# Photoresist Strip SOP

<figure><img src="https://2353182699-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FXgXjz6D0Vz2o0EOp8JO5%2Fuploads%2FqjLdt0et4MXDFNJIdwaf%2Fimage.png?alt=media&#x26;token=269a54c7-17e6-4567-900d-a3eb7caab87a" alt="" width="256"><figcaption><p>Example of Photoresist on Surface of Chip</p></figcaption></figure>

<figure><img src="https://2353182699-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FXgXjz6D0Vz2o0EOp8JO5%2Fuploads%2FCKEtBHeGyMstJRzOgbla%2Fimage.png?alt=media&#x26;token=ceace277-b672-4550-bca2-b4ed1c427cc5" alt="" width="256"><figcaption><p>Photoresist Removed post-strip</p></figcaption></figure>

## Parameters

| Total Time                   | 1 minute   |
| ---------------------------- | ---------- |
| Acetone Spray Time           | 20 seconds |
| Isopropyl Alcohol Rinse Time | 10 seconds |
| Nitrogen Blow Dry Time       | 10 seconds |

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## Purpose

Stripping removes all photoresist from a chip. This is typically done after an etch step is completed, though it can also be used to remove resist before etching if you need to redo patterning.

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## Tools

1. Fume Hood with Sink
2. N2 gun

## Materials

1. Chip with photoresist
2. Acetone
3. Isopropanol

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## Troubleshooting and Best Practices

<details>

<summary>Chip flying out of tweezers during nitrogen blow drying</summary>

Lie the chip flat on a cleanroom wipe surface while still holding it with the tweezers.&#x20;

Only apply nitrogen normal to the surface of the chip, so it presses against the cleanroom wipe instead of lifting it up.

</details>

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## Procedure

### Stripping

1. Spray the entire chip with acetone
2. Rinse with IPA
   1. IPA must always be used *after* acetone to remove any acetone residue
3. Dry with nitrogen gun until the surface is entirely dry
   1. This requires you to blow dry the back of the chip as well. Surface tension tends to pull the liquid towards the back

## Safety

Be sure to spray the chip over a sink. Do not use near source of high heat.