Microchip Manufacturing

Silicon Nitride (Si 3 N 4 ) Deposition
Process and the Virtual Chemical
Vapor Deposition Program

Chemical Vapor Deposition A Closer Look: Si 3 N 4
Overall Reaction:
3 SiCl 2 H 2 (g) + 10 NH 3 (g) Si 3 N 4 (s)
Dichlorosilane
(DCS)
Ammonia
Silicon
nitride
+
6 NH 4 Cl (g) +
Ammonium chloride
6 H 2 (g)
Hydrogen
NH 3 (gas)
NH 4 Cl (gas)
H 2 (gas) SiCl 2 H 2 (gas)
Silicon
nitride
SiCl 2 H 2 (gas)
NH 3 (gas)
Graphics copy-write Pro. Milo Koretsky, Chemical Engineering Department at OSU
Photo Courtesy of Silicon Run Educational Video

Chemical Vapor Deposition A Closer Look:
Factors that Effect Film Thickness and Uniformity
• Absolute flow rates of ammonia
to DCS
• Ratio of ammonia to DCS (fixed)
• Temperature (5 zones)
• Reaction time
• Pressure (fixed)
We’ll explore the results of changing
some of these factors.
DCS (gas)
NH 3 (gas)
NH 4 Cl (gas)
H 2 (gas)
NH 3 (gas)
DCS (gas)
Thickness
Film
Substrate

Virtual CVD Overview
Choosing the Virtual CVD reactor parameters
Pressure
is Fixed
Each run costs $

Film Thickness [A]
Film Thickness [A]
Measurement – Thickness & Uniformity
• Film thickness is determined by the amount of material
that reacts and is grown on the wafer
• Uniformity describes the evenness of film thickness on
the wafer
45% Uniformity 100% Uniformity
1000
1000
800
600
400
200
0
-150 -50 50 150
x position
800
600
400
200
0
-150 -50 50 150
x position

Wafer #
Measurement – Thickness & Uniformity
• Film thickness is determined by the amount of material
that reacts and is grown on the wafer
• Uniformity describes the evenness of film thickness on
the wafer
NH 4 Cl (gas)
H 2 (gas)
NH 3 (gas)
200
150
50% Overall Efficiency
SiCl 2 H 2 (gas)
0
100
50
SiCl 2 H 2 (gas)
NH 3 (gas)
79% Overall Efficiency
0 2000 4000 6000 8000 10000
Thickness [A]

Measurement via Ellipsometer
• The ellipsometer is used to measure the
thickness and refractive index of
transparent films.
• It is made of a light source and polarizer
on one side and a analyzer and detector
on the other side.
Detector
Analyzing
Polarizer
Substrate
Light Control
Light Source
Polarizing
Sheet
Analyzer &
Detector
Light Source,
Control &
Polarizing
Sheet
• Light from the source is polarized
and reflected off the film.
• The analyzer is rotated till no light
passes through it.
• The angle of rotation depends on the
thickness of the film.

Virtual CVD Overview
Choosing the locations on the wafer to measure
Each measurement costs $

Virtual Chemical Vapor Deposition
(VCVD) Program
VCVD Program
Semiconductor Manufacturing Fab
Photo Courtesy of http://webmedia.national.com/gallery/06/06_rgb.jpg

Your Objectives:
•Optimize “Recipe”
◦high uniformity (within wafer and between wafers)
◦meets a target thickness of 1000 Angstroms
•Minimize Cost

Let’s Get Started
•Open VCVD Program...