Erik N. Hoggan

Spin coating and photolithography using liquid and supercritical carbon dioxide

We discuss a new dry lithographic process using only carbon dioxide (CO2) as a solvent. Novel CO2 soluble photoresists were synthesized based on random copolymers of poly(1,1-dihydroperfluorooctyl)methacrylate 2-tetrahyrdopyranyl methacrylate. Photoresist spin casting, development, and stripping were all carried out in either liquid or supercritical CO2. We investigate such parameters as resist sensitivity, contrast, and resolution. The contrast of these resists has been evaluated using 248 nm exposures, and promising test images have been formed.

Designing photoresist systems for CO2-based microlithography

Carbon dioxide (CO2) based microlithography (dry microlithography) represents an immense opportunity for the semiconductor industry to keep pace with Moores Law while reducing its environmental impact. Currently, rinsing <130nm developed images with supercritical CO2 is the only method which can prevent image collapse at this resolution. In this article, we will discuss CO2s ability to improve lithographic performance as we demonstrate its potential to replace the most solvent intensive steps of the microlithography process; spin coating, developing, and stripping. During these steps, semiconductor manufacturers produce vast amounts of organic and aqueous waste, which are detrimental to our ecosystem. However, before CO2 can replace conventional solvents, photoresist systems must be designed and synthesized to be compatible with CO2. These photoresists must be soluble in liquid CO2 to insure that uniform thin-films can be produced by spin coating while maintaining characteristics of conventional resist systems such as low absorbance, high sensitivity, solubility contrast, good resolution, and etch resistance. Using our CO2 compatible resist system, we will show the ability of CO2 to spin coat uniform thin-films which (after exposing and PEB) can be developed using scCO2 to produce lithography features that may be stripped in CO2. Thus, revealing the enormous potential of CO2 to provide the microlithography industry an opportunity to escape its water and organic solvent dependence.

All CO 2 -Processed Fluoropolymer-Containing Photoresist Systems

Currently, the microlithography industry creates large amounts of organic and aqueous wastes in the production of semiconductors. Using carbon dioxide can possibly eliminate the majority of these waste solvents as well as eliminate the image collapse problems shown with aqueous base development. We will discuss the use of carbon dioxide to replace the most solvent intensive steps of the microlithography process, spin coating, developing, and stripping. However, before CO 2 can replace conventional solvents, photoresist systems must be designed and synthesized to be compatible with CO 2 . These photoresist systems must be soluble in liquid CO 2 to insure that thin-uniform coatings can be produced by spin coating while maintaining characteristics of conventional resist systems such as low absorbance, high sensitivity, solubility contrast, good resolution, and etch resistance. Using our CO 2 compatible resist system, we will demonstrate the ability of CO 2 to spin coat uniform thin-films which (after exposing and PEB) can be developed using scCO 2 to produce lithography features that may be stripped in CO 2 . Thus, revealing the enormous potential of CO 2 to provide the microlithography industry an opportunity to escape its water and organic solvent dependence as it moves toward 157nm lithography.

All CO2-processed 157-nm fluoropolymer-containing photoresist systems

We present our progress on implementing a completely carbon dioxide-processed 157nm photoresist system. While current processes rely on the use of large amounts or organic and aqueous solvents, our chemistry and equipment will allow both negative and positive-tone imaging using CO2 as a casting solvent, developer, and stripping solvent. The unique solubility characteristics of fluoropolymers in CO2 make it possible to use this cleaner and simpler approach with improved optical transparency at 157nm and excellent etch resistance. Also, the inherently low surface tension and viscosity and excellent wetting properties of liquid CO2 will allow us to generate defect-free thin films on large area wafers (300mm and larger). In addition, CO2-based development can virtually eliminate image collapse problems associated with aqueous-base development. Aside form performance issues, our process eliminates several waste streams from the semiconductor manufacturing process and replaces them with the more environmentally benign CO2-this reduction in complexity could allow the integration of multiple processes and provide an enormous savings to the industry.

All CO2-Processed 157-nm fluoropolymer-containing photoresist systems

We present our progress on implementing a completely carbon dioxide-processed 157nm photoresist system. While current processes rely on the use of large amounts or organic and aqueous solvents, our chemistry and equipment will allow both negative and positive-tone imaging using CO2 as a casting solvent, developer, and stripping solvent. The unique solubility characteristics of fluoropolymers in CO2 make it possible to use this cleaner and simpler approach with improved optical transparency at 157nm and excellent etch resistance. Also, the inherently low surface tension and viscosity and excellent wetting properties of liquid CO2 will allow us to generate defect-free thin films on large area wafers (300mm and larger). In addition, CO2-based development can virtually eliminate image collapse problems associated with aqueous-base development. Aside form performance issues, our process eliminates several waste streams from the semiconductor manufacturing process and replaces them with the more environmentally benign CO2-this reduction in complexity could allow the integration of multiple processes and provide an enormous savings to the industry.

All Co 2 -processed 157-nm fluoropolymer-containing photoresist systems

We present our progress on implementing a completely carbon dioxide-processed 157nm photoresist system. While current processes rely on the use of large amounts or organic and aqueous solvents, our chemistry and equipment will allow both negative and positive-tone imaging using CO2 as a casting solvent, developer, and stripping solvent. The unique solubility characteristics of fluoropolymers in CO2 make it possible to use this cleaner and simpler approach with improved optical transparency at 157nm and excellent etch resistance. Also, the inherently low surface tension and viscosity and excellent wetting properties of liquid CO2 will allow us to generate defect-free thin films on large area wafers (300mm and larger). In addition, CO2-based development can virtually eliminate image collapse problems associated with aqueous-base development. Aside form performance issues, our process eliminates several waste streams from the semiconductor manufacturing process and replaces them with the more environmentally benign CO2-this reduction in complexity could allow the integration of multiple processes and provide an enormous savings to the industry.