Low-pressure Thermal Chemical Vapor Research Articles

Properties of stacked dielectric films composed of SiO 2/Si 3N 4/SiO 2

Dielectric films composed of silicon oxide-nitride-oxide (ONO) structure have been grown over a polycrystalline silicon phosphorous-doped substrate. The films with a total thickness of about 30 nm have been obtained by two different deposition techniques of the top-oxide layer i.e. thermal oxidation of the nitride layers and low pressure chemical vapour deposition, while the bottom oxide and the nitride layer were obtained by thermal oxidation and low pressure chemical vapour deposition, respectively. The chemical composition was measured by XPS Auger parameter technique while the thickness of the deposited layers was determined by the X-ray reflectivity method and compared with the measurements performed on transmission electron microscopy cross-section images. The influence of the layer composition and thickness on the electrical properties of the whole film, used as dielectric layer of a capacitor with doped polycrystalline silicon as electrodes, have been investigated by measuring current as a function of voltage to study the mechanisms which contribute to an increase of the leakage current with increasing applied voltage. Furthermore, electrical erasable programmable read-only flash memory devices built using these dielectric layers in the floating gate structure have been measured for `data retention loss' after thermal stress. The results give a complete picture on the role of the two topmost layers of the ONO structure towards the electrical behaviour.

Growth and physical properties of in situ phosphorus-doped RTLPCVD polycrystalline silicon thin films

In situ phosphorus-doped (P-doped) polysilicon (poly-Si) thin films are obtained by rapid thermal low pressure chemical vapor deposition (RTLPCVD) in a single chamber RTP machine by using diluted silane (SiH 4/Ar=10%) and phosphine (PH 3=200 ppm). Deposition kinetics of poly-Si films were studied in the 600–850°C temperature range at fixed total pressure of 2 mbar and gas flow rate (100 sccm). Activation energy of 1.82 eV was calculated in the surface reaction deposition regime. Dopant activation has been obtained sequentially by RTO at 1000°C in pure O 2 atmosphere. This later process permits to both activate the phosphorus dopant and forms an ultrathin polyoxide which blocks dopant outdiffusion. Secondary ion-mass spectrometry (SIMS) analysis showed flat P-dopant profiles throughout the film thickness with a P concentration varying from 5.5×10 20 to 2.4×10 19 at/cm 3 when the deposition temperature increases in the 600–850°C range. Grazing incidence X-ray diffraction (XRD) has been used to study the structural properties of the poly-Si layers. It appeared particularly that the amorphous to crystalline temperature transition occurs at around 650°C. Finally, four-point probe measurements showed that sheet resitivities in the mΩ cm range can be routinely achieved for in situ P-doped RTLPCVD poly-Si films.

Electrical and structural properties of poly-Si films grown by furnace and rapid thermal annealing of amorphous Si

In the present work, the effect of rapid thermal annealing (RTA) on the electrical and structural properties of poly-Si thin films, grown by the crystallization of a-Si films deposited by rapid thermal low-pressure chemical vapor deposition, has been studied. Structural and electrical results were obtained using atomic force microscopy, transmission electron microscopy, electron spin resonance, electrical resistivity, and Hall mobility techniques. The effects of the grain size, grain boundaries, and surface roughness on the electrical characteristics of poly-Si films have been investigated. Amorphous Si (a-Si) films crystallized by RTA at 850 °C for 45 s result in the formation of poly-Si with small grains, an electron spin density Ns=5.2×1016 cm−3, and a Hall mobility μH=30 cm2 V−1 s−1. A two-stage annealing, involving low-temperature annealing at 600 °C for 6 h, followed by RTA at 850 °C in five steps of 30 s each, results in the formation of poly-Si films with large grains free of in-grain defects, low surface roughness, and higher Hall mobility μH=43 cm2 V−1 s−1, characteristics rendering such poly-Si films suitable for the fabrication of good performance thin film transistors.

Kinetics of the Formation of Titanium Nitride Layers by Rapid Thermal Low Pressure Chemical Vapor Deposition from TiCl4 ‐ NH 3 ‐ H 2

A kinetic study of the titanium nitride growth by low pressure chemical vapor deposition (LPCVD) from gas‐phase was carried out. Experiments were performed in the temperature range of 600–900°C and in the total pressure range of 20 to 73 Pa. Partial pressures ranges were 0.4 to 2.5 Pa for , 5 to 43 Pa for , and 13 to 28 Pa for The following law of deposition was obtained A model was developed to explain the difference between these results and the published results, and to point out the importance of gas injection configuration on the experimental reaction orders and on the apparent activation energies. When (respectively, ) is injected quite near the substrate, this species is strongly adsorbed on the surface, and the available sites for adsorption (respectively, ) are reduced. Then the reaction order with respect to (respectively, is negative, and the rate‐determining step is the adsorption of (respectively, ). When these two species are injected far from the substrate, the rate‐determining step is the reaction between adsorbed and adsorbed NH or .

