SEMICONDUCTOR DEVICE PHYSICS AND DESIGN

218 CHAPTER 5. SEMICONDUCTOR JUNCTIONS

R =

C ross-sectional area, A

Lρ

A

R esistivity = ρ

L

W

D

L

S heet resi stance

= R W R =R LW

(b)

METALS IN SEMICONDUCTOR TECHNOLOGY

I nterconnects to prov i de

low resistance paths for

current

S chottk y barri ers to

prov i de non- l i near

I -V response

O hmi c contacts to prov i de

low resistance paths to inject

el ectrons and hol es i nto

semi conductors

(a)

(c)

Figure 5.1: (a) Metals serve three important functions in semiconductor technology. (b) A resis-
torofdimensionsL×W×D. (c) Representation of the resistors in terms of sheet resistance.

wherenis the free carrier density andμis the mobility of the carriers (the equation can be

modified for ap-type material).

The sheet resistance is a measure of the characteristics of a uniform sheet of film. It is

defined as ohms per square, as shown in figure 5.1c, and is related to the film resistance by

R=R

W

L

(5.2.3)