Handbook for Cleaning for Semiconductor Manufacturing E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Serie: Wiley-Scrivener
• Sprache: Englisch

Seitenzahl: 1122

Veröffentlichungsjahr: 2011

Beschreibung

Provides an In-depth discussion of surface conditioning for semiconductor applications

The Handbook of Cleaning for Semiconductor Manufacturing: Fundamentals and Applications provides an in-depth discussion of surface conditioning for semiconductor applications. The fundamental physics and chemistry associated with wet processing is reviewed as well as surface and colloidal aspects of cleaning and etching.

Topics covered in this new reference include:

• Front end line (FEOL) and back end of line (BEOL) cleaning applications such as high-k/metal gate post-etch cleaning and pore sealing, high-dose implant stripping and cleaning, and germanium, and silicon passivation
• Formulation development practices, methodology and a new directions are presented including chemicals used for preventing corrosion of copper lines, cleaning aluminium lines, reclaiming wafers, and water bonding, as well as the filtering and recirculating of chemicals including reuse and recycling
• Wetting, cleaning, and drying of features, such as high aspect ratio features and hydrophilic surface states, especially how to dry without watermarks, the abilities to wet hydrophobic surfaces and to remove liquid from deep features
• The chemical reactions and mechanisms of silicon dioxide etching with hydrofluoric acid, particle removal with ammonium hydroxide/hydrogen peroxide mixture, and metal removal with hydrochloric acid

The Handbook of Cleaning for Semiconductor Manufacturing: Fundamentals and Applications is a valuable resource for any engineer or manager associated with using or supplying cleaning and contamination free technologies for semiconductor manufacturing. Engineers working for semiconductor manufacturing, capital equipment, chemicals, or other industries that assures cleanliness of chemicals, material, and equipment in the manufacturing area will also find this handbook an indispensible reference.

