Ion Implantation Techniques

In recent years, ion implantation has developed into the major doping technique for integrated circuits. Several series of conferences have dealt with the application of ion implantation to semiconductors and other materials (Thousand Oaks 1970, Garmisch-Partenkirchen 1971, Osaka 1974, Warwick 1975, Boulder 1976, Budapest 1978, and Albany 1980). Another series of conferences was devoted more to implantation equipment and tech­ niques (Salford 1977, Trento 1978, and Kingston 1980). In connection with the Third International Conference on Ion Implantation: Equipment and Tech­ niques, held at Queen's University,' Kingston, Ontario, Canada, July 8-11, 1980, a two-day instructional program was organized parallel to an implan­ tation conference for the first time. This implantation school concentra­ ted on aspects of implantation-equipment design. This book contains all lectures presented at the International Ion Implantation School organized in connection with the Fourth International Conference on Ion Implantation: Equipment and Techniques, held at the Convention Center, Berchtesgaden, Germany, September 13-17, 1982. In con­ trast to the first .school, the main emphasis in thiS school was placed on practical aspects of implanter operation and application. In three chap­ ters, various machine aspects of ion implantation (general concepts, ion sources, safety, calibration, dOSimetry), range distributions (stopping power, range profiles), and measuring techniques (electrical and nonelec­ tri ca 1 measu ri ng techni ques, annea 1 i ng) are di scussed. In the appendi x, a review of the state of the art in modern implantation equipment is given.

I Machine Aspects of Ion Implantation.- Ion Implantation System Concepts.- 1. Implanter Concepts.- 1.1 Post-Analysis.- 1.2 Pre-Analysis.- 1.3 Post-Analysis with Post-Acceleration.- 2. Criteria for the Ideal Semiconductor-Manufacturing Implanter.- 3. Low-Current and Medium-Current Implanter Concepts.- 4. High-Current Implanter Concepts.- 5. System-Limiting Aspects H.- 5.1 Throughput.- 5.2 Wafer Heating.- 5.3 Energy Range.- 5.4 Wafer Size and Wafer Tilting.- 5.5 Charge-up Phenomena.- 5.6 Contamination.- 6. Human Engineering.- 6.1 Operation of an Implanter.- 6.2 Automatic Implantation Control.- 6.3 Safety.- References.- Ion Sources.- 1. Introduction.- 2. Ion Implantation Requirements from the Ion Source.- 3. The Principle of Operation of an Ion Source.- 3.1 The Cathode.- 3.2 The Anode.- 3.3 The Extraction Aperture.- 3.4 The Magnetic Field.- 3.5 The Plasma.- 3.6 The Source Feed System.- 4. Beam Extraction.- 5. Beam Formation.- 6. Beam Quality.- 7. Beam Content.- 8. Ion Source Selection.- 8.1 Low-Current Machines.- 8.2 Medium-Current Machines.- 8.3 High-Current Machines.- 8.4 Surface Treatment Machines.- 9. Types of Arc Discharge Source.- 9.1 Calutron Sources.- 9.2 Magnetron Ion Sources.- 9.3 Penning Ion Source.- 9.4 Plasmatron Ion Sources.- 9.5 Hollow Cathode Sources.- 9.6 Sputtering Sources.- 9.7 Sources for the Surface Treatment of Metals.- 9.8 Other Sources.- 10. Sources Not Utilising an Arc Discharge.- 10.1 Surface Ionisation Sources.- 10.2 Molten Metal Field Emission Ion Sources.- 11. Operational Characteristics of Arc Discharge Sources.- 11.1 Arc Voltage.- 11.2 Arc Current.- 11.3 Magnetic Field Strength.- 11.4 Arc Chamber Pressure.- 11.5 Feed Material.- 11.6 Temperature.