Chemical vapor deposition 2. You are using a CVd system for which the data shown below have been proven reliable for the growth of poly Si. 130012001100100900800 Sig(Na) Transfer Limited Resction StH?CI Limited SH CIa Sicle 0.6 10/7K) a) Write the chemical reaction for Silane pyrolysis to grow Si at 650 C. 31 b) Is this film growth reaction-rate limited or gas transport limited?.31 c) How would you calculate the activation energy for this reaction?B31 d)Calculate the activation energy from the figure. 3 e) You want to grow your Si film more smoothly and with higher density. To achieve this, would you do the following(explain in I sentence) 1 Increase or decrease processing temperature, T?[2] 11) Increase or decrease gas flow rate?.3 ii1 Increase or decrease Silane concentration, C. 31 a a)SiH4(g)=> Si(s)+2H2(g) b) From figure above, it is reaction-rate limited (strong linear In(v)vs 1/T) c)AG is given by the slope of these In(v)vs. I/T curves in the reaction-limited regime d)Using the two points at about 650 C, 0. I um/min (1.67x 10 cm/s)and 750 C 0.01 um/min, the change inIn(v)is 2.3 and the change in 1/T is 1.06x 10-. Include Boltzman constant to get AG=1.87eV(3 x 10-9J e)1) Increase T, it gives more surface mobility to reacting species. Also correct would be to say decrease T to slow down the reaction-limited growth rate 11) Reaction-limited process is not affected by gas flow rate. Also accepted was: decrease gas flow rate to have less burial of surface-diffusing species which is more appropriate for transport-limited case iii)Decrease SiH, concentration to slow down all fluxes2 Chemical vapor deposition 2. You are using a CVD system for which the data shown below have been proven reliable for the growth of poly Si. a) Write the chemical reaction for Silane pyrolysis to grow Si at 650 C. [3] b) Is this film growth reaction-rate limited or gas transport limited? . [3] c) How would you calculate the activation energy for this reaction? . [3] d) Calculate the activation energy from the figure. . [3] e) You want to grow your Si film more smoothly and with higher density. To achieve this, would you do the following (explain in 1 sentence) i) Increase or decrease processing temperature, T? . [2] ii) Increase or decrease gas flow rate? . [3] iii) Increase or decrease Silane concentration, Cg . [3] A a) SiH4 (g) => Si(s) + 2H2(g). b) From figure above, it is reaction-rate limited (strong linear ln(v) vs 1/T). c) DG is given by the slope of these ln(v) vs. 1/T curves in the reaction-limited regime. d) Using the two points at about 650 C, 0.1 µm/min (1.67 ¥ 10-7 cm/s) and 750 C, 0.01 µm/min, the change in ln(v) is 2.3 and the change in 1/T is 1.06 ¥ 10-4. Include Boltzman constant to get DG ≈ 1.87 eV (3 ¥ 10-19 J). e) i) Increase T, it gives more surface mobility to reacting species. Also correct would be to say decrease T to slow down the reaction-limited growth rate. ii) Reaction-limited process is not affected by gas flow rate. Also accepted was: decrease gas flow rate to have less burial of surface-diffusing species, which is more appropriate for transport-limited case. iii)Decrease SiH4 concentration to slow down all fluxes