About the Editors ............................................ xiii
List of Contributors ........................................... xv
Preface ....................................................... xix
Abbreviations ............................................... xxiii
Section I Low-k Materials ...................................... 1
1 Low-k: Materials: Recent Advances ............................ 3
Geraud Dubois and Willi Volksen
1.1 Introduction ............................................ 3
1.2 Integration Challenges .................................. 5
1.2.1 Process-Induced Damage ........................... 6
1.2.2 Mechanical Properties ............................ 9
1.3 Processing Approaches to Existing Integration Issues ... 10
1.3.1 Post-deposition Treatments ...................... 11
1.3.2 Prevention or Repair of Plasma-Induced
Processing Damage ............................... 14
1.3.3 Multilayer Structures ........................... 15
1.4 Material Advances to Overcome Current Limitations ...... 16
1.4.1 Silica Zeolites ................................. 16
1.4.2 Hybrid Organic-Inorganic: Oxycarbosilanes ....... 19
1.5 Conclusion ............................................. 22
References .................................................. 23
2 Ultra-Low-k by CVD: Deposition and Curing ................... 35
Vincent Jousseaume, Aziz Zenasni, Olivier Gourhant,
Laurent Favennec and Mikhail R. Baklanov
2.1 Introduction ........................................... 35
2.2 Porogen Approach by PECVD .............................. 37
2.2.1 Precursors and Deposition Conditions ............ 37
2.2.2 Mystery Still Unsolved: From Porogens to
Pores ........................................... 41
2.3 UV Curing .............................................. 42
2.3.1 General Overview of Curing ...................... 42
2.3.2 UV Curing Mechanisms ............................ 43
2.4 Impact of Curing on Structure and Physical
Properties: Benefits of UV Curing ...................... 49
2.4.1 Porosity ........................................ 49
2.4.2 Chemical Structure and Mechanical Properties .... 50
2.4.3 Electrical Properties ........................... 56
2.5 Limit/Issues with the Porogen Approach ................. 57
2.5.1 Porosity Creation Limit ......................... 58
2.5.2 Porogen Residues ................................ 59
2.6 Future of CVD Low-k .................................... 62
2.6.1 New Matrix Precursor ............................ 62
2.6.2 Other Deposition Strategies ..................... 64
2.6.3 New Deposition Techniques ....................... 66
2.7 Material Engineering: Adaptation to Integration
Schemes ................................................ 68
2.8 Conclusion ............................................. 70
References .................................................. 71
3 Plasma Processing of Low-fc Dielectrics ..................... 79
Hualiang Shi, Denis Shamiryan, Jean-François de Marneffe,
Huai Huang, Paul S. Ho and Mikhail R. Baklanov
3.1 Introduction ........................................... 79
3.2 Materials and Equipment ................................ 80
3.3 Process Results Characterization ....................... 82
3.4 Interaction of Low-k Dielectrics with Plasma ........... 85
3.4.1 Low-k Etch Chemistries .......................... 85
3.4.2 Patterning Strategies and Masking Materials ..... 87
3.4.3 Etch Mechanisms ................................. 88
3.5 Mechanisms of Plasma Damage ............................ 92
3.5.1 Gap Structure Studies ........................... 93
3.5.2 Effect of Radical Density ....................... 95
3.5.3 Effect of Ion Energy ............................ 96
3.5.4 Effect of Photon Energy and Intensity ........... 99
3.5.5 Plasma Damage by Oxidative Radicals ............ 103
3.5.6 Hydrogen-Based Plasma .......................... 105
3.5.7 Minimization of Plasma Damage .................. 108
3.6 Dielectric Recovery ................................... 112
3.6.1 CH4 Beam Treatment ............................. 112
3.6.2 Dielectric Recovery by Silylation .............. 113
3.6.3 UV Radiation ................................... 119
3.7 Conclusions ........................................... 121
References ................................................. 122
4 Wet Clean Applications in Porous Low-A Patterning
Processes .................................................. 129
Quoc Toan Le, Guy Vereecke, Herbert Struyf, Els Kesters
and Mikhail R. Baklanov
4.1 Introduction .......................................... 129
4.2 Silica and Porous Hybrid Dielectric Materials ......... 130
4.3 Impact of Plasma and Subsequent Wet Clean Processes
