Above-Complementary Metal–Oxide–Semiconductor Metal Pattern Technique for Postfabrication Tuning of On-Chip Inductor Characteristics

In the design of radio frequency (RF) circuits, modifying the characteristics of an inductor in efficient way is required to realize rapid prototyping of RF system-on-a-chip (SoC). We propose an above-complementary-metal–oxide–semiconductor (above-CMOS) metal pattern technique. In this technique, metal patterns are formed using a simple process on the passivation layer above the on-chip inductor. Since the metal pattern with different shapes has different effects, we can tune the characteristics of an on-chip inductor by forming various metal patterns in a chip-by-chip manner. This method can experimentally create various inductors from an identical on-chip inductor. Therefore, the optimization of inductor characteristics and related circuit performance can be carried out in a short period and at a low cost on a trial-and-error basis, which is very effective for rapid prototyping of RF SoCs. Adjustment of the oscillation frequency of the voltage-controlled oscillator using this technique and the technique of modeling the above-CMOS metal pattern are also described in this paper.