Preface to the Third Editioniii

Preface to the Third Editioniii

Contentsv

11

Typical Equipment for Optical Coating Production1

1.1. INTRODUCTION1

1.2. GENERAL REQUIREMENTS2

1.2.1. The Vacuum5

1.2.2. Deposition Sources32

1.2.3. Fixturing and Uniformity70

1.2.4. Temperature Control83

1.2.5. Process Control88

1.3. TYPICAL EQUIPMENT91

1.4. ALTERNATIVE APPROACHES96

1.5. UTILITIES100

1.6. REFERENCES105

2113

Materials and Processes113

2.1. PROCESS KNOW-HOW113

2.1.1. Film Growth Models and Observations114

2.1.2. Chiral and Sculptured Coatings127

2.1.3. Stress in Coatings128

2.1.4. Designing Optical Coatings to Control Stress132

2.1.5. Laser Damage in Coatings145

2.1.6. Rain Erosion of Coatings149

2.2. MATERIALS150

2.2.1. Silicon Compounds151

2.2.2. Titanium Oxides, TiO through TiO2161

2.2.3. Magnesium Compounds170

2.2.4. Germanium183

2.2.5. Thorium Fluoride185

2.2.6. Zinc Sulfide186

2.2.7. Zinc Selenide190

2.2.8. Lead Telluride190

2.2.9. Hafnium Compounds191

2.2.10. Niobium and Neodymium Compounds193

2.2.11. Yttrium Compounds194

2.2.12. Zirconium Dioxide195

2.2.13. Tantalum Pentoxide198

2.2.14. Aluminum Compounds199

2.2.15. Cerium Compounds202

2.2.16. Scandium Oxide204

2.2.17. Zinc Oxide204

2.2.18. Lead Fluoride205

2.2.19. Calcium Fluoride206

2.2.20. Barium Fluoride207

2.2.21. Ytterbium Fluoride207

2.2.22. Lanthanum Compounds208

2.2.23. Rhodium209

2.2.24. Chromium210

2.2.25. Aluminum211

2.2.26. Silver212

2.2.27. Gold214

2.2.28. Indium-Tin Oxide215

2.2.29. Electrochromic Materials, Tungsten Oxide, Etc.218

2.2.30. Cubic Boron Nitride220

2.2.31. Bismuth Oxide223

2.2.32. Gadolinium Fluoride223

2.2.33. Lithium Fluoride224

2.2.34. Toxicity of Coating Materials224

2.2.35. Relative Cost of Coating Materials224

2.3. MIXED MATERIALS and TERNARY OXIDES225

2.4. CRYSTAL MONITOR CONTROLLER SETUP229

2.4.1 The Problem230

2.4.2 The Solution230

2.4.3 Setting Ramp and Soak Times231

2.4.4 PID Settings232

2.4.5 Soak Level Before The Shutter Opens235

2.4.6 Control Delay After Shutter Opens237

2.4.7. Adhesion Failures, Etc.237

2.5. IONS AND ION SOURCES240

2.5.1. Ion to Atom Arrival Ratio (IAAR) and Its Implications240

2.5.2. Kaufman Gridded Source244

2.5.3. Cold Cathode Source247

2.5.4. End-Hall Source249

2.5.5. IS1000/PS1500 Plasma/Ion Source252

2.5.6. Behavior of Three Types of Plasma/Ion Sources255

2.5.7. Ion/Plasma Sources with Fluoride Coatings267

2.6. OTHER PROCESSES TO CONSIDER267

2.6.0. Surface Preparation and Cleaning267

2.6.1. Physical Vapor Deposition268

2.6.2. Dip, Spin, and Spray Coatings269

2.6.3. Chemical Vapor Deposition270

2.6.4. Plasma-Enhanced CVD271

2.6.5. Plasma Polymerization273

2.6.6. Hard Carbon Coatings273

2.6.7. Atomic Layer Deposition275

2.7. SUMMARY278

2.8. REFERENCES278

3312

Thin Film Monitoring and Control312

3.1 OVERVIEW312

3.2 SIMPLE MONITORS317

3.2.1. "Eyeball" and Measured Charge318

3.2.2. Optical Thickness Monitors322

3.2.3. Automation versus Manual Monitoring326

3.2.4. Spectral Requirement Factors327

3.3 CRYSTAL MONITORS334

3.3.1. Crystal Thickness Controllers334

3.3.2. Precision versus Accuracy335

3.3.3. Crystal Control of Eyeglass Coatings338

3.3.4. Calibrations and Variations343

3.3.5. Tooling Factors344

3.3.6. Variations345

3.4 OPTICAL MONITORING346

3.4.1. Effect of Rate Variations346

3.4.2. Optical Monitor with the Method of Schroedter347

3.4.4. Level Cut Monitoring350

3.4.5. Turning Point Monitoring353

3.4.6. Termination Point Simulation356

3.4.7. Noise Effects359

