A direct positive patterning of PPA layers is possible by electron bombardment. Similar to the irradiation of normally used e-beam resists like e.g. CSAR 62 or PMMA, the electron beam causes a fragmentation of the polymer chains.
Report on the two layer system, respectively lift-off: AR P-617 (250nm) with PPA (30nm), development followed by vapor coating of Al (40nm).
We now succeeded in finding a remarkable solution for high-layer e-beam structuring. The negative resist CAR 44 (AR-N 4400-10) was coated to yield a layer with a height of 9.5 μm, dried, and irradiated.
A new application field for Atlas 46 is electron beam lithography, as experiments with a thin Atlas resist layer patterned by e-beam lithography demonstrated. At a layer thickness of 450 nm, 200 nm lines were written into this layer. The sensitivity was 70 μC/cm² at an acceleration voltage of 100 kV.
In the final stage of the Eurostar PPA-Litho project which was aimed to develop the resist Phoenix, we achieved to generate far more stable PPA polymers by optimizing the synthesis procedure. Pure polyphthalaldehydes which were subjected to a “stress test” for 14 days at 37 °C showed no decomposition. These resists can thus be shipped without cooling; this however only applies to pure PPA polymers.
Fluorescence is the spontaneous emission of light briefly after a substance is excited by electronic transitions. The emitted light has usually less energy than the previously absorbed light.
The DESIRE process can also be used for electron beam lithography even though certain differences exist between photo and e-beam lithography. Structures are written into the resist layer by means of electrons.
Semi-precious stones like sapphire or garnet increasingly gain in importance as substrates for semiconductor industry. Even though these materials have insulating properties, a patterning with electron beam lithography is nevertheless possible with the help of Electra.
Novolac-based e-beam resists have other surface properties than e.g. CSAR 62, PMMA, or HSQ resists. Due to a higher solvent content of the conductive resist as for example is the case with SX AR-PC 5000/90.2, these novolac-resists are already moderately attacked.
The measured conductivity of resist layers is strongly influenced not only by the temperature but also directly dependent on the air humidity. After a softbake, the now almost anhydrous layer gradually takes up water at room temperature from the ambient air due to the slightly hygroscopic properties of the polymer.