Double Patterning Lithography (DPL) for next generation wafer exposure is placing greater demands on the
requirements for pattern placement accuracy on photomasks. Recent studies have shown that pattern placement accuracy
can be one of the largest components of systematic wafer overlay error. Since LELE or LFLE DPL technologies tighten
intra-field-wafer overlay requirements by as much as a factor of 2 (to 2 - 3nm for critical layers), minimizing all sources
of systematic overlay error has become critical. In addition to its impact on overlay performance, any significant pattern
displacement between the two exposures in a double patterning scheme will have a significant impact on CD uniformity,
another major area of concern for next-generation devices.
In the past, mask registration has been referenced to design data using relatively large, specially designed targets.
However, as shown in many previous papers , the true registration error of a next-generation reticle cannot be
sufficiently described by using today's sampling plans. In order to address this issue, it is mandatory to have In-Die
registration capability for next generation reticle registration. On this path to In-Die pattern placement metrology many
challenges have to be solved. One is the data preparation necessary to get the targets placed and marked within the
design, preparing for the later metrology step.
This paper demonstrates an automated way of performing In-Die registration metrology. This new approach allows more
flexible and higher density metrology so that pattern placement error is sufficiently well characterized.