Protecting Chips Against Hold Time Violations Due to Variability by Gustavo Neuberger Gilson Wirth & Ricardo Reis

Author:Gustavo Neuberger, Gilson Wirth & Ricardo Reis
Language: eng
Format: epub
Publisher: Springer Netherlands, Dordrecht

7.2 Separation Results

The first step in the analysis was to apply the separation methods described in the previous section in the RO frequency variability. The three methods were compared: moving average with a 3 × 3 window, moving average with a 5 × 5 window, and curve fitting. Figures 7.1, 7.2, 7.3, 7.4, 7.5 and 7.6 show the curves obtained for the 130 nm wafer, while Figs. 7.7, 7.8, 7.9, 7.10, 7.11 and 7.12 show the results for the 90 nm wafer. In 130 nm, the curve obtained was a paraboloid, what could be observed already in the original data. However, in the 90 nm wafer, the original data was very random and difficult to see any systematic dependence, but the mathematical methods showed a plane, with ring oscillator frequency increasing from one side of the wafer to the other.

Fig. 7.1Variability curves in 130 nm wafer: systematic variability using method Moving Average with 3 × 3 window

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