3D Atomic Force Microscopy as an Alternative to X-SEM and TEM for Advanced Process Metrology (AN91)

3D Atomic Force Microscopy as an Alternative to X-SEM and TEM for Advanced Process Metrology double for each device node at 90nm Introduction and below, which means a significant As increasing demand for smaller increase in development costs and device feature data drives wafer delay in process development due to development costs up, process the long turnaround times. developers seek new metrology Whereas the available error budget solutions to better address today's of TEM is consumed by LWR and line stringent process requirements. edge roughness (LER), the X3D atomic Traditional, destructive measurement force microscope is able to accurately techniques such as cross-section quantify both. The Dimension X3D, scanning electron microscopy (X-SEM) which provides robust data on and transmission electron microscopy materials via the highest sensitivity with (TEM) are labor- and cost-intensive subnanometer resolution, can also methods whose long turnaround times differentiate between sidewall angle are not suitable for integration into and CD. In addition, the X3D offers process flow. Optical techniques, improved three-dimensional accuracy. meanwhile, although suited for on-line This state-of-the-art instrument has no metrology simply do not provide material bias, is compatible with sufficient direct information and require various dielectric materials and cross-checking with accurate metrology photoresist, and has NIST traceable to verify models. Figure 1. The Dimension X3D Atomic CD standards. Force Microscope. Atomic force microscopy (AFM), on the By providing extremely short other hand, represents an excellent turnaround times (minutes) and a fully solution for advanced process Trends and Benefits automated measurement sequence metrology. The Digital Instruments ™ that allows integration into process Dimension X3D Automated Atomic 3D profile, line edge roughness, line flow, the X3D accelerates technology Force Microscope from Veeco (see width variability and sidewall angle are development cycles. Another key Figure 1), is able to deliver TEM-like becoming more important for process benefit is its attractive cost savings. performance at a fraction of the cost. control. At 110nm and above, Unlike X-SEM and TEM, AFM The X3D reduces cost per wafer pass traditional top-down CD-SEMS (critical measurements are nondestructive by a factor as high as 10 and provides dimensions) were adequate for process and require no sample preparation. n on investment after only 500 toa retur control. At 90nm and below, however, Cost of ownership for the X3D is up 1000 cross-sections performed (i.e., by shape-related variations gain to 10 times lower than TEM. X-SEM or TEM). Furthermore, this mance.forsignificance for device per nondestructive instrument is designed for In short, the Dimension X3D atomicAnd at 65nm and below, controlling in fab use for process control. force microscope delivers accuratesidewall angle and line width variability Numerical results and data are profile results, both faster and at aWR) is required to maximize yield and(L available within minutes. lower cost, than X-SEM and TEM fordevice performance. It is worth noting process control and development.that TEM measurement volumes actually