Step coverage from an extended sputtering source

The simultaneous one‐dimensional Knudsen diffusion and chemical reaction description of low‐pressure chemical vapor deposition in features on patterned surfaces is used to show that a substantial decrease in processing time can be achieved for a given step coverage by varying the deposition rate in a prescribed manner during the process. For constant‐rate CVD (CRCVD) processes, the rate is dictated by the rate required to obtain a good step coverage at the end of the process when the instantaneous aspect ratio becomes very large. The use of a programmed‐rate CVD (PRCVD) process allows a larger average deposition rate, since the initial rate is much higher than the rate required to maintain good step coverage close to feature closure. The PRCVD concept is demonstrated for the thermally activated deposition of silicon dioxide from tetraethylorthosilicate (TEOS) by decreasing the temperature during deposition. The two‐step process path chosen for our calculations is not optimal; however, it can be easily implemented and modified. The time saved depends on the reaction kinetics, but approaches 50% of the constant rate process time for step coverages above 95%.

Metal Ir films were prepared by spray chemical vapor deposition (CVD) in air from an Ir precursor, (1,3-cyclohexadiene)(ethylcyclopentadienyl)iridium, Ir(EtCp)(CHD). Film deposition was ascertained at 270–430°C on a SiO2/Si substrate and the deposition rate increased with the deposition temperature but was saturated above 330°C. The obtained films consisted of Ir metal without any iridium oxide impurity irrespective of the deposition temperature. Films tended to orient to (111) with increasing deposition temperature. Resistivity of these Ir films decreased with increasing film thickness and reached to values on the order of 10-6 Ω・cm, which was the same order of the values for bulk Ir metal. Good step coverage was observed for the Ir metal films deposited at 270°C and 330°C. This shows that the simple spray CVD process in air is a good candidate for depositing Ir metal films with good conductivity and step coverage.

The deposition characteristics of (Ba, Sr)TiO3 (BST) thin films using a liquid source metal-organic chemical vapor deposition on a 6-inch-diameter Pt/SiO2/Si wafer were investigated. Ba(DPM)2 tetraglyme, Sr(DPM)2 tetraglyme and Ti(DPM)2(O-i-Pr)2, dissolved in n-butyl acetate, were used as the sources of Ba, Sr and Ti, respectively. Step coverage, within-wafer uniformities in composition and thickness of the BST films were investigated as a function of substrate temperatures ranging from 420° C to 570° C. As the substrate temperature decreased, the step coverage improved, whereas the within-wafer uniformities degraded. From BST films deposited in a temperature range from 450° C to 480° C, good step coverage (>80%), as well as good within-wafer uniformity were obtained. However, in that temperature range, hazy deposition was observed due to many humps on the surface. The humps are an agglomeration of crystalline grains and are a few hundred Å in diameter, which have a Ti-rich composition compared to flat film region.

Electrodeposition of copper into sub‐0.25 μm features has been studied theoretically and experimentally. A physically based two‐dimensional (2D) pseudo‐steady state and a one‐dimensional (1D) unsteady‐state mass‐transfer model have been developed to study the effect of important parameters on the step coverage, evolution of copper deposits in damascene features, and deposition rate inside high aspect ratio single and dual damascene features. An analytical model that assumes linear deposition kinetics and a fixed boundary also has been developed and found to be in good agreement with the numerical results of the free boundary models to about 50% filling of the feature. A new criterion, based on the pulse plating parameters, for optimizing the opposing trends in step coverage and the deposition rate is also given. Copper has been deposited into submicron features, by dc and pulse plating, using an alkaline bath. Deposit evolution inside trenches has been studied by performing sequential plating experiments. Copper deposits with good morphology and resistivity were obtained using the alkaline bath. Experimental observations have been compared to the model trends and found to be in good agreement. Pulse plating experiments show that the deposit quality and the step coverage are improved over dc plating. Slanting the sidewalls also improves step coverage as shown by 2D model calculations. © 2000 The Electrochemical Society. All rights reserved.

