CONTROL OF PVD TIN THICKNESS MEASUREMENTS

TiN is widely used as a diffusion barrier layer. Uniformity of the thi ckness and composition of this layer is dependent on the deposition co nditions and is important for production yield. This uniformity is rou tinely derived from the sheet resistance measurements. Due to the corr elation between composition and thickness in resistivity measurements, thus derived thickness can be incorrect. Use of the multiple angles o f incidence (MAI) ellipsometry with a blue Ar+ laser (458 nm) allows t o decouple thickness and composition effects and ensures accurate meas urements over 1000 Angstrom for TiNx (x greater than or equal to 1.1). Comparison of the MAI ellipsometry, spectroscopic ellipsometry (SE), profilometry and resistivity measurements of TiN layer on a specially prepared wafers confirms reliability and accuracy of the MAI ellipsome try measurement. Tracking of the composition and thickness variation o f the TiN across the wafers with the MAI ellipsometry is found consist ent with the SE and profilometry measurements.