Process Variations in Microsystems Manufacturing

Preface

Acknowledgments

Contents

Chapter 1: Introduction

1.1 From Vacuum Tubes to Microsystems

1.2 MEMS Microsystems

1.3 Some of the Important Attributes of MEMS Microsystems

1.4 Organization of This Book

References

Other Information

Chapter 2: An Overview of MEMS Microsystems

2.1 Introduction

2.2 Microsensors and Microactuators

2.2.1 MEMS Microsensors

2.2.1.1 Resistive

2.2.1.2 Piezoresistive

2.2.1.3 Capacitive

2.2.1.4 Piezoelectric

2.2.1.5 Tunneling

2.2.1.6 Magnetic

2.2.1.7 Photoconduction

2.2.1.8 Thermoelectric

2.2.1.9 Diodes

2.2.2 MEMS Microactuators

2.2.2.1 Electrostatic

2.2.2.2 Piezoelectric

2.2.2.3 Thermal

2.2.2.4 Shape-Memory Alloys (SMA)

2.2.2.5 Magnetic

2.3 Microsystems Manufacturing Processes

2.4 Batch Fabrication

2.5 Some Basics of Microsystems Manufacturing

2.5.1 Differences Between IC and MEMS Manufacturing

2.5.2 Microsystems Feature Sizes

2.6 Some Material Basics Regarding Semiconductors and Silicon

2.7 Summary

References

Chapter 3: Microsystems Manufacturing Methods: Integrated Circuit Processing Steps

