On-wafer spectrofluorometric method for determination of relative quantum yields of photoacid generation in chemically amplified resists.

Chemically amplified resists (CARs) that employ acid catalysts are widely used throughout the semiconductor industry due to the need for high throughput in the lithography process. The quantum yield of the particular photoacid generator (PAG) used to generate a given acid ultimately limits the photospeed of the CAR. Determination of quantum yields of photoacid generation is therefore an important component of resist design. We report the development of an on-wafer spectrofluorometric technique for this purpose. This technique is based on one first reported by Feke et al. (J. Vac. Sci. Technol. 2000, B18, 136- 139), which involves doping the resist formulations containing the candidate PAGs with a fluorescent pH indicator dye, coating one wafer per PAG, patterning the wafers with a dose ramp, and spectroscopically imaging the wafers. The response curve of each PAG is spatially and spectrally encoded in the fluorescence images of each wafer. We investigate the efficacy of coumarin 6, a dye that was introduced as an acid sensor by Pohlers et al. (Chem. Mater. 1997, 9, 3222-3230) for this application. We further apply this technique to the determination of the quantum yield of photoacid generation of four candidate PAGs for prototype 193-nm CARs. This technique is convenient, fast, robust, and nondestructive.

Laser flash photolysis of diphenylsulfonyldiazomethane: detection of the sulfene and a sulfene-pyridine ylide

The photochemistry of diphenylsulfonyldiazomethane (DSD) was studied by means of nanosecond laser flash photolysis. The photochemical behavior of this molecule upon UV irradiation is characterized by sulfene formation, presumed to arise via Wolff rearrangement of a carbene. We were able to detect the sulfene and the sulfene ylide formed upon sulfene trapping by pyridine. Sulfene quenching by nucleophiles was also examined.

Laser flash photolysis of 2-diazo-1,3-diphenyl-1,3-propanedione: An unusual long-lived triplet as a reaction intermediate

Laser flash photolysis of 2-diazo-1,3-diphenyl-1,3-propanedione (DBD) is presumed to involve a short-lived carbene, followed by Wolff rearrangement to a long-lived ketene. We have detected ketene ylides following photolysis of DBD in the presence of amines but not with pyridine. The triplet state of DBD lives several microseconds, an unusual observation for a diazo compound; however, the triplet is not a ketene precursor, which must result from excited singlet state fragmentation of DBD.