Most new nanolithography techniques are demonstrated over very mall working areas. An important milestone was reached at the TU Ilmenau with the development of a 4-inch nanofabrication and nanomeasuring machine, which is equipped with a special SPL/AFM head. The advanced interferometric air-bearing stage allows an exorbitant resolution of 20 picometres within the full range of 4 inch. A very high structuring accuracy is achieved. The tip-based lithography process based on Fowler-Nordheim electron field emission results in immediate patterning with very small line widths. In the paper, the exceptionally high measurement and fabrication accuracy will be comprehensively presented and discussed.
The use of molecular resist in scanning proximal probe lithography (SPPL) offers a novel and promising maskless lithographic method with sub-10 nm resolution. Here, the authors present their investigation of the patterning capabilities of C-Methylcalix[4]resorcinarene at ambient conditions using SPPL. The STM-based setup operates in constant-current Fowler–Nordheim regime and results in positive-tone self-developing phenomena. The lithographic operation is performed at currents in the range of pico-ampere, writing speeds of 1–10 μm/s, and bias voltages ranging from 20 up to 70 V. Currently, the authors have achieved feature sizes from 7 nm to micrometers depending on the applied exposure parameters. The direct patterning process shows high reproducibility and reliability over this large feature range.
An Atomic Force Microscope (AFM) is a powerful and versatile tool for nanoscale surface studies to capture 3D topography images of samples. However, due to their limited imaging throughput, AFMs have not been widely adopted for large-scale inspection purposes. Researchers have developed high-speed AFM systems to record dynamic process videos in chemical and biological reactions at tens of frames per second, at the cost of a small imaging area of up to several square micrometers. In contrast, inspecting large-scale nanofabricated structures, such as semiconductor wafers, requires nanoscale spatial resolution imaging of a static sample over hundreds of square centimeters with high productivity. Conventional AFMs use a single passive cantilever probe with an optical beam deflection system, which can only collect one pixel at a time during AFM imaging, resulting in low imaging throughput. This work utilizes an array of active cantilevers with embedded piezoresistive sensors and thermomechanical actuators, which allows simultaneous multi-cantilever operation in parallel operation for increased imaging throughput. When combined with large-range nano-positioners and proper control algorithms, each cantilever can be individually controlled to capture multiple AFM images. With data-driven post-processing algorithms, the images can be stitched together, and defect detection can be performed by comparing them to the desired geometry. This paper introduces principles of the custom AFM using the active cantilever arrays, followed by a discussion on practical experiment considerations for inspection applications. Selected example images of silicon calibration grating, highly-oriented pyrolytic graphite, and extreme ultraviolet lithography masks are captured using an array of four active cantilevers ("Quattro") with a 125 µm tip separation distance. With more engineering integration, this high-throughput, large-scale imaging tool can provide 3D metrological data for extreme ultraviolet (EUV) masks, chemical mechanical planarization (CMP) inspection, failure analysis, displays, thin-film step measurements, roughness measurement dies, and laser-engraved dry gas seal grooves.
