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FEBRUARY 2024 I DESIGN007 MAGAZINE 45 • Ceramic insulators bonded to package substrates or embedded in interposers Embedded dielectric foils like tantalum can be used on-die as a sintered layer. is enables a thin layer over a large area, giving a low-pro- file embedded capacitor film integrated into a semiconductor die. Following the same approach as embed- ded dielectric foils, ceramics can also be used in substrates and interposers as an embed- ded capacitive film when a standard organic ECM is not suitable. While ECMs target both PCBs and packaging, embedded ceram- ics currently sit in the packaging domain and are compatible with multiple substrate/ interposer materials. An example is shown in Figure 4. ese ceramic films are placed as a thin metal-insulator-metal (MIM) structure. The target frequency range is up into GHz frequencies. Trench Capacitors ese structures are fabricated directly into silicon, either in a die or in interposers. ey can have unique vertical structures that attempt to maximize the exposed surface area that defines a trench capacitor, thereby maximizing the capacitance of each trench. Multiples of these trench structures act like a large group of capacitors in parallel, so they collectively pro- vide high capacitance without decreasing the self-resonant frequency of the structure. e target frequency range runs into the GHz frequencies. Figure 4: Embedded ceramic film structure for a package substrate/interposer. Figure 3: This 6-layer PCB stackup can use an ECM between L2 and L3, or between L4 and L5, to form a large embedded capacitor. A similar strategy could be used with packaging.