Leseprobe

Contents

Cover

Half Title page

Title page

Copyright page

Foreword

Introduction

Part 1: Fundamentals

Chapter 1: Surface and Colloidal Chemical Aspects of Wet Cleaning

1.1 Introduction to Surface Chemical Aspects of Cleaning

1.2 Chemistry of Solid-Water Interface

1.3 Particulate Contamination: Theory and Measurements

1.4 Influence of Surface Electrical Charges on Metal Ion Adsorption

1.5 Wettability of Surfaces

1.6 High Aspect Ratio Cleaning: Narrow Structures

1.7 Surface Tension Gradient: Application to Drying

1.8 Summary

References

Chapter 2: The Chemistry of Wet Cleaning

2.1 Introduction to Aqueous Cleaning

2.2 Overview of Aqueous Cleaning Processes

2.3 The SC-1 Clean or APM

2.4 The SC-2 clean or HPM

2.5 Sulfuric Acid-Hydrogen Peroxide Mixture

2.6 Hydrofluoric Acid

Acknowledgments

References

Chapter 3: The Chemistry of Wet Etching

3.1 Introduction and Overview

3.2 Silicon Dioxide Etching

3.3 Silicon Etching

3.4 Silicon Nitride Etching

Acknowledgements

References

Chapter 4: Surface Phenomena: Rinsing and Drying

4.1 The Surface Phenomena of Rinsing and Drying

4.2 Overview of Rinsing

4.3 Overview of Drying

Acknowledgements

References

Chapter 5: Fundamental Design of Chemical Formulations

5.1 Introduction and Overview

5.2 Historical Development of Formulations for the Integrated Circuit Industry

5.3 Mechanism of Stripping, Cleaning, and Particle Removal

5.4 Components and Additives in Chemical Formulations

5.5 Creating Chemical Formulations

5.6 Environmental, Safety, and Health Aspects

Acknowledgments

References

Chapter 6: Filtering, Recirculating, Reuse, and Recycling of Chemicals

6.1 Overview of Wet Chemical Contamination Control

6.2 Bulk Chemical Distribution for Wet Cleaning Tools

6.3 Chemical Distribution, Filtering, and Recirculation Requirements for Wet Cleaning Tools

6.4 Contamination Control Metrology

6.5 Effects of Contamination

6.6 Filtration

6.7 Chemical Blending, Recycling, and Reuse

6.8 Summary

References

Part 2: Applications

Chapter 7: Cleaning Challenges of High-k/Metal Gate Structures

7.1 Introduction and Overview of High-κ/Metal Gate Surface Preparation

7.2 Surface Preparation and Cleaning

7.3 Wet Film Removal

7.4 High-κ Removal

7.5 Resist Stripping and Residue Removal

Acknowledgments

References

Chapter 8: High Dose Implant Stripping

8.1 Introduction and Overview of High Dose Implant Stripping

8.2 High Dose Implant Cleaning and Stripping Processes

8.3 Plasma Processing

8.4 Wet Processing

8.5 Other Processing

Acknowledgments

References

Chapter 9: Aluminum Interconnect Cleaning and Drying

9.1 Introduction to Aluminum Interconnect Cleaning

9.2 Source of Post-Etch Residues Requiring Wet Cleaning

9.3 Chemistry Considerations for Cleans Following Etching

9.4 Rinsing/Drying and Equipment Considerations

9.5 Alternative and Emerging Cleaning Technologies

Acknowledgements

References

Chapter 10: Low-κ/CU Cleaning and Drying

10.1 Introduction and Overview

10.2 Stripping and Post-etch Residue Removal

10.3 Pore Sealing and Plasma Damage Repair

10.4 Post-chemical Mechanical Polishing Cleaning

References

Chapter 11: Corrosion and Passivation of Copper

11.1 Introduction and Overview

11.2 Copper Corrosion

11.3 Copper Corrosion Inhibitors

11.4 Copper Cleaning Formulations

Acknowledgments

References

Chapter 12: Germanium Surface Conditioning and Passivation

12.1 Introduction

12.2 Germanium Cleaning

12.3 Surface Passivation and Gate Stack Interface Preparation

References

Chapter 13: Wafer Reclaim

13.1 Introduction to Wafer Reclaim

13.2 Introduction to Silicon Manufacturing for Semiconductor Applications

13.3 Energy Requirements for Silicon Wafer Manufacturing

13.4 Test Wafer Usage and Wafer Reclaim

13.5 Requirements for Wafer Reclaim and Recycle

13.6 Wafer Reclaim Options

13.7 Types of Wafer Reclaim Processes

13.8 Formulated Reclaim Solutions

Acknowledgements

References

Chapter 14: Direct Wafer Bonding Surface Conditioning

14.1 Introduction and Overview of Bonding

14.2 Planarization and Smoothing Prior to Bonding

14.3 Wet Cleaning and Surface Conditioning Processing

14.4 Dry Surface Conditioning Processing

14.5 Thermal Treatments and Annealing

14.6 Conductive Bonding

References

Part 3: New Directions

Chapter 15: Novel Analytical Methods for Cleaning Evaluation

15.1 Introduction

15.2 Novel Analytical Methods

15.3 Recent Advances in Total Reflection X-ray Fluorescence Spectroscopy Analysis

15.4 Advances in Vapor Phase Analysis

15.5 Trace Metal Contamination on the Edge and Bevel of a Wafer

15.6 Kelvin Probe Technologies

15.7 Novel Applications of Electron Spectroscopy Techniques

15.8 Novel X-ray Spectroscopy Techniques

15.9 Electrochemical Sensors

15.10 Summary

Acknowledgments

References

Chapter 16: Stripping and Cleaning for Advanced Photolithography Applications

16.1 Introduction to Advance Stripping Applications

16.2 Historical Background

16.3 Recent Trends for Photoresist Stripping and Post-etch Residue Removal

16.4 Single Wafer Tools

16.5 Wetting in Small Dimensions and Cleaning Challenges

16.6 Environmental Health and Safety

16.7 The Future of Advanced Photoresist Stripping and Cleaning

Acknowledgements

References

Index

Handbook of Cleaning for Semiconductor Manufacturing

Scrivener Publishing3 Winter Street, Suite 3Salem, MA 01970

Scrivener Publishing Collections Editors

James E. R. CouperRichard ErdlacRafiq IslamPradip KhaladkarNorman LiebermanPeter MartinW. Kent MuhlbauerAndrew Y. C. NeeS. A. SherifJames G. Speight

Publishers at ScrivenerMartin Scrivener ([email protected])Phillip Carmical ([email protected])

Copyright © 2011 by Scrivener Publishing LLC. All rights reserved.

Co-published by John Wiley & Sons, Inc. Hoboken, New Jersey, and Scrivener Publishing LLC, Salem, Massachusetts.

Published simultaneously in Canada.

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Cover design by Russell Richardson.

Library of Congress Cataloging-in-Publication Data:

ISBN 978-0-470-62595-8

Foreword

Semiconductor electronic properties are extremely sensitive to the presence of trace amounts of foreign substances. This fundamental property of doped semiconductors is the basis for the fabrication of electronic devices. From the dawn of semiconductor based electronic devices, it has been clear that undesired impurities must be kept at very low levels and material purification methods were essential to the successful operation of such devices.