Geometric structure of thin SiO xN y films on Si(100)

Thin films of amorphous stoichometric SiO x N y are deposited on radiation-heated Si(100) by rapid thermal low-pressure chemical vapour deposition. We studied the whole range of possible compositions. In order to determine the geometric structure, we used EXAFS and photoelectron spectroscopy. Tetrahedrons constitute the short-range units with a central Si atom connected to N and O. The distribution of the possible tetrahedrons can be described by a mixture of the Random Bonding Model and the Random Mixture Model. For low oxygen contents x/( x+ y)≤0.3, the geometric structure of the film is almost the structure of a-Si 3N 4, with the oxygen preferably on top of Si–N 3 triangles. Higher oxygen contents induce changes in the bond lengths, bond angles and coordination numbers.

Low temperature rapid thermal low pressure chemical vapor deposition of 〈111〉 oriented TiN layers from the TiCl 4NH 3H 2 gaseous phase

Titanium nitride layers are deposited by Rapid Thermal Low-Pressure Chemical Vapor Deposition (RTLPCVD) from the TiCl 4NH 3H 2 gaseous phase. Growth rate, resistivity and crystallographic orientation are studied as a function of the deposition temperature and the NH 3/TiCl 4 partial pressures ratio called R. To fulfill the TiN barrier layer requirements, the deposition temperature and the R value have to be as low as possible. We show that with such conditions, the preferential orientation of the deposited TiN layer is always 〈200〉. This orientation enhances the 〈200〉 orientation of the aluminium overlayer which leads to poor electromigration resistance. In order to obtain 〈111〉 oriented TiN layer, a two step process is proposed. In this way, 〈111〉 oriented TiN layers are deposited at a deposition temperature and with an R ratio value as low as 500°C and 4, respectively. The resistivity of such as-deposited films is 200 μΩcm.

Determination of the hydrogen concentration of silicon nitride layers by Fourier transform infrared spectroscopy

We report on new accurate FTIR measurements of the hydrogen content of amorphous silicon nitride (SiN) layers by evaluating the corresponding absorption lines with the help of polynomial fits. Our measurements show large differences in the hydrogen concentrations comparing layers which were deposited by plasma-enhanced chemical vapor deposition with layers deposited by thermal low-pressure chemical vapor deposition. The hydrogen content of the layers can be successfully reduced by applying various annealing procedures.

LPCVD SiO2 Layers Prepared from SiH4 and O2 at 450 °C in a Rapid Thermal Processing Reactor

In this paper experimental results of the silane oxidation kinetics in a rapid thermal low pressure chemical vapor deposition (RTLPCVD) cold wall reactor at 450 °C are presented. For a certain total pressure kept constant in the range of 0.6-4.5 mbar. it is always found a certain threshold silane partial pressure p(th) SiH4 (decreasing from 0.15 mbar to 0.076 mbar when the total pressure increases) which determines a sharp transition from no film formation to high deposition rates of the SiO 2 layers. Critical partial pressures for lower limits of explosion at room temperature (0.223 mbar) and at deposition temperature (0.17 mbar) are noticed. The film deposition is very sensitive to the changes in the chemical state of the walls. These results may indicate that the silane oxidation process is controlled by the gas phase chain reactions. By keeping constant the total pressure (4.5 mbar), the SiH 4 partial pressure (0.079 mbar) and the total gas flow rate (570 sccm), with the nitrogen varied as a gas balance, an increase-maximum-decrease dependence of deposition rate as a function of O 2 /SiH 4 mole ratio is found. Uniform SiO 2 layers ( 5% around the averaged value) were found for the above CVD conditions and an O 2 /SiH 4 ratio equal to 11. Without further process and equipment improvements this process cannot be used in practice.

