Pre-gate Oxide Cleaning Research Articles

Very High Carrier Mobility for High-Performance CMOS on a Si(110) Surface

In this paper, we demonstrate CMOS characteristics on a Si(110) surface using surface flattening processes and radical oxidation. A Si(110) surface is easily roughened by OH- ions in the cleaning solution compared with a Si(100) surface. A flat Si(110) surface is realized by the combination of flattening processes, which include a high-temperature wet oxidation, a radical oxidation, and a five-step room-temperature cleaning as a pregate-oxidation cleaning, which does not employ an alkali solution. On the flat surface, the current drivability of a p-channel MOSFET on a Si(110) surface is three times larger than that on a Si(100) surface, and the current drivability of an n-channel MOSFET on a Si(100) surface can be improved compared with that without the flattening processes and alkali-free cleaning. The 1/f noise of the n-channel MOSFET and p-channel MOSFET on a flattened Si(110) surface is one order of magnitude less than that of a conventional n-channel MOSFET on a Si(100) surface. Thus, a high-speed and low-flicker-noise p-channel MOSFET can be realized on a flat Si(110) surface. Furthermore, a CMOS implementation in which the current drivabilities of the p-channel and n-channel MOSFETs are balanced can be realized (balanced CMOS). These advantages are very useful in analog/digital mixed-signal circuits.

Novel One-Step Aqueous Solutions to Replace Pregate Oxide Cleans

We have developed a number of novel solutions to use for one-step pregate oxide cleaning; they are based on tetraalkylammonium hydroxides of varying alkyl chain lengths, namely tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide (TPAH), and tetrabutylammonium hydroxide (TBAH). We added these surfactants together with ethylenediaminetetraacetic acid (EDTA) into the RCA SC-1 cleaning solution to enhance the efficiency of cleaning. With the exception of the TBAH solution, the cleaning efficiency of these solutions toward particles was 4%-7% higher than that of the conventional RCA method. Our cleaning methods have better efficiency toward the removal of Fe, Na, Ca, Cu, and Mn contaminants. We found that the conventional RCA method results in 10/sup 9/-10/sup 10/ atoms/cm/sup 2/ of Cu and Mn after cleaning. The electrical breakdown field of MOS capacitors was enhanced when using the new cleaning method. The literature model for surface adsorption and double-layer formation explains the cleaning behavior of the tetraalkylammonium ion-containing solutions. The removal of surface particles and metallic contaminants and the degree of surface roughness agree with the model's predictions. We believe that the best solution for use in one-step cleaning-one that comprises EDTA and TPAH-can replace the traditional RCA cleaning method. This new method has great potential for pregate oxide cleaning because it has the advantages of faster cycle times, lower costs, and greater efficiency.

One-Step Cleaning Solution to Replace the Conventional RCA Two-Step Cleaning Recipe for Pregate Oxide Cleaning

This work proposes an advanced wet chemical one-step cleaning process which omits the hydrochloric acid/hydrogen peroxide/water mixture (HPM) step in RCA. A novel one-step cleaning solution had been developed for pregate oxide cleaning to replace the conventional RCA two-step cleaning recipe, which used ammonia/hydrogen peroxide (or SC-1) and HPM (or SC-2) step. Tetramethylammonium hydroxide (TMAH) and ethylenediaminetetraacetic acid (EDTA) were added into the RCA SC-1 cleaning solution to enhance cleaning efficiency. From the experimental results, the particles and metallic contamination on the bare Si wafer surface could be removed significantly by applying this one-step cleaning solution. The effectiveness of various cleaning recipes and their interaction mechanism with silicon surfaces were studied. The surface adsorption and double layer models could explain the surface behavior of TMAH solutions. Based on the model, the particle, surface roughness and metallic contaminants can be realized. It was observed that the electrical properties of metal oxide semiconductor capacitors after cleaning with this novel solution were better than those after the conventional RCA cleaning. Besides, the cleaning method combining tetramethylammonium hydroxide, ethylenediaminetetraacetic acid, and at 80°C for 3 min showed high performance on particle removal, metal cleaning, surface smoothness, and electrical properties. Hence, this one-step cleaning process is very promising for future large sized silicon wafer cleaning due to the advantages of time-saving, low cost, and high performance. © 2001 The Electrochemical Society. All rights reserved.

