Aspects of BAW filter harmonics wafer level testing

Optimal suppression of spurious spikes in the harmonic response of bulk acoustic wave (BAW) filters is becoming a limiting factor to meet the stringent specification requirements in RF modules. The full harmonic (H2) response is typically not characterized during processing the BAW filters, but specification compliance is guaranteed by design on the final module. Outlier screening on final module response is typically done on only a couple of relevant frequency points due to the time intensive nature of the harmonic measurement. In this work we discuss the feasibility of future wafer level screening of BAW filter H2 during processing. Therefore, we discuss a promising probe procedure to emulate the final module response on the wafer. An example is given to demonstrate potential benefits and cost savings of the presented approach by evaluating the performance of different filter designs on a wafer level in a statistical analysis.