Low 1/f noise design of Hi-CMOS devices

Low-frequency noise characteristics of High-Performance CMOS(Hi-CMOS) devices were measured. It was found that the equivalent input noise power SVg,eqfor n-channel MOSFET´s has a 1/fα spectrum (0.8 < α < 0.95) above 10 µA, even for sealed-down devices with channel lengths LGof 2 µm. The SVg,eqis clearly proportional to 1/Leffdown to 0.8 µm. The noise characteristics of p-channel and n-channel MOSFET´s were compared. It was found that in Hi-CMOS devices, noise reduction in normally-off-type p-channel devices was obtained by light boron-ion implantations at doses below 10¹²cm^-2. The 1/f noise level of p-channel devices was reduced to 1/10- 1/20 that of n-channel devices. In n-channel devices, the low-frequency noise power is a slow increasing function of the drain current. In p-channel devices, on the other hand, a threshold current was observed at which the noise begins to increase rapidly. The results are discussed in this paper in relation to the theoretical model of 1/f noise. The device design for reducing 1/f noise in CMOS differential amplifiers is also examined.