5. Metrology for Microsystems Manufacturing

Microsystems fabrication utilizes a number of metrology techniques during development and manufacturing that are reviewed in Chap. 5. These techniques are used in development after processing steps are performed (reviewed in Chaps. 3 and 4) to find and diagnose problems that may be present. In manufacturing, metrology is employed to maintain quality control and thereby increase production yields. Metrology also enables the process engineers to monitor the status of the processing equipment used in production. There are a wide variety of metrology tools that are available, including inspection of the devices during and after fabrication; measurement of the dimensions of various important elements of the microsystems; and chemical analysis of materials used in fabrication. Some of the basic metrology techniques that have been developed for the IC industry are discussed, followed by a review of several more specialized metrology techniques specific for MEMS fabrication. Guidance as the accuracy of each of the metrology methods is given in Tables 5.2 through 5.5 providing a quick look-up summary of these metrology methods along with their resolution, precision, and accuracy.