Metal Assisted Chemical Deep Silicon Etching

Microfabrication is a widely used technology that is crucial to modern science and engineering.Some nanostructures that fabricated by microfabrication have been widely used in the field of photo detectors,gas sensors and solar cells.Etching is a very important technique in microfabrication progress,which can be categorized into dry etching and wet etching.In the traditional etching process of silicon,metal assisted chemical wet etching,compared with traditional dry etching technology,which has shown us many advantages about the high efficiency and cost effective.In this thesis,a main goal is to explore metal assisted wet etching in order to fabricate silicon device.Compared with silicon nanowires and black silicon with nanoscale structures,the main research content of this paper is mainly to silicon micron field.This is a new attempt that in the progress of deep etching,in the field of high aspect ratio and large area of deep etching progress.Prior to the study of the metal assisted wet method to fabricate the silicon micro pillars,silicon waveguides are fabricated using dry etching process.First of all,we design the waveguide by CAD,and a photo mask lithography method is adopted.Then in order to transfer of the pattern into silicon layer on a silicon-on-insulator wafer,contact lithography using photo mask is employed and the pattern formed in AZ5214 photo-resist is transferred into silicon device layer by dry etching using six sulfur fluoride and oxygen in an RIE machine,we achieve accurate pattern transfer of silicon waveguides with highly vertical side wall.Based on the above analysis,the metal assisted wet etching using conventional wet etching,such as polystyrene spheres based on wet etching,anodic alumina template based and wet etching,block copolymer based on template by analogy,we put forward the photoresist mask based on the other ideas.The basic process is that covered with a thin layer of metal layer on the silicon substrate,and then coated with a layer of photo resist on the metal layer,design and transfer pattern on the photoresist,the corrosion of liquid metal will transfer the photoresist pattern on the metal thin layer on the metal layer to realize the mask and the catalyst.After many attempts,the metal layer selected in this experiment is decided to be gold.By changing the thickness of the deposited metal and the morphology of the metal,the reaction can be carried out in the mixed solution of hydrofluoric acid and hydrogen peroxide.The ratio of hydrofluoric acid and hydrogen peroxide in the corrosion solution is optimized to approximately 1:3.Then by adding deionized water to regulate the heat bubbles,the etching reaction can be go on smoothly.Finally we adjust other etching parameters,the measured etching rate by metal assisted wet etching is one micron per minute for silicon.Using this developed method large scaled Silicon micro-pillars are fabrication.They are shown to have good morphology and vertical side walls as required in further investigation.