Wafer Manufacturing

10Wafer Metrology and Optical Techniques

10.1 Introduction

The developments and applications of wafer metrology have been to meet the demand for production control for increasingly complex structures on larger wafer substrates. As electronic devices are getting smaller each day, the demand for lower cost and high performance of prime silicon wafers continue to grow. This is also the case for other semiconductor and optoelectronic wafers. The parameters that affect prime wafer manufacturing process need to be monitored carefully in order to produce wafers with extreme flatness and parallelism in a desired thickness. Measurement performance involves the following four factors for modern wafer metrology: (1) sensitivity, (2) repeatability, (3) accuracy, and (4) possibility of integration in the wafer manufacturing process. The automation of manufacturing to reduce cost also requires metrology equipment to keep up with on‐line control and in situ measurement.

10.2 Evaluation and Inspection of the Wafer Surface

Silicon wafers are measured and qualified at different stages of the surface manufacturing process to identify defects and evaluate quality. This is done to eliminate unsatisfactory wafer materials from the process stream and to sort the wafers into batches of uniform thickness at a final inspection stage. These wafers will become the basic raw material, called prime or premium wafers, for new integrated circuits [Bates (2000)].

10.2.1 Wafer Surface Specifications

Surface ...