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New Aeris-S Technology Helps Increase Subfab Safety While Reducing Emissions

Andreas Nueber, Michael Cox, John Dickinson, Jim L’Heureux and Dustin Ho

The fabrication of advanced gate stacks and complex device geometries increasingly depends on new processes, chemistries and materials that generate substantial volumes of hard-to-treat and potentially dangerous waste byproducts in chamber effluent.

High-aspect-ratio processes (HARP) and “dirty” chemistries—such as flowable CVD (FCVD) based on low-thermal-budget chemical reactions—generate large volumes of byproducts that can clog forelines, gate valves and pumps. Meanwhile, low-material-efficiency processes such as atomic layer deposition (ALD) deposit only a small fraction of the gaseous source material onto the wafer; the rest must be removed from the waste stream. Finally, SiGe, III-V, and other alternative materials and highly reactive precursors may pose safety and operational concerns if they are energetic, pyrophoric or toxic to humans, as many are.

This means it is no longer enough to simply meet governmental emissions regulations, despite how difficult that can be under these new manufacturing conditions. To be successful in today’s hyper-competitive markets, semiconductor manufacturers must place greater emphasis on hazardous material management when treating chamber effluent so that subfab utilities and subsystems remain safe, available, cost-effective and efficient—even under heavy factory loads.

Applied Materials is now developing a promising solution for these challenges: Applied Aeris-S abatement technology.

This new solution operates by converting problematic materials into compounds that can be managed and transported more easily and safely for abatement (either locally or in the central scrubber). Aeris-S technology also improves subfab safety by reducing the levels of flammable, explosive or toxic exhaust gases and the accumulation of potentially hazardous reactive solids downstream of the chamber.

Initially focused on HARP applications, the new Aeris-S technology is currently undergoing beta testing at a number of fabs. The system builds on the success of the Applied Aeris-G pre-pump plasma abatement system, some 2,000 of which are installed at fabs worldwide. Using Aeris-G units has enabled fabs to meet increasingly strict emissions regulations and reduce their carbon footprints while maximizing system uptime and reducing overall costs.

Like the zero-footprint Aeris-G units, the new Aeris-S units sit in the existing pump footprint for each chamber but are placed before the pump so they can treat the actual process gas volume, a much smaller and more concentrated gas volume than what is treated by traditional post-pump abatement technology (see figure 1).

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Figure 1. The Aeris-G pre-pump plasma abatement system enables semiconductor manufacturers to meet greenhouse gas (GHG) reduction goals with no added subfab footprint required. The new Aeris-S system is a pre-pump, magnetically confined, capacitively coupled plasma source used to address environmental, health and safety concerns with CVD and other advanced processes. Aeris-S also helps manage solids accumulation and tool productivity.

However, Applied’s Aeris-S technology brings powerful capabilities to the more challenging abatement requirements at the leading edge of semiconductor manufacturing. For example, the Aeris-G and Aeris-S technologies employ different plasma sources.

Existing Aeris-G units use an inductively coupled plasma source to actively manage process effluent and reduce solids accumulation. This is a more effective solution than passive microwave-based pipe-heating and post-pump purging systems. Aeris-G units virtually eliminate volatile organic compounds (VOCs) and COx from tool exhaust because no fuel is used. They also eliminate NOx emissions because effluent is treated before it is diluted with N2 purge gases. Aeris-G technology demonstrates typical destruction removal efficiencies (DRE) greater than 99% for SF6, CHF3, C3F8, NF3 and C4F8, and greater than 95% for CF4.

By contrast, Applied’s new Aeris-S technology employs a higher-power magnetically confined and capacitively coupled plasma source to dissociate complex molecules, and precipitate and evaporate solids. It features high flow rates (100 slm) and a wide operating range. These features allow users to manage and prevent accumulation of solids in and beyond the foreline, increasing uptime and availability and reducing costs. In addition, these features drive reactions that turn harmful compounds into less harmful ones, reducing potential risks to maintenance personnel.

Figure 2. Illustrations show that Aeris-S abatement technology first turns TEOS effluent into “cleanable” SiO2 (step 1), and then turns the SiO2 into SiF4 (step 2), which is easy for a scrubber to remove from a fab’s waste stream.

Results from the beta tests indicate that Aeris-S technology can effectively treat high volumes of effluents with a wide range of chemistries and foreline pressures. It can significantly lengthen preventive maintenance (PM) intervals for pumps and post-pump abatement equipment, and improve subfab safety by reducing hazardous levels of exhaust gases and downstream accumulations of reactive solids.

Both Aeris-G and Aeris-S units are synchronized with chamber operation and operate on-demand. This can lower the overall utility cost of ownership by up to 70%.

How It Works

To more clearly illustrate the working principle of Aeris-S technology, consider a HARP process that incorporates a TEOS deposition step. The waste stream from TEOS breakdown on the wafer and in the chamber comprises the following molecules: TEOS, which is Si(OC2H5), along with CO, HCOOH, CO2 and CH4. (See figure 2, step 1.)

TEOS and its byproducts are toxic or flammable and the goal is to eliminate them from the waste stream. Applied’s Aeris-S technology performs a two-step process to eliminate TEOS during the cleaning process. First, the Aeris-S converts it into SiO2, which is much easier to handle and is deposited on the pump shields and in the foreline.

Second, NF3 is introduced into the Aeris-S system as a source of highly reactive fluorine radicals (figure 2, step 2). The Aeris-S activates the NF3. Some of the F radicals recombine and don’t react anymore, but some of them convert the SiO2 into SiF4. This removes the SiO2 buildup, and leaves SiF4, which a fab’s central scrubber can manage easily.

The concentration of SiF4 in the effluent can be seen as an indicator of cleaning efficiency (i.e., more SiF4 in the effluent means that more SiO2 effluent has been converted). The removal efficiency of Aeris-S units in beta tests is shown in figure 3.

Figure 3. Aeris-S technology reactivates F2 to F radicals and thereby converts SiO2 to SiF4. The concentration of SiF4 in chamber effluent can be used as an indicator of cleaning efficiency, because more SiF4 in the effluent means that more SiO2 has been converted. The figure captures data from three tests, showing twice the SiF4 emission levels with Aeris-S technology.

Applied’s new Aeris-S technology is designed for low operating costs and has a flexible architecture for easy cleaning and maintenance. The units are externally programmable to control reagent flow, power and purge functions, and can interface with production tools from Applied Materials or other manufacturers, as well as a fab’s host computer system.

It is always Applied Materials’ goal to have increased uptime, higher efficiency and lower operating costs go hand-in-hand with good environmental stewardship and safe operating practices. The new Applied Aeris-S technology will help ensure that customers continue to enjoy those benefits no matter how complex semiconductor fabrication becomes. For additional information, contact andreas_neuber@amat.com.