Exhaust gas cleaning by thermal decomposition and wet scrubber.
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Burn plus wet scrubber for exhaust gas cleaning.

This type of exhaust gas cleaning system consists of several units. In a first step soluble and corrosive gases can be abated by a washer in order to protect the burner. SWB series abatement systems for waste gas treatment include this option, SBW series abatement is delivered without this option. A pre-washer is recommendable, when the exhaust gas contains hydrogen halides like HCl and HBr, which are very corrosive or when they contain metal halides like WF6. The second step is the main unit of the gas cleaner: the burn chamber, where the electrical combustion of insoluble compounds happens. Here the waste gas is heated and oxidized in order to destroy toxic compounds. Very important is the temperature distribution in this combustion unit. It has to made sure that the gas reaches a minimum temperature in order to crack the toxic components. During this decomposition quite often a lot of dust is generated and sometimes also soluble or corrosive gases. This dust has to be removed also from the exhaust gas. This can be achieved in two steps, using a swirl unit and a two step wet scrubber unit. As an option, a cooler can be installed inside the circulation tank. Remaining moisture is removed in a demister.

Abatement, combustion and wet scrubber

Several types of burn and wet abatement systems are available, listed in the following table. All main parts are made of stainless steel, the reactor is made of Inconel and the circulation pump is teflon coated. The reactor is equipped with  a multi-construction heater and an auto-cleaning system. The process control is done by PLC control, heater power detection system, SRC heater power control and visualization achieved by a TFT monitor. As an option, a central, PC based monitoring system is available. Several scrubber can be connected to this system. The status of all scrubbers can be displayed there. Improved safety functions, various interlocks and water leak detection systems are installed. The footprint of the system is small and total equipment is designed in order to work at lowest cost.

Burn and wet scrubber overview

SemiAn offers abatement systems consisting of an electrical combustion and a wet scrubber, which have been developed for cleaning waste gas from single process tools, as they are used in the semiconductor and LCD industry. Therefore our gas cleaner are sized for a gas flow in the range of 100 - 1.200 slm or 6 - 72 m3/h. Of course, we can also offer gas scrubber of that size for other applications also. Our equipment is reliable and cost effective.

exhaust gas cleaner SBW200 abatement system SBW200 waste gas cleaner SBW201

SBW200

SWB200

SBW201

SBW 100 / SBW 200 (SemiAn burn - wet)

Gas treatment and abatement type scrubber for high temperature oxidative reaction and soluble gas treatment by wet scrubbing with circulation system. This system is mainly used for the cleaning of exhaust gas from ion implantors, PE-CVD, LP-CVD,  and AP-CVD equipment as well as for MO-CVD (Optoelectronics).

SWB 200 (SemiAn wet - burn - wet)

Gas treatment and abatement type pre-wet scrubber and oxidative reactor and main wet scrubber. Exhaust gas cleaning is achieved in three steps: Abatement of soluble gases and by-products in pre-wet scrubbing section, treatment of pyrophoric, inflammable gases in high temperature oxidative reactor section, treatment of soluble gases by wet scrubbing with a circulation system. This system is used mainly in combination with PE-CVD (semiconductor and LCD manufacturing), LP-CVD, AP-CVD and MO-CVD (optoelectronics).

SBW 201 / SBW 202

Large version of the burn-wet scrubber, consisting of several parallel oxidative reactors and a main wet scrubber. Exhaust gas cleaning is achieved in two steps: Treatment of pyrophoric, inflammable gases in high temperature oxidative reactor section and treatment of soluble gases by wet scrubbing with a circulation system. This system is used for LCD manufacturing in combination with PE-CVD, for MO-CVD (optoelectronics) and for epitaxy reactors.

