AZ 4562/AZ 4533 光刻胶
- 型号AZ 4500系列
AZ 4500系列光刻胶包括：AZ 4533、AZ4562 匀胶厚度约在3~6微米
AZ 4500 Series
This series of positive photoresists is intended for applications where coating thicknesses
above 3 µm are required. When using a standard photoresist at film thicknesses above 3
µm, the necessary exposure energy drastically increases. This is due to the absorption of the
photoactive compound (PAC) in the actinic range of the spectrum. So with increasing film
thickness exposure dose has to be adjusted to provide sufficient energy also at the bottom
of the photoresist, otherwise the pattern cannot be cleared. In extreme cases it becomes
almost impossible to expose the resist properly and exposure doses above 1000 mJ/cm²
have to be applied. Under these conditions unwanted side effects also appear: the dose at
the surface of the photoresist becomes too high and induces crosslinking of the resist. This
effect is similar to the well known deep-UV hardening used to preserve the resist profiles at
postbake temperatures up to 200°C. Standard resist would also generate too much nitrogen
during exposure which, trapped in the thick layer, cannot diffuse fast enough and may lead
to lifting of the resist.
For AZ 4500-series photoresists we have chosen a special photoactive compound with
low absorption and reduced nitrogen content which enables these resists to be used at
thicknesses up to 50 µm. The highest viscosity product AZ 4562 allows to spin coat 10 µm in
a single step (2000 rpm). For even higher thicknesses special coating techniques have to be
1. The common spin time of about 30 - 40 seconds is reduced down to only 3 seconds.
By this 20 µm are obtained, however the substrate has to be left on the spinner in a
horizontal position for another minute to allow for drying.
2. AZ 4562 may be multiple coated with a bake cycle in-between. Due to the high solids
content of this resist, which is close to the dissolution limit, the underlying coating
will only be dissolved minor. The bake temperatures in-between should not exceed
90°C or the final prebake temperature.
When using high film thicknesses some special guidelines have to be observed: after coating
the resist should be kept at room temperature for at least 15 minutes to allow most of the
solvent to evaporate before it is put into an oven for prebake. Otherwise the resist surface
will dry quite fast and trapped solvent remaining in the bulk may form bubbles and lift the
resist film. Adhesion failure is the result. Using a hotplate instead of an oven is the better
choice, especially when the temperature is ramped to the final value.
The development process also has to be adopted to the high film thickness: Background forthis is the fact that even heavily overexposed positive photoresists only have limited dissolution rates. There is a saturation at values in the order of 100 nm/s. For this it is
recommended to operate at development rates of about 2 µm/min. and adjust the exposure dose for proper clearing and feature size.
This resist series is designed for use with any common sodium and potassium based developer. AZ 340, 1:5 diluted with water is a good choice, AZ 400K may be used as well.