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Section 5: Thin Film Deposition Part 2: Chemical Methods

Section 5: Thin Film Deposition Part 2: Chemical Methods. Jaeger Chapter 6. Chemical Vapor Deposition (CVD). source. chemical reaction. film. substrate. More conformal deposition vs. PVD. t. t. Shown here is 100% conformal deposition. step. LPCVD Examples. LPCVD Examples.

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Section 5: Thin Film Deposition Part 2: Chemical Methods

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  1. Section 5: Thin Film DepositionPart 2: Chemical Methods Jaeger Chapter 6 EE143 – Ali Javey

  2. Chemical Vapor Deposition (CVD) source chemical reaction film substrate More conformal deposition vs. PVD t t Shown here is 100% conformal deposition step EE143 – Ali Javey

  3. LPCVD Examples EE143 – Ali Javey

  4. LPCVD Examples EE143 – Ali Javey

  5. reactant 5 stagnant gas layer 1 surface diffusion 2 3 4 substrate CVD Mechanisms 1 = Diffusion of reactant to surface 2 = Absorption of reactant to surface 3 = Chemical reaction 4 = Desorption of gas by-products 5 = Outdiffusion of by-product gas EE143 – Ali Javey

  6. CVD Deposition Rate [Grove Model] film Si F1 F3 d d = thickness of stagnant layer = F D [ CG - CS] / d 1 = F kS CS 3 EE143 – Ali Javey

  7. Grove model of CVD (cont’d) EE143 – Ali Javey

  8. Deposition Rate versus Temp gas transport limited [log scale] Rate surface-reaction limited 0 1/T high T low T EE143 – Ali Javey

  9. Growth Rate Dependence on Flow Velocity EE143 – Ali Javey

  10. LPCVD Features (1) More conformal deposition, if T is uniform (2) Inter-wafer and intra-wafer thickness uniformity less sensitive to gas flow patterns. (i.e. wafer placement). Wafer topography EE143 – Ali Javey

  11. Comments about LPCVD (1) Sensitivity to gas flow pattern Furnace tube wafers (2) Mass depletion problem more less in out EE143 – Ali Javey

  12. Plasma Enhanced CVD • Ionized chemical species allows a lower process temperature to be used. • Film properties (e.g. mechanical stress) can be tailored • by controllable ion bombardment with substrate bias voltage. EE143 – Ali Javey

  13. Atomic Layer Deposition • The process involves two self-limiting half reactions that are repeated in cycles • Unlike CVD, in ALD pulses of precursors are introduced in each cycle • ALD is highly conformal and enables excellent thickness uniformity and control down to nm-scale EE143 – Ali Javey

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