Wafer-level packaging based on uniquely orienting self-assembly (the DUO-SPASS processes)

A wafer-level packaging strategy for micro device chips based on uniquely orienting self-assembly is presented with the following steps: 1) bulk parts are uniquely face- oriented and spread in a single layer; 2) Parts are palletized onto an alignment template having an array of receptor sites; 3) Parts are anchored one-to-one to the receptor sites; 4) Each anchored part is fixed to a unique in-plane orientation. We demonstrate all of these steps with two different self-organizing parallel assembly (SPASS) processes: a semidry uniquely orienting process (semi-DUO-SPASS) and a dry uniquely orienting (DUO-SPASS) process. The semidry process exploits: 1)An agitated air/water interface to uniquely face-orient bulk parts having a single hydrophobic face; 2) A hydrophobic carrier wafer to palletize the parts in an air environment; 3) Orbital shaking to drive the parts until they are anchored to receptor sites; 4) Gravity to uniquely align the parts. Experiments show that 2-mm square silicon parts are correctly registered on a 4-in alignment template having 164 receptor sites with a defect rate of ∼1% after 3min orbital shaking. The dry process utilizes: 1) Asymmetry in dynamic stability to uniquely face-orient bulk parts having protruding features on one face; 2) Orbital shaking to drive the parts until they are first anchored to receptor sites and then fixed in well-defined in-plane orientations by two-stage shape recognition. In our experiments, 1-mm square silicon parts are assembled with a defect rate of ∼2% in 10min on each of two 4-in alignment templates having, respectively, 397 and 720 receptor sites.