Process integration and testing of TSV Si interposers for 3D integration applications
Lannon, J., Hilton, J., Huffman, C., Lueck, M., Vick, E., Goodwin, S., Cunningham, G., Malta, D., Gregory, C., & Temple, D. (2012). Process integration and testing of TSV Si interposers for 3D integration applications. In 2012 IEEE 62nd Electronic Components and Technology Conference (ECTC 2012), San Diego, CA, May 29-June 1, 2012 (pp. 268-273) https://doi.org/10.1109/ECTC.2012.6248839
Two 3D Si interposer demonstration vehicles containing through-Si vias (TSVs) were successfully fabricated using integration of two different TSV formation and multilevel metallization (MLM) process modules. The first Si interposer vehicles were made with a dual damascene frontside MLM (5 levels), backside TSV (unfilled, vias-last), and backside metallization (2 levels) process sequence on standard thickness 6” wafers. The front-side MLM was comprised of 4 metal routing layers (2 ?m Cu with 2 ?m oxide interlayer dielectric) and 1 metal pad layer. Electrical yield as high as 100% was obtained on contact chain test structures containing 26,400 vias between the front-side MLM layers, while the average contact resistance between the dual damascene levels was <; 4 M? per via. TSV dimensions of 100 and 80 ?m diameter and 6:1 aspect ratio were investigated. DRIE bottom clear process conditions were optimized for each via dimension to produce 100% yield on TSV contact chains with up to 540 vias. The optimized DRIE conditions also resulted in TSV resistance below 30 M? and sufficient TSV isolation resistance (>;100M?/via at 3.3V) for the target application. Functional testing of two die (4 cm × 3.7 cm die size) showed that 99% of the functional circuit path nets had acceptable continuity and isolation. The second Si interposer vehicles were fabricated using a vias-first TSV (filled, blind vias), wafer-level packaging (WLP) front-side MLM (2 levels), wafer thinning (via reveal), and WLP-MLM (1 level) process sequence on stock 6” wafers. Via dimensions for the viasfirst interposers were 50 ?m diameter × 315 ?m depth or 80 ?m diameter × 315 ?m depth (6:1 or 4:1 aspect ratios). The front and backside MLM was formed with a 2 ?m Cu routing layer and one of two spin-on dielectrics (polyimide or ALX) for evaluation of polymer dielectric process com- atibility with Cu-filled TSVs and thinned wafer processing. Details of the process modules and process integration required to realize the TSV Si interposers are described.