Nickel and nickel(II) oxide are widely used in advanced electronic devices. In microelectronic industry, nickel is used to form nickel silicide. The nickel mono-silicide (NiSi) has emerged as an excellent material of choice for source-drain contact applications below 45 nm node CMOS technology. As compared to other silicides used for the contact applications, NiSi is preferred because of its low resistivity, low contact resistance, relatively low formation temperature and low silicon consumption. Nickel is used in nickel-based rechargeable batteries and ferromagnetic random access memories (RAMs). Nickel(II) oxide is utilized as transistor gate-oxide and oxide in resistive RAMs.
Atomic Layer Deposition (ALD) is a special type of Chemical Vapor Deposition (CVD) technique, that is used to deposit very smooth as well as homogeneous thin films with excellent conformality even at high aspect ratios.
In spite of huge number of practical applications of nickel and nickel(II) oxide, a few nickel precursors are available for thermal based ALD. Moreover, these precursors have resulted in poor film qualities and the process properties were also limited. Therefore in this master thesis, the properties of various novel nickel precursors had to be evaluated. All novel precursors are heteroleptic (different types of ligands) complexes and were specially designed by the manufacturer for thermal based ALD of pure nickel with hydrogen as a co-reactant.
In order to evaluate the novel precursors, a new methodology was designed to test small amounts (down to 2 g) of precursors in a very time efficient way. This methodology includes: TGA/DTA curve analyses of the precursors, thermal stability tests in which the precursors (< 0.1 g) were heated at elevated temperatures in a sealed environment for several hours, deposition experiments, and film characterizations. The depositions were monitored with the help of in situ quartz crystal microbalance, while application related film properties like chemical composition, physical phase, thickness, density, roughness and sheet resistance were investigated with the help of ex situ measurement techniques. [....]
Table of Contents
1 Introduction
I Theoretical Part
2 Nickel and Nickel Oxides
2.1 Introduction and Existence
2.2 Material properties of Nickel and Nickel Oxide
2.3 Application in electronic industry
3 Atomic Layer Deposition
3.1 History
3.2 Definition
3.3 Features of thermal-ALD
3.3.1 ALD growth mechanism – an ideal view
3.3.2 ALD growth behaviour
3.3.3 Growth mode
3.3.4 ALD temperature window
3.4 Benefits and limitations
3.5 Precursor properties for thermal-ALD
3.6 ALD & CVD of Nickel – A literature survey
4 Metrology
4.1 Thermal analysis of precursors
4.2 Film and growth characterization
4.2.1 Quartz Crystal Microbalance
4.2.2 Spectroscopic Ellipsometry
4.2.3 X-Ray Photoelectron Spectroscopy
4.2.4 Scanning Electron Microscopy
4.2.5 X-Ray Reflectometry and X-Ray Diffraction
4.2.6 Four Point Probe Technique
5 Rapid Thermal Processing
5.1 Introduction
5.2 Basics of RTP
5.3 Nickel Silicides-A literature survey
II Experimental Part
6 Methodologies
6.1 Experimental setup
6.2 ALD process
6.2.1 ALD process types and substrate setups
6.2.2 Process parameters
6.3 Experimental procedure
6.3.1 Tool preparation
6.3.2 Thermal analysis and ALD experiments from nickel precursors
6.3.3 Data acquisition and evaluation
6.3.4 Characterization of film properties
7 Results and discussion
7.1 Introduction
7.2 QCM verification with Aluminum Oxide ALD process
7.3 ALD process from the reference precursor
7.3.1 Introduction
7.3.2 TG analysis for Ni(amd) precursor
7.3.3 Thermal stability test for Ni(amd)
7.3.4 ALD process optimization
7.3.5 Film properties
7.4 Evaluating the novel Nickel precursors
7.4.1 Screening tests for precursor P1
7.4.2 Screening tests for precursor P2
7.4.3 Screening tests for precursor P3
7.4.4 Screening tests for precursor P4
7.4.5 Screening tests for precursor P5
7.5 Comparison of all nickel precursors used in this work
8 Conclusions and outlook
A Deposition temperature control & Ellipsometry model
B Gas flow plan
Research Objectives and Topics
The primary goal of this master thesis is the evaluation of several novel Nickel precursors for Atomic Layer Deposition (ALD) to facilitate the production of thin films suitable for source and drain contact metallization in 28 nm semiconductor technology and beyond. Since existing Nickel precursors have been limited in availability and film quality, this work aims to develop an efficient testing methodology to screen these new materials.
- Development of a time-efficient testing procedure for novel metalorganic precursors using small sample quantities.
- Optimization of a benchmark ALD process using a reference precursor to establish standard process parameters.
- Thermal analysis (TGA/DTA) and thermal stability testing of novel Nickel precursors.
- Comprehensive film characterization, including chemical composition, physical phase, thickness, density, and sheet resistance, using various metrological techniques (XPS, XRR, SEM, 4PP).
- Assessment of the feasibility of these precursors for nickel silicide formation in comparison to state-of-the-art processes.
