Photolithography And Mechanical Properties Of SU-8 Photoresist Modified By Sic Nanowires

With the development of MEMS technology,in addition to silicon-based materials,a variety of new materials have been developed for the design and manufacture of MEMS devices.Among many new MEMS materials,polymers are favored for their excellent properties.Among them,polymer matrix composite materials can combine the advantages of polymer matrix and reinforcement at the same time,which can better meet the application requirements of polymer MEMS and have more development potential.As a kind of polymer material with many excellent properties,SU-8photoresist has been widely used in MEMS system because of its direct photolithography ability and excellent structural material properties after curing.At the same time,the development and utilization of all kinds of polymer matrix composites based on SU-8 compound modification have been paid more attention.However,up to now,most of these researches have focused on composite with functional materials to give SU-8 adhesive some unique functions,but little attention has been paid to how to modify the mechanical properties of SU-8 adhesive to achieve better microstructure materials,although it is mainly introduced into MEMS architecture as a microstructure material.In view of this,this paper proposes a general method of SU-8 compound modification to improve its mechanical properties,in order to further improve its applicability as a micro structural material in MEMS,and try not to have a serious impact on its direct photolithography.Therefore,on the basis of considering the compatibility of micromachining process and the ability of photolithography,Si C nanowires are selected as reinforcement materials in this paper.The process methods of composite modification and micromachining of Si C nanowires with SU-8 adhesive,as well as the effect and mechanism of strengthening and toughening of the modified composites are systematically studied.The main research contents and achievements are as follows:1.The process of uniform mixing of Si C nanowires and SU-8 glue was studied.By means of dispersing medium and temperature rising agitation,the nanowires can be uniformly dispersed in SU-8 photoresist.2.The technology of fabricating thick film microstructure by direct photolithography of Si C nanowires and SU-8 composite precursor was established.The gelatinization,soft-bake,exposure,post-bake,development and post-processing technologies were studied in detail.In this experiment,firstly,the structure was fabricated by lithography,and the lithography process was optimized to realize the lithography graphics of silicon carbide nanowire / SU-8 composite with a certain thickness.In order to solve the problem of rough edge of graphic structure,the reactive ion etching(RIE)method is innovatively used to remove the redundant Si C nanowires on the side wall by optimizing the technological process.3.The key properties of SU-8/Si C nanowire composite were characterized,and the mechanism of strengthening and toughening of Si C nanowire composite SU-8 adhesive was discussed.Based on the optimized photolithography process and reactive ion etching process,the samples were prepared.Based on the analysis of the mechanical properties of SU-8 matrix composites with different silicon carbide nanowire content,and combined with the scanning electron microscope observation of the cross-section morphology of the tensile specimen,the remarkable strengthening and toughening effect of silicon carbide nanowire on the mechanical properties of SU-8 was verified.The effect of the Coupling Agent Modified Si C nanowires on the mechanical properties of the composite was verified by static tensile method.The transmittance test shows that silicon carbide reduces the transmittance of SU-8 matrix,especially in the near UV region,but it can still form a certain thickness of structure by photolithography.The test results of thermal conductivity and thermal expansion coefficient show that Si C can improve the thermal properties of SU-8 matrix significantly.Through this study,the process feasibility of strengthening SU-8adhesive microstructure by Si C nanowire composite was confirmed.Moreover,Si C nanowire composite can not only improve its mechanical strength,thermal conductivity,reduce the coefficient of thermal expansion,but also maintain its advantages of direct photolithography,which is conducive to the SU-8 adhesive as a micro structure material to get more applications in MEMS devices.