Oxide Regrowth Research Articles

Adsorption of Mixed Peptide/Thiol Adlayers on InAs: Assessment of Different Functionalization Strategies Using X-ray Photoelectron Spectroscopy

Mixed adlayers are commonly used to create surfaces with multiple functional groups or molecular gradients. The resulting surfaces are designed to have the combined effects of each adsorbed functional group. In this work, we combine the passivation ability of a thiol with the functionality of a peptide by assembling mixed peptide/thiol adlayers on InAs. Both sequential (insertion) and simultaneous (co-assembly) methods are used to functionalize InAs and are analyzed by contact angle measurements and X-ray photoelectron spectroscopy (XPS). Peptide coverage, thiol coverage, and oxide layer thicknesses are estimated from XPS data. For each method, oxide layer thicknesses were significantly lower than the oxide thicknesses for as-received samples. Surfaces functionalized using the insertion methods had lower oxide layer thicknesses than peptide only samples, indicating that the addition of the thiol helped block oxide regrowth. Functionalization with the thiol followed by the peptide yielded surfaces with the...

Characteristics of Hafnium Silicate Films Deposited on Si by Atomic Layer Deposition Process

We investigated the effects of annealing (i.e., temperature and time) on the characteristics of hafnium silicate () films deposited on a Si substrate by atomic layer deposition process (ALD). We found that the post deposition annealing under oxidizing ambient causes the oxidation of residual Hf metal components, resulting in the improvement of electrical characteristics (e.g., hysteresis window and leakage current are decreased). In addition, we observed the annealing temperature is more important than the annealing time for post deposition annealing. Based on these observations, we suggest that post deposition annealing under oxidizing ambient is necessary to improve the electrical characteristics of films deposited by ALD. However, the annealing temperature has to be carefully controlled to minimize the regrowth of interfacial oxide, which degrades the value of equivalent oxide thickness.

Electrical analysis of three-stage passivated In0.53Ga0.47As capacitors with varying HfO2 thicknesses and incorporating an Al2O3 interface control layer

The atomic layer deposition of high dielectric constant oxides like HfO2 on III-V substrates such as In0.53Ga0.47As leads to a poor interface, with the growth of In0.53Ga0.47As native oxides regardless of the surface pretreatment and passivation method. The presence of the native oxides leads to poor gate leakage current characteristics due to the low band gap of the native oxides and the presence of potential wells at the interface. In addition, the poor quality of this interface leads to very large interface state defect densities, which are detrimental to metal-oxide-semiconductor-based device performance. A wide band gap interlayer replacing the native oxide layer would remove the potential wells and provide a larger barrier to conduction. It may also assist in the improvement of the interface quality, but the problem remains as to how this native oxide interlayer cannot only be removed but prevented from regrowing. In this regard, the authors present electrical results showing that the atomic layer deposition (ALD) growth of a thin (∼1 nm) Al2O3 layer before the ALD growth of HfO2 causes a removal/reduction of the native oxides on the surface by a self-cleaning process without subsequent regrowth of the native oxides. As a result, there are significant improvements in gate leakage current densities, and significant improvements in the frequency dispersion of capacitance versus gate voltage, even when a defective In0.53Ga0.47As epitaxial layer on an InP substrate is employed. Measurements at different temperatures confirm that the frequency dispersion is mainly due to interface state defect responses and another weakly temperature dependent mechanism such as border traps, after accounting for the effects of nonideal In0.53Ga0.47As epitaxial layer growth defects where applicable.