Excerpt from the Book
3.3.1 ALD growth mechanism – an ideal view
The above figure 3.3.1 shows a four – step ALD growth mechanism and is repeated until a desired thickness of material is deposited. Most of the ALD processes are based on binary reaction mechanism where two surface reactions occur in a self – limiting sequential fashion [ George 2010 ] and is described as follows :
1. Exposure of the reactant A: In this step the reactant A is introduced into the chamber. On exposure of reactant A an irreversible chemisorption reaction takes place on the surface of substrate and is shown in figure 3.3.1a. Three main classes of chemisorption mechanisms are ligand exchange, molecule dissociation and association [ Puurunen 2005, p. 121301 - 24 ]. The exposure of reactant A is the first step towards a self-limiting growth mechanism. A self limited growth mechanism is due to the limited availability of active sites on the surface of substrate [ George 2010, p.112 ]. For instance, in figure 3.3.1a there are seven active sites available which allow the chemisoprtion of maximum seven molecules of reactant A. The active sites are the sites on the surface of substrate that are terminated by reactive groups like -OH, -H, -SH etc. These reactive groups make a surface chemical reaction possible.
2. Purging or evacuation: After the exposure of reactant A a reaction chamber is purged or evacuated with the help of non-reacting gases like argon as shown in figure 3.3.1b. Inert gas acts as a purging or transport gas. This step is necessary to remove excessive non-reacted precursor molecules as well as the reaction by-products which prevents further incorporation of any contaminations and CVD like effects. A vacuum pump or other mean is required to draw all unnecessary products out of the reaction chamber.
Summary of Chapters
1 Introduction: Provides an overview of the application of Nickel and Nickel(II) oxide in microelectronics and introduces the need for evaluating novel precursors for ALD.
2 Nickel and Nickel Oxides: Details the material properties, physical characteristics, and electronic industry applications of Nickel and its oxides.
3 Atomic Layer Deposition: Discusses the history, definition, features, and advantages/limitations of the ALD technique, including a survey of existing literature on Nickel ALD.
4 Metrology: Describes the analytical experimental techniques used, specifically thermal analysis (TGA/DTA) and various film characterization methods like QCM, Ellipsometry, and XPS.
5 Rapid Thermal Processing: Covers the basics of RTP and provides a literature survey on Nickel silicide formation, including its application in semiconductor devices.
6 Methodologies: Explains the experimental setup, ALD process parameters, and the detailed procedures used for testing precursors and evaluating thin film properties.
7 Results and discussion: Presents the findings of the benchmark ALD process and the comprehensive screening/evaluation of the five novel Nickel precursors.
8 Conclusions and outlook: Summarizes the findings regarding the precursors and offers recommendations for future research in optimizing Nickel precursor stability for ALD.
Keywords
Atomic Layer Deposition, ALD, Nickel, Metalorganic Precursors, Thin Films, Nickel Silicide, Thermal Analysis, TGA, DTA, Spectroscopic Ellipsometry, X-Ray Photoelectron Spectroscopy, XPS, Quartz Crystal Microbalance, Semiconductor Technology
Frequently Asked Questions
What is the core subject of this thesis?
The thesis focuses on the evaluation of several novel metalorganic Nickel precursors for Atomic Layer Deposition (ALD) to improve the quality of Nickel-based thin films used in microelectronic applications.
What are the central thematic fields?
The research encompasses thin film deposition techniques (ALD), precursor chemistry, thermal analysis (TGA/DTA), and metrology (characterization methods like XPS, XRR, and Ellipsometry) applied to semiconductor manufacturing.
What is the primary objective of the work?
The goal is to determine if the provided novel Nickel precursors are suitable for thermal ALD, specifically by assessing their thermal stability, sublimation properties, and the resulting film quality.
Which scientific methodology is applied?
The work employs a multi-step methodology: TGA/DTA analysis, thermal stability testing in sealed ampoules, benchmark process development using a reference precursor (Ni(amd)), and subsequent screening of novel precursors with in-situ QCM monitoring and ex-situ characterization.
What is covered in the main body of the thesis?
The main body is divided into a theoretical part, covering ALD and Nickel properties, and an experimental part, detailing the setup, precursor screening tests (P1-P5), and data evaluation regarding their growth behavior and film characteristics.
Which keywords best characterize this research?
Keywords include Atomic Layer Deposition (ALD), Nickel, Nickel Silicide, Metalorganic Precursors, Thin Films, Thermal Analysis, and various characterization techniques like XPS and Ellipsometry.
Why are standard precursors often unsuitable for ALD?
Existing precursors often exhibit limited thermal stability, leading to self-decomposition, poor film homogeneity, and significant impurity incorporation, which deviates from the ideal self-limiting ALD growth mechanism.
What were the main conclusions regarding the tested precursors (P1-P5)?
The evaluation revealed that most tested precursors underwent thermal decomposition or structural changes at operating temperatures, making them generally unsuitable for achieving high-quality metallic nickel films through standard thermal ALD.
- Citar trabajo
- M.Sc. Nanoelectronic Systems Varun Sharma (Autor), 2015, Evaluation of Novel Metalorganic Precursors for Atomic Layer Deposition of Nickel-based Thin Films, Múnich, GRIN Verlag, https://www.grin.com/document/294280
