Prediction of UV spectra and UV-radiation damage in actual plasma etching processes using on-wafer monitoring technique

Abstract

UV radiation during plasma processing affects the surface of materials. Nevertheless, the interaction of UV photons with surface is not clearly understood because of the difficulty in monitoring photons during plasma processing. For this purpose, we have previously proposed an on-wafer monitoring technique for UV photons. For this study, using the combination of this on-wafer monitoring technique and a neural network, we established a relationship between the data obtained from the on-wafer monitoring technique and UV spectra. Also, we obtained absolute intensities of UV radiation by calibrating arbitrary units of UV intensity with a 126 nm excimer lamp. As a result, UV spectra and their absolute intensities could be predicted with the on-wafer monitoring. Furthermore, we developed a prediction system with the on-wafer monitoring technique to simulate UV-radiation damage in dielectric films during plasma etching. UV-induced damage in SiOC films was predicted in this study. Our prediction results of damage in SiOC films shows that UV spectra and their absolute intensities are the key cause of damage in SiOC films. In addition, UV-radiation damage in SiOC films strongly depends on the geometry of the etching structure. The on-wafer monitoring technique should be useful in understanding the interaction of UV radiation with surface and in optimizing plasma processing by controlling UV radiation.

Comparison of surface vacuum ultraviolet emissions with resonance level number densities. II. Rare-gas plasmas and Ar-molecular gas mixtures

“…3 Degradation of low dielectric constant ("low-k") materials used to insulate wiring in high-speed IC interconnects has been attributed to exposure to VUV during etching, stripping and cleaning steps using O 2 , Ar/O 2 , and He/H 2 plasmas. [4][5][6] SiOCH low-k dielectric films consist of SiO 2 doped with carbon (in methyl groups) and are fabricated with a high concentration of nanopores. Both the carbon doping and nanopore introduction are strategies to reduce the dielectric constant.…”

“…Solid points: absolute vacuum photodiode measurements, which includes contributions from emissions out of both Ar(1s 2 ) and Ar(1s4 ) levels, open circles: normalized sodium salicylate signal, line: VUV transport model using measured Ar(1s 2 ) and Ar(1s 4 ) number densities.…”

The effect of He plasma treatment on properties of organosilicate glass low-k films

“…The type of plasma reactor mainly affects the ratio of charged and neutral species; the carrier gases can change the spectra of VUV radiation. 16,17 These techniques allow the measurement of UV radiation spectra from the plasma and then predicting the type of damage. Several recently published papers give the extensive review of the available experimental data and provide the detailed analysis of chemical and physical processes occurring during the exposure of porous OSG materials in different kinds of etch, strip, and cleaning plasmas, and different types of plasma reactors.…”

Optical Observation of Deep Bulk Damage in Amorphous Perfluorocarbon Films Produced by UV Photons Emitted from Low-Pressure Argon Plasma

“…As with electrical charge-up and ion bombardment, photons in the UV and especially in the vacuum ultraviolet (VUV) regions emitted from plasma also induce damage on device materials [9][10][11][12][13][14][15][16][17]. Although the number of reports on UV-induced damage in LSI fabrication is much smaller than those on damage induced by electrical charge-up and ion bombardment, the recent increase in the use of organic materials in electronic devices, e.g., for low-k dielectric barrier and flexible semiconductors, has highlighted the ever-growing importance of the study on UV-induced damage in plasma processing.…”