In the 1950’s and 1960’s, the solid state device of choice was the bipolar junction transistor (BJT), which required a sufficiently long free-carrier recombination lifetime and thus, a low metallic impurity concentration. To achieve this, semiconductor surfaces were cleaned at critical steps in the manufacturing process. In the early 1970’s, the first systematic cleaning studies were carried out and resulted in the “RCA cleaning” process. The aqueous oxidizing mixtures (SC-1 and SC-2) were found to be very efficient at removing a broad range of contaminants such as organics and metals. SC-1, in particular, very effectively removes particles. These mixtures were highly selective towards silicon because of the stability of the passivating SiOx on the silicon surface.

Although the metal-insulator-semiconductor lateral-field effect transistor had been invented in the 1920’s, it was not until the late 1970’s that the metal-oxide-semiconductor field-effect transistor (MOSFET) became a useful electronic device. It was only at that point that surface cleaning reached the capability needed to fabricate high-quality gate oxides with low levels of Na and K contamination essential for making MOSFET devices with stable threshold voltages. This delayed introduction also reflects the thermodynamic propensity of surfaces and interfaces to be the preferred sites for impurities. Within a decade, MOSFET technology replaced the BJT in large scale integrated circuits.

The field of cleaning is complicated by the fact that contamination is often near the edge of detectable limits; consequently, the progress of cleaning science has been tightly linked to advancements in metrology. For a long time, bulk semiconductor electronic properties, such as free carrier lifetime, were the primary measurement technique for contamination. Because MOSFET performance is in large part driven by the quality of its interfaces, more attention has been directed to surface quality and contamination. New metrology techniques such as high resolution electron energy loss spectroscopy (HR-EELS), high resolution X-ray photoelectron spectroscopy (HR-XPS), and Fourier transform infrared spectroscopy (FTIR) helped reveal a great deal about the nature of the chemical structure of a silicon surface and its relation to the aqueous chemical treatments. Surface inspection for particle contamination began in the 1980’s with visual observation under collimated light and has evolved to scanning laser light scattering measurement tools capable of detecting particles only a few tens of nanometers in diameter. Total X-ray fluorescence (TXRF) was developed in the 1990’s and evolved from a research method to a monitoring technique for fast inspection for low-levels of metal contaminants. Time-of-flight SIMS made it possible to detect trace amounts of organic and airborne molecular surface contamination. The availability of these surface measurement techniques made contamination a measurable quantity transforming contamination control and cleaning from an experience-driven field into a science embraced by academic institutes and R&D centers.

The functionality of circuits has increased while feature size has shrunk at an astonishingly high and steady pace. From the early 1990’s, the major quest for yield improvements on megabit-level memory chips has significantly boosted the development of improved cleaning processes and cleaner chemicals. During this wave of substantial investigation, concerns were raised that wet cleaning would quickly run out of steam; consequently, various types of dry cleaning were investigated. Wet cleaning, however, has remained the method of choice because of a number of reasons including: excellent particle removal due to a reduction of van der Waals attractions; highly selective chemical reactions; and good dissolution and transport properties.

The RCA clean has been the backbone in semiconductor cleaning because of its abovementioned properties. Current requirements for cleaning have become more constrained than at the time the RCA clean was introduced. Reduction in surface etching amounts and other issues require that the SC-1 mixtures be very dilute and at reduced temperatures. In many cases, the SC-2 step can be replaced by dilute HCl. These approaches have resulted in longer bath lifetimes, reduced chemical costs, and lower waste burdens. An acidified rinse has been used to further suppress contamination. Alternative simple cleaning recipes have been introduced, such as self-saturating chemical oxide growth using sulfuric acid spiked with ozone, followed by an HF-based mixture.

Cleaning tools have evolved to keep up with ever-changing processes. Wet benches consisting of immersion tanks are now equipped with recirculation and filtration units, automated filling in situ concentration monitoring, and automatic spiking systems. Simplified recipes have resulted in wet benches with fewer tanks. Single tank tools have been introduced for use with very dilute chemicals. The biggest change has occurred since 2000; single wafer cleaning gradually replacing batch tools for critical applications. Single wafer tools made it possible to treat both sides of a wafer differently and thus, provide isolation of the front and back surfaces allowing for high performance cleaning. For single wafer cleaning, process time limitations favor the use of more concentrated chemicals.

