Incubation Time Measurements in Thin-Film Deposition

Studies on the initial growth or nucleation of materials and research on selective deposition often mention an incubation time. Many techniques exist to determine the incubation time. The outcome can be very different for each technique when the same nucleation process is considered. For the first time we have given a simple model which shows that several incubation times can be expected if different methods are used. One of the most popular methods, plotting the mass or thickness as a function of time and defining the incubation time as the intercept on the x-axis, is not a good method. In particular, a meaningful incubation time is found only if a layer-by-layer growth mechanism occurs right from the start. Ellipsometry can be used in situ and is a much more sensitive method, but this technique needs more research to correlate the nucleation process with the data obtained using this technique. The determination of the nucleus density using scanning electron microscopy or atomic force microscope is the most accurate method, yet needs a lot of experiments. Without a detailed description of the measurement method the incubation time is a meaningless quantity

Furnace and rapid thermal crystallization of amorphous GexSi1-x and Si for thin film transistors

The crystallization behavior of polycrystalline silicon (Si) and germanium-silicon alloys (GexSi1−x) from SiH4 and GeH4, where x is in the range of 0-0.32, has been investigated for thin film transistor (TFT) applications. Furnace anneals as well as rapid thermal anneal (RTA) and combinations of these two techniques have been used to crystallize amorphously deposited thin (≤100 nm) films. The effects of time and temperature for the furnace anneals and time, temperature and pulse rate for the RTA have been investigated. Smooth Si and GexSi1−x layers with a surface roughness ≤0.6 nm have been obtained using an initial Si layer for the GexSi1−x material, since GexSi1−x shows a nucleation problem on oxide surfaces which influences the resulting surface roughness and grain size. For TFT applications the optimal film properties cannot be obtained with a single crystallization anneal. Conventional furnace crystallization results in smooth layers with Si furnace crystallized films exhibiting small grains with many intra-grain defects. An average grain size of approximately 300 nm for Ge0.25Si0.75 and slightly larger grains for Ge0.32Si0.68 with less defects is obtained at lower temperature. RTA results for Si and GexSi1−x in fine grained material with lower defect density

Dielectric breakdown I: A review of oxide breakdown

This paper gives an overview of the dielectric breakdown in thin oxide layers on silicon. First test methods are discussed, followed by their application to the estimation of the oxide lifetime. The main part of the paper is devoted to the physical background of the intrinsic breakdown. Finally, defect-related or extrinsic breakdown is discussed

Dielectric breakdown II: Related projects at the University of Twente

In this paper an overview is given of the related activities in our group of the University of Twente. These are on thin film transistors with the inherent difficulty of making a gate dielectric at low temperature, on thin dielectrics for EEPROM devices with well-known requirements with respect to charge retention and endurance and, finally, on thin film diodes in displays with unexpected breakdown properties

An empirical model for early resistance changes due to electromigration

A new heuristic description for electromigration-induced early resistance changes is given. The basis is formed by two coupled partial differential equations, one for vacancies, and one for imperfections. These equations are solved numerically for a grain boundary bamboo structure. It is shown that this model is capable of simulating the typical effects as observed in early resistance change measurements. These early resistance changes are due to the redistributions of the vacancies and the generation of imperfections. Simulations are performed that closely match the measured resistance change curves

Comprehensive physical modeling of NMOSFET hot-carrier-induced degradation

The role of hot-carrier-induced interface states in NMOSFETs is discussed. A new model is proposed based on measurements in several 0.7¿m CMOS technologies of different suppliers. Our model for the first time enables accurate interface state prediction over many orders of magnitude in time for all stress conditions under pinch-off and incorporates saturation. It can easily be implemented in a reliability circuit simulator, enabling more accurate NMOSFET parameter degradation calculations(e.g. ¿ID ¿gm etc.)

Extraction of Kinetic Parameters for the Chemical Vapor Deposition of Polycrystalline Silicon at Medium and Low Pressures

The deposition of silicon (Si) from silane (SiH4) was studied in the silane pressure range from 0.5 to 100 Pa (0.005 to1 mbar) and total pressure range from 10 to 1000 Pa using N2 or He as carrier gases. The two reaction paths, namely,heterogeneous and homogeneous decomposition could be separated by varying the amount of wafer area per unit volume(wafer-distance variation) and the SiH4 partial pressure as well as the total pressure. Rate constants were derived by fittingthe experimental results. The heterogeneous reaction path could be described by only the adsorption rate constants ofreactive species and the desorption rate constant of hydrogen using a Langmuir-Hinshelwood mechanism. Hydrogen andphosphine were found to suppress the deposition rate at low silane pressures. At high silane pressures or high totalpressures the unimolecular decomposition of silane dominates. The unimolecular rate constant was found to be one to twoorders larger than literature values based on RRKM analyses of high pressure rate data. The relative efficiency of SiH4-N2and SiH4-He collisions compared with SiH4-SiH4 collisions in the unimolecular gas-phase decomposition of SiH4 has beeninvestigated. Helium was found to be a weak collider compared to silane and nitrogen