Full width at half maximum (FWHM) is an expression of the extent of a function, given by the difference between the two extreme values of the independent variable at which the dependent variable is equal to half of its maximum value.
Total Thickness Variation (TTV): The maximum variation in the wafer thickness. Total Thickness Variation is generally determined by measuring the wafer in 5 locations of a cross pattern (not too close to the wafer edge) and calculating the maximum measured difference in thickness.
Bow is the deviation of the center point of the median surface of a free, un-clamped wafer from the median surface to the reference plane. Where the reference plane is defined by three corners of equilateral triangle. This definition is based on now obsolete ASTM F534. There are a number of factors that can affect the shape of a wafer be it Silicon carbide, GaAs or InP. While a wafer is at full thickness, it has the tensile strength to resist any external influences from changing its shape. However, as a wafer is thinned, external influences will cause a wafer to become concave or convex. Some of the more common influences is film type and thickness on the surface of wafer. Concavity, curvature, or deformation of the silicon carbide wafer centerline independent of any thickness variation present.
Warp is the difference between the maximum and the minimum distances of the median surface of a free, un-clamped wafer from the reference plane defined above. This definition follows ASTM F657, and ASTM F1390,which deviation from a plane of a slice or wafer centerline containing both concave and convex regions.
The resistance to current flow and movement of electron and hole carries in the silicon carbide. Resistivity is related to the ratio of voltage across the silicon to the current flowing through the silicon carbide per unit volume of silicon carbide. The units for resistivity are Ohm-cm, and these are the units used to specify the resistivity of silicon carbide wafers and crystals. Resistivity is controlled by adding impurities such as,Nitrogen or Boron to the silicon carbide. As the amount of impurity or dopant is increased, the resistivity is decreased. Heavy doped material has low resistivity.
A dopant, also called a doping agent, is a trace impurity element that is inserted into a substance (in very low concentrations) in order to alter the electrical properties or the opticalproperties of the substance. In the case of crystalline substances, the atoms of the dopant very commonly take the place of elements that were in the crystal lattice of the material. These materials are very commonly either crystals of a semiconductor (silicon, germanium, etc.), for use in solid-state electronics; or else transparent crystals that are used to make lasers of various types. An intentional impurity such as Nitrogen or Boron added to the silicon carbide to engineer or alter the resistivity.which cause n-type dopant and p type dopant. As the dopant increases in concentration per cubic cm the resistivity is reduced.
A semiconductor has electrical conductivity between that of a conductor and an insulator. Semiconductors differ from metals in their characteristic property of decreasing electrical resistivity with increasing temperature.Semiconductors can also display properties of passing current more easily in one direction than the other, and sensitivity to light. Because the conductive properties of a semiconductor can be modified by controlled addition of impurities or by the application of electical fields or light, semiconductors are very useful devices for amplification of signals, switching, and energy conversion. The comprehensive theory of semiconductors relies on the principles of quantum physics to explain the motions of electrons through a lattice of atoms. Current conduction in a semiconductor occurs via free electrons and holes, collectively known as charge carriers. Adding a small amount of impurity atoms greatly increases the number of charge carriers within it. When a doped semiconductor contains excess holes it is called "p-type", and when it contains excess free electrons it is known as "n-type". The semiconductor material used in devices is doped under highly controlled conditions to precisely control the location and concentration of p- and n-type dopants. A single semiconductor crystal can have multiple P and N type regions; the p-n junctions betweeen these regions have many useful electronic properties. Silicon carbide material having electrons as the majority current carriers. Electrons have negative charge (n). Doping with the impurities Nitrogen creates n-type material.
Semi-insulating Doping with the impurities vanadium creates semi-insulating material of silicon carbide.
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