Method and apparatus for measuring threshold characteristic of semiconductor integrated circuit

An apparatus for measuring a threshold characteristic of a semiconductor integrated circuit having an input circuit whose operation state varies depending on whether an input signal voltage is above or below a threshold, the apparatus comprising:

• signal generating means for repeatedly generating as an input signal to be fed to the semiconductor integrated circuit, a clock signal having an amplitude within a range from a predetermined reference voltage which is significantly greater or less than an approximate threshold voltage to a peak voltage which differs by a variation amount toward the approximate threshold voltage from the predetermined reference voltage, and sequentially changing the peak voltage of the clock signal by a predetermined variation amount at a time;
• change detecting means for detecting a change of a power source current supplied to the semiconductor integrated circuit;
• and
• measuring means for responding to an output from the change detecting means and measuring the peak voltage of the input signal outputted from the signal generating means as the threshold, when the change of the power source current exceeds a predetermined range.

A method for measuring threshold characteristics of an integrated circuit which includes a input circuit having an operation state which varies depending on whether an input signal voltage is above or below a threshold, said method comprising the steps of:

• (a) setting a first reference signal at a predetermined voltage level which is significantly greater than or less than an approximate threshold level;
• (b) setting a first peak voltage at the first reference voltage level;
• (c) inputting a clock signal to the integrated circuit, the clock signal varying between the first reference signal and the first peak voltage;
• (d) determining whether a current signal output from the integrated circuit indicates that a threshold level has been reached and deciding that the input first peak voltage is a first threshold value when the output current signal indicates that a threshold level has been reached;
• (e) when said step (d) does not indicate that a threshold level has been reached, changing the first peak voltage by a predetermined amount;
• and
• (f) repeating said steps (c)-(e) until it is indicated that either a threshold level has been reached or that an entire range of potential first peak voltages has been input to the integrated circuit.

An apparatus for measuring threshold characteristics of an integrated circuit which includes an input circuit having an operation state which varies depending on whether an input signal voltage is above or below a threshold, said apparatus comprising;

• a signal generator which generates a reference signal which is significantly greater or less than an approximate threshold level, an adjustable peak voltage which is sequentially adjusted toward the approximate threshold level, and a clock signal which varies between the generated reference signal and the adjustable peak voltage;
• a change detector which detects when a current signal output by the integrated circuit indicates that a threshold level has been reached;
• and
• a test circuit for determining, as a threshold level, the peak voltage resulting in an indication from said change detector that a threshold level had been reached.