Laser Annealing in Semiconductors
Investigation of Kinetics of Laser Annealing Process of Semiconductor Materials
Tech Area / Field
- INF-ELE/Microelectronics and Optoelectronics/Information and Communications
- PHY-OPL/Optics and Lasers/Physics
- PHY-SSP/Solid State Physics/Physics
3 Approved without Funding
Tbilisi State University, Georgia, Tbilisi
- Christopher Newport University, USA, VA, Newport News\nUniversita Degli Studi di Roma "La Sapienza"/Dipartamento di Energetica, Italy, Rome\nUniversity of Palermo, Italy, Palermo
Project summaryThe objective of the project is to study dynamics of pulsed laser action on the photon stimulated diffusion in semiconductors As a result, a model of pulse-photon annealing processes, where the role of ionizing and thermal factors will be distinguished, will be created. The results of the research will be further used in developing technological applications to improve electronics material processing.
The non-conventional technological methods based on the laser and pulse-photon radiation treatment have been more and more widely used in technological processes of manufacturing of products of micro- and opto-electronics for recent years. This is caused by necessity to decrease time and temperature of technological processes of manufacturing of the given product, that results in improving their characteristics, raising quality, reliability and the product yield. Limited possibilities of the traditional technology, based on relatively long high-temperature diffusion processes (including an ion implantation tehcnique with consequent high-temperature annealing), do not enable us to solve these problems. Therefore, they can by solved by application of new, perspective and relatively low-temperature methods.
The said methods based on photon stimulated processes, are applied instead of lasting heat treatments in furnaces to carrying out of diffusion processes or annealing of defects. They allow to save from such undesirable factors, as a creation of special media and a long-term high-temperature heating. Said methods have allowed to modify surface layers of a material without a modification of properties of a matrix, to ensure a localization of processes and to forming manifold metastable states. The application of pulse-photon treatment for activation of the introduced impurity and annealing of radiation defects in layers with implanted ions has revealed specific benefits of the given methods.
Despite of a huge amount of investigations in a field of pulse-photon and laser annealing, there is no uniform concept on mechanisms of processes of photon stimulated diffusion, transformation or annealing of defects under photon action. The majority scientists understand this processes, as fast heat (see the book A.V.Dvurechenski, G.A.Kachurin, E.V.Nidaev, L.S.Smirnov. Pulse annealing of semiconductor materials, M., Nauka, 1982, 208p.(Russian)). Therefore, their methods and the constructions of installations, whether the source of photons in them laser or pulse-lamp, provide with short-time, but all the same high-temperature heat of a crystal. Under such approach, alongside with the set forth above positive factors such undesirable factors as creation of defects, dislocations or microcracks are also observed because of a high gradient of temperatures on boundary of cold and locally heated part of a crystal.
However, there is a series of investigations, both ours, and other scientists, where is shown that in particular conditions of pulse-photon treatment, it is possible to carry out diffusion or annealing processes at considerably smaller temperatures than traditional. It allows to avoid an undesirable consequence of pulse high-temperature heating. In such cases, the ionization factor plays the main role in photon stimulated diffusion processes. The lack of single-valued understanding of the mechanism of processes of pulse-photon or laser action makes difficult to beforehand create conditions for a targeted amplification of a role of the ionization factor (i.e. diminution of temperature of a crystal) in technological processes of diffusion or annealing.
This problem with the most high efficiency can be solved through application of the powerful neodymium waveguide laser, radiating a series of giant pulses with the repetition frequency of up to 100 kHz, which was developed under financial support ISTC (Design G-049). The power of giant pulses reaches a several GW, and the laser field is characterized by a high homogeneity. The flexibility of active elements enables to receive any, beforehand given distribution of a laser radiation field in a short-range band.
The high power of radiation allows to receive high harmonics, that is important for accomplishing of investigations on interaction of a laser radiation with different substances during the studying of kinetics of photon stimulated diffusion processes in semiconductor materials.
The investigations accomplished under realization of the project ISTC G-049 have shown, that the laser field could be imagined as the chaotically located exhausts of an electric field created by superposition of many electromagnetic waves. These exhausts of different intensities can lead to nonlinear interactions of a laser field with the defects of crystal lattice. Hence, the radiation field of the powerful waveguide laser will allow to investigate dependence of process of laser annealing under different power of light pulses and to study possible nonlinear processes of interaction of radiation with a semiconductor material.
It is necessary to note, that the radiation of neodymium waveguide laser has a low degree of coherency that because of lack of speckle - structure, ensures a high homogeneity of distribution of intensity of a field. Nevertheless, the multiple element waveguide laser provides with any, beforehand given distribution of intensity of a field that enables to carry out diffusion in semi-conductors selectively - with given figure.
Studying of kinetics of the process of laser annealing in semiconductor materials through a series of giant pulses with the frequency of 30-100 kHz is especially interesting. The high frequency of regular pulses will allow distinguishing the role of the ionization and thermal factors in the laser annealing.
The results of the above-stated investigations will allow developing of a complex of effective methods to decrease temperature of diffusion processes in the technology of manufacturing of semiconductor products of micro- and optoelectronics. The complex of new methods will be based on substitution of a traditional thermal technology by the pulse-photon (laser) action. The investigation of dynamics of the process of laser annealing by means of lasers with the giant pulses permitting to reveal a role of the ionizing factor in this process will be carried out. The methods to significantly lower the treatment temperature of crystals under diffusion and annealing will be suggested.
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