James P. Doyle

Vapor deposition processes for amorphous carbon films with sp3 fractions approaching diamond

Trends in recently reported data on high sp3 fraction (up to 85%), nonhydrogenated amorphous diamond‐like carbon films deposited by ion beam sputtering and laser vaporization are examined. The degree of diamondlike film character is found to depend upon the deposition technique as well as the substrate temperature and thermal diffusivity. The data suggest that the combination of incident particle kinetic energy and surface accommodation determine the physical properties of the resultant film. A model is proposed for the condensation of energetic carbon atoms into diamondlike films in which a quench‐type surface accommodation mechanism is operative.

Sputter deposition of dense diamond‐like carbon films at low temperature

Thin carbon films were deposited by ion beam sputtering at temperatures of 77–1073 K. Using Rutherford backscattering spectrometry and electron energy loss spectroscopy, the trends in film density and bonding were examined as a function of deposition conditions. It has been found that film density and sp3 bonding character unexpectedly increased with increased substrate thermal conductivity and decreasing substrate temperature, reaching values of 2.9 g/cc and 50%, respectively.

Picosecond optical studies of amorphous diamond and diamondlike carbon: Thermal conductivity and longitudinal sound velocity

A picosecond pump‐probe technique is used to measure the room‐temperature thermal conductivity κ and longitudinal sound velocity cl of amorphous diamond (a‐D) and diamondlike carbon (DLC) thin films. Both κ and cl were found to decrease with film hydrogen content. Depending on the film deposition technique, κ is in the range 5–10×10−2 W cm−1 K−1 for a‐D, and 3–10×10−3 W cm−1 K−1 for DLC. Values of cl were found to be in the range 14–18×105 cm s−1 for a‐D, and 6–9×105 cm s−1 for DLC.

Properties of amorphous diamond films prepared by a filtered cathodic arc

Amorphous diamond films have been prepared by filtered cathodic arc deposition of carbon. The filtered arc is well suited for the growth of amorphous diamond, as it provides carbon ions with optimum kinetic energies at practical deposition rates. These films contain no hydrogen and are therefore structurally different from diamond‐like carbon films generated by plasma chemical vapor deposition. Diamond‐type bonding of carbon is quantitatively determined by electron energy loss spectroscopy, as an sp3 content up to 83% is measured. Data on the macroscopic properties are provided by optical transmittance, ellipsometry, Rutherford backscattering, elastic recoil scattering, and resistivity measurements. The films exhibit high optical transparency and an optical gap of 2.4 eV. Trends in the optical gap and refractive index as a function of deposition energy are consistent with semiconductor theory and indicates a change in the average bond length.

Low resistivity body‐centered cubic tantalum thin films as diffusion barriers between copper and silicon

Both bcc and β‐Ta thin films (50 nm) have been deposited onto (100) Si by dc magnetron sputtering at pressures between 4 and 7×10−2 Pa. Ta nucleates in the bcc structure when the substrate is at ground potential. However, when a negative bias voltage is applied, a mixture of bcc and β phases is formed. Below −100 V bias, only the β structure is observed. We conclude that ion bombardment during the deposition process plays an important role in the growth of the Ta films. We also compare the effectiveness of thin bcc and β‐Ta layers as diffusion barriers to copper penetration into Si. Ta films (bcc and β) were sputtered onto Si wafers (100) and overcoated with 150 nm of copper. Diffusion and reaction were monitored as function of temperature and time (up to 60 min) by four point resistance measurements and by Rutherford backscattering spectrometry. It has been observed that bcc Ta films exhibited no copper–silicon interdiffusion up to 650 °C, indicating that this Ta structure is a potential candidate for us...

Ion‐beam sputtered diamond‐like carbon with densities of 2.9 g/cc

Thin films of carbon have been deposited at temperatures ranging from 77 to 1073 K. It has been found that diamond‐like properties of the films change with the deposition temperature and the thermal conductivity of the substrate. Densities as high as 2.9 g/cc with an sp3 bond content >40% have been observed. Substrates that have been investigated include graphite, NaCl, Si, Al2O3, fused quartz, and diamond. Density measurements have been made using Rutherford backscattering spectrometry and electron‐energy‐loss spectroscopy while hydrogen profiling was conducted using forward recoil spectrometry.

