Masafumi Kitano

Dependence of the Decomposition of Trimethylaluminum on Oxygen Concentration

Trimethylaluminum (TMA) is often used as a source gas for composite semiconductor or gate insulator films containing aluminum. However, TMA readily reacts with O 2 and this reaction causes film performance to degrade. Film formation is affected by the decomposition properties of the source gas, so it is important to investigate the influence of O 2 on the decomposition behavior of TMA. The starting decomposition temperature of TMA was 332°C in an Al 2 O 3 tube filled with Ar gas, and the decomposition rate increased rapidly above 380°C. However, when TMA was heated in an atmosphere containing more than 1 ppm O 2 , the temperature at which TMA began to decompose increased. It is assumed that this phenomenon resulted from the formation of methoxy groups through reaction between TMA and O 2 . Thus, the presence of O 2 in TMA not only caused the films to be contaminated with oxygen atoms but also altered the decomposition behavior of TMA. This means that fluctuations in the deposition rate and film performance are caused by the presence of O 2 in TMA when deposition conditions are otherwise kept constant. As a result, it is desirable that the O 2 concentration present in TMA is maintained below 0.1 ppm during deposition.

High-corrosion-resistant Al2O3 passivation-film formation by selective oxidation on austenitic stainless steel containing Al

We have developed Al2O3 passivation film having very high anticorrosion resistance on the surface of austenitic stainless steel containing 3 wt % aluminum. Al2O3 passivation film is formed by selective oxidation of aluminum in the austenitic stainless steel in the Ar and H2 ambient including a small amount of H2O at predetermined temperatures. Al2O3 film is obtained at temperatures higher than 750 °C in the Ar and H2 ambient, where the partial pressure ratio of H2 and H2O is set higher than 2×103. Al2O3 films have been confirmed to exhibit very high anticorrosion resistance for various halogen gases and various plasma ambients (Cl2, H2, and O2) with ion-bombardment energies less than 100 eV at temperatures less than 150 °C. In the case of fluorine-gas plasma, the Al2O3 film surface has been converted to AlF3 with a depth of 15 nm, where AlF3 film is thermodynamically stable, as well as Al2O3, resulting in an excellent passivation film exhibiting very high anticorrosion capability. Moreover, the Al2O3 film...

Impurity Measurement in Specialty Gases Using an Atmospheric Pressure Ionization Mass Spectrometer with a Two-Compartment Ion Source

Using an atmospheric pressure ionization mass spectrometer (APIMS) with a two-compartment ion source, impurity in specialty gases (CH4, SiH4, GeH4) is measured due to a stable ionization reaction with a detection limit of approximately 0.1 to 1 parts per billion (ppb). The form in which the impurity exists in these gases has been clarified. In the case of SiH4, the main impurity is disiloxane (SiH3–O–SiH3). We have also established a method for obtaining the SiH3–O–SiH3 calibration curve standardized for a known concentration of SiH3–O–SiH3 generated from the reaction of SiH4 with H2O. In the case of CH4 and GeH4, the main impurity is moisture (H2O) and it is quantified from the plotted H2O calibration curve.

An Outgas Free Passivation Technology for Semiconductor Vacuum Chamber using Advanced Anodic Oxidation

In order to apply the aluminum alloy to the semiconductor vacuum chamber, appropriate passivation surface process is essential. Following characteristics are required for the passivation film of advanced semiconductor chamber. 1) no outgas(H2O) 2) no heat crack 3) no corrosion by the process chemicals 4) no damage by the plasma irradiation 5) no catalyst effect to the decomposition of the process gas

Development of Barrier Anodic Oxide Al2O3 Passivations of Aluminum Alloy Surface for LSI/FPD Plasma Process Equipment