Development of ALD HfZrOx with TDEAH/TDEAZ and H2O

In this work we report on the development of the atomic layer deposition (ALD) process with tetrakisdiethylamino (TDEA) hafnium/zirconium (TDEAH/TDEAZ) and . A nanolaminar structure approach is used to grow by alternating and ALD reaction cycles at . The film thickness increases linearly with the number of ALD cycles. Compared to the halide based process, the process with TDEA precursors and yields a lower temperature window, an initial growth insensitive toward the starting surfaces, and a fast film closure on the hydrofluoric acid-last surface. The Zr content, measured by Rutherford backscattering increases linearly with the cycle ratio of . The as-deposited films are amorphous and crystallize after a postdeposition anneal. Depending on the film composition a different crystalline phase is formed, ranging from monoclinic to tetragonal with increasing Zr content. Using instead of not only reduces the interfacial oxide regrowth during deposition, which allows for a thinner interfacial layer and improves the interfacial oxide scalability, but also results in a lower C content in the deposited films. Finally, complementary metal oxide semiconductor transistor using as gate dielectric are fabricated for the evaluation of device performance. These results show that all considered splits with as gate dielectric yield a similar equivalent oxide thickness-gate leakage current performance and (low) gate current leakage level. The data reported in this paper demonstrates that ALD grown based on and is a promising gate dielectric for subnanometer equivalent oxide thickness scaling.

High Productivity Combinatorial Analysis of Cu Post-CMP Cleans: Corrosion Protection and Queue Time

High Productivity Combinatorial (HPC) technology was used to evaluate post-CMP clean chemistries and their impact on copper surface corrosion protection and queue time performance. Cleaning formulations at low pH and high pH, both with and without functional additives, were used to produce a wide range of surface conditions typical in semiconductor processing. X-ray photoelectron spectroscopy (XPS) results show that low pH cleans remove most oxides, but that within 20 hrs copper oxide re-growth occurs in the form of Cu (I) and Cu (II) oxide species. Electrochemical analysis is a simpler and higher throughput method to study oxide growth over time. Good agreement existed between electrochemical and XPS techniques when both were used to study copper surfaces for 0 to 20 hours after clean. The electrochemical tests were continued after 48 hours of queue time to develop a better understanding of oxide growth trends, and showing continued oxidation of Cu surfaces treated with low pH cleans. For extremely long queue times, SEM analysis shows growth of visible copper oxide nodules on Cu lines and pads for low pH treated M1 test structures. Leakage of comb structures monitored as a function of queue time was inconsistent, indicating that standard leakage measurements at 1V for comb structures with 0.125 / 0.175 line/space dimensions are not sensitive to the copper surface instability of oxidation.

Impact of nitrogen post deposition annealing on hafnium zirconate dielectrics for 32 nm high-performance SOI CMOS technologies

The impact of either N 2 or N 2/O 2 Post Deposition Annealing (PDA) and Post Work Function Annealing (PWFA) combinations as well as single N 2 or N 2/O 2 PWFA with different process parameters on HfZrO 4 has been investigated in detail for high performance 32 nm SOI CMOS devices. Electrical parameters such as leakage current, capacitance equivalent thickness (CET), threshold voltage and performance as well as reliability data have been taken into account in order to evaluate these treatments. N 2/O 2 annealing results in severe oxide regrowth due to the presence of oxygen in the annealing ambient. A detailed investigation on the impact of N 2 PWFA has been performed. Finally significant gate leakage current benefit, performance and reliability improvements are demonstrated especially for the N 2 PWFA treatments in combination with HfZrO 4.

Electrical properties and structure of laser-spike-annealed hafnium oxide

We studied the effects of laser-spike annealing (LSA) on hafnium oxide high-k dielectrics using high power diode laser. The equivalent oxide thickness of HfO 2 gate stacks annealed using a moderate laser power decreased noticeably as compared to as-grown films due to densification and crystallization of HfO 2. Transmission electron microscope and X-ray photoelectron spectroscopy show that regrowth of interfacial oxide and silication of HfO 2 layer are suppressed in case of LSA compared with rapid thermal annealing. Capacitance voltage hysteresis revealed stronger charge trapping/de-trapping behavior for LSA gate stacks as compared to rapid thermal annealed gate stack. However, bias-stress-induced flat band voltage shifts of LSA gate stacks were within acceptable levels, ≲ 30 mV, showing controllable threshold voltage.