Rapid thermal low-pressure metal-organic chemical vapor deposition (RT-LPMOCVD) of semiconductor, dielectric and metal film onto InP and related materials

Abstract Rapidly thermal low-pressure metal-organic chemical vapor deposition (RT-LPMOCVD) was explored as a way to carry out a number of critical steps in the processing of InP-based laser devices, under a vacuum environment. Single-wafer integrated processes (SWIP) employing a multi-chamber cluster tool are suggested as an alternative approach to sequential hybrid batch processing. This work includes demonstrations of the processes for each of the required modules of the cluster. The following processes were realized by means of the RT-LPMOCVD technique: 1. 1. Wafer cleaning using tertiarybutylphosphine (TBP). The InP wafers were annealed at a low protective ambient pressure. Wafer surfaces were degradation-free after being heat-treated at temperatures up to 750 °C for times as long as 30 s under a TBP ambient. 2. 2. III–V semiconductor film deposition. InP and InGaAs layers, undoped and Zn-doped, with low impurity backgrounds were grown using tertiarybutylphosphine (TBP), tertiarybutylarsine (TBA), trimethylindium (TMIn), trimethylgallium (TMGa), and dimethylzinc (DMZn). 3. 3. Deposition of SiO 2 spacer layers onto epitaxially grown InGaAs and InP layers. The SiO 2 films were deposited using a gas mixture of O 2 and 2% diluted SiH 4 in Ar. 4. 4. Reactive ion etching (RIE) of the InP-based material in an electron cyclotron resonance-reactive ion etching (ECR-RIE) chamber. A stainless-steel mask (25 μm thick) with openings (500 μm long and 50–250 μm wide) was aligned on top of the wafer, and RIE of SiO 2 layers was performed through the mask openings. 5. 5. Cleaning of the semiconductor contacting stripes by heating the wafer at 500 °C under a TBP ambient. 6. 6. Metallization of TiN x and W films to produce ohmic contacts and barrier layers. The American Cyanamid tetrakis (dimethylamido) titanium (DMATi) Cypure TM product was used as the TiN x precursor, which was reduced with NH 3 . The W films were deposited using a W 6 source reduced by H 2 .

Microstructural study of very low resistivity TiNx films formed by rapid thermal low-pressure metalorganic chemical vapour deposition on InP

Significant reductions in sheet resistivity of TiNx films formed by rapid thermal low-pressure metalorganic chemical vapour deposition onto InP, were realized by increasing the substrate temperature through the deposition, utilizing a post-deposition, in situ, heat treatment at temperatures up to 600 degrees C, and adding tertiarybutylphosphine (TBP) metalorganic precursor to the reactive gas mixture. As a result, film resistivity values as low as 30 mu Omega cm were obtained. Extensive transmission electron microscopy analysis was performed and the formation of a new and unidentified phase, having a similar crystal structure and lattice constant to those of Li9TiN2O2, was identified. This phase was formed as a result of TiNx-P intermixing during high-temperature post-deposition sintering of the TiNx/InP system, or as a result of incorporating P in the deposited TiNx film by bleeding TBP. This phase formation is likely to be the origin of the observed reduction in film resistivity.

Rapid thermal low-pressure chemical vapour deposition of tungsten films onto InP using WF6 and H2

Tungsten (W) films were deposited onto InP in a cold wall, rapid thermal low-pressure chemical vapour deposition (RT-LPCVD) reactor, from a tungsten hexafluoride (WF6) gas reduced by hydrogen (H2). W films of thickness 50-450 nm were deposited in the temperature range 350-550 degrees C, pressure range 0.5-4.5 Torr at deposition rates up to 4 nm s-1 with an apparent activation energy of about 1.12 eV. The film stress varied depending upon the deposition pressure, from low compressive for deposition at 0.5 Torr to moderate tensile for deposition at about 4.5 Torr. The films were aged at temperatures as high as 300 degrees C for about 800 h and exhibited an excellent mechanical stability. Post-deposition sintering of the W films at temperatures up to 600 degrees C led to reduction of the resistivity with a minimum value of about 55 mu Omega cm as a result of heating at 500 degrees C. Conditions for both selective and blanket deposition were defined, and a dry etching process for further geometrical definitions of the films was developed, providing etch rates of 40-50 nm min-1. This report reflects the first attempt to deposit W films onto III-V semiconductor at a very high rate by means of RT-LPCVD.

Improved ultrathin oxynitride formed by thermal nitridation and low pressure chemical vapor deposition process

In this letter, we will present the electrical and reliability characteristics of ultrathin oxynitrides (65–73 Å) formed by thermal nitridation of silicon substrate followed by deposition of silicon dioxide by low pressure chemical vapor deposition (LPCVD) technique. The dielectric integrity has been compared to those of the conventional thermal oxide and reoxidized nitrided oxides. It has been found that the new oxynitrides have lower electron trapping, higher charge-to-breakdown, and lower interface state generation under electrical stress even in comparison to reoxidized nitrided oxides with the same thermal budget. The improved characteristics are believed to be due to the combination of the nitrogen-rich layer at the Si/SiO2 interface, the higher quality of LPCVD oxides over thermally grown oxides, and the reduced hydrogen concentration in the dielectrics in comparison to conventional nitrided oxides. The results indicate that these new oxynitride films may be promising for ultra large scale integrated metal-oxide-semiconductor device applications, especially in cases where low thermal budget processes are desirable.

