Recent developments in producing test-structures for use as critical dimension reference materials

NIST is developing Single-Crystal Critical-Dimension Reference Materials (SCCDRM) which address the need of the semiconductor and semiconductor equipment industries for a well-characterized artifact to serve as the basis for comparing the performance of different classes of critical dimension (CD) measurement instruments. Recent work has focused on providing an integrated process that can be transferred to a production environment. In this paper we discuss recent work to address issues identified as key to successful completion of the project. The first issue is the requirement to provide reference materials with CDs at or near the minimum found on state-of-the-art chips. To meet this requirement using conventional processing, the CD reference materials would need to be produced using process technologies not yet available. Therefore, a process is used that will allow the reduction of the CDs of silicon features on selected chips by adding a sequence of three wet etches to reduce the overall width of the replicated features while enabling them to retain their essential cross-section rectangularity and sidewall flatness. In this paper we describe this modification and present initial results. The remaining issues center around the test structure design for the imaging metrology tools, in particular, high-resolution transmission electron microscopy (HRTEM), which is the most time-consuming and expensive of the measurement processes. A new test structure was developed which incorporates a set of different-width features placed in a way that allows optimal evaluation of the features by several imaging techniques.