Cantilever Preparation
Silicon Cantilever Substrates
Rev. B
MultiMode SPM Instruction Manual
59
4.1.1 Tip Shape of Etched Silicon Probes
Etched silicon probes provide the highest aspect ratio and most consistent tip sharpness of the
probes supplied at present. There are some subtleties in general shape that should be understood to
gain the best advantage from the etched silicon tips when imaging samples with steep walls over
steps of 100nm to several microns in height.
Figure 4.1b
Silicon Cantilever—Theoretical Tip Shape
The present process creates a tip which has symmetry from side to side with a 17+ 2° half cone
angle (refer to top of
). Front-to-back, along the length of the lever, the tip is asymmetric
(refer to lower-right of
). Another factor affecting the interaction of the tip shape with
the surface is the substrate mounting angle. Along the front edge of the tip, the half angle is
nominally 25°, and at the back edge of the tip the half angle is approximately 10°, with both of
these numbers not accounting for the tilt of the substrate. With the mounting angle of the substrate
taken into account, the front is 35° and the back is zero degrees. From the tip side, the cross-section
of the tip near the lever is approximated by an inverted “kite” shape. All of these subtleties arise
from the etching process used to make the tip, which employs caustic solutions to perform wet
anisotropic etching of the silicon.
17.0°
17.0°
T
IP
Cantilever
25.0°
10.0°
