Electrochemical Technology CorporationDryScrub®



Frequently Asked Questions

  1. Does the DryScrub®Plasma Trap System interfere with the existing vacuum system?
    NO. The DryScrub
    ® Plasma Trap is virtually transparent to any existing vacuum system. The current design of 2DH electrode gives conductance >50,000 liter/sec in the viscosity flow regime and >5,000 liter/sec in the transition regime. DryScrub® Systems have been successfully installed in many LPCVD/PECVD including: AMAT PE5000, ASM, Axtron, Kokusai (KE), Novellus, SVG, TEL, and other systems.
  2. What other applications can the DryScrub® Plasma Trap System be used for?
    ® Plasma Trap utilizes the patented RF capacitance coupled plasma technology to treat semiconductor processing exhaust gases. The applicable processes include LPCVD/PECVD, silicon and metal nitrides and oxides, MOCVD and ALD metals, Ion Implantation, Plasma Etching and Chamber-clean PFC abatements. For more information, please call us.
  3. What can the DryScrub® Plasma Trap System do to abate etching and chamber-clean PFC gases?
    For etching gases (CF
    4, C2F6, etc), DryScrub® systems provide adequate RF energy to decompose the unpolarized and stable PFC gas molecules into polarized and active radicals/molecules under vacuum without added gases. The F atoms etch the as deposited silicon nitride and oxide to form SiF4 and clean up the electrode. The polarized components and SiF4 are soluble in water/chemical and can be scrubbed by any central wet chemical scrubber. It reduces the PFC emission and protects the environment while recycle the electrode for next deposition process. It eliminates powder formation during deposition cycle and abates PFC during the etch clean cycle.

    For CVD Chamber-clean effluents, the DryScrub
    ® system can do several things to improve the overall performance. Firstly, it can strip the solid components of hydride processing gases from exhausts. This will reduce the flow of particles to your downstream particle filters and membrane, which facilitate downstream PFC capture and recycle processes. Secondly, the films on the DryScrub® electrodes, which have almost identical chemical components to wafer films, can react with un-reacted Chamber-clean PFC gases to increase the reaction efficiency of PFC gases. This application is used to reduce the PFC emission. Under such application, the electrode has a much longer life time. Various functions can be achieved by programming the RF power supply differently.
  4. Why the DryScrub® Plasma Trap System can reduce the particle counts on wafers in CVD processing?
    There are many sources of particles in a CVD process. From the gas source line, the wafer handling, the chamber deposited film peeling off and from the uncontrollable but most important, back diffusion of particles generated in downstream gases. The reactive process gases are energized after the process tool. These reactive nano-metric size molecules back diffuse into the process chamber. They react with other particles and coagulate together, larger than 100 nm size particles are formed within short reaction times. The coagulating process is amplified by the seeding of the already existing molecular clusters and sub-micron particles that have been generated by the pump. For condensable gases, such as TEOS and NH
    4Cl, coagulation is further enhanced by the nucleation process, due to the large temperature drop at the foreline.

    With an installed DryScrub
    ® Plasma Trap between the CVD chamber/furnace and the pump, the charged plasma strips solid components and deposits them in dense films, >99.5% elimination of solid bearing gases by deposition reduces particle formation. At the same time, the charged plasma inside the capacitor like electrode also functions as a trapper, it's like an electrostatic precipitator for particles flowing from upstream and downstream. DryScrub® improves the wafer yield and reduces the cost of ownership (COO).
  5. What is the advantage of choosing DryScrub® Technology to abate exhaust gases, compared to conventional burn box, CDO, GRC, etc.?
    Assuming Burn Box, CDO and other technologies can abate the exhaust gases with the same efficiency as DryScrub
    ® System, then, the main advantage of using DryScrub® is that it benefits pump and other downstream facilities. The DryScrub® is installed before the pump. >99.5% solid components of hydride gases are stripped by the DryScrub® System, leaving neutral gases to pass through the pump and downstream facilities. This will prevent pump failure, APC valve and vacuum line clogging issues. It reduces operation cost and increase process up-time.

