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The Technical Principles of Acid Fumes Collection
System and Practical Application
Introduction
• Acidic, alkaline and organic gas fumes are many industrial
production, including semiconductor and optoelectronics
industry processes as unavoidable by-product, due to the
extremely small particle size of smoke particles and enable it
to cause lung disease through the upper respiratory tract of the
human body; therefore, 2012.05.14 Taiwan EPA amended air
quality standards, the fine particles (PM2.5) included in the
regulation, refers to the fine particles suspended in the air,
aerodynamic diameter less than or equal to 2.5 microns
particles, the particle size is extremely small, easy to enter the
body with the breath, the impact on health. Therefore, how to
control the emission of smoke and sub-micron particles is one
of the important direction of the air pollution control technology.
Particle diameter analysis of aerosols
Aerosol Diameter(μmΦ)
Clouds and fog < 2
Hydrochloric acid mist 1-3
Sulfuric acid mist 0.3-2
Ammonium chloride fume 0.05-1
Tobacco smoke 0.01-1
Particles size distribution of the aerosols from silane
combustion from APCVD
Cause of acid gas fumes (white smoke) 1
• Acidic wet etching(heating)
□ Aluminum: Acetic acid
□ ITO Rework: Hydrochloric
□ Aluminum oxide: Sulfuric acid and Phosphoric acid
• Aqua regia(nitrohydrochloric)
□ Hydrochloric
• Metal cleaning
□ Indium ball: Hydrochloric
Cause of acid gas fumes (white smoke) 2
• Plasma etching:
□ Ammonium fluoride
□ Silica particle
• Plasma-Enhanced chemical vapor deposition (PECVD)
□ Ammonium fluoride
□ Silica particle
• Wafer reclaim
□ Ammonium fluoride
Cause of acid gas fumes (white smoke) 3
• Mixed acid-Base exhaust
□ Ammonium fluoride
□ Ammonium chloride
□ Ammonium nitrate
□ Ammonium sulfate
Introduction of the improved Venturi Scrubber system 1
Gas+particles
Principle of the improved Venturi Scrubber System 2
• The improved Quasi-Venturi Scrubbers are mechanical
devices that rely on shearing and impaction forces to break
water into fine droplets. The goal is to produce an evenly
distributed regime of fine droplets at high density. The fine
droplets are obtained by providing a nozzle just ahead of
quasi-venture throat. Contaminant particles will impact on the
droplets, enlarged through similar collisions and become
inertially separated through application of centrifugal force.
Efficiency of the improved Venture Scrubber system 3
Introduction of acid gas deep filtration system 1
(SiO2/NH3/HCl/H2SO4)
Principle of acid gas fume deep filtration system 2
Gas flow
Principle of acid gas fumes deep filtration system 3
• Filter construction:
The filters are typically constructed in vessel and consist of
special panel(or cylinder type) mist eliminator densely packed
between reinforcing screen. The filter material and material’s
packing density determines the operating parameters of filter
(such as pressure drop, collection rate and gas through-put
etc…). At the screen ends, plates and flanges are attached to
permit a variety of mounting and draining methods.
DRE of acid gas fumes deep filtration for semiconductor fab.
ITEM 01.SEX XX
(inlet)
01.SEX XX
(outlet)
DRE
(%)
ug/m3 ppbv ug/m3 ppbv
Chloride(Cl-) 491 339 ND ND 100
Sulfate ion(SO42-) 43.7 11.1 ND ND 100
Ammonium ion(NH4-) 320 435 0.867 1.18 99.73
Sampling date: 2016.06.22
Introduction of acid gas fume collection system 1
Venturi Scrubbing Deep Filtration
Introduction of acid gas fume collection system 2
(HCl/FeCl3)
Pictures of acid gas fume collection system 3
(HCl/FeCl3)
DRE of acid gas fume collection system 4
(HCl/H2SO4)
Layout DWG. of acid gas fume collection system 5
(HF/NH4/SiO2)
Picture of acid gas fume collection system 6
(NH4F/HF/H2O2/H2SO4)
Principle of acid gas fumes collection system 7
• Acid fumes are suspended liquid or solid particles ranging in
diameter from the submicron range to the 3µm size. The acid
fume removal system to collect submicron particulates which
are hygroscopic using the principles of condensation scrubbing.
Acid fumes as small as 0.3 microns in diameter pass through
gas scrubbing stages and particle growth stage within the acid
fume removal system before being collected by a final
entrainment filtration stage.
Principle of Acid Gas Fumes Collection System 8
• Partcles Collection Mechanism:
Inertial impaction devices previously discussed give high
efficiency on particles above 5μm in size and often reasonable
efficiency on particles above to 3μm size at moderate pressure
drops.
However, this mechanism becomes ineffective for particle
smaller than 3μm because of the particle gaslike mobility. Only
impaction devices having extremely high energy input such as
venturi scrubbers or a flooded mesh pad can give high
collection efficiency on fine particles, defined as 2.5μm or 3μm
and smaller, including the submicron meter range.
Principle of acid gas fumes collection system 9
• Fine particles are subjected to brownian motion in gases, and
diffusion deposition can be employed or their collection.
Diffusion deposition becomes highly efficient as particles
become smaller, especially below 0.2μm to 0.3μm. Randomly
oriented filter having tortuous and narrow gas passages are
suitable devices for utilizing this collection mechanism.
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