Controlled etching and regrowth of tunnel oxide for antenna-coupled metal-oxide-metal diodes

The authors have designed a new procedure for fabrication of infrared (IR) sensors. These sensors consist of a dipole antenna coupled with a metal-oxide-metal (MOM) (Al–AlOx–Pt) diode. The surface of electron beam evaporated Al, serving as one of the electrodes, is cleaned using an Ar plasma, followed by in situ controlled growth of the tunneling oxide, AlOx. The antenna, its leads, and the overlap of the Al and Pt electrodes that defines the MOM overlap area are all defined using electron beam lithography. The MOM overlap area of these devices is as small as 50×80 nm2. Features of our process include the use of dissimilar metals for the formation of the MOM diode, small MOM diode size, and controlled etching and regrowth of the tunneling oxide. A CO2 laser at 10.6 μm was used for the IR characterization of these sensors. Current-voltage and IR measurements are presented. The normalized detectivity (D∗) for these devices was found to be 2.13×106 cm Hz1/2 W−1.

NdSrNi0.8Cu0.2O4−δ thin films epitaxially grown by pulsed laser deposition on LaAlO3 and SrTiO3: A potential electrode for epitaxial regrowth of perovskite structure-based oxides

NdSrNi0.8Cu0.2O4−δ (NSNCO) thin films were grown by pulsed laser deposition (PLD) on LaAlO3 and (110)SrTiO3 substrates. NSNCO thin films were (00l) and (103) oriented on (100) LaAlO3 and (110)SrTiO3, respectively, as evidenced by the θ−2θ X-ray diffraction. The high crystalline quality was illustrated by low value of rocking curve (Δω=0.1–0.5° for (00l) films and about 1° for (103) films). In-plane ordering was probed by X-ray diffraction ϕ-scans, evidencing the epitaxial growth on both substrates. The microstructure of films investigated by scanning electron microscopy was strongly influenced by deposition conditions. Four probe electrical resistivity measurements were performed versus temperature in the range 77–300K. The resistivity was found to be 0.004Ωcm at room temperature. Some bilayers combining a ferroelectric oxide and NSNCO, i.e. SrBi2Nb2O9 (SBN) and NdSrNi0.8Cu0.2O4−δ, were grown by PLD on both substrates. The possibility to control (00l)- and (116)-oriented epitaxial SBN thin films was proved by the X-ray diffraction analysis.

Instability of anodically formed TiO 2 layers (revisited)

On the occasion of the 4th Gerischer Symposium, a remarkable Ti anodising experiment first reported in 1978 by Di Quarto, Doblhofer and Gerischer has been reproduced. The key observation of the original experiment was the presence of a fast cell voltage decay occurring when the current during galvanostatic Ti anodising was decreased below a critical, low threshold value. In order to reveal the origin of this instability, which at the time was suggested to be mechanical in nature, chronopotentiometric data have been combined with high resolution in situ curvature measurements, the latter allowing to monitor the internal stress evolution during anodising. Our synchronised in situ electrochemical and curvature measurements have confirmed for the first time the previously assumed sequence of phenomena underlying the reported instability (O 2-evolution, oxide swelling, oxide delamination and oxide regrowth) through their mechanical consequences (curvature noise, electrostriction jumps and growth stress transitions). However, no evidence could be obtained as to a possible mechanical origin of the instability itself. Instead, based on detailed SEM and TEM inspection, a link with the microstructural evolution has been establised, involving the presence of anatase micro-crystals in the early stages of anodising. Local gas evolution at these anatase crystals is then believed to lead to the gradual appearance of open, crater-like defects on the oxide surface, which in turn allow for electrolyte penetration during the voltage decay when gas evolution at these surface features has stopped.

High-Temperature Oxide Regrowth on Mechanically Damaged Surfaces

X-ray elemental maps are used with single-point abrasion tests of a nickel-based superalloy, exposed to air at 850 °C, to demonstrate how high-temperature oxidation products form differently on damaged and non-damaged tribosurfaces. These findings complement previous work on the nature of sliding combined with oxidation. Results have implications for modeling the wear processes of exhaust valves in internal combustion engines.

Advanced Surface Preparation Development on a 300 mm Single Wafer Spin-on Platform

Focus has been made on the so-called "Leti BKM-Clean" advanced surface preparation, developed on a 300 mm single wafer spin-on platform. Based on the "Dilute Dynamic Clean" (DDC) knowledge [1], dilute HF/HCl and O3/HCl chemistries have been investigated here in combined spin-on and immersion mode. Depending on the specific FEOL cleaning step requirements, the HF/HCl step can be tuned in order to precisely control the partial or total silicon surface de-oxidation as for pre-gate cleanings which require a controlled chemical oxide re-growth. In this last case, the Leti BKM-Clean presents good particle performance up to 65 nm particles size, good particle and metallic removal efficiency without any feature damage generation on high-K /TiN/poly-Si lines structures with an aspect ratio lower than 4.