- 11.7 Source Condition.- 11.8 Extraction Voltage.- 12. Ion Source Feed Materials.- 12.1 Gaseous Feed Materials.- 12.2 Low Vapour Pressure Materials.- 12.3 Very Low Vapour Pressure Materials.- 12.4 Chemical Synthesis.- 12.5 Feed Materials.- 13. Materials of Construction.- 13.1 Arc Chamber Materials.- 13.2 Cathode Materials.- 13.3 Insulator Materials.- 13.4 Magnetic Materials.- 13.5 Electrical Conductors.- 13.6 Coating Materials.- 14. Ion Sources in Commercial Ion Implanters.- 14.1 Sources for Low-Current Machines.- 14.2 Medium-Current Machines.- 14.3 High-Current Machines.- 15. Conclusions.- References.- Faraday Cup Designs for Ion Implantation.- 1. Introduction.- 2. Dose Control by Current Measurement.- 2.1 Assumptions.- 2.2 Discrepancies.- 3. Limitations in Dose Measurements with Faraday Cups.- 3.1 Ion Beam Space-Charge Effects.- 3.2 Secondary and Tertiary Particle Emissions in the Faraday Cup...- 3.3 Target Area Effects.- 3.4 Electrical Errors.- 4. Design Principles for Faraday Cups.- 5. Faraday Cup Design for Dose Measurement for Scanned Beams.- 5.1 Beam Space Charge and Secondary Particle Collection.- 5.2 Implant Area.- 5.3 Electrical Considerations.- 6. Faraday Cup Design for Dose Measurement for Scanned Targets.- 6.1 Beam Space Charge, Surface Neutralization and Secondary Particle Collection.- 6.2 Implant Area.- 6.3 Electrical Considerations.- 7. In Situ Monitoring of Dose Uniformity.- 7.1 Uniformity Control for Scanned Beams.- 7.2 Uniformity Control for Scanned Targets.- 8. Hybrid Systems.- 9. Summary.- References.- Safety and Ion Implanters.- 1. Radiation.- 1.1 Mechanisms of X-Ray Production.- 1.2 X-Ray Production Efficiency.- 1.3 Generation of the Reverse Electron Flow Responsible for X-Ray Production.- 1.4 Mechanisms of X-Ray Absorption.- 1.5 Radiation Units.- 1.6 Example of a Radiation-Level Calculation.- 2. Poisonous Materials.- 3. High Voltage.- 4. Mechanical Hazards.- 5. Fire, Flooding, Earthquake.- 5.1 Fire.- 5.2 Flooding.- 5.3 Earthquake.- References.- II Ion Ranges in Solids.- The Stopping and Range of Ions in Solids.- 1. Introduction.- 2. Review of Some Stopping and Range Tables.- 2.1 Stopping Power Tables.- 2.2 Range Tables.- 3. Stopping Powers for Ions in Solids.- 3.1 Nuclear Stopping Powers.- 3.2 The Electronic Stopping of Ions in Solids.- 3.3 Empirical Ion Stopping Powers.- References.- The Calculation of Ion Ranges in Solids with Analytic Solutions.- 1. Introduction.- 2. The Basic Ideas of the Model.- 2.1 Directional Spread of Ion Motion During the Slowing-Down Process.- 2.2 Connection Between Angular Spread Parameter t and Energy Loss.- 2.3 Calculation of the Mean Projected Range.- 3. Application of the Model.- 3.1 Heavy-Ion Ranges as an Example of Possible Analytic Treatment.- 3.2 Differential Equation and Universal Algorithm for Projected Ranges.- 3.3 Universal Analytic Approximation for Projected Ranges.- 4. Projected Ranges in Compound Targets.- 5. Higher Terms and Precision.- 6. Appendix.- 6.1 Numerical Evaluation of Projected Ranges on Programmable.- Pocket Calculators (PRAL).- 6.2 Numerical Evaluation of Projected Ranges on Computers (DIMUS) 169 References.- Range Distributions.- 1. Introduction.- 2. Gaussian Profiles I?.- 3. Pearson Distributions.- 4. Other Distributions.- 5. Two-Layer Targets.- 6. Implantation and Sputtering.- 7. Lateral Spread.- 8. Appendix: Range Program.- References.- III Measuring Techniques and Annealing.