Method and apparatus for microwave treatment of dielectric films
An apparatus for thermal treatment of dielectric films on substrates includes: a microwave applicator cavity and microwave power source; a workpiece to be heated in the cavity, having a porous coating on a selected substrate; and, an apparatus for introducing a controlled amount of a polar species into the porous coating immediately before heating by the microwave power. The interaction of the polar species with the microwaves enhances the efficiency of the process, to shorten process time and reduce thermal budget. A related method includes: depositing a porous film on a substrate; soft baking the film to a selected state of dryness; introducing a controlled amount of a polar species into the soft baked film; and, applying microwave energy to heat the film via interaction with the polar species.
1. An apparatus for thermal treatment of dielectric films on substrates comprising:
a pretreatment chamber for receiving a soft-baked workpiece, the workpiece comprising a porous coating on a selected substrate, and holding the workpiece in a controlled vapor pressure of a selected polar solvent for a sufficient time to allow a selected amount of the solvent to be absorbed by the porous coating;
a microwave applicator cavity for applying microwave power to the workpiece so that a portion of said microwave power interacts with the absorbed solvent; and
a microwave power source to supply power to the applicator cavity, wherein the pretreatment chamber contains a reservoir of the polar solvent further containing a dissolved species so that a selected partial pressure of said polar solvent is maintained in a headspace above the reservoir.
2. The apparatus of claim 1 wherein the selected substrate comprises a semiconductor wafer and the porous coating is selected from the group consisting of: low-k dielectric films, organo-silicate glass films, and soft-baked polymeric films.
3. The apparatus of claim 1 wherein the polar solvent is selected from the group consisting of: water, methanol, ethanol, isopropanol, acetic acid, acetone, n-propanol, n-butanol, formic acid, propylene carbonate, ethyl acetate, dimethyl sulfoxide, acetonitrile, dimethylformamide, tetrahydrofuran, and dichloromethane.
4. The apparatus of claim 1 wherein the pretreatment chamber comprises a humidistat.
5. The apparatus of claim 1 , wherein:
the polar solvent is water;
the dissolved species comprises one or more compounds selected from the group consisting of: acids and salts; and
the dissolved species is selected to maintain a relative humidity from about 3.2% to about 100% in the headspace.
6. The apparatus of claim 1 , wherein the pretreatment chamber and the applicator cavity are different chambers, and further comprising:
a material handler to place the soft-baked workpiece into the pretreatment chamber, remove a pretreated workpiece from the pretreatment chamber, and place the pretreated workpiece into the applicator cavity for microwave processing.
7. The apparatus of claim 1 , further comprising a quartz bell jar disposed in the microwave applicator cavity.