on the Stability of Porous Low-k Dielectrics .......... 134
4.3.1 Stability in Pure Chemical Solutions ........... 134
4.3.2 Stability in Commercial Chemistries ............ 135
4.3.3 Hydrophobicity of Hybrid Low-k: Materials ...... 138
4.4 Removal of Post-Etch Residues and Copper Surface
Cleaning .............................................. 141
4.5 Plasma Modification and Removal of Post-Etch 193 nm
Photoresist ........................................... 146
4.5.1 Modification of 193 nm Photoresist by Plasma
Etch ........................................... 146
4.5.2 Wet Removal of 193 nm Photoresist .............. 153
Acknowledgments ............................................ 166
References ................................................. 166
Section II Conductive Layers and Barriers .................... 173
5 Copper Electroplating for On-Chip Metallization ............ 175
Valery M. Dubin
5.1 Introduction .......................................... 175
5.2 Copper Electroplating Techniques ...................... 176
5.3 Copper Electroplating Superfill ....................... 177
5.3.1 The Role of Accelerator ........................ 177
5.3.2 The Role of Suppressor ......................... 178
5.3.3 The Role of Leveler ............................ 180
5.4 Alternative Cu Plating Methods ........................ 182
5.4.1 Electroless Plating ............................ 182
5.4.2 Direct Plating ................................. 182
5.5 Electroplated Cu Properties ........................... 184
5.5.1 Resistivity .................................... 184
5.5.2 Impurities ..................................... 184
5.5.3 Electromigration ............................... 185
5.6 Conclusions ........................................... 186
References ................................................. 187
6 Diffusion Barriers ......................................... 193
Michael Hecker and René Hübner
6.1 Introduction .......................................... 193
6.1.1 Cu Metallization, Barrier Requirements and
Materials ...................................... 193
6.1.2 Barrier Deposition Techniques .................. 195
6.1.3 Characterization of Barrier Performance ........ 196
6.2 Metal-Based Barriers as Liners for Cu Seed
Deposition ............................................ 198
6.2.1 Ta-Based Barriers .............................. 198
6.2.2 W-Based Barriers ............................... 209
6.2.3 Ti-Based Barriers .............................. 210
6.2.4 Further Systems ................................ 211
6.3 Advanced Barrier Approaches ........................... 212
6.3.1 Barriers for Direct Cu Plating ................. 212
6.3.2 Metal Capping Layers ........................... 214
6.3.3 Self-Forming Diffusion Barriers ................ 216
6.3.4 Self-Assembled Molecular Nanolayers and
Polymer-Based Barriers ......................... 218
6.4 Conclusions ........................................... 221
References ................................................. 221
Section III Integration and Reliability ....................... 235
7 Process Integration of Interconnects ....................... 237
Sridhar Balakrishnan, Ruth Brain and Larry Zhao
7.1 Introduction .......................................... 237
7.2 On-Die Interconnects in the Submicrometer Era ......... 237
7.3 On-Die Interconnects at Sub-100nm Nodes ............... 240
7.4 Integration of Low-k: Dielectrics in Sub-65 nm
Nodes ................................................. 241
7.4.1 Degradation of Dielectric Constant during
Integration .................................... 243
7.4.2 Integration Issues in ELK Dielectrics Due to
Degraded Mechanical Properties ................. 246
7.5 Patterning Integration at Sub-65 nm Nodes ............. 248
7.5.1 Patterning Challenges .......................... 249
7.6 Integration of Conductors in Sub-65 nm Nodes .......... 252
7.6.1 Narrow Line Copper Resistivity ................. 253
7.6.2 Integrating Novel Barrier/Liner Materials and
Deposition Techniques for Cu Interconnects ..... 254
7.6.3 Self-Forming Barriers and Their Integration .... 256
7.6.4 Integration to Enable Reliable Copper
Interconnects .................................. 257
7.7 Novel Air-Gap Interconnects ........................... 258
7.7.1 Unlanded Via Integration with Air-Gap
Interconnects .................................. 258
7.7.2 Air-Gap Formation Using Nonconformal
Dielectric Deposition .......................... 259
7.7.3 Air-Gap Formation Using a Sacrificial
Material ....................................... 260
References ................................................. 261
8 Chemical Mechanical Planarization for Cu-Low-k
Integration ................................................ 267
