Research On The Preparation Technology Of Ultra-thin Silicon Wafers And Their Photoelectric Properties

The silicon is the most important material in many semiconductor components such asphoto detectors,semiconductor lasers,photovoltaic cells,etc.Therefore,it is widely used in the imaging field,information communication and new energy fields.With the development of application requirements such as device miniaturization,low cost and high performance,the demand for the preparation process of ultra-thin silicon wafers is increasing.However,during the processing of ultra-thin silicon wafers,the silicon wafers will be sensitive to mechanical stress and vibration as the thickness decreases,and the structural stability will be greatly reduced.Due to the influence of its own gravity,surface application and strong pressure on the silicon wafer,the silicon wafer may be bent or even broken,causing the silicon wafer to break,crack and roughen the surface.And the existing thinning process is gradually unable to meet the requirements and development of device preparation.It has become a key issue that realize the preparation and processing of ultra-thin silicon wafers in the field of semiconductor research.In this thesis,it is studied in depth that preparation of ultra-thin silicon wafers,and the photoelectric properties of ultra-thin silicon wafers.First,the preparation process of ultra-thin silicon wafers is studied in the thesis.Themethod of combining adhesive bonding process and chemical mechanical grinding and polishing process is used.It is optimized in terms of thinning process,pressure,speed,etc.And the influence of pressure and thinning process on the surface accuracy of silicon wafers is analyzed.The results show that the use of adhesives with better viscosity and higher hardness can improve the mechanical properties of silicon wafers that can withstand processing and ensure the total thickness deviation of ultra-thin silicon wafers after thinning.In the polishing stage,a combination of mechanical action and chemical action is used,and at the same time,the pressure on the sample is appropriately increased,which can improve the thinning efficiency and reduce the surface roughness of the ultra-thin silicon wafer.Finally,an ultra-thin silicon wafer with a thickness of about 10um and a high surface flatness is prepared.Secondly,the optical properties of silicon wafers with different thicknesses in differentdevices are studies.The optical characteristics of ultra-thin silicon-based solar cells are simulated.By introducing ITO anti-reflection layer and silver cathode,the light absorption characteristics of 10-50?m ultra-thin silicon wafers are better in the sunlight waveband.However,the preparation of ultra-thin silicon wafers can realize the preparation of silicon wafers in this thickness range,especially the preparation of 10-30?m thin films.It is of great significance to reduce the cost of photovoltaic devices.The optical characteristics of the electron multiplying layer in the back-illuminated CMOS are simulated.The results show that the light absorption characteristics of 10?m thick silicon wafers in the visible light band are more consistent with those of thicker silicon wafers,but the light absorption performance in the near-infrared band is poor.And the application of ultra-thin silicon wafers to back-illuminated chips has a good imaging effect in the visible light band.At the same time,the influence of the introduction of single-layer Si O₂ and double-layer Si O₂/Si₃N₄ on the optical properties of silicon film(electron multiplying layer)was simulated and analyzed.It is showed that covering a 200 nm Si O₂ film on the surface of a 10-100?m silicon wafer can increase the light absorption rate of the device by 15%.If the150 nm Si₃N₄ film is further introduced,the light absorption can be further enhanced by14%.Finally,the electrical properties of ultra-thin silicon wafers are studied.The main content of the research is the electron gain characteristics when used as an electron multiplying layer in an electron bombardment imaging device.The results show that as the incident energy increases,the gain of the electron multiplier layer also increases.The experimental results are consistent with the trend of the simulation results.So,the ultra-thin silicon wafer has better electronic gain characteristics.In summary,the ultra-thin silicon wafers can be applied to photovoltaic devices,back-illuminated CMOS,electron bombardment CMOS and other optoelectronic devices,and the preparation process has important theoretical value and guiding significance for device preparation.