Mark Allen George

Materials selection for HBr service

Abstract This study was undertaken to determine the compatibility of hydrogen bromide (HBr) with common materials of construction used for specialty gas delivery systems. Reactions between reactive gases and materials of construction can result in the formation of particles and volatile metal complexes as well as the creation of corrosion products that can retain water. We found that when moisture is below 1 ppm v (designated as anhydrous ), bromine from HBr is not incorporated beyond the native oxide of electropolished 316L stainless steel (EP316L) and no macroscopic degradation of the metal occurs. Also, if adequate purging and evacuation procedures are followed to remove the HBr, this material can be exposed to moist air without diminishing the initial surface quality. However, if adequate precautions are not followed to eliminate water in the presence of HBr, iron-and bromine-rich crystalline deposits form on the surface. Purge and evacuation procedures are inadequate for removal of the reactive species on this surface and corrosion proceeds upon subsequent exposure to air. EP316L exposed to HBr containing 1700 ppm v H 2 O appears visually unaltered, but close inspection by SEM reveals the onset of corrosion. Of the materials examined in this study, Nickel-200 and Hastelloy C-22 are more resistant to HBr corrosive environments. In contrast, deleterious reactions occur between anhydrous HBr and elemental iron and the iron-rich surface of oxygen-passivated 316L.

Chemical vapor cleaning of Si and SiO/sub 2/ surfaces

A novel vapor phase clean is shown to be a viable method for removing copper and iron from wafer surfaces. Utilizing thin films and sub-monolayer samples of copper and iron on Si or SiO/sub 2/ substrates the reaction of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (CF/sub 3/COCH/sub 2/COCF/sub 3/ or H/sup +/hfac) with these metals has been explored as a potential vapor phase clean. It is shown that the chemical state of the surface metal is an important factor in the removal of these metals. The reaction of CuO and Cu/sub 2/O with H/sup +/hfac results in volatile reaction by-products of Cu/sup 11/(hfac)/sub 2/ and H/sub 2/O. Additionally, the reaction with Cu/sub 2/O yields Cu/sup (0/). Reaction of H/sup +/hfac with iron contamination is more complex and leads to at least two different types of reactions. These reactions include a nucleophilic substitution reaction and a reaction leading to a mixed ligand system. The final surface metal concentration is dependent upon the processing conditions and can result in concentrations similar to those achieved with standard wet cleans.

The Effects of Chemical Vapor Cleaning Chemistries on Silicon Surfaces

This study explores the effects of two chemical vapor cleaning chemistries on silicon surfaces. The silicon surfaces are not significantly roughened by exposure to either process. Trace amounts of fluorine are found on the surfaces exposed to 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (HFAC). A thin silicon nitride film forms on the silicon surface as a result of exposure to the HMDS process and is attributed to the H 2 /N 2 plasma treatment used in the first step of the process.

Examining process induced contamination: plasma etching and chemical vapor deposition reactors coupled to an in situ surface analytical capability

A comprehensive approach developed for the systematic examination of process induced contamination and reaction mechanisms seen during electronics processing is discussed. The approach is based on a tool which models a cluster tool environment, incorporating both plasma and thermal processing, and coupling them in vacuo to a surface analytical instrument. This tool has been used to examine a number of contamination issues including those arising from the use of fluorine-containing plasma exposed to aluminum and anodized aluminum. It was found that coupons of aluminum and anodized aluminum alloys exposed to NF/sub 3//Ar or C/sub 2/F/sub 6//O/sub 2/ plasmas were fluorinated by similar chemical mechanisms but at different rates. These rates correlate with fluorine atom concentrations in the respective plasmas and with DC self bias or ion bombardment. Using in vacuo transfer of the exposed samples, both the extent of reaction between the plasma and substrate and plasma/substrate reaction mechanisms were determined by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The results suggest that to take advantage of chemical differences between various plasma-cleaning gases, process times should be optimized for fluorine atom concentrations and etch rates.<<ETX>>

Chemical Vapor Cleaning of Sodium from SiO 2

Chemical vapor cleaning (CVC) is an emerging technology which has been used to remove transition metal contamination from wafer surfaces. CVC is a gas phase/surface reaction which does not incorporate any wet steps nor condensation of reagents onto the wafer surface. In previous work, we reported the effective removal of trace iron and copper from native oxide surfaces using 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (HFAC) and other chelating or coordination compounds. In general, surface metal contaminants form volatile reaction products with these CVC reagents at relatively low temperatures (