Clean oven, ovens with HEPA filter for annealing under clean conditions.
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Koyo Thermo Systems developed a special version of the clean oven CLH for the baking of non-photosensitive polyimide. Several recipes can be stored in the controller.
The CLH oven is a convection oven. The gas passes a heat resistive HEPA filter and is heated by a special sheath heater and then introduced to the oven chamber through the punched backside. The gas passes the chamber in a laminar flow and is exhausted by the punched front door. The blower in the lower part of the oven sucks in the gas from the door and mixes it with fresh gas from outside. The gas mixture passes a heat exchanger in order to cool it down and part of the gas is exhausted and led to a cool trap. The rest gas goes through the HEPA filter and is then heated again.
For good polyimide performance a very good temperature uniformity, a low oxygen content and low particle figures are most important. Using the procedure described above, the gas in the chamber stays rather clean (class 100). The temperature uniformity is ± 5°C. The oxygen level can be lowered below 20ppm by nitrogen purge and measured optionally by a zirconia oxygen sensor. This guarantees excellent process results for non-photosensitive polyimide.
Ramp rates of >7°C / Min. for heating and cool down rates of >4°C / Min. can be achieved. Total process time for a standard polyimide is around 3.5h. Most customers put four metallic cassettes with 25 wafers each in the furnace for one run.
For furnace control we use in Europe mainly program controller from the company of Stange, which enable beside temperature control also gas flow control via MFCs (mass flow controller) and allows integration of gas sensors, e.g. for oxygen measurement. As an option, data coupling with a PC can be offered, which allows long term data storage as well as statistical process control SPC, recipe management and process visualization.
All parts can be accessed easily for maintenance and cleaning. Baking photosensitive polyimide in this type of oven however, you will get deposition of solid by-products and the maintenance work will increase a lot. Therefore we recommend this furnace only for non-photosensitive material. For photosensitive material we recommend our maintenance free vertical furnaces, that have been developed especially for the baking of photosensitive polyimide.
|Clean Oven CLH|
Please find more information about the polyimide bake process and other ovens from Koyo Thermo Systems, following these links.
Koyo Thermo Systems and Crystec will be pleased to engineer a cost effective system to satisfy your most demanding and exacting requirements.