Process Gas Distribution and Control - Seminar Module Outline

Introduction
	Groundrules, instructor introduction, objectives
	Course overview (tailored to specific course content)
The nature of engineering requirements
	Authority, tradition, standards, and common knowledge vs. data
	To progress we must be willing to see things differently
	Classifying requirements (exercize)
The nature of gases
	The usefulness of gases
	What is different about handling semiconductor process gases?
	What is different about measuring semiconductor process gases?
	The ideal gas law
	Volumetric flow vs. mass flow
	Why use volumetric units for mass flow?
	Surface effects - adsorption
Basic semiconductor structures
	CMOS transistor, contact and DRAM structure
	Interconnect
Basic semiconductor processes using gases
	Themes in wafer processing
	Elements of the process environment
	Chemical reaction with the wafer
	Dry etch
	Principles of dry etch
	Deposition
	Cleaning the process chamber
Gas distribution
	Distribution system architecture
		Elements of the system
		Alternative architectures
		Pressure levels within the system
	Safety
		Pressure ratings
		Leak integrity
		Isolation
		Ventilation
		Double containment
		Flow limitation
		Abatement
	Connections and splices
		Connecting the parts of the system
		Sealing methods compared
		Gaskets and seals - examples
		Fittings
		Welding
		Bending
	Purging
		Displacement
		Concentration differential
		Entrainment

		Cycle
		Automated purging
	Leaks
		Internal vs. external leaks
		What is likely to leak?
		What causes leaks?
		The effects and consequences of leaks
			Inert gases
			Movement of gas through a leak, bidirectional diffusion
			corrosive gases
			Pyrophoric gases
			Toxic gases
		Measuring system leak integrity
			Pressure decay testing
			Helium mass spectrometer
		Virtual leaks
			Dead legs
			Crevices and cavities
			Surface effects
		Detecting hazardous gas in ambient air
	Cylinder cabinets
		Typical valve panels
	Bulk gas supply
	Valve manifold boxes
	Condensable / corrosive / reactive gases
	Safe Delivery System (SDS)
		SDS vs. high pressure sources
		adsorption / desorbtion curves vs. pressure
		cylinder capacity table
	Vaporized liquids distributed as gases
		examples
		Preventing condensation in the delivery system
		Selective distillation in the bottle
	Liquids which are vaporized at point-of-use
		examples
		bubblers vs. vaporizers
		metering the liquid vs. metering the vapor
		Liquid handling
	Unstable gases

		highly diluted mixtures
		Ozone
Gas purity
	Particles
		Particle sources
		Detecting and measuring particles
			Laser particle counters
			CNC particle counters
	Molecular contaminants
		Moisture
			Moisture measurement
		Chemical impurities
	Materials of construction
	Surface finish
	Surface passivation
Flow control
	Flow Calibration Metrology
		Primary or secondary?
		Transfer standards get no respect
		Dealing with nasty gases
		Volumetric primary
		Variable pressure primary
		Gravimetric primary
		Critical flow nozzles
		Laminar flow elements
		Thermal mass flow meters
		Calibration Traceability
	Flow controllers, general
		Mass flow control requirements
		Closed-loop controllers
		Controller error
		Control and monitoring signals
		Analog vs. digital signaling
		Proportional control valves, magnetic, piezoelectric
	Thermal MFCs
		Thermal MFC issues
		Thermal mass flow measurement
			Thermal sensor principles
			Thermal sensor excitation options
			Ranging with shunts (bypasses)
			Split ratio issues (bypass - sensor behavior differences)
		Thermophysical gas properties
			Density
			Molar specific heat
			Thermal conductivity
			Viscosity
		Conversion functions

		Sources of error
		How to upset an MFC by design
		Strengths and weaknesses
	Pressure based MFCs
		Introduction to pressure based flow measurement
		Sonic flow devices
		Orifice vs. nozzle
		LFE based devices
		Pressure based MFC issues
		conversion functions
		Sources of error
		Thermal vs. pressure MFCs: strengths and weaknesses
	Micro-machined devices
	Liquid MFCs
	Flow controller specification parameters (definition, measurement, typical values)
		Accuracy
		Turndown
		Repeatability
		Reproducibility
		Hysterisis
		Long-term stability, zero, span
		Temperature effects
			Zero effect
			Span effect
		Pressure effects
			Steady-state
			Transient
		Transient characteristics
			Typical response curves
			Starting, changing and stopping flow
			Dead time, response time, settling time
			Measuring transient characteristics
			Settling the last two percent
		Electrical supply effects
		System effects
		Sequencing
Valves
	Actuators
		Manual
		Manual with lockout / tagout
		Pneumatic
	Moving seals
		Bellows
		Diaphragm
	Poppet / seat
		Soft seats
		all-metal valves

	Cv - flow capacity
	Pressure rating
	Inlet vs. outlet
	Multi-ported valves
	Pilot valves
	Actuation delay
	Valve failure modes
	Valve position detectors
Pressure regulators
	How mechanical regulators work
		Loading the diaphragm
		Connecting the valve to the diaphragm
		The significance of mechanical gain and damping
	Characteristics / specifications
		Lockup / creep
		Burp
		Inlet pressure effect
		Droop
		Oscillation
	Electronic regulators
	Regulator failure modes
	Interactions between regulators and MFCs
Filters and purifiers
	What makes filters work?
	Filter material
		Teflon
		Metal
		Ceramic
	Flow resistance
	Purifiers
		Purifier types / strengths / weaknesses
			Getter
			Resin
			Molecular sieve
			Chemical sequestering
	Gas compatibility
	End-point detection
Pressure measurement
	Mechanical pressure gauges
		Bourdon tube
	Electronic gauges
	Diaphragms and other isolation structures
		Sensing the force
			Strain gauge
			Semiconductor gauge
			Variable capacitance
	Characteristics / specifications
		Working range

		Accuracy
		Repeatability
		Hysterisis
Process tool gas systems
	The gas stick
	Simple gas systems
	The inert gas stick
	Reactive gas sticks
	Designing for efficient purging
	Gas isolation
	Interlocks
	Heating lines
	Maintaining system purity while servicing components
	System design checklist
	Questionable practices
	Safety and design standards
	Modular / integrated gas systems
	Gas box (and tool) control architecture
		Analog interface with central control
		Sensor bus with central control
		Sensor bus with distributed control
		Multiple sensor buses with distributed control
		Implementing sensor bus at a low level: implications
Troubleshooting gas systems
	Symptoms
		No flow
		MFC will not control above some setpoint
		MFC will not control below some setpoint
		Flow oscillates
		The first wafer effect
	(this section still in development)