AFM Lithography Instrumentation
Any atomic force microscope can be used for creating nanometer-sized patterns on a surface. However, the quality and complexity of the patterns depends on specific scanning probe hardware and software. The method of patterning is determined by the types of probes, substrates, and the specific software performance capabilities used to drive the scanning probe tool.
Hardware: The most critical hardware feature that is required is an X-Y
calibration system. Because the piezoelectric ceramics used in AFM have
unwanted characteristics such as creep and hysteresis, calibration sensors
are necessary to guide the motion of the probe. Without the calibration
sensors, the probe moves in an unpredictable motion, and it is hard to write
complex patterns. As an example, in figure 5 the AFM did not have calibration
sensors, and the lines at the upper right of the pattern did not connect as
intended. Conversely, Figure 6 is an illustration of a complex pattern drawn
with the DPN™ process. Because the instrumentation had X-Y calibration
sensors, a higher quality pattern was possible.
Figure 6: Lateral Force Microscope (LFM) images of patterns created
using DPN™. With X-Y calibration sensors the lines at the edges
of the boxes intersect as expected. Image written with a NanoInk DPN
Writer™ using PNI scanner technology. Line widths vary from
60 nm - 100 nm.
Software: Software is used for defining the pattern that will be drawn with
an AFM and then for drawing the pattern on a materials surface. Figure 7
shows a control window that may be used for creating patterns with an AFM.
The pattern may be drawn on a section of the screen as a combination of
dots and lines or it may be imported from a bit-map file. The software
allows writing of the patterns by applying a specific force or a specified
voltage. Also, the rate of scanning can be specified.
Figure 7: A typical control window for modifying surfaces with an AFM.
Each of the buttons has a drop down menu that facilitates selection
of parameters.
Advanced DPN™ patterning involves the overlay of complex pattern
layers with the precise deposition of molecules, and this process requires
more complex instrumentation. NanoInk has developed a dedicated DPN™
Writer tool called NSCRIPTOR™. Built upon advanced PNI scanner
technology, NSCRIPTOR™ offers a sophisticated, user-friendly DPN™ experience with integrated environmental control.
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