Jozef Ociepa, PhD, Research VP for Stela Materials (SMI)) spoke on novel processes for semiconductor manufacturing at The U.S. Workshop on the Physics and Chemistry of II-VI Detector Materials.
The purpose of this Workshop is to bring together the industrial, governmental, and academic communities that work with II-VI materials. These II-VI materials are critical in a wide range of detector technologies operating in the infrared, ultraviolet, x-ray, and gamma-ray regions of the spectrum, as well as broad-band devices such as solar cells. They include HgCdTe, ZnSe, ZnO, ZnS, and CdTe, as well as other II-VI semiconductors and alloys. Spectrometers, imagers, and other sophisticated systems exploiting various properties of these materials are finding applications in many fields, including national security, homeland security, medicine, industrial process monitoring, basic science, astronomy, energy production, and more.
Abstract presented:
Effect of photonic annealing on reduction of surface defects on Si(111) and Si(112) measured by changes in the effective surface Debye temperature using LEED
Surface defects in semiconductors plays very important role in high quality device fabrication and their performance because strong influence on their electrical and optical properties. In this paper we show result of the effect of the photonic annealing using 300 Watt Xe Arc lamp irradiation on the wafer samples of Si(111) and Si(112). The method of characterization employed was Low energy electron diffraction (LEED) and changes of effective surface Debye temperature.
The use of monitoring changes in surface Debye temperature to detect changes in the surface defect concentration is not well established technique but offer several advantages such simplicity and high precision. There is limited literature data which connecting lattice vibrations with defects parameters. The limited nature of the literature resources in this field provides strong motivate experimental investigations. The thermal vibration of the atoms at the surface depends on binding energy, structure and also defects concentration. Most typical surface defects are vacancies, steps, dislocations, boundaries, etc. and they are intrinsic or introduced during surface preparation processes. The defects are influencing the atomic binding energy in the crystal structure which affects the thermal vibration characteristic of the surface. The thermal vibrations characteristic can be characterized by measurements of the surface Debye temperature using LEED. In this method the diffracted beam intensity is measured as a function of the surface temperature. From this plot the surface Debye temperature is calculated. Increasing the primary electron beam energy increases the electron beam penetration to the surface. The diffracted beam close to the normal to the surface give information on thermal vibrations in normal direction. The mean free path for the low energy electrons is in the order of 0.5 nanometers for 100 eV beam energy which ensure the results from the topmost surface layer.
Photonic annealing is applied to reduce surface defects caused by low energy ion bombardment below energy 0.5keV. Photonic annealing of clean Si(111) and Si(112) substrates show LEED pattern changes in the reconstruction of the clean silicon surfaces. It has been demonstrated that photonic annealing is another tool for improving the growth of quality of epitaxial thin films on silicon wafers. The highest temperatures during photonic annealing is at the first surface layer, limiting the restructuring of deeper layers. The variation of the surface Debye temperature using LEED is related to the changes in surface defect densities.
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