Application of surface wave plasmas as an innovative technology for the destruction and removal of perfluorocompounds (PFC) emanating from semiconductor fabrication tools is demonstrated. The destruction of parts per thousand (ppt) concentrations of hexafluoroethane, C2F6, in oxygen and natural gas mixtures has been investigated as a function of microwave power in a low-pressure plasma reactor at 11.3 Torr. Effluent analysis included the determination of destruction and removal efficiencies (DRE) and product distributions by Fourier transform infrared spectroscopy and mass spectrometry. Destruction and removal efficiences of up to 99.6% for C2F6 were achieved using applied microwave powers from 500 to 2000 W, which corresponded to millisecond range residence times within the plasma. Product analysis indicated that hexafluoroethane conversion was limited to low molecular weight gases such as CO2, CO, COF2, H2O, and HF. CF4 was not produced as a plasma byproduct in any significant quantities. These investigations indicate that surface wave plasma destruction of perfluorocompounds at the point of use is a viable nonintrusive abatement technology for application to semiconductor manufacturing tools.

Projected exponential growth in semiconductor device manufacture over the next few years demands technology to reduce the corresponding increase in etchants such as perfluorocompounds (PFCs), CHF 3 , and SF 6 that would be emitted into the atmosphere. These compounds are a cause for concern because of their large global warming potentials relative to CO 2 and of their long lifetimes in the atmosphere, often tens of thousands of years. We demonstrate that a plasma-based technology can yield effective (up to 99.9%) destruction and removal efficiencies (DREs) for CF 4 and CHF 3 present in etch recipes widely used in the semiconductor industry. Specifically, we report application of surface wave plasmas at 2.45 GHz for this purpose. Post-plasma effluent analysis included the determination of DREs and product distributions, simultaneously by gas-phase FTIR and QMS. Application of microwave powers from 500 to 1950 W were investigated and DREs for CF 4 and CHF 3 reported. Final product analysis indicated that PFC conversion was limited to low molecular weight gases such as CO 2 , CO, COF 2 , H 2 O, and HF. These investigations demonstrate that surface wave plasma destruction of the referenced PFCs at the output of semiconductor etch tools is a viable nonintrusive point of use abatement technology.

Today's electronic assembly manufacturing operations can be complex combinations of process steps such as IR reflow, wave soldering, special soldering of connectors or sensitive components, cleaning, rework, etc. Such multiple exposures to elevated temperatures and/or oxidising environments (e.g., aqueous cleaning) can have a negative effect on the solderability of printed wiring board (PWB) surfaces. This in turn may limit the effectiveness of subsequent soldering operations, such as wave soldering following an IR reflow step. The purpose of this study is to assess the impact of individual assembly process steps on the solderability of PWB surfaces. The PWB surfaces are initially treated with protective coatings of benzotriazole (BTA). The process steps investigated include: IR reflow in air and in nitrogen; vapour phase reflow; aqueous cleaning; adhesive cure; and wave soldering as a function of solder temperature and flux type. Meniscograph wettability testing is used to measure relative solderability changes, and Auger electron spectroscopy (AES) is used to monitor surface chemical changes, particularly oxide formation. The overall result is a body of fundamental information providing insight into optimisations of process flows, equipment operating specifications, process temperatures and selection of flux types.

The performance and reliability of personal computers, workstations and other electronic products depend on the effective soldering of electronic components to printed wiring oards (PWBs). The copper surfaces of PWBs are frequently treated with benzotriazole (or similar organic complexes) to preserve solderability by preventing copper oxide formation. However, new assembly process techniques and more complex processes may degrade protective organo-copper surface complexes and allow copper oxidation to occur, thus inhibiting subsequent solder operations. This study uses Auger electron spectroscopy (AES) in conjunction with meniscograph wettability results to determine the effects of processing conditions on the solderability of PWB surfaces. Effects are characterized for aging up to 19 months; Infrared (IR) reflow in air and nitrogen; cleaning; and temperature cycles associated with adhesive or encapsulant cure. Surface compositions, oxide thicknesses, and solderability measurements are correlated to the above process steps. For example, IR reflow in air increases oxide thickness from ∼10 Å to ∼150Å (relative to sputtering rates in Ta2O5 with an attendant increase in the meniscograph time-to-neutral-buoyancy from <2 seconds to >10 seconds, relative to unprocessed PWBs. Such fundamental information serves as an invaluable complement to standard phenomenological observations of defective solder joints, and can aid in guiding processing decisions for improved yield and reliability.