Optimizing wavelengths for optics-based measurements of advanced electronics

The semiconductor industry has just recently met the end of “Moore’s Law”, the cyclical reduction in transistor cost observed over several decades. With the smallest dimensions now approaching near-atomic scales, new architectures and materials combinations are anticipated over the next decade to realize smaller, energy-efficient, high-performance, and secure devices. Optics currently is the non-destructive, fast, inexpensive “workhorse” metrology tool in this industry. This present work addresses the potential promise of and possible requirements for wavelength down-scaling for robustly quantifying dimensions at these scales. The requirements for measuring these critical dimensions at the transistor level, also known as the “Front End of the Line” (FEOL) in manufacturing, will be compared against the also-decreasing dimensions at the “back end of the line” (BEOL); the BEOL consists of metals and insulators and facilitates the flow of electrons between the FEOL-patterned transistors and the semiconductor device’s packaging. The main challenges between optics-based metrology at the FEOL and BEOL will be contrasted with solutions suggested, based upon finite-difference time-domain (FDTD) electromagnetic simulation studies of nominal FEOL and BEOL structures.