3. stability and optimum storage condition

general information - 3. stability & storage condition

Stability and optimum storage conditions

PMMA and copolymer e-beam resists are not light-sensitive in the visible wavelength range (no yellow light required) and react considerably less sensitive than novolac-based resists to temperature changes. They age only slowly; observed age-related changes mainly concern a gradual thickening of the resist which however does not compromise product quality. In this case, only the film thickness will increase which can easily be corrected during coating.

Novolac-based e-beam resists in contrast are light-sensitive like photoresists, they react to light exposure or temperature changes and age faster during storage. These resists are therefore filled in light-protected amber bottles, stored in a cool place and may only be processed under yellow light (λ > 500 nm). The date of expiry and the recommended storage temperature are indicated on the product label of each bottle. If these temperatures are maintained, resists in unopened bottles are stable until expiry date (which is in general 2 years after production), at least however for 6 month after date of sale. Brief temperatures deviations do not influence on general product properties.

If resists are to be used later than 6 month after date of sale or to be processed within a very small process window, storage at 4 – 8 °C is recommended. Exceptions are only resists with recommended storage temperatures between 14 – 20 °C. These resists should not be stored colder.

Novolac-based e-beam resists stored for several years are outdated and may only be used with considerable restrictions. This also applies to resists stored at too high temperatures and to highly diluted resists which age faster than normal.

Wastewater treatment

Up to 90 % of the organic material can be removed from developer wastes if the pH of used aqueous-alkaline developer and remover solutions is adjusted to pH 9 to 10 by addition of acids, followed by subsequent separation of the precipitate. Prior to waste disposal, filtered solutions have to be adjusted to pH 6.5 – 8.0. Solid wastes may be disposed of at sanitary landfills or by incineration in officially authorized plants. Collected resist and solvent wastes have to be disposed of in approved incinerators.

Safety instructions

Resists, thinner and remover contain organic solvents. Adequate ventilation in the working area is thus mandatory. Development solutions are caustic alkaline liquids which may irritate the skin. Avoid direct contact with products and their vapours (wear safety goggles and gloves).

EG-safety data sheets of our products may be downloaded from www.allresist.de/products or be requested at info@allresist.de.