The growth behavior and step coverage of thin films deposited by liquid-delivery metallorganic chemical vapor deposition (MOCVD) at temperatures ranging from 410 to 490°C were investigated. The film growth rates were controlled by the gas phase thermal decomposition reaction of the precursors, and the reaction shows an apparent activation energy of . The gas phase thermal decomposition produced several intermediate precursor molecules with different sticking coefficients. The intermediate precursors played a crucial role in the film growth and step coverage change. As the growth rate decreases, the step coverage degrades, which can be explained by Langmuir’s isothermal adsorption model of the precursors with the assumption of the various intermediate molecular structures of the precursors. The bulkier intermediate molecular structure of the precursor increases the steric hindrance between the previously adsorbed molecules and the impinging molecules so that the step coverage improves. The unusual step coverage of an MOCVD film previously observed for a low precursor injection rate was successfully explained using the results derived from the MOCVD and nonsticking property of the Ti-precursor molecules on the SrO surface.

(Ba, Sr)TiO 3 (BST) thin films have been grown on planar Ir/Si and Pt/Si substrates and on three-dimensional (3D) Ir electrodes by metalorganic chemical vapor deposition using two kinds of β-diketonate-based BST precursors. Film growth was studied as a function of film thickness, composition, and substrate temperature. Growth rate was monitored by in situ spectroscopic ellipsometry. The BST films were characterized ex situ by a variety of techniques including x-ray photoelectron spectroscopy, Auger electron microscopy, atomic force microscopy, transmission and scanning electron microscopy, x-ray diffraction, and impedance analyzer. The results reveal that the two sets of BST precursors, albeit slightly different, show quite different reactivities that strongly affect the step coverage on the 3D structure. However, different reactivities have no apparent effect on the microstructure, surface morphology, and dielectric properties of the stoichiometric BST films. These properties strongly depend on the film composition, substrate material, and growth temperature. In general, the BST films grown on Pt exhibit better crystalline quality, surface smoothness, and dielectric properties compared to those grown on Ir under the optimal growth conditions.

Some of the important technical challenges for sub-micron CMOS logic and ASIC devices lie in the multilevel metallization module. Device integration becomes a complex task to balance yield, manufacturability, and reliability demands for these process modules. Important issues include low resistance contacts and vias, good step coverage, high current carrying capability and high electromigration resistance. We have developed a double level Ti/TiN-AlSiCu-TiN metallization scheme with a cold/hot aluminium PVD process and an additional Ti layer on the top of the Ti/TiN-barrier for both metals. The additional Ti layer inhibits the formation of Si nodules, improves the step coverage and increases the reliability.

A Monte Carlo sputter flux transport model has been developed for efficient generation of angular, energy, and thickness uniformity distributions for application to integrated circuit metallization films. The model allows for arbitrary target erosion profiles and emission angular distributions and uses an energy-dependent gas-scattering model. Verification of the model using aluminum and copper pinhole images has been obtained. The resulting sputter distribution information can be input into a topography-level film-deposition model to provide step coverage and microstructure depictions. The combination of these two models has been used to examine metallization issues such as film thickness uniformity, step coverage, compositional variations in alloy films, and magnetron source design.

Tailoring indium oxide film characteristics through oxygen reactants in atomic layer deposition with highly reactive liquid precursor

Titanium nitride (TiN) films were deposited using tetrakis(dimethylamido)titanium (TDMAT) as a precursor. During film growth, N‐ and Ar‐ion beams with an energy of 120 eV were supplied in order to improve the film quality. The films deposited using a N‐ion beam showed a resistivity of about 320 μΩ cm and density of . The use of the N‐ion beam, however, drastically degraded the step coverage of the film (below 5% at the 0.5 × 1.5 μm contact). The films deposited using an Ar‐ion beam showed a resistivity of about 800 μΩ cm and density of . The step coverage measured at the same contact was around 30%. For comparison, the thermally decomposed film showed a resistivity of about 5800 μΩ cm and density of . Finally, the diffusion barrier properties of 50 nm thick TiN films for Cu were investigated by the etch‐pit test. The films deposited using N‐ and Ar‐ion beam failed after annealing at 600 and 650°C for 1 h, respectively, while thermally decomposed films failed at temperatures as low as 500°C. It is thought that the improvements of the diffusion barrier performance of the films deposited using a N‐ and Ar‐ion beam are the consequence of the film densification resulting from ion bombardment during film growth. © 2000 The Electrochemical Society. All rights reserved.

