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On‐wafer thermomechanical characterization of a thin film polyimide formed by vapor deposition polymerization for through‐silicon via applications: Comparison to plasma‐enhanced chemical vapor deposition SiO 2
Author(s) -
Fukushima Takafumi,
Murugesan Mariappan,
Bea JiCheol,
Hashimoto Hiroyuki,
Kino Hisashi,
Tanaka Tetsu,
Koyanagi Mitsumasa
Publication year - 2020
Publication title -
journal of polymer science
Language(s) - English
Resource type - Journals
eISSN - 2642-4169
pISSN - 2642-4150
DOI - 10.1002/pol.20200094
Subject(s) - polyimide , chemical vapor deposition , materials science , pyromellitic dianhydride , wafer , thin film , plasma enhanced chemical vapor deposition , polymerization , chemical engineering , x ray photoelectron spectroscopy , deposition (geology) , dielectric , composite material , polymer , analytical chemistry (journal) , polymer chemistry , nanotechnology , organic chemistry , optoelectronics , chemistry , layer (electronics) , sediment , engineering , biology , paleontology
Abstract Thin‐film polyimides were prepared by solvent‐less vapor deposition polymerization (VDP) from pyromellitic dianhydride and 4,4′‐oxydianiline at 200 °C for liner dielectric formation of vertical interconnects called through‐silicon vias (TSVs) used in three‐dimensionally stacked integrated circuit (3DICs). FTIR, synchrotron XPS, and TDS were employed for determining the imidization ratio, and in addition, the mechanical properties, coefficient of thermal expansion and Young's modulus, of the VDP polyimide were characterized on Si wafers. The VDP polyimide exhibited extremely high conformality, beyond 75%, toward high‐aspect‐ratio deep Si holes, compared with conventional SiO 2 prepared by plasma‐enhanced chemical vapor deposition. The adhesion between the VDP polyimide and Si wafer was enhanced by an Al‐chelate promotor. Remarkably, the VDP polyimide TSV liner dielectrics showed much less thermomechanical stresses applied to the Si surrounding the TSVs than the plasma‐chemical vapor deposition SiO 2 . The small keep‐out zone is expected for scaling down highly reliable 3DICs for the upcoming real artificial intelligence society.