Silicon-On Insulator (Sol) based devices have been a research theme for about two decades. The advantages over BulkSi are clear and SO1 substrates have been expected to break into the main am CMOS IC industry. Until now these expectations have not been realized. Reasons are (i) SO1 wafer availability, quality and cost, (ii) SO1 MOSFET's floating body effects and lower breakdown voltage. And (iii) economic reasons that propel BulkCMOS advances in circuit techniques and process technology. Today, the situation is changing; battery operated portable devices are called to perform advanced functions that include communication in the RF spectrum at frequencies in the 400 MHz to 2.5 GHz range, as well as complex signal and graphic processing. The low-voltage, low-power and high performance requirements are showing the limitations of BulkCMOS and opening a new opportunity for SOI. In this paper, the status of SO1 device applications and manufacturing considerations are reviewed.
SO1 for Low-Voltage ApplicationsCMOS devices implemented on SO1 substrates demonstrate power consumption reduction of about 1/5 X compared with BulkSi CMOS [I]. as Fig. 1 shows for a CMOS inverter. The speed performance of the SO1 CMOS is approximately one generation ahead of BulkSi. In complex logic IC's, where interconnect capacitance dominates the logic gate loading, the low source/drain capacitance of the SO1 device is nullified. However, due to the suppressed back bias effect and the possibility to reduce Vth due to the abrupt subthreshold characteristic, at the same operating speed, SO1 MOSFET's are able to operate at lower supply voltage than BulkCMOS. This ~s u l t s in a net reduction of power consumption. Fig.2 shows the power dissipation ratio between Bulk and SO1 2-input NAND gates vs the metal interconnect capacitance, at constant propagation delay. Even for a typical loading of 0.lpF (-lmm metal line), a 1/3 X power reduction is expected. SO1 has already demonstrated the capability to replace BiCMOS E W PLL frequency synthesizers in the 1 to 2 GHz frequency range [2,3]. Operating at 1.5V and 1.2 GHz, SO1 PPL's show a 1/9 X reduction in power as compared with the BiCMOS PLL. The high frequency performance of the 0.35um MOSFTT's implemented on SIMOX wafers shows a transition frequency fT= 21GHz @ 0 . 7 5 (Fig.3) that demonstrates their RF capabilities, and shows the possibility of a single-chip CMOS, low cost RF fiont-end. Fig.4 illustrates a perspective of the power-supply, IC feature size and the circuit techniques. voltage is reduced new circuit techniques need to be applied to control the DC leakage current F with Vdd
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