    Open flame technology burns exhaust gases. It requires additional fuel such as H
    2 or natural gases. Since exhaust gases have been highly diluted, for example below 2% for a hydride gas such as silane, most of the burning is of the natural gases, which heats air and leads to the formation of toxic NOx. In addition, solids are expected to deposit, by gas phase nucleation, near the nozzle and downstream. The foam deposition requires the cleanup of the nozzle virtually daily when on a production line, an extensive maintenance and downtime. Pyrophoric gases such as SiH4 are trapped in the foams, which can ignite, the cost of fuel and safety issues have to be considered.

    Controlled Decomposition and Oxidation (CDO) technology uses heating elements to supply thermal energy for the exhaust gas reaction and decomposition. The addition of N
    2 and O2 (air) dilutes and increases the overall volume of exhaust gas. Under atmospheric pressure, the exhaust gases nucleate and form foam type byproducts on the hot surface. Once a loose foam type layer is formed, it reduces the rate of heat transfer to the bulk exhaust gases, and lowers the exhaust gas reaction rates exponentially. Therefore, the scrubber efficiency decays dramatically with time once a loose foam type layer is formed.

    The gas reactor column (GRC) technology uses solid inorganic materials to react exhaust gases on the solid granular surfaces. When new, inorganic solids have many fresh sites to allow gas molecules to be adsorbed and reacted effectively. However, once the reaction products cover the solid surface as an oxide or nitride sheath, the reaction rate reduces dramatically, toxic gases must diffuse and react with the inner core of the inorganic materials. Please draw the parallel that very thin oxide or nitride layers are purposely deposited on wafers as barrier layers to block the penetration of gas and moisture. The nitride or oxide by-products block the diffusion of exhaust gasses and stops the reaction. When new the GRC can be effective, but as the surface gets clogged most of the exhaust gas will simply pass by and efficiency drops dramatically. The GRC cartridge itself contains a large quantity of inorganic solid. After the gas treatment, GRC generates a large quantity of waste in volume. The cost for solid waste disposal is high. Unlike the DryScrub
    ® System which uses one electrode for any type of process gas, GRC uses different types of cartridges for various processing gases.
  6. What is the DryScrub® preventative maintenance (PM) procedure?
    The PM procedure of DryScrub
    ® is simple. Only the electrode needs to be replaced. This can be done within 30 minutes.
  7. What is the DryScrub® preventative maintenance frequency?
    The PM frequency depends on the hydride gas flow rate and processing time. Normally, an electrode can last for a couple of months. Please refer to the Technical Notes. This expression is given to calculate how many runs or the total deposited film thickness the electrode can handle before replacing. If you have any difficulty to figure it out, please call ETC. One of our engineers can help you out within a few minutes.
  8. What waste gases leave the DryScrub® System?
    Please refer to the following note "Summary Table of DryScrub® Collection Capacity" for the components of waste gases leaving the DryScrub
    ®. If your process is not listed in the Summary Table of DryScrub® Collection Capacity, please call ETC for help!
  9. What are the materials collected by the electrode and how should I dispose of the used DryScrub® electrode?
    The solid materials in the electrode are virtually identical to those on wafer films. The Summary Table of DryScrub
    ® Collection Capacity shows the waste materials for various LPCVD/PECVD processes. Since the solids in the electrode is more or less non-toxic, they can be disposed with other solid wastes. Please check with ETC and your safety team for more details.



Home   Why DryScrub?   DryScrub Overview   DryScrub Systems   Application Reports
Performance Benefits   FAQ's   Technical Notes   Images   Register   About ETC

© Copyright 2001 DryScrub ETC.

Tel: +1-408-DryScrub




Toll Free: +1-888-DryScrub




Fax +1-510-818-9993



 To contact us.