Fabrication and evaluation of diamond-tip chips for scanning probe microscopy

Scanning probe microscopy (SPM) is a powerful technique for characterizing materials and devices at the nanometre scale, but the measurement quality depends directly on the SPM tip. Blunt, irregular, or multi-contact tips produce convolution artefacts that reduce accuracy and require frequent replacement. Depending on the instrument, operating mode, and experimental environment, changing a tip can take from ten minutes to several hours. Extensive research has therefore focused on innovative solutions, with reverse tip sample (RTS) SPM, developed at imec, emerging as a particularly promising approach.

In RTS SPM, the sample is placed on a tipless cantilever and is scanned over a tip integrated into the RTS tip chip, which contains thousands of such tips. This configuration allows for tip exchanges within a few seconds, a dramatic improvement compared to traditional SPM, simply by repositioning the sample above any adjacent, unused tip. In just a few years, the RTS technology has further advanced and several RTS tip chip prototypes tailored for different applications have been demonstrated. These include chips equipped with bare silicon tips for topographical mapping, platinum coated tips for electrical SPM, and conductive diamond tip variants designed for high-force electrical measurements.

This project aims to improve the reproducibility and yield of an existing dry-etching process for silicon tip structures by transferring it from an older research etching tool to a newer, more advanced etching reactor. Key target parameters are a silicon tip height of 8–12 µm, a tip-on-pedestal geometry, and a tip radius of 10–50 nm. The fabricated silicon tips will be coated with thin diamond films and further patterned by dry etching. The project will also establish rigorous, efficient characterization methods to enable rapid feedback and continuous process improvement. The student will perform lithography, etching, and deposition in imec’s state-of-the-art cleanroom, evaluate tip performance in a well-equipped SPM laboratory, and summarize the results in a scientific publication.