Purpose of the work
Studying the characteristics of semiconductor microminiature energy sources and sensors based on photo- and beta-voltaic effects by means of modeling and CAD (Using beta-particle sources), the use of which opens up breakthrough possibilities in the field of medicine (Cardio- and neurostimulators, hearing aids, devices for overcoming blindness, devices for oncology, biosensors, etc.) And equipment (unmanned aircraft, "black boxes" of the Ministry of Emergency Situations, search devices in inaccessible places, safety, nuclear power, etc.).
The work adopted a multilevel concept of development of methods and tools of simulation and design of electronic component base (ECB) on the principle of bottom-up in the following sequence: radiation - semiconductor material - semiconductor device - chip (or functional unit of IC.
At each of these levels of ECB, the methodology of multifysical modeling is used, which is currently one of the most promising directions of mathematical modeling of complex hierarchical systems used by the world 's leading companies and research companies.
Several types of models are developed or modified for each level of ECB, in particular:
Models of exposure of semiconductor devices to radiation and light flux;
Technology & device models, in which physical effects of different nature are described by 2 and 3 dimensional equations of mathematical physics, which are solved by numerical methods in known 2D/3D modeling systems ANSYS, COMSOL, Synopsys TCAD, Silvaco TCAD, etc.;
To take into account new physical effects that have not previously been taken into account, the above models of different levels use two universal methods:
Introducing into the system equations describing an element (component) of new equations or approximations (expressions) to describe additional effects and model parameters dependent on a particular physical impact.
Macromodeling when the new effect is taken into account by attaching additional elements describing the effect to the equivalent scheme.
Empirical basis of the study
The basis of the study included open publications and results of research carried out by the authors of this Project on available equipment and software.
Results of the work:
1) Concept and specific methods of multifysical modeling of photo- and beta-voltaic energy sources and radiation sensors in the environment of universal 2D/3D computing complexes have been developed.
2) Mathematical models of physical effects in the structures of photo- and beta-voltaic power elements and sensors have been developed. A subsystem is connected to the standard TCAD core, taking into account the interaction of energy flows of photons, alpha- and beta-particles with semiconductor and other materials of converter design.
3) Models of interaction of energy flows of beta-particles with semiconductor materials of converter have been developed.
4) The developed simulation subsystem includes an expanded library of physical models for parameters of the device structure describing the impact of energy flows of particles;
5) the following new models were added to TCAD 's commercial physical model library:
efficient models of the rate of generation of electron-hole pairs in semiconductor materials under the influence of beta-radiation;
TCAD models for investigation of electrical characteristics of semiconductor converter structures when exposed to radiation;
In order to take into account the new physical effects of particle flow, which have not previously been taken into account, the above-mentioned use a universal method: introducing into the system equations describing the element (component) of new equations or approximations (expressions) to describe model parameters dependent on a particular physical impact.
6) Verification of the developed models was carried out on the results of measuring the characteristics of test samples of converters. Verification of the developed models showed a high match of the simulation results according to the proposed model with the data of known sources. This shows that the approach proposed for TCAD modeling of Betavoltaic elements based on Si and SiC can be applied to study the structures of Betavoltaic elements taking into account various external factors.
7) The novelty of the proposed models and techniques for modeling betavoltaic power supply elements is that known and well-tuned TCAD models of optical radiation absorption are used to model the effect of generating electron-hole pairs from beta particle absorption. Such a solution of the problem of setting the generation speed in combination with application of two or three-dimensional models of physical processes in the semiconductor volume allows to investigate the main characteristics of beta-voltaic element taking into account various factors of converter design.
8) The proposed model of beta-voltaic element and modeling techniques will be used in practice to study the dependence of beta-element efficiency on the number and position of radiation sources, the structure of the impurity element profile, which is extremely relevant for practical development.
9) A highly cost-effective TCAD model of a photosensitive CCD cell with a microlens is proposed. The reduction of computational costs in this model compared to the traditional two-dimensional model is achieved by replacing the real cell structure with some simple diode structure, and the efficiency of the microlens is determined by the two-dimensional integrals of the photogeneration rate in specially selected areas corresponding to the areas of photodiodes, vertical registers, anti-blooming runoff, and others with potential pits. This approach does not solve the system of semiconductor equations in dynamics and reduces processor time by up to 10 times (1-2 minutes instead of 10 - 20 minutes for CCD calculation in accumulation mode).
10) Method of determining parameters of microlens of photodetector providing maximum gain is developed. The values obtained by this technique for the photosensitivity gains of a low-dimensional vertical anti-bluming CCD cell (5.5x5.5 μm2) are well consistent with foreign data.
11) For the first time calculation of the value of modulation of the output signal of the line of the matrix FF CCD IS is carried out by means of instrument-technological simulation of distributions of accumulated photogenerated charges with subsequent direct calculation of modulation by the ratio of charge values of adjacent photodetector cells. This approach using TCAD modeling for the first time allows to take into account the influence of any topological, technological and external factors on the resolution of FF IE.
12) Method of TCAD-modeling of CCD cell signal modulation value for FF CCD with vertical antibluming, which allows to carry out maximum modulation by selection of design-process and electric parameters of CCD, has been developed. The technique was tested in the course of practical design of the CCD IS and allowed to create the design of a CCD cell with vertical antibluming with resolution close to the theoretical geometric limit.
13) Using the developed models, modeling and analysis of basic structures of the new generation of microminiature, micro-power semiconductor photo- and beta-voltaic sensors and power elements, were carried out.
By the completeness of taking into account physical effects in the structures of photo- and beta-voltaic cells and sensors, the developed models exceed the available world and domestic level.
For the models developed, there is a good match between the simulated and measured characteristics of the transmitter test samples. Standard error is not more than 15-20%.
The extended capabilities of the TCAD subsystem with the developed and included models of interaction of photon and beta particle streams with semiconductor and other materials of energy element design are illustrated by examples of test samples of a new class of semiconductor microminiature energy sources based on radioisotopes (beta particle sources) with long half-life (tens of years), intended for promising microminiature power sources with long life (tens of years).
Estimates of energy efficiency of photo- and beta-voltaic transformation for various promising designs of power sources and sensors have been obtained.
Degree of implementation, recommendations for implementation or results of implementation of NIR results
The enhanced capabilities of the TCAD subsystem with developed models for converting photon and beta particle streams into transmitter output parameters have been illustrated with examples of promising power supply and sensor designs.
The results of the work may be of interest, first, to enterprises engaged in the application of microminiature energy sources of the new generation based on radioisotopes for the supply of electronic equipment, in particular, JSC "Information satellite technologies named after M.F., Reshetnev," Krasnoyarsk Krai, Zheleznogorsk. Second, the results may be of interest to enterprises engaged in the creation and development of betavoltaic sources, in particular: FSUE Research and Development Institute and enterprise”Luch"(Podolsk), FSUE" Mining and Chemical Plant ", Zheleznogorsk, Krasnoyarsk Krai, FSBU “Institute of Technology for Ultra-Hard and New Carbon Materials”. In addition, they can be useful to specialists of other enterprises, research institutes, universities, academic institutions engaged in the development of equipment used in outer space, medicine, communication and information transmission systems, etc., where access to the power supply network is difficult and micro-power sources of ultra-long service life are required.