Multi-Directional Space Tessellation to Improve the Decision Boundary in Indirect Mixed-Signal Testing

One of the most challenging aspects in nowadays microelectronics industry is production test and verification of mixed-signal circuits. In order to cope with some of the drawbacks encountered in this scenario, researchers have found alternate test as a promising solution in achieving such endeavor. This work prospects the possibilities of using space tessellations along multiple directions in order to improve the test decision boundary definition in the alternate measure space. The proposed method is able to reduce false positive test outcomes, i.e. test escapes, with acceptable penalty in test yield loss metric. The key idea presented in this work is to use an ensemble of octrees, each of them tessellating the plane along different directions. Such tessellations create a refinement in the non linear test decision boundaries without the need of including extra circuit samples. The tree ensemble, together with a strict test decision criterion, serve as a classifier during the production testing phase. The proposed multi-directional ensemble tessellation strategy has been applied to test a band-pass Biquad filter affected by parametric variations. The proposed method has reported promising simulation results in lowering the test escapes metric as compared to a single octree classifier. The computational overhead of evaluating several octrees is insignificant since 2n-tree data structures are traversed efficiently. The octree ensemble technique has also been compared against a classic specification guard-banding technique reporting better test yield loss metrics for the same test escape target.