Layout Dependence Stress Investigation in through Glass via Interposer Architecture Using a Submodeling Simulation Technique and a Factorial Design Approach

The multi-chiplet technique is expected to be a promising solution to achieve high-density system integration with low power consumption and high usage ratio. This technique can be integrated with a glass interposer to accomplish a competitive low fabrication cost compared with the silicon-based interposer architecture. In this study, process-oriented stress simulation is performed by the element activation and deactivation technique in finite element analysis architecture. The submodeling technique is also utilized to mostly conquer the scale mismatch and difficulty in mesh gridding design. It is also used to analyze the thermomechanical responses of glass interposers with chiplet arrangements and capped epoxy molding compounds (EMC) during curing. A three-factor, three-level full factorial design is applied using the analysis of variance method to explore the significance of various structural design parameters for stress generation. Analytic results reveal that the maximum first principal stresses of 130.75 and 17.18 MPa are introduced on the sidewall of Cu-filled via and the bottom of the glass interposer, respectively. Moreover, the EMC thickness and through glass via pitch are the dominant factors in the adopted vehicle. They significantly influence the stress magnitude during heating and cooling.

Reliability Assessment of Thermocompressed Epoxy Molding Compound through Glass via Interposer Architecture by the Submodeling Simulation Approach

In glass interposer architecture and its assembly process, the mechanical responses of interposer structure under thermocompression process-induced thermal loading and generated shrinkage of molding material are regarded as a major reliability issue. Thousands of metal-filled via are involved in glass interposers and are regarded as a potential risk that can lead to cracking and the failure of an entire vehicle. In this study, a finite element-based submodeling approach is demonstrated to overcome the complexity of modeling and the relevant convergence issue of interposer architecture. Convergence analysis results revealed that at least four via pitch-wide regions of a local simulation model were needed to obtain the stable results enabled by the submodeling simulation approach. The stress-generation mechanism during thermocompression, the coefficient of thermal expansion mismatch, and the curing process-induced shrinkage were separately investigated. The critical stress location was explored as the outer corner of the chip, and the maximum first principal stress during the thermocompression process generated on the chip and glass interposer were 34 and 120 MPa, respectively.