Metrology and Inspection

Define Metrology, characterization and Insespection

Metrology: precision, statistics and prepeatable measurements to ensure process control and quality assurance

Characterization: full analysis of materials: properties and behavior

Inspection: actively searching for defects

Ellipsometry

A non-destructive polarized beam used to find film thickness and angle of diffration. A non-destructive and quick method

Atomic Force Microscopy

Uses a canteliver with a tip to map a 3D surface. Non-destructive and has high resolution. Slower so best for smaller sample sizes

Optical Profilometry

splits light in two, interference shows height change/topography. Non-destructive contactless and very fast

Contact Profilometry

stylus drags across the surface to find topography. non-destructive but can cause some surface contamination

Good for a spot check

Scatterometry

3D optical profilometry, makes a 3D surface map. Is non-destructive, contactless and has high precision

SEM

low energy beam that measures dimensions and features. Is contactless, high precision but slower and causes some damage

What are color charts used for?

easy way to find film thickness by shining light on sample but not very precise

Are systematic or random defects harder to detect? Why?

Systematic as they are regular you may not realize it is a defect

Automated Optical Inspection

type of defect inspection using a light or e-beam source to find defects by comparing adjacent dies

Laser-Based Inspection

non-patterned wafers have laser light scattered when encountering a defect. The position is recorded

Electron Beam Inspection

Looks at nano scale patterns. Uses dark-field ot analyze SE and BE electrons. Shows conductivity contrast

ρ = resistivity

n = carrier concentration

q = charge

L = length of wire

A = cross-sectional are

S = probe spacing

V = voltage

I = current

μ = mobility

t = thickness of film

Rs = resistance of square, uniform sheet

What is the four point probe method?

uses four probes to measure sample resistance independant of contact resistance. Current runs between outside probes while inside measure the voltage.

What method requires you to know sample geometry

Four point probe

Under what conditions can you use the following equation

Four point probe method when the thin film thickness < probe space meaning you can assume it is infinite

The substrate must also be more resistive than the filmm