Specific Process Knowledge/Lithography/4562: Difference between revisions

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Resist description

AZ 4562 is a positive UV photoresist for thick coatings (above 5µm).

Priming

HMDS priming is recommended for improved adhesion.

Spin coating

Spin curves for AZ 4562 using 60s spin-off and 60s@100°C softbake on LabSpin, and 30s spin-off and 300s@100°C 1mm proximity softbake on Gamma

Typical spin parameters:

Spin off: 30-60 s
Soft bake: 300 s @ 100°C in proximity

The thickest achievable coating using a normal spin cycle is probably 10-15µm. However, reducing the spin-off time to a few seconds at 2000 rpm, has successfully been used to increase the coating thickness beyond 20 µm on a Gamma coater. The substrate waits for 1 min before softbake, in order to reduce the edge bead height.

Exposure

Before exposure, the resist must be rehydrated:

A 1-2 µm resist film requires less than 1 minute
A 6 µm resist film requires 15-20 min
A 10 µm resist film requires an hour, or more

After exposure, the nitrogen generated in the resist film must be allowed to diffuse out, in order to avoid bubble formation (in particular before any heating). This process is similar to rehydration, but usually slower.

Exposure in mask aligner: In order to avoid heating during exposure, leading to the formation of bubbles, it is recommended to use multiple exposure, limiting the exposure time for each cycle to 10-15 s, and using a 10-15 s pause between cycles.

Development

Development speed:

Puddle development in 2.38% TMAH (AZ 726 MIF): ~2 µm/min

The recommended development speed in 2.38% TMAH (AZ 4726 MIF) for AZ 4562 is 2 µm/min. A 6.2µm resist film thus requires ~3 min development, recommended as three separate 60 s puddles. 10µm AZ 4562 has successfully been developed using 4 x 60 s development.

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-'''Feedback to this section''': '''[mailto:labadviser@danchip.dtu.dk?Subject=Feed%20back%20from%20page%20http://http://labadviser.danchip.dtu.dk/index.php/Specific_Process_Knowledge/Lithography/4562 click here]'''
+__TOC__
+==Resist description==
 AZ 4562 is a positive UV photoresist for thick coatings (above 5µm).
 ==Priming==
+HMDS priming is recommended for improved adhesion.
-Using HMDS priming with AZ 4562 seems to cause more problems than it solves, and is generally not recommended. HMDS priming seems to make the adhesion worse, maybe due to accumulation of N2 at the resist-substrate interface during exposure. A combination of oxygen plasma treatment (7min @ 400ml/min O<sub>2</sub> and 500W power) and HMDS has been successful for a 14µm coating, but has not been tested further (Taran Dec 2019).
+==Spin coating==
+[[Image:4562spincurves.JPG|500x500px|thumb|Spin curves for AZ 4562 using 60s spin-off and 60s@100°C softbake on LabSpin, and 30s spin-off and 300s@100°C 1mm proximity softbake on Gamma]]
-If adhesion failure is an issue, a dehydration bake (e.g. 1min at 100°C) just before spin coating is recommended. Storing the coated substrates before exposure also leads to adhesion failure after as little as a couple of days.
-==Spin coating==
+'''Typical spin parameters:'''
+*Spin off: 30-60 s
+*Soft bake: 300 s @ 100°C in proximity
-[[Image:4562spincurves.JPG|500x500px|thumb|Spin curves for AZ 4562 using 60s spin-off and 60s@100°C softbake on LabSpin, and 30s spin-off and 300s@100°C 1mm proximity softbake on Gamma]]
-The thickest achievable coating using a normal spin cycle is probably 10-15µm. However, reducing the spin-off time to a few seconds at 2000rpm has successfully been used to increase the coating thickness beyond 20µm on a Gamma coater. The substrate is rested for 1min before softbake in order to reduce the edge bead height.
+The thickest achievable coating using a normal spin cycle is probably 10-15µm. However, reducing the spin-off time to a few seconds at 2000 rpm, has successfully been used to increase the coating thickness beyond 20 µm on a Gamma coater. The substrate waits for 1 min before softbake, in order to reduce the edge bead height.
 <br clear="all" />
 ==Exposure==
+Before exposure, the resist must be rehydrated:
+*A 1-2 µm resist film requires less than 1 minute
+*A 6 µm resist film requires 15-20 min
+*A 10 µm resist film requires an hour, or more
-Before exposure, the resist must be rehydrated. A 1-2µm thick resist rehydrates in less than 1 minute, a 6µm layer requires 15-20min, and a 10µm layer requires an hour, maybe more.
-After exposure, the nitrogen generated must be allowed to diffuse out, in order to avoid bubble formation (in particular before any heating). This process is similar to rehydration, but usually slower.
+After exposure, the nitrogen generated in the resist film must be allowed to diffuse out, in order to avoid bubble formation (in particular before any heating). This process is similar to rehydration, but usually slower.
-In order to avoid heating during exposure, leading to the formation of bubbles, it is recommended to use multiple exposure, limiting the exposure time for each cycle to 10-15s, and using a 10-15s pause between cycles.
+'''Exposure in mask aligner:'''
+In order to avoid heating during exposure, leading to the formation of bubbles, it is recommended to use multiple exposure, limiting the exposure time for each cycle to 10-15 s, and using a 10-15 s pause between cycles.
 ==Development==
+'''Development speed:'''
+*Puddle development in 2.38% TMAH (AZ 726 MIF): ~2 µm/min
-The recommended development speed for AZ 4562 is 2µm/min. A 6.2µm resist film thus requires 3min development, usually as three 60s puddles of TMAH (AZ 726 MIF). 10µm AZ 4562 has successfully been developed using 4x60s development
+The recommended development speed in 2.38% TMAH (AZ 4726 MIF) for AZ 4562 is 2 µm/min. A 6.2µm resist film thus requires ~3 min development, recommended as three separate 60 s puddles. 10µm AZ 4562 has successfully been developed using 4 x 60 s development.