Improving Photoresist for Chip Manufacture
According to Moore's Law, the number of transistors that can fit on a microprocessor will double roughly every two years. While it has been holding true for some time now, the technology has rapidly been approaching a barrier that could bring everything to a halt. One part of the barrier has been the photoresist used to etch circuitry onto silicon, but now a partnership between Berkeley Lab and Intel has found what could be its replacement.
To create the small and intricate circuitry in computer chips, manufacturers start with a wafer of silicon and coat it with a photoresist. Using a UV light source, an image of the circuitry is burned onto the photoresist, changing its properties where the light hits. A solvent is then used to wash away the unwanted photoresist, enabling selective deposition to build the circuitry up. The photoresist currently used was first developed to work with deep UV light, which has wavelengths between 248 and 193 nm, but manufacturers want to transition to using extreme UV, which can reach down to 13.5 nm for its wavelength. Due to the complexity of the photoresist compound, many have avoided developing a replacement as the risk could be so great.
A new photoresist is going to be needed to reach the smaller sizes chip makers want though, and some work has been done to that end. The Berkeley researchers decided to combine two promising photoresists and were surprised to find the mixture actually keeps the properties of its parts. One photoresist had great stability, but took long exposure times to achieve it, while the other was highly sensitive, but less mechanically stable. More work needs to be done to optimize the mixture, but the researchers believe it could reach manufacturing lines by 2017.
Source: Berkeley Lab