Benefit of precise control of surface reaction by new patterning technique for small-contact etching with TiN hard mask

We introduce state-of-the art small-contact etching by a new patterning technique using atomic layer etching (ALE) for sub-5 nm technology generation. In small-contact etching, SiO2 is etched by using a TiN hard mask with the progress of the miniaturization process. However, when applying the conventional method to small-contact etching with a TiN mask, etch stop is caused by excess deposition on the SiO2 film. From the results of surface analysis by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy–energy-dispersive X-ray spectroscopy (TEM–EDX), it is considered that the deposition is formed by the reaction of fluorocarbon (FC) plasma and TiN. To solve this problem, we have developed a quasi-ALE technique to improve the ALE process to make it more suitable for SiO2 etching. By adopting this technique to small-contact etching with a TiN hard mask, etch stop was significantly reduced. Quasi-ALE precisely controls the surface reaction by controlling the radical flux and ion flux independently. Therefore, the reaction of FC plasma and TiN leading to etch stop can be minimized. Quasi-ALE can resolve the etch-stop issue due to the TiN mask used in the conventional method.