Adding 3D to conventional SEM or FIB surface imaging information

In situ Surface Sensing and Nanoprofilometry for Focused Electron and Ion Beam Induced Process Verification with the new Raith NanoSense

Nanopatterning processes and corresponding parameters are typically well understood for standard nanofabrication applications using resist-based electron beam lithography (EBL) or FIB milling processes.

However, advanced and innovative nanofabrication applications involving e.g. (3D-) focused electron or ion beam induced deposition/etching processes (FEBIP/FIBIP) or complex FIB patterning tasks on new materials might require challenging and elaborate process verification and optimization–typically in time-consuming iterative cycles. This is due to the fact that the number of variable parameters for such complex processes involving e.g. new gas chemistries or ion species is virtually “infinite”. As SEM imaging only delivers 2D information, AFM or cross-sectioning techniques are typically involved in order to retrieve the required 3D information.

Efficient 3D milling profile visualization

The new Raith NanoSense – available for eLINE Plus and ionLINE – offers a far more efficient and straightforward solution, helping to qualify FEBIP/FIBIP and milling processes in situ within minutes. Nanoprofilometric scans for both additive (deposition) or subtractive (milling/etching) surface treatment yield 3D information for deposition or milling rate determination in a very efficient way – without the need for laborious unloading of the sample and ex situ AFM analysis or use of FIB-SEM technologies.

In order to achieve the expected reliable and reproducible results for 3D nanostructures, NanoSense can be implemented in both eLINE Plus and ionLINE in order to optimize and verify complex nanofabrication tasks. A standard nanomanipulator, available for both systems, can be upgraded with a surface-sensitive sensor yielding height resolutions in the order of 5nm.

Image 1 (a, b) Complex and challenging deposition processes using FEBIP, (c) inhomogeneous milling results applying multipass versus single pass strategies

Image 2 a, b shows the scanning principle and an example of deposition rate determination using height profiles of deposited lines applying electron beam induced deposition.

Image 3 (a) Milling a rectangle with identical milling dose, yet applying different patterning strategies, (b) Corresponding 2D SEM imaging information is not sufficient for qualitative process verification (c) Nanoprofilometric line scans revealing the resulting milling profiles for the respective milling strateg