Joffre F. Bernard

Self-aligned nickel, cobalt/tantalum nitride stacked-gate pMOSFETs fabricated with a low temperature process after metal electrode deposition

This letter reports the first replacement (Damascene) metal gate pMOSFETs fabricated with Ni/TaN, Co/TaN stacked electrode, where Ni or Co is in direct contact with the gate SiO/sub 2/, to adjust the electrode metal work function and TaN is used as the filling material for the gate electrode to avoid wet etching and CMP problems. The process is similar to the fabrication of traditional self-aligned polysilicon gate MOSFETs, except that in the back end (after the source/drain implants are activated) a few processing steps are added to replace the polysilicon with metal. Our data show that the Ni or Co/TaN gate electrode has the right work function for the pMOSFETs. The metal gate process can reduce the gate resistivity. Thermal stability of the stacked electrodes is studied and the result is reported in this paper. The damascene process flow bypasses high temperature steps (> 400/spl deg/C)critical for metal gate and hi k materials. This paper demonstrates that a low temperature anneal (300/spl deg/C) can improve the device performance. In this paper, the gate dielectrics is SiO/sub 2/.

Impact of photo-induced species in O2-containing gases on lithographic patterning at 193-nm wavelength

In order to prevent contaminants and impurities from being deposited on the optical elements of the tool, ArF lithographic patterning of photoresists is currently done in the exposure chamber of a scanner or stepper that is purged with clean dry air. Unfortunately, the 6.4 eV (193 nm) ArF laser photons can dissociate molecular oxygen in air into atomic oxygen, form ozone, form singlet molecular oxygen and atomic oxygen from the photodissociation of ozone, and mediate singlet molecular oxygen formation in polymers by energy transfer mechanisms from impurities or specially added sensitizers (S) (e.g. dyes). Once formed, these species mediate photo-oxidative degradation processes of resist polymers, including cross-linking, chain scission, oxidation, and other secondary reactions by free radical mechanisms, resulting in resist feature erosion, poor resist feature profiles, particularly under bright field illumination in full field scanners and steppers. The occurrence of these photo-oxidative degradation processes has been experimentally verified in photoresist films exposed in commercially available ArF laser scanners and steppers that are purged with clean dry air. Using a custom-built ultra-high vacuum (UHV) chamber equipped with ArF laser beam line, mass spectrometer, and infra-red spectrometer, as well as an ex-situ X-ray photo-electron spectrometer and a Fourier Transform infra-red spectrometer, the effects of different exposure environments (dry air, nitrogen, oxygen, ozone/oxygen mixture, and vacuum) in either contributing to or mitigating these photo-oxidative degradation processes during exposure of photoresist films were studied. The effects of these photo-oxidative degradation processes have been quantified, and it was observed that the processes are initiated at the surface of resist polymers by photo-induced species, and proceed inwards, giving rise to a gradient of deteriorated material across the specimen thickness.

Bottom anti-reflective coatings: fluid property characterization and wetting tendency

This series of studies focuses on the fundamental fluid properties of several commercially available bottom anti- reflective coatings (BARCs). A goniometer was used to complete pendant drop analysis and dynamic contact angle measurement for two similar varieties (A-1 and A-2) of a 248nm BARC and another, competing variety (B-1) of a 248nm BARC. The pendant drop analysis shows that the liquid surface tension of the three BARCs is identical. The contact angle analysis was performed on SiON, low k dielectric, and F-based oxide type layers. Contact angle analysis shows that B-1 wets the least quickly, A-1 wets the most rapidly, and A-2 wets at an intermediate rate. All three wet quickly, A-1 and A-2 completely wet the surface, and B-1 nearly does. The surface type does not seem to affect the wetting rate, despite a real difference in the chemistry of the surface, as shown by the different surface energies of the materials. A Newman-type polymer-spreading model is proposed for the BARC spreading and shown to offer reasonable explanation of the wetting process. Three wafers, one for each BARC, were coated with resist and BARC and then stripped. The stripping process appears to have no major effect on the SiON and F- based oxide surfaces. However, the stripping process modifies the low k dielectric surface in an unknown way, making it more hydrophilic, which causes A-1 and A-2 BARCs to spread less well. Three wafers, one for each BARC, were subjected to a 20 degree(s)C/minute bake over the temperature range 50-220 degree(s)C in a mass spectrometer. The analysis shows that A-1 BARC exhibits the most outgassing, that A-2 BARC exhibits an intermediate level of outgassing and that the B-1 exhibits the least level of outgassing. In general, the B-1 peaked at substantially lower levels. The analysis shows that water vapor forms the largest component of the evolved gas. A-1 BARC causes the most water outgassing. The A-2 BARC, being substantially more viscous than the A-1 BARC, coats much thicker. The thickness is related to the spin speed by an inverse power relationship, where the power is -0.419.

Characterization of Ti/TiN Films and SiO2/Ti Interfaces by Use of X-Ray Photoelectron Spectroscopy

The deposition and processing of thin films, such as barrier metals and anti-reflective coatings, can be enhanced using the information provided by various surface analysis techniques. We will show the application of x-ray photoelectron spectroscopy(XPS) to the production of Ti and TiN films suitable for use in ULSI CMOS integrated circuits. XPS can separate Ti and N photoelectron peaks and detect low (1.0-5.0 atomic%) contamination levels while providing surface and interface chemical state information. In this paper we will show that a) the effect of TiN deposition on subsequent Ti film quality from the same Ti target was determined to be minimal, b) the relation of anneal temperature to the extent of SiO 2 reduction by Ti metal was characterized on SiO 2 /Ti/TiN structures for temperatures from 600°C to 800°C, and c) the absorption of O into TiN films from ambient air was detected and confirmed.