Advanced Analytical Techniques for Semiconductor Assembly Materials and Processes Jason Chou and Sze Pei Lim Indium Corporation
Agenda Company introduction Semiconductor assembly roadmap challenges Fine pitch, low stand-off Warpage Smaller Cu-pillar solder cap, fewer flux amount More pre-process and thermal oxidation on bond pad surface Five case studies in using surface analysis tools to drive understanding of semiconductor assembly materials
Company Introduction Indium Corporation is a premier materials supplier to global industries including: Electronics assembly Semiconductor Solar energy Thin-film Thermal management
Indium Corporation Global Manufacturing and Sales Offices
From Mobile to Wearable to IoT Technology driving force: lighter, thinner, smaller
Solder Joint Evolution Solder Joint by Package Type Flip-Chip Solder Joint High-Pb Solder Eutectic Solder (PbSn63) SnAg2 Sn(?)
Assembly and Process Challenges for FC-BGA Thinner substrates and thinned die increase warpage Processes oxidize / contaminate the ball-attach pad surface Bottom Cu/OSP pads badly oxidized
Process and Material Challenges in Flip-Chip Solder Microbump Thickness & alloy Oxidation Contamination IMC thickness No-clean Flux Residue level (ULR) Wetting power Compatibility with MUF/CUF Rheology Substrate or Leadframe Leadframe / Substrate Surface treatment Oxidation Contamination Warpage
Advanced Analytical Techniques for Semiconductor Assembly Advanced analytical and preparation techniques now necessary to understand failure modes Auger spectroscopy SIMS (secondary ion mass spectrometry) FIB (focused ion beam) Drive deep understanding of mechanisms
Surface Analysis by SIMS / Auger Auger Electron: 0.4 ~ 5nm Secondary Electron (SIMS): <50 nm SEM EDX: 1000 ~ 3000 nm SIMS Auger SEM EDX
Case Study 1: Solder Cap Contamination SEM and EDX analysis The SEM did not find foreign or abnormal material EDX analysis showed high C and O levels Good solder joint Bad solder joint
Case Study 1: Solder Cap Contamination Solder cap shows abnormal one has dark surface with impurity SIMS data shows abnormal one has high C, O content Abnormal Normal
Case Study 2: Wafer Bumping Cleaning Optimization Auger test method is very sensitive to carbon, oxygen (oxide) Good tool for process optimization STD STD (exclude S, Ca) 40S50DI 40S25DI 60S50DI 60S25DI 70S50DI 70S25DI Name Start KE Peak KE End KE PP At. % PP At. % PP At. % PP At. % PP At. % PP At. % PP At. % PP At. % C KL1 256.1 270.6 272.0 20.55 31.98 31.21 32.64 26.02 15.77 14.68 15.15 Sn MN1 424.1 430.1 433.0 20.95 32.60 39.18 32.20 39.60 46.46 52.40 54.42 O KL1 506.5 516.5 530.3 19.4 30.19 21.98 27.40 29.30 27.89 28.02 24.63 S LM1 148.0 155.6 163.8 17.86 Ca LM2 290.6 295.6 302.0 17.87 Ag MN1 350.0 366.4 384.5 3.36 5.23 7.63 7.76 5.08 9.88 4.91 5.79 100 64.26 100 100 100 100 100 100 % 35 30 25 20 15 10 5 0 Carbon Condition
Case Study 3: Leadframe Surface Treatment Surface roughness (adhesion enhancement) treatment is used to increase MUF/CUF adhesion Different surface treatment will induce different wetting performance Scanned Area 3.0µ m