Molecular Self-Assembly at Bare Semiconductor Surfaces: Investigation of the Chemical and Electronic Properties of the Alkanethiolate−GaAs(001) Interface

High-resolution X-ray photoelectron spectroscopy (HRXPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and Raman scattering have been used to characterize the bonding and electronic properties of the interfaces formed by ambient-temperature, solution self-assembly of octadecanethiol and dodecanethiol under oxygen-free conditions on GaAs(001) surfaces. The combination of HRXPS and ToF-SIMS shows that both monolayers form direct S−[GaAs] attachment to the bare substrate with dominant As−S bonding and some fraction of Ga−S bonding, but the densely packed octadecanethiolate self-assembled monolayers (SAMs) are significantly more effective in protecting the interface from oxide regrowth compared to the less dense dodecanethiolate SAMs. Raman scattering measurements of the GaAs LO phonon modes indicate that the formation of these direct, oxide-free S−[GaAs] interfaces does not induce any significant changes in the GaAs surface electronic states, whereas control experiments with inorganic sulfide t...

In situ second-harmonic generation measurements of the stability of Si(111)–H and kinetics of oxide regrowth in ambient

The oxidation of H terminated silicon surfaces is a significant and controversial problem in silicon device fabrication. Second-harmonic generation rotational anisotropy (SHG–RA) provides a convenient means to monitor the chemical state of the Si surfaces, and to follow the conversion of H terminated surface to SiO2 by oxidation as a function of time in ambient. The change in SHG–RA of Si(111)–H was shown to correlate well with the ellipsometric thickness. SHG is sensitive to the initial stage of oxidation (induction period) as well as to the logarithmic oxide growth. SHG is sensitive to the electronic properties of the surface, therefore it is a sensitive probe of the quality of H terminated Si(111) surface. Under ambient conditions, (20% relative humidity, 23 °C) the initial oxidation rate is at most 2×10−6 ML/s.

Cleaning of Si and properties of the HfO2–Si interface

The effectiveness of modified Shiraki and RCA cleans on the properties of HfO2 gate dielectric and its interface with silicon has been investigated. Modified Shiraki clean provides atomically flat and more completely hydrogen terminated Si surfaces resulting in sharper low energy electron diffraction images and longer inhibition times for native oxide regrowth. Capacitors based on HfO2 deposited by reactive electron beam evaporation under O2 partial pressure and annealed in H2 atmosphere show different properties, dependent on the cleaning method. Capacitance–voltage curves obtained on RCA cleaned samples show lower capacitance and higher distortion than those of modified Shiraki samples. Analysis of capacitance–voltage curves implies higher density of interfacial traps in RCA cleaned devices and thicker interfacial oxides compared to modified Shiraki clean, resulting in higher effective oxide thickness of the dielectric stack.

Limiting Native Oxide Regrowth for High-k Gate Dielectrics

AbstractA cleaning process resulting in atomically smooth, hydrogen-terminated, silicon surface that would inhibit formation of native silicon oxide is needed for high-k gate dielectric deposition. Various cleaning methods thus need to be tested in terms of resistance to native oxide formation. Native oxide re-growth is studied as a function of exposure time to atmospheric ambient using ellipsometry. Hafnium dioxide film (k ~23) is deposited on the as-cleaned substrates by electron beam evaporation and subsequently annealed in hydrogen. The difference in the effective oxide thickness re-grown on surfaces treated with the conventional RCA and modified Shiraki cleaning methods, after one-hour exposure, can be as large as 2 Å. This is significant in device applications demanding equivalent oxide thickness less than 20 Å. The degree of hydrogen passivation, surface micro-roughness and organic removal capability are considered to be the main factors that explain the differences between the cleaning methods. Data derived from capacitance-voltage analysis of test capacitors verified the trend observed in the native oxide thickness measurements. An increase of 10~15 % in accumulation capacitance is observed in the samples treated by the new cleaning method.

