TiN and TaN cointegration for 300 mm superconducting back end of line

The development of new quantum technologies based on superconducting qubits or spin qubits becomes a major subject of interest for applications in communication and data computing. Such technology operating at low temperature requires a superconducting rooting development. The superconducting materials were selected based on their superconducting properties and their integration capabilities in an industrial process flow. Their integration is based on the French Alternative Energies and Atomic Energy Commission patent No. FR2112216 and consist in a direct etching approach by patterning both metals successively with a selective etch process to define lines and vias. To obtain a critical temperature higher than 1 K, the nitrogen flow during TaN deposition and the TiN thickness are optimized. To develop the patterning process, 40 nm thick films of TiN or TaN are deposited by physical vapor deposition on a SiO2 layer over 300 mm silicon wafers. Then, the lithography process is performed on a 193 nm stepper to achieve a 150 nm line via critical dimension (CD). Etching developments are carried out on a 300 mm industrial ICP chamber using Cl2 based chemistry with or without HBr or CH4 addition. With Cl2/CH4 chemistry, we achieved straight profiles, controlled critical dimensions, and mitigated micromasking issues. This approach also addressed selectivity challenges, ultimately enabling reliable patterning for TiN and TaN superconducting lines and vias. The patterning of 80 nm TiN vias is obtained by combining resist trimming and the etching processes previously optimized for the narrow lines. After this patterning process optimization, the Tc of 150 nm CD structures is measured using a specific test vehicle for both TiN and TaN thin films.