Method for determining solvent permeability of films

Abstract

A method is disclosed to measure the permeability of films or coatings towards solvents (e.g. water). First a substrate comprising an absorption or container layer is provided, preferably the material is a porous material. To study water permeability, the porous material is hydrophilic or is made hydrophilic by means of e.g. an anneal process. To study the permeability of the film or coating, the coating is deposited on top of the porous material. The substrate comprising the film or coating on top of the absorption or container layer is then brought into a pressurizable chamber subsequently filled with the gaseous substance of the solvent (e.g. water vapor). By increasing/decreasing the vapor pressure in the chamber between zero and the equilibrium vapor pressure of the solvent used, the permeability (penetration) of solvent through the film or coating can be determined. The amount of solvent that can penetrate through the film or coating can be measured by means of ellipsometry, mass spectrometry, etc. The method of preferred embodiments of the invention can be applied to predict the water permeability of photosensitive coatings used in photolithography in semiconductor processing, which is especially important in case of immersion lithography.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments are illustrated in referenced Figures of the drawings. It is intended that the embodiments and Figures disclosed herein are to be considered illustrative rather than restrictive.

FIG. 1A shows a permeability measurement set-up according to the prior art used for membrane systems to have an indication of how fast water diffuses through the membrane;

FIG. 1B shows a permeability measurement according to preferred embodiments to determine the permeability of films or top coatings;

FIG. 2A illustrates the change of pressure as a function of time in a pressurizable chamber according to a preferred embodiment.

FIG. 2B shows the change in absorptive mass (solvent) as a function of time for a preferred embodiment.

FIG. 3A illustrates absorption and desorption graphs for NanoClustered Silica (NCS).

FIG. 3B shows the desorption characteristics of FIG. 3A in more detail and with added ellipsometric values.

Claims

1. A method to determine a permeability of a film towards a solvent, the method comprising: providing a substrate, a container layer, and a film, wherein the container layer is situated between the substrate and a film;transferring the substrate, the container layer, and the film into a pressurizable chamber; thereafterdecreasing a pressure in the pressurizable chamber; thereafterfilling the pressurizable chamber with a gaseous solvent; thereaftergradually increasing the pressure in the pressurizable chamber up to a vapor pressure of the solvent, such that the solvent penetrates the film and absorbs into the container layer;determining a first value of a parameter indicative of an amount of solvent absorbed in the container layer; thereafterdecreasing the pressure in the pressurizable chamber such that an amount of the solvent absorbed in the container layer diffuses back through the film;determining a second value of the parameter indicative of the amount of solvent absorbed in the container layer; and thereafterdetermining the amount of solvent that diffused back through the film from the first value and the second value, wherein the amount of solvent diffused through the film is indicative of a permeability of the film towards the solvent.

2. The method of claim 1, wherein decreasing the pressure in the pressurizable chamber is done to a level less than or equal to 10−2 torr.

3. The method of claim 1, wherein decreasing the pressure in the pressurizable chamber is done to a level less than or equal to 10−3 torr.

4. The method of claim 1, wherein the method further comprises activating the container layer, whereby an absorption of the container layer towards the solvent is increased.

5. The method of claim 1, wherein the container layer is a porous material.

6. The method of claim 1, wherein the solvent and the container layer are both hydrophilic.

7. The method of claim 1, wherein the solvent and the container layer are both hydrophobic.

8. The method of claim 1, wherein determining an amount of solvent diffused through the film from the first value and the second value is performed using ellipsometric measurements.

9. The method of claim 1, wherein determining an amount of solvent diffused through the film from the first value and the second value is performed using mass spectrometric measurements.

10. An immersion lithography method, the method comprising: conducting the method of claim 1, wherein the method of claim 1 is conducted as part of an immersion lithography method.

11. A system for determining a permeability of a film towards a solvent using a substrate, a container layer, and a film, wherein the container layer is situated between the substrate and the film in between the substrate and a film, the system comprising: a pressurizable chamber configured for holding the substrate, the container layer, and the film;means for decreasing a pressure in the pressurizable chamber; means for filling the pressurizable chamber with a gaseous solvent;means for gradually increasing a pressure in the pressurizable chamber up to a vapor pressure of the solvent such that the solvent penetrates the film and absorbs into the container layer;means for determining a first value of a parameter indicative of an amount of solvent absorbed in the container layer;means for decreasing a pressure in the pressurizable chamber such that an amount of the solvent absorbed in the container layer diffuses back through the film;means for determining a second value of the parameter indicative of the amount of solvent absorbed in the container layer; andmeans for determining the amount of solvent diffused through the film from the first value and the second value, wherein the amount of solvent diffused through the film is indicative of a permeability of the film towards the solvent.