Mass spectrometry studies of resist trimming processes in HBr∕O2 and Cl2∕O2 chemistries
05 Jan 2005-Journal of Vacuum Science & Technology B (American Vacuum Society)-Vol. 23, Iss: 1, pp 103-112
TL;DR: In this article, a parametric study of HBr∕O2 and Cl2O2 resist trimming processes correlated to x-ray photoelectron spectroscopy (XPS) analyses has been performed.
Abstract: In a previous article, a parametric study of HBr∕O2 and Cl2∕O2 resist trimming processes correlated to x-ray photoelectron spectroscopy (XPS) analyses has been performed. The present article confirms the preliminary results obtained by XPS. Mass spectrometry experiments have established that the slow resist erosion rate measured in Cl2∕O2 trim chemistries is attributed to a competitive etching of the resist by atomic chlorine and oxygen, while in HBr∕O2 trim chemistries, atomic oxygen is the main etching species, bromine playing only a minor role. The etching of the resist by the oxygen species originating from the dissociation of HBr∕O2 and Cl2∕O2 plasmas generates the formation of volatile resist-etch-by-products such as CO and CO2, while the etching of the resist by halogen (bromine or chlorine) generates less volatile and heavier resist-etch-by-products such as CxHyBrz with bromine and CxHyClz with chlorine. Mass spectrometry has also shown that plasma conditions leading to a higher concentration of h...
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TL;DR: In this article, the authors compare the silicon recess generated by continuous wave HBr/O2/Ar plasmas and synchronous pulsed HBr /O2 /Ar plaasmas, showing that the oxidized layer which leads to silicon recess can be reduced from 4 to 0.8 nm by pulsing the plasma in synchronous mode.
Abstract: Plasma oxidation of the c-Si substrate through a very thin gate oxide layer can be observed during HBr/O2/Ar based plasma overetch steps of gate etch processes. This phenomenon generates the so-called silicon recess in the channel and source/drain regions of the transistors. In this work, the authors compare the silicon recess generated by continuous wave HBr/O2/Ar plasmas and synchronous pulsed HBr/O2/Ar plasmas. Thin SiO2 layers are exposed to continuous and pulsed HBr/O2/Ar plasmas, reproducing the overetch process conditions of a typical gate etch process. Using in situ ellipsometry and angle resolved X-ray photoelectron spectroscopy, the authors demonstrate that the oxidized layer which leads to silicon recess can be reduced from 4 to 0.8 nm by pulsing the plasma in synchronous mode.
68 citations
TL;DR: In this article, an atomic force microscope (AFM) was used to obtain 3D line edge roughness (LER) measurements for a full pattern transfer into a simplified gate stack, where the sample is tilted at about 45° and feature sidewalls are scanned along their length with the AFM tip to obtain three-dimensional images.
Abstract: With the constant decrease of semiconductor device dimensions, line edge roughness (LER) becomes one of the most important sources of device variability and needs to be controlled below 2 nm for the future technological nodes of the semiconductor roadmap. LER control at the nanometer scale requires accurate measurements. We introduce a technique for LER measurement based upon the atomic force microscope (AFM). In this technique, the sample is tilted at about 45° and feature sidewalls are scanned along their length with the AFM tip to obtain three-dimensional images. The small radius of curvature of the tip together with the low noise level of a laboratory AFM result in high resolution images. Half profiles and LER values on all the height of the sidewalls are extracted from the 3D images using a procedure that we developed. The influence of sample angle variations on the measurements is shown to be small. The technique is applied to the study of a full pattern transfer into a simplified gate stack. The images obtained are qualitatively consistent with cross-section scanning electron microscopy images and the average LER values agree with that obtained by critical dimension scanning electron microscopy. In addition to its high resolution, this technique presents several advantages such as the ability to image the foot of photoresist lines, complex multi-layer stacks regardless of the materials, and deep re-entrant profiles.
45 citations
TL;DR: In this paper, the etch rate and faceting of a TiN hard mask in terms of etch speed and facetting were investigated using a dielectric etch process.
Abstract: This study focuses on the etching characteristics of a TiN hard mask in terms of etch rate and faceting when using a dielectric etch process. The etching experiments have been performed on blanket wafers and patterned structures in an inductively coupled plasma using a conventional CF4∕Ar based plasma. The etch rate and faceting of TiN have been measured as a function of the plasma parameters (bias power and pressure) and also plasma chemistries (Ar dilution and CH2F2 addition). The TiN etch rate is about 30nmmin−1 using the base line process conditions (70SCCM CF4, source power of 500W, bias power of 100W, and pressure of 4mTorr). Lower etch rate is observed at lower pressure and bias power and with higher Ar dilution and CH2F2 addition. The faceting is strongly reduced at lower bias power and higher pressure whereas higher Ar dilution and CH2F2 addition have no clear effect on the facet formation. Surface analysis using x-ray photoelectrons spectroscopy reveal that the top surface of TiN is mainly fluor...
35 citations
TL;DR: In this article, the authors present some key issues related to the patterning of narrow porous SiOCH trenches with a metallic (TiN) hard mask, which can help in controlling the profile of the etched structures, minimizing plasmainduced damage, and controlling the impact of various types of etch stops and hard mask materials.
28 citations
Journal Article•
TL;DR: In this paper, a 10 nm isolated silicon pattern on a very thin gate can be achieved if the plasma parameters and chemistry that impact the critical dimension (CD) control are well understood, such as the passivation layers that form on the silicon gate sidewalls which directly impact the CD control, the nature of the mask used during the gate process (resist mask or SiO2 hard mask), the charging effects developed when the plasma lands on a thin gate oxide.
