Overlay error statistics for multiple-exposure patterning

Abstract

Background: The mathematical equations that explain overlay error of multiple-exposure patterning schemes have not been fully described in the literature and some commonly accepted methods lead to inaccurate estimated and/or measured overlay error. Aims: Develop the proper mathematical framework, using a first principles statistical approach, so that engineers using multiple-exposure patterning can determine the overlay impact and overlay controls needed. Alert patterning community that grouped overlay metrology of multiple-exposures undermeasures the true overlay error. Approach: Use image placement error and population-based statistics to enable a mathematical framework to be established that predicts the actual overlay error for an overlaying pattern that minimizes overlay error back to a pattern that is patterned with multiple-exposure patterning. Results: The overlay error between two patterns is usually less than the root sum square of the two overlay error values of the patterns individually measured to a common prior pattern. Overlay error for a pattern minimizing back to multiple-prior patterns increases quickly as systematic overlay error between the prior patterns increases. Conclusions: Controlling systematic overlay error between patterns of a multipatterned layer is important for subsequent patterns that need to minimize overlay error back to the composite multipatterned layer. The ratio between the overlay error determined with metrology and true overlay can be calculated.

Degradation of Perfluorododecyl-Iodide Self-Assembled Monolayers upon Exposure to Ambient Light

“…With each advancement in technology, the intricacy and number of these procedures grow, leading to significant challenges in terms of patterning techniques. Patterning at scales smaller than 10 nm using these top–down techniques faces a number of difficulties, including edge placement errors, decreasing throughput, complexity, pattern collapse, and photoresist non-uniformity [ 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. Due to these issues, there is a push towards using extreme UV photolithography.…”

Self-assembled monolayers as inhibitors for area-selective deposition: A novel approach towards resist-less EUV lithography

“…A very thin photoresist is desirable for critical dimensions smaller than 10 nm as higher thickness can lead to pattern collapse or, bending during the development step due to capillary forces [8][9][10][11][12]. Some of the other limitations of the process are edge placement error, overlay errors, complexity, economic, environmental, low throughput etc [4,[13][14][15][16][17][18][19]. These challenges have forced industry to shift towards bottom-up deposition schemes using atomic layer deposition (ALD) which allows growing films by subsequent addition of atoms in a layer by layer fashion [20][21][22].…”