**5. Conclusion**

This chapter is focused on the study of the Scanning Probe Lithography in a controlled way on various substrates. The load force produced by silicon nitride (NSG11) tip with average spring constant is sufficient to deform and make scratch on the PMMA thin film. The analysis of the roughness of the surface shows that the concept using a thin insulting film of PMMA on silicon and glass surfaces as a scratching mask can be successfully performed for nanopatterning. Drawing patterns are being controlled by the necessary parameters such as normal force, scanning velocity, time of applying pressure and number of scratching cycle. It is shown that the depth of the lithography mark increases linearly with the increase of the applied normal force. The uniformity of scratches on the PMMA coated on silicon and glass is comparable.

The load force applied by NSG11 tip is not sufficient to exert scratch on the hard surface and is disabled to perform any changes, so diamond tip with much higher spring constant is required. It must be mentioned that the minimum necessary force to modify the PE surface is about 4 N that can be achieved by NSG11 tip and with maximum force load. Therefore, for investigation of the effect of higher forces, DCP20 tip is used for PE substrate. The experimental results show that depth of the lithography pattern increased with the increase of the applied normal force with a linear trend for all of the applied substrates. The increase of applied normal force caused accumulating of material at the start and end point of the grooves. This deformity occurred because of cantilever bending at the start point of the tip moving through the surface.

It is presented that the increase of the scanning velocity induces a decrease in the scratch depth. Thus, slower scans seem to generate higher pressure and as a result, deeper scratch pattern are obtained. However, it could not be determined whether the depth decreases linearly or exponentially with the increase of the scanning velocity.

The increase of the lithography depth with the loading time suggests that the plastic deformation on PMMA layer is time dependent. However, the results show that the dependence of depth to the loading time is not quite linear. By the tip-induced stress, dilation changes such as defects created or absorbed near the vicinity of the deformed region on the surface might occur, which would lead to an additional plastic deformation of the film.

It is shown that the depth of the lithography mark increases with the increase of the number of scratching cycle. The depths of scratches increase linearly with the number of scratching cycle. Finally, due to the convolution effect of the tip and substrate topography, the scratch depth may appear smaller by AFM imaging than their actual size.
