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Linewidth Measurements by Reflected Light

IP.com Disclosure Number: IPCOM000036780D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Chappelow, RE: AUTHOR [+2]

Abstract

A dimensional measurement technique is shown for measuring semiconductor line widths in the one-micron size range, and in some cases in the 500 nm size range, employing some unique properties of reflected light.

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Linewidth Measurements by Reflected Light

A dimensional measurement technique is shown for measuring semiconductor line widths in the one-micron size range, and in some cases in the 500 nm size range, employing some unique properties of reflected light.

Given two materials with different reflectivities, the average reflectivity is a function of the relative percentage of each material from which the signal is derived. Referring to Fig. 1, consider a repetitive pattern of lines and spaces with a period of f. Let a line width = Wl, and a space width = f - Wl. Let the material comprising the lines have a reflectivity of R2 and that of the substrate R1. Then, if the average target reflectivity as a function of Wl is plotted, the ideal reflectivity curve shown in Fig. 2 will result. By using the ideal curve of Fig. 2 and assuming the structure of Fig. 1, theoretically the line width Wl can be determined by measuring the average target reflectivity. In practice, because most lines possess non-vertical edges, complications are introduced. The ideal curve of Fig. 2 becomes the real curve of Fig. 2, and it is not possible to identify Wl given Rl in most cases.

If the complementary case (Fig. 3) is considered, similar results to the ones cited above are seen except for the obvious reversal of the R(Wl) function. In particular, for constant edge slopes, the real curve deviates from the ideal curve equally in both cases.

When these cases are combined, the combined R(W) curve...