This paper describes in detail a surface preparation, and post-etch removal technique developed for InGaAs sidewalls. It illustrates the results demonstrating the effect of sidewall post-etch, surface preparation, and surface passivation on the performance of high speed InGaAs detectors. Dark current density for circular diodes with a diameter size varying between 10 and 100 μm was measured at a reverse bias voltage of −5 V. The effectiveness of various surface preparation techniques was studied by measuring the immediate improvement in dark current density, as well as its long-term stability. The benefits of this new technique compared to other techniques we have investigated include improved device characteristics, long-term stability, as well as a much less critical process to achieve optimum surface properties.

A methodology has been developed which provides a means of detecting and chemically characterizing low levels of contaminants in process gases used in the microelectronics industry. NVR monitors based on SAW (surface acoustical wave) technology were exposed to cylinders of a common gas used in microelectronics applications. A control cylinder of clean N2 was compared with a deliberately contaminated cylinder and two supposedly clean cylinders from different suppliers. The SAW devices were able to detect the residue deposited from each gas. After exposure to the cylinders, the SAW devices were directly analyzed by time-of-flight secondary ion mass spectrometry (TOF-SIMS) to identify the deposited residues. The TOF-SIMS instrument was equipped with a liquid-N2 cooled sample stage to facilitate detection of semivolatile species in the UHV environment necessary for the analysis.

Bi-surface photoconductivity decay (BSPCD) method has been useful to obtain the true bulk lifetime and surface recombination velocities in silicon wafers with variously finished surfaces. Thermally oxidized n-type CZ silicon wafers with and without a poly-Si back seal (PBS) were characterized with the BSPCD method using 500 MHz-UHF wave reflection. It has been found that the surface recombination velocity of the PBS surface is, 4027 cm/s while that of the no-PBS surface is 16 cm/s, for example. The very fast surface recombination velocity is attributed to the poly-Si / Si interface character. Moreover, the bulk lifetime calculated in the PBS wafer is much higher than that in the no-PBS one, which reveals the PBS gettering performance for the thermal oxidation induced contamination.

We have studied the thermal growth chemistry and bonding structure of three promising ultrathin (5–20Å), nitrogen rich passivation layers on Si(100), namely-Si3N4, NO/Si(100) grown oxynitride and NO annealed SiO2. These films are intended to serve as substrates with excellent diffusion barrier/interface properties during deposition of high- K dielectrics such as Ta2O5, with tSiO2 equivalent <30Å for ULSI applications. In this paper we show that it is possible to form films with a tailored composition and nitrogen profile using techniques that can easily be integrated with existing silicon processing technology. Alternating growth and surface analysis by X-Ray Photoelectron Spectroscopy (XPS) is used to non destructively characterize the growth.

The oxidation resistance of ultrathin (5–15Å) thermally grown silicon nitride (Si3N4), in conditions relevant to the deposition/annealing of Tantalum Pentoxide (Ta2O5) in a Rapid Thermal Processing (RTP) environment, has been non destructively examined using X-Ray Photoelectron Spectroscopy (XPS). This has been carried out with a view to establishing a process window for the deposition of Ta2O5 on a Rapid Thermally Nitrided (RTN) Si(100) surface, with negligible oxidation of the Si(100) substrate. A physical model of the oxidation process of these films is also proposed.

SurfaceSIMS depth profile measurements of dopants in silicon wafers with thin thermal oxide layers are presented. Complete and accurate calibration of these profiles requires layered data reduction to adjust for residual matrix effects of a factor of two in the sputter rate and SIMS relative sensitivity factor in SiO2 compared with bulk silicon. Properly calibrated profiles show good agreement with expected ion implant profile shapes, and can reveal dopant pile-up at SiO2/Si interfaces (phosphorus, for example). Measured SurfaceSIMS profiles of B doping within the first 10 nm of the substrate Si of experimental large area MOS capacitors show good agreement with dopant profiles independently obtained from experimental C-V data.

The influence of experimental geometry on the signal strength and signal-to-noise ratio of infrared spectrometry has been investigated. In general, it was found that the choice of optimum experimental geometry depended on the orientation of the vibrational mode being investigated. In particular, it has been calculated that internal reflection spectrometry is relatively insensitive to vibrational modes perpendicular to the surface relative to transmission spectroscopy at Brewster's angle, and this has been confirmed by experiment.

