Sanket Sant

Deposition and patterning of diamondlike carbon as antiwear nanoimprint templates

In this work, antiwear nanoimprint templates were made by depositing and patterning diamondlike carbon (DLC) films on Si and quartz. A capacitively coupled plasma enhanced chemical vapor deposition (PECVD) system was configured to deposit 100nm–1μm thick DLC films on Si and quartz substrates. These films were characterized with Raman spectroscopy, electron energy loss spectroscopy, atomic force microscopy, nanoindentation, contact angle measurements, and optical transmission measurements. The rf power and pressure of the PECVD process were varied to obtain uniform coating of DLC films with smooth surface (∼0.2nm rms), low surface energy (∼40mJ∕m2), and high hardness (∼22GPa). The resulting films’ wear resistance is more than three times better than quartz. The DLC films were patterned by nanoimprint lithography using polymethylmethacrylate (PMMA) followed by CF4 plasma etch. Thermal nanoimprint tests with DLC templates were performed in PMMA. Atomic force microscopy measurements indicated excellent patter...

Effect of surface temperature on plasma-surface interactions in an inductively coupled modified gaseous electronics conference reactor

The effect of wall temperature, from 50to200°C, on gas phase chemistry and substrate etching rates has been studied in inductively coupled CF4 plasma under two distinctive initial wall conditions, namely “clean” and “seasoned.” During plasma etching, we found that the gas phase chemistry exhibits a weak dependence on the initial wall cleanliness when the wall is either cold (50°C) or hot (200°C). In the mid-temperature range, the wall cleanliness can strongly affect gas phase chemistry. The study of temperature dependence of the fluorocarbon film deposition on the substrate indicates that ion-assisted incorporation, direct ion incorporation and ion-assisted desorption are the major factors determining film growth and removal. Ion-assisted incorporation and desorption are surface-temperature-dependent, while direct ion incorporation is independent of the surface temperature.

Investigation and modeling of plasma-wall interactions in inductively coupled fluorocarbon plasmas

Plasma-wall interactions in fluorocarbon based feedgas chemistries, namely CF4, are examined in a standard inductively coupled Gaseous Electronics Conference reference cell using in situ Fourier-transform infrared spectroscopy and microwave interferometry. Measurements show the dissociation of the CF4 feedgas into radical CFx species, as has been observed elsewhere [M. J. Goeckner and R. A. Breun, J. Vac. Sci. Technol. A 11, 3 (1993)], and qualitatively reveal a decrease in plasma-wall interactions as wall temperature is increased. Experimental results such as plasma density, 1011 cm−3, and CF4 density 1013 cm−3, are further compared to results from the hybrid plasma equipment model [R. Kinder and M. J. Kushner, J. Vac. Sci. Technol. A 19, 76 (2001)] to better elucidate the influence of wall temperature on plasma exposed surfaces and sticking coefficients. Last, CF4 vibrational temperatures were also measured, revealing that the line-averaged vibrational temperature remains at a constant 40–60 K above the chamber wall temperature while the vibrational temperature in the center of the discharge is significantly higher. Moreover, the vibrational temperatures are further compared to results from a global thermal model and are in good agreement.Plasma-wall interactions in fluorocarbon based feedgas chemistries, namely CF4, are examined in a standard inductively coupled Gaseous Electronics Conference reference cell using in situ Fourier-transform infrared spectroscopy and microwave interferometry. Measurements show the dissociation of the CF4 feedgas into radical CFx species, as has been observed elsewhere [M. J. Goeckner and R. A. Breun, J. Vac. Sci. Technol. A 11, 3 (1993)], and qualitatively reveal a decrease in plasma-wall interactions as wall temperature is increased. Experimental results such as plasma density, 1011 cm−3, and CF4 density 1013 cm−3, are further compared to results from the hybrid plasma equipment model [R. Kinder and M. J. Kushner, J. Vac. Sci. Technol. A 19, 76 (2001)] to better elucidate the influence of wall temperature on plasma exposed surfaces and sticking coefficients. Last, CF4 vibrational temperatures were also measured, revealing that the line-averaged vibrational temperature remains at a constant 40–60 K above the...

