Cubic boron nitride film synthesis by reactive sputtering with pulsed RF substrate bias

Cubic boron nitride (c-BN) films are synthesized by reactive sputtering wit h RF biased substrate in electron cyclotron resonance (ECR) plasmas. In thi s study, continuous working (CW) and pulsed RF bias modes are applied for d eposition and the results are compared. In the CW mode, c-BN is synthesized above a certain threshold ion energy and this energy changes with the ion to boron-atom flux ratio to the substrate. An experimental study is made in the pulsed bias mode under various conditions: the pulse period and the du ty ratio. As a result in the case of the pulsed bias mode, higher ion energ y is required than that in the CW mode for c-BN synthesis. The boundary bet ween c-BN and h-BN formation regions is found on the diagram expressed as t he threshold ion energy vs. ion to boron atom fluence ratio. Stress measure ment is also carried out for all obtained samples and a strong correlation between the c-BN content and the compressive stress in both substrate bias modes is found. (C) 2001 Elsevier Science B.V. All rights reserved.