Biomedical Engineering Reference
In-Depth Information
250 nm
192 nm
134 nm
78 nm
18 nm
0
µ
m
65
µ
m
0
µ
m
65
µ
m0
µ
m
20
µ
m
Fig. 7.32. Optical and video products: on the left is an image of an LCD screen, where the step
height is characterized with a line profile. On the right is a micro-lens array, consisting of a surface
on which a series of
ca
.7
m lenses are manufactured. Dimensions, shape and roughness of these
lenses are important parameters that the AFM can provide.
three-dimensional nature of AFM images can give a better idea of the shape of MEMS
devices.
7.4.2.4 Optical products
Optical components can be somewhat less demanding than semiconductors, but still
require very low manufacturing tolerances, and AFM can be useful to characterize several
high-technology optical products. LCD screens are created by patterning a glass surface
with several layers of thin films. The AFM is an excellent tool for measuring the thickness
of the thin films on the surface of the glass. In the example in Figure 7.32, an image of an
LCD screen is shown, with a critical measurement on a thin film step. The step height at
the left is 30 nm, and the step at the right is 73 nm.
Optical components are required for many high-technology products such as optical
storage device lenses, digital cameras, and fibre optics required for telecommunications.
The AFM is an excellent method for imaging optical components. These components are
often quite large, but measurement of these components is not possible with an optical
profiler because the devices are transparent. A mechanical profiler cannot be used because
it would potentially scratch their surfaces. The example in Figure 7.32 shows a micro-lens
array comprising a series of microscopic lenses fabricated onto a surface. Each lens is
approximately 7 microns across. The AFM is capable of precisely measuring the dimen-
sions of each of the lenses, as well as the surface roughness of the lenses. Any anisotropy
in the lenses will cause unwanted distortion in the devices that the lenses are used in.
