M-S specification binning based on digitally coded indirect measurements

Binning of IC circuits after volume fabrication is widely used to separate tested circuits in different classes depending on different degrees of specifications compliance. When the specifications are directly measured, the boundaries of the classes are usually linear functions in the specification space. For alternate testing strategies the indirect measures generate more complicated regions in the measure space due to the non linear mapping between the specification space and the measure space. The binning strategy proposed in this paper works with the same efficiency regardless of the shape of the boundaries of each binning region. A digital encoding of the measure space using octrees is the key idea of the proposal. The strategy has two phases: (1) The training to generate the digital codes for the binning subsets and (2) the actual production binning of the fabricated ICs. The first phase is performed only once and requires sufficient samples of each binning class to generate the octree under realistic variations. The second phase is fast and requires only to evaluate the octree using the measures of the tested IC. In order to illustrate the proposal, the method has been applied to a Biquad filter considering three specification bins as a proof of concept. Successful simulation results are reported showing considerable advantages in terms of binning speed. In addition, the method has been compared to a SVM classifier revealing substantial benefits.