Write-Read AlignmentΒΆ
see also CLL Offsets tab
The thermal expansion of the cantilever when the writer is switched on, and delays in the electronics cause a shift between the expected position of a written pixel and its position in the read image. Uncompensated shifts between the write and read positions reduces the overlay accuracy and confuses the depth feedback. During writing, the user can detect any residual shift using the line analysis tool (see Figure 17). After patterning, the offsets can be automatically detected by the NanoFrazor’s software.

Figure 17 The line analysis tool provides a plot with a comparison between the measured line profile (in green) and the target line profile (in blue).
In the example shown in Figure 17 the NanoFrazor was writing a vertical trench or groove with a single non-zero depth level at a target depth of 15 nm. The line analysis tool shows a shift of 60 nm between the groove’s position in the measured depth (green line) and its position in the target depth (blue line). This offset would result in an overlay error. Additionally, because of this shift, the depth measured in the Depth Feedback region (light blue area) is not the depth of the written groove, but the depth of an unwritten area. This depth is lower than the target depth, and so the feedback increases the write force even though the groove’s depth is already higher than the target depth.
Figure 18 shows the result of repeating the write process following the correction of the CLL offsets. The line analysis tool shows that the groove has been written in the correct position. As a result, the feedback is now fed with correct written depths and so it is able to adjust the force to achieve the target depth of 15 nm.