Microwave monolithic integrated circuit fabrication, test method and

Abstract

The present invention performs RF performance measurements on basic transistors of a microwave monolithic integrated circuit while it is being fabricated. The circuitry necessary to assess the performance potential at the frequency and power levels of interest is provided by incorporating matching elements onto RF probes used for in-process tests. This invention measures the RF performance potential of GaAs monolithic microwave integrated circuits at an early stage in the process before expensive process sequence has been completed. The essence of the invention is that the transistors are measured with an RF probe that has RF matching circuitry included as an integral part of the probe. Consequently, the performance potential of circuits on the wafer is assessed at the earliest possible point in the manufacturing process; specifically as soon as Schottky barrier gates have been deposited. This in-process measurement approach may be applied to any microwave monolithic integrated circuit. Once the correlation between in-process and post-process measurement results are established, the present method may be used to routinely screen wafers, thereby saving roughly two-thirds of the processing costs of 'RF bad' wafers.