Gautam Banerjee
8.1 Introduction .......................................... 267
8.2 Back to Basics ........................................ 268
8.3 Mechanism of the CMP Process .......................... 268
8.4 CMP Consumables ....................................... 271
8.4.1 Slurry ......................................... 271
8.4.2 Pad ............................................ 273
8.4.3 Pad Conditioner ................................ 274
8.5 CMP Interactions ...................................... 276
8.6 Post-CMP Cleaning ..................................... 281
8.6.1 Other Defects .................................. 286
8.6.2 Surface Finish ................................. 286
8.6.3 E-Test ......................................... 287
8.7 Future Direction ...................................... 287
References ................................................. 288
9 Scaling and Microstructure Effects on Electromigration
Reliability for Cu Interconnects ........................... 291
Chao-Kun Hu, René Hübner, Lijuan Zhang, Meike Hauschildt
and Paul S. Ho
9.1 Introduction .......................................... 291
9.2 Electromigration Fundamentals ......................... 293
9.2.1 EM Mass Flow ................................... 293
9.2.2 EM Lifetime and Scaling Rule ................... 294
9.2.3 Statistical Test Method ........................ 296
9.2.4 Effect of Current Density on EM Lifetime ....... 297
9.3 Cu Microstructure ..................................... 299
9.3.1 X-ray Diffraction (XRD) ........................ 299
9.3.2 Electron Backscatter Diffraction in the
Scanning Electron Microscope ................... 301
9.3.3 Orientation Imaging Microscopy in the
Transmission Electron Microscope ............... 304
9.4 Lifetime Enhancement .................................. 306
9.4.1 Effect of а Та Liner ........................... 306
9.4.2 Upper-Level Dummy Vias ......................... 308
9.4.3 Plasma Pre-clean and SiH4 Soak ................. 310
9.4.4 CVD and ECDCu and the Effect of Nonmetallic
Impurities ..................................... 311
9.4.5 Cu Alloys ...................................... 314
9.4.6 CoWP Cap Near-Bamboo and Polycrystalline Cu
Lines .......................................... 319
9.5 Effect of Grain Size on EM Lifetime and Statistics .... 321
9.6 Massive-Scale Statistical Study of EM ................. 326
9.7 Summary ............................................... 329
Acknowledgments ............................................ 331
References ................................................. 331
10 Mechanical Reliability of Low-A Dielectrics ................ 339
Kris Vanstreels, Han Li and Joost J. Vlassak
10.1 Introduction .......................................... 339
10.2 Mechanical Properties of Porous Low-A Materials ....... 340
10.2.1 Techniques to Measure Mechanical Properties
of Thin Films .................................. 340
10.2.2 Effect of Porosity on the Stiffness of
Organosilicate Glass Films ..................... 342
10.2.3 Hybrid Dielectrics Containing Organic/
Inorganic Bridging Units ....................... 344
10.2.4 Effect of UV Wavelength and Porogen Content
on the Hardening Process of PECVD Low-A
Dielectrics .................................... 349
10.3 Fracture Properties of Porous Low-A Materials ......... 352
10.3.1 Adhesion Measurement Methods ................... 352
10.3.2 Fracture Toughness Measurement Techniques ...... 354
10.3.3 Effect of Porosity and Network Structure on
the Fracture Toughness of Organosilicate
Glass Films .................................... 355
10.3.4 Effects of UV Cure on Fracture Properties
of Carbon-Doped Oxides ......................... 357
10.3.5 Water Diffusion and Fracture Properties of
Organosilicate Glass Films ..................... 359
10.4 Conclusion ............................................ 361
References ................................................. 362
11 Electrical Breakdown in Advanced Interconnect
Dielectrics ................................................ 369
Ennis T. Ogawa and Oliver Aubel
11.1 Introduction .......................................... 369
11.1.1 Dual-Damascene Integration of Low-k
Dielectrics .................................... 370
11.1.2 Low-k Types and Integrating Low-k
Dielectrics .................................... 373
11.2 Reliability Testing ................................... 378
11.2.1 Measurement of Dielectric Degradation .......... 378
11.2.2 Reliability Analysis ........................... 390
11.3 Lifetime Extrapolation and Models ..................... 397
11.4 Future Trends and Concerns ............................ 403
