In the nanometer era, the physical verification of CMOS digital circuit becomes a complex task. Designers must account of new factors that impose a significant change in validation methods. One of these major changes in timing verification to handle process variation lies in the progressive development of statistical static timing engines. However the statistical approach cannot capture accurately the deterministic variations of both the voltage and temperature variations. Therefore, we define a novel method, based on non-linear derating coefficients, to account of these environmental variations. Based on temperature and voltage drop CAD tool reports, this method allows computing the delay of logical paths considering more realistic operating conditions for each cell. Application is given to the analysis of voltage drop effects on timings.
In low power UDSM process the use of reduced supply voltage with high threshold voltages may reverse the temperature dependence of designs. In this paper we propose a model to define the true worst Process, Voltage and Temperature conditions to be used to verify a design. This model will provide an accurate worst case definition for high performance designs where standard design margins are not applicable. This model is validated at either cell level or path level on two different 130nm process.
In the nanometer era, the physical verification of CMOS digital circuit becomes a complex task. Designers must account of numerous new factors that impose a drastic change in validation and physical verification methods. One of these major changes in timing verification to handle process variation lies in the progressive development of statistical static timing engines. However the statistical approach cannot capture accurately the deterministic variations of both the voltage and temperature variations. Therefore, we define a novel method, based on nonlinear derating coefficients, to account of these environmental variations. Based on temperature and voltage drop CAD tool reports, this method allows computing the delay of logical paths considering the operating conditions of each cell.
In low power UDSM process the combined use of reduced value of the supply voltage and high threshold voltage value may greatly modify the temperature sensitivity of designs, which becomes structure and transition edge dependent. In this paper we propose a model for determining the temperature coefficient of CMOS structures and defining the worst Process, Voltage and Temperature condition to be verified for qualifying a design. This model is validated on two 0.13µm processes by comparing the calculated values of the temperature coefficient of the performance parameters to values deduced from electrical simulations (Eldo). Application to combinatorial path gives evidence of the occurrence of temperature inversion that is structure and control condition dependent and must carefully be considered for robust design validation.
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