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Equation 9 · Part 3 · Patterning at the Limit: What Actually Happens When a Chip Is Manufactured

=

DOF=k2λNA2.\mathrm{DOF} = k_2 \frac{\lambda}{\mathrm{NA}^2}.
=

What this part means

The expressions on both sides represent the same quantity under the stated assumptions.

Its job in the formula

The equals sign connects the complete expression on the left with the complete expression on the right. Both sides must have compatible units.

The passage around this formula

The relation that is usually left out of popular accounts is the one that costs money: DOF=k2λNA2\mathrm{DOF} = k_2 \frac{\lambda}{\mathrm{NA}^2}. Depth of focus falls with the square of numerical aperture. Resolution is bought linearly in NA\mathrm{NA} and paid for quadratically in focus budget. This is why the planarisation step exists at all, why resist films keep getting thinner, and why every increase in NA\mathrm{NA} makes the mechanical and material problems worse rather than better. The roadmap is explicit that meeting small depths of focus at 0.55 numerical aperture is a key challenge in its own right, and that a longer-term move to still higher aperture would drive resist thicknesses below 20 nm [ 1 ] .

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Learn the underlying idea

An equals sign says that the expression on its left and the expression on its right have the same value under the stated definitions and assumptions.

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Sources cited in the surrounding passage

These citations provide research context; check each source for the exact claim it supports.