Synthesis of cubic boron nitride films using a helicon wave plasma and reduction of compressive stress

Abstract

A high density helicon wave plasma was used to synthesize a thin film of cubic boron nitride (c-BN) on the Si(100) substrate. Borazine (B3N3H6) vapor was directly introduced into the reaction chamber where the plasma density was greater than 10(10)-10(11) cm(-3). The plasma density high enough to dissociate borazine effectively resulted in depositing a relatively good stoichiometric BN film without additional nitrogen sources. The bombardment of energetic ions with a high flux and energy is necessary for the growth of c-BN. The BN him synthesized at the condition of plasma density and rf substrate bias of 8.5 x 10(10) cm(-3) and - 350 V, respectively, was confirmed to be of cubic phase by both the FT-IR and TEM analyses. However, there existed an excessive compressive residual stress of 4-8 G-Pa in the c-BN film, which resulted in poor adhesion. The adhesion of c-BN film was significantly improved without a phase transformation through the post-heat treatment at 800 degrees C in N-2 atmosphere to relax the compressive residual stress.