Scaling of poly-encapsulated LOCOS for 0.35 μm CMOS technology |
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Authors: | Kenkare P.U. Mazure C. Hayden J.D. Pfiester J.R. Ko J. Kirsch H.C. Ajuria S.A. Crabtree P. Vuong T. |
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Affiliation: | Adv. Products Res. & Dev. Lab., Motorola Inc., Austin, TX; |
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Abstract: | We demonstrate the scaling of Poly-Encapsulated LOCOS (PELOX) for 0.35 μm CMOS technology without detrimental effects on gate oxide and shallow source/drain junction integrity. As-grown bird's beak punchthrough is shown to fundamentally limit the scalability of LOCOS-based schemes for narrow nitride features. A quantitative comparison of bird's beak punchthrough is made between LOCOS, Poly-Buffer LOCOS (PBL), and PELOX. The PELOX scalability is emphasized by evaluating the impact of the polysilicon-sealed cavity length for narrow nitride features. We present the realization of a 1 μm active/isolation pitch fully meeting the geometry and off-leakage requirements of 0.35 μm CMOS technologies (VDS⩽5 V). This field-implant-free isolation module avoids unnecessary process complexity by successfully integrating scaled PELOX with the split well-drive-in scheme. A highlight of this new approach is that the NMOSFET characteristics are largely width-independent down to 0.3 μm dimensions |
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