What happened to the photoresist (S1818) after RIE?

[Yinxiao Li]

S1818 was hard baked at 125C for 2 hours and then put into RIE chamber. The recipe is SF6, 30mtorr, 45sccm, 3min. However, the color of the resist totally changed, as shown in the attachment.
I totally don't understand what happened here. 3 min of SF6 etching won't peel the photoresist off. Is there anybody having any ideas?

 

[phyzguy]

S1818 was hard baked at 125C for 2 hours and then put into RIE chamber. The recipe is SF6, 30mtorr, 45sccm, 3min. However, the color of the resist totally changed, as shown in the attachment.
I totally don't understand what happened here. 3 min of SF6 etching won't peel the photoresist off. Is there anybody having any ideas?

Please give more detail of what you did and what your question is. It sounds like you think that the change in color indicates that the photoresist has been removed. This is probably not the case. Probably the photoresist is still there. There are several things that could cause the color of the photoresist to change, such as:
(1) The thickness of the photoresist has changed due to some of it being sputtered away by the RIE plasma.
(2) The index of the photoresist has changed due to increased cross-linking due to exposure to the UV light from the plasma.
(3) The surface of the photoresist has changed due to incorporation of S or F atoms from the plasma.
(4) Something else...

 

[Yinxiao Li]

Please give more detail of what you did and what your question is. It sounds like you think that the change in color indicates that the photoresist has been removed. This is probably not the case. Probably the photoresist is still there. There are several things that could cause the color of the photoresist to change, such as:
(1) The thickness of the photoresist has changed due to some of it being sputtered away by the RIE plasma.
(2) The index of the photoresist has changed due to increased cross-linking due to exposure to the UV light from the plasma.
(3) The surface of the photoresist has changed due to incorporation of S or F atoms from the plasma.
(4) Something else...

This sounds like a real profession answer! Although I cannot verify what is really going on, thank you so much for your great idea!