1. Purpose and scope
Unlike a digital chip, a MEMS sensor rarely has a mature design kit waiting for it. Even on an established MEMS platform, a new sensor often needs a different film thickness, a new etch depth, a different cavity pressure or a new release step. This stage develops those steps until each runs inside its window, joins them into one flow, and freezes the flow as the process baseline that the layout, models and qualification will rely on.
The critical modules are specific to MEMS. Structural films must have controlled residual stress and stress gradient so released parts do not curl. Deep etches must hold their profile and sidewall angle across the wafer. Sacrificial release must remove the right material without leaving residue or causing the structure to stick. Bonding or thin film encapsulation must seal the cavity at the intended pressure and keep it there. Anti-stiction treatment must survive the bonding temperature. The design rules come out of this work, and the transducer layout is drawn to them and released as the MEMS mask set at the end of the stage.
In scope: process development and baselining, MEMS design rules, process control monitor structures, the transducer design specification, the detailed multiphysics model and the transducer behavioural model, the transducer layout and its checks, and the MEMS mask set. Out of scope: the interface ASIC design, which runs in Interface ASIC Co-design, and the first prototype wafers, which are processed and measured in Prototype Build & Model Correlation.
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