Nanometric lateral standards are essential to nanometrology. Using laser-focused atomic deposition, a one-dimensional (1D) grating has been manufactured. The pitch of the grating is 212.8 nm, which can be traced to the laser wavelength that is accurately locked to the 52Cr atomic resonance transition <sup>7</sup>S<sub>3</sub> →<sup>7</sup>P<sub>4</sub><sup>0</sup>. In this paper, the uniformity rather than the pitch accuracy of the 1D grating was evaluated using atomic force microscope (AFM). Based on the center-of-gravity method, the average pitch and the nonuniformity of the grating pitch were calculated. The results show that the average pitch of the grating is 213.2 nm which deviates from the design pitch due to the calibration of AFM, and the nonuniformity of the grating is 0.1 nm. The results preliminarily prove that 1D grating fabricated by laser-focused atomic deposition has good uniformity, and has great potential to become nanometric reference material for AFM and scanning electron microscope (SEM) calibration.
One-dimensional multilayer gratings were prepared by four steps. A periodic Si/SiO<sub>2</sub> multilayer was firstly deposited on Si substrate using a magnetron sputtering coating process. Then, the multilayer was been bonded and split into small pieces by diamond wire cutting. The side-wall of the cut sample was subsequently grinded and polished until the surface roughness was less than 1nm. Finally, the SiO<sub>2</sub> layers were selective etched using hydrofluoric acid to form the grating structure. In the above steps, special attentions were given to optimize the etching processes to achieve a uniform and smooth grating pattern. Transmission electron microscope (TEM) was used to characterize the multilayer gratings. The pitch size of the grating was evaluated by an offline image analysis algorithm and optimized processes are discussed.
Atom lithography is a novel technique for nanofabrication which can be used to grow periodic arrays of highly uniform nanometer-scale structures. The pitch standard of Cr nano-grating is 212.8±0.1 nm, which coincides with λ/2 of the standing wave, in correspondence with the <sup>52</sup>Cr atomic resonance transition: <sup>7</sup>S<sub>3</sub> → <sup>7</sup>P<sub>4</sub><sup>0</sup>, λ= 425.55 nm. With the utilization of the material removal ability by AFM scratching, the Cr nanostructures have been transferred to an InP substrate for replication and subdivision. The uncertainty analysed based on gravity centre (GC) method is better than 0.5% for both replicated and subdivided nano-gratings. AFM lithography method expands the application of atom lithography in metrology to a smaller scale with high precision.