1. SUPREM Simulation ECE/ChE 4752: Microelectronics Processing Laboratory Gary S. May March 18, 2004

2. Outline  Introduction Diffusion Simulation Diffusion Simulation Oxidation Simulation Oxidation Simulation Ion Implant Simulation Ion Implant Simulation

3. 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)

4. 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.

5. 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

6. Outline Introduction Introduction  Diffusion Simulation Oxidation Simulation Oxidation Simulation Ion Implant Simulation Ion Implant Simulation

7. Flux All diffusion simulators based on 3 basic equations Flux:   where: Z i = charge state of the impurity    i = mobility of the impurity    = electric field

8. Continuity where: G i = recombination rate of the impurity

9. Poisson’s Equation where:    = dielectric constant   n = electron concentration   p = hole concentration   N D = ionized donor concentration   N A = ionized acceptor concentration

10. Solution These 3 equations are solved simultaneously over a user defined 1-D grid Diffusivity is calculated using: where the values of D 0 and E a 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)

11. Example go ssuprem3 TitlePre-deposition of Boron CommentInitialize the silicon substrate Initialize Silicon Phosphor Concentration=1e16 CommentDiffuse boron DiffusionTime=15 Temperature=850 Boron Solidsol PrintLayers Concentration Phosphorus Boron Net TonyPlot-ttitle “Boron Predep” Structureoutfile=predep.str StopEnd example

12. Pre-Deposition Example

13. Outline Introduction Introduction Diffusion Simulation Diffusion Simulation  Oxidation Simulation Ion Implant Simulation Ion Implant Simulation

14. 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

15. Outline Introduction Introduction Diffusion Simulation Diffusion Simulation Oxidation Simulation Oxidation Simulation  Ion Implant Simulation

16. Ion Implantation SUPREM can calculate ion implant profiles Simulated impurities can be implanted, activated, and diffused SUPREM contains data for the implant parameters (R p 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: ImplantArsenic Energy=60 Dose=5e15