedance Matching Techniques
• Fixed f, Pdel Regulation w/Fixed Match• Fixed f, Pdel Regulation w/Variable Match• Variable f, Pdel Regulation w/Variable Match, del g
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai7
Fixed f, Pdel Regulation, Variable Match
•Variable match gives very wide process range •No need to define known impedance points—variable match automatically tunes•Preset match points can minimize time to achieve 50 Ωminimize time to achieve 50 ΩtuneVariablematch
RFG t
Match N t k
Forward Power
C i l C bl
Delivered Power
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai8
Generator Network
Plasma Chamber
Reflected Power
Coaxial Cable
Impedance(VSWR)
Fixedfrequency
Fixed f, Pdel Regulation, Variable Match
•Very fast—relies on generator’s fast electronics rather than slow mechanical matchmechanical match•Autotuning match allows very wide process range•Variable capacitors subject toVariable capacitors subject to wear-out in highly cyclical processes•Generator’s ability to handle yreflected power is critical—typically requires “oversized” generator
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai9
Impedance Matching Techniques
• Fixed f, Pdel Regulation w/Fixed Match• Fixed f, Pdel Regulation w/Variable Match• Variable f, Pdel Regulation w/Fixed Match, del g
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai10
Variable f, Pdel Regulation, Fixed Match
•Generator varies frequency to obtain best match—combined with delivered power regulation allows wide operatingallows wide operating •Often, fixed match may be used to cover all required process rangesranges•Variable match may be added for added range if necessaryFixed
match
RFG t
Match N t k
Forward Power
C i l C bl
Delivered Power
match
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai11
Generator Network
Plasma Chamber
Reflected Power
Coaxial Cable
Impedance(VSWR)
Variablefrequency
Variable f, Pdel Regulation, Fixed Match
•Requires frequency agile generator (ability to frequency tune)tune)•VERY fast—tunes typically in 10’s of msec•Minimizes need for “oversized”Minimizes need for oversized generator (reduced reflected power)•Allows development of process p precipes requiring extremely precise power delivery
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai12
Variable f, Pdel Regulation, Fixed Match
•Example of frequency tuning into a plasma power change M t h t k i fi d•Match network is fixed
•Tune with minimum reflected power achieved in less than 150 µsecµsec
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai13
Plasma Ignition Using Three Different g gTechniques
Variable match Variable matchw/presets
Frequency tunew/fixed match
•Tuned in ~2.3 secw/presets•Tuned in ~1.1 sec
w/fixed match•Tuned in ~ 10 ms
•Faster tune results in more repeatable processes especially for
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai14
•Faster tune results in more repeatable processes, especially for short steps
Process Example
P l d fl l t ti d l t iti•Pulsed flow, electronegative and electropositive gases •Could represent deep silicon etch process or complex gate stack etch recipe
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai15
Process Example: Fixed Frequency
•Traditional variable match network•Fixed frequency generator•Match continuously moves—l diti hplasma condition never reaches
stable operating point
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai16
Variable Frequency Process Example
•Fixed match network•Variable frequency, auto-tuning generator•Match never moves—plasma l i d i dalways receives desired power
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai17
SummaryO ti Ad t Di d tOption Advantage Disadvantage
Load Power Fast, accurate delivery to into 50 and non-50 Ω loads
Limited range depending on required power or
Regulation changes in plasma impedance
Variable Match withWidest impedance matching range available Adjustable
Slow mechanical components in matchVariable Match with
autotunerange available. Adjustable pre-sets for minimizing time to achieve match.
components in match. Subject to wear in highly cyclical processes.
Fast broader impedance Operating range smallerFrequency tuning
Fast, broader impedance range for load regulation
Operating range smaller than variable match
Load power regulation
Broadest operating range, fastest performance
None
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai18
regulation, frequency tuning & variable match
fastest performance available
Conclusions
• Modern RF delivery systems offer several different methodsCh i d d ifi i t• Choice depends on specific process requirements– Step times– Impedance rangeImpedance range– Power delivery accuracy requirements
• Some systems are available that are fast enough to tune even during pulsed RF power delivery
2008-3-26 CSMIC 2008, InterContinental Hotel, Shanghai19
Top Related