ECE6450L13and14-CVD and Epitaxy

ECE6450L13and14-CVD and Epitaxy - Lecture 13 and 14 Thin...

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ECE 6450 - Dr. Alan Doolittle Georgia Tech Lecture 13 and 14 Thin Film Deposition and Epitaxy (Chemical Vapor Deposition, Metal Organic CVD and Molecular Beam Epitaxy) Reading: Chapters 13 and 14
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ECE 6450 - Dr. Alan Doolittle Georgia Tech Chemical Vapor Deposition Chemical gas sources are thermally, optically, or electrically (plasma) reacted with a surface to “leave” behind deposits with reaction byproducts pumped out of the reaction tube or vacuum chamber.
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ECE 6450 - Dr. Alan Doolittle Georgia Tech 1.) Atmospheric Pressure CVD (APCVD) Advantages: High deposition rates, simple, high throughput Disadvantages: Poor uniformity, purity is less than LPCVD Used mainly for thick oxides. 2.) Low Pressure CVD (LPCVD at ~0.2 to 20 torr) Advantages: Excellent uniformity, purity Disadvantages: Lower (but reasonable) deposition rates than APCVD Used for polysilicon deposition, dielectric layer deposition, and doped dielectric deposition. 3.) Metal Organic CVD (MOCVD) Advantages.: Highly flexible—> can deposit semiconductors, metals, dielectrics Disadvantages: HIGHLY TOXIC! , Very expensive source material. Environmental disposal costs are high. Uses: Dominates optical (but not electronic) III-V technology, some metalization processes (W plugs and Cu) 4.) Plasma Enhance CVD Plasmas are used to force reactions that would not be possible at low temperature. Advantages.: Uses low temperatures necessary for rear end processing. Disadvantages: Plasma damage typically results. Used for dielectrics coatings. Four Basic CVD Reactors
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ECE 6450 - Dr. Alan Doolittle Georgia Tech Low Pressure Chemical Vapor Deposition (LPCVD) can be used for a variety of materials: •Polysilicon for gate contacts •Thick oxides used for isolation between metal interconnects •Doped oxides useful for global planarization •Nitrides and other dielectrics for isolation or capacitors (higher K materials for larger capacitance) •Metals for seed layers for vias and interconnect lines (not typically used for the entire metal line due to slow deposition rate) Polysilicon Uses: Gate contact in MOS (prevents metal/oxide reactions) and very short interconnect lines. Also, resistors in analog technologies. Typically uses Si containing compounds (typically 100% silane, SiH 4 , or 20-30% silane/ 80-70% inert gas) are reacted with the wafer at ~0.2 to 1 torr and ~575-650. The temperature range is limited by: •Limited by low deposition rate at low temperature end (insufficient thermal energy for the reaction) •Formation of particles in the gas phase (gas spontaneously reacting before it reaches the wafer) and poor adhesion on the upper temperature end LPCVD for Si Technology
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ECE 6450 - Dr. Alan Doolittle Georgia Tech LPCVD for Si Technology Deposition rate is limited by reaction rate (controlled by temperature and pressure) and arrival rate (controlled by pressure (remember gas throughput is related to pressure by Q=CP)) .
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ECE 6450 - Dr. Alan Doolittle Georgia Tech Crystalline Structure is also controlled by temperature. Poly-Si can be doped using Diborane (B
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This note was uploaded on 08/23/2011 for the course ECE 6450 taught by Professor Doolittle during the Fall '10 term at University of Florida.

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ECE6450L13and14-CVD and Epitaxy - Lecture 13 and 14 Thin...

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