This paper describes a simulation technology for HgCdTe infrared detectors used in advanced IR focal plane array architectures. This model addresses the material processes needed for fabrication and the electrical characteristics of multi-layer structures covering a wide range of wavelengths from middle wavelength to very long wavelength.
Focal plane arrays (FPAs) are used in many applications for detecting infrared (IR) radiation where normal sight with light in the visible spectrum is not possible. To effectively detect this IR radiation, complex semiconductor diodes, cooled to low temperatures, are usually used. The most common of these semiconductor materials is the II-VI alloy semiconductor system using HgCdTe, which is often called MCT. Focal plane arrays with over 1000 pixels have been fabricated. The cost of these very complex systems is becoming a very important consideration in decisions of where to use these FPAs. The focal plane array actually consists of two semiconductor parts with a sophisticated cooling assembly. The semiconductor parts are the MCT detector device itself and a companion device called the read-out circuit. The cost model presented in this paper consists of various expressions as functions of physical parameters that can be measured, calculated from data or estimated. Although accurate absolute cost data may not be available (because it does not exist or is proprietary to a company), cost estimates can be effectively used to determine relative cost between two designs or processes. In addition, when these cost models are coupled with the STADIUM design of experiments simulation methodology, accurate predictions of the most dominant cost drivers can be obtained. This cost model and its algorithms are coupled with a commercial software program called IR-SIM.
Mercury Cadmium Telluride focal plane arrays with well over 1000 pixels have been fabricated for a number of years. These FPA's have been built as large two-dimensional arrays of HgCdTe p-n junction diodes on a single CdTe or CdZnTe substrate. Sensitivity of each pixel to impinging radiation is one of the most important quality factors for these devices. However, material parameters, which give diode high sensitivity, are the same as those that cause cross talk between adjacent diodes in the array. This cross talk causes a blurred image and in general is a detrimental factor for the FPA system. The cross talk modeling is done in a two- dimensional simulation format to achieve high accuracy. In addition, the output information can be generated as a statistical function of the material and design parameter variations. Actual heterojunction FPA devices have been fabricated and tested for cross talk. In the paper, this data is compared to the simulation results. This design method and its algorithms are encapsulated in a software program called IRSIM. This physics-based simulator allows the engineer to use versatile geometries and material concentrations.
Heterojunction HgCdTe detector chips are used in military and commercial focal plane array systems. These devices give improved performance because they are built with a wide bandgap semiconductor on top of a narrow bandgap semiconductor. Optimization FPA performance with heterojunction detectors has posed problems because many of the HgCdTe material parameters vary as a function of composition, temperature and doping concentrations. AET, with funding from the US Army Night Vision Labs, has developed a new simulator called IRSIM that automates the HgCdTe device analysis and design. This paper discusses the details of and operation of this simulator.
HgCdTe has emerged as an important electronic material because of its IRFPA applications. Technologies for growing the material are advanced and current sources for the material are more readily available than in the past. This brings an advantage to the manufacturing other types of HgCdTe devices. PHEMTs are attractive as applications of high-speed devices. In this paper, a model for PHEMT devices by using Hg1-xCdxTe as device materials is presented. High digital performance of the device is expected because electron mobility of the material is very high at low temperatures.
In our work, a three-dimensional IRFPA model has been constructed to conduct device simulations for drift-diffusion based Hg1-xCdxTe devices. The model uses the finite element method and numerical errors are automatically eliminated during computation. Computational results can thus easily achieve accuracy. The computer model was constructed by using C++ language. We have successfully represented simulation results in three-dimensional graphics. In this paper, a model for analyzing infrared-illuminated p-on-n photodiodes is presented. The computational results were verified analytically and experimentally. Furthermore, an IRFPA device model was built for calculating crosstalk by using uniformly collimated infrared radiation. Devices used for the model were linear FPAs. Ohmic contacts with zero bias were applied on electrodes. Other physics phenomena such as recombinations were also considered in the analyses. This model and simulation approach can provide an efficient way to reduce crosstalk in designing advanced MCT IRFPA devices.