The oxidation of Si(111) and Si(100) surfaces with the high-purity ozone(more than 98 mole %) was investigated with X-ray photoelectron spectroscopy (XPS). Thin oxide less than 3nm thickens was formed in an experimental chamber and the results showed that ozone oxidizes the (111) surface faster than (100) surface. Ozone does not show the temperature dependence on oxidation within the temperature range of 250–500 degree C for both (111) and (100) surfaces. Ozone proceeds the oxide formation at 700 degree C where oxygen does not proceed oxide formation rapidly.

The influence of sheet electron beam irradiation ( SEBI ) on the water-wettability of the ( 100 ) plane on the Si wafer etched by hydrofluoric acid ( HF ) is investigated. The wettability energy is estimated from the contact angle of water. The SEBI treatment decreases the contact angle and increases the interfacial energy. Aging decreases the change in the interfacial energy. A rate process is inferred for the interfacial energy changes on the Si wafer.

A cleaning process using anhydrous HF (AHF)/methanol and ozone was carried out in a STEAG AST Vapor Phase Cleaning module (VPC). This module was integrated in a state-of-theart cluster tool also consisting of a STEAG AST Rapid Thermal Oxidation module (RTO). To investigate the properties of silicon after cleaning a novel in-line XPS module was integrated into the gate oxide cluster. Measurements of fluorine, carbon, and oxygen contamination in the range from 0.01 to 1 monolayers on cleaned wafer surfaces and on regrown oxides (< 0.5 nm) have been performed and used for rapid optimization of the cleaning procedure. The in-line integration enabled measurements without exposing the wafers to atmosphere thus avoiding oxidation or contamination of the wafer surfaces. To demonstrate the feasibility of this cluster tool for advanced gate dielectric formation, 4.0 nm thin oxide was grown directly after the cleaning in the RTO module without breaking the vacuum. Time dependent dielectric breakdown results for oxides pre-oxidation-cleaned in AHF, and in AHF followed by ozone were compared to a reference sample without any dry pre-oxidation cleaning. It could be shown, that the cleaning in AHF with a subsequent ozone step at 200°C under UV light lead to improved breakdown characteristics compared to AHF/methanol cleanings without such subsequent ozone/UV step or conventional wet cleaning using HF-Dip.

Trace organic contaminants adsorbing on silicon surfaces during transportation of wafers to a reaction chamber in an air ambient cause incubation before film growth starts in low-pressure chemical vapor deposition (LPCVD) of silicon nitride film on silicon substrates. The incubation time for wafers either exposed to cleanroom air for a long period without being stored in a box or stored in an outgassing plastic box prior to LPCVD is longer than that for wafers transported to the CVD reactor immediately after the previous step. It has been found that the longer incubation time is attributed to not only extraneous oxide grown on the silicon surface but also organic contaminants adsorbed on the surface.

The influence of fluorine atoms remaining after HF treatment on the adsorption of organic contaminants onto the surface of silicon wafers was investigated by analyzing the organic contaminants with gas chromatography-mass spectrometry following thermodesorption (TDGC/MS), and the surface composition with X-ray photoelectron spectroscopy (XPS). It has been found that residual fluorine on silicon surfaces after cleaning of the silicon wafers with either aqueous HF or anhydrous HF accelerates the adsorption of organic contamination onto the silicon surfaces. This would be due to the electrostatic force of attraction between the polar groups of organic compounds and the residual fluorine on the silicon surface.

Grazing-Emission X-Ray Fluorescence Spectrometry (GEXRF) is a new analytical X-ray fluorescence technique, which like TXRF takes advantage of the total-reflection phenomenon. The main advantage of GEXRF over TXRF is its sensitivity towards light elements. This paper presents straight GEXRF and VPD-DC-GEXRF analysis results for Na, Mg, Al, K and Ca surface contamination on silicon wafers.

This work describes recent progress in implementation and applications of synchrotron radiation total reflection x-ray fluorescence (SR-TXRF) to measure trace metals on wafer surfaces. To date, we have achieved state-of-the-art transition metal sensitivity of 3×108 atoms/cm2 (˜3fg) for 1000 sec. counting time for impurities which have an monolayer-like distribution on the surface and <1fg for droplet-like impurities. Recent instrumentation breakthroughs include reduction of detector parasitic backgrounds (particularly Cu) to below our present detection limit, 150 and 200mm whole-wafer handling, wafer-mapping capability and a cleanroom mini-environment. With these upgrades, measurements were made of wafers from various steps in the integrated circuit fabrication process. These results demonstrate that synchtron radiation brings TXRF into a new and useful regime. Further developments are underway to increase throughput and access for broader application.

