Development
- Wirth, Justin C
Overview
After exposure, development of either optical or electron beam photoresists is necessary to define a pattern. Information about the BNC supplied resists is available below. Additionally, users may feel free to add information about developers their groups have purchased.
Metal Ion Based Developers
Metal Ion developers use a potassium or sodium solution to develop photoresist. They may also be referred to as inorganic developers.
Inorganic development should not be mixed with metal free (TMAH) based developers. TMAH contamination (even on the PPM level) can seriously affect the speed of the inorganic developer.
The bath life/shelf life of inorganic developer is highly dependent on carbon dioxide absorbed from the air. CO2 causes the development rate to decrease. Therefore, exposure to air should be minimized for bottles, and developer left exposed to air will not be good after a period of hours.
Developed resist will also cause the development rate to decrease. A 0.1% concentration of dissolved resist will, as a rule of thumb, decrease the development rate by 10%. Development rate will approach zero as dissovled PR concentration approaches 1%.
Note that alkaline developers (AZ 400K and AZ 351) will etch aluminum, and should be avoided with metallic aluminum, aluminum alloys, and aluminum compounds. To avoid this, AZ Developer should be used instead. However it's higher dark erosion rate makes it a less optimal choice for non-Al substrates.
References:
AZ 400K
AZ 400 K is a potassium based developer for Novolak based photoresist, such as AZ1518 and AZ9260. It is particularly recommended for thick resists such as AZ9260. It is a basic solution (pH=12.9) of buffered potassium hydroxide to allow for extended bath life. Chemically, it is a solution <15% potassium borate in >85% water. It is concentrated, and requires dilution before use. Recommended dilutions are:
| High Sensitivity/Speed | High Contrast |
|---|---|
| 1:3 Developer:Water | 1:4 Developer:Water |
References:
- AZ Developer, 400K, and 421K Inorganic Developers Datasheet (AZ)
- AZ 400K Technical Datasheet (Merck)
- AZ 400K Developer MSDS
AZ 340
AZ 340 is a buffered sodium hydroxide (NaOH) based developer for Novolak based photoresist, such as AZ1518 and AZ9260. It is particularly recommended for thin resists such as AZ1518. It is a basic solution (pH≈13) of <2% sodium hydroxide and <5% of disodium tetraborate buffer. It is concentrated, and requires dilution before use. Recommended dilutions from the manufacturer have not been found, but these may be used as a general guide:
| High Sensitivity/Speed | High Contrast |
|---|---|
| 1:1.5 Developer:Water | 1:2 Developer:Water |
References: