Chemical-Mechanical Polishing of Low Dielectric Constant Polymers and Organosilicate Glasses

by Borst, Christopher Lyle; Gill, William N.; Gutmann, Ronald J.

• ISBN13: 9781402071935
• ISBN10: 1402071930
• Format: Hardcover
• Copyright: 2002-08-01
• Publisher: Kluwer Academic Pub

Summary

As semiconductor manufacturers implement copper conductors in advanced interconnect schemes, research and development efforts shift toward the selection of an insulator that can take maximum advantage of the lower power and faster signal propagation allowed by copper interconnects. One of the main challenges to integrating a low-dielectric constant (low-kappa) insulator as a replacement for silicon dioxide is the behavior of such materials during the chemical-mechanical planarization (CMP) process used in Damascene patterning. Low-kappa dielectrics tend to be softer and less chemically reactive than silicon dioxide, providing significant challenges to successful removal and planarization of such materials. The focus of this book is to merge the complex CMP models and mechanisms that have evolved in the past decade with recent experimental results with copper and low-kappa CMP to develop a comprehensive mechanism for low- and high-removal-rate processes. The result is a more in-depth look into the fundamental reaction kinetics that alter, selectively consume, and ultimately planarize a multi-material structure during Damascene patterning.

Table of Contents

Preface	xi
Acknowledgements	xiii
Overview of IC Interconnects	1	(16)
Silicon IC BEOL Technology Trends	2	(4)
SIA Roadmap Interconnect Projections	6	(1)
Low-κ Requirements and Materials	7	(5)
Fluorinated Glasses	8	(1)
Spin-On Glasses and Silsesquioxanes	8	(1)
Organosilicate Glasses	9	(1)
Polymers	9	(2)
Fluorinated Polymers	11	(1)
Porous Media	11	(1)
Need for Low-κ CMP Process Understanding	12	(2)
Summary	14	(1)
References	14	(3)
Low-κ Interlevel Dielectrics	17	(28)
Fluorinated Glasses	19	(2)
Silsesquioxanes	21	(3)
Organosilicate Glasses	24	(3)
Polymers	27	(7)
Fluorinated Hydrocarbons	34	(1)
Nanoporous Silica Films	35	(3)
Other Porous Materials	38	(2)
References	40	(5)
Chemical-Mechanical Planarization (CMP)	45	(26)
CMP Process Description	47	(3)
CMP Processes With Copper Metallization	50	(5)
Oxide CMP	50	(1)
Copper CMP	50	(2)
Damascene Patterning	52	(3)
CMP Targeted Results and Challenges	55	(1)
CMP of Low-κ Materials	55	(7)
CMP Process Models	62	(4)
Contact Mechanics-Based Models	63	(1)
Fluid Mechanics-Based Models	64	(2)
Langmuir-Hinshelwood Surface Kinetics in CMP Modeling	66	(5)
References	71	(1)
CMP of BCB and SiLK Polymers	71	(26)
Removal Rate in Copper Slurries	71	(3)
Surface Roughness	74	(4)
Surface and Bulk Film Chemistry	78	(7)
Angle-Resolved Surface Results	78	(6)
Depth Profiling Results	84	(1)
Effect of Cure Conditions on BCB and Silk Removal	85	(3)
Variation in Cure Conditions	86	(1)
Effect of Cure Conditions on Removal Rate	86	(2)
Effect of CMP and BCB and Silk Film Hardness	88	(3)
Comparison of BCB and Silk CMP with Other Polymer CMP	91	(2)
Summary	93	(1)
References	94	(3)
CMP of Organosilicate Glasses	97	(22)
Effect of Film Carbon Content	97	(6)
Removal Rate in Oxide Slurries	98	(3)
Removal Rate in Copper Slurries	101	(2)
Surface Roughness	103	(3)
Surface and Bulk Film Chemistry	106	(4)
XPS Surface Results	107	(2)
FTIR Bulk Profiling Results	109	(1)
Copper Damascene Patterning with OSG Dielectrics	110	(7)
Hardmasks or Dielectric Cap Layers	111	(1)
Low-κ Etching	112	(1)
CMP Integration	113	(4)
Summary	117	(1)
References	117	(2)
Low-κ CMP Model Based on Surface Kinetics	119	(42)
Isolation of the Chemical Effects in Silk CMP	120	(2)
CMP with Simplified ``Model'' Silk Slurries	122	(7)
Removal Rate Dependence on Slurry Reactant Concentration	124	(3)
KH Phthalate Slurry for Copper CMP Applications	127	(1)
SiLK Removal Rate Dependence on Velocity	128	(1)
Phenomenological Model for CMP Removal	129	(5)
Applicability to the CMP of BCB and Silk	131	(2)
Applicability to the CMP of Organosilicate Glasses	133	(1)
Five Step Removal Model Using Modified Langmuir-Hinshelwood Kinetics for Silk CMP	134	(18)
Five Step Surface Mechanism	135	(4)
Implementation into 3-D Fluid Mechanics and Mass Transport Models	139	(2)
Results	141	(11)
Two Step Removal Model Using Heterogeneous Catalysis for Silk CMP	152	(3)
Two Step Surface Mechanism	152	(2)
Results	154	(1)
Extendibility of Model to Describe the CMP of Other Materials	155	(3)
Copper	156	(1)
Dielectrics	156	(2)
References	158	(3)
Copper CMP Model Based Upon Fluid Mechanics and Surface Kinetics	161	(20)
Flow Model	163	(1)
Copper Removal Model	164	(8)
Mass Transport of Oxidizer to the Wafer Surface	165	(1)
Kinetic Surface Steps	166	(2)
Copper Removal Rate and Effectiveness Factor	168	(2)
Kinetic Rate Parameters	170	(1)
Solution Procedure	171	(1)
Model Results	172	(4)
Copper CMP Experiments with Potassium Dichromate Based Slurry	176	(3)
Summary	179	(1)
References	179	(2)
Future Directions in IC Interconnects and Related Low-κ ILD Planarization Issues	181	(46)
Planarization of Interconnects with Ultra Low-κ ILDS	182	(3)
Alternatives to Conventional CMP	182	(1)
Non-CMP Approaches to Planarization	183	(2)
Alternatives for the Post-Copper/Ultra Low-κ Interconnect Era	185	(8)
Alternative Materials	185	(1)
Alternative Distribution for Signals and Clocks	186	(2)
Non-electrical Distribution of Signals and Clocks	188	(1)
Non-Planar Integrated Assemblies-Three Dimensional (3D) Integration	189	(4)
3D Wafer-Scale Integration Using Dielectric Bonding Glues and Inter-Wafer Interconnection with Copper Damascene Patterning	193	(6)
Wafer Bonding	194	(3)
Inter-wafer Interconnect	197	(2)
Comparison with Other Wafer-Scale 3D Integration Technologies	199	(1)
Summary and Conclusions	199	(1)
References	200	(3)
APPENDICES
Appendix A: Experimental Procedures and Techniques	203	(18)
Appendix B: XPS Depth-Profile Data	221	(4)
Appendix C: CMP Data for Anomalous Silk Removal Behavior	225	(2)
Index	227