Vlsi Design Expert

VLSI Design Expert

Before Starting

1. Full custom or standard cell design?
2. Which technology node?
3. Analog, digital, or mixed-signal circuit?

Core Expertise Areas

CMOS Logic

NMOS: n-channel MOSFET, conducts when gate voltage high. PMOS: p-channel MOSFET, conducts when gate voltage low. CMOS inverter: PMOS pull-up, NMOS pull-down, low static power. CMOS gate: pull-up network PMOS, pull-down network NMOS, dual networks. Propagation delay: function of load capacitance and drive strength.

Custom Layout

Design rules: minimum widths, spacings, enclosures for each layer. Poly, diffusion, metal layers: stack of conducting and insulating layers. Transistor layout: gate poly crosses active diffusion, contacts on source and drain. Matching: common centroid layout for differential pairs and current mirrors. Parasitic extraction: RC parasitics from layout affect circuit performance.

Physical Design Flow

Floorplanning: partition design into blocks, place macro cells and I/O. Placement: position standard cells to minimize wire length and meet timing. Clock tree synthesis: distribute clock with balanced skew and minimal jitter. Routing: connect cells with metal wires respecting design rules. Sign-off: DRC, LVS, ERC, timing closure, power analysis.

Advanced Nodes

FinFET: 3D transistor, multiple gates, better electrostatic control below 20nm. GAA: gate all around, nanosheets wrap gate completely, used at 3nm and below. Low-k dielectric: reduce parasitic capacitance between metal layers. Multi-patterning: achieve sub-wavelength features using multiple lithography passes.

Best Practices

• Always run DRC and LVS before tapeout
• Extract parasitics and re-simulate critical analog circuits
• Design for manufacturing with OPC and redundant vias
• Meet electromigration rules for all metal layers

Common Pitfalls

Related Skills

• digital-electronics-expert
• electronics-expert
• circuit-analysis-expert