Chemical Vapor Deposltlon(CVD) Processes: gift of Slo2-Expose Si to steam = uniform insulating layer or metal film growth: high vacuum, single element Contrast with CVD: toxic, corrosive gas flowing through valves T up to 1000 C, multiple simultaneous reactions, gas dynamics, dead layers.. whose ldea was It? DIELECTRIC SIN Sio POLY- SI GATE OXIDE BARRIER METAL SOURCE DRAIN WAFER All layers above poly-Si made by cvD, except gate oxide and aluminum Mon.. Sept. 15. 2003
Chemical Vapor Deposition (CVD) Processes: gift of SiO2 - Expose Si to steam => uniform insulating layer… or metal film growth : high vacuum, single element… CVD: toxic, corrosive gas flowing through valves, T … Contrast with up to 1000°C, multiple simultaneous reactions, gas dynamics, dead layers… whose idea was it? All layers above poly-Si made by CVD, except gate oxide and aluminum Mon., Sept. 15, 2003 1
CVD reactor reacton chamber (similar to those Control for si oxidation module Control T as motul low rate Mon., Sept. 15, 2003
CVD reactors Control module Four reaction chambers (similar to those for Si oxidation) Control T, gas mixture, pressure, flow rate Mon., Sept. 15, 2003 2
CVD is film growth from vapor/gas phase via chemical reactions in gas and on substrate e.g. SiH4 (g)- Si(s)+2H2(g) Do not want Si to nucleate above substrate(homogeneous nucleation) but on substrate surface(heterogeneous nucleation wall Reactor Transport of precursor Removal of across by-products dead layer to Susceptor substrate olysls: thermal/aun say decomposed species ond to subs decomposition More details at substrate Mon.. Sept. 15. 2003
CVD is film growth from vapor/gas phase via chemical reactions in gas and on substrate: homogeneous nucleation), e.g. SiH4 (g) Æ Si (s) + 2H2 (g) Do not want Si to nucleate above substrate ( but on substrate surface (heterogeneous nucleation). Twall Reactor Transport of precursors across dead layer to substrate Pyrolysis: thermal Susceptor film T sub> Twall Chemical reaction: Decomposed species bond to substrate decomposition at substrate More details… by-products Removal of Mon., Sept. 15, 2003 3
CVD Processes Bulk transport tansport of byproduct Reactan molecule ○ Duluson of 2) Transport Carrier gas (g)byproduct across andry (Maintain hi p, cO slow reaction d layer Decomposition 1∝D△C sorption O Reaction with film Surface diffusion Mon., Sept. 15, 2003
CVD Processes 8 1 Bulk Bulk transport transport of byproduct Reactant molecule 7 Diffusion of Transport Carrier gas 2 across bndry 4 (g) byproduct (Maintain hi p, layer Decomposition slow reaction) 6 Desorption 3 Adsorption 5 J1 µDgDC Reaction with film J2 ~ kiCi Surface diffusion Mon., Sept. 15, 2003 4
Hi vel low P Gas transport Low vel, hi P Laminar flow across plate Transport Hi vel. low acrosS boundary ∝D△C Plate Knudsen Nk Viscous flow 2 Tube Wall Laminar flow pipe Conductance aA/L Mon., Sept. 15, 2003
Gas transport J1 µDgDC Transport across boundary layer 2 Knudsen NK ≡ lL <1 L Viscous flow Dgas ª lvx 2 Mon., Sept. 15, 2003 5