Acknowledgments ............................................ 405
References ................................................. 405
Section IV New Approaches ..................................... 435
12 3D Interconnect Technology ................................. 437
John U. Knickerbocker, Lay Wai Kong, Sven Niese, Alain
Diebold and Ehrenfried Zschech
12.1 Introduction .......................................... 437
12.2 Dimensional Interconnected Circuits (3DICs) for
System Applications ................................... 438
John U. Knickerbocker
12.2.1 Introduction ................................... 438
12.2.2 System Needs ................................... 441
12.2.3 3D Interconnect Design and Architecture ........ 444
12.2.4 3D Fabrication and Interconnect Technology ..... 446
12.2.5 Trade-offs in Application Design and Product
Applications ................................... 464
12.2.6 Summary ........................................ 466
Acknowledgments ............................................ 467
12.3 Advanced Microscopy Techniques for 3D Interconnect
Characterization ...................................... 467
Lay Wai Kong, Sven Niese, Alain Diebold and
Ehrenfried Zschech
12.3.1 Scanning Acoustic Microscopy ................... 467
12.3.2 IR Microscopy .................................. 473
12.3.3 Transmission X-ray Microscopy and Tomography ... 474
12.3.4 Microstructure Analysis ........................ 480
12.4 Summary ............................................... 486
References ................................................. 486
13 Carbon Nanotubes for Interconnects ......................... 491
Mizuhisa Nihei, Motonobu Sato, Akio Kawabata, Shintaro
Sato and Yuji Awano
13.1 Introduction .......................................... 491
13.2 Advantage of CNT Vias ................................. 492
13.3 Fabrication Processes of CNT Vias ..................... 493
13.4 Electrical Properties of CNT Vias ..................... 496
13.5 Current Reliability of CNT Vias ....................... 498
13.6 Conclusion ............................................ 501
Acknowledgments ............................................ 501
References ................................................. 501
14 Optical Interconnects ...................................... 503
Wim Bogaerts
14.1 Introduction .......................................... 503
14.2 Optical Links ......................................... 505
14.2.1 Waveguides ..................................... 507
14.2.2 Waveguide Filters and (De)multiplexers ......... 510
14.2.3 Transmitter: Light Source ...................... 513
14.2.4 Transmitter: Modulators ........................ 514
14.2.5 Receiver: Photodetector ........................ 517
14.2.6 Power Consumption and Heat Dissipation ......... 517
14.2.7 Different Materials ............................ 518
14.2.8 Conclusion ..................................... 519
14.3 The Case for Silicon Photonics ........................ 519
14.3.1 Waveguides and WDM Components ................. 519
14.3.2 Modulators, Tuners and Switches ................ 523
14.3.3 Photodetectors ................................. 526
14.3.4 Light Sources .................................. 526
14.3.5 Conclusion ..................................... 527
14.4 Optical Networks on a Chip ............................ 528
14.4.1 WDM Point-to-Point Links ....................... 529
14.4.2 Bus Architecture ............................... 529
14.4.3 (Reconfigurable) Networks ...................... 530
14.5 Integration Strategies ................................ 532
14.5.1 Front-End-of-Line Integration .................. 533
14.5.2 Backside Integration ........................... 535
14.5.3 Back-End-of-Line Integration ................... 535
14.5.4 3D Integration ................................. 536
14.5.5 Flip-Chip Integration .......................... 537
14.5.6 Conclusion ..................................... 537
14.6 Conclusion ............................................ 538
References ................................................. 538
15 Wireless Interchip Interconnects
Takamaro Kikkawa ........................................... 543
15.1 Introduction ......................................... 547
15.2 Wireless Interconnect Technologies ................... 547
15.2.1 Figure of Merit for Wireless Interconnects .... 549
15.2.2 Capacitively Coupled Wireless Interconnects ... 550
15.2.3 Inductively Coupled Wireless Interconnects .... 553
15.2.4 Antennas and Propagation Conclusion ........... 561
15.3 References ............................................ 561
Index ......................................................... 565
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