Low resistance tungsten films on GaAs deposited by means of rapid thermal low pressure chemical vapor deposition

Low resistance tungsten (W) films were deposited onto GaAs substrates by means of rapid thermal low pressure chemical vapor deposition (RT-LPCVD), using tungsten hexafluoride (WF6) gas reduced by hydrogen (H2). Deposition temperatures up to 550 °C for durations of up to 30 s were explored, resulting in deposition of relatively pure W films (containing less than 2% O2 and C). Post-deposition sintering of the layers led to significant reduction of the resistivity to values as low as 50 μΩ cm. The efficiency of the deposition improved upon increasing the H2 flow rate up to 1250 sccm resulting in a deposition rate of about 10 nm/s at a total chamber pressure of 3.5 Torr and temperature of 500 °C. The films appeared to be polycrystalline with a very fine grain structure, regardless of the deposition temperature with good morphology and underwent a limited reaction with the underlying GaAs substrates.

Fast thermal kinetic growth of silicon dioxide films on InP by rapid thermal low-pressure chemical vapour deposition

Silicon dioxide films were deposited onto InP substrates in the ranges of 350-550 degrees C temperature, and 3-15 Torr pressure by means of the rapid thermal low-pressure chemical vapour deposition (RTLPCVD) technique. SiO2 films were deposited using a variety of Ox: SiH4 ratios in the range of 5:1-50:1, and deposition rates of 15-50 nm s-1. The high temperature and high rate deposition was obtained without creating any damage to the InP substrate surface, and resulted in highly densified SiO2 layers with good thickness control and low stress. The main parameters of the as-deposited and annealed films, such as deposition rate, density, refractive index, wet and dry etch rates, stresses, film microstructure, and the SiO2/InP interface quality are reported. These parameters were studied as a function of the process variables, which include deposition time, temperature, pressure, O2:SiH4 ratio, gas flow rates and chamber geometry.

W and Related Alloys Deposited onto InP by RT-LPCVD

ABSTRACTTungsten (W) films were deposited onto InP in a cold wall, rapid thermal low-pressure chemical vapor deposition (RT-LPCVD) reactor, from a tungsten hexafluoride (WF6) gas reduced by hydrogran (H2). W films of thickness 50 to 450 nm were deposited in the temperature range of 350° to 550°C, pressure range of 0.5 to 4.5 Torr and deposition rates up to 4 nm/sec with an apparent activation energy of about 1.12 eV. The film stress varied depending upon the deposition pressure, from low compressive for deposition at 0.5 Torr to moderate tensile for deposition at about 4.5 Torr. The films were aged at temperatures as high as 300°C for about 800 hr and exhibited an excellent mechanical stability. Post-deposition sintering of the W films at temperatures up to 600°C led to reduction of the resistivity with a minimum value of about 55μΩ-crn as a result of heating at 500°C. Conditions for both selective and blanket deposition were defined, and a dry etching process for further geometrical definitions of the films was developed, providing etch rates of 40 to 50 nm·sec-1. This report reflects the first attempt to deposit W films onto III-V semiconductor at a very high rate by means of RT-LPCVD.

Ohmic contacts to InP-based materials induced by means of rapid thermal low pressure (metallorganic) chemical vapor deposition technique

A rapid-thermal-low-pressure-metallorganic-chemical-vapor-deposition (RT-LPMOCVD) technique was executed in order to deposit non-semiconductor thin layer materials, necessary for producing metal contact to InP-based microelectronic devices. Silicon dioxide (SiO2) films were deposited onto InP substrates in rapid thermal cycles, using O2 and 2% diluted SiH4 in Ar, with very fast growth kinetics and low activation energy. The SiO2 film exhibited excellent properties, such as refractivity index, density, internal stress, and wetp-etch rates. The SiO2 films were dry etched in a given pattern to allow for the formation of a small metal contact to the InP-based material, onto which the SiO2 layer was deposited. Subsequently, titanium-nitride (TiNx) thin films were deposited onto the InP substrate through rapid thermal deposition cycles, using a tetrakis (dimethylamido) titanium (DMATi) metallorganic liquid source as the precursor for the process, with fast kinetics. The deposited TiNx films had a stoichiometric structure and contained nitrogen and titanium in a ratio close to unity, but incorporated a large amount of carbon and oxygen. The film properties, such as resistivity (40–80 μΩ·mm) and stress (compressive; −0.5 to −2.0×109 dyne·cm−2), were studied in addition to an intensive investigation of its microstructure and morphology, and their performance as an ohmic contacts while deposited ontop−In0.53Ga0.47As material (Zn doped 1.2×1018 cm−3).

