Etching – Part 2 - folk.ntnu.nofolk.ntnu.no/jonathrg/fag/TFE4180/slides/Ch16 Etching (Part...
Transcript of Etching – Part 2 - folk.ntnu.nofolk.ntnu.no/jonathrg/fag/TFE4180/slides/Ch16 Etching (Part...
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TFE4180 Semiconductor Manufacturing TechnologyTFE4180 Semiconductor Manufacturing Technology
Etching – Part 2Chapter : 16 Semiconductor Manufacturing Technology by M. Quirk & J. Serda
Spring Semester 2014
Saroj Kumar PatraTFE4180 Semiconductor Manufacturing Technology,
Norwegian University of Science and Technology ( NTNU )
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TFE4180 Semiconductor Manufacturing Technology
Introduction• Plasma dry etch reactors
• Barrel plasma etcher• Parallel plate etcher• Downstream etcher• Triode planar reactor• Ion beam milling• Reactive ion etch• High-density plasma etchers
• Requirements• Reaction chamber• RF• Gas• Vacuum
F2 SiO2
Cl, F2 AlBr2, Cl, F2 SiO2 Photoresist
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TFE4180 Semiconductor Manufacturing Technology
Barrel reactor
• 0.1-1torr• Almost purely chemical process
• Isotropic etching• High selectivity
• Wafers parallell to E-field• Minimal plasma-induced damage
• Typically used for photoresist stripping with O2
Vacuum pump
Gas in
RF electrode
RFgenerator
Wafers
Quartz boat
WafersReaction chamber
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TFE4180 Semiconductor Manufacturing Technology
Parralel plate (planar) reactor
• 0.1-1 Torr• Direct contact with plasma/energetic ions• High-energy ion bombardment• Early reactor
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TFE4180 Semiconductor Manufacturing Technology
Downstream etch systems
• 0.1-1 Torr• Plasma in separate chamber
• Transfered to reaction chamber• Uniformly distribution of plasma on surface
• Chemical etching• Isotropic
• 2.45 GHz source
Plasma chamberDiffuser
Wafer chuck
Heat lampTo vacuum system
Microwave energy Microwave source 2.45 GHz
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TFE4180 Semiconductor Manufacturing Technology
Triode planar reactor
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TFE4180 Semiconductor Manufacturing Technology
Ion beam milling
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Hot filament emits electrons
Gas inlet(Argon)
To vacuum system
Neutralizing filamentAccelerating gridScreen grid
Electromagnet improves ionization
Plasma chamber(+anode repels +ions)
Wafer can be tilted to control etch profile
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TFE4180 Semiconductor Manufacturing Technology
Reactive ion etch (RIE)
RF generator
Wafer
Powered electrode(cathode)
Grounded electrode
(anode)
Ar+
(physical etch t)F
(chemical etch)
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TFE4180 Semiconductor Manufacturing Technology
High-density plasma etchers
• Predominant dry etching methodology.• Difference from standard plasma etching:
• Better for small geometries (>0.25µm)• Lower pressure (1-10 mtorr)• Higher degree of ionization (10%)
• Electron Cyclotron Resonance (ECR)• Inductively-Coupled Plasma (ICP)• Dual Plasma Source (DPS)• Magnetically Enhanced Reactive Ion Etch (MERIE)
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TFE4180 Semiconductor Manufacturing Technology
Electron cyclotron resonance (ECR)• Introduced in early 1980s• Microwave excitation• Magnetic field parallel to reactant flow• Electron cyclotron resonance• Both physical and chemical etch
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TFE4180 Semiconductor Manufacturing Technology
Inductively-coupled plasma (ICP)
Electromagnet
Dielectric window/ quartz tube
Inductive coil
Biased wafer chuck
RF generator
Bias RF generator
Plasma chamberPlasma
chamber
• Simple reactor that is widely used in the US. • Plasma is generated from a spiral coil separated by a
dielectric window/quartz tube• Both physical and chemical etch
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TFE4180 Semiconductor Manufacturing Technology
Dual plasma source (DPS)• RF power applied to both coil (source) and wafer electrode (bias)• Lower chamber is clean• Upper chamber exposed to process gasses.• Key aspect, decoupling of the source plasma power from the bias.
Decoupled plasma chamber
Decoupled plasma chamber
Turbo pump
Lower chamber
Cathode
Wafer
Capacitively-coupled RF generator (bias power)
Inductively-coupled RF generator (source power)
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TFE4180 Semiconductor Manufacturing Technology
Magnetically enhanced RIE (MERIE)
• Similar to reactive ion etch (RIE)• Magnetic field holds plasma away for chamber walls.• Increase in plasma density
Electromagnet (1 of 4)
13.56 MHz
Biased wafer chuck
WaferWafer
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TFE4180 Semiconductor Manufacturing Technology
Etch system reviewConfigurations Activity Pressure
(Torr) Arrangement High
Density Plasma
Biasing Bias Source Profile
Barrel Reactive 10-1 to 1 Coil or electrodes outside vessel No In cassette (bulk) RF Isotropic
Parallel Plate (Plasma) Reactive 10-1 to 1 Planar diode (two electrodes) No On powered electrode (anode) RF Anisotropic
Downstream Plasma Reactive 10-1 to 1 Coil or electrodes outside vessel No
In cassette (bulk) downstream of plasma
RF or Microwave Isotropic
Triode Planar Reactive 10-3 Triode (three electrodes) No On platform electrode Anisotropic
Ion Beam Milling Inert 10-4 Planar triode No On powered electrode (anode) Anisotropic
Reactive Ion Etch (RIE) Reactive < 0.1 Planar or cylindrical diode No On cathode Anisotropic
Electron Cyclotron Resonance (ECR) Reactive
10-4 to 10-
3 (low)
Magnetic field in parallel with plasma flow Yes On cathode RF or DC Anisotropic
Distributed ECR Reactive (low) Magnets distributed around central plasma Yes On cathode RF or DC Anisotropic
Inductively Coupled Plasma (ICP) Reactive (low) Spiral coil separated from
plasma by dielectric plate Yes On cathode RF or DC Anisotropic
Helicon Wave Reactive (low)
Plasma generated by electromagnets and plasma density maintained at wafer by magnetic field
Yes On cathode RF or DC Anisotropic
Dual Plasma Source Reactive (low) Independent plasma and wafer biasing Yes On cathode RF or DC Anisotropic
Magnetically Enhanced RIE (MERIE)
Reactive (low) Planar diode with magnetic field confining plasma Yes On cathode RF or DC Anisotropic
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TFE4180 Semiconductor Manufacturing Technology
Endpoint detectionEndpoint detectionNormal etch Change in etch
rate - detection occurs here.
Endpoint signal stops the etch.
Time
Etch
Par
amet
er
Material Etchant Gas Emitting Species of some Products Wavelength (nm)
Silicon CF4/O2 Cl2
SiF SiCl
440; 777 287
SiO2 CHF3 CO 484
Aluminum Cl2 BCl3
Al AlCl
391; 394; 396 261
Photoresist O2 CO
OH H
484 309 656
Nitrogen (indicating chamber vacuum leak)
N2
NO 337 248
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TFE4180 Semiconductor Manufacturing Technology
Vacuum for etch chambers
• Critical for the plasma parameters
• Has a set of predefined specifications
• High removal rate
• May require special designs
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TFE4180 Semiconductor Manufacturing Technology
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