Quantitative Secondary Ion Mass Spectrometry Analysis of Carbon and Fluorine Impurities on Silicon Wafers Stored in Polymer Carrier Cases

Abstract

We have investigated the carbon and fluoride contaminants on silicon wafers during their storage in quartz-glass boxes equipped with carrier cases made of either polypropylene (PP), polybutylene-terephthalate (PBT), or perfluoroalkoxy polymer (PFA). The adsorbed organic contaminants on the wafer surfaces were identified by time-of-flight secondary-ion mass spectrometry (TOF-SIMS). The concentrations of contaminants on the wafer surface have been measured as a function of wafer storage positions as well as carrier case storage time. For quantitative analyses, secondary-ion mass spectrometry (SIMS) combined with the encapsulation method was employed, and carbon ( 12 C − ) and fluorine ( 19 F − ) ions were detected. It has been found that the amount of adsorbed contaminants on the surface of silicon wafers depend on both the wafer storage conditions and the carrier case materials.

Critical interface: Poly-silicon to tunneling SiO2 for passivated contact performance

“…When comparing surface spectra (figure 7) of stored-and-treated versus stored-and-untreated tunneling SiO2, we find polypropyelene fragmentations 9 at atomic mass of ~288.3 as a result of the container in which we store our samples. These adhere to the SiO2 layer to create the localized weak attachment points for the a-Si:H. Environmental conditions such as containment and latent chemistry, even in a cleanroom, are well known to contaminate surfaces 10,11 .…”

Atomic Spectrometry Update. Industrial analysis: metals, chemicals and advanced materials

“…A study on the use of quantitative SIMS for the analysis of carbon and fluorine impurities on Si wafers stored in quartz-glass boxes equipped with polymer carrier cases (polypropylene, polybutylene terephthalate or perfluoroalkoxy polymer) has been undertaken. 216 The adsorbed organic contaminants were identified by ToF-SIMS. The concentrations of contaminants on the wafer surface were measured as a function of wafer storage positions as well as carrier case storage time.…”

Failure Mechanism by Organic Contaminants in Si Device Fabrication

“…5 They have many oxygen atoms and planar aromatic rings and, thus, induce strong hydrogen bonding with hydroxyl groups or silicon hydrides on the wafer surface along with additional van der Waals interactions with silicon atoms. Thus far, studies of a few organic contaminants on silicon wafers have been carried out by identifying contaminants by thermal desorption-gas chromatography/mass spectroscopy (TD-GC/MS), 6,7 time of flight-secondary ion mass spectroscopy (TOF-SIMS), 8 X-ray photoelectron spectroscopy (XPS), 9 and Fourier transform-infrared spectroscopy (FT-IR). 10 The phenomenon has been explained by postulated degradation mechanisms but the causes of the device failure due to the organic contamination have not been experimentally studied.…”