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On a graph of normalized remaining thickness against ${\log }_{10}D$, both positive photoresist curves remain near unity below $D_0$ and fall to zero by $D_c$. Their transition widths are ${\log }_{10}(D_c/D_0)=1/\gamma$: $0.752$ decades for the lower-contrast material and $0.177$ decades for the higher-contrast material. The latter therefore has a much steeper transition. The curves can be aligned at a common illustrative clearing dose; their absolute horizontal placement cannot be inferred from photoresist contrast alone.

The higher-contrast material distinguishes bright and dark regions even when diffraction has reduced their intensity modulation. The lower-contrast material requires a much stronger aerial-image modulation and loses small features earlier. Finite resist thickness, standing waves, acid diffusion, development conditions and photon statistics can limit actual performance beyond this threshold model.

For a positive photoresist, let $D_0$ be the largest exposure preserving the initial film thickness and $D_c$ the clearing dose. The photoresist contrast is $\gamma =1/{\log }_{10}(D_c/D_0)$. An aerial image $I=\bar{I}[1+M\cos (2\pi \nu x)]$ can clear its maxima while retaining its minima only ifThus $M_c=0.6991$ and $0.2006$ for the lower- and higher-contrast materials. Reading those levels on the supplied modulation transfer function gives maximum normalized spatial frequencies approximately $\nu /{\nu }_0=0.40$ and $0.60$, respectively. The stated partial coherence is already represented by that curve; do not multiply the read frequencies by another coherence factor.

The unambiguous pattern dimensions are full pitch $P=1/(x{\nu }_0)$ and equal line/space width $w=P/2$, where $x$ is the read normalized frequency. To convert the paper's Rayleigh-frequency label into lengths, explicitly use the circular-pupil Rayleigh criterion $d_R=0.61\lambda /NA$ and ${\nu }_0=1/d_R$. With the ArF vacuum wavelength $193\mathrm{nm}$ and the stated numerical aperture, $d_R=235.5\mathrm{nm}$, givingThe higher-contrast material resolves a line/space feature about two-thirds as wide. The pitch and half-pitch distinction matters: the point-separation Rayleigh criterion is not itself an equal-line/space width. If a course defines ${\nu }_0$ as an optical cutoff rather than $1/d_R$, use that specified frequency in $w=1/(2x{\nu }_0)$; the normalized graph readings and their ratio are unchanged. No absolute clearing dose is provided.

Reading the straight-line extrapolation in the printed photoresist contrast curve gives approximately $D_0=20\mathrm{mJ}\mathrm{c}{\mathrm{m}}^{-2}$ at unit remaining thickness and $D_c=100\mathrm{mJ}\mathrm{c}{\mathrm{m}}^{-2}$ at clearing. On the logarithmic dose axis,The critical image modulation follows by requiring one exposure time to give $D_{\max }\ge D_c$ in a bright region and $D_{\min }\le D_0$ in a dark region:For unit object modulation, this meansThe doses are graphical estimates, so extra significant figures would not represent greater measurement accuracy.

Read the straight-line extrapolation on the logarithmic dose axis, rather than the rounded shoulder of the measured curve. The retention and clearing intercepts are approximately $D_0=10$ and $D_{100}=50\mathrm{mJ}\mathrm{c}{\mathrm{m}}^{-2}$. Thus the photoresist contrast isHere the subscripts denote the two dose thresholds used in the supplied definition. The physical positive-resist curve decreases with exposure; $D_{100}$ is the higher clearing dose in that definition, not a statement that the film retains its full thickness there. Graphical intercepts justify roughly two significant figures.

For a positive photoresist, let $D_r$ be the largest dose retaining the nominal film and $D_c$ the clearing dose. With the conventional photoresist contrast definition,For a sinusoidal aerial image, the bright-to-dark dose ratio is $(1+C)/(1-C)$, where $C$ is the Michelson contrast. A dose window that clears bright regions while retaining dark regions requiresThis assumes a fully modulated input pattern and that the plotted modulation transfer function gives the aerial-image contrast. It is a dose-window criterion, not a statement that the resist creates optical information absent from the image.^[ref]

The two thresholds are approximatelyReading their intersections with the supplied curve gives, to graphical accuracy,for the lower- and higher-contrast resists respectively. These are the results independent of the dimensional frequency convention. Their minimum full periods are $P=1/\nu$, and equal line/space widths are half those periods:An ArF excimer laser uses $\lambda \simeq 193\mathrm{nm}$. A numerical length requires specifying what the caption's “Rayleigh limit” means. Taking it literally as the reciprocal of the Rayleigh criterion point separation givesIf instead the graph uses the common incoherent-cutoff normalization ${\nu }_0=2\mathrm{NA}/\lambda$, the widths are $302\mathrm{nm}$ and $201\mathrm{nm}$, with periods twice those values. The caption does not explicitly provide an equation for ${\nu }_0$ or define whether “feature size” means period or half-pitch, so these conventions must not be silently mixed. The higher-contrast resist resolves the higher normalized frequency in either convention.