Monitoring the reduction in thickness as material is removed from a wafer composite and test structure for monitoring removal of material

Abstract

The aim of the invention is to create a simple monitoring or testing method for monitoring a reduction in thickness as material is removed from a bonded semiconductor wafer pair, which prevents failure effects as material is removed from wafers (polishing, grinding or lapping). In addition, the costs of the material removal process should be reduced by minimizing the complexity of monitoring, as well as by reducing the amount of resulting refuse. To this end, the invention provides a test structure (4, 5, 6, 7, 8, 9) comprised of a systematic row of a number of different depth trenches that are made in the (active) wafer (2). A thickness (h6; h7) of the active wafer (2) desired during material removal, particularly during a polishing, corresponds to the depth (t6; t7) of a reference trench (6; 7) of the trenches of the test structure, said reference trench (6) being surrounded by flatter and deeper trenches (5, 7). The active wafer (2), via the side (2a) on which the test structure was provided, is bonded to the second wafer of the semiconductor wafer pair provided as a supporting wafer (1). A removal of material, particularly a polishing, is effected on the rear (2b) of the active wafer (2) until the reference trench (6) is exposed. The result is visually observed (30) in order to monitor the reduction in thickness as material is removed from the first wafer (2).

Dependencies are inferred from the claim text.