What is the hard film of photoresist and "glue"

Want to ask the hardening film before corrosion is to increase the adhesion of the glue, then add a step after the hardening film "glue", what is the role of this step, "glue" how to "play"?
What is the composition of photoresist?
It is mainly composed of resins, photoinitiators, solvents and additives. Therefore, in the lithography process, continuous baking is required to remove the solvent.
What are the steps of baking in the lithography process?
1. Soft Bake
After the liquid photoresist is homogenized, the baking is carried out. Most of the residual solvent in the coating process is removed to stabilize the photoresist film layer and improve its uniformity. Improve graphic fidelity during subsequent exposures.
2. Post Exposure Bake (PEB)
Promote the continuation of the photochemical reaction in the photoresist, reduce the standing wave effect generated during the exposure process, and improve the resolution and contrast of the photolithographic pattern
3. Hard Bake
After development, the photoresist is baked to harden it and enhance the adhesion, mechanical strength and etching resistance of the photoresist to the substrate. Without this step, the photoresist is prone to fall off and other abnormalities in acid-base solvents. The temperature should not be too high, easy to make the photoresist deformation.
And when we say hard bake, we generally mean hard bake.
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What is gluing?
Gluing can be understood as Ashing or Descum. The principle is to pass oxygen into the reaction chamber, isoionize it, and react with the photoresist to produce water vapor, carbon dioxide and other gases.
The main functions are:
1. After the photoresist development, there are several angstroms of residuals or anti-reflection layers, HMDS, viscosification layers that are difficult to be removed by the developer, which can be removed by the Ashing process.
2, improve the photoresist morphology.