Researchers have studied the use of double layer heterojunction HgCdTe devices for application in focal plane arrays (FPA's). Such devices are built with a wide bandgap semiconductor on top of a narrow bandgap semiconductor. With a highly doped p-type material at the surface, these devices enhance the ability to make contact with the anode side of the diode with interconnect metal. Optimizing FPA performance with heterojunction detectors has posed serious problems because many of the HgCdTe's material parameters vary as a function of composition, temperature and doping concentration. AET, with funding from the US Army Night Vision Labs, has developed a new system for design of focal plane arrays using heterojunction HgCdTe detectors. By using this new software modeling technique, a double layer heterojunction detector device has been designed with consideration for many of the material and environmental variations. This paper develops the models employed in the simulation program and will compare the simulation results with experimental data.
FLIR92 and ACQUIRE have become the standard simulation models used in virtually all Forward Looking Infrared (FLIR) system design. Recently, a software program called STADIUM FLIR has been written for use with the U.S. Army's FLIR92 and ACQUIRE models. This software provides many performance and ease of use enhancements for the models. Some of these enhancements include graphical user interfaces for all model parameter entry, data extraction between FLIR92 and ACQUIRE as well as comprehensive plotting of output curves. All data extraction and plotting is automatic and seamless. STADIUM FLIR is based on AET's STADIUM technology which adds powerful Design of Experiments and statistical analysis capabilities to simulation environments. The results are presented both quantitatively and graphically. STADIUM FLIR provides comprehensive plotting capabilities for both raw data as well as `overlayed' statistical variability data. STADIUM FLIR provides the power to perform multiple FLIR92 and ACQUIRE simulations with inputs (even multiple targets) varying over user specified ranges. This paper will describe the software and how it enhances the power of FLIR92 and ACQUIRE.
Existing infrared IRFPA models lack simplicity for setting up the detector's architecture/structure and lack continuity between IR detector material, IR detector processes, detector architecture, and detector operation. Existing models also lack the ability to reveal spatially and quantitatively the full impact of the detector's material, process and architecture on IRFPA performance. This paper discusses the development of a new IRFPA computer model used to simulate existing and future IRFPA's. This model is the first model that evaluates the IR sensor system at the device physics level and provides enhanced quantitative and visual information allowing the device engineer to determine the impact of material quality, processing procedures and IR detector architecture on IRFPA performance in the SWIR-VLWIR region. This new model is combined with powerful statistical techniques that predict IRFPA performance as well as cost. Operation under virtually unlimited user specified conditions allows the engineer to project the performance of a newly designed IRFPA prior to fabrication. The complete model provides outputs at both the device physics and detector level. When interfaced with NVESD's FLIR92 and ACQUIRE, the model provides the ability to analyze effects at the device level of the detector that impact outputs at the system level such as NETD and range.
This paper addresses the integrated circuit industry needs for non-isothermal simulation in device reliability analysis, initial
input factor sensitivity analysis and their software implementation. The key reliability issues are the hot-electron induced
oxide damages and electro-static discharge (ESD) damages. The main purpose of this work is to provide a design aid tool to
improve device reliability and performance. The reliability simulator developed in this work not only predicts designed device
reliability, but also provides some information about the effect of manufacturing variations on reliability. This is accomplished
by combining the statistical methodology with existing technology computer aided design (TCAD) tools. The design of experiment
(DoE) technique can be successfully employed to analyze the effect of manufacturing variations on the SOT device reliability.
As an example, the reliability analysis and the statistical analysis have performed on SOT MOS devices (partially
depleted and fully depleted SOT) and submicron bulk-Si MOSFET's to verify the applied modeling method.
Existing Infrared IRFPA models lack simplicity for setting up the detector's architecture/structure and lack continuity between IR detector material, IR detector processes, detector architecture, and detector operation. The models also lack the ability to reveal spatially and quantitatively the full impact of the detector's material, process and architecture on IRFPA performance. This paper will discuss the development of a new IRFPA computer model which is used to simulate existing and future IRFPA's with enhanced quantitative and visual information that allow the device engineer to access the impact of material quality, processing procedures and IR detector architecture on IRFPA performance in the SWIR-VLWIR region. This new model will be combined with statistical simulation to provide high IRFPA performance and lowest cost.