3.1 Introduction

3.2 Basic IC Processing Steps

3.2.1 Thin-Film Growth and Deposition Techniques

3.2.1.1 Thermal Oxidation

3.2.1.2 Chemical Vapor Deposition

3.2.1.2.1 Atmospheric Chemical Vapor Deposition (ACVD)

3.2.1.2.2 Low-Pressure Chemical Vapor Deposition (LPCVD)

3.2.1.2.3 Plasma-Enhanced Chemical Vapor Deposition (PECVD)

3.2.1.2.4 Atomic Layer Deposition (ALD)

3.2.1.3 Physical Vapor Deposition (PVD)

3.2.1.3.1 Evaporation

3.2.1.3.2 Sputtering

3.2.2 Impurity Doping

3.2.2.1 Thermal Diffusion

3.2.2.2 Ion Implantation

3.2.3 Photolithography

3.2.4 Rapid Thermal Anneal (RTA)

3.2.5 Planarization

3.2.6 Etching

3.2.7 Clean and Strip

3.3 Summary

References

Chapter 4: Microsystems Manufacturing Methods: MEMS Processes

4.1 Introduction

4.2 MEMS Substrate Material Types

4.3 MEMS Materials Deposition Processing Steps

4.3.1 MEMS Thin-Film Materials Deposited on IC Equipment

4.3.1.1 Thin-Film Semiconductors

4.3.1.1.1 Silicon (Si)

4.3.1.1.2 Silicon-Germanium (SiGe)

4.3.1.1.3 Germanium (Ge)

4.3.1.1.4 Silicon Carbide (SiC)

4.3.1.1.5 Diamond

4.3.1.2 Metals

4.3.1.3 Thin-Film Metal Oxides

4.3.1.4 Dielectrics

4.3.1.4.1 Silicon Nitride (SiN)

4.3.1.4.2 Silicon Dioxide (SiO2)

4.3.1.5 Polymers

4.3.1.5.1 SU-8

4.3.1.5.2 PDMS

4.3.1.5.3 Polyimide

4.3.1.6 Ceramics

4.3.1.7 Special MEMS Materials

4.3.1.7.1 Piezoelectric Materials

4.3.1.7.2 Shape-Memory Alloys (SMAs)

4.3.1.7.3 Magnetic Materials

4.3.2 MEMS Specific Processing Steps

4.3.2.1 Electrochemical Deposition

4.3.2.2 MEMS Lithography

4.3.2.2.1 Contact Photolithography

4.3.2.2.2 Front-to-Back Contact Photolithography

4.3.2.2.3 Direct-Write Laser Photolithography

4.3.2.2.4 Grayscale Photolithography

4.3.2.2.5 X-Ray Lithography

4.3.2.2.6 E-Beam Lithography

4.3.2.2.7 Lithography on Large Topography

4.3.2.2.8 Lift-Off Patterning

4.3.2.2.9 Image Reversal Photoresists

4.3.2.2.10 Photolithography on Transparent Substrates

4.4 MEMS Micromachining Methods

4.4.1 Bulk Micromachining

4.4.1.1 Wet Chemical Etchants

4.4.1.1.1 Isotropic Wet Chemical Etchants

4.4.1.1.2 Anisotropic Wet Chemical Etchants

4.4.1.2 Gas-Phase Isotropic Chemical Etchants

4.4.1.3 Deep Reactive Ion Etching (DRIE) of Silicon

4.4.1.4 Deep, High-Aspect Ratio RIE of Fused Silica, Quartz, and Glass

4.4.1.5 Deep, High-Aspect Ratio RIE of Silicon Carbide (SiC)

4.4.2 Surface Micromachining

4.4.3 Wafer Bonding

4.4.4 LIGA

4.4.5 Hot Embossing

4.4.6 Other MEMS Micromachining Technologies

4.4.6.1 Electro-Discharge Micromachining

4.4.6.2 Laser Micromachining

4.4.6.3 Focused Ion Beam (FIB) Micromachining

4.4.6.4 Electrochemical Fabrication (EFAB)

4.5 Summary

References

Chapter 5: Metrology for Microsystems Manufacturing

5.1 Introduction

5.2 Fabrication Metrology Equipment and Methods

5.2.1 Optical Microscopy

5.2.2 Fluorescence Microscopy

5.2.3 Confocal Microscopy

5.2.4 Stereomicroscopy

5.2.5 Scanning Electron Microscope (SEM)

5.2.6 Automated Scanning Electron Microscope

5.2.7 Thin-Film Thickness

5.2.7.1 Interferometry

5.2.7.2 Ellipsometry

5.2.7.3 Stylus Profilometry

5.2.8 Four-Point Probe

5.2.9 Thin-Film Stress Measurement

5.2.10 Particle Measurements

5.2.11 Noncontact Optical Profilometry

5.2.12 Wafer Bonding Inspection

5.3 Specialized Metrology Equipment and Methods

5.3.1 Focused Ion Beam

5.3.2 Scanning Tunneling Microscopy (STM)

5.3.3 Atomic Force Microscopy (AFM)

5.3.4 Energy-Dispersive X-Ray Spectroscopy (EDXS)

5.4 Highly Specialized Material Analysis Methods

5.5 Electrical Material Properties Test Methods

5.5.1 Junction Depth Measurements

5.5.2 Spreading Sheet Resistance

5.6 Summary

References

Chapter 6: Microsystems Material Properties

6.1 Introduction

6.2 Residual Stress and Young´s Modulus

6.2.1 Young´s Modulus

6.2.2 Residual Stress

6.3 Mechanical Test Structures

6.3.1 Test Structures for Young´s Modulus

6.3.2 Thin-Film Residual Stress Test Structures

6.3.3 Stress Gradients

6.3.4 Tests for Other Mechanical Material Properties

6.4 Electrical Test Structures

6.5 Thin-Film Material Properties

6.5.1 Thermal SiO2

6.5.2 LPCVD Polysilicon

6.5.3 LPCVD Silicon Dioxide (SiO2)

6.5.4 LPCVD Silicon Nitride (SiN)

6.5.5 PECVD Silicon Dioxide (SiO2)

6.5.6 PECVD Silicon Nitride (SiN)

6.5.7 PECVD Polycrystalline Silicon

6.5.8 Evaporative Physical Vapor Deposition

6.5.9 Sputter Physical Vapor Deposition

6.5.9.1 Sputter-Deposited Silicon

6.5.10 Electrochemical Deposition

6.6 Summary

References

Chapter 7: Microsystems Process Integration, Testing, and Packaging

