Method and apparatus for measuring sheet resistance and thickness of thin films and substrates
First Claim
1. A method for measuring sheet resistance of a film surface comprising:
- engaging a probe assembly including a plurality of probes with a surface of a film;
creating a variable voltage using a voltage source on said probe assembly to create a variable voltage in said film, thereby creating a variable current through a portion of said film;
measuring said variable current flowing through said portion of said film at a plurality of points in time;
measuring a film voltage between two of said probes of said probe assembly at a corresponding plurality of points in time to when said variable current is measured, said film voltage being influenced by said variable current; and
calculating a sheet resistance of said film from a plurality of ratios of said measured film voltages to corresponding measured currents.
0 Assignments
0 Petitions
Accused Products
Abstract
A method and apparatus for measuring sheet resistance and thickness of thin films and substrates. A four-point probe assembly engages the surface of a film on a substrate, and the thickness of the substrate is determined from the point of contact between the probes and film. A measuring apparatus then outputs a voltage waveform which applies a voltage to probes of the probe assembly. An inverter inverts the voltage and provides the inverted voltage on another probe of the probe assembly, thus inducing a current in these probes of the four point probe and through the surface of the film. Two other probes measure a voltage in the film created by the current. The voltages on the current probes provide a voltage close to zero at the other probes, thus allowing these other probes to measure voltages with greater precision. The current created by the voltage waveform and the voltage created across the inner probes are measured for each voltage level of the waveform. A sheet resistance of the film is determined by calculating the slope of a least square fit line of the measured current and voltage. The sheet resistance is proportional to the slope of the least square line. The thickness of the film is calculated by dividing the film resistivity by the calculated sheet resistance.
-
Citations
36 Claims
-
1. A method for measuring sheet resistance of a film surface comprising:
-
engaging a probe assembly including a plurality of probes with a surface of a film; creating a variable voltage using a voltage source on said probe assembly to create a variable voltage in said film, thereby creating a variable current through a portion of said film; measuring said variable current flowing through said portion of said film at a plurality of points in time; measuring a film voltage between two of said probes of said probe assembly at a corresponding plurality of points in time to when said variable current is measured, said film voltage being influenced by said variable current; and calculating a sheet resistance of said film from a plurality of ratios of said measured film voltages to corresponding measured currents. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
-
-
13. A method for measuring sheet resistance of a film surface comprising:
-
engaging a probe assembly including a plurality of probes with a surface of a film; creating a variable voltage on a first one of said probes of said probe assembly using a voltage source; creating a dependent variable voltage on a second one of said probes of said probe assembly by inverting said variable voltage and providing said inverted variable voltage at said second probe, thereby creating a variable current through said film, wherein said current in said film flows from said first probe to said second probe; measuring said variable current flowing through said portion of said film at a plurality of points in time, said variable current being measured at a portion of said film between said first and second probes where an average voltage is close to zero; measuring a film voltage between two of said probes of said probe assembly at a corresponding plurality of points in time to when said variable current is measured; and calculating a sheet resistance of said film from a plurality of ratios of said measured film voltages to corresponding measured currents. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 33, 34, 35, 36)
-
-
21. A method for measuring sheet resistance of a sample comprising:
-
(a) engaging a probe assembly including a plurality of probes with a surface of a sample; (b) applying a first voltage from a voltage source to a first probe of said probe assembly; (c) providing an inverted voltage based on and inverted from said first voltage to a second probe of said probe assembly, thereby creating a current through said sample; (d) measuring said current through said sample; (e) measuring a sample voltage between said first probe and said second probe; (f) repeating steps (b) through (e) applying a second voltage in place of and different from said first voltage; and (g) calculating sheet resistance using a plurality of said measured currents and a plurality of said sample voltages. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
-
Specification