Silicon on insulator (SOI) substrates are widely used in forming semiconductor dies due to the low cost of silicon materials, large scale capacity of wafer production, well-established semiconductor design tools, and well-established semiconductor manufacturing techniques. However, harmonic generations and low resistivity values of the SOI substrates severely limit the SOI's usage in radio-frequency (RF) applications. By using SOI substrates in RF fabrications, an interface between the silicon handle layer and an adjacent dielectric layer will generate unwanted harmonic and intermodulation products. Such spectrum degradation causes a number of significant system issues such as unwanted generation of signals in other RF bands that the system is attempting to avoid. In addition, the relatively low resistivity encountered in the silicon handle layer limits the performance and quality factor of inductive elements embedded in the semiconductor dies, such as inductors, transmission lines and couples, by the generation of unwanted RF current loss in the silicon handle layer.
Further, with the current popularity of portable communication devices, high speed and high performance transistors are more densely integrated on semiconductor dies. The amount of heat generated by the semiconductor dies will increase significantly due to the large number of transistors integrated on the semiconductor dies, the large amount of power passing through the transistors, and the high operation speed of the transistors.
Accordingly, there remains a need for improved microelectronics package designs that improve the quality factor and inductance value of the inductive elements, and accommodate the increased heat generation of the semiconductor dies. In addition, there is also a need to enhance the performance of the microelectronics package without increasing the package size.