Device construction & distinguishing traits
Silicon and thin film capacitors are a relatively new crop of devices produced using tools, methods, and materials borrowed from the semiconductor industry. The precise control over structure and materials that these techniques provide allows production of near-ideal capacitors with excellent parameter stability, minimal ESR & ESL, wide service temperature capabilities, and comparable to better capacitance per volume compared to the Class 1 ceramic type devices with which they most directly compete. Their main disadvantages include high cost and, as a related matter, a relatively limited range of available capacitance values.
Typically based on a silicon oxide/nitride dielectric, the distinction between “thin film” and “silicon” capacitors is something of a marketing concession, though significant differences exist within & among the two depending on the intended application. Devices targeting RF tuning & matching applications tend to be low-capacitance, single-layer devices optimized for parameter stability and consistency, and are commonly found in standard JEDEC package sizes. In contrast, devices intended for power supply decoupling, broadband DC blocking, and similar applications allow larger tolerances in favor of achieving higher specific capacitance, and are more likely to be found in packaging adapted to advanced assembly methods such as wire bonding or embedding within a PCB. Regardless of intended application however, devices in the thin film and silicon capacitor families are premium-performance products and are priced accordingly, currently fetching something on the order of 5 to 5000 times the price of ceramic devices with similar capacitance and voltage ratings.
Parts designed as high-precision devices mostly compete with ceramic capacitors based on C0G (NPO) dielectrics, as a higher-performance alternative for RF and microwave applications. While these class I ceramic devices are quite good and approach idealness themselves after some decades of refinement, characteristic manufacturing differences allow thin film/silicon devices to be a little better, in terms of consistency across devices and manufacturing lots.
Higher-capacitance thin film/silicon capacitors compete more directly with the class II ceramics based on X7R and X8R dielectrics for de-coupling and broadband DC blocking applications. For these purposes, thin film/silicon devices can offer notable advantages, such as a significantly lower dissipation factor and much better stability of capacitance over temperature and voltage.