Measurement Data

The following chemicals can be removed from the exhaust gas. In the table the maximum inlet concentration and the minimum outlet concentration for several gases are given as well as the related TLV (Threshold Limit Values). The chemical reaction describes the oxidation in the burner. In the wet scrubber, HF and HCl are then dissolved. Chlorine reacts  in the wet scrubber with water to HCl and hypochloric acid HClO.
Gas Max. inlet
concentration
in ppm
Min. outlet
concentration
in ppm
TLV
in ppm
Efficiency
in %
Chemical reaction (combustion)
AsH3 5,000 0.01 0.05 >99.99 2 AsH3 + 3 O2PfeilAs2O3+ 3 H2O
B2H6 2,500 0.01 0.1 >99.99 B2H6 + 3 O2PfeilB2O3+ 3 H2O
C2F6 50,000 1200 n.a. 97.60 C2F6 + 2 O2+ 3 H2Pfeil2 CO2 + 6 HF
Cl2 10,000 1 1 99.99 stable
GeH4 4,000 0.02 0.2 >99.98 GeH4 + 2 O2PfeilGeO2 + 2 H2O
H2 125,000 0.5 5 >99.99 2 H2 + O2Pfeil2 H2O
HCl 3,000 1 5 99.97 stable
NF3 50,000 5 10 99.99 4 NF3 + 3 O2Pfeil2 N2+ 6 OF2
NH3 10,000 5 25 99.95 4NH3 + 3 O2Pfeil2 N2+ 6 H2O
PH3 6,000 0.01 0.3 >99.99 2 PH3+ 4 O2PfeilP2O5+ 3 H2O
SF6 5,000 75 1,000 98.50 SF6 + O2 + 3 H2PfeilSO2 + 6 HF
SiF4 4,000 1 n.a. 99.98 SiF4 + O2PfeilSiO2 + 2 F2
SiH2Cl2 1,000 1 5 99.90 2 SiH2Cl2+ 3 O2Pfeil2 SiO2 + 2 H2O + 2 Cl2
SiH4 16,000 0.5 5 >99.99 SiH4 + 2 O2PfeilSiO2 + 2 H2O

Recommended scrubber

In the following list, the most common processes used in the semiconductor industry, which require exhaust gas cleaning are listed. Dry etching equipment is produced for example by Applied Materials or Lam Research. Common etched layers are metallic layers, poly-silicon layers, nitride, oxide and tungston layers. PECVD is used to produce special layers, like oxides, PSG and BPSG as well as Tungston at low temperature. LPCVD is normally done in vertical furnaces, e.g. from Koyo Thermo Systems. Nitride, poly-silicon and TEOS layers are produced with this equipment. In ion implantation equipment also toxic gases are used, which require decombustion. MOCVD is used with III-V-semiconductors. A typical manufacturer of this equipment is Aixtron.
In some cases special caution has to be taken for inflammable gases or for exhaust gas which could cause clogging by depostion of solid material in the tubes.
Alternative wast gas cleaning methods are wet scrubbing and chemisorption. You can find a complete overview over our abatement system on our SemiAn abatement page.
Process Typical Gases Recommended Scrubber Type
Dry Etch Metal Cl2, BCl3, SiCl4, CHF3, CF4, SF6 SSD or SWB

Poly silicon HBr, Cl2, NF3, SF6 SSD or SWB

Nitride HBr, CF4, SF6 SSD or SWB

W, Al Oxide Cl2, SF6, CHF3, CF4, NF3 SSD or SWB
PECVD BPSG TEOS, TMP, TMB, N2O, SIH4, B2H6, PH3, C2F6/NF3 SBW

PSG SiH4, PH3, N2O, TEOS, TMP, C2F6/NF3 SBW

Oxide/Nitride SiH4, NH3, N2O, C2F6/NF3 SBW

Tungston WF6, NF3, SiH4 SBW
LPCVD Nitride DCS, NH3 SBW

Poly silicon SiH4 SBW

(doped) TEOS TEOS, PH3 SBW
Ion Implant B2H6, BF3, PH3, AsH3, Ar SSD or SBW
MOCVD GaAs H2, AsH3, MO sources SBW

InP H2, PH3, AsH3, MO sources SBW

GaN H2, NH3, MO Sources SBW
Crystec Technology Trading GmbH will be pleased to further discuss details with you.
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