Effects of photoresist polymer molecular weight on line-edge roughness and its metrology probed with Monte Carlo simulations
A fast 2D/3D resist dissolution algorithm based on the critical ionization model is used to quantify line-edge roughness and determine its relation to resist polymer molecular weight, the end-to-end distance and the radius of gyration, keeping acid effects off (i.e., minimal). The algorithm permits also simulations of line-edge roughness metrology by examining the effects of SEM measurement box length.
New development model: aggregate extraction development
We propose a new development model (Aggregate Extraction Model), which can explain the generation process of linewidth fluctuations. This model is inherently different from some previously proposed development models in that polymer aggregates, not a single polymer, are treated as the dissolution units. We found that the polymer aggregates about 20 - 30 nm in size are naturally contained in resist films. These aggregates can be observed in the cross section of a resist film and on the lightly exposed resist pattern surface after development. A polymer aggregate dissolves more slowly than the surrounding polymer probably because the polymer density is slightly higher inside the aggregate. Once the surrounding polymer dissolves, the aggregates are extracted and float away into the developer. The polymer aggregates trapped on the pattern sidewall, on the other hand, cause the roughness of the pattern size wall surface, which is responsible for the linewidth fluctuations. We have succeeded in a direct observation of aggregate extraction during the development by AFM observations. The validity of the Aggregate Extraction Model is also discussed from the point of view of the polymer density.
Botulinum toxin in the management of chronic migraine: clinical evidence and experience
Chronic migraine (CM) is a severely disabling neurological condition characterized by episodes of pulsating unilateral or bilateral headache. The United States Food and Drug Administration (FDA) approved onabotulinumtoxinA (Botox®) for the prophylactic treatment of CM in 2010. It has been shown that onabotulinumtoxinA is effective in the reduction of headache frequency and severity in patients with CM. Treatment is well tolerated by the patients. This review reports on the history of botulinum neurotoxin (BoNT) in CM and presents the current clinical evidence for the use of onabotulinumtoxinA in the treatment of CM.