The etching of Si, SiO 2 , Si 3 N 4 , and SiCH in fluorocarbon plasmas is accompanied by the formation of a thin steady-state fluorocarbon film at the substrate surface. The thickness of this film and the substrate etch rate have often been related. In the present work, this film has been characterized for a wide range of processing conditions in a high-density plasma reactor. It was found that the thickness of this fluorocarbon film is not necessarily the main parameter controlling the substrate etch rate. When varying the self-bias voltage, for example, we found a weak correlation between the etch rate of the substrate and the fluorocarbon film thickness. Instead, for a wide range of processing conditions, it was found that ion-induced defluorination of the fluorocarbon film plays a major role in the etching process. We therefore suggest that the fluorocarbon film can be an important source of fluorine and is not necessarily an etch-inhibiting film.

Articles you may be interested inThe effect of PECVD plasma decomposition on the wettability and dielectric constant changes in silicon modified DLC films for potential MEMS and low stiction applications AIP Advances 2, 032128 (2012); 10.1063/1.4742852Dependences of Young's modulus of porous silica low dielectric constant films on skeletal structure and porosity Surface modified silica mesoporous films as a low dielectric constant intermetal dielectric Integration of new low-interlayer dielectrics ͑ILD͒ with current damascene schemes is a continuing issue in the microelectronics industry. During integration of the ILD, processing steps such as plasma etching, resist strip, and chemical-mechanical planarization are known to chemically alter a layer of the dielectric. Here, porous organosilicate glass ͑OSG͒ ILD films, which-according to the 2004 edition of the International Technology Roadmap for Semiconductors-are projected for use in the 65 and 45 nm nodes, are investigated. spectroscopic ellipsometry, x-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy are used to characterize the modified layer of the ILD after exposure to O 2 or H 2 resist strip plasmas. The effects of the two types of plasma etch chemistries on the formation of the modified layer were found to differ significantly. These effects include both the degree of modification ͑i.e., chemical composition͒ and depth of the modified layer. A key difference between the O 2 and H 2 plasmas is that silicon hydride groups are present in the modified layer after exposure to H 2 plasma but not after exposure to the O 2 plasma. In addition, the influence of OSG porosity on the etch rate and modified layer thickness was investigated for porosities ranging from 0-45 %. As expected, the etch rate was found to increase rapidly with porosity. Finally, conditions including reactive gas concentrations and substrate temperature for the H 2 plasma were varied. These parameters produced considerable changes in the chemistry of the modified layer, especially in the amount of hydrogen incorporated into the film. Details of these results will be discussed in the context of the mechanism by which modification and etching occurs as well as which process variables dominate those phenomena.

Reactive neutral species densities for various conditions in dual frequency capacitively coupled discharges of Ar∕O2, Ar∕N2, and Ar∕H2 were determined using optical emission spectroscopy, Kr actinometry, and modeling. The reactive neutral species probed in this work include O, O2, N, N2, H, and H2. Densities are reported as a function of pressure (5–60mTorr), percent Ar in the feed gas (1%–86%), source power (50–800W), and bias power (0W, 200W). It was found that increasing the pressure from 5to60mTorr resulted in order of magnitude increases in atomic species densities for all ash chemistries. At 30mTorr, percent dissociation is relatively low (⩽15%) for all species. Also, at 30mTorr, the addition of Ar resulted in a small decrease in N and H densities, but an order of magnitude increase in O density. Based on modeling, it is proposed that the increase in O density is due to an increasing contribution of Penning dissociation with increasing Ar density. Only the source power contributed significantly to O and N radical densities, but 200W bias power generated a significant H radical density above that generated via the source power. Details of these results are discussed in comparison with theory and literature.

This paper will examine an approach for automatically identifying endpoint (the completion in etch of a thin film) during plasma etching of low open area wafers. Since many endpointing techniques use a few manually selected wavelengths or simply time the etch, the resulting endpoint detection determination may only be valid for a very short number of runs before process drift and noise render them ineffective. Only recently have researchers begun to examine methods to automatically select and weight spectral channels for estimation and diagnosis of process behavior. This paper will explore the use of principal component analysis (PCA) based T 2 formulation to filter out noisy spectral channels and characterize spectral variation of optical emission spectroscopy (OES) correlated with endpoint. This approach is applied and demonstrated for patterned contact and via etching using Digital Semiconductor's CMOS6 (0.35µm) production process.

Cleaning of CHF 3 plasma-etched SiO 2 /SiN/Cu via structures using a hydrogen plasma, an oxygen plasma, and hexafluoroacetylacetone vaporsThe cleaning of Al, TiN, and Cu blanket samples was investigated in a high density inductively coupled plasma reactor, and compared with results for silicon. After simulating the dielectric overetch exposure of these substrates to a CHF 3 discharge, an in situ O 2 plasma clean and subsequent Ar ϩ premetal sputter clean were performed and evaluated using ellipsometry and x-ray photoelectron spectroscopy. Following the fluorocarbon exposure, significant C and F residues were observed. Exposure to a O 2 plasma clean greatly reduced this contamination. Subsequent treatment with an Ar ϩ sputter further reduced the thickness of the modified surface layer. Comparisons of the cleaning results with silicon suggest an efficient cleaning procedure, especially in the cases of copper and titanium nitride. The response of several blanket, oxide-like low-K dielectrics to the O 2 plasma treatment were also studied and compared to SiO 2 . While a fluorinated SiO 2 ͑SiOF͒ exhibited SiO 2 -like stability, deep modifications were observed in both hydrogen silsesquioxane and methyl silsesquioxane, consistent with the removal of hydrogen and carbon from these films. These results were compared to a dedicated chamber design, where no fluorocarbons contaminate the reactor. The dedicated chamber methodology offered no significant advantage.