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Critical dimension measurement and sidewall slope evaluation using a coherence probe microscope

The drive by the manufacturers and designers of integrated circuits towards smaller dimensions has led to ever increasing demands being placed on the vendors of semiconductor equipment. In the photolithography arena this has meant producing optical projection systems with improved resolution approaching 0.2μm and layer to layer registration to better than 50nm. In order to monitor these processes, metrology equipment must be capable of tracking changes in the above areas. Traditionally, optical techniques have been utilised for several reasons, namely their cost, high throughput and ease of use. The drive however, towards circuit dimensions which are equal to the wavelength of the illuminating light has reduced the appeal of optical tools to be used at these dimensions. The ability to get as close as possible to the theoretical limit is of benefit to the users and manufacturers of metrology equipment in that the useful life of optical metrology tools can be increased. This has been achieved by examining and implementing various new algorithms developed for the coherence probe microscope, the aim of which is to improve the measuring ability and extract more information from the complex signal that the microscope produces. Three areas have been examined, the first was the effect of a pathlength offset on the microscope, which moves the coherence region away from the focal plane of the objective lens. The results from this show a substantial improvement in the repeatability of the measurements from the bottom of trenches. The second area is that of profile extraction, in particular that of a photoresist profile after development. The ability to extract profile information from an optical tool is of great use to a lithography engineer as it negates the need to destructively cross section the sample. Thirdly, the area of general algorithms for measurement of critical dimensions has been investigated and several other schemes for measurement have been proposed.
Date January 1994
CreatorsDavies, Guy Scott
PublisherUniversity of Edinburgh
Source SetsEthos UK
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation

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