It is well known that, in integrated circuits, a consequence of the Moore's law is a gigantic reduction of the gate oxide thickness (reduced from 170 nm to less than 10 nm in 30 years) [SIA- 98]. As the oxide thickness is the most effective factor influencing the dose hardness, modern gate oxides take vast benefit of the downscaling, as illustrated in the following experimental curve. In principle, this gain is strongly observed in the low dose regime (tox2) and also, but in a lesser magnitude, in the saturation regime (tox ) Note that discrete components, often devoted to medium to high voltage application, escape the Moore's law and therefore still remain potentially very sensitive to total-dose. An Experiment on MOS Aluminum Gate Capacitors, without Oxide Annealing 1 Mrad(Si) 100 A Initial Slope is proportional 150 A Vfb to tox 2 Saturation is proportional to tox 1 250 A Figure 60. Straightforward influence of thickness downscaling [Lera-89a]. EMPIRICAL PROCESS ENGINEERING CURVES FOR THE THERMAL GATE OXIDE AND MODELING 6.3.1. CORRELATIONS CONCERNING OXIDATIONS AND ANNEALS Figure 61 shows examples of correlation between the alpha coefficient and various temperatures: - the temperature of oxidation (in the left chart, the anneal temperature is constant). - the maximal temperature attained by the SiO2/Si layer during the process (right chart). The nature of the gate is indicated as a parameter. III-71 EXPERIMENTAL CORRELATION GENERALIZATION Qox (cm-2) Vt (V) ANNEALED ANNEALED WET OXIDE Tr= 950°C 900°C 850°C 1 Mrad 2 Mrad 3 Mrad 1300°C Annealing Temperature Tr Variable MAXIMUM HIGH TEMPERATURE Oxidation Temperature Tox 850°C Figure 61. Examples of empirical correlation curves. The left figure present typical rough data. The right figure is a compilation of tens of data published in the literature of the 70s and 80s, normalized to tox2 and interpreted by means of the trapping coefficient [Lera-89a]. These correlations have to be considered as indications of trends, and not as absolute rules [Dawe-76, Wino-85, Schw-