Aluminum alloys are key materials for advanced large-scale integration (LSI)/flat panel display (FPD) plasma process equipment to drastically improve the process performance. There exists a severe disadvantage for aluminum-alloy process chambers, however, i.e., very poor anticorrosion capability to halogen gas plasmas. Thus, the authors have developed very advanced Al 2 O 3 passivation films having a thickness of 0.1-0.4 μm on aluminum-alloy surfaces exhibiting complete anticorrosion resistance for various radicals such as hydrogen radicals H*, oxygen radicals O*, halogen radicals (Cl*,Br*,F*), and simultaneously various ion bombardments by using nonaqueous anodic oxidations. Porous alumite (alumilite) films having a thickness of 50-200 μm have been provided on aluminum-alloy chamber surfaces as anticorrosion films using aqueous anodic oxidations, particularly for reactive ion etching process chambers. But alumite films (Al 2 O 3 nH 2 O) include huge amounts of water molecules, resulting in the generation of water vapors in the process chamber and leading to the degradation of process quality and the generation of too many particles in the process chamber coming from water-molecule-originated gas-phase reactions. 1 Plasma process performance of LSI/FPD manufacturing is drastically enhanced by introducing a newly developed Al 2 O 3 passivated aluminum-alloy chamber to overcome all disadvantages of current plasma process equipment.

A Defect-Free Anodic Oxide Passivation for LSI/FPD Vacuum Chamber

Aluminum alloys were anodized in nonaqueous electrolyte solution and surface microroughness of anodic oxide grown on the alloys in nonaqueous electrolyte solution is found by far less than that grown in aqueous electrolyte solution. Barrier type anodic oxides on high-purity Al/Mg/Zr(AlMg2) alloys in nonaqueous solution are found to feature excellent characteristics: no voids or seams are formed, outgas from anodic oxides is very much limited, they feature outstanding resistance to process gases. Anodization of AlMg2 alloys in nonaqueous electrolyte solution will be promising surface passivation of LSI/FPD vacuum equipments.

Precise Control of Gas Concentration Ratio in Process Chamber

A new system for controlling gas concentration in a process chamber was developed using a combination of a new flow controller and a gas pumping system. The new flow controller does not exhibit overshooting; thus, a stable gas flow rate can be realized in a process chamber after valve operation. Furthermore, very rapid gas displacement in the chamber can be realized by combined gas flow system and pumping system. As a result, it took only 2 s to stabilize chamber pressure and gas composition from purge gas to process gases using Fourier transform infrared spectroscopy (FT-IR) method. It is possible to control process parameters such as gas concentration and working pressure during the entire process using this system.

The Degradation Prevention of Resin Materials for Semiconductor Manufacturing Equipment by Applying the Ultra-High Purity Gas Supply Technology

The production (molding) guideline to realize ultraclean resin components for semiconductor equipment has been established. In this paper, we focused on the degradation behavior of resin materials for the purpose of reducing low-molecular-weight volatile contaminants concentration in resin components because the molding is carried out at high temperature and low-molecular-weight volatile contaminants are produced by thermal degradation. It was clarified that the oxygen concentration in high temperature molding environment is required to be below 1 ppm. And as the contact surface of the thermal degradation prevention for the resin material, the following surface materials are effective. 1) Passivation surface for a hydrocarbon resin. 2) Ni (nickel) surface for a fluorocarbon resin. As a result, we found the degradation prevention of the resin material can be realized until around 400°C although the degradation was observed even under 200 °C if using current process condition. Therefore, low-molecular-weight volatile contaminants can be drastically reduced from resin components by using the guideline and ultraclean semiconductor equipment must be realized.

Adsorption Behavior of Various Fluorocarbon Gases on Silicon Wafer Surface

An analytical technique to clarifying the adsorption behavior of a fluorocarbon gas, which is one of the key steps in reactive ion etching, has been established. In this paper, we focus on the adsorption behavior of fluorocarbon gases to the silicon wafer surface to clarify the etching mechanism in order to realize etching to a high aspect ratio. Each fluorocarbon gas had surface selectivity for SiO2, Si and the photoresist. Each fluorocarbon gas reacted differently at the silicon wafer surface. As a result, the etching mechanism could be clarified using this newly established analytical technique. Therefore, an etching mechanism will be able to be clarified by applying the newly established analytical technique to the fluorocarbon gases expected to be useful for etching of high aspect ratio and further high performance ultra large scale integrated circuit device must be realized.