Semiconductor Manufacturing – Plasma Process
The plasma process is one of the most hostile for elastomers, especially those vulnerable to chemicals and/or close to the substrate or the wafer. The most hostile plasma processes for elastomers include oxygen resist strip and radical based plasmas (such as remote NF3) and chamber cleans using remote plasma sources (RPS).
Every seal, especially one in critical locations is going to deteriorate/decay over a certain period of time. These elastomers must perform at high temperatures (up to +250°C) and continue to maintain low off-gassing and low particle origination to eliminate contaminating the manufacturing process. In several instances, under exceptionally corrosive surrounding of high temperatures and plasma gasses, around 6-8 weeks is frequently considered a long service life for a seal. No seal material is enhanced for all chemicals or relevant to every tool placement and/or product category. Adequate selection of our suggested/recommended products/materials will provide the following benefits:
- Low erosion ratio
- Reduced footprint on appliance efficiency and electrical yield
- Decreased Cost of Consumables (CoC)
- Cost optimised guidance conditional on the application
- Where critical, moderate/low particle discharge ratios
- Where critical, low trace metal level
Plasma Process Applications
Seals can be used in a diversity of sealing installations, including door seals, centering rings for flanges, exhaust valves, window seals, valve seals, chamber lid seals, also as cushioning for wafer transport. Each of these installations have various demands, therefore it’s important to be aware of and fully understand the accurate requirements for each application. Having that understanding can help maximise service life and enhance the best possible elastomer productivity.
Material Requirements in the Plasma Process – Perfluoroelastomers
Performance demands may vary depending on the elastomer placement. In a location near the plasma source, close to the wafer, in the plasma gas, numerous ions are present. This makes it an aggressive environment to the seal surface. Therefore, in such locations, it is recommended to use a filled elastomer. Unfilled elastomers can deteriorate rapidly and cause leaks.
Particles such as radicals are also found in plasma stream, however, are deemed less corrosive. They can still damage the seal surface, but at a steadier rate than ions. Mainly elastomers that are placed further from the plasma source, or the chamber zone under the wafer, are vulnerable to these surroundings. Due to lower surface destruction, elastomers in this zone can be non-filled or lightly filled.
In the exhaust pipes, cleanliness of a seal is not a big concern. This is because elastomer particles originated are swept out of the system with the exhaust gas. With time, of course, the material will build upon the chamber walls. When that happens, the chamber will demand a cleaning procedure, generally a hostile plasma gas to clear out the deposits.
The below table points out compatible and recommended elastomer material grades for a given application. Primary grades are adjusted in the direction of critical process/tool placements.
|PROCESS/APPLICATION||TEMP. RANGE||PROCESS MEDIA||PRIMARY MATERIALS||COMPATIBLE MATERIALS|
|PECVD/HPDCVD||25°C – 300°C
(77°F – 572°F)
|SiH4, N2, NH2, N2O, NO, Organosilanes/siloxanes, O2, CF4, C2F6, C3F8, SF6, SiF4, NF3||MBMS1108, MBMS1040||MBMS0825, MBMS0729|
|Resist Strip / Ash||25°C – 200°C
(77°F – 392°F)
|O2, CF4, SF6, CHF3, NH3, H2, H2O, NO, N2O, Forming Gas||MBMS1040, MBMS0825||MBMS0245, MBMS0729|
|Dielectric Etch||25°C – 200°C
(77°F – 392°F)
|H2, O2, CO, CO2, NO, NO2, N2O, CS2, COS, CF4, CH4, CHF3, C2F4, C2F6, C3F8, C4F6, C4F10, C5F8, C6F6, SF6||MBMS1040, MBMS1108||MBMS0825, MBMS0245, MBMS0729|
|Conductor Etch||25°C – 200°C
(77°F – 392°F)
|CF4, CHF3, C2F6, C3F8, SF6, HBr, BCl3, SiCl4, CCl4, Cl2, CCl2F2, O2, CO, NO, N2O, NF3||MBMS0825, MBMS1040||MBMS0245, MBMS0729, MBMS1119|
E & OE.