Photoresists are used in the production of printing plates, printed circuit boards, flat panel liquid crystal displays and magnetic recording heads, but the most important use is in the manufacture of integrated circuit (IC) devices, such as microprocessor devices for smart electronic chips and gadgets, IoT, AI chips and high data storage computer memory chips. Improvements in the resolution of what is called the photolithographic process – with the help of photoresists – have been key to advances in the semiconductor space.
IIT Mandi is among the few institutions in India working towards indigenisation of a wide spectrum of photoresists. In 2012, the institute took up the challenge of bulk production of indigenous photoresist formulations for Indian semiconductor industries and academic institutes.
“Photoresists are the workhorse for chip manufacturing. Electronic chips are everywhere, including telecom, robotics, aerospace, automobile, railways, defense, and in many other strategic and commercial sectors. It has a huge impact on the mobile phone industry; more the number of transistors on a chip, better is the performance,” says Subrata Ghosh, associate professor at the school of basic sciences at IIT Mandi.
In 2012, the institute started an initiative for the research and development of futuristic device fabrication technologies with the support of chipmaker Intel, which provided $300,000 for developing state-of-art materials for 20 nanometre (nm) node VLSI technologies. This was demonstrated for resolution of 20 nm under EUV (extreme ultraviolet lithography) at Lawrence Berkeley National Laboratory, USA.
To put this in context, Taiwan Semiconductor Manufacturing Co (TSMC), the world’s most valuable company in the field, is investing heavily in 5 nm fabrication, is working on a 3 nm fabrication line that will begin production in 2023, and also intends to start development of a 2 nm lithographic process.
Currently, the Indian semiconductor industry is involved in 180 nm node technology for ISRO. To print these nodes, the Semiconductor Laboratory (SCL) in Mohali uses four different types of photoresists that are sensitive to deep ultraviolet (DUV) light. As no Indian manufacturer develops these DUV resists, SCL is fully dependent on foreign vendors. The IIT Mandi photoresists team is working on developing such DUV resists.
The Space Application Centre (SAC) in Ahmedabad has done some work on 70 nm technology at the R&D level.
“The production capacity for wafer printing is limited in the country. The main challenge for us is the lack of indigenous photoresists, almost no dedicated testing facility for their industry-scale production, and of course less skilled manpower,” says Ghosh.
More testing facilities need big investments. “At present, we get very few slots at SCL’s fab line for testing our products as the same line is involved in chip production. A dedicated facility for testing is needed,” says Ghosh.