Energetic carbon deposition at oblique angles

Carbon is energetically deposited by pulsed laser vaporization, cathodic arc and ion beam sputtering to provide amorphous diamond films with varying degrees of diamondlike quality. Laser and arc films prepared at normal particle incidence are high in sp3 content and electrical resistivity, and exhibit optical behavior comparable to diamond. As the incident angle of the depositing species becomes increasingly oblique, the diamondlike character is progressively degraded. This is verified by decreases in sp3 fraction, resistivity, and optical transmittance. These changes are accompanied by a roughening of the microstructure, but no apparent variation in the transmission electron diffraction pattern. For deposition at the most oblique angles, the development of biaxial stress anisotropy is observed, as the compressive stress measured along the direction of incidence decreases at a greater rate than along the perpendicular direction. The implications of these results on the mechanisms proposed for amorphous di...

Ion beam alignment for liquid crystal display fabrication

The ability to align liquid crystals to a substrate is a critical step in the liquid crystal display (LCD) manufacturing process with the industry standard technique employing a mechanical rubbing technique to accomplish this function. However, mechanical rubbing can result in debris generation contaminating not only the substrate being processed but also the clean room housing the equipment. As such, post-cleaning of the display panels is required to remove the debris from the surface in addition to the physical isolation of the mechanical rubbing equipment within the clean room environment introducing considerable time and expense. In addition, uneven wear of the mechanical roller during the rubbing process may result in localized defects that will not be observed until final inspection of a completely assembled display. We have developed and introduced into LCD manufacturing a non-contact alignment technique utilizing both diamond-like carbon (DLC) and a low energy ion beam (IB). The replacement of the polyimide alignment layer with DLC results in a completely dry processing technique for both the thin film deposition and alignment steps.

Effect of radical species density and ion bombardment during ashing of extreme ultralow-κ interlevel dielectric materials

The significance of ion impact and radical species density on ash-induced modification of an extreme ultralow-κ interlevel dielectric (ILD) material (κ<2.0) in a patterned single damascene structure exposed to Ar∕O2 and Ar∕N2 dual frequency capacitive discharges is determined by combining plasma diagnostics, modeling of the ion angular distribution function, and material characterization such as angle resolved x-ray photoelectron spectroscopy. Radical species density was determined by optical emission actinometry under the same conditions and in the same reactor in a previous study by the present authors. ILD modification is observed and correlated with changes in the plasma for a range of pressures (5–60mTorr), bias powers (0–350W), and percent Ar in the source gas (0%, 85%). For the Ar∕O2 discharge, extensive modification of the ILD sidewall was observed for significant ion scattering conditions, whereas minimal modification of the ILD sidewall was observed under conditions of minimal or no ion scatteri...

Looking into the crystal ball: future device learning using hybrid e-beam and optical lithography (Keynote Paper)

Semiconductor process development teams are faced with increasing process and integration complexity while the time between lithographic capability and volume production has remained more or less constant over the last decade. Lithography tools have often gated the volume checkpoint of a new device node on the ITRS roadmap. The processes have to be redeveloped after the tooling capability for the new groundrule is obtained since straight scaling is no longer sufficient. In certain cases the time window that the process development teams have is actually decreasing. In the extreme, some forecasts are showing that by the time the 45nm technology node is scheduled for volume production, the tooling vendors will just begin shipping the tools required for this technology node. To address this time pressure, IBM has implemented a hybrid-lithography strategy that marries the advantages of optical lithography (high throughput) with electron beam direct write lithography (high resolution and alignment capability). This hybrid-lithography scheme allows for the timely development of semiconductor processes for the 32nm node, and beyond. In this paper we will describe how hybrid lithography has enabled early process integration and device learning and how IBM applied e-beam & optical hybrid lithography to create the worlds smallest working SRAM cell.