Low-pressure Thermal Chemical Vapor Deposition Research Articles

Liquid source chemical vapor deposition of high-dielectric-constant (Ba, Sr)TiO3 films

High-dielectric-constant (Ba, Sr)TiO3 [BST] films were deposited by the liquid source chemical vapor deposition (CVD) method. The system consisted of a single-wafer, low-pressure thermal CVD reactor, a vaporizer for liquid source materials, and a shower-type gas nozzle head, giving stable BST film deposition on a 6-in. diam. substrate with uniform thickness and uniform chemical composition ratio. The source materials employed were Ba(DPM)2, Sr(DPM)2, and TiO(DPM)2 dissolved in tetrahydrofuran (THF), resulting in conformal step coverage of BST films at lowered substrate temperatures, where DPM denotes dipivaloylmethanate. Moreover, the two-step deposition technique was developed to restart protrusions formed on BST film surfaces at low temperatures, where the BST films consisted of a buffer layer and a main layer; the buffer layer was a layer about 60 Å thick of CVD-BST film annealed in N2. Thus, the two-step CVD deposition of BST films on Pt and Ru electrodes achieved an equivalent SiO2 thickness of teq ∼ 0.5 nm, a leakage current of JL ∼ 1.0 × 10−8 A/cm2 (at +1.1 V), and a dielectric loss of tan δ ∼ 0.01 at a total film thickness of 250 Å, along with conformal coverage of 80% for a trench with an aspect ratio of 0.65. Then, for BST films deposited on patterned electrodes 0.24 μm wide, 0.60 μm deep, and 0.15 μm high (each spaced by 0.14 μm), the capacitance was demonstrated to be increased without significant deterioration of the leakage current: the capacitance was increased in comparison with that for films on flat electrodes, by a factor corresponding to the increase in surface area due to sidewalls of storage-node-like pattern features. This capacitance increase reflects the most characteristic advantage of CVD, an excellent step coverage on microscopic pattern features. These electrical properties satisfy the specifications for capacitors for Gb-scale dynamic random access memories (DRAMs), giving a storage capacitance of more than 25 fF/cell for a stacked capacitor having a storage node 0.2 to 0.3 μm high. © 1998 Scripta Technica, Electr Eng Jpn, 125(1): 47–54, 1998

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.

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.

溶液気化CVD法による(Ba, Sr) TiO<sub>3</sub>高誘電率薄膜形成

High dielectric constant (Ba, Sr) TiO3 [BST] films have been deposited by liquid source chemical vapor deposition (CVD) method. The system consisted of a single-wafer, low-pressure thermal CVD reactor, a vaporizer for liquid source materials, and a shower-type gas nozzle head, giving stable BST film deposition on a 6-in. -diam substrate with uniform thickness and uniform chemical composition ratio. The source materials employed were Ba(DPM)2, Sr(DPM)2, and TiO(DPM)2 dissolved in tetrahydrofuran (THF), resulting in a conformal step coverage of BST films at lowered substrate temperatures, where DPM denotes dipivaloylmethanato. Moreover, the two-step deposition technique was developed to restrain protrusions formed on BST film surfaces at low temperatures, where BST films consisted of a buffer layer and a main layer; the buffer layer was an about 60-Å-thick layer of CVD-BST films annealed in N2 ambience. Thus, the two-step CVD deposition of BST films on Pt and Ru electrodes achieved an equivalent SiO2 thickness of teq_??_0.5nm, a leakage current of JL_??_1.0×10-8A/cm2 (at+1.1V) and a dielectric loss of tan δ_??_0.01 at a total film thickness of 250Å, along with a comformal coverage of 80% for a trench of an aspect ratio of 0.65. Then, for BST films deposited on patterned electrodes 0.24μm wide, 0.60μm deep, and 0.15μm high (each spaced by 0.14μm), the capacitance was demonstrated to be increased without a significant deterioration of the leakage current: the capacitance was measured to be increased in comparison with that for films on flat electrodes, by a factor corresponding to an increase in surface area due to sidewalls of storage-node-like pattern features. This capacitance increase reflects the most characteristic advantage of CVD, or an excellent step coverage on microscopic pattern features. These electrical properties obtained satisfy specifications of a capacitor for Gb-scale dynamic random access memories (DRAMS), giving a storage capacitance of more than 25fF/cell for a stacked capacitor having a storage node 0.2_??_0.3μm high.

Processing of Silicon Oxides Thin Films by Thermal LPCVD Starting from Teos Mixtures

AbstractA thermodynamic simulation is presented of the low pressure chemical vapor deposition (LPCVD) of silicon oxide thin films starting from TEOS and N2O mixtures within the temperature range 700 – 1300K, by minimizing the total Gibbs energy of the C‐H‐N‐O‐Si chemical system. It was found that at temperatures up to 1173K and N2O/TEOS molar ratios up to approximately 7, SiO2 films contain carbon impurities, while above this ratio deposits are carbon free. A corresponding experimental investigation is also presented where the obtained submicronic films are slightly substoichiometric in oxygen. They contain small carbon impurities the concentration of which decreases with the N2O/TEOS molar ratio.

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.

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.

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.