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A new measurement system analysis (MSA) methodology has been developed at Texas Instruments (TI) to evaluate the
status of the 65 nm technology critical dimension (CD) metrology and its readiness for production. Elements of the
methodology were used in a previously reported scatterometry evaluation [1]. At every critical process level the
precision, bias, linearity and total measurement uncertainty (TMU) were evaluated for metrology fleet over extended
periods of time, and with the technology representative set of samples. The samples with variations that fully covered
and often exceeded process space were pre-calibrated by CD atomic force microscope (AFM). CD AFM measurement
precision was determined for every analyzed process level based on repeated measurements conducted over several
days. The National Institute of Standards and Technologies (NIST) traceable standards were used to verify CD AFM
line CD and scale calibrations. Therefore, for the first time the NIST traceability has been established for CD metrology
at every critical process level for the entire technology. The data indicates an overall healthy status of the 65 nm CD
metrology. Sub-nanometer accuracy has been established for gate CD metrology. The thorough CD metrology
characterization and specifically absolute CD calibration were instrumental in seamless technology transfer from 200
mm to 300 mm fabs. The qualification of CD metrology also revealed several problems. Most of these are well-known
from previous studies and should soon be addressed. CD scanning electron microscopy (SEM) has a systematic problem
with bias of CD measurements. The problem is common for several front-end and back-end of line process levels. For
most process levels, TMU of CD SEM is noticeably affected by sample modification inflicted by electron irradiation
(shrinkage, charging, buildups, etc.). This causes problems, especially in the case of fleet TMU evaluation. An
improved data collection methodology should be devised to minimize the impact of sample modification on fleet TMU
measurements. The reported progress in semiconductor industrial CD metrology became possible after a recent
breakthrough in line CD standard technology [2,3], recognition of CD AFM as an instrument for CD traceability [4,5]
and development of the concept and mathematical tools for TMU analysis [6,7].
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