Optical Detection Technology Of Semiconductor Ion Implantation Characteristics

The entire process from wafer to chip contains many steps.Among them,the doping of wafers determines the use and performance of semiconductor devices,which is critical for chip manufacturing.The doping process is also an ion implantation process.The inspection of the wafer after ion implantation can timely analyze the distribution of ion implantation and whether the design requirements are combined,avoiding the waste of subsequent processing costs.The methods of ion implantation testing can be divided into two categories: destructive testing and non-destructive testing.The destructive testing method will cause pollution and damage to the silicon wafer and the testing time will be longer,while the optical non-destructive testing method can achieve rapid and pollutionfree detection of the samples after ion implantation.There are many non-destructive testing methods,and the detection principles used are not the same.In this paper,the modulated light reflection technology is mainly studied to detect the damage of the semiconductor material surface caused by ion implantation and the amorphization caused by defects,resulting in the change of the reflectivity of the sample surface.Then,the influence of different ion implantation dose and implantation energy on the reflectivity of the sample is analyzed in principle,and the sensitivity of the modulated light reflection technique to the ion implantation dose and energy is proved theoretically.In this paper,based on the principle of the modulated optical reflectance,an optical detection system for semiconductor ion implantation is developed and built.The system is divided into two parts: hardware and software.The hardware part includes the optical design of the modulated optical reflectance and the optical module of automatic focusing.The autofocus optical module provides two ideas,one uses the light intensity distribution to determine the focus position,and the other uses the image changes of the two light spots to determine the focus position.The software part includes the motion trajectory planning of wafer scanning,data synchronous acquisition and analysis,image processing method,PID control algorithm,etc.The embedding of the software part makes the complex inspection system intelligent and easy to operate.The modulated optical reflectance signal intensity of the sample under different implant doses,different implant energies,different dopant ions and different modulation frequencies was detected by the system.The experimental results are consistent with the theoretical analysis,which verifies the feasibility of the system.The system can distinguish samples with lower dopant concentration intervals,verifying the sensitivity of the system.By scanning the entire silicon wafer,the intensity distribution of the modulated optical reflectance signal is obtained,and the dose distribution after ion implantation can be seen intuitively,which proves that the system can well detect the dose distribution of the sample after ion implantation.