Chemical thinning approach for high-topography glass wafers

In this paper, a novel processing scheme for the thinning of high-topography glass wafers and its use for the fabrication of thin film battery devices is reported. The approach involves different engineering steps from the fabrication of battery stacks on 8" rigid alkali-free glass wafers (initial thickness of 500μm) to the delivery of individual battery devices on etched glass (final thickness from 100pm to 50μm). In particular, we introduce the chemical etching solutions, the used masking materials as well as the technique of battery wafers mounting. This scheme, therefore, allows a wet etching of the rear surface of battery wafers in such a way that the etching system does not disturb the electrochemical properties of thin film batteries. Using the proposed method, fully functional thin film batteries (thickness of 40μm, size of 7mmx7mm) on ultrathin glass (50μm±5μm) were achieved.