III. Vacuum PumpsIII. Vacuum Pumps
MechanismGas transferGas capture
FunctionFunctionRoughing (backing, mechanical pumps)
Rotary vaneSorption Rotary lobe Scroll ScrewSorption, Rotary lobe, Scroll, Screw
High vacuumOil diffusion, Turbomolecular, Cryo, Ion
AuxiliaryTitanium Sublimation, LN2
Liu, UCD Phy250-1, 2011, NanoFab16
IIIIII--A. Roughing: Rotary Vane Pump A. Roughing: Rotary Vane Pump (Gas Transfer)(Gas Transfer)(Gas Transfer)(Gas Transfer)
Single-stage10-2 torr
Dual-stage10-3 torr
Speed: 1-100 cfmOil: lubricant, coolant, sealant, contaminationForeline trap: copper gauze, molecular sieve, LN2Pumping reactive/flammable/O2 gas:
Chemically inert fluid: Fomblin PFPE (perfluoropolyethers)
Liu, UCD Phy250-1, 2011, NanoFab17
Chemically inert fluid: Fomblin PFPE (perfluoropolyethers)Ballast valve; Gas bubbler; Venting (anti-suckback); Exhaust; Vibration
Roughing: Sorption Pump Roughing: Sorption Pump (Gas Capture)(Gas Capture)( p )( p )
10-3 - 10-4 torr10 10 torrOil free, no moving partsDrawback:
Initial cooling
Liu, UCD Phy250-1, 2011, NanoFab18
gLimited capacity, need regenerationGas selective- difficulty w/ inert gases
Liu, UCD Phy250-1, 2011, NanoFab19
Roughing: Diaphragm Pumps Roughing: Diaphragm Pumps (Dry, Gas Transfer)(Dry, Gas Transfer)( y, )( y, )
< 10cfm
1-10 torr
Exhaust into atmosphereExhaust into atmosphere
Low cost
Liu, UCD Phy250-1, 2011, NanoFab20
Kurt J. Lesker
Roughing: Roots (Rotary Lobe) Pump Roughing: Roots (Rotary Lobe) Pump (Dry, Gas Transfer)(Dry, Gas Transfer)( y, )( y, )
RootsGas transfer0.01-10 torr(10-4 torr when backed) Handle high gas loadsHandle high gas loads
Liu, UCD Phy250-1, 2011, NanoFab21
Kurt J. Lesker
Roughing: Other Dry PumpsRoughing: Other Dry Pumps
Kurt J. Lesker
ScrollG f
ScrewGas transferGas transfer
10-2 torr12-25 cfm
Gas transfer10-3 torr30-320 cfmMay handle aggressive gases
Liu, UCD Phy250-1, 2011, NanoFab22
May handle aggressive gases
IIIIII--B. High Vacuum: Oil Diffusion PumpB. High Vacuum: Oil Diffusion Pump(Wet, Gas Transfer)(Wet, Gas Transfer)( , )( , )
Momentum transfer
10-7 -10-8 torr or better30 L/s - 50,000 L/sOil: Very low vapor pressure
O2 resistantBaffles & LN2 trap
Kurt J. LeskerBaffles & LN2 trap
Advantages: Inexpensive, simple, non-gas-selective, durable, quietDisadvantages: oil backstreaming (LN2 trap, baffles)
Liu, UCD Phy250-1, 2011, NanoFab23
upright, load < 300mtorr, need backingslow start/shut-down
High Vacuum: Turbomolecular PumpHigh Vacuum: Turbomolecular Pump(Dry, Gas Transfer)(Dry, Gas Transfer)( y, )( y, )
10-7 -10-10 torr10 -10 torr 50 L/s - 3500 L/sCrossover P: ~ 1000 mtorr
Gas selective: Easy w/ heavy moleculesdifficulty w/ H2, He
High speed, screenOften verticalOften verticalBearings
Ceramic M ti ll l it t d
Liu, UCD Phy250-1, 2011, NanoFab24
Magnetically levitated
High Vacuum: Cryo PumpHigh Vacuum: Cryo Pump(Dry, Gas Capture)(Dry, Gas Capture)( y, p )( y, p )
Cryo-condensation + cryo-sorptionClosed-cycle He cryocompressor10-9 torr or betterAny orientationNo backing neededNo backing neededCrossover P: ~ 500 mtorr
Gas selecti e: diffic lt / HeGas selective: difficulty w/ HeRegeneration & replacement
KJL
Liu, UCD Phy250-1, 2011, NanoFab25
KJL
UHV Pump: Ion PumpUHV Pump: Ion Pump(Gas Capture)(Gas Capture)( p )( p )
KJLKJL
Liu, UCD Phy250-1, 2011, NanoFab26
Chemical reaction w/ Ti (getter) + burial (ion implantation)
Reactive gases All gases
10-12 torrCross over P: ~<1mtorrAny orientationAny orientationClean, bakeable, vibration-freePermanent magnet: ionization; heavy
Gas selective: difficulty w/ inert gasLow throughput
Liu, UCD Phy250-1, 2011, NanoFab27
Ti refurbish necessary
HV Pump ComparisonHV Pump Comparison
Liu, UCD Phy250-1, 2011, NanoFab28
IIIIII--C. Auxiliary: Titanium Sublimation PumpC. Auxiliary: Titanium Sublimation Pump(Dry, Gas Capture)(Dry, Gas Capture)( y, p )( y, p )
Sublime Ti-Mo, continuous/pulseChemical reactionGas selective: no inert gasGas selective: no inert gasBetter at LN2:
Pump speed & heat insulationProper partitionOperates < 10-6 torr
Liu, UCD Phy250-1, 2011, NanoFab29
Auxiliary: LNAuxiliary: LN22(Gas Capture)(Gas Capture)( p )( p )
Cryopumping
LN trapLN2 trapCryopanel
Continuous LN2 feed$0.25 /L
Liu, UCD Phy250-1, 2011, NanoFab30
IIIIII--D. Vacuum SystemsD. Vacuum SystemsExample: Diffusion pump system
Safeguards:Water interlockT i l k
Liu, UCD Phy250-1, 2011, NanoFab31
Temperature interlockPressure interlock
