This chapter delves into the pivotal roles of chemical mechanical planarization (CMP) and wafer grinding in contemporary IC packaging fabrication. CMP facilitates critical processes like interlayer dielectric planarization, copper interconnect planarization, and through-silicon via (TSV) integration, ensuring uniformity and reliability in semiconductor structures. Wafer grinding enables precise thinning of semiconductor wafers, essential for compact packages and integrating multiple dies. Thinner wafers not only enable smaller packages but also enhance thermal dissipation, making them ideal for mobile devices and IoT sensors. These techniques are instrumental in producing high-performance IC packages with superior electrical properties, compact form factors, and enhanced reliability. This chapter offers insights into their applications and significance in modern semiconductor manufacturing, contributing to a deeper understanding of advanced IC packaging fabrication processes.