Broadcom builds the TPU chip. Google designs it. You can’t avoid partnering with Broadcom if you want TPUs in significant volume .

Broadcom designs it as well [0], though GCP also works on design as well.

[0] - https://www.broadcom.com/products/custom-silicon

TSMC builds the TPU chip. Broadcom does the rest of the electronics (motherboard, networking, etc...)

And and Broadcom designs a huge part of the chip. They take Google's (mostly) logical design and providing everything TSMC need to physically make the chip (including imports g IP such as serdes, PLLs, and test).