Specific Process Knowledge/Lithography/MiR: Difference between revisions

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Revision as of 15:02, 30 January 2023

Resist description

AZ MiR 701 is a positive UV photoresist. It is considered to have high selectivity for dry etching.

Spin coating

Spin curves for AZ MiR 701 (29 cps) using a 30 s spin-off, and a 60 s @ 90°C proximity softbake

Typical spin parameters:

Spin off: 30-60 s
Soft bake: 60 s @ 90°C in proximity

Exposure

Dehydration of resist film:
During exposure in the maskless aligners, MiR can be sensitive to dehydration by the air flow applied by the pneumatic auto-focus mechanism. This may lead to insufficient development, especially for small substrates. This problem can be alleviated by switching to the overview camera for a period of 1 minute before starting the exposure, or simply by parking the writehead away from the exposure location for 1 minute before starting the exposure.

The effect can also be reduced by increasing the soft bake.

Post-exposure bake

Typical PEB parameters:

PEB temperature: 110°C
PEB time: 60 s

During exposure, interaction between the incoming light and the light reflected by the substrate can cause a standing wave to form in the resist (especially true for single line/wavelength exposure). This leads to a wavy sidewall after development. The standing wave pattern can be removed by introducing a post-exposure bake before development, which allows the activated PAC to diffuse into unactivated regions, thus smoothing the sidewall. The recommended PEB for MiR is 60 s at 110°C (for a 1-2µm film). Thicker coatings may require longer bake, and substrate thickness and material, e.g glass, may also affect the required baking time.

Since the post-exposure bake is at an elevated temperature compared to the soft bake, it will cause the resist film to become 5-10% thinner (probably due to continued evaporation of solvent). A 1.5µm thick MiR resist film will be approximately 1.4µm after PEB.

Development

Development speed:

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

@@ Line 1: / Line 1: @@
-'''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/MiR click here]'''
+__TOC__
-AZ MiR 701 is a positive UV photoresist.
+==Resist description==
+AZ MiR 701 is a positive UV photoresist. It is considered to have high selectivity for dry etching.
 ==Spin coating==
+[[Image:MiRspincurves.JPG|640px|thumb|Spin curves for AZ MiR 701 (29 cps) using a 30 s spin-off, and a 60 s @ 90°C proximity softbake]]
-[[Image:MiRspincurves.JPG|500x500px|thumb|Spin curves for AZ MiR 701 (29cps) using a 30s spin-off, and a 60s@90°C softbake (proximity bake for Gamma)]]
+'''Typical spin parameters:'''
+*Spin off: 30-60 s
+*Soft bake: 60 s @ 90°C in proximity
 <br clear="all" />
 ==Exposure==
+'''Dehydration of resist film:'''<br>
+During exposure in the maskless aligners, MiR can be sensitive to dehydration by the air flow applied by the pneumatic auto-focus mechanism. This may lead to insufficient development, especially for small substrates. This problem can be alleviated by switching to the overview camera for a period of 1 minute before starting the exposure, or simply by parking the writehead away from the exposure location for 1 minute before starting the exposure.
-During exposure using the maskless aligners, MiR can be sensitive to dehydration by the air flow applied by the pneumatic auto-focus mechanism. This may lead to insufficient development, especially for small substrates. This problem can be alleviated by switching to the overview camera for a period of 1-2 minutes before starting the exposure. The effect can also be reduced by increasing the soft bake.
+The effect can also be reduced by increasing the soft bake.
 ==Post-exposure bake==
+'''Typical PEB parameters:'''
+*PEB temperature: 110°C
+*PEB time: 60 s
-During exposure, interaction between the incoming light and the light reflected by the substrate can cause a standing wave to form in the resist (especially true for single line/wavelength exposure). This leads to a wavy sidewall after development. The standing wave pattern can be removed by introducing a post-exposure bake before development, which allows the activated PAC to diffuse into un-activated regions, thus smoothing the sidewall. The recommended PEB for MiR is 60s at 110°C (1-2µm film). Thicker coatings may require longer bake, and substrate thickness and material, e.g glass, may also affect the required baking time.
+During exposure, interaction between the incoming light and the light reflected by the substrate can cause a standing wave to form in the resist (especially true for single line/wavelength exposure). This leads to a wavy sidewall after development. The standing wave pattern can be removed by introducing a post-exposure bake before development, which allows the activated PAC to diffuse into unactivated regions, thus smoothing the sidewall. The recommended PEB for MiR is 60 s at 110°C (for a 1-2µm film). Thicker coatings may require longer bake, and substrate thickness and material, e.g glass, may also affect the required baking time.
-As the post-exposure bake is at an elevated temperature compared to the soft bake, it will cause the resist film to become 5-10% thinner (probably due to continued evaporation of solvent). A 1.5µm thick MiR resist film will be approximately 1.4µm after PEB.
+Since the post-exposure bake is at an elevated temperature compared to the soft bake, it will cause the resist film to become 5-10% thinner (probably due to continued evaporation of solvent). A 1.5µm thick MiR resist film will be approximately 1.4µm after PEB.
 ==Development==
+'''Development speed:'''
-A 1.5-2µm MiR resist film is fully developed in 60s using TMAH (AZ 726). Depending on the exposure dose, thicker coatings may develop in 1 min, but it is probably better to aim for a similar development speed (2µm/min).
+*Puddle development in 2.38% TMAH (AZ 726 MIF): ~2 µm/min