Why positive PR is the better than negative PR in VLSI

[empkth]

As attached, I know basic concept between Positive and Negative PR

But, I confirm this message; Negative resists were popular in the early history of integrated circuit processing, but positive resist gradually became more widely used since they offer better process controllability for small geometry features. Positive resists are now the dominant type of resist used in VLSI fabrication process.

1. Why Positive PR is the better than negative PR in VLSI?
2. Why Positive PR is the better than negative PR about "Resolution" ?

R=K*λ/NA (Rayleigh criterion)

Please.. Answer to me, I'm so curiosity... with Engineertic answer..

 

[davenn]

Hi
welcome to PF

Negative resists were popular in the early days of integrated circuit processing. Positive resist slowly became more widely used since they offer better process control for small geometry features as dies became higher density. Positive resists are now the main type of resist used in VLSI fabrication processes.


Dave

 

[empkth]

Thanks to Dave!

But What is the meaning of higher density? So, higher density... After what?

Please.. Add to logical answer.

 

[davenn]

higher density = more transistors etc in a given area of the die

 

[alphy]

I can confirm that positive PR (photoresist) is indeed the better option compared to negative PR in VLSI (Very Large Scale Integration) for several reasons.

Firstly, positive PR offers better process controllability for small geometry features. This means that the fabrication process can be more precise and accurate when using positive PR, resulting in a higher quality end product. In contrast, negative PR can be more difficult to control and can lead to variations in the final product.

Secondly, positive PR is now the dominant type of resist used in VLSI fabrication process. This is a result of continuous advancements and improvements in the technology, making positive PR the preferred option for manufacturers. This widespread use of positive PR also means that there is a larger support system and more resources available for its usage, making it a more reliable and efficient choice.

In terms of resolution, the Rayleigh criterion (R=K*λ/NA) shows that the resolution of a system is directly proportional to the wavelength (λ) and inversely proportional to the numerical aperture (NA). Positive PR has a lower wavelength and higher numerical aperture compared to negative PR, resulting in a higher resolution. This means that positive PR can produce finer and more detailed features, making it a better option for VLSI applications where precision is crucial.

In conclusion, positive PR is the better option compared to negative PR in VLSI due to its better process controllability, widespread usage and support, and higher resolution capabilities. It is the preferred choice for achieving high-quality and precise results in VLSI fabrication processes.