3.4.8. Relative Merits of Four Strategies366

3.4.9. NBP Filter Comparison of Monitoring Strategies366

3.4.10. Software Examples371

3.5 ERROR COMPENSATION AND DEGREE OF CONTROL375

3.5.1. Narrow Bandpass Filter Monitoring375

3.5.2. How to Grab a Rattlesnake379

3.5.3. Broad Band AR Coating Monitoring380

3.6 NBP FILTER MONITORING385

3.6.1. Signal to Noise in Monitoring387

3.6.2. Special Layers in NBP Monitoring388

3.7 LAST TWO LAYERS OF NBP FILTERS389

3.7.1 Types of Final Layer Monitoring Techniques390

3.7.2 Basis of Predicted Thickness392

3.7.3. Effects of Final Layer Monitoring Techniques394

3.7.4. Summary of the Last Two Layers of a NBP Filter399

3.8 FENCEPOST MONITORING400

3.8.1 Monitoring in General Cases401

3.8.2 Monitoring Non-QWOT NBP Filters405

3.8.3 New Approach to NBP Monitoring and Control410

3.8.4 Preliminary Conclusions on Fencepost Monitoring419

3.8.5. Adjusting Thicknesses in NBP Filters419

3.8.6. Further on Procedures for Adjusted Designs426

3.9 DIRECT VERSUS INDIRECT428

3.10 CHIP CHANGERS429

3.11 ERROR ACCUMULATION432

3.12 SENSITIVITY TO ERRORS432

3.12.1. Geometrical Factors432

3.12.2. Effects of Errors on the Average Transmission435

3.12.3. Sensitivity of Turning Points in Monitoring437

3.12.4. Total Error Sensitivity of the Average Transmission438

3.12.5. Error Compensation in the Monitoring439

3.13 CONSTANT LEVEL MONITORING444

3.13.1 Sensitivity and Correction Strategies446

3.13.2. Sensitivity versus Layer Termination Point446

3.13.3. Sensitivity Versus g-Value448

3.13.4. Constant Level Monitoring Strategies452

3.14 PASSIVE VERSUS ACTIVE, STEERING457

3.14.1. Passive Versus Active Optical Monitoring457

3.14.2. Steering the Monitoring Signal Result457

3.14.3. Departures from Ideal457

3.14.4. Steering Concept458

3.14.5. Algorithm459

3.14.6. More on Photometrics461

3.14.7. Example Case461

3.14.8. Lessons Learned462

3.14.9. Results464

3.14.10. A Problem Case465

3.15 PRECOATED MONITOR CHIPS466

3.15.1. Eliminating the Precoated Chip466

3.15.2. General Design Procedure468

3.15.3. Specific Design Procedure468

3.15.4. Results of the Procedure472

3.16 OTHER EFFECTS ON OPTICAL MONITORS474

3.16.1 Error Due to Drift in the Monitoring Wavelength474

3.16.2. Effects of Thin Film Wedge on the Monitor Chip475

3.16.3. Error Due to Width of the Monitoring Passband477

3.17 DESENSITIZING FOR %T/%R ERRORS479

3.18 OVERCOMING ABSORPTION488

3.19 REVERSE & FORWARD ENGINEERING491

3.19.1. Narrow Bandpass Filter491

3.19.2. Special "Multichroic" Beamsplitter492

3.19.3. Very Broadband Antireflection Coating493

3.19.4. The Rest of the Story499

3.20 SIMULATION OF ERROR EFFECTS IN FP MONITOING500

3.21 DIRECT DOUBLE BEAM MONITORING509

3.21.1 Single Beam versus Double Beam Optical Monitors509

3.21.2. Intermittent Monitoring509

3.22 ELLIPSOMETRIC MONITORING512

3.23 BROAD BAND OPTICAL MONITORING518

3.24 ADVICE, FOR WHAT IT IS WORTH525

3.25 SUMMARY526

3.26 REFERENCES529

4537

Process Development537

4.1. INTRODUCTION537

4.2. DESIGN OF EXPERIMENTS METHODOLOGY541

4.2.1. Process Flow Diagram541

4.2.2. Cause-and-Effect Diagram542

4.2.3. Control, Noise, or Experiment543

4.2.4. Screening and Pareto Ranking544

4.2.5. Standard Operating Procedures546

4.3. DESIGN OF THE EXPERIMENTS: EXAMPLES546

4.3.1. A Central Composite Design for Aluminizing548

4.3.2. A Box-Behnken Design for IAD Deposition of TiO2552

4.4. REAL LIFE EXAMPLE PROBLEM SOLVING559

4.5. ANOTHER REAL LIFE EXAMPLE566

4.6. SUMMARY576

4.7. REFERENCES577

Appendix579

Table of Conversion Factors579

INDEX580