Abstract
A successful failure analysis not only depends on extensive electrical and physical fault isolation by using all the advanced FA tools to narrow down the possible failure site, but also relies on actual physical defect findings. For advanced IC devices with technologies approaching sub-10nm and more than 10 layers of metallization built in ultra-low k materials, finding convincing physical defects becomes increasingly challenging. Backside deprocessing to reveal the physical defects at the active circuit layers and interconnect layers have been mostly done with KOH or TMAH as bulk Si etching chemicals, and some successful results have been published in the literatures. However, some challenges are also reported using these chemicals to achieve satisfactory results. In this paper, an improved backside deprocessing technique will be discussed using a special bulk Si etching chemical, choline hydroxide, to successfully reveal the physical defects on advanced IC devices. The new technique showed advantages over the existing techniques with more predictable and reliable results for backside deprocessing work. Two case studies will also be shared to demonstrate how this improved technique has been utilized to successfully reveal the physical damage at transistor gate level on the advanced MCU devices.
