Synthesis of Cubic Boron Nitride Thin Films by Low-Energy Ion Beam Assisted Deposition by Applying Substrate Bias

摘要

Cubic boron nitride (c-BN) films are synthesizedwith low-energy ions of 100eV from a gridless ion gun byapplying negative substrate bias. Boron is evaporated by anelectron beam at rates of 0.8 to 2.3A/sec onto silicon substrate.Substrate temperature and bias are varied from 400 to 800℃ andfrom 0 to -700Y respectively. Due to the low-operating pressureof the ion beam assisted deposition (IBAD) process, applyingsubstrate bias efficiently accelerates ions enough for synthesis ofthe c-BN phase. With increasing substrate bias, the major phasechanges in the sequence of hexagonal boron nitride (h-BN) to c-BN to h-BN. The reappearance of the hexagonal phase at high biasvoltage is thought to be due to the stress annealing effect.Intermediate temperatures have produced higher c-BN contents.Far-off stoichiometric film (NIB=0.72) consists of h-BN phaseeven under the c-BN parameter but a little off stoichiometry hasled to higher c-BN contents. The maximum contents of c-BNphase is about 70%. DC type bias and oxygen/hydrogenincorporation into the films are presumed to limit the content. TheIBAD process with proper substrate bias is promising for largeareas of and high rate growth of the c-BN phase.