專利摘要：
A method of forming a pattern with high aspect ratio on a polycrystalline aluminum nitride substrate comprises the steps of (A) providing an aluminum nitride substrate and forming a barrier layer on the aluminum nitride substrate; (B) etching the barrier layer with an energy beam to form at least one recess in the barrier layer; (C) plasma etching the substrate to deepen the recess into the aluminum nitride substrate; (D) removing the barrier layer to obtain the aluminum nitride substrate having at least one pattern with high aspect ratio. The method uses the energy beam to directly form a pattern on the barrier layer, and further employs plasma etching to prepare the aluminum nitride substrate having a pattern with high aspect ratio quickly and effectively.