Sub-50-nm isolated line and trench width artifacts for CD metrology

SI-traceable critical dimension 3DAFM was used to characterize 25 nm NanoCD linewidth standard. The standard has a uniquely low linewidth roughness (LWR) and can be used as a benchmark during development of advanced patterning technologies. The following results were obtained: (a) Mean LWR for two 25 nm standards with uncertainty ±0.02 nm (0.95 CL). The LWR is below 0.7 nm (1s). (b) Distribution of LWR and linewidth (LW) at 3 line heights (20, 50 and 80% from the line top) along 3 mm segment of the standards. Variations are below 0.25 nm and 0.07 nm (1s) for LW and LWR, respectively. (c) Spatial power spectra of LWR of the standards. The NanoCD spectrum resembles reported earlier spectra of polycrystalline Si.

“…Detailed description of the sample can be found elsewhere [3]. The NanoCD standard NCD12-25XY has two samples placed horizontally (with notch down) and vertically.…”

Section: Experimental Setup and Methodologymentioning

confidence: 99%

SI-traceable calibration of line-width roughness of 25nm NanoCD standard

Ukraintsev¹,

Helvey

Guan

et al. 2010

“…Every wafer is pre-measured at least three times using CD AFM calibrated with a 70 nm VLSI NanoCD standard [9]. For the majority of the applications, precision of the CD AFM for lateral and vertical CD's is 1.5 nm (3σ).…”

Section: Methodsmentioning

confidence: 99%

“…Lot average OS measurements were correlated to the baseline metrologies (Figures 8,9,10). The data shows linearity problems for line CD.…”

Section: Sti Post Etching Patternmentioning

confidence: 99%

A comprehensive test of optical scatterometry readiness for 65-nm technology production

Ukraintsev

2006

Measurement bias is a central concept of critical dimension (CD) metrology. Bias is a complex function of sample, tool and time. Bias variation defines the total measurement uncertainty (TMU). TMU is a measure of metrology quality. Precision (or bias variation with time) is only a part of TMU. Often tool-to-tool and sample-to-sample components of bias variation exceed precision. To measure sample-to-sample bias variation, knowledge of the reference CD value for the samples is required. Since bias is sample specific, the technology representative set of calibrated samples has to be created. The described approach has been implemented for a comprehensive evaluation of optical scatterometry (OS) to determine readiness of OS for the 65 nm technology production. The tests covered nine OS applications representative of the technology. The testing revealed that OS metrology is mostly ready to support 65 nm technology production. Both spectral ellipsometry and angular reflectometry OS compete closely on all applications. OS demonstrates acceptable averaged bias for CD and sidewall angle for most applications. Correlation of OS to other metrologies is usually satisfactory. At the same time some problems have been observed. The majority of the tested applications show poor linearity for some measured parameters. Cross-correlation between parameters is usually the cause. OS has trouble to meet the semiconductor industry's tight fleet precision requirements. For all applications, OS tool matching is a major component of fleet precision. The evaluation also exposed some general CD metrology challenges. With accuracy allowance in a sub-nanometer range, it is difficult to find an adequate reference technique to verify and calibrate OS models. Atomic force microscopy (AFM) has been chosen as a reference technique during this evaluation, but it has limitations. Precision, sidewall profile resolution and tip finite dimensions are some of the AFM limitations. OS fleet TMU for many applications is unacceptably high. Further work is needed to better understand the impact of reference data uncertainty on these alarming results. It is clear that to achieve a desired sub-nanometer agreement between reference and OS data, one must pay scrupulous attention to every detail of the experiment.

“…In this paper we present just brief overview of the approach. The methodology consists of XYZ scale calibration using SI-traceable NanoLatice TM (XY) and step height standards (Z) followed by tip width (TW) calibration using SI-traceable NanoCD TM standard(s) by the VLSI Standards, Inc. [21,22,23]. Results of CD AFM MU assessment using three NanoCD TM standards are shown in Figure 5 [24].…”

Section: Afm As Si-traceable Reference Metrologymentioning

confidence: 99%

Dimensional metrology with sub-nanometer uncertainty: unique role of AFM as the reference

Ukraintsev¹,

Foucher

2010

The 2007 edition of ITRS has introduced a new metric for metrology quality assessment -measurement uncertainty (MU). The new metric has precision as one of many uncertainty components. Additional significant components are tool matching, sampling uncertainty and sample-to-sample bias variation. Sample dependent bias variation and, therefore, MU can be measured accurately only if a reference metrology (RM) is employed. RM is a must for achieving and verifying required today sub-nanometer MU of critical dimension (CD) metrology. To insure long-term performance of in-line metrology and reliable process control a simple but efficient way is suggested -employment of in-line RM system. SI-traceable CD AFM with sub-nanometer MU is a proper RM tool for the task.