Developments in Surface Contamination and Cleaning: Types of Contamination and Contamination Resources

Volume 10

Rajiv Kohli, Kashmiri L. Mittal

• Publisher: William Andrew
• Year: 2016
• Print ISBN: 9780323431583
• eBook ISBN: 9780323431736
• Topic: Physical Sciences
• Subtopic: Industrial & Technical Chemistry

Developments in Surface Contamination and Cleaning, Volume Ten, provides a state-of-the-art guide to the current knowledge on the behavior of film-type and particulate surface contaminants and their cleaning methods. This newest volume in the series discusses mechanisms of particle adhesion, particle behavior in liquid systems, and metallic contamination and its impact. In addition, the book includes a discussion of the types of contaminants, with resources to deal with them and information on environmental issues related to surface contamination and cleaning. Taken as a whole, the series forms a unique reference for professionals and academics working in the area of surface contamination and cleaning that also includes information on cleaning at the micro and nano scales. - Written by established experts in the contamination field that provide an authoritative resource - Presents a comprehensive review of new trends in contaminants and resources for dealing with those contaminants - Contains detailed case studies to illustrate various scenarios

Chapter 1

Metallic Contaminants on Surfaces and Their Impact

Rajiv Kohli, The Aerospace Corporation, Houston, TX, United States

Abstract

Metallic contaminants are ubiquitous as discrete particles or in ionic form. Even in very low concentrations, they can adversely affect the performance of high-end devices. This chapter provides an overview of the sources and generation of metallic contaminants and discusses some of their impacts. Analytical techniques are briefly described that are available to detect and characterize metallic contaminants at the nanoscale.

Keywords

Contaminants; metallic contamination; diffusion; solubility; retrograde solubility; retrograde melting; defects; mitigation; cleanliness levels; impact; characterization techniques

Chapter Outline

1 Introduction 1

2 Cleanliness Levels 2

3 Metallic Contaminant Behavior 11

3.1 Diffusion 13

3.2 Solubility 16

4 Contamination Sources 23

4.1 Metal Impurities and Particles 23

4.2 Ionic Contamination 28

5 Characterization Techniques 29

6 Impact of Metallic Contaminants 34

6.1 Metal Particles and Trace Metal Impurities 34

6.2 Ionic Contamination 36

7 Summary 38

Acknowledgments 38

Disclaimer 38

References 38

1 Introduction

Metallic contaminants occur in nature as byproducts of natural processes where they are present in the starting materials for industrial products such as quartz used for manufacturing silicon-based devices, or as impurities in minerals used for producing high-end metal products. Metal contaminants are also produced as byproducts of human and industrial activity and can deposit on the surface of the product with detrimental effect. For example, in semiconductor silicon wafer processing, transition metal impurities in the wafer form metal silicide precipitates that can result in haze on the wafer surface. The performance of the device can be significantly degraded by metal impurities in the starting materials and metallic contaminants from the manufacturing process. In the case of a hard disk drive, a particle with dimensions of the order of the flying height between the recording head and the disk that is trapped between the head and the disk can cause catastrophic failure of the drive. Cationic contaminants also can lead to corrosion of the recording head and failure of the drive. The emphasis in this chapter will be on metallic contaminants deposited on the surface of products or present in the starting materials for products like semiconductor wafers and solar cells that are manufactured in controlled environments such as cleanrooms. Removal of contaminants has been covered previously and will not be addressed here. The discussion in this chapter is necessarily an overview of the broad and diverse subject matter and no attempt is made at comprehensiveness. A large number of general references address different aspects of metallic contamination and provide sources of additional information [1–41].

2 Cleanliness Levels

In the semiconductor industry, metallic contaminants at very low levels can adversely affect the performance of devices. Several standards and specifications have been issued that define allowable trace metal contamination levels in starting materials and on surfaces in the manufacturing environment.

The most recent (2013) version of the International Technology Roadmap for Semiconductors (ITRS) lists maximum levels for trace metals in its 15-year projections to 2026 for a wide range of current and emerging semiconductor materials for various current and future device applications, including novel metal oxides, chalcogenides, graphene, carbon nanotubes, low-/high-k dielectric materials, and new and advanced materials, as well as process chemicals (Table 1.1) [42].

Table 1.1

ITRS Table YE3 Defines the Technology Requirements for Wafer Environmental Contamination Control Relative to Metal Contaminants [42]

Year of Production	2013	2014	2015	2016	2017	2018	2019	2020	2021	2...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of Contributors
• About the Editors
• Preface
• Chapter 1. Metallic Contaminants on Surfaces and Their Impact
• Chapter 2. Particle Resuspension From Surfaces: Overview of Theoretical Models and Experimental Data
• Chapter 3. GMP in Pharma Manufacturing—Description of GMP as Related to Air-Handling Units and Prevention of Contamination and Implementation of GMP Regulatory Requirements
• Chapter 4. The Role of Standards in Cleaning and Contamination Control
• Chapter 5. Droplet-Assisted Laser Cleaning of Contaminated Surfaces
• Index