Microsemi-RFIS utilizes a proprietary Microwave Monolithic Ceramic Circuit (MMCC) technology specifically optimized for power applications. This technology is also ideally suited for multi-chip module integration of GaAs monolithics. One of the main features of this technology is the ability to insert solid gold vias through the ceramic substrate while maintaining excellent pattern definition in the immediate vicinity of the hole. Other important features are the air bridges, the fine line definition obtained by dry etching, and the excellent step-coverage of the plasma-deposited silicon nitride.
Shown in the photographs below are some details of circuits fabricated with the MMCC technology, namely, a cross section of a 10 mil wafer with 10 mil vias, a detail of multiple air bridges, and a multi-chip module prior to the die-attachment of the monolithics.
The MMCC technology has enabled Microsemi-RFIS to transfer to ceramic substrates many of the technology advances routinely used in the monolithic field (especially on silicon), such as all dry processing and plasma-deposited silicon nitride. We have added a few key proprietary elements, such as solid via holes and air bridges. A a result, the hybrid approach has been upgraded to a semi-monolithic, miniaturized technology, most effective in power applications, but also ideally suited to multichip integration of monolithic circuits at all power levels.
One of the most characteristics features is the introduction of solid gold vias into the ceramic substrate. These vias, placed directly under the active devices and in other critical positions, act as effective heat sinks and low inductance ground connections.
This technology minimizes parasitics associated with chip components and bond wire interconnects critical to achieving high power at broad bandwidths. Depending on the requirement, we use a combination of three different approaches:
-Microwave ceramic circuits where all elements but the GaAs
-FETs are integrated in a semi-monolithic technology
-Multi-chip modules utilizing the most advanced GaAs MMICs
-Internally matched power devices
Using modular structures, we combine all three approaches to achieve the best overall performance.
This two-stage amplifier was fabricated by die-attaching and bonding GaAs FETs to the ceramic circuit, which includes eight bypass and three tuning capacitors, numerous grounding via holes, and two major heatsinking and grounding vias under the two devices.
Microsemi-RFIS (Formerly AML) Reference Section
U.S. Patent No. 4,925,723, "Microwave integrated circuit substrate including metal filled via holes and method of manufacture."
U.S. Patent No. 5,023,994, "Method of manufacturing a microwave intergrated circuit substrate including metal lined via holes."
F. Sechi, et al., "Radially-Combined 30-W, 14-16 GHz Amplifier," IEEE MTT-S Symposium Digest, 1994, pp. 1737-1740.
F. Sechi, et al., "Miniature Beryllia Circuits for Ku-Band Power Amplifiers," IEEE MTT-S Symposium Digest, 1983, p. 530.
F. Sechi, M. Bujatti, "Broadband Power Amplifiers Based on a New Monolithic Ceramic Technology," IEEE MTT-S Symposium Digest, 1989, pp. 937-940.
M. Bujatti, "Technological Trends in GaAs MESFETs for mm-Wave Applications," Invited Paper, 13th European Microwave Conference, Nurnberg, Germany, September 1983.
