Presentation 7 thin film

Presentation 7 thin film - Historical Development and Basic...

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Historical Development and Basic Concepts Two main deposition methods are used today: 1. Chemical Vapor Deposition (CVD) 2. Physical Vapor Deposition (PVD) - APCVD, LPCVD, PECVD, HDPCVD - evaporation, sputter deposition Chemical Vapor Deposition (CVD) Quartz reaction chamber RF induction (heating) coils Exhaust scrubber rap Furnace - with resistance heaters Standup wafers iCl Silicon wafers Graphite susceptor vent Trap VaccumPump SiH 4 + O 2 SiO 2 + 2H 2 H 2 Ar H 2 +PH 3 H 2 +B2H 6 HCl SiCl 4 H 2 SiCl 4 + 2H 2 Si + 4HCl Gas control and sequencer SiH 4 O 2 Source Gases APCVD - Atmospheric Pressure CVD LPCVD - Low Pressure CVD
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Chemical Vapor Deposition 1 2 6 7 Gas stream Susceptor Wafer 34 5 1. Transport of reactants to the deposition region. *2. Transport of reactants from the main gas stream through the boundary yer to the wafer surface layer to the wafer surface. *3. Adsorption of reactants on the wafer surface. *4. Surface reactions, including: chemical decomposition or reaction, surface migration to attachment sites (kinks and ledges); site incorporation; and other surface reactions (emission and redeposition for example). *5. Desorption of byproducts. Transport of byproducts through boundary layer 6. Transport of byproducts through boundary layer. 7. Transport of byproducts away from the deposition region.
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D g Chemical Vapor Deposition J S = k S N S J g = δ N g N S ( ) = h g N g N S ( ) J S = J g k h N Growth Rate v = J S N = S g k S + h g g N Mass Transfer Limited: v h g N g N for k S >> h g where N is the number of atoms per nit volume in the film (5 x 10 22 m -3 Surface Reaction Limited : v k S N g N for h g >> k S unit volume in the film (5 x 10 cm for the case of epitaxial Si deposition) xample: alculate the deposition rate for a CVD system, =1.0 cm/s, =10 Example: Calculate the deposition rate for a CVD system, h g 1.0 cm/s, k s 10 cm/s, P total = 760 torr, P si =1 torr, T=1000 o C.
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CVD Calculation () ( ) 2 4 o 4 2 C 1200 at Process Deposition Reversible gas HCl solid Si gas H gas SiCl + + k s term with k s = k 0 exp(-E a /kT) rm with constant elocity cale) Reaction Etching Competing Surface Clean to Used be can Stream Input in HCl h G term with h G = constant Net growth velocity rowth v (log s c ( ) ( ) ( ) 2 4 Silane of ion Decomposit Pyrolytic - e Alternativ 2 gas SiCl solid Si gas SiCl + /T Reaction controlled Mass transfer controlled Mixed 2 600 4 2 H Si SiH C o + ⎯→ 1/T • The surface term is Arrhenius with E A depending on the articular reaction (1 6 eV for particular reaction (1.6 eV for single crystal silicon deposition).
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Presentation 7 thin film - Historical Development and Basic...

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