TY - THES

T1 - Three-Dimensional Integration of Power Electronic Devices Using Wafer Level Deposited Copper Sinter Paste

AU - Karner, Stefan

N1 - embargoed until 30-06-2020

PY - 2019

Y1 - 2019

N2 - Bond materials are presently intensively investigated for the production of cost-efficient, lead-free, highly conductive and highly reliable interconnections between high power semiconductor devices. In general, pure Cu interconnects, which are fabricated by paste sintering, match these demands and have been further shown to surpass other interconnect technologies regarding cost efficiency, electromigration resistance and high-temperature reliability. In the course of this master thesis, thermal compression and thermosonic bonding were investigated for the three dimensional integration of power electronic devices. Furthermore, wafer level deposited copper (Cu) sinter paste was employed as bonding material, which permits a low-ohmic contact among the stacked devices. A systematic design of experiments (DoE) was conducted to evaluate a mild parameter setup for thermal compression bonding of two power devices. In more detail, the pressureless curing temperature, bonding specifications and an optional post-bond annealing step were considered as parameters within this DoE. The resulting sinter joints were investigated with regards to their morphology, interfacial adhesion and mechanical strength by conducting scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), scanning acoustic microscopy (SAM) and shear test measurements. Moreover, linear regression analysis was conducted to investigate the influence of each parameter on the mechanical quality of the sinter joint in more detail. A feasibility study of thermosonic bonding for the vertical integration of semiconductor devices was additionally performed on dummy chips, with the aim of achieving lower temperature and pressure specifications in comparison to thermal compression bonding. In summary, it was shown that an electrically working interconnect with sufficiently good mechanical properties can be manufactured by thermal compression bonding with temperatures and pressures below 400 °C and 50 MPa. The introduction of ultrasonic energy during bonding additionally shifted the bonding parameters to significantly lower values.

AB - Bond materials are presently intensively investigated for the production of cost-efficient, lead-free, highly conductive and highly reliable interconnections between high power semiconductor devices. In general, pure Cu interconnects, which are fabricated by paste sintering, match these demands and have been further shown to surpass other interconnect technologies regarding cost efficiency, electromigration resistance and high-temperature reliability. In the course of this master thesis, thermal compression and thermosonic bonding were investigated for the three dimensional integration of power electronic devices. Furthermore, wafer level deposited copper (Cu) sinter paste was employed as bonding material, which permits a low-ohmic contact among the stacked devices. A systematic design of experiments (DoE) was conducted to evaluate a mild parameter setup for thermal compression bonding of two power devices. In more detail, the pressureless curing temperature, bonding specifications and an optional post-bond annealing step were considered as parameters within this DoE. The resulting sinter joints were investigated with regards to their morphology, interfacial adhesion and mechanical strength by conducting scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), scanning acoustic microscopy (SAM) and shear test measurements. Moreover, linear regression analysis was conducted to investigate the influence of each parameter on the mechanical quality of the sinter joint in more detail. A feasibility study of thermosonic bonding for the vertical integration of semiconductor devices was additionally performed on dummy chips, with the aim of achieving lower temperature and pressure specifications in comparison to thermal compression bonding. In summary, it was shown that an electrically working interconnect with sufficiently good mechanical properties can be manufactured by thermal compression bonding with temperatures and pressures below 400 °C and 50 MPa. The introduction of ultrasonic energy during bonding additionally shifted the bonding parameters to significantly lower values.

KW - 3D integration

KW - vertical integration

KW - power semiconductor

KW - thermal compression bonding

KW - thermosonic bonding

KW - copper

KW - sinter paste

KW - stencil printing

KW - wafer level

KW - 3D Integration

KW - vertikale Integration

KW - Leistungshalbleiter

KW - Thermokompressionsbonden

KW - Thermosonicbonden

KW - Kupfer

KW - Sinterpaste

KW - Schablonendruck

KW - Waferebene

M3 - Master's Thesis

ER -