Developers are a chemical solvent that dissolve the dissolveable area of photoresist (PR) caused by exposure. PR in the photolithography process is mainly divided into positive PR and negative PR. Therefore, developers are divided into positive PR developers and negative PR developers. The positive PR developer is usually a strong alkali solution diluted with water and used in positive PR development process. The negative PR developer is usually an organic solvent and used in negative PR development process.
Fig. 1. Schematic diagram of development process.
In order to dissolve part of the PR to obtain the pattern in the PR coating, a suitable developer must be used. The part of positive PR that has not been illuminated by the exposure lamp will be retained after development, while the part of negative PR that has not been illuminated by the exposure lamp will be dissolved after development. It is simply described as the photosensitive region of the positive PR and the non-photosensitive region of the negative PR are dissolved in the developer during the development process. The development mechanism of positive PR developers and negative PR developers is both acid-base neutralization reaction, but there are slight difference.
The positive PR developer dissolves the positive PR. The positive PR after exposure is acidic and can be neutralized with alkaline positive PR developers. Appropriate buffer added to the positive PR developer can maintain the balance of developer PH, so that the developer concentration does not change too fast. Therefore, the addition of buffer is beneficial to the development effect.
The negative PR developer dissolves the negative PR. The unexposed region of the negative PR is weakly acidic and can be neutralized with alkaline negative PR developer. Negative PR has large molecular weight and hydrophobicity, so surfactants are usually added to the negative PR developer to improve the hydrophilicity and ensure the development effect.
Alfa Chemistry provides developers for customers, including but not limited to the following products.
Positive PR developers
Sodium hydroxide (NaOH)
Tetramethylammonium hydroxide (TMAH)
Tetramethylammonium hydroxide with surfactant (TMAH with surfactant)
Potassium hydroxide with water (KOH with water)
Negative PR developers
Sodium carbonate (Na2CO3)
Potassium hydroxide with buffer
(KOH with buffer)
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