LithoTalk

[mar]

Hi all,

Could anyone tell me the easiest way to calculate the suitable exposure time for 1um CD features?

I'm using Karlsus MA4 (i-line) mask aligner, Az nLOF 2070 resist and 6.0 mW/cm2 light intensity.

Cheers.

[Guest]

Hello,

the suitable exposure dose for a negative tone resist such as the AZ nLOF 2000 depends on the undercut you would like to attain.

If the undercut should be pronounced, the optimum exposure dose is lower as for the requirement of comparable steep resist sidewalls.

Additionally, the post exposure bake temperature and -time also impact on the result. Within a certain range, a high PEB temperature compensates a low exposure dose, and vice versa.

Finally, the optical substrate parameters such as reflection coefficient, transmission, or roughness also make it hard to calculate the dose.

I would recommend to keep the PEB at 120°C for 1 minute, and vary the (i-line) exposure dose between 10 and 40 mJ/cm2 (2 ... 6 seconds in you case in 1 s steps), and look how the result looks like.

A recommended developer for such small features would be the AZ 726 MIF, the 326/300 MIF will also do.

Good Luck!