Correlation between inversion layer mobility and surface roughness measured by AFM

The correlation between inversion layer mobility of MOSFET's and surface micro-roughness of the channel has been studied using split CV measurements and AFM analysis, The mobility at high normal field decreases with increasing the surface roughness over a wide range of roughness from 0.3 nm to 4.3 nm (RMS). The trend is the same even for very thin gate oxides down to 3 mn. Careful AFM measurements are used to show that the gate oxide thickness doesn't affect the surface roughness, supporting the independence of mobility on the gate oxide thickness.