PRESENTED BY- PRESENTED BY- ANUBHAV SINGHANUBHAV SINGH

FINAL YEARFINAL YEAR

Instrumentation Instrumentation &Applications of FTIR &Applications of FTIR

SpectroscopySpectroscopy..

What is FT-IR-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.

INTRUMENTATIONINTRUMENTATION

Interferometer

He-Ne gas laser

Fixed mirror

Movable mirror

Sample chamber

Detector

Beam splitter

Lambert-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

Principle Of FTIR SpectroscopyPrinciple Of FTIR Spectroscopy--

1. POLYMER PROCESSING

– CURING

2. PLASMA ETCHING

3. IDENTIFICATION OF MATERIALS:

– POLYMER DIELECTRICS

– INORGANIC THIN FILMS

– CONTAMINATION

– UNKNOWN COMPOUNDS

4. ANALYSIS OF FORMULATIONS

Practical FTIR applications in packagingPractical FTIR applications in packaging

Drying and Curing polymersDrying 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

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.

Drying PolyimideDrying Polyimide

Monitoring product after curingMonitoring 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 inamounts of 1% and in some cases as low as 0.01%.

PlasmaPlasma EtchingEtching

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)

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.

Identifying Contamination

Identification of Materials and ChemicalsIdentification 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.....

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.

Specific groupsSpecific groups

Alcohols Show a strong, broad band for the O-H stretch from 3200-3400 cm-1

1-butanol

Primary Amines Shows the –N-H stretch for NH2 as a doubletdoublet between 3200-3500 cm-1

2-aminopentane2-aminopentane

Spectra of Thin Inorganic FilmsSpectra of Thin Inorganic Films

Monitoring of oxidation of an Aluminium film.

Other FTIR ApplicationsOther 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.

FTIR limitationsFTIR 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.

Comparison of FT-IR & IR Comparison of FT-IR & IR

Dispersive IR Fourier transform IR

1. There are many moving parts, resulting in mechanical slippage. 2. Calibration against reference spectra is required to measure frequency.  3. Stray light causes spurious readings.  4. To improve resolution only a small amount of IR beam is allowed to pass.

1. Only the mirror moves during the experiment. 2. Use of laser provides high frequency accuracy (to 0.01 cm-1).  3. Stray radiations do not affect the detector. 4. A much larger beam may be used at all time. Data collection is easier.

Dispersive IR Fourier transform IR

 5. Only radiation of a narrow frequency range falls on the detector at one time. 6. Slow scan speed.

 5. All frequency of radiation falls on the detector simultaneously. 6. Rapid scan speed.

AdvantagesAdvantages--

Fellgett's (multiplex) Advantage-Fellgett'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)signal-to-noise (S/N ratio) of the spectrum.

Connes Advantage –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.

Advantages-Advantages-

Jacquinot Advantage-Jacquinot 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.

ConclusionConclusion

AdvantagesAdvantages--

– 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

Disadvantages-Disadvantages-

– Interpretation of the data requires some experience.

– No useful detailed database available for the semiconductor

processes.

– Carbon di-oxide & Water Sensitive.

FTIR InstrumentsFTIR Instruments

microscope

Microscope