Post on 05-Jan-2016
SUPREM Simulation
ECE/ChE 4752: Microelectronics ECE/ChE 4752: Microelectronics Processing LaboratoryProcessing Laboratory
Gary S. May
March 18, 2004
Outline
IntroductionIntroduction Diffusion SimulationDiffusion Simulation Oxidation SimulationOxidation Simulation Ion Implant SimulationIon Implant Simulation
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)
Caution
SUPREM is not infallible (although it’s 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.
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
Outline
IntroductionIntroduction Diffusion SimulationDiffusion Simulation Oxidation SimulationOxidation Simulation Ion Implant SimulationIon Implant Simulation
Flux
All diffusion simulators based on 3 basic equations
Flux:
where: Zi = charge state of the impurity
i = mobility of the impurity = electric field
Ji Di–xd
dC i ZiiC i+=
Continuity
where: Gi = recombination rate of the impurity
td
dC i
xd
dJi+ G i=
Poisson’s Equation
where: = dielectric constant n = electron concentration p = hole concentration ND = ionized donor concentration NA = ionized acceptor concentration
xdd q p n– ND NA–+ =
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)
D D0 Ea kT– exp=
Example
go ssuprem3
Title Pre-deposition of Boron
Comment Initialize the silicon substrate
Initialize <100>Silicon Phosphor Concentration=1e16
Comment Diffuse boron
Diffusion Time=15 Temperature=850 Boron Solidsol
Print Layers Concentration Phosphorus Boron Net
TonyPlot -ttitle “Boron Predep”
Structure outfile=predep.str
Stop End example
Pre-Deposition Example
Outline
IntroductionIntroduction Diffusion SimulationDiffusion Simulation Oxidation SimulationOxidation Simulation Ion Implant SimulationIon Implant Simulation
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:DiffusionTime=30 Temperature=1000 DryO2
Outline
IntroductionIntroduction Diffusion SimulationDiffusion Simulation Oxidation SimulationOxidation Simulation Ion Implant SimulationIon Implant Simulation
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 p) 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 Energy=60 Dose=5e15