Takatoshi Kato

High-resistance ZrN thin film resistor for small and low-cost MMIC switch

GaAs monolithic microwave integrated circuit switch (MMIC SW) for cellular phones and WLAN are required to be smaller. The chip size can be smaller using a high-resistance thin film resistor (HR-TFR) because the resistance of the gate-resistor for the SW is very large. ZrN is thought to be one of the most promising materials for HR-TFRs. However, the ZrN TFRs have a thermal stability problem. In this study, we investigated the effect of thermal annealing on the ZrN film to improve the thermal stability. We found oxidized bumps in the ZrN TFR that are formed at the contact edge between the ZrN TFR and the electrode reduced the stability of the ZrN TFR. With an appropriate annealing condition, these oxidized bumps are suppressed and the stability of the ZrN TFR is improved. We developed a stable HR ZrN TFR of approximately 4000Ω/sq. to fulfill design requirements. We made the chip about 30% smaller in case of a single pole double throw (SPDT) MMIC SW for WLAN applications with the ZrN TFR.

Millimeter-wave DRO with Excellent Temperature Stability of Frequency

Novel millimeter-wave dielectric resonator oscillators (PRO) and dielectric resonator voltage controlled oscillators (DR-VCO) have been developed for communication systems. The authors have been developing DROs with a novel structure called PDIC (planar dielectric itegrated circuit), which layers are composed of a microstrip circuit substrate stacked on a high ¿r dielectric resonator (DR) substrate with electrodes on both surfaces. The DR substrate and a pair of hollow patches on the electrodes form a dielectric resonator (TE010 mode DR). This paper focuses on the improvement of the temperature stability of the PDIC-DRO by controlling the material composition of the DR. An excellent temperature stability of oscillation frequency of less than 1ppm/deg C has been obtained for DRO and DR-VCO. The phase noise of the DRO and DR-VCO is - 100dBc/Hz and ¿94 dBc/Hz at 100kHz offset respectively. The DRO or DR-VCO without PLL can be used for millimeter-wave sources of communication systems.