1. Silicon Etch Product Transport by an Inductively Coupled Plasma in Cl2
SFR Workshop
May 24, 2001
Mark Kiehlbauch, David Graves, Mark Nierode
Berkeley, CA
2001 GOAL: Demonstrate effects of coupled plasma and neutral models on etch product redeposition by 9/30/2001.
5/24/2001

2. Etch Products in Plasma: CD Effects
Example: Silicon Etching with Cl2
Neutral transport and redeposition plays a key role in etch performance.
Redeposition of silicon from gas phase on wafer can lead to loss of CD control.
Deposition of silicon onto reactor wall requires expensive cleans.
Vahedi et.al., 1999 Dry Process Symposium, Tokyo
5/24/2001

3. The Silicon Lifecycle During Etching
1) SiClx is etched from wafer.
2) SiClx is:
ionized/dissociated to
depositing species
3) Depositing species:
go to walls
redeposit on wafer
removed by pumping
4) SiClx is etched from walls.
5/24/2001

4. Role of Gas Inlet Position on Etch Product Redeposition
Examine effect of inlet position and flow rate: showerhead vs. center inlet
5/24/2001

5. Silicon Redeposition on Wafer
Inlet position changes the magnitude and profile of redeposition
on wafer
Si Redep. (Å/min.)
500 sccm
R (cm)
5/24/2001

6. SiCl2 Transport & Inlet Position
Showerhead Inlet SiCl2 Flux
Center Inlet SiCl2 Flux
Inlet
Inlet
Outlet
Outlet
Vspec = Vtot + Vspec,dif
Vtot
Species
Mole Fraction
500 sccm
Vspec,dif
Vspec
5/24/2001

7. Convective Neutral Transport
Center Inlet Overall Neutral Flux
Showerhead Inlet Overall Neutral Flux
Inlet
Inlet
Outlet
Outlet
Overall flow driven by ÑP = f(inlet/outlet position, reactor aspect ratio) and coupling with plasma.
500 sccm
5/24/2001

8. SiCl2 Diffusive Transport
Showerhead Inlet SiCl2 Diffusive Flux
Center Inlet SiCl2 Diffusive Flux
Inlet
Inlet
Outlet
Outlet
SiCl2 diffuses towards inlet and plasma (sinks) and away from wafer and walls (sources).
500 sccm
5/24/2001

9. 2002 and 2003 Goals
Convert plasma/neutral code to FEMLAB/MATLAB platform for ease of use and code transferability. Include self-consistent electron kinetics in model, by 9/30/2002.
Compare plasma/neutral model to test-bed experimental system: role of etch products in etching, by 9/30/2003.
5/24/2001