- Electrical Measuring Techniques.- 1. Introduction.- 2. Background.- 2.1 Why Post-Implantation Dosimetry.- 2.2 Incident and Retained Dose.- 2.3 Absolute and Relative Dose Measurement.- 2.4 Sample Contamination.- 2.5 Post-Implantation Annealing.- 2.6 Basic Assumptions.- 3. Measurement Techniques.- 3.1 Resistance Measurements.- 3.2 Capacitance Voltage.- 3.3 Device Parameters.- 3.4 Depth Profiles.- 4. Limitations of Electrical Measurements.- 5. Standards Exercises.- References.- Wafer Mapping Techniques for Characterization of Ion Implantation Processing.- 1. Introduction.- 2. High-Dose Characterization: Sheet Resistance Measurements.- 2.1 The van der Pauw Resistor.- 2.2 The Four-Point Probe.- 3. Sheet Resistance Wafer Mapping.- 3.1 Performance Norms for Dose Accuracy and Uniformity.- 3.2 Implanter Diagnostics.- 3.3 Effects of Annealing Conditions.- 3.4 Wafer Heating During Implantation.- 4. Low-Dose Characterization.- 4.1 Device Parameters.- 4.2 High-Frequency Capacitance Technique.- 5. Summary.- References.- Non-Electrical Measuring Techniques.- 1. Introduction.- 2. Structure of Implantation-Related Analytical Problems.- 3. Review of Measurement Techniques: Impurity Profiling.- 3.1 Abrasive Techniques.- 3.2 Non-Destructive Methods.- 4. Secondary Ion Mass Spectroscopy (SIMS).- 4.1 Sputtering and Secondary Ionization.- 4.2 Experimental Techniques.- 5. Rutherford Backscattering (RBS).- 5.1 Concepts of RBS.- 5.2 Experimental Technique.- 6. Damage Evaluation by Channeling Techniques.- 6.1 Channeling of Energetic Light Ions.- 6.2 Channeling Spectra and Lattice Disorder.- 6.3 Lattice Location.- References.- Annealing and Residual Damage.- 1. Introduction.- 2. Characterization of Damage and Defects.- 3. Primary Implantation Damage.- 4. Thermal Annealing.- 5. Residual Defects.- 6. Effects of Residual Defects.- References.- IV Appendix: Modern Ion Implantation Equipment TM.- Evolution and Performance of the Nova NV-10 Predep™ Implanter.- 1. Introduction.- 2. Performance Specifications.- 3. Dose Control.- 4. Throughput.- 4.1 Implant Time.- 4.2 The Wafer Handling Sequence Between Implants.- 4.3 Throughput Values.- 5. Uptime.- 6. Beam Current and Source Performance.- 7. Energy.- 8. Wafer Cooling.- 8.1 Uncooled Disks.- 8.2 Radiation-Enhanced Cooling.- 3.3 2-Point Clamp Technique.- 8.4 Full-Ring Centrifugal Clamp.- 9. Preventive Maintenance.- 10. Process Control (Datalock™).- 11. Neutral Beams.- 11.1 Dose Error.- 11.2 Dose Non-uniformity.- 11.3 Depth Profile Errors.- 11.4 Secondary Particle Effects.- 12. Contamination.- 13. Wafer Handling.- 14. Summary.- References.- Ion Implantation Equipment from Veeco.- 1. Introduction.- 2. A Versatile Ion Implantation System.- 3. A High-Production Ion Implantation System.- 4. Ion Implanter for GaAs - Device Development and Production.- The Series III A and IIIX Ion Implanters.- 1. Introduction.- 2. The Series III Machine.- 3. The Series IIIA Machine.- 4. The Series IIIX Machine.- 5. The Electron Flood Gun.- 6. The Process Verification System.- 7. Specifications.- 7.1 IIIA.- 7.2 IIIX.- References.- Standard High-Voltage Power Supplies for Ion Implantation.- The IONMICROPROBE A-DIDA 3000-30 for Dopant Depth Profiling and Impurity Bulk Analysis.- 1. Introduction.- 2. Some Features of the IONMICROPROBE A-DIDA 3000-30.- 3. Some IONMICROPROBE A-DIDA 3000-30 Applications.- References.- List of Contributors.