In recent years, CMOS image sensor has been widely used for ubiquitous devices such as smart-phone and tablets. However, CMOS image sensors performance are dramatically influenced by process induced defects such as metallic impurities related deep level defects in the space-charge region. Thus, it is extremely important to study metallic impurities influence on CMOS image sensor performance and to develop effectiveness metallic impurities gettering technique. In this article, we introduce our new proximity gettering technique for advanced CMOS image sensor by using a carbon cluster ion implantation technique. In addition, we demonstrate that the carbon cluster ion implanted silicon wafer has high gettering capability of oxygen, hydrogen and metallic impurity after CMOS simulation heat treatment.
Metal impurities dissolved in silicon can cause “recombination centers”, which degrade retention characteristics of DRAMs, produce dark current in CMOS image sensors, and cause leakage of current in high-voltage transistors. In consideration of these problems, methods of controlling metallic contamination (including the removal, prevention, and gettering) in advanced ULSI manufacturing are reviewed. In particular, for controlling yield of the devices, the better understanding of the behavior and electrical activities of metal impurities diffusing in and penetrating into silicon is important. The gettering design based on the physical properties of metal species is also proposed.
The mechanisms behind the experimentally observed impact of the type and concentration of substitutional dopants on intrinsic point defect behavior in growing single crystal Si are clarified. On the basis of the density functional theory (DFT) calculated results, an appropriate model of intrinsic point defect behavior in heavily doped Si is proposed. Also one has to take into account the impact of thermal stress on intrinsic point defect behavior during single crystal Si growth. In order to explain the experimental results quantitatively, the dependence of the formation enthalpies of vacancy (V) and self-interstitial (I) on compressive plane stress was determined using DFT calculations. It is found that the compressive plane stress around 20 MPa shifts a growing Si crystal to more V-rich. The calculated plane stress dependence is in excellent agreement with the published experimental values and should be taken into account in the development of pulling processes for 450 mm diameter defect-free Si crystals.
Cathodoluminescence (CL) is a kind of light emission as a result of electron beam irradiation to various materials. In the measurement technique using CL, scanning electron microscope (SEM) is usually used as an electron beam source, and consequently CL measurement method is suitable for the characterization of electronic devices. However, the application to electronic devices made of silicon (Si) is restricted because of the low luminescence efficiency of Si. In this paper, we show the application of CL spectroscopy to the characterization of Si electronic devices and discuss the results of it. In particular, we focus the point defects and dislocations generated during device fabrication process.
The influence of diffusion temperature on the formation of one type of Cu center denoted as CuDLB center, the relationship between the concentrations of the CuDLB center after the diffusion of Cu and those of contaminated Cu on sample surfaces, and the transformation of the CuDLB center to another type of Cu center denoted as the CuDLA center by annealing were investigated by photoluminescence and deep-level transient spectroscopy (DLTS) measurements. It was found that the CuDLB center is composed of one core Cu atom and weakly bonded three interstitial Cu atoms around the core and that the CuDLA center is the core of the CuDLB center. For Ni, the depth profiles of the substitutional Ni (Ni center) in silicon diffused with various concentrations of the element were measured by DLTS, and were found to be controlled by the temperature-dependent outdiffusion of Ni.