| 摘要 |
A method and apparatus for measuring capacitances in the pressure of stray capacitances is disclosed. A high frequency voltage signal is applied to a first node of the capacitor being tested. The frequency and change in voltage of the signal is known and measured precisely. The current flowing through the small capacitor is measured during a known portion of the signal's period. The measuring period is chosen so that the stray capacitances charge and discharge during the period, thereby adding no net current to the measured current. As the measured current, frequency, and change in voltage are all known precisely, the capacitance of the test capacitor can be calculated precisely. For testing capacitances in semiconductor wafers, a plurality of test structures comprised of a plurality of test capacitances are fabricated on the wafers. Using known decoding methods and apparatus, individual capacitances within individual test structures can be accessed and measured, using the method of the present invention.
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