[信息与通信]ReviewofPlasmaEtchFundamentals.ppt

REVIEW OF PLASMAFUNDAMENTALSConcepts and Terms Review of Plasma Etch Fundamentals The Plasma IONIZATION Radicals: Recombination: The Glow: Constituents Within a Plasma: Some Terms Used to Evaluate Process Results ETCH DIRECTIONALITYIN A PLASMA CONTROLLING ETCH DIRECTIONALITY Etch Directionality and Mean Free Path Poly Etch Process Requirement High selectivity over gate oxide For 0.25um,0.18um ploy gate, gate oxide thickness is around 20-30A High fidelity mask replication CD control, normally 10% High selectivity to PR No undercutting Profile control Anisotropic No reentrant profile Residue free No poly stringers Damage free No gate oxide breakdown No charging Poly Etch Material and Chemistry Material Polysilicon (gate, capacitor,resistor,fuse,interconnect etc.) WSi and Polysilicon(gate) Single Crystal Silicon(STI) Chemistry Variety of gases containing Fluorine, Chlorine and Bromine In general, gases containing F are more chemical etch in nature,and gases containing Cl and Br are more ion-assisted etch in nature HBr and O2 are added to increase the selectivity over SiO2 Br-gas have higher selectivity over PR and SiO2 than Cl-gas but more residue at high pressure SiF4, SiCl4 and SiBr4 are the final products of etching silicon (Boiling Point: SiF4 -86C SiCl4 57.6 SiBr4 154 Selectivity To change the selectivity in Si and SiO2 etching, the following way can be used Carbon blocking method (Increase SiO2 to Si selectivity) Volatility of end product Materials which form volatile compounds etch must faster than materials which form in-volatile compounds Thermodynamic principle Thermodynamically “downhill” reactions proceed much faster then “uphill” reactions (use Cl and Br containing gas) Si+4Cl SiCl4(downhill) Si+4Br SiBr4(downhill) SiO2+4Cl SiCl4+O2(uphill) SiO2+4Br SiBr4+O2(downhill) Br containing achieve the highest Si to SiO2 selectivity Adding O2 to increase Si to SiO2 selectivity Ion bombardment Energy(d