Study Of Laser Assisted Wet Chemical Etching

The unique superiority of laser such as monochromaticity, directivity and high brightness are used in Laser assisted wet chemical etching (LAWE). Taken the laser to the material photon effect and the thermal reaction as the foundation, this technology can assist in the material aqueous etching process,thus satisfies the need of material etching. There are the following advantages with LAWE technology. First, compared with general chemical etching, the influence of crystal orientation can be eliminated effectively and the diverser etched figure is manufactured by LAWE. Secondly, it's much easier to realize the process conditions and simpler to operate than Laser introduced gaseous etching. Furthermore, compared with Dry ion etching, there is no ion damage to the substrate, the excessive etching is easier to control and the cost is low. So LAWE technology has become one of the world study focuses gradually. Because of many factors that influence the effect of the semiconductor Laser Aqueous Etching, it's very difficult to obtain the ideal etched figure and monitor the etching process.So far these problems have not been solved.This dissertation focuses on the Laser induced aqueous etching technology. The main research results and important contributions are as follows:1)Mainly based on the LAWE technology, to realize its application, the principle, the process real-time monitoring,processing and device application are researched. The LAWE study system is established effectively.Based on laser technology, LAWE is a typical interdisciplinary. Its content ranges from chemistry to material and many other fields. With the complex background, many problems related to the practical application(involving principle,processing level and process monitoring) press for solution. Because every aspect mentioned above correlates.The establishment of LAWE system is an important starting point in the dissertation. The extensive and in-depth research covering a wide range and requiring strong innovative capacity is conducted.2) The infrared thermal imaging method is used in real-time monitoring. The thermal environment distribution of the etching solvent in the LAWE process is studied systematically. So the important factor temperature which affects LAWE is characterized.The temperature is an important consideration in the chemical reaction. In the LAWE process, laser, chemical reaction heat and other factors all have a great influence on practical temperature. Additionally, thermal convection, heat conduction and thermal radiation are also taken into account. Using infrared thermal imaging for the real-time monitoring is proposed by the article. Thermal radiation caused by the temperature difference is converted into infrared visible image. With recording and processing, required monitoring results are obtained. The interrelationships between the process, rate and the surface roughness of etching process and infrared thermal image are explored.3)The measuring method to obtain the material reaction starting time length(it takes a certain period time to react between the material and etching solution from contact to etching)is put forward. Focused on different materials and etching solution concentrations, the chemical reaction starting time lengths are researched and valuable experiment results are obtained.Constantly increasing the etching rate is generally considered as the foundation for the sustainable development of the wet-etching technology. Because compared with dry-etching technology, the defects including lateral etching can be overcome only by continuous acceleration of etching rate. Thus the advantages of wet etching:wide application scope, low cost and excellent selective etching property stand out. With the continuous improvment of etching rate, the high control accuracy of time is required. The chemical reaction starting time length has great impact on controlling the fast etching time. So far the effective technology to measure the reaction starting time length is lacked. A rough estimate or complete neglect are in most cases. So the further development of fast etching is slowed down. From the phenomenon that the heat generation in the chemical reaction, this thesis has made thorough research to the etching droplet on the surface of the material and infrared radiation character of the etching liquid membrane. The infrared thermal real-time monitoring system is used to collect the infrared grey image real-timely of the linearis liquid membrane caused by the sliding droplets on the vertical material surface. The information about the reaction starting time length is acquired successfully. 4) As one of the critical steps, study on processing technology determines the practical application results of LAWE.The laser-assisted aqueous etching processing system is proposed in this thesis including etch-resistant film masking method, oder-selective etching method, electrode etching method and two-step etching method. According to the selection of methods, the etching on the different materials are realized successfully. Ideal etching results are obtained.Etch-resistant film masking method:cover the substrate surface on which etching is not required with etch-resistant film. And laser irradiates to etch the region without the film.Electrode etching method:etching electric current is formed in the solution by applying electric voltage and causes the intermediate ion product to separate from the substrate surface. Oder-selective etching method focused on the using order of the mixed solvents. Two-step etching method takes advantages of the etching rate differences in the different direction of the materials to prolong or shorten the etching span.In the practical etching processing, one or more processing methods can be adopted for different demands. Various processing methods are analysed separately by this thesis. According to the theoretical analysis and experimental verification, the above four methods building the basic processing system can meet most etching need and gain ideal etching results.5) LAWE has the vital significance for the application of the device fabrication and its property's research. Based on LAWE technology as the processing foundation, an omnidirectional self-aligned circular detector is designed and an optically controlled high-temperature superconducting attenuator(it can realize the accurate signal attenuation) is fabricated.As far as I know, It is first reported both in domestic and abroad such as measuring method to obtain the material reaction starting time length, the surface roughness of etching process, self-aligned circular detector, laser-assisted aqueous etching processing system, optically controlled high-temperature superconducting attenuator and thermal environment distribution monitoring of the etching solvent in the LAWE process...