Currently wet cleaning has become more diverse and gained a very high level of sophistication. Cleaning is applied throughout the entire manufacturing process of integrated circuits from incoming wafers to sawing and packaging or 3D-integration. As technology progresses, cleaning requirements become more stringent with smaller margins. Often selectivity is a major challenge as the contaminants to be removed resemble more closely that of the layers to be cleaned. This has led to a variety of tailored cleaning processes for: incoming wafers, pre-gate dielectrics, after-gate stack etch, pre-selective epitaxy, several photoresist removal steps and post-strip cleans, pre-metal deposition for silicide formation, post-silicide metal removal, post-CMP clean, and post-etch residue removal and cleaning. Specialized cleaning solutions have been introduced consisting of rather complex mixtures of acids, bases, solvents, surfactants, and chelating agents.

In recent years, high-κ metal gate stacks and alternative semiconductor materials such as SiGe, Ge, and even III-V compound semiconductors have been introduced or considered for future generation devices. Unlike Si, many of these materials tend to be attacked by “RCA''-like aqueous oxidizing cleaning mixtures. Therefore, alternatives must be developed such as solvent-based cleaning.

As part of the large effort spent over the last decades in this field, major international forums and symposia have been set up for the large “cleaning R&D” community to enhance and share their collective knowledge base. Many of these findings are published in numerous articles and conference proceedings. Particularly in this highly dynamic environment, it is very important to keep track of this acquired knowledge. The collective wisdom of this field is mostly in the minds of the participating researchers. The mission of this book is to extend this knowledge – capturing and synthesizing the major results and state-of-the-art knowledge of individual researchers and experts in the field of cleaning, surface conditioning, and contamination control.

This volume should become an essential part of a thorough training regimen on cleaning and surface preparation. It is a useful reference work for people active in the field and an absolute must for young engineers and researchers entering the dynamic and exciting discipline of cleaning and surface preparation. This handbook will help the industry avoid the unproductive and feared scenario of “reinventions” and provide a solid platform to build the new science and technology of cleaning and surface preparation for future applications far beyond the current scope of cleaning science.

Paul W. MertensLeuven, Belgium

October 24, 2010

Introduction

Semiconductor manufacturing continuously faces the most demanding technical challenges of any industry. As features have scaled, one of the most problematic areas of fabrication has been cleaning. Over the last few decades, the art of cleaning has turned into the science of surface preparation, critical cleaning, post-etch residue removal, and particle removal. Years ago the integrated circuit industry “borrowed” techniques from other industries – now the microelectronic engineers and scientists are the technology drivers. They work with the most advanced technology in the world making affordable microprocessors, controllers, and memory devices, so everyone can afford the newest electronic gadgets. These engineers work on devices that have minute features, rare materials, intricate equipment, and specialized processes. They help develop high-yielding, easily manufactured processes for the most sophisticated devices at the minimal cost and with the lowest environmental impact. This handbook celebrates these individuals – those who develop processes that are not physically present on a finished device. The chemicals used are all washed away, along with the contaminating metals, organics, and particles, yielding a pristine surface.

We have assembled authors with specific expertise to provide a thorough and thoughtful look at key range of cleaning topics in this field. The work is divided into three sections. The first six chapters address fundamental processes in chemical cleaning. Chapter 1 examines surface and colloid chemistry in cleaning, and Chapters 2 and 3 describe the chemistries of cleaning and etching processes. Chapter 4 details the surface phenomenon of cleaning. While chapters 5 and 6 discuss the design, delivery, and recycling of chemical formulations used in cleans. The second section (Chapters 7-14) covers a range of cleaning applications. Chapters 7, 8, 9, and 10 discuss cleaning and stripping of front end and back end of the line structures, Chapters 11 and 12 examine passivation and corrosion of copper and passivation of silicon and germanium. Wafer reclamation and wafer bonding preparation processes are discussed in Chapters 13 and 14. The last section of the book offers insight into the trends in cleans technologies. Chapter 15 details novel methods for evaluating the surface cleanliness and condition. The strip and cleans methods needed for the newest photolithography applications are discussed in Chapter 16.

Our book is dedicated to all the engineers past, present, and future that have and still toil feverishly and relentlessly to develop and utilize proven cleaning processes, and invent new ways to solve these crucial issues.

Karen A. ReinhardtSan Jose, California

Richard F. ReidyDenton, TexasNovember 2010.

PART 1

FUNDAMENTALS