Through Pitch monitoring by optical scatterometry

摘要

Scatterometry critical dimension (SCD) technology in state of the art semiconductor manufacturing is a well-accepted and powerful technique to determine profile properties such as critical dimensions, sidewall angles, trench depths as well as layer thicknesses of microelectronic structures. The amount and combination of information receivable via SCD measurements makes it, as long as interpreted correctly and incoming process variations especially incoming material variations are well understood, superior to other measurement techniques such as critical dimension scanning electron microscopy (CDSEM), transmission electron microscopy (TEM) or atomic force microscopy (AFM). For high throughput inline process monitoring and feedback SCD models are usually generated for uniform gratings having fixed pitches representing dense areas of the microelectronic chip design. However, for purposes such as improvement in process tool matching, wafer uniformity or optical proximity correction (OPC) it is of great value if the measured test patterns do have different layout properties being representative for other design elements and styles as well. In this paper a through pitch SCD measurement within the shallow trench isolation (STI) layer on the 28nm node is presented. This approach allows to interpret, to tune and to monitor process tool behavior for different pattern densities using only one single specially designed lithography mask. Two different use cases are shown: for varying pitch sizes either the designed line CD or the designed space CD is kept constant. General SCD modelling approaches and examples to illustrate the key idea and practical use will be provided.