Dyed positive photoresist employing curcumin for notching control

• Published in: Journal of the Electrochemical Society 1989, Vol.136 (1), p.281-283
• Main Authors: RENSCHLER, C. L, LEMEN, E. K, RODRIQUEZ, J. L, STIEFELD, R. E
• Format: Article
• Language: English
• Subjects: 360601 - Other Materials- Preparation & Manufacture; 400500 - Photochemistry; ABSORPTION SPECTRA; ANTIREFLECTION COATINGS; Applied sciences; AROMATICS; CHEMISTRY; COATINGS; CURCUMIN; DYES; ELECTRIC CONDUCTIVITY; ELECTRICAL EQUIPMENT; ELECTRICAL PROPERTIES; Electronics; ETHERS; Exact sciences and technology; GLASS; HYDROXY COMPOUNDS; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; KETONES; MATERIALS SCIENCE; Microelectronic fabrication (materials and surfaces technology); ORGANIC COMPOUNDS; ORGANIC OXYGEN COMPOUNDS; PHENOLS; PHOTOCHEMISTRY; PHOTORESISTORS; PHYSICAL PROPERTIES; POLYPHENOLS; RESISTORS; SEMICONDUCTOR DEVICES; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; SOLAR ABSORBERS; SOLAR EQUIPMENT; SPECTRA; SPECTRALLY SELECTIVE SURFACES; SURFACES
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1.2096604

A variety of dyes have been proposed as absorbers for photoresists. The nonbleachable absorbance incorporated in this way can result in a reduction in standing waves and/or reflective notching (nonuniform linewidths due to reflections off the substrate). In addition, it can provide increased visual contrast at the patterned resist inspection stage. A variation on the visual contrast improvement involves the use of a dye which fluoresces, allowing for more precise resist metrology. The deposition and growth processes used here result in large oxide and polycrystalline silicon steps with high aspect ratios. Processes such as LOCOS which allow less severe topography, are inherently radiation soft and cannot be used on our fabrication process. The resulting steep sidewalls make metal coverage and etch significantly more difficult. Thus, the glass layer which isolates metal conductors from oxide steps is smoothed with either a thermal reflow or a plasma etch of a partially planarized coating to reduce the aspect ratio of the step. This results in metal coverage with a 45{degrees} angle at each step, which causes severe notching. This paper reports on an attempt to develop a resist which would eliminate this notching problem. Although the addition of unbleachable dye to photoresist for the control of notching is well established, most of the dyes used have one or more serious shortcomings, such as a poor match of the absorption spectrum with the exposure spectrum or low solubility in resist. Severe notching requires the use of a resist dye with optimized physical and spectroscopic properties to allow high optical absorbance to be achieved without the onset of other problems such as particulate formation or changes in thermal properties.