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The Best Laid Plans of 300 mm Fabs Anantha Sethuraman, Sagar A. Kekare, Raman Nurani, and Dadi Gudmundsson, KLA-Tencor Corporation
The move to 0.13 µm, and the introduction of new materials and processing methods such as copper, low-κ materials, and phase shift reticles, are byproducts of the demand for more powerful ICs. As a result, the yield management challenges are difficult, but somewhat anticipated for a move to a smaller design rule. Some of the associated defect samples planning aspects, such as employing e-beam inspection in addition to optical techniques, have been explored 3. For the first time in recent memory, the semiconductor industry is witnessing the convergence of shrinking design rules, the transition to 300 mm, and implementation of new materials in the interconnect scheme such as copper and low-κ dielectrics. The fact that the 300 mm transition is taking place, along with other transitions, creates unique challenges and opportunities in yield management that warrant a new focus in defect sample planning.
Although the transition to new materials and smaller design rules are definitely technology-enabling endeavors, such efforts are not without their characteristic yield management challenges. However, many of these challenges would have been encountered without the 300 mm transition taking place simultaneously. Supposing no 300 mm transition were taking place, previously established sample planning exercises could be performed effectively, with only moderate changes in focus, to establish effective yield management strategies. This paper has been organized to reflect those challenges and provide some insights to surmounting them. The first half of the paper covers in detail some of the 300 mm process-induced challenges, while the second half covers the classical defect inspection sampling problem from a 300 mm standpoint. The detailed discussion of 300 mm processinduced challenges provides a guideline to where new defect inspection points may emerge. Besides suggesting the incorporation of these potential inspection points into 300 mm sampling plans, the latter half of the paper addresses how sample planning in 300 mm fabs needs to take place alongside layout and automation plans for optimal effect.
300 mm technological & processinduced challenges
Films Module Films processes are generally viewed as two somewhat separate categories: planar films stacked on a substrate, and films targeted towards optimal gap-fill to avoid translation of topography. The planar film-stacks such as STI nitride, gate poly-silicon, or refractory metal for silicidation are mostly affected by defects like particles, flakes, pinholes and voids. In addition to these defects, the gap-fill films may have other unique defects when they fail to achieve their primary function of filling a gap between features. Many times such unique defects may not be captured right after deposition, as they stay hidden deep into the folds of these films. Examples of these films are STI HDP oxide, spacer nitride, PMD doped silica glass, IMD doped silica glass for Al interconnects, etc. With advent of copper dual damascene technology, a much larger fraction of films in modern fabs have gap-fill function as their prime objective. Absorption and adhesion between each of the films within a desired film stack is a prime factor that controls the continuity and conformity of such film stacks. Electrochemically deposited copper is especially sensitive to the existence of a sputtered seed layer during the nucleation stage for the copper film. Voids are almost the predominant defect in copper films due to this tendency. New methods in Winter 2002
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