Exposure latitude

Exposure latitude is the maximum amount of dose variation that can he tolerated before a pattern prints out of specification (see Fig. 13.35). A + 10% dimension 

Optics for photolithography, in Microlithography Science and Technology, J.R. Sheats and B.W. Smith, Eds., p. 207, Marcel Dekker, New York (1998). 

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As a measure of pattern collapse, the maximum usable exposure latitude (MUEL) was defined ... 

Fig. 3 Maximum usable exposure latitude (MUEL) as a function of the concentration of the surfactant solution used in the surfactant rinse. The dashed line gives the concentration cefr assumed to have the highest efficiency to reduce pattern collapse...

A quantitative method has been developed to comparatively measure photoresist sensitivity and development/exposure latitude. The second generation resists evaluated exhibit improved sensitivity, good to excellent RPL, but also exhibit slightly lower contrast. 

Di-(fert-butylphenyl)iodonium nonaflate (perfluorobutanesulfonate) Exposure latitude... 

There are quite a few metrics that lithographers use to quantify the quality of an image. These include the contrast, modulation transfer function, exposure latitude. 

Figure 13.35 Exposure latitude for printing a feature of target size 0.4 fim. If the dose to print the feature target is 128 mJ/cm, then the exposure latitude (145 114)/...

The last step calls for the development of the HOL polymer/photoresist film stack in an aqueous basic solvent such as 0.26 N tetramethylammonium hydroxide. This will dissolve and wash away the exposed part of the resist, comprising the carboxylic acid moieties. The preferential diffusion of the HOL into the exposed area of the photoresist results in deprotection of the photoresist polymer at the edge of the unexposed features, leading to their dissolution. This is the basis of the CD reduction, improved process window, and exposure latitude, and smoother sidewall and line edge profile of photoresist features processed with HOL relative to the features processed without HOL. ... 

Color print films are easier to use, since they have more exposure latitude, adjustment of contrast, and ease of use during printing, and reproduction as plates or slides is excellent. We recommend Fujicolor 400... 

Figure 5. Lithographic performance of the resist formulation Copolymer VBA HS (10 90 Mn == 5373 Mw = 15493), N-hydroxyimide-triflate, PGMEA Exposure system ASML 0.5NA Substrate Bari 1200 PAB/PEB 110 C / 110 C Exposure latitude for 1 1 L/S 0.3 pm and below.

Normal CA resists shown in Chapter 2 are available for immersion lithography. However, significant improvements to immersion lithography are also expected when the refractive index (RI) of the resist is increased beyond the current average value of 1.65. Specifically, theoretical calculations have shown that an increase in the RI of the polymeric resist, to a value around 1.9-2.0, will result in an increase in the exposure latitude, contrast, and mask error enhancement factor (MEET), R(ACD f /ACD, ., i,). A. Whittaker et ai 10,11 have reported that the design and S3mthesis of novel polymers with increased RI achieved 193 resist formulations. An essential part of the discovery process is the use of quantitative structure-property relationship (QSPR) models to predict the RI of small molecules and polymers. ... 

Cox, S., Wide Exposure Latitude Photoresists and Fine Line PWB Manufacturing, Board Authority supplement to CircuiTree, Vol. 1, No. 3, October 1999, p. 34. 

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