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Equation 1 · Part 2 · How Advanced Semiconductor Fabrication Actually Works

Symbol λ

mλ≈2dcos⁡θ,m\lambda \approx 2d\cos\theta,
λ\lambda

What this part means

λ is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

Its job in the formula

λ is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

The passage around this formula

…Bragg condition for layered reflectors, mλ≈2dcos⁡θm\lambda \approx 2d\cos\theta. describes why the stack works at all: at near-normal incidence, θ\theta is small and cos⁡\cosθ\theta is close to one, so the first-order condition reduces to roughly λ\lambda ≈\approx 2d , meaning a bilayer period d of a little under 7 nanometers should reflect strongly somewhere near 13.5–14 nanometers. Measurement bears this out closely rather than exactly: one recent study of Mo/Si multilayers built for EUV optics reports bilayer periods of 6.97 to 7.07…

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A variable is a named place for a value. Its letter is a local label: x can mean position in one formula and a data point in another.

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Sources cited in the surrounding passage

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