1 19 37 55 73 91 109 127 145 163 181 199 217 235 253 271 289 307 325 343 1 19 37 55 73 91 109 127 145 163 181 199 217 235 253 271 289 307 325 343 1 19 37 55 73 91 109 127 145 163 181 199 217 235 253 271 289 307 325 343 3.0µ m Scanned Area Case Study 3: Leadframe Surfaces with SIMS Analysis SIMS analysis quantifies oxidation level and oxide depth Important for process tuning 3.50E+08 3.00E+08 2.2 3.50E+08 3.00E+08 2.50E+08 2.50E+08 2.00E+08 C 2.00E+08 C 1.50E+08 1.00E+08 O Cu 1.50E+08 1.00E+08 O Cu 5.00E+07 5.00E+07 3.50E+08 3.00E+08 2.50E+08 1.8 2.00E+08 1.50E+08 1.00E+08 C O Cu 5.00E+07
BGA Process and Thermal Treatment 2~4 times Substrate SMT Reflow Die Bond Wire bond D/B Cure Saw Singulation BM Pre-clean PMC Molding Pre-Baking Many thermal process before BM will induce pad surface oxidation, which will induce yield loss (missing ball ) and low productivity
1 12 23 34 45 56 67 78 89 100 111 122 133 144 155 166 177 188 1 12 23 34 45 56 67 78 89 100 111 122 133 144 155 166 177 188 1 11 21 31 41 51 61 71 81 91 101 111 121 131 141 151 161 1 13 25 37 49 61 73 85 97 109 121 133 145 157 169 181 193 205 Case Study 4: BM Pad Surface with SIMS Analysis 2~4 times Substrate SMT Reflow Die Bond Wire bond D/B Cure Saw Singulation BM Pre-clean PMC Molding Pre-Baking 1.40E+08 1.20E+08 Fresh substrate 3.50E+06 3.00E+06 Post Molding cure 1.00E+08 8.00E+07 6.00E+07 4.00E+07 2.00E+07 Cu 12C 16O 32S 58Ni 138Ba 197Au 2.50E+06 2.00E+06 1.50E+06 1.00E+06 5.00E+05 O, C 12C 16O 32S 58Ni 138Ba 9.00E+07 8.00E+07 7.00E+07 6.00E+07 5.00E+07 4.00E+07 3.00E+07 2.00E+07 1.00E+07 Flux clean x1 12C 16O 32S 58Ni 138Ba 197Au 9.00E+07 8.00E+07 7.00E+07 6.00E+07 5.00E+07 4.00E+07 3.00E+07 2.00E+07 1.00E+07 Flux clean x2 12C 16O 32S 58Ni 138Ba 197Au
Supplier-B Supplier-A Case Study 5: FIB Analysis on OSP Substrate Deposit Pt for FIB analysis OSP Cu Fresh Cu OSP Substrate
1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106 113 1 11 21 31 41 51 61 71 81 91 101 111 121 131 141 151 161 1 10 19 28 37 46 55 64 73 82 91 100 109 118 127 136 145 154 163 1 7 13 19 25 31 37 43 49 55 61 67 73 79 85 91 97 103 109 Case Study 5: FIB and SIMS post-flux clean Indium WS-575-C shows better cleaning efficiency on OSP substrate base on FIB and SIMS analysis result WS-575-C 4.00E+07 3.50E+07 5-4-F 4.00E+07 3.50E+07 5-6-F 3.00E+07 3.00E+07 2.50E+07 2.00E+07 1.50E+07 12C 16O 32S 58Ni 2.50E+07 2.00E+07 1.50E+07 12C 16O 32S 58Ni 1.00E+07 63Cu 1.00E+07 63Cu 5.00E+06 5.00E+06 5.00E+07 4.50E+07 K-5-NC 5.00E+07 4.50E+07 K-5-F 4.00E+07 4.00E+07 3.50E+07 12C 3.50E+07 12C 3.00E+07 16O 3.00E+07 16O 2.50E+07 32S 2.50E+07 32S 2.00E+07 58Ni 2.00E+07 58Ni 1.50E+07 63Cu 1.50E+07 63Cu 1.00E+07 197Au 1.00E+07 197Au 5.00E+06 5.00E+06 Competitor OSP residue
Summary Advanced analytical techniques create: Knowledge of the mechanisms of flux activity and usage Improved materials and processes Higher yield, improved reliability, and speed time to market
Thank you!