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Title: In-situ characterisation of positive photoresist development during automated wafer processing
Author: Robertson, Stewart A.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1994
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The place of optical lithography within integrated circuit manufacture is discussed, and the key nature of its role identified. All aspects of lithographic processing are reviewed, highlighting the long list of process conditions which influence the final results. The manner in which lithographic processes are evaluated and characterised is also reviewed, illustrating the large amount of work required to compare different processes. Computer simulation of lithography is reviewed as a quick and cheap way of investigating the effect of key processing parameters on process results. Such simulations are only useful, in this respect, if they exhibit the same trends as genuine processes and are quantitatively accurate. Experimental results reveal discrepancies between modern track-based development techniques and the immersion processes generally used to generate the input parameters for simulation of the development. A novel polychromatic Development Rate Monitor (DRM) is introduced capable of measuring resist dissolution rates in-situ on manufacturing equipment. Results from this equipment demonstrate significant differences between immersion and track development. The detailed output from the DRM system coupled with a new analysis technique allow accurate estimation of post exposure bake diffusion lengths and have led to the derivation of a new model describing surface induction effects during development. Having accurately characterised continuous spray and static puddle development processes, a new 'interrupted development' simulation technique is introduced to simulate the spray/puddle processes commonly employed in manufacturing facilities. Excellent correlation is demonstrated between these simulations and experimental results.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available