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Flexible substrate with floating island structure for mounting ultra-thin silicon chips

A flexible substrate with a novel floating island structure design was developed for mounting ultra-thin silicon chips. The structure reduced the strain propagated from the stretching base to the ultra-thin silicon chips. While conventional structures reduce strain by 64.2%, the floating island structure reduced strain by 90.2%. Furthermore, tests for operational stability and durability were conducted using an ultra-thin operational amplifier (OPAMP) mounted on the flexible substrate with a floating island structure, where the OPAMP was thinned to 30 µm by chemical mechanical polishing. The ultra-thin OPAMP operated with no strain effects even when repeatedly stretched to 30% elongation. Also, the ultra-thin silicon chip mounted on the floating island structure demonstrated durability against >25 000 stretching cycles. This research is applicable for functional wearable devices using ultra-thin silicon chips and featuring high flexibility and stretchability.