SUPREM Simulation

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SUPREM Simulation

• ECE/ChE 4752 Microelectronics Processing
  Laboratory

Gary S. May March 18, 2004
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Outline

• Introduction
• Diffusion Simulation
• Oxidation Simulation
• Ion Implant Simulation

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SUPREM

• Except for a few simple cases, complications may
  arise in the calculation of diffusion and ion
  implantation profiles, and oxidation rates
• Numerical methods have been developed to perform
  these computations in 1, 2, or 3 dimensions
• Numerical simulations can be used optimize
  process recipes and test process sensitivity
  without costly and time-consuming experiments
• One simulator SUPREM (Stanford University
  PRocess Engineering Module)
• Silvaco software version of SUPREM is called
  SSUPREM3 (1-D) or SSUPREM4 (2-D)

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Caution

• SUPREM is not infallible (although its pretty
  good), since its accuracy depends on the quality
  of models, parameters, and numerical techniques
  it employs.
• SUPREM results should be verified experimentally
  at least once to ensure accuracy.

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SUPREM Input Deck

• Title card
• Comment repeated on each page of the output
• Comments
• Initialization statement
• Sets substrate type, orientation, and doping
• Sets thickness of region to be simulated and
  establishes a grid
• Materials statements
• Process statements
• Output statements

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Outline

• Introduction
• Diffusion Simulation
• Oxidation Simulation
• Ion Implant Simulation

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Flux

• All diffusion simulators based on 3 basic
  equations
• Flux
• where Zi charge state of the impurity
• mi mobility of the impurity
• x electric field

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Continuity

• where Gi recombination rate of the impurity

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Poissons Equation

• where
• e dielectric constant
• n electron concentration
• p hole concentration
• ND ionized donor concentration
• NA ionized acceptor concentration

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Solution

• These 3 equations are solved simultaneously over
  a user defined 1-D grid
• Diffusivity is calculated using
• where the values of D0 and Ea are included in a
  look-up table for B, Sb, As in Si
• Empirical models are added to account for
  non-standard diffusion (i.e., oxidation-enhanced,
  oxidation-retarded, or field-aided)

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Example

• go ssuprem3
• Title Pre-deposition of Boron
• Comment Initialize the silicon substrate
• Initialize lt100gtSilicon Phosphor
  Concentration1e16
• Comment Diffuse boron
• Diffusion Time15 Temperature850 Boron Solidsol
• Print Layers Concentration Phosphorus Boron Net
• TonyPlot -ttitle Boron Predep
• Structure outfilepredep.str
• Stop End example

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Pre-Deposition Example
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Outline

• Introduction
• Diffusion Simulation
• Oxidation Simulation
• Ion Implant Simulation

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Oxidation

• SUPREM can also be used to simulate oxidation
  using the Deal/Grove model
• SUPREM uses Arrhenius functions to describe the
  linear and parabolic rate coefficients for wet
  and dry oxidation
• Oxidation processes are accessed using the same
  command as diffusion processes DIFFUSION
• For oxidation, parameters DRYO2 or WETO2 are
  added
• EXAMPLE
• Diffusion Time30 Temperature1000 DryO2

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Outline

• Introduction
• Diffusion Simulation
• Oxidation Simulation
• Ion Implant Simulation

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Ion Implantation

• SUPREM can calculate ion implant profiles
• Simulated impurities can be implanted, activated,
  and diffused
• SUPREM contains data for the implant parameters
  (Rp and sp) for most dopants for unusual
  materials, the user must provide this data
• SUPREM can also handle implantation through
  multiple layers (i.e., through an oxide)
• EXAMPLE
• Implant Arsenic Energy60 Dose5e15