Abstract: This article demonstrates that a 10 nm isolated silicon pattern on a very thin gate can be achieved if the plasma parameters and chemistry that impact the critical dimension (CD) control are well understood. The parameters investigated are the passivation layers that form on the silicon gate sidewalls which directly impact the CD control, the nature of the mask used during the gate process (resist mask or SiO2 hard mask), the charging effects developed when the plasma lands on a thin gate oxide.
24 citations
References
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TL;DR: In this paper, the authors investigated the assumption that the extraction efficiency of ions produced by direct ionization of radicals and dissociative ionisation of the parent molecule used as the reference signal, are equal in the ionizer of the mass spectrometer.
Abstract: Appearance potential mass spectrometry (APMS) has recently gained importance for detection and quantitative measurements of reactive radical species in plasmas using line-of-sight sampling of radicals. In this work, we have investigated the assumption that the extraction efficiency of ions produced by direct ionization of radicals, and ions produced by dissociative ionization of the parent molecule used as the reference signal, are equal in the ionizer of the mass spectrometer. We find that the dissociative ionization products are extracted with much lower efficiency (2–50 times smaller for the cases studied) than the direct ionization products. This is expected due to the excess kinetic energy of the dissociatively ionized products as a result of the Franck–Condon effect. Use of this procedure will thus lead to an overestimation of the radical number density by a factor of 2–50, depending on the nature of the parent and the daughter ion. We recommend an alternate procedure for APMS that utilizes an inert...
95 citations
TL;DR: In this article, the authors characterized the contributions of the mass spectrometer signal from the line-of-sight "beam" component and the background component of the reactive species in the ionizer of the massive mass analyzer.
Abstract: Mass spectrometry and appearance potential mass spectrometry (APMS) have recently gained importance for detection and quantitative measurements of reactive radical species in plasmas using line-of-sight sampling of reactive species. In this work, we have characterized the contributions to the mass spectrometer signal from the line-of-sight “beam” component and the background component of the species in the ionizer of the mass spectrometer. The beam signal is proportional to the number density of the species in the plasma, while the background component of the signal depends on various factors like the vacuum system design and pump speeds. Single differential pumping of the mass spectrometer is found to be inadequate as the background signal dominates the beam signal for radical and stable neutral species. The beam to background ratio for CFx (x=1–3) radicals is smaller than 0.25 and the large background signals of the species of interest necessitates implementation of modulated beam mass spectrometry usin...
79 citations
TL;DR: In this paper, mass spectrometry has been used to investigate the chemical composition of the ion flux bombarding the reactor walls of an industrial inductively coupled plasma used for 200mm-diam silicon wafer processing.
Abstract: Anisotropic etching of silicon gates is a key step in today’s integrated circuit fabrication. For sub-100 nm gate dimensions, one of the main issues is to precisely control the shape of the etched feature. This requires a detailed knowledge of the various physicochemical mechanisms involved in anisotropic plasma etching. Since silicon etching in high-density plasmas is strongly ion assisted, the identities of the ions bombarding the wafer is a key parameter that governs the etch rates and the etched profiles. In the present article, mass spectrometry has been used to investigate the chemical composition of the ion flux bombarding the reactor walls of an industrial inductively coupled plasma used for 200-mm-diam silicon wafer processing. The plasma chemistries investigated are HBr/Cl2/O2 and HBr/Cl2/O2/CF4 mixtures optimized for sub-100 nm gate processes. Quantitative ion mass spectra show that under those conditions the ion flux contains up to 50% of SiClXBrY+ (X,Y=0–2) ions, although Cl+, Cl2+, and Br+ i...
79 citations
TL;DR: In this paper, the absolute concentration of fluorine atoms (F), a parameter of great importance for the characterization and modeling of etching plasmas, was measured by means of threshold ionization mass spectrometry in a CF4 microwave plasma.
Abstract: The absolute concentration of fluorine atoms (F), a parameter of great importance for the characterization and modeling of etching plasmas, was measured by means of threshold ionization mass spectrometry in a CF4 microwave plasma (p=15–100 mTorr). The kinetics of these atoms and those of CF2 and CF3 radicals were studied by pulsing the plasma and time-resolved detection of these radicals with mass spectrometer. Sticking coefficients of F atoms on the different surrounding surfaces were estimated, as a function of the discharge parameters and the nature of the surfaces interacting with the plasma. It was found that the sticking of F atoms on hexatriacontane polymer surface is highly activated by the plasma generated ions and/or ultraviolet radiations.
50 citations
TL;DR: In this paper, a soft landing scheme was used for the etching of poly gates, which resulted in vertical profiles without punch through and with minimum damage to the thin gate oxide and the substrate.
Abstract: Charging induced damage of thin gate dielectric during polysilicon gate etching in a high density decoupled plasma source was investigated for 0.16 and 0.24 μm gates on 30 A nitrided gate oxide. The undoped polysilicon gates were etched with a HBr/He/O 2 based process recipe. The optimized process recipe resulted in vertical profiles (89°–90°) with microloading of No notching of the polysilicon or punch through of the thin gate oxide was observed. Gate leakage and breakdown voltage measurements after gate formation were made on metal-oxide-semiconductor capacitor structures with antenna ratios ranging from 100:1 to 1000:1. These measurements did not exhibit any damage to the thin gate dielectric. In addition, no significant change in the damage characteristics was observed over a wide process window around the optimized recipe, i.e., increased over etch (OE) time, increased source power, or reduced bias power in the OE step. A soft landing scheme was used for the etching of poly gates. This scheme provides vertical profiles without punch through and with minimum damage to the thin gate oxide and the substrate.
37 citations