Equation 7 · Part 1 · Patterning at the Limit: What Actually Happens When a Chip Is Manufactured

Symbol R

R

R

What this part means

a half-pitch.

Its job in the formula

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

Full expressionSymbol RArticle meaning

Where the article explains it

Two-beam interference sets a hard floor: for a periodic line-and-space pattern the smallest printable half-pitch is $\lambda$ / (2\, $\mathrm{NA}$ ) , which is $k_1$ = 0.25 in the convention where R is a half-pitch.

The passage around this formula

where $\lambda$ is the exposure wavelength, $\mathrm{NA}$ is the numerical aperture of the projection optics, and $k_1$ is a dimensionless process factor absorbing illumination scheme, mask engineering and resist behaviour. Two-beam interference sets a hard floor: for a periodic line-and-space pattern the smallest printable half-pitch is $\lambda$ / (2\, $\mathrm{NA}$ ) , which is $k_1$ = 0.25 in the convention where R is a half-pitch. Everything the industry calls resolution enhancement — off-axis illumination, phase shifting, optical proximity correction, inverse lithography — is an attempt to drive $k_1$ down toward that floor without printing garbage.

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Learn the underlying idea

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 article section

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