fd-soi (fully-depleted soi)

FD-SOI (Fully-Depleted Silicon-On-Insulator) Overview FD-SOI is a planar transistor technology built on ultra-thin silicon-on-insulator wafers where the silicon channel is thin enough (< 7nm) to be fully depleted of mobile carriers, providing FinFET-like performance with a simpler planar process. How It Works - SOI Wafer: Thin silicon film (~6-7nm) on top of a buried oxide layer (BOX, ~20-25nm) on bulk silicon. - Fully Depleted: The channel is so thin that the gate fully controls it—no floating body effects. - Back-Bias: Voltage applied to the substrate below the BOX modulates threshold voltage in real-time (body biasing). This is FD-SOI's unique advantage. Back-Bias Advantage - Forward Body Bias (FBB): Apply positive voltage to substrate → lower Vt → faster switching. Use for performance mode. - Reverse Body Bias (RBB): Apply negative voltage → raise Vt → lower leakage. Use for low-power/sleep mode. - Dynamic adjustment: Software can switch bias on-the-fly, adapting performance vs. power in real-time. FD-SOI vs. FinFET - FD-SOI: Simpler process (planar, fewer masks), lower cost, body biasing, good for RF/analog. Limited scaling beyond 12nm. - FinFET: Better scaling to 3nm, higher drive current density, industry standard for high-performance. Adoption - GlobalFoundries 22FDX (22nm) and 12FDX (12nm): Primary FD-SOI offerings. - Samsung 18FDS (18nm): Used in automotive and IoT. - Applications: Automotive, IoT, RF, low-power mobile, edge AI—markets where cost and power matter more than peak performance.