Non Uniform Structural Degradation in Porous Organosilicate Films Exposed to Plasma, Etching and Ashing as Characterized by X-Ray Porosimetry

Published

October 25, 2007

Author(s)

Hae-Jeong Lee, Christopher L. Soles, Eric K. Lin, Wen-Li Wu, Yiping Liu

Abstract

The microelectronics industry critically needs non-destructive methodologies capable of profiling the porosity characteristics as a function of depth in the highly porous film that are used as interlayer dielectric insulators in integrated semiconductor devices. Here we illustrate how X-ray porosimetry (XRP) can be used to profile non-uniformities in porosity, average film density, and the density of the wall material between the pores as a function of height, all with nm resolution. We quantify how the plasma and etching plus ashing processes used in back end of the line integration adversely impact on the porous structure of ultra low dielectric constant (k) organosilicate films.There is a both a collapse of the pore structure at the free surface of the film which is exposed to the plasma as well as a general densification of wall material between the pores. The extent of the structural damage is greatest at the exposed surface of the film, with a sharp decreases in the porosity by approximately 6 % and 14 %, and increases in wall density by approximately 42 % and 36 %, in the ultra-low k films (relative to untreated films) exposed to just plasma and etching plus ashing, respectively. It is important to understand, measure, and control this processing induced damage to the porous material as it will lead to an effective increase in the k for the dielectric stack.

Citation

Applied Physics Letters

Volume

91

Pub Type

Journals

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Keywords

ashing, density profile, etch, non-uniform structure, plasma, porosity, ultra low-k dielectric, wall density, x-ray proosimetry

Citation

Lee, H. , Soles, C. , Lin, E. , Wu, W. and Liu, Y. (2007), Non Uniform Structural Degradation in Porous Organosilicate Films Exposed to Plasma, Etching and Ashing as Characterized by X-Ray Porosimetry, Applied Physics Letters, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=852742 (Accessed October 2, 2025)