This document discusses instrumentation and applications of Fourier transform infrared (FTIR) spectroscopy. It begins by explaining the basic principles of FTIR spectroscopy, how it works, and its advantages over dispersive infrared spectroscopy. It then describes various applications of FTIR spectroscopy like polymer processing, plasma etching, identification of materials, and analysis of formulations. Specific examples discussed include drying and curing polymers, monitoring plasma etching, identifying contamination, and distinguishing different functional groups in molecules. The document concludes by noting the advantages, limitations, and comparison of FTIR spectroscopy to dispersive infrared spectroscopy.

1. Instrumentation &Applications
of FTIR Spectroscopy.
PRESENTED BY- ANUBHAV SINGH
FINAL YEAR

2. What is FT-IR FT-IR stands for Fourier Transform Infra Red, the preferred method of
infrared spectroscopy.
 In infrared spectroscopy, IR radiation is passed through a sample, Some of the
infrared radiation is absorbed by the sample and some of it is passed through
(transmitted). The resulting spectrum represents the molecular absorption and
transmission, creating a molecular fingerprint of the sample.
 Like a fingerprint no two unique molecular structures produce the same
infrared spectrum.
 This makes infrared spectroscopy useful for several types of analysis.
 This system is based on the Michelson- Morley experiment used to measure
the influence of earth rotation on the speed of light.

3. INTRUMENTATION
He-Ne gas laser
Movable mirror
Beam splitter
Sample chamber
Fixed mirror
Interferometer
Detector

4. Principle Of FTIR SpectroscopyLambert-Beer´s law
•
FTIR spectra can provide quantitative information
•
Lambert-Beer´s law correlates physical properties and chemical
composition :
– The concentration of a sample can be estimated by:
A = ε.c.d
– Where:
• ε is the molar absorption coefficient
• c is the sample concentration
• d is the sample thickness

5. Practical FTIR applications in packaging
1. POLYMER PROCESSING
– CURING
2. PLASMA ETCHING
3. IDENTIFICATION OF MATERIALS:
– POLYMER DIELECTRICS
– INORGANIC THIN FILMS
– CONTAMINATION
– UNKNOWN COMPOUNDS
4. ANALYSIS OF FORMULATIONS

6. Drying and Curing polymers
 Drying of photo-sensitive materials is critical
– Impacts photo response
 Optimizing curing:
– Determine optimum intermediate curing in multi-layer applications
• Curing level kept low for layer to promote inter-layer bonding.
• Curing level high enough to withstand sputtering thermal load.
– Checking on consistency of curing level.
– Determining curing level and completion.
– Checking on the effects of novel curing methods
• Microwave

7.  Optimizing curing profile
– Ramping speed.
– Monitoring effects of background curing atmosphere.
OthersOthers
•Drying photo resist materials.
• Drying polyimide
- Identification of material condensing on walls of
a poorly ventilated drying oven.

8. Drying Polyimide

9. Monitoring product after curing
1. Curing atmosphere:
– Evaluation of thermo-oxidative and thermal stability.
– Stability check of cured polymers to environment.
• Post curing oxidation in air.
– Troubleshooting curing oven problems.
2. Moisture absorption.
3. Evaluation of oxygen or moisture barrier capabilities.
4. Detection of molecular impurities or additives present in
amounts of 1% and in some cases as low as 0.01%.

10. Plasma Etching
1. Detection of etching endpoint
– contact via holes
– polymer
– oxide
2. Detection of etching problems
– Residual Fluorine on polymer surface
– Polymer or metal oxidation
– Polymer degradation: Identification of bonds damaged by plasma
chemistry
3. Cleaning of via holes
– Very thin films are not detectable in an optical microscope
– Over-etching and under-etching control
– Detection and identification of residues (e.g. ash)

11. Identification of contamination
1. Chemical contamination of parts in processing
– e.g. Permeation or absorption of chemicals in a polymer.
2. Contamination of parts induced by handling, processing,
shipping etc.
3. Aging of vacuum roughing lubricants
– Deterioration of plasma pump oil.
• Acidification, oxidation or fluorination.
4. Vacuum chamber contamination.

