Spinner Material Compatibility

Spin on materials have now been segregated by spinner. Please see the following page for what spinner you need to use for a particular material:

Spinner Allowed Chemicals

Technology Overview

Spin coating of photoresist allows a uniform layer to be distributed on a substrate in a short amount of time.

Advantages:

• Uniform coating of photoresist on rotationally symmetric substrates (i.e. wafers)
• Small amount of photoresist used
• Quick process

Disadvantages, while using a small amount of liquid photoresist. The thickness of spun resist will be approximately proportional to the viscosity (high viscosity = resistant to flow, low viscosity = more easily flows) of the unspun photoresist, and will be inversely proportional to the square root of the spin speed (Mack 2006, p4).

While spin coating is relatively straight forward, be aware of the following:

• Coating uniformity degrades for non-rotationally symmetric substrates (i.e. squares and rectangles)
• Edge bead formationEvaporation forms an 'edge bead' at the substrate edges; This is more substantial for longer spin times, thicker photoresist, and less circular substrates
• Coverage of textured/patterned surface depends on the thickness of photoresist
• Photoresist adhesion will depend on the surface state of the substrate

Example of a multidispense spin (via Specialy Coating Systems):

Spinning may either proceed directly to the target RPM, or via multiple steps to more gently distribute resist. In general, thin resist layers (e.g. 2 μm of AZ1518) on a properly prepared substrate surface (e.g. BOE cleaned silicon) spin best without a low RPM dispersal step, while thicker films (e.g. 10 μm of AZ9260) on non-ideal surfaces (e.g. Piranha cleaned glass) may benefit from a dispersal step.

An example of a multistep coating cycle is seen below. Note that typically only a single low RPM dispersal step is used.

Representative Coating Cycle

Process Library

For in-depth information about photoresist properties and spin recipes, see BNC Supplied Photoresists.

Typical Recipe:
Step 0:   Values should be set to 0 or "None". Disp should be rounded up to the nearest chuck size, and Disp Time may be set to a nonzero value to avoid the "Homing" step after spinning.
Step 1:   Timed ramp and dwell at process rpm.
Step 2:   Timed ramp down to zero rpm / unload

AZ1518

Standard Spin, AZ1518, no dispersal steps

Standard Spin, AZ1518, initial dispersal spin

References

MicroChemicals: Spin Coating of Photoresist (Internal Resource)