applications such as microresonators that involve pairs of “centipedes-like” micro
plate electrodes with overlapped “fingers”:
● DRIE process may produce deep trenches with θ ≈ 0 (i.e., near perfect vertical walls).
There are two types of etching techniques: ● Wet etching （湿法刻蚀)involving the use of strong chemical solvents （化学溶剂） . ● Dry etching（干法刻蚀） using high energy plasmas（高能电浆）.
● Plasma etching.（等离子刻蚀）
● Reactive ion etching. Deep reactive ion etching (DRIE)（深反应离子刻蚀）
Dry etching
The principal plasma etching.
1、how to generate plasma 2、the process of plasma etching
What is etching?
Wet etching
Wet etching involves the use of chemical solvents (called etchants)
Wet etching
Wet etching
Pure silicon crystals are not isotropic in their properties due to asymmetrical （非对称的） distribution of atoms at their interior. So,when etching material is pure silicon ,the etching is anisotropic(各向异性的) .
Etching(刻蚀) ------A microsystems fabrication process
Speaker:
What is etching?
Etching is an important fabrication
technique in fabricating ICs and MEMS.
Dry etching
Working principle: ● The DRIE process provides thin films of a few micrometer protective coatings of special polymer on the sidewalls during the etching process. ● It involves the use of a high-density plasma source. ● The process allows alternating process of plasma (ion) etching of the substrate material and the deposition of etching- protective material on the sidewalls. ● Special polymers are frequently used for side-wall protective films.
Wet etching
Anisotropic etching is easier to control of the etched shape of the substrates.
Disadvantages: ● Slower in rate of etching (< 1 μm/m) ● The rate is temperature-sensitive. ● Best performance at elevated temperature by using temperature-resistive mask materials.
Etching is used to create 3-dimensional microstructures in substrates by removing materials from desirable locations– The technique is similar to that used by sculptors(雕刻家) in shaping sculptures.
Dry etching
Deep Reactive Ion Etching (DRIE)
Why DRIE?
● Plasma etching can produce deeper trenches, than wet etching, but with tapered angles.
● Tapered trenches are not desirable in many
Wet vs. dry etching
2014.09.23THANK YOUWet etching
Wet etchants methods for silicon and silicon compounds
HNA for isotropic etching at room temperature. Alkaline（碱性） chemicals with ph > 12 for anisotropic etching. Popular anisotropic etchants are: KOH ( potassium hydroxide) EDP (ethylene-diamine and pyrocatecol) (乙(撑)二胺+焦 酚, 连苯三酚, 苯三酚-[1,2,3]) TMAH (tetramethyl ammonium hydroxide)(]四甲基的铵氢氧化物) Hydrazine Typical etching rates for KOH and EDP are:
Wet etching
Dry etching
Dry etching involves the removal of substrate materials by gaseous etchants.
It is more a physical than chemical process.
3 dry etching techniques ● Ion etching.（离子刻蚀）