some people calculated the average molecular speed in any direction, which is This is also accepted. (Note that the molecular speed is independent of pressure because both J and n are proportional to p. 2. SCCM stands for a flow of a"standard cubic centimeter per minute"'(standard cc is at temperature of 273 K and pressure of 760 Torr) L min 100 =0.001666 min人1000cm3人60s To change to 100 K and l mTorr L∥100KY760T 00066 =463 s八273K八10Tor CVD 3. Assume chemical equilibrium is established in a CVD reactor according to the quation Sih4 (g) (g)+H2(g) The temperature is maintained at 650C and the pressure at 0. 1 atm. If the equilibrium constant for the reaction is K(T)=2 x 10(Torr)exp[-1.8 eV/(kgT], find the partial pressure of each gas assuming P(H,) P(SiH,) 10 points. K(T=923K)=2×10°eX[-29×10J1ka×923 0.3 Torr Psi,X PH,-PsiHz=0.3 Torr (*)(assumption: PH2=Ps PH,+PH +PH=76 To in addition Psin, +2 76Tor(**) Substituting(**)into()2 some people calculated the average molecular speed in any direction, which is v = 8kT pm = 476 m s This is also accepted. (Note that the molecular speed is independent of pressure because both J and n are proportional to p.) 2. SCCM stands for a flow of a “standard cubic centimeter per minute” (standard cc is at temperature of 273 K and pressure of 760 Torr). 100 cm3 min Ê Ë Á Á ˆ ¯ ˜ ˜ L 1000cm 3 Ê Ë Á ˆ ¯ ˜ min 60s Ê Ë Á ˆ ¯ ˜ = 0.001666 L s To change to 100 K and 1 mTorr, 0.001666 L s Ê Ë Á ˆ ¯ ˜ 100 K 273 K Ê Ë Á ˆ ¯ ˜ 760Torr 10-3 Torr Ê Ë Á ˆ ¯ ˜ = 463 L s CVD 3. Assume chemical equilibrium is established in a CVD reactor according to the equation: SiH4 (g) ´ SiH2 (g) + H2 (g) The temperature is maintained at 650 C and the pressure at 0.1 atm. If the equilibrium constant for the reaction is K(T)=2 ¥ 109 (Torr) exp[-1.8 eV/(kBT)], find the partial pressure of each gas assuming p(H2) p(SiH2). 10 points. K(T = 923K) = 2 ¥109 exp -2.9 ¥10-19 J / k [ ] ( ) B ¥ 923K = 0.3 Torr Also, K = pSiH2 ¥ pH2 pSiH4 = pSiH2 2 pSiH4 = 0.3 Torr (*) (assumption : pH2 = pSiH2 ) I in addition, pSiH4 + pSiH2 + pH2 = 76 Torr pSiH4 + 2pSiH2 = 76 Torr (**) Substituting (**) into (*):