Highly stable silicon dioxide films deposited by means of rapid thermal low-pressure chemical vapor deposition onto InP

An attempt was made to deposit a high thermally stable silicon dioxide (SiO2) film onto InP substrates. The films were grown by rapid thermal, low-pressure chemical vapor deposition (RT-LPCVD), using pure oxygen (O2) and 2% diluted silane (SiH4) in argon (Ar) gas sources, in the temperature range of 350–550 °C and pressure range of 3–10 Torr. The SiO2/InP structures were heated, post-deposition, up to 1000 °C for durations of up to 5 min, resulting in negligible changes in the properties of the SiO2 films and a limited SiO2/InP interfacial reaction of about 15 nm thick. The higher the initial deposition temperature of the SiO2 the larger was the film compressive stress and the less the degree of densification the film underwent through the post-deposition heating cycles.

Rapid thermal low-pressure chemical vapor deposition of SiOx films onto InP

High quality SiOx films have been deposited onto InP substrates by means of a rapid thermal low-pressure chemical vapor deposition technique, using oxygen (O2) and 2% diluted silane (SiH4) in argon (Ar) in the gas sources. Rapid deposition rates in the range of 15–40 nm s−1 with apparent activation energies of 0.12–0.15 eV were obtained at temperatures in the range of 350–550 °C, pressures between 5 and 15 Torr, and O2:SiH4 ratios in the range of 5:1–20:1. The SiOx films had refractive indexes between 1.44 and 1.50, densities of 2.25–2.37 g cm−3, internal compressive stresses of −0.5×109 to −3×109 dyn cm−2, and exhibited wet etch rates of 0.2–0.8 nm s−1 through the standard p-etch process. The influence of the various process parameters on all the SiOx film parameters such as morphology and microstructure was examined.

Rapid Growth Kinetics, Mechanical Properties and Thermal Stability of Siox Thin Films Grown by Rapid Thermal Low Pressure Chemical Vapor Deposition

ABSTRACTHigh quality SiOx films were deposited onto InP substrates in the temperature range of 350 to 550°C and pressure range of 5 to 15 Torr. Depositions were made by means of rapid thermal low pressure chemical vapor deposition (RT-LPCVD) using oxygen (O2) and 2% diluted silane (SiH4) in argon (Ar) gas sources, with O2:SiH4 gas ratio of 5:1 to 50:1. High deposition rates of 15–50 nm/sec were obtained, providing uniform SiOx layers, with low stresses of −5×109 to −2×109 dyne-cm−2, and thermal stability on post deposition temperatures up to 1000°C. The SiOx films had refractive indexes between 1.44 and 1.50, densities of 2.25 to 2.37grcm−3 and exhibited wet etch rates of 0.2 to 0.8 nmsec.−1 through standard p-etch process. The influence of the various process parameters on the SiOx film properties was examined.

Formation of Ohmic Contacts to InP by Means of Rapid Thermal Low Pressure (Metalorganic) Chemical Vapor Deposition (RT-LPMOCVD) Technique

ABSTRACTThe viability of forming an ohmic contact to InGaAs/InP structures by means of a load-locked RT-LP(MO)CVD integrated process, was demonstrated. The wafer was loaded into the reactor chamber and was exposed to a sequence of dry and in-situ processes which led to the formation of an ohmic contact. After an in-situ cleaning of the wafer through a thermal cycle at 500°C under a flow of tertiarybutylphosphine (TBP), which provided the needed free hydrogen for a mild etching of the surface, however with an over pressure of P to eliminate surface degradation, a layer of silicon oxide (SiOx ) was rapid thermal chemical vapor deposited (RT-CVD) onto the InGaAs/InP sample via a rapid thermal cycle (500°C,30 s) in a low pressure O2 and 2% diluted SiH4. Dry etching of 50–150 μm wide contact stripes was carried out using a contact stencil mask by an electron-cyclotron resonance (ECR) dry etching. Subsequently the wafer was reloaded through the load-lock to the main chamber and a TiNx layer were selectively deposited into the via-holes and processed to provide an ohmic contact to the InGaAs/InP substrate. Finally, a blanket deposition of conducting cap layer was realized by means of RT-LP(MO)CVD. This work provides a solid demonstration to the feasibility of the single-wafer-integrated-process (SWIP) as an approach to replace the batch process traditionally used for manufacturing the InP-based optoelectronic devices.