Effect of Chemical Oxides Formed During Pre-Gate Oxide Cleaning on the Properties of Sub 20Ǻ Thick Ultra-Thin Stack Gate Dielectrics

Effect of Chemical Oxides Formed During Pre-Gate Oxide Cleaning on the Properties of Sub 20Ǻ Thick Ultra-Thin Stack Gate Dielectrics

Optimum Conditions for Novel One-Step Cleaning Method for Pre-Gate Oxide Cleaning Using Robust Design Methodology

A novel one-step cleaning method has been developed for pre-gate-oxide cleaning to replace the conventional RCA two-step cleaning process. Tetramethyl ammonium hydroxide (TMAH) and ethylenediamine tetraacetic acid (EDTA) are added into the RCA SC-1 cleaning solution to enhance cleaning efficiency. We adapt a robust design methodology (Genichi Taguchi method) to analyze the results of our experiments. Using this novel method, it is found that the optimum conditions are A1B2C1D1 (A1: TMAH:NH4OH=1:50, B2: EDTA concentration is 100 ppm, C1: cleaning time is 5 min, and D1: cleaning temperature is 60°C). This novel one-step cleaning method is very promising for future large-sized silicon wafer cleaning processes because it has the advantages of reduced processing time and temperature, cost reduction due to reduced chemical usage and improved performance.

Evaluation of Cleaning Recipes Based on Ozonated Water for Pre-Gate Oxide Cleaning

Evaluation of Cleaning Recipes Based on Ozonated Water for Pre-Gate Oxide Cleaning

In Situ Vapor Phase Pregate Oxide Cleaning and Its Effects on Metal‐Oxide‐Semiconductor Device Characteristics

Vapor phase cleaning of Si(100) surface in a cluster tool was studied. Electrical properties of the interface and the integrity of 55 Å films formed by in situ pregate oxide cleaning and rapid thermal oxidation (RTO) were characterized. Pregate oxide cleaning included anhydrous hydrofluoride (AHF) vapor for etching of native or sacrificial oxide, hydrocarbon removal, and trace metallic contamination elimination. Compared with a conventional wet cleaning procedure, in situ cleaning results in an equivalent interface and film with higher charge‐to‐breakdown . A two‐step cleaning procedure consisting of AHF etching and metal removal results in oxides with the highest .

A study comparing measurements of roughness of silicon and SiO 2 surfaces and interfaces using scanning probe microscopy and neutron reflectivity

Ultrahigh vacuum scanning tunnelling microscopy (UHV-STM) and air/liquid atomic force microscopy (AFM) have been used to evaluate the roughness of silicon surfaces after they have been subjected to pre-gate oxide cleaning. The pre-gate oxide cleaning procedure has involved the removal of the ‘native oxide’ with solutions of buffered HF (BHF) and dilute HF (DHF). The DHF treatment of Si {100} surfaces has been found by UHV-STM to give the smoothest surfaces for pre-gate oxidation in accord with HREELS and IR studies. A comparison of roughness measurement by UHV-STM relative to air/liquid AFM is given to elucidate the relative merits of those techniques which have different spatial resolution. The MOS gate oxide performance is correlated with pre-gate oxide silicon surface roughness. Data published on the Si SiO 2 interface roughness following growth of the gate oxide are inconsistent. A comparative study of interface roughness, determined with the gate oxide present, by neutron reflectivity experiments, and after removal of the gate oxide with DHF, by scanning probe measurements (SPM) is reported. Since the MOS performance may also depend on the SiO 2/contact interface roughness, roughness measurements of the SiO 2 gate oxide surface obtained using neutron reflectivity are also reported.

Pre-Gate Oxidation Cleaning of Silicon Wafer by Electric Arc Plasma Jet Treatment

ABSTRACTThe effect of arc plasma jet treatment (APJT) of silicon surface used for pre-gate oxidation cleaning on the electrophysical parameters of MOS structures (Si/SiO2/Si*/Al) has been studied- We show that APJT etching cleaning considerably improves the constant current charge to breakdown of MOS structures in comparison with conventional wet chemical cleaning. We have analyzed the effect of plasma cleaning conditions on the quality of gate oxide and SiO2/Si interface.

Effects of Pre-Gate Oxidation Cleaning and Gettering Upon The Very Thin Oxide Integrity

AbstractVarious pre-gate oxide cleaning and gettering techniques on the integrity of thin gate oxide were investigated. A 100 Å thick oxide capacitor was used to study its time-dependent breakdown characteristics and minority carrier lifetime. It has been shown that the oxide integrity as measured by time-dependent breakdown and the minority carrier lifetime are very sensitive to the cleaning technique. On the other hand, given adequate cleaning process, different intrinsic gettering schemes may only influence the oxygen precipitation, as well as the minority carrier lifetime, but not the oxide integrity.