A Highly Latchup-Immune 1-μm CMOS Technology Fabricated with 1-MeV Ion Implantation and Self-Aligned TiSi₂

A 1-μm n-well CMOS technology with high latchnp immunity is designed, realized, and characterized. Important features in this technology include thin epi substrate, retrograde n-well formed by 1-MeV ion implantation, As-P graded junctions, and self-aligned ticanium disilicide. The 1-μm CMOS technology has been characterised by examining the device I-V curves, avalanche-breakdown voltages, subthreshold characteristics, short-channel effect, and sheet resistances. The devices fabricated by using the 1-MeV ion implantation and self-aligned titanium disilicide do not deviate from the conventional devices constructed with the same level of technology. With the As-P double-diffused LDD structure for the n-channel device, the avalanche-breakdown voltage is increased and hot-electron reliability is greatly improved. The titanium disilicide process effectively reduces the sheet resistances of the source-drain and the polysilicon gate to 3 Ω/□ compared with 150 Ω/□ of the unsilicided counterparts. The optimized 1-μm device channel n-well CMOS resulted in a propagation delay time of 150 ps with a power dissipation of 0.3 mW. With the thin epi wafers and the retrograde n-well structure, latchup immunity is found to be greatly improved. Moreover, with the titanium disilicide formation on the source-drain, the latchup holding voltage is found to be extremely high (13 V) with the substrate grounded from the backside of the wafer. If the backside substrate is not grounded, self-aligned disilicide over n⁺ and p⁺ regions are found necessary to ensure high latchup immunity even in the case of thin epi on heavily doped substrate. The degradation of emitter efficiency due to the TiSi₂ is believed to be the dominant factor in raising the holding voltage. Detailed experimental results and discussions are presented.