Rodolfo Lucero

System-in-a-package integration of SAW RF Rx filter stacked on a transceiver chip

Demands for mobile phones with smaller form factor and lower cost have driven enhanced integration of electronics components. However, surface acoustic wave (SAW) filters must be fabricated on piezoelectric substrates, and so they are difficult to monolithically integrate on semiconductor chips. This paper reports on a compact wafer-scale packaged SAW filter stacked over a transceiver chip in a quad flat-pack no-lead (QFN) package. An integrated passive device (IPD) provided redistribution and matching between the SAW filter output and the transceiver input. Both extended global system for mobile communications (EGSM) and DCS filters were evaluated. Results demonstrated that conventional packaging techniques could be used to successfully assemble stacked SAW on transceiver modules without damage. SAW compact models based on the coupling of modes model were developed to facilitate system design. Electromagnetic simulations of coupling between SAW filters and inductors integrated on the transceiver suggested that design care is needed to avoid interactions, especially if an IPD is not used as a spacer. With appropriate design, stacked SAW filter on transceiver offers viable module integration.

Submicron p-channel (Al,Ga)As/(In,Ga)As HIGFETs

Submicron p-channel (Al,Ga)As/(In,Ga)As HIGFETs have been optimized for application to high-performance complementary GaAs circuits. Major issues with submicron and deep submicron (L/sub g//spl les/0.5-/spl mu/m) P-channel HIGFETs have been the severe short-channel effects, such as high subthreshold leakage currents and high output conductances. With optimization of the p-type self-aligned implant schedule, control of impurity contamination at the substrate/buffer interfaces and increase of the resistivity of the unintentionally-doped GaAs buffers, high-performance submicron devices have been realized. Typically, 0.5-/spl mu/m P-HIGFETs yielded room temperature transconductances of 90 mS/mm, drain currents at V/sub gs/=V/sub ds/=-1.5 V of 63 mA/mm, and subthreshold leakage currents near 1 nA. Subthreshold slope of 90 mV/decade and output conductances under 5 mS/mm were realized.

Experimental observation of velocity overshoot in n-channel AlGaAs/InGaAs/GaAs enhancement mode MODFETs

Velocity overshoot phenomena in n-channel Al-GaAs/InGaAs/GaAs enhancement mode MODFETs have been investigated for gate lengths ranging from 1 to 0.5 /spl mu/m. The study is based on Motorolas established CGaAs/sup TM/ technology. The observed average electron velocity /spl upsi//sub a/spl upsi// under the gate is 1.05, 1.34, 1.48, and 1.71/spl times/10/sup 7/ cm/s for a gate length L/sub G/ of 1, 0.7, 0.6, and 0.5 /spl mu/m, respectively. The presence of velocity overshoot in InGaAs channels is clearly proven with average electron velocities exceeding the steady-state saturation velocity of /spl cong/1/spl times/10/sup 7/ cm/s for L/sub G//spl les/0.7 /spl mu/m, and with the significant increase of /spl upsi//sub a/spl upsi// with shorter gate length.

Integration of SAW RF Rx filter stacked on a transceiver chip in a QFN package

Enhanced integration of mobile phone components is driven by demands for reduced form factor and cost. Because SAW filters must be fabricated on piezoelectric substrates, they are difficult to monolithically integrate on semiconductor chips. Here we report on the integration of a compact wafer-scale packaged SAW filter stacked over a transceiver chip in a quad flat-pack no-lead (QFN) package. An integrated passive device interposer provided redistribution and matching. We demonstrated the successful integration of both EGSM and DCS filters in such modules. SAW compact models based on the coupling of modes model were developed to facilitate system design.