Through Silicon ViasEECS713Daniel Herr

Why Through Silicon Vias (TSVs)?

•Demand for Faster, Smaller Chips•Allows for Higher Density 3D chips•Higher Density –> Higher Bandwidth•Lead to significant Interconnect Length

reduction vs. Edge Connected Multi-Chip Modules (MCMs)

Multi-Chip Module (3)

What is a TSV• Via through a Silicon Substrate• Generally Copper Via• Oxide Layer• Bump• Interposer Interconnect

TSV Layout (1)

Multiple TSV Stack-up (1)

Modeling GSG TSV• Transmission Line Model• Resistance and Inductance behave as normal transmission

line• Conductivity of the Silicon along with the oxide layer

complicate the Model.

Equivalent Circuit Model of TSV (1) Equivalent Circuit Model of Interposer (1)

Channel Loss of TSV and Interconnect

Effect of Interposer Silicon Conductance (1) Effect of TSV Silicon Conductance (1)

Effect of Interposer Oxide Capacitance (1) Effect of TSV Oxide Capacitance (1)

TSVs vs. Edge Connected MCMs• TSVs generally allow for shorter trace length• The Characteristic Impedance of TSV and interposer are

frequency dependent. This can make it very challenging to impedance match. However; the Conductivity of the Silicon Substrate attenuates the reflection.

• MCM has less loss than TSVs until the frequency is high enough.

Characteristic Impedance vs Frequency (1) Channel Loss vs. Frequency (1)

Substrate Coupling• Electro-Magnetic Coupling (What we’ve dealt with in

class)• Because Silicon is a Semi-Conductor, the Conductivity

of the Substrate is non-trivial. This leads to Parasitic Substrate Coupling

TSV Test Setup (Side) (2)

TSV Test Setup (Top-Down) (2)

Effects of Substrate Coupling

Voltage Transfer Function From Signal 1 to Signal 2 (2)

(2) (2)

References• 1: Measurement and Analysis of a High-Speed TSV Channel (Kim,

Heegon; Cho, Jonghyun; et al.): http://ieeexplore.ieee.org.www2.lib.ku.edu:2048/xpls/icp.jsp?arnumber=6268425

• 2: Trhough Silicon Via and 3-D Wafer/Chip Stacking Technology (Takahashi, Kenji and Sekiguchi, Masahiro): http://ieeexplore.ieee.org.www2.lib.ku.edu:2048/xpl/articleDetails.jsp?tp=&arnumber=6248929&queryText%3Dsilicon+high+speed+signals

• 3: EECS713 Notes (Professor Allen)