Process development for commercial manufacturing of micromachined millimeter wave components

Seeqc is pleased to submit this phase I SBIR proposal to develop a fabrication process for commercial manufacturing of micromachined millimeter wave components. Microfabrication techniques developed under this project will be generally useful to manufacture detector coupler/holders that are machined to micron-level tolerance operating at the cryogenic temperature. Therefore, this project is responding to - “Ultimate-performance mechanical materials for precision support and cooling are of general interest for HEP detectors. Mechanical structures are used to hold detector elements with micron precision and stability.” Objective of the project is to perform technology transfer to enable an industry partner to microfabricate silicon-based millimeter wave components. Feedhorn coupled Transition Edge Sensor detector arrays that are widely used successfully by multiple cosmic microwave background (CMB) experiments are microfabricated on silicon wafers. These detector arrays are coupled to aluminum horn arrays via microfabricated silicon coupling wafers. The next generation CMB experiment, CMB-S4, is expected to deploy orders of magnitude more, approximately 500, detector arrays than what is currently deployed in the field. Currently, NIST is the only institution that has delivered these coupling wafers to the CMB community. Industry knowhow can bring high throughput and potential for cost reduction to coupling wafers fabrication. Seeqc is uniquely positioned because of its prior development of TES sensors with LBNL for CMB experiments. Seeqc have successfully fabricated TES sensor arrays using deep reactive ion etcher (DRIE), one of the key equipment required to fabricate the coupling wafers. Seeqc being a quantum computing company will benefit from the proposed fabrication processes as the innovation fits well with the requirement of fabrication of low-noise scalable superconducting qubit arrays while controlling the number of input/output (I/O) channels. The 3D integrated circuit process is critical for building scalable, low noise quantum circuits, in which I/O is efficiently done using capacitive and inductive coupling between quantum array and classical control chip The introduction of an optimized and well characterized of a high-quality qubit process will be directly applicable to the needs of quantum computing community and hence Seeqc and will greatly increase business opportunities to the industry in general. During Phase-I we will port established processes for fabricating silicon coupling wafers to Seeqc processing equipment. Detailed fabrication steps that were developed by NIST has been provided to Seeqc via CMB-S4 project. We will closely follow the established recipe while making necessary adjustments to the process to work well with equipment at Seeqc. We will improve fabrication throughput and cleanliness (therefore yield) by changing wafer bonding process between the process wafer and the carrier wafer from a melted wax bonding method to electrostatic bonding. During Phase-I we will demonstrate full compatibility of fabrication processes for all three types of coupling wafers that are required by the CMB-S4 project. During Phase II of the program, we will implement the developed process to mass fabrication of the coupling wafers and stress test the process flow to identify any bottlenecks that may arise and implement solutions.