7.1 Introduction

7.2 What Is Process Integration?

7.3 How Is Process Integration Performed?

7.4 What Is an Integrated MEMS Process Sequence?

7.5 Examples of MEMS Microsystems Process Technologies

7.5.1 PolyMUMPS Process Technology

7.5.1.1 Some Important Elements About PolyMUMPS

7.5.2 Digital Light Processor (DLP) Technology

7.5.2.1 Some Key Elements About the DLP Process Technology

7.6 Process Integration and Manufacturing Variations

7.6.1 Causes of Device Parameter Variations in Process Sequences

7.6.2 An Example of Parameter Variations for a Process Technology: The PolyMUMPS Process

7.7 Microsystems Design Rules

7.7.1 MEMS Microsystems Design Rules

7.7.2 Design Rule Checking

7.8 MEMS Microsystems Testing

7.8.1 Example of MEMS Microsystems Testing

7.8.2 MEMS Microsystems Device Trimming

7.8.3 MEMS Microsystems Calibration

7.9 MEMS Microsystems Packaging

7.10 Summary

References

Chapter 8: Device Parameter Variations in Microsystems Manufacturing

8.1 Introduction

8.2 Manufacturing Variations

8.3 Measurement of Manufacturing Variations

8.4 Bias and Random Variations

8.5 Resolution, Precision, and Accuracy

8.6 Comparison of the Dimensional Parameter Variations in Manufacturing Technologies

8.7 The Nature of Random Parameter Variations

8.8 Discrete Probability Distributions

8.9 Some Examples of Statistical Analysis of Variations

8.9.1 Confidence Interval for Manufacturing Large Samples (N > 30)

8.9.2 Confidence Interval for Small Samples (N < 30)

8.9.3 Hypothesis Testing for Small Sample Sizes (N < 30)

8.9.4 Hypothesis Testing of Goodness of Fit

8.9.5 Sample Size Required to Estimate Population Mean

8.9.6 Example of Use of the Hypergeometric Distribution

8.9.7 Example of Poisson Distribution

8.10 Impact of Physics and Random Parameter Variations

8.11 Combination of Both Bias and Random Manufacturing Parameter Variations

8.12 Device Output Behavior Variation Due to Parameter Variations

8.13 Example of Device Output Behavior Variation Analysis

8.14 Simplified Variation Analysis

8.15 Important Generalizations

8.16 Review of Methods for Variation Analysis

8.16.1 Worst-Case Variation Analysis

8.16.2 Non-worst-Case Variation Analysis

8.16.2.1 Non-sampling, Non-worst-Case Variation Analysis

8.16.2.2 Monte Carlo Variation Analysis

8.17 Summary

References

Chapter 9: Yield Analysis and Quality Assurance and Control Methods Used in Microsystems Manufacturing

9.1 Introduction

9.2 Importance of Manufacturing Yield

9.3 Definitions of Microsystems Manufacturing Yield

9.4 Microsystems Manufacturing Yield Monitoring and Analysis

9.4.1 Functional Yield

9.4.1.1 Functional Yield Models Based on Point Defects

9.4.1.2 Functional Yield Measurement Tools

9.4.2 Parametric Yield

9.4.2.1 Parametric Yield Model

9.4.2.2 An Example of a Parametric Yield Model

9.5 Yield Estimations Using Sampling Methods

9.5.1 Yield Estimation Using Regionalization

9.5.2 Yield Estimation Using Simplicial Approximation

9.5.3 Monte Carlo Yield Estimation

9.5.3.1 Confidence Intervals for Monte Carlo Yield Analysis

9.6 Statistical Process Control (SPC)

9.6.1 Control Charts for Variables

9.6.2 Control Charts for Attributes

9.6.3 Identification of Non-random Patterns in Control Charts

9.6.4 Process Capability

9.6.5 Rational Subgroups

9.6.5.1 Sampling Methods for Rational Subgroups

9.7 Summary

References

Chapter 10: Managing Parameter Variations in Microsystems Device Design

10.1 Introduction

10.2 Relationships Between Process Sequence and Parameter Variations

10.3 Overview of MEMS Device Design and Modeling

10.4 Example of the Design Levels for a MEMS Device

10.5 MEMS Design for Manufacturability

10.5.1 MEMS Device Design for Manufacturability

10.5.2 MEMS Process Sequence Design for Manufacturability

10.5.3 MEMS Microsystems Partitioning

10.6 Overview of MEMS Development

10.7 MEMS Design for Manufacturability Recommendations

10.8 Managing Device Parameter Variations in MEMS Design

10.8.1 Design Centering

10.8.2 Parameter Variation Reduction

10.8.3 Device Size Scaling

10.8.4 Acceptance Range Increase

10.8.5 Best Practices in Layout Design

10.8.6 Further Comments About MEMS Design Methods

10.9 MEMS Design in Multidimensional Spaces

10.10 MEMS Design Methods Using Monte Carlo Techniques

10.10.1 Design Centering Using Monte Carlo

10.11 Sensitivity Analysis

10.11.1 Generalized Sensitivity Analysis Methods

10.11.2 Optimizing Manufacturing Cost Function

10.12 Summary

References

Index