Hidemitsu Aoki

Wafer Treatment Using Electrolysis-Ionized Water

Electrolysis-ionized water treatment is shown to be useful for removing polystyrene particles from contact holes, silicon surface cleaning and the removal of metal contamination such as copper. Electrolysis-ionized water has a controllable pH and a higher oxidation-reduction potential than chemicals. Moreover, this water does not contain acid or alkaline chemicals, and can easily be neutralized without adding chemicals. Electrolysis-ionized water treatment has great potential for ecologically safe and low cost semiconductor processing.

Improved field emission characteristics of individual carbon nanotube coated with boron nitride nanofilm

An individual multiwall carbon nanotube (CNT) synthesized without a catalyst by an arc discharge method is bonded to a tungsten tip. Field emission characteristics of the individual CNT coated with a boron nitride (BN) nanofilm are investigated. The BN film is synthesized by plasma-assisted chemical vapor deposition method in which boron trichloride (BCl3) and nitrogen (N2) are used as source gases. Deposition of the BN film with a thickness less than 10nm onto the individual CNT is attempted. Field emission characteristics are measured in the chamber evacuated to 2×10−8Pa. An anode electrode is set 25mm away from the CNT sample. The turn-on electric field, designated as an electric field at an emission current of 1.0nA, is compared between individual CNTs with and without the BN nanofilm. A significant reduction in the turn-on electric field is achieved by coating with the BN nanofilm. The turn-on electric field is estimated to be 1.2×10−2V∕μm for the uncoated individual CNT sample, and the turn-on elect...

Ag Diffusion in Low-

The diffusion of Ag and Cu in low-k films (BCN and SiOC) was investigated for future interconnections. From the depth profiles obtained by glow discharge optical emission spectroscopy (GDOES) after annealing, it was found that the rate of Ag diffusion in the BCN film was less than that in the SiOC film. It was also found that Cu diffused more easily in the SiOC film than in the BCN film. Current–voltage (I–V) characteristics were measured using a Ag or Cu electrode with and without annealing. The BCN film leakage current variation with and without annealing was less than that of the SiOC film. To improve RC delay time, Ag can be used because it has a lower resistivity than Cu; the BCN dielectric film can also be used because of its lower dielectric constant of 1.9 than that of the SiOC dielectric film.

k

Low-dielectric-constant (k) materials for large-scale integration (LSI) interconnect insulators are required to meet the fast development of high-speed devices. Introducing nanopores into dielectrics reduces their k effectively but also markedly degrades film strength (Youngs modulus). Developing a new low-k material is important for a stable integration with multilevel interconnections. We have investigated a low-k material of boron nitride containing methyl (methyl BN) using tris(dimethylamino)boron (TMAB) gas. This is the first report on the characteristics of a methyl BN film deposited using TMAB. We have succeeded in fabricating a low-k material with k 26 GPa. Moreover, the film can easily be etched using CF4 gas. The methyl BN film as a low-k material can readily be applicable to next-generation node technology devices.

Materials (BCN and SiOC) and Its Challenges for Future Interconnection

Thermal desorption spectroscopy (TDS) has been applied to detect contamination, produced in deep‐submicron contact holes during plasma etching. AlF and other Al‐containing fragments were observed as constituents of the contamination. The contamination is found to be accumulated in the holes, depending on an overetch time, acting as an inhibitor against achieving sufficiently low contact resistance. The effects of cleaning by Ar+ ion sputtering after contact‐hole fabrication are also investigated. The sputtering improves the contact resistance significantly. The sharp TDS peaks of AlF and AlC clearly decreased in good relation to the improvement in the contact resistance. The TDS method has proven to be an effective tool in evaluating contamination in the submicron contact holes.

Properties of Methyl Boron Nitride Film for Next Generation Low-k Interconnection

Abstract Amorphous silicon oxide (a-SiOx) films have been deposited by excimer laser-induced decomposition of an Si2H6N2O gas mixture. The films are characterized in terms of the oxygen composition, hydrogen content, refractive index, electron spin resonance spin density, breakdown strength and interface properties of the silicon metal-insulator-semiconductor structures as a function of the N2O-to-Si2H6 gas flow rate ratio. The annealing effects on the electron spin resonance spin density, breakdown strength and oxide charge density are also studied. Annealing at 450°C was found to be useful for improving the breakdown field and reducing the oxide charge density.

DIRECT ANALYSIS OF CONTAMINATION IN SUBMICRON CONTACT HOLES BY THERMAL DESORPTION SPECTROSCOPY

Quarter-micron interconnection technologies for 256-Mbit dynamic random access memories (DRAMs) are reviewed. Since the density of memory capacity is increased, both decreasing feature size and increasing sophistication of cell structures are required, resulting in three-dimensional structures. This trend leads us to the introduction of new interconnection technologies which have good coverage, low resistivity and high reliability, because the three-dimensional device structure requires high aspect-ratio contact hole plugs and narrow-pitch metal lines on different surface levels. The state of the art and current problems are discussed for quarter-micron contact-hole filling and quarter-micron interconnection lines.

Laser-induced chemical vapour deposition and characterization of amorphous silicon oxide films

Achieving high-performance and low-stand-by-power applications requires the integration of new metal gate materials and high-k dielectrics into LSI devices with the 45 nm technology node and beyond. The wet processes used for high-k removal involve a risk of enhanced galvanic corrosion at the gate electrode level. In this study, we investigated the galvanic corrosion between polycrystalline silicon (poly-Si) and metal in gate electrodes using organic solvents with hydrogen fluoride (HF). We succeeded in suppressing the corrosion of metal gates using a mixture of HF and isopropyl alcohol (IPA) with high selectivity for high-k/SiO2 in the front-end-of-line (FEOL) process for the fabrication of next-generation devices.

Quarter-Micron Interconnection Technologies for 256-Mbit Dynamic Random Access Memories

The effects of etching temperature and gases on the microloading and critical dimension (CD) shifts are investigated for Al etching using a SiO2 mask. Al etching with a SiO2 mask using Cl2 gas at low temperature achieved etching resistance against the mask, selective Al etching of underlying SiO2, suppression of microloading, CD shift, and after-corrosion. Al etching of 0.2 ?m was successfully achieved by using the SiO2 mask and Cl2 gas chemistry at low temperature.

Galvanic Corrosion Suppression of High-k/Metal Gates Using Organic Solvent-Based Hydrogen Fluoride

Features of thin strontium titanate (SrTiO3) films are a high dielectric constant (er) and chemical and structural stability. Submicron SrTiO3 patterning is necessary for realizing future planar dynamic random access memory (DRAM) structures to suppress parasitic capacitance. The etching technology and reaction with SrTiO3 film were investigated. It was found that the SrTiO3 film could be chemically etched by Cl2 and SF6 mixture gas, and 0.6 µm SrTiO3 patterns were etched by Cl2 with 10%-SF6 gases. In addition, the side wall deposition layer was removed by rinsing with CH3COOH, HNO3 and HF mixture solution.