Refractory compounds such as Trimethylsilanol (TMS) and other organic compounds such as propylene glycol methyl ether acetate (PGMEA) used in the photolithography area of microelectronic cleanrooms have irreversible dramatic impact on optical lenses used on photolithography tools. There is a need for real-time, continuous measurements of organic contaminants in representative cleanroom environment especially in lithography zone. Such information is essential to properly evaluate the impact of organic contamination on optical lenses. In this study, a Proton-Transfer Reaction-Time-of-Flight Mass spectrometer (PTR-TOF-MS) was applied for real-time and continuous monitoring of fugitive organic contamination induced by the fabrication process. Three types of measurements were carried out using the PTR-TOF-MS in order to detect the volatile organic compounds (VOCs) next to the tools in the photolithography area and at the upstream and downstream of chemical filters used to purge the air in the cleanroom environment. A validation and verification of the results obtained with PTR-TOF-MS was performed by comparing these results with those obtained with an off-line technique that is Automated Thermal Desorber – Gas Chromatography – Mass Spectrometry (ATD-GC-MS) used as a reference analytical method. The emerged results from the PTR-TOF-MS analysis exhibited the temporal variation of the VOCs levels in the cleanroom environment during the fabrication process. While comparing the results emerging from the two techniques, a good agreement was found between the results obtained with PTR-TOF-MS and those obtained with ATD-GC-MS for the PGMEA, toluene and xylene. Regarding TMS, a significant difference was observed ascribed to the technical performance of both instruments.
With device size reduction, variability induced by local micro roughness is becoming less and less negligible in terms of
statistical control of critical dimensions (CD). We applied a recent approach developed at Fresnel Institute for the
determination of micro roughness on periodic structures through optical far field characterization using an angle resolved
scatterometer. Structure periodicity affects the diffraction orders, while roughness signature is mainly found between
diffraction orders. Theoretical simulation was performed using two in-house computer codes based on differential
method and on first order approximation. We will review the theoretical approach and show roughness data derived from
measurement on glass gratings as well as poly silicon gate type structures.
In the field of microelectronic industry, periodic structures are produced with spatial dimensions that can be less than
100 nm. Because of the material and process effects, these structures will most likely present some additional roughness.
The optical far field characterization of these structures usually allows to deduce the shape parameters of the periodic
structure. Measurements are performed thanks to an ellipsometric apparatus, associated with modelling and inversion
algorithms. In this configuration the technique is called "scatterometry". This method does not permit to directly extract
roughness parameters. This paper aims at describing how model and experimental tools can be used to characterize the
roughness of gratings. The study needs a complete three-dimensional electromagnetic modelling of the structure but the
calculations are very time consuming. Here, different theoretical models are associated in order to reduce the calculation
time: rigorous numerical differential theory and Born approximation theory. The exact numerical model allows to treat
the periodic part of the structure while the roughness is viewed as a perturbation and treated using a first order
approximation. From an experimental point of view, the information on the periodic part of the structure lies in the
diffraction orders, while the roughness signature is mainly found between diffraction orders. Practically, this model
could be used in the semiconductor industry for a detailed roughness characterization, based on an optical measurement
using the same test structures used for scatterometry.
A comparison was made between rapid-thermal processing and furnace processing with respect to gate oxidation, polysilicon sidewall oxidation, and junction activation anneal. NMOS and PMOS structures with N+ polysilicon gates, 6.5 nm gate oxide, and 70 nm source/drain junction depths were processed in parallel, using one-mask FET test structures to define MOSFETs with channel lengths down to 0.18 micrometers . Good NMOS device characteristics and low junction leakage were observed for all experimental combinations. Rapid-thermal and furnace oxidation exhibited similar gate-oxide breakdown characteristics.
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