Varvara Brackmann, Malte Neul, Michael Friedrich, Wolfram Langheinrich, Maik Simon, Pascal Muster, Sebastian Pregl, Arne Demmler, Norbert Hanisch, Maximilian Lederer, Katrin Zimmermann, Jan Klos, Felix Reichmann, Yuji Yamamoto, Marcus Wislicenus, Claus Dahl, Lars Schreiber, Hendrik Bluhm, Benjamin Lilienthal-Uhlig
Universal quantum computers promise the possibility of solving certain computational problems significantly faster than classically possible. For relevant problems, millions of qubits are needed, which is only feasible with industrial production methods. This study presents an electron beam patterning process of gate electrodes for Si/SiGe electron spin qubits, which is compatible with modern CMOS semiconductor manufacturing. Using a pCAR e-beam resist, a process window is determined in which structure sizes of 50 nm line and 30 nm space can be reproducibly fabricated with reasonable throughput. Based on electrostatic simulations, we implemented a feedback loop to investigate the functionality of the gate electrode geometry under fabrication-induced variations.
KEYWORDS: Point spread functions, Scattering, Scanning electron microscopy, Tolerancing, Critical dimension metrology, Calibration, Electron beam lithography, Electron beams
The result of electron beam lithography is influenced by many effects: forward and backward scattering, formation of secondary electrons, re-scattering of electrons, chemicals diffusion in the resist material, wafer stack, etc. To achieve high resolution all these effects should be taken into account. Commonly, the electron energy distribution in the exposed matter is described by the Point Spread Function (PSF). This is a simple approach which takes into account large portion of phenomena using few parameters. PSF function is a Gauss or multiple Gauss function, which is determined experimentally by the calibration procedure. Each resist material with corresponding stack is characterised by its own PSF, in case of double Gaussian, with the following parameters: α, β and η. In the current work the PSF parameters were systematically varied to study their influence on the dose assignment and resulting pattern. This gives a broader understanding of the correction mechanism using PSF. Furthermore, the resulting shape of the structure is influenced not only by the PSF parameters and dose assignment, but by the fracturing type as well. All these effects were studied using experimental and simulation approaches.
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