Patent ID: 8169813
Filing Date: 2012-05-01
Classification: G11C

Abstract:
1. A method for evaluating an SRAM memory cell which stores data by a flip-flop circuit which is constituted of a first inverter and a second inverter, the method for evaluating the SRAM memory cell comprising the steps of: obtaining first input/output characteristic data which is a characteristic of an output voltage for an input voltage in the first inverter; obtaining second input/output characteristic data by applying X-Y axis conversion to characteristic data of an output voltage for an input voltage in the second inverter; generating first rotary converted data by applying coordinate conversion which rotates a coordinate axis by 45 degrees to the first input/output characteristic data; generating second rotary converted data by applying coordinate conversion which rotates the coordinate axis by 45 degrees to the second input/output characteristic data; specifying a first proximity curve function obtained by fitting the first rotary converted data to a first proximity curve; specifying a second proximity curve function obtained by fitting the second rotary converted data to a second proximity curve; specifying a difference curve function which is the difference between the first proximity curve function and the second proximity curve function; and calculating a static noise margin by specifying a maximum value and a minimum value of the difference curve function, and also by dividing a smaller value out of an absolute value of the minimum value and the maximum value by a square root of 2.