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