Francais | English | Espanõl

From Wikipedia, the free encyclopedia

Image:Carbon-film Resistor Construction.svg

The sheet resistance is a measure of resistivity of thin films that have a uniform thickness, for example, doped semiconductor regions (e.g. silicon or polysilicon). It is commonly used to evaluate the outcome of semiconductor doping or metal deposition steps. Sheet resistance is measured in ohms/square <math>(\Omega/\square)</math>, and it is equivalent to resistivity for two-dimensional systems. When this term is used, the current is passing along the sheet, not through it.

In a regular three-dimensional conductor, the resistance can be written as

<math>R=\rho\frac{L}{A} = \rho\frac{L}{W t}</math>

where <math>\rho</math> is the resistivity, <math>A</math> is the cross-sectional area and <math>L</math> is the length. The cross-sectional area can be split into the width <math>W</math> and the sheet thickness <math>t</math>.

By grouping the resistivity with the thickness, the resistance can then be written as

<math>R = \frac{\rho}{t} \frac{L}{W} = R_s \frac{L}{W}</math>

<math>R_s</math> is then the sheet resistance. Because it is multiplied by a dimensionless quantity, the units are ohms. The term ohms/square is used because it gives the resistance in ohms of current passing from one side of a square region to the opposite side, regardless of the size of the square.de:Schichtwiderstand