12. Identifying Contamination

13. Identification of Materials and Chemicals
1. Identification of compounds
– Matching spectrum of unknown compound with reference
spectrum (fingerprinting).
2. Identification of functional groups in unknown substances.
Ex. Ketones, Aldehydes, Carboxylic Acids Etc.
3. Identification of reaction components and kinetic studies of reactions.
Cont.....

14. 4. Identification of molecular orientation in polymer films
– Need polarized IR set-up.
5. Identification of polymers, plastics, and resins.
6. Analysis of formulations
– Wet etchants
– Cleaning solutions
– Solvents.

15. Specific groups
Alcohols
 Show a strong, broad band for the O-H stretch from 3200-3400 cm -1
1-butanol

16. Primary Amines
 Shows the –N-H stretch for NH2 as a doublet between 3200-3500 cm-1
2-aminopentane

17. Spectra of Thin Inorganic Films
 Monitoring of oxidation of an Aluminium film.

18. Other FTIR Applications
 Opaque or cloudy samples.
 Energy limiting accessories such as diffuse reflectance or FT-IR microscopes .
 High resolution experiments (as high as 0.001 cm-1 resolution) .
 Trace analysis of raw materials or finished products.
 Depth profiling and microscopic mapping of samples.
 Kinetics reactions on the microsecond time-scale.
 Analysis of chromatographic and thermo gravimetric sample fractions.

19. FTIR limitations
1. Molecule must be active in the IR region. (When exposed to IR radiation, a
minimum of one vibrational motion must alter the net dipole moment of the
molecule in order for absorption to be observed.)
2. Minimal elemental information is given for most samples.
3. Material under test must have some transparency in the spectral region of
interest.
4. Accuracy greater than 1% obtainable when analysis is done
under favourable conditions.

20. Comparison of FT-IR & IR
Dispersive IR
Fourier transform IR
1. There are many moving parts,
resulting in mechanical slippage.
1. Only the mirror moves during the
experiment.
2. Calibration against reference spectra
is required to measure frequency.
2. Use of laser provides high frequency
accuracy (to 0.01 cm-1).
3. Stray light causes spurious readings.
3. Stray radiations do not affect the
detector.
4. To improve resolution only a small
amount of IR beam is allowed to pass.
4. A much larger beam may be used at
all time. Data collection is easier.

21. Dispersive IR
Fourier transform IR
5. Only radiation of a narrow frequency
range falls on the detector at one time.
5. All frequency of radiation falls on the
detector simultaneously.
6. Slow scan speed.
6. Rapid scan speed.

22. AdvantagesFellgett's (multiplex) Advantage- FT-IR collects all resolution elements with a complete scan of the
interferometer. Successive scans of the FT-IR instrument are co added and
averaged to enhance the signal-to-noise (S/N ratio) of the spectrum.
Connes Advantage –
 An FT-IR uses a He-Ne laser as an internal wavelength standard. The
infrared wavelengths are calculated using the laser wavelength, itself a very
precise and repeatable 'standard'.
 Wavelength assignment for the FT-IR spectrum is very repeatable and
reproducible and data can be compared to digital libraries for identification
purposes.

23. AdvantagesJacquinot Advantage- FT-IR uses a combination of circular apertures and interferometer travel to
define resolution. To improve signal-to-noise ratio, one simply collects more
scans.

24. Conclusion
Advantages– FTIR is a simple and sensitive analytical tool.
– Provide fast data acquisition tool.
– Simple to operate
– Most useful analytical tool
• To determine the composition of organic materials
• To identify IR transparent or semi-transparent inorganic films
• Provides quantitative determination of compounds in mixtures

25. Disadvantages– Interpretation of the data requires some experience.
– No useful detailed database available for the semiconductor
processes.
– Carbon di-oxide & Water Sensitive.

26. FTIR Instruments
microscope

27. Microscope