黑硅电池中你需要掌握的半导体基础工艺知识.ppt

Etching stop Timed etching: not good for 10um membrane Factors determining etching rate: temperature, concentration, aging, stirring, light, wafer irregularity, surface preparation (1) V-groove technique (visual inspection: not suitable for mass production) (2) Boron (P+) etch stop 7?1019 cm-3 ? etching rate drops 50 times (EDP) 1-20 um controllable Membrane in tension (B Si) Not effective with KOH ncompatible with CMOS process membrane beam Process Design: How to make beams? wafer (p) oxidation doping patterning (HF) ion implantation diffusion EDP crystal etching top view Anisotropic Etching Rules Etching blocked by {111} (slowest etching plane) Long time etching - Arbitrary shape opening: surrounded by largest possible rectangle - Island (mesa) mask: disappears! Masks Si3N4 is best, very slow etch rate，Selectivity 1000 SiO2 works, selectivity ? 100 Mask Design KOH Etches exposed corners quickly Use star pattern or create interior corners to create outer corners Corner Compensation (1) Convex corner attack Junghoon Lee, Ph.D. Thesis (2) Compensation: etchant dependence (concave corner never attacked) Fundamental of Microfabrication, Marc Madou (3) Various compensation structures Fundamental of Microfabrication, Marc Madou (4) Fastest etching plane: 411 E411/E100 = 1.6 @ 15% KOH = 1.3 @ 40% KOH Not a depends on temperature (60-100 deg C) (5) Length of 110 compensation structure How long does etching go in {110} direction when it goes down in {100} direction by a certain depth? L1/H=[E411 projected to {110}]/E100 L1: length {110} H: depth {100} Then L1=2H*E411/E100 Pressure Sensor p-Si n-Si epi p-Si piezoresistor p-Si Si3N4 p-Si p-Si p-Si Pyrex? glass /articles/0700/62/main.shtml?? Bulk Micromachining Generally Wet Etching is Isotropic WET ETCHING OF SILICON DIOXIDE 7:1 NH4F/HF gives about 1000 ?/min etch rate at room T TYPES OF BHF WET ETCHING OF SILICON NITRIDE 热磷酸腐蚀氮化物 HOT PHOSPHORIC ACID ETCH OF SI3N4 HOT PHOSPHORIC ACID NITRIDE ET