Directly measuring the topography
of bits on DVD masters and replicas with an Atomic Force Microscope
(AFM) is useful for quality control and process development. Parameters
that are routinely measured with an AFM include:
- Track Pitch
- Bit Width - Top and bottom
- Bit Length - Top and bottom
- Bit Angle - All sides
- Bit Height
Additionally, an AFM is very helpful
for visualizing defects on the surface of masters and discs.
Figure 1 shows a three dimensional image of a stamper surface.
The scan range is 10 x 10 microns and the maximum Z range is 192 nanometers.
Figure 1. Three dimensional image of a stamper surface.
A 2-D image of the DVD stamper in figure 2 shows the alignment
of bits. Any defects on the surface are readily identified in 2-D images.
Figure 2. 2-D image of the DVD stamper showing the alignment
Line profile of the stamper surface is given in Figure 3. It shows the measure
of the bit width at the bottom, .535 µm, and at the top, .238 µm,
of the bit. From similar profile analysis it other parameters such as the pitch
and bit height are measured.
Figure 3. Line profile of the stamper surface showing
the measure of the bit width at the bottom, .535 µm, and at the top, .238
µm, of the bit.
The following information was supplied by Pacific Nanotechnology