Study On Nanofabrication Of Silicon Surface Based On Friction-Induced Selective Etching In TMAH Solution

In the 21 st century,nanotechnology has been widely utilized in military,information,energy,aerospace,medicine and many other fields.Due to the excellent physical,mechanical and electronic properties,monocrystalline silicon is suitable for manufacturing integrated circuits,solar cells and silicon-based semiconductor devices,and it has become an important material to support the development of nanotechnology.At present,micro/nano manufacturing technologies,including photolithography,nanoimprinting,electron beam lithography and local anodic oxidation,have been widely utilized to process the surface of monocrystalline silicon.However,with the diversified development of nanotechnology,it is still necessary to develop other nanofabrication methods.Friction-induced selective etching presents many advantages,such as high resolution,low cost,easy operation,flexible and controllable processing,and has good application prospects.At present,tetramethylammonium hydroxide(TMAH)solution is commonly utilized in industry to etch monocrystalline silicon materials for the purpose of processing.However,there is little study about friction-induced selective etching in TMAH solution.In this paper,the effect of key etching parameters on friction-induced selective etching in TMAH solution was systematically investigated.The mechanism of friction-induced selective etching of single crystal silicon in TMAH solution was analyzed by high-resolution transmission electron microscopy(HRTEM).The specific research contents of this paper are as below.(1)The effect of different parameters on the friction-induced selective etching of monocrystalline silicon was investigatedThe height of the protrusive structures processed by the friction-induced selective etching is mainly affected by etching temperature and etching time.The friction-induced selective etching rate increased with the increasing temperature,and the protrusive hillocks stemming from the selective etching eventually disappeared with the increase of etching time.Different crystal planes also exhibit different friction-induced selective etching characteristics.Si(100)and Si(110)have good selective etching effect,while Si(111)has lower etching rate in TMAH solution.In a certain etching time,the load applied by the tip on the surface of monocrystalline silicon material has no significant effect on the protrusive hillock height produced stemming from friction-induced selective etching,but has a significant effect on the width of the protrusive structure produced by friction-induced selective etching.(2)The etching mechanism of friction-induced selective etching on single crystal silicon surface was elaboratedAfter the diamond tip is scribed on the surface of the single crystal silicon,the surface of monocrystalline silicon will be damaged and the deformed layer will be formed(including oxide layer and lattice distortion layer).The experimental results show that the etching rate of the deformed layer in TMAH solution is much lower than that of monocrystalline silicon in TMAH solution.Therefore,it acts as a mask in friction-induced selective etching.Further investigation showed that the amorphous silicon formed by low-speed etching can also reduce the etching rate and play the role of mask in THAH solution.(3)Nanofabrication was carried out on monocrystalline silicon surface by friction-induced selective etching in TMAH solutionBased on above study,scratching tracks of AFM tip was programmed by C language,and the pattered surface was realized under the closed-loop AFM mode.A series of nanostructures with straight lines,curves and different angles are fabricated on the surface of monocrystalline silicon by friction-induced selective etching in TMAH solution.Generally,the structures have almost the same height as each other and uniform width.In summary,TMAH friction-induced selective etching on the surface of monocrystalline silicon has the advantages of high processing precision,excellent controllability and high surface finish.In this paper,the friction-induced selective etching of single crystal silicon in TMAH solution is utilized to further improve the friction-induced nanofabrication method.The relevant results will help to enrich the basic knowledge of nanofabrication and promote the application of friction-induced selective etching in micro-electromechanical systems and integrated circuit fabrication.