(Vacuum) Vacuum)? `Vacua` (1 ) Gas.5.5 10 19 molecular/cm 3
& Medium high vacuum High vacuum Very high vacuum 760 5 1 10-3 10-6 10-7 10-9 Low vacuum Medium vacuum High vacuum Very high vacuum Ultra-high vacuum Rough vacuum Fine vacuum
(Low vacuum) : 760 10-3 torr - Rough vacuum,. - Food processing,, (sputtering, LPCVD), (High vacuum) : 10-3 10-7 torr -. - -, CRT,, (evaporation), (Ultra high vacuum, UHV) : 10-8 torr - (monolayer) -,,,,
1608-1647 E. Torricelli 163-166 B. Pascal 1783 D. Bernoull 1859 J.K. Maxwell 1874 H.Mcleod 1905 W.Kaufman 1905 W.Gaeda : rotaty Pump, Diffusion pump 1906 M.Pirani 1909 1914 1937 194 1950 1950 1953 1958 1954 M. Knudsen G. Langmuir F.M. Penning Leak detector R.T. Bayard & D. Alpert R. Herb H.J. Schwartz W. Becker Vacuum Pump, Vacuum Gauge,,
1 = 76 cmhg H O () Hg : 13.53 g/cm 3 1 = 76 cmhg x 13.53 g/cm 3 = 108 cmh O 10 m
:. PV = C, P 1 V 1 = P V :. V = kt,, V/V 0 = T/T 0 P 1 V 1 /T 1 = P V /T, PV = kt PV = nrt = NkT 1 P 1 + ρv + ρgh1 = Const.
(1/6) : 1g ( = 1.66 x 10-4 g => 1 g = 6.0 x 10 3 ) 3 gas : : gas 1 mv = kt g( v) dv 3 = 4πv m πkt 3 e mv kt dv
V (/6) 8kT ( = vg v) dv = 0 πm 1,30 m/s, 467 m/s, 437 m/s, 394 m/sec, 1/ (impinge rate, arrival rate) A (molecules/cm sec) ( Ptorr, TK, Mg/mole) f = 1 4 nv = πmk ) ) 1 x 10-6 torr,, 300 K, N f = ( 1 x 10-6 x 133) / ( x 3.14 x 8 x 1.66 x 10-7 x 1.38 x 10 3 x 300 ) 1/ = 3.8 x 10 18 /m sec = 3.8 x 10 14 /cm sec P B T = 3.513 10 P MT
(3/6) (N 0 ) : 00,, 1 atm,,.4 liter => 6.03 x 10 3 Number density of gases : STP =>.7 x 10 19 #/cm 3 1 mtorr,, l um 3 => 35 Monolayer : cm 1, (A A g/cm 3 ), (B B g/mole), (N 0 #/mole) => = (( x ) ) / = A N 0 / B (#/cm 3 ) => 1 cm = (A( A N 0 /B) 1/3, = (B/A( N 0 ) 1/3 => monolayer = (A N 0 / B) /3 ex) Ti = 4.51 g/cm 3, = 47.9 g/mole monolayer = 1.476x10 15, monolayer =.6
(4/6) Y t = L / v x P x = m v x P t x = m v L x = F X 1 mv = 3 kt force pressure = ( L ) N P = L 0 m v L x = Nm v V mn( vx ) vx dvx nmvx P = = x = Nmv 3V = nn0mv 3V
NITROGEN 78.08 593.4 OXYGEN 0.95 159. ARGON 0.93 7.1 CARBON DIOXIDE 0.03 0.5 NEON 0.0018 1.38x10 - HELIUM 0.0005 4.0x10-3 KRYPTON 0.0001 8.66x10-4 HYDROGEN 0.00005 3.8x103-4 ZENON 0.0000087 6.6x10-5
:. 17.5 43.9 184.8 (torr) 10-4 ~ 10-7 10-5 ~ 10-10 10-3
(5/6) (5/6)
(6/6) (mean free path : ) : 0 λ = xdn ( cm) n λ 0 ( ) 1 n 3 v =V / λ = 5 / P(1 10 torr) E E t i = 4m m ( m + m ) i i t t cos θ m i << m t m i >> m t Et 4mimt 4m = E i i ( m + m ) mt i Et 4mimt 4m = E t ( m + m ) mi i t i t
Collision mean free path Elastic Collision Process/Inelastic Collision Process : Depending on whether the internal energies of colliding particles are conserved # of particle removed by collision in dx Fraction of incident particles colliding in dx Particles Targets dn = σnn dx dγn dx, dx g g dγ Γ Hard ball cross section =Q 1 Uncollided Flux Γ ngσ x x / λ ( x) = Γ e = Γ e 0 Mean Free path Mean time τ = 0 λ = λ υ n g 1 σ dn = n = n σdx g Collision Frequency v = τ 1 = n συ v = Kn g g Rate Constant K =συ
5 8 7 5 1 : : leakage 3 : 4 : roughing 10 9 <<<< 6 4 3 5 : 6 : roughing 7 : 8 : 11 1 1 9 : main 10 : water 11 : 1 : fore-line
Rough pumps (760 torr ~ 1 10-3 torr) Rotary oil sealed mechanical pump Sorption pump Venturi pump Booster pump High vacuum pumps (1 10-3 torr ~ 1 10-8 torr) Diffusion pump Cryopump Cryotrap Turbomolecular pump Ultrahigh vacuum pumps (1 10-8 torr ) Titanium sublimation pump Sputter ion pump
Pressure ranges of various Pumps Ultrahigh Vacuum High Vacuum Rough Vacuum Venturi Pump Rotary Piston Pump Dry Mechanical Pump Oil-sealed Mechanical Pump Sorption Pump Blower/Booster Liquid Nitrogen Trap Diffusion Cryopump Turbo Ion pump TSP (Torr) -1-10 - 8-6 - 4-0
( )
(Oil Diffusion)
(Oil Diffusion)
(Oil Diffusion)
Typical gauge Pressure Ranges (Torr) -1-10 - 8-6 - 4-0 Gold Cathode Gauge Bourdon Gauge Thermocouple Gauge Pirani Gauge Capacitance Manometer Residual Nitrogen Analyzer Ionization Gauge Residual Gas Analyzer
760 torr ~ 1 torr
TC
Ion Gauge (BA Gauge)
Cold Cathode Gauge