US Patent 7208065 Structure for measuring the etching speed

The specification discloses a structure and method for measuring the etching speed. A test layer is connected with several resistors. Etching the metal layer disconnects in order the resistors from the circuit. The equivalent resistance of the sensing resistor system is measured to obtain the etching speed. In consideration of the errors of the resistors, the invention also provides a structure that utilizes an IC layout technique to put an interdigitized dummy resistor beside the sensing resistors. By taking the ratio of the equivalent resistance of the sensing resistors and the dummy resistor, the invention can compute to obtain the etching speed.