Semi E131
SEMI E131 defines the physical interface for integrated measurement modules using BOLTS-M — the mechanical mounting geometry, connector locations, and signal-pin assignments that let a measurement module bolt directly onto a process tool's chamber or transport in a fixed, predictable location — as the hardware counterpart to E127's IMMC communication model and E127.1's SECS-II protocol binding. E127 and E127.1 standardize how a host software triggers and reads an integrated measurement module over SECS-II; neither says anything about how that module physically attaches to the process tool itself — where it bolts on, what connector it uses, which pins carry power versus signal — and without a shared physical interface, every process-tool vendor would need custom mechanical integration work for each metrology vendor's module, even after the communication layer was already solved.
The reason the communication standards weren't enough on their own is that SECS-II messages travel over a network connection, but the module generating them still has to be bolted onto, and wired into, the physical process tool — and a fixed mechanical envelope the host software never has to think about was still an open mechanical-engineering problem for every tool/module vendor pairing. E131 closes that gap by defining BOLTS-M's bolt pattern, connector placement, and pin-out as a fixed hardware contract, so a process-tool OEM can design a mounting bay once and have it accept any BOLTS-M-compliant measurement module, rather than re-engineering the physical mount every time a fab wants to swap in a different metrology vendor's module.
E131 completes the integrated-measurement-module stack by giving the hardware side of E127/E127.1 the same interchangeability guarantee the communication side already has: with the bolt pattern, connector location, and pin assignments fixed by BOLTS-M, a process tool can accept any compliant module both mechanically and electrically, and a fab can swap metrology vendors without a custom retrofit at either the software or the hardware layer.