NANO5-2D Grating-Final report

This report is prepared for the Discussion Group 7 (DG7) for Nanometrology under the Consultative Committee for Length's Working Group on Dimensional Metrology (CCL-WGDM). It describes the comparison of calibration results of the pitch in the x and y directions and the angle of two two-dimensional gratings. The nominal values of the pitches are 300 nm and 1000 nm and the nominal angle is 90 degrees. The standards were circulated between 12 national metrological institutes. The measurement methods were optical diffraction (OD) and scanning probe microscopy (SPM). The reported uncertainty for the pitch was in the range from 0.0031 nm (OD) to 3.1 nm and for the angle in the range from 0.0012 degrees (OD) to 1.2 degrees. Out of the 112 measurement results for the six measurands, 17 results have either been removed from the calculation of the reference value-due to errors acknowledged by the lab- or have been omitted as the E-n values were larger than one. Ten of the results have E-n values larger than one; six results have E-n values larger than two. However, the participating labs have identified errors and submitted a total of 15 corrected measurement values to be considered for inclusion in the calculation of the reference value. In the end only four results remain with an unexplained E-n value larger than one, ranging between 1.4 and 2.1. Acknowledging the errors found by the labs in this comparison, the measurement of pitch and angle are generally consistent and reliable to a very high accuracy.