Interferometry: a direct die level characterization technique

This paper studies the measurement capabilities of interferometric microscopy post CMP processes at die level (≈ 1cm(exp 2)). Such metrology is presently missing in the semiconductor industry. The study addresses different problems linked to interferometric imaging at die’s scale, as wafer signature, stitching or accuracy. Methodology is proposed, detailed and discussed. The impact of stage’s vacuum is observed and quantified. Choice of cylinder and tilt levelling is justified; stitching effects are also investigated. To finalise local and global correlations with reference techniques are performed. Keywords: Chemical Mechanical Planarization, Interferometry, Characterization, Die-level, Intra die-level