Relationship between gas-phase chemistries and surface processes in fluorocarbon etch plasmas: A process rate model

In a typical plasma tool, both etch and deposition occur simultaneously. Extensive experimental measurements are used to help develop a general model of etch and deposition processes. This model employs reaction probabilities, or surface averaged cross sections, to link the measurable surface processes, etch and deposition, to the flux of various species to the surfaces. Because the cross sections are quantum mechanical in nature, this surface rate model should be applicable to many low temperature plasma processing systems. Further, the parameters that might be important in reaction cross sections are known from quantum mechanics, e.g., species, energy, temperature, and impact angle. Such parameters might vary from system to system, causing the wide processing variability observed in plasma tools. Finally the model is used to compare measurements of ion flux, ion energy, and fluorocarbon radical flux to the measured process rates. It is found that the model appears to be consistent with calculations of gain/loss rates for the various radicals present in the discharge as well as measured etch and deposition rates.

Role of chamber dimension in fluorocarbon based deposition and etching of SiO2 and its effects on gas and surface-phase chemistry

It is well understood that chamber geometry is an influential factor governing plasma processing of materials. Simple models suggest that a large fraction of this influence is due to changes in basic plasma properties, namely, density, temperature, and potential. However, while such factors do play an important role, they only partly describe the observed differences in process results. Therefore, to better elucidate the role of chamber geometry in this work, the authors explore the influence of plasma chemistry and its symbiotic effect on plasma processing by decoupling the plasma density, temperature, and potential from the plasma-surface (wall) interactions. Specifically, a plasma system is used with which the authors can vary the chamber dimension so as to vary the plasma-surface interaction directly. By varying chamber wall diameter, 20–66cm, and source-platen distance, 4–6cm, the etch behavior of SiO2 (or the deposition behavior of fluorocarbon polymer) and the resulting gas-phase chemistry change s...

Chemistry in long residence time fluorocarbon plasmas

The densities of radicals and neutrals in fluorocarbon (FC) plasmas have been investigated in an inductively coupled plasma system to understand the predominant gain and loss mechanisms of dissociative products and their interaction with chamber surfaces. The input parameters varied in this experiment are the source to chuck gap and the F: C ratio of the feed gas. The densities of F, CF2, CF3, CF4, C2F4, SiF4, COF2, CO, and CO2 are measured and analyzed. In addition, two different forms of C4F8, the standard cyclic c and a radical linear l structures are observed in C4F8 containing plasmas. l-C4F8 is shown to be the primary dissociation product of c-C4F8 and, thus, cannot be neglected from calculations of the loss rate of c-C4F8 to electron collisions. This implies that the typically cited dissociative products of c-C4F8 (primarily C2F4) can have dual production channels: one from l-C4F8 and the other directly from c-C4F8. Furthermore, the measured density of CF4 shows strong correlation to the loss of F ...

Effects of pore morphology on the diffusive properties of a porous low-κ dielectric

Porous methylsilsesquioxane-based spin-on films with pore sizes of 1.5–2nm and porosities ranging from 0% to 32% have been exposed to a variety of processing environments such as fluorocarbon or oxygen containing plasmas and TaN atomic layer deposition to determine the integratability of the films. The porosity of the low-κ films was found to decrease during processing due to tantalum and fluorine indiffusion (fluorine potentially depositing as fluorocarbon film in the pores) while oxygen indiffusion depleted carbon (possibly by forming volatile CO and CO2). Carbon removal from the low-κ film alters the film’s dielectric constant and refractive index. The depth of the indiffusion appears to be independent of diffusant (fluorocarbon, oxygen, or tantalum), ranging from 40to150nm, and to correlate directly to the pore structure. It was also found that water (moisture) in these films significantly affects the measured porosity as well as can be used to reduce the indiffusion of fluorine containing molecules b...