Thin films used in semiconductor manufacturing all have resistance, and film resistance has a direct impact on the performance of the device. We usually do not measure the absolute resistance of the film, but use the sheet resistance to characterize it.
What are sheet resistance and volume resistivity?
Volume resistivity, also known as volume resistivity, is an inherent property of a material that characterizes how much the material impedes the flow of electrical current. Commonly used symbol ρ represents, the unit is Ω.
Sheet resistance, also known as sheet resistance, the English name is sheet resistance, which refers to the resistance value of the film per unit area. Commonly used symbols Rs or ρs to express, the unit is Ω/sq or Ω/□
The relationship between the two is: sheet resistance = volume resistivity/film thickness, that is, Rs =ρ/t
Why measure sheet resistance?
Measuring the absolute resistance of a film requires precise knowledge of the film’s geometric dimensions (length, width, thickness), which has many variables and is very complex for very thin or irregularly shaped films. The sheet resistance is only related to the thickness of the film and can be quickly and directly tested without complicated size calculations.
Which films need to measure sheet resistance?
Generally, conductive films and semiconductor films need to be measured for square resistance, while insulating films do not need to be measured.
In semiconductor doping, the sheet resistance of silicon is also measured.
How to measure square resistance?
The four-probe method is generally used in the industry. The four-probe method can measure square resistance ranging from 1E-3 to 1E+9Ω/sq. The four-probe method can avoid measurement errors due to contact resistance between the probe and the sample.
Measurement methods:
1) Set four linearly arranged probes on the surface of the sample.
2) Apply a constant current between the two outer probes.
3) Determine the resistance by measuring the potential difference between the two internal probes
R S : sheet resistance
ΔV: Change in voltage measured between internal probes
I : Current applied between outer probes
Post time: Mar-29-2024