Nucleation and growth of liquid drops from the vapor can be used to locate efficiently surface inhomogeneities such as topological defects, oxide patches, metallic impurities, organic contamination, and particles. In this study, nucleation of water drops was used to investigate the surfaces of copper-contaminated silicon substrates. Hydrogen-terminated silicon (111) substrates were dipped into copper-contaminated ultrapure water and exposed to supersaturated water vapor. The amount of copper deposited was varied by changing the strength of the solution. Nucleation occurred at vapor pressures close to saturation. Higher densities of nucleated drops appeared on areas with greater concentrations of copper. Using this technique, it was possible to detect copper concentrations as low as 6×1011 atom/cm2. Below this concentration, treated and untreated substrates could not be distinguished. The extreme sensitivity of the technique to background nucleants shows its potential for efficient screening of surfaces for a large range of inhomogeneities.

We report the formation of deuterium-terminated Si(111) and Si(100) surfaces in deuterated aqueous KF. The reaction of a deuterated Si(100) surface with H2O is investigated. We find that H2O etches the surface to give hydrogen termination and oxidized silicon hydrides. Hydrogenterminated surfaces react with various reagents under non-UHV conditions to form other covalent bonded species, including Cl-Si and Co(CO)4-Si. These species are characterized by polarized ATR and transmission FTIR. On Cl-Si(111) surfaces, Cl-Si is perpendicular to the surface. Chlorine-terminated Si(100) reacts with H2O to produce the hydrogen terminated surface. On Co(CO)4-Si(111) surfaces, one carbonyl is perpendicular to the surface, and the other three are approximately parallel to the surface.

The changes in X-ray excited valence band of silicon oxide during progressive oxidation of Si(111) surface in 1 Torr dry oxygen at 600–850°C were studied. Following results are obtained: 1) energy level of top of valence band within 0.9 nm from the SiO2/Si interface is different from that of bulk silicon oxide by about 0.2 eV, 2) valence band discontinuity at the interface changes periodically with the interface structures.

We have studied native oxide growth behavior on silicon surface with various resistivity in ultra pure water (UPW), SPM (sulfuric acid-hydrogen peroxide mixture, H2SO4:H2O2 = 4:1) cleaning and UPW contaminated with CuF2 by X-Ray photoelectron spectroscopy (XPS). The results show that the native oxide growth behavior in UPW is different from that in UPW contaminated with CuF2 and that grown by SPM cleaning. Native oxide thickness grown in UPW depends on resistivity. Native oxide thickness grown during SPM cleaning has the relationship of steric hinderance effect. However, in CuF2 solution, native oxide thickness is more influenced by the redox reaction between Cu ions and silicon atoms.

The correlation of contaminants in a process bath with contaminants on a silicon wafer prepared in the bath is important information when developing a cleaning strategy. In this paper, we present such a correlation focused on contaminants in dilute HF (1:100) and in SC1 (1:1:5 and 1:1:80 at 50°C and 65°C). We have limited the contamination levels to between 0 and 150 ppb. We have also limited the contaminants studied to those that are most likely to be a problem (Fe, Al, Mg, Ca, Cu, Zn, and Na). The bath concentrations are measured using ICPMS and the wafer surface concentrations are measured using both VPD/TXRF and VPD/ICPMS.

We demonstrate that Fe and Ca at the levels studied do not deposit from dilute HF, while Cu deposits, showing a linear dependence on bath concentration. We also demonstrate that in the SCl bath, both concentration and temperature are important variables in the contamination of wafers for a given bath contamination level. Al and Zn contaminate wafers most strongly, with Al being the largest contributor at the higher concentration of SC1 and Zn being the largest contributor in the lower concentration. Finally, we demonstrate that a dilute HF clean can remove everything deposited in a highly contaminated SC1 bath.

A gradual change in thermal oxide surface state from hydrophilic to hydrophobic was observed with time -delay in a clean room environment. Surface quality and reflectivity for the Al/Ti metal layers showed a strong dependency on the oxide surface state. From the hydrophilic oxide substrate, a lower (002) Ti preferred orientation was obtained than from hydrophobic ones. This resulted in a degraded (111) Al preferred orientation and rough metal surface. The RF-etch process increased the smoothness and hydrophobic surface property for the inter -metal dielectric (IMD) oxides, and therefore greatly improved Al/Ti surface quality. When conventional CMOS double layer metal interconnection process is performed, metal inter-line bridge yield was strongly affected by the surface state of substrate oxides.