Depth-profile Reconstruction Of Electronic Properties In Ion-implanted Semiconductor Using Photocarrier Radiometry

In the doping process of the semiconductor industry, ion implantation method overcomesthe drawbacks of thermal diffusion method and is widely used in large scale integrationcircuit manufacturing due to its following advantages: high uniformity in the implantationdose, low operation tempreture, good repeatability. It is necessary to monitor the relationbetween the electronic properties (carrier lifetime and diffusivity coefficient) and theimplantation processing parameters including the implantation dose,implantation energyand the implanted ion range to control and improve the quality of the ion-implantedsemiconductor. The conventional method of measuring the electronic properties mainlycontain the open circuit voltage decay (OCVD) and the secondary ion mass spectrometry(SIMS). But these methods are limited due to the long period, contact with the sample andnon-real time in the measuring process. Recently, a photocarrier radiometry (PCR) wasintroduced and found to be an non-destrucive, quick-measuring and high-sensitive method.The effective electronic properties in the ion-implanted semiconductor are measuredthrough effective uniform-layer theory model established based on the structurecharacteristics of the ion-implanted semiconductor using the PCR method. But theinhomogeneous variable electronic properties along the depth in the ion-implantedsemiconductor can not be investigated based on the former theory model. In this article, adepth profiling technique using photocarrier radiometry (PCR) is demonstrated and usedfor the reconstruction of continuously varying electronic transport properties alone thedepth in the ion-implanted semiconductor. The article proposes a multi-layer theoreticalmodel suitable for the ion-implanted semiconductor possessing the inhomogeneousvariable electronic properties using the photocarrier riometry (PCR) method. The inhomogeneous region in the ion-implanted semiconductor is sliced into many virtual thinlayers along the depth direction so that the continuously and monotonically variableelectronic properties across its thickness can be considered uniform within each virtuallayer. A recursion relationship among the slices is obtained and the overall PCR signal isexpressed as a summation of contributions from each slice. The application condition ofthe theory model and the effect from the parameters of the ion-implanted semiconductorare investigated through numerical simulation. In the experiment, the final PCR signals ofsemiconductor wafers which are ion-implanted at different doses with differentimplantation energies are measured. Then the established multi-layer model ismultiparameter fitted to the experimental data. At last, the depth profile reconstruction ofboth carrier life time and diffusivity in these experimental implanted wafers is presented.