Synthesis and control of ultra thin gate oxides for the 90 and 65 NM nodes

Thin gate oxide processes for advanced semiconductor manufacturing present many challenges at both the 90 and 65 nm technology nodes. In most cases the films are oxynitride materials (SiO_xN_y) constructed in single wafer tools clustered on the same common platform. The combination of discrete process chambers and the atomic dimensions of the dielectric puts a premium on film characterization and process control. The electrical specifications are severe with common values of ±1Å leading to nitrogen and oxygen dose requirements of better than ±5E14 at/cm ². In the recent past difficulties maintaining those specifications have repeatedly lead to tool down situations and limited run paths. In the aftermath of those events, the investigations which followed exposed weaknesses in both the metrology and the qualification strategies used to characterize those processes. In this paper, a number of examples will be presented which illustrate the sensitivity of the composite process to excursions in any of its component steps. The relative sensitivities of different in-line measurement techniques (optical, electrical, and chemical) will be reported and the data used to illustrate the clear advantages of in-line compositional analysis.