Plasma‐deposited amorphous carbon films as planarization layers

A dry planarization process has been developed that utilizes plasma‐enhanced chemical vapor deposition of amorphous carbon films. The characteristics of the films depend on deposition conditions such as source gas composition, rf power, degree of ion bombardment, temperature, pressure, and electrode spacing. Planar films were deposited at low temperatures (< 50 °C) with low ion bombardment energy (< 10 V) and high deposition rates (100–300 nm/min). These conditions are desirable for ultra‐large‐scale integrated circuits fabrication, in which the thermal budget and damage must be minimized while maintaining a high throughput. A high degree of planarization over long distances was obtained. By using 2.5‐μm‐thick carbon films, the height of 1.5 μm steps was reduced to less than 0.2 μm for 400‐μm‐wide trenches, providing better than 85% planarization. The planar films have low viscosity and molecular weight, and their molecular structure is similar to that of the source gas. A post‐deposition hardening step was utilized to improve the compatibility of the films with subsequent processing steps. Submicrometer features were patterned in bilayer resists consisting of these planarization layers in combination with either wet‐ or dry‐deposited inorganic imaging layers.