Composition and method for removing photoresist and/or resist residue using supercritical fluids

Abstract

A method of removing photoresist and / or resist residue from a substrate includes exposing the substrate to a supercritical fluid in combination with a co-solvent mixture comprising an organic solvent and an oxidizer. In one embodiment, the supercritical fluid is supercritical carbon dioxide and the co-solvent mixture includes 1,2-Butylene Carbonate, Dimethyl Sulfoxide and hydrogen peroxide. If desired, supercritical carbon dioxide in combination with a second co-solvent mixture may be subsequently applied to the substrate to rinse and dry the substrate. In one embodiment, the second co-solvent mixture includes isopropyl alcohol.

Description

[0001] The present invention relates to supercritical fluids and, in particularly, to compositions and methods using supercritical fluids to remove photoresist and / or resist residues and associated materials from semiconductor substrates.BACKGROUND OF THE DISCLOSURE[0002] During the process of fabricating semiconductor integrated circuits, organic photoresist material may be applied to a semiconductor substrate as a precursor to formation of features on the substrate using photolithography techniques. Often additional coatings, for example an anti-reflective coating known in the industry as BARC [Back Antireflective Coating], are also applied to the substrate to enhance the lithography process.[0003] Once lithography is completed, the resist, BARC and other coatings used for the lithography steps must be removed from the substrate. A common technique for photoresist removal involves placing the substrate in an asher and burning the resist and associated coatings using a gaseous plas...

AI Technical Summary

Problems solved by technology

While the high temperature in the plasma process chamber oxidizes the photoresist and removes it, the plasma etch process leaves post-ash residues--undesirable byproducts from the reaction of the plasma gases, reactant species and the photoresist.

Moreover, the plasma etch procedure for resist removal is less desirable for substrates having low dielectric constant (or "low-k") films as insulating layers.

Nevertheless, the industry lacks a first-rate method of removing photoresist and / or resist residue from high aspect ratio openings such as submicron grooves, narrow crevices etc. without damaging the structure being produced.

This not only speeds up the wafer processing but also results in a decreased consumption of solvents and / or water used in cleaning, rinsing and drying.

Until now, however, the use of scCO.sub.2 in photoresist removal processes has not been successfully achieved.

This lack of success is due to the fact that scCO.sub.2 itself is a very poor solvent for polar residues such as resist and / or resist residues found on wafer surfaces.

Many of these processes are not cost effective for commercial use in that they require extended processing durations overly high energy costs, or use of prohibitively large quantities of process chemicals.

Others expose substrates to temperatures and / or pressures and / or chemical environments that can degrade the electrical performance of the integrated circuits manufactured using the substrates.

Others may even result in damage to the process equipment, such as amine stress corrosion cracking of the pressure vessel which can occur when amines are used in the presence of supercritical CO.sub.2.

Still others are simply ineffective at removing photoresist and / or resist residue.

In addition, the zero dipole moment of CO.sub.2 ensures that it is a poor solvent for polar substances until substantially higher operating pressures (more than 4 times its critical pressure) are used.

At those high pressures, the solvating ability of the scCO.sub.2 alone is so high that it will begin dissolving parts of the semiconductor device structure along with the resist and / or resist residue and loses its selective cleaning ability.

Normally concentrated solutions of hydrogen peroxide and water are handled carefully as the peroxide is a strong oxidizer and could pose a hazard.

In that case there is a finite shelf and / or bath life of the stripper and additional costs are involved in the disposal of unused stripper mix.

Without complete co-solvent penetration, residue removal from the bottom and the sidewalls of high aspect ratio structures is not possible.

A 100% cross-linked photoresist structure improves the intended performance of the photoresist but makes the photoresist very difficult to remove.

The hard crust dissolves at a much slower rate than the underlying photoresist and therefore, implanted photoresists are considered some of the most challenging resists to remove.

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