Results of Design of Experiments optimization of magnetic stack etching
Process parameters for the acceptance test
To find the optimal parameters, Design of Experiments was applied, with the intervals shown on the figure below.
Parameter
Ti etch acceptance
DoE
Neutalizer current [mA]
450
Design of Experiments setup used to find optimal etch of the multi layers stack. Centerpoints are not shown on the figure. The parameters varied were Beam current, Beam Voltage, Accelerator Voltage, and Incident Angle.
RF Power [W]
800
Beam current [mA]
400
Beam voltage [V]
500
Beam accelerator voltage
500
Ar flow to neutralizer [sccm]
5.0
Ar flow to beam [sccm]
10.0
Rotation speed [rpm]
20
Stage angle [degrees]
5
Helium backside cooling [Torr]
37.5
Some SEM profile images of the etched stacks
Magnetic stack of Ta/MnIr/NiFe/Ta/Tao/Ta/MnIr/NiFe/Ta etched with the optimal parameters shown above. Redeposition of etched material at photo resist. Profile ~78°
Etched magnetic stack with poor structure transfer, the parameters chosen was clearly not optimal. Chosen etch parameters result in severe footing
Etched magnetic stack with poor structure transfer, the parameters chosen was clearly not optimal. Chosen etch parameters result in severe trenching
Endpoint detection with SIMS
The endpoint for etching is determined by the integrated SIMS
End point detection is achieved by SIMS, and the etch rate is approximately 25 Nm/min.
Resist stripping can be hard due to burned resist, to remedy this try to lover the current. Changing the currect will chance the sidewall angle and new studies of etch profiles will be necessary. For help, discussion and further info please contact Kristian Hagsted Rasmussen.