This paper mainly focuses on solving the low yield problem for lateral phase change random access memory with a fully confined phase change material node. Improper over-etching and bad step-coverage of physical vapor deposition were the main reasons for the poor contact quality, which leads to the low yield problem. Process improvement was carried out to better control over-etching within 10 nm. Atomic layer deposition process was used to replace physical vapor deposition to guarantee good step coverage. Contrasting cross-sectional photos taken by scanning electron microscopy showed great improvement in contact quality. The atom layer deposition process was demonstrated to have good prospects in nano-contact for phase change memory application.

In recent years, there was an increasing interest in aircraft IR signature as an effective passive means of detecting and locking on to an aircraft. There are two main sources of the aircraft IR emission: engine-fuselage layout and gaseous exhaust plume. The size of aircraft plume is several times more than the size of aircraft. The present work focuses on the exhaust plume. The relatively high temperature plume ejected from the nozzle is a mixture of several species that are products of hydrocarbon fuel combustion under excess air condition: CO2, H2O, CO, O2, and N2. Experimental investigation of IR radiation from exhaust gases of a small turbojet engine was conducted in a micro jet engine SR-30 by Turbine Technologies, Ltd. The compact engine features a centrifugal flow compressor, reverse flow annular combustor and an axial flow turbine stage. The SR-30 follows the fundamental Brayton gas turbine cycle. The engine is operated at different regimes with various flow rates of air and kerosene. Measurements were obtained with engine operating at global equivalence ratio of about 0.23. The IR radiation images of the exhaust flow were obtained by a thermocamera equipped with a narrow bandpass filter that falls on the CO2 fundamental band emission. Temperature profiles were measured by a thermocouple in the exhaust flow. An in-house computer program was developed to calculate the IR emission from optically thick gas object and it takes into account the self-absorption of the IR radiation along a line-of-sight. An essential feature of the calculation is the fact that the optical path is non-isothermal. The typical IR spectrum of a turbo-jet engine exhaust flow was simulated using the developed computer program. The calculations allow prediction of “apparent” plume temperatures measured by the IR camera. The calculated results were compared with the experimental measurements and a good agreement was found.

Although the analysis of beams made of metallic isotopic materials is well developed and documented, less information is available on the analysis of layered composite beams under bending. In the present work, a procedure was developed to analyze single cell closed section and open section made from an assembly of flat layered fibrous composite under symmetric bending. The analysis is based on symmetric laminates for each flat segment of a thin-walled section. For the validation of the presented analysis, a model was constructed with thin-walled open cross section of C shape. The model was tested under bending moment and experimental strain measurements were performed. The results are compared with the theoretical analysis. The comparison shows that the presented approach gives results in a good agreement with the experimental measurements.

Modeling 3D effects of substrate topography on step coverage and film morphology of thin metal films

This paper describes the basic study of the simulation of chemical vapor deposition (CVD) step coverage that is used to estimate the deposition of thin films in LSI production. Given the trend toward extremely high density in the semiconductor manufacturing process, such as that of LSIs, the deposition process of silicon thin film on the circuit pattern needs to be accurate. To optimize the deposition of thin film around the trench of the order of less than a micron, computer simulations of the step coverage and of the film growth rate in the process are very important. In this simulation reported in this paper, the thin film deposition process, whose reaction is modeled as silicon from silane (SiH4) and silylene (SiH2), is solved using the direct simulation Monte Carlo (DSMC) method. The DSMC method is usually adopted in this case, but, since 1) this method solves the Boltzmann equation with a huge amount of molecular collisions and free motions and 2) sticking probability of molecules is of the order of 10-5 [1], even a high performance computer needs much time for this calculation. Although the performance of supercomputers and other types of computers is improving, the DSMC method as conventionally applied seems to be reaching its limit in terms of practicality.