Methods for plasma depositing polymers comprising cyclic siloxanes and related compositions and articles
Methods for plasma depositing polymers comprising cyclic siloxanes and related articles and compositions are generally provided. In some embodiments, the methods comprise flowing a precursor gas in proximity to a substrate within a PECVD reactor, wherein the precursor gas comprises an initiator and at least one monomer comprising a cyclic siloxane and at least two vinyl groups, and depositing a polymer formed from the at least one monomer on the substrate.
1. A method of fabricating a polymer via a plasma-enhanced chemical vapor deposition (PECVD) process, comprising the steps of:
(i) flowing a precursor gas in proximity to a substrate within a reaction volume of a PECVD reactor comprising an active electrode and a ground electrode, wherein the precursor gas comprises an initiator and at least one monomer comprising a cyclic siloxane and at least two vinyl groups; and
(ii) depositing the polymer in the presence of a plasma, wherein the deposited polymer is formed from polymerization of the at least one monomer on at least a portion of the substrate and, wherein the deposited polymer comprises one or more cyclic siloxane groups;
wherein the initiator is present at a partial pressure of less than or equal to 10 mTorr during step (ii);
wherein the at least one monomer is present at a partial pressure of less than or equal to 10 mTorr during step (ii);
wherein the plasma throughout the reaction volume is substantially uniform; and
wherein the percentage of the one or more cyclic siloxane groups in the deposited polymer in step (ii) is greater than or equal to about 60%.
2. The method of claim 1 , wherein the at least one monomer comprises at least three vinyl groups.
3. The method of claim 2 , wherein the at least one monomer comprises one or more of trivinyltrimethylcyclotrisiloxane, tetravinyltetramethylcyclotetrasiloxane, or trivinylpentamethyltetrasiloxane.
4. The method of claim 1 , wherein the percentage of the cyclic siloxane groups in the polymer is greater than or equal to about 65%.
5. The method of claim 1 , wherein the deposited polymer is a film that has a thickness of greater than or equal to 50 nm and less than or equal to 10 μm.
6. The method of claim 1 , wherein the deposited polymer is a film that has a dielectric constant of less than or equal to 3.
7. The method of claim 1 , wherein the initiator comprises a peroxide.
8. The method of claim 7 , wherein the peroxide is tert-butyl peroxide or is tert-amyl peroxide.
9. The method of claim 1 , wherein the substrate comprises one or more of gold, copper, solder, solder flux, indium phosphide, gallium sulfide, gallium nitride, and silicon.
10. The method of claim 1 , wherein the active electrode is located at a distance to the ground electrode wherein the distance is greater than or equal to 1 cm.
11. The method of claim 1 , wherein the plasma uniformity exhibits a ratio of the standard deviation of a power density of the plasma over the reaction volume of less than or equal to 25%.
12. The method of claim 1 , wherein the ratio of the partial pressure of the initiator to the partial pressure of the at least one monomer is less than or equal to 2 during step (ii).
13. The method of claim 1 , wherein the partial pressures of the initiator and the at least one monomer are each independently less than or equal to 10 mTorr during step (ii).
14. The method of claim 1 , wherein the total pressure of the PECVD reactor is less than or equal to 75 mTorr during step (ii).
15. The method of claim 1 , wherein the deposited polymer exhibits no fungal growth, as measured by ASTM G-21.
16. The method of claim 1 , wherein the deposited polymer has an insulation resistance of greater than or equal to 1.5*10 12 ohms and less than or equal to 10 14 ohms.
17. The method of claim 1 , wherein the deposited polymer exhibits a dielectric breakdown voltage of greater than or equal to 5,000 V/mil.
18. The method of claim 1 , wherein the adhesion strength of the deposited polymer after undergoing elongation of up to 5% is greater than or equal to 75% of the initial adhesion strength.
19. The method of claim 1 , wherein the deposited polymer on at least a portion of the substrate reduces or prevents corrosion of the substrate, as compared to the substrate prior to depositing the polymer thereon, as measured using a salt fog test, conducted in accordance with Method 509.5 5 in MIL-STD-810G.