An all-wet process based on a novel chemistry has been developed to enable the removal of high-dose implanted photoresist in the presence of exposed metal layers and other materials typical of advanced gate stacks.

Scanning capacitance microscopy (SCM) has been used to generate two dimensional images of emitters formed using various doping techniques on polished and textured silicon photovoltaic cells. SCM has the advantage of high spatial resolution and sensitivity to carrier concentrations in the range of 10 14 - 10 20 cm -3 . The ability to image emitters on textured substrates allows evaluation of variations in emitter thickness in local regions due to the surface texture or doping technique as well as other processing steps such as metallization.

Photovoltaic devices were fabricated at IBM TJ Watson Research Center using a research line designed to run different substrate types concurrently. The process knowledge gained from CMOS IC fabrication is applied to solar cell fabrication to create cells with plated Cu front metallization, Al back contacts, and PECVD SiN ARC. The interaction between substrate type and process conditions for saw damage etch, PECVD SiN deposition and emitter formation (thermal budget exposure) is presented in this paper. Electroplating process characterization results are discussed. The effects on the electrical characteristics of the photovoltaic device due to the process parameters chosen, and due to extrinsic defects, are discussed.

A combination of wet chemistry and high-velocity solid CO2 aerosol pre-treatment was used to remove ion-implanted resist from patterned Si structures. The top resist surface is modified by heavy ion-implantation forming a crust ~100nm thick. The aerosol treatment, which is aimed at breaking and partially removing the crusted top layer of implanted resist, produces circular openings in this surface, with diameters on the order of tens to hundreds of micrometers. No resist is detected by either optical microscopy or localized SEM inspection, after immersion in hot SPM mixture, on aerosol-pre-treated wafer fragments. In contrast, resist residue is still observed on similarly pre-treated specimens, after immersion in either N-methyl pyrrolidone or Microstrip2001{trade mark, serif}, even under ultrasonic agitation. Overall, the aerosol pre-treatment is a key step in reducing the amount of resist residue, for both aqueous-based and solvent-based wet cleaning. Full-wafer defect-count results, post aerosol treatment, are reported for poly-Si line widths down to 40 nm.

The reactivity of copper toward liquid anhydrous hydrofluoric acid (AHF) has been examined using ex situ X-ray photoelectron spectroscopy (XPS). Exposure of either oxide-free or air-oxidized Cu surfaces to AHF yielded XPS spectra consistent with the presence of a CuF2 layer devoid of oxygen. Cyclic voltammetric experiments involving oxide-free Cu electrodes in hexafluorobutanol (HFB)+AHF displayed a prominent oxidation peak during the first few cycles. XPS analysis of Cu electrodes emersed at potentials positive to this feature provided evidence for the presence of a CuF2 layer much thicker than that found by simple immersion in AHF. Furthermore, the onset potential for both oxidation and subsequent reduction of the film was 0.0 V versus a Cu electrode in the same solution, which suggests that the Cu/CuF2 redox couple controls the potential of the reference electrode.

Certain aspects of the electrochemical fluorination (ECF) of hexafluorobutanol (HFB) in anhydrous HF (AHF) on Ni electrodes have been examined by mass spectrometry (MS) and X-ray photoelectron spectroscopy (XPS). Measurements were performed using a portable ultrahigh vacuum compatible chamber that allows for the transfer and characterization of specimens without exposure to the ambient atmosphere. Quasi on line MS analysis of the gases released during ECF of HFB/AHF solutions revealed features attributable to perfluorobutyryl fluoride [PBF = CF3CF2CF2C(O)F] with no evidence of the presence of other reaction products. Ex situ XPS analysis of Ni electrodes following ECF yielded spectra consistent with the formation of a rather thick, irregular layer of NiF2 of average thickness of about 150-200 monolayers, with small contributions due to O (6% ) and C (7%) localized primarily in the surface region. (C) 2001 The Electrochemical Society.

The reactivity of nominally clean polycrystalline Ni toward gas-phase and liquid anhydrous hydrofluoric acid (AHF) has been examined by X-ray photoelectron spectroscopy (XPS). To avoid contamination with atmospheric components, experiments were carried out using a portable ultrahigh vacuum (UHV)-compatible chamber to transfer Ni specimens between a UHV system that houses the XPS spectrometer and an additional UHV-compatible chamber where the actual exposures were performed.For exposures of ca. 10 minutes, the extent of surface oxidation of clean Ni to form NiF2, as calculated from Ni 2p and F 1s XPS spectra, was found to be significantly higher for gas-, compared to liquid-phase AHF. Thin (ca. 100 nm), mirror-like Ni films sputtered onto the surface of a sapphire disk yielded upon exposure to gas phase AHF (after contact with the laboratory atmosphere) scanning electron microscope images displaying a coherent, patchy structure with raised junctures. This behavior was ascribed to internal compressive stresses induced by the formation of a nickel (II) fluoride layer on the metal surface.

The electrochemical properties of clean aluminum in LiClO4(PEO) solutions have been investigated in ultrahigh vacuum using as electrodes both foils and thin films vapor deposited on boron-doped diamond (BDD) layers supported on Si substrates. Voltammetric scans recorded at temperatures of about 55 degrees C yielded a set of deposition/stripping peaks at potentials positive to the onset of Li/Al alloy formation, attributed to Li underpotential deposition on Al. The positions of these peaks were found to be in relatively good agreement with those predicted by Gerischer-Kolb's work function correlation, as well as with recent theoretical calculations reported by Lehnert and Schmickler. In the case of Al films supported on BDD/Si, the charge under the stripping peak obtained after polarizing the Al electrode at potentials slightly positive to Li bulk deposition was found to increase with the film thickness. Further optimization of this type of experiments, by using, for example, a quartz crystal microbalance to determine the actual amount of Al deposited on the BDD/Si substrate, will make it possible to measure the stoichiometry of the alloy as a function of the applied potential.