Epitaxial growth of yittria-stabilized zirconia oxide thinfilm on natively oxidized silicon wafer without an amorphouslayer

By varying oxygen partial pressure duringdeposition, epitaxial yittria-stabilized zirconia thinfilms were grown on natively oxidized silicon wafer by thepulsed laser deposition technique. The commensurate crystallineinterface was attributed to the lower partial pressure at theinitial deposition stage, where the amorphous interfacial oxideis eliminated by the metal Zr (or Y) ions reacting with nativesilicon oxide on the surface of the silicon substrate. The partialpressure effect on the origin of re-growth of amorphousinterfacial oxide is discussed. The results demonstrate thatthe commensurate crystalline oxide can be obtained by an appropriatedeposition process, which sheds light on the fabrication ofhigh-quality crystalline thin films on Si wafers to promote theapplication of silicon-based electronic technology.

Kinetic Limitations on Metal Dissolution during Aqueous Silicon Wafer Processing

Metal contamination during aqueous processing has recently been a subject of great interest,1-14 since metal surface contamination can decrease yield in semiconductor manufacturing by causing a wide variety of electrical problems.1,3,5,6 For example, the metal contamination tolerance level for 16 megabyte (MB) dynamic random access memory (DRAM) devices is approximately 1010 metal atoms/cm2.15-17 Deposition has been suggested to occur by a variety of mechanisms,4,6,16,18 including precipitation from a supersaturated cleaning solution and incorporation into the silicon dioxide layer during oxide regrowth. The most problematic is a proposed electroless process whereby metal ion reduction and silicon oxidation occur simultaneously following HF dissolution of the native oxide.4 The physical processes which occur during dissolution and removal have been less studied, although they can also be important to obtaining a contamination-free substrate. For example, during Cu dissolution into an SC-1 process solution, one might expect the electroless dissolution in this basic solution to occur via the following half-reactions

An X-ray photoelectron spectroscopy study of the HF etching of native oxides on Ge(111) and Ge(100) surfaces

An X-ray photoelectron spectroscopy (XPS) study of the removal of the native oxides from the Ge(111) and Ge(100) surfaces by hydrofluoric (HF) acid based etch treatments is presented. A cyclic HF etch, water rinse procedure which was repeated a number of times before loading the samples into the XPS chamber was found to be an effective surface oxide removal treatment. In the analysis, germanium 2p and 3d core level data was collected together with C 1s and O 1s data. The Ge 2p and 3d core levels have a wide kinetic energy separation of significantly different escape depths. By consistently curve fitting the chemically shifted oxide peaks for these two core levels it was possible to determine the thickness of the residual oxide coverage on the chemically etched surfaces. Rates of native oxide re-growth as a function of exposure to ambient conditions were also monitored. These oxide regrowth rates were found to be comparable to those reported for hydrogen passivated silicon surfaces suggesting that the chemical procedures used on germanium resulted in the formation of hydrogen terminated surfaces.

Tem Studies of Polysilicon Emitter Bipolar Materials & Devices: Increased Interfacial Oxide Break-Up and Polysilicon Regrowth and Decreased Emitter Resistance by Fluorine Implantation

AbstractThe role of fluorine (F) in the break-up of the native oxide and the regrowth of As doped poly-Si layers on unpatterned Si wafers and on patterned regions of Si device wafers at temperatures of 900°C to 1000°C are investigated by TEM and by the fabrication of npn poly-Si emitter bipolar devices. Results for unpatterned wafers with F show i) a 950°C dopant drive-in anneal causes oxide break-up and regrowth after a time suitable for the fabrication of devices, ii) a pre-anneal, before the As implant, further enhances the break-up and regrowth and iii) there is an optimum F dose of 5×1015/cm2. Based on these results poly-Si emitter bipolar devices were fabricated using F=5×1015/cm2, a pre-anneal and a 900°C As drive-in anneal. The results establish quantitatively the relationship between the interface structures and the specific emitter resistance, i.e. with no F there is no break-up or regrowth and the emitter resistance is high (114Ωμm2) while with F there is break-up and regrowth and the emitter resistance is low (17Ωμm2).