Photo Resist Removal
Photoresist removal is a chemical etching process for stripping the resist layer on the silicon wafer. It is carried out under low pressure plasma in an O2 plasma where the O2 radicals react with the organic layer and burn the photoresist to ash. The key objective for photoresist removal process is to totally removal of organic layer on the wafer. It is also important that when the resist is completely removed, the layer exposed can withstand the plasma condition. Controlling the chemistry and parameter are critical to any photoresist removal process especially when the underlying layer is sensitive to plasma damages. Direct plasma can cause damage through ion bombardment at the wafer surface and electric fields that develops on the surface due to sheath formation can affect sensitive structures such as transistor gates. Alpha Plasma advanced microwave technology can offer photoresist removal with unprecedent precision and control to avoid wafer damages.
Following photoresist removal and patterning, descum is another gentle photoresist removal process carried out under lower temperature conditions to remove thin film/ scum after pattern development. Plasma descum process itself demands stringent control in order not to affect or alter the pattern quality after development. Microwave plasma has proven to be a better and effective way to descum the leftovers within trenches. Maintaining a controlled process enables etching uniformity and reduce adhesion properties in lift-off technique on subsequent process. Descum step is also important to improve the side wall profile of the masking resist. For challenging descum processes, we have dedicated systems with single layer process in either manual or automatic wafer handling mode up to 300 mm wafers. More precise control of the descum process is possible here to providing good uniformity and desirable etching rate on demanding descum applications.
SU8 RESIST REMOVAL
SU8 is commonly used as a resin for making high aspect ratio in MEMS device structures. Unfortunately, the properties of cross-linked SU8 make the resist removal difficult as this resist is chemically very stable. Highly selective etching process is need in order to remove SU8 successfully without damaging other micro structures. Dry microwave plasma treatment generates high density radicals to obtain high chemical etching on SU8 photoresist removal rate without damage by ions attacking onto the sample. Temperature control are critical in the removal of SU8 resist and sacrificial layers. If the temperature is too high, SU8 resist are hard and difficult to remove. Therefore, microwave technology offers useful advantages to SU8 removal applications. Alpha Plasma tools are equipped with precision temperature control to assist our customers to create tomorrow new technology.
Plasma surface activation has also proven to be able to increase the surface energy, hence, to improve adhesion characteristics. However, in the semiconductor production, high performance polymers are used because of their minimal thermal expansion, minimal out-gassing under vacuum, good wear resistance including chemical resistance to acids, alkalis, etc. Plasma polyer removal is also commonly used in the removal of polymeric photoresists in IC fabrication. The polymer removal rate is highly influence by the etching gas used. Radicals generated by microwave frequency removes the polyer even from deep and narrow trenches.
We provide all kind of plasma solutions in most of the Asian countries including Malaysia.