Using atomic force microscope
Atomic force microscope firm Park Systems has developed an inspection equipment for masks used in the extreme ultraviolet (EUV) process in wafer fabrication, TheElec has learned.
The equipment can inspect the mask for defects and improvements without damaging it, people familiar with the matter said.
Park Systems is testing the equipment with global foundry companies, which may lead to a supply deal soon, they added.
EUV’s wavelength is fourteenth of that of argon fluoride (ArF) lasers, allowing it to draw even finer circuit patterns on the wafer.
This means the mask used for the process must also be more finer and accurate. The masks used in EUV processes can cost up to a billion won (close to US$1 million), so having them damaged by dust can be costly.
Currently, Japan’s Lasertec is the only company that offers an inspection equipment for EUV masks, which uses infrared technology.
But only a few units of this equipment are produced and they are expensive.
Park Systems’ equipment uses an atomic force microscope instead of chemical rays. People familiar with the matter said this allows the equipment not only to look for defects but can analyze the defect and offer improvements.
Park Systems vice president Cho Sang-joon, speaking at the 2021 Semiconductor EUV Ecosystem Big Trend Relay Conference hosted by TheElec last week, said currently available inspection equipment mostly use laser such as e-beam to remove defects on the mask, but this can cause damage to the surface if the sample sizes were to become smaller. Cho said that as an alternative, use of microscopes can prevent mask from being damaged.
Atomic force microscope uses an ultra-small probe to scan the surface of the sample at atomic level. It then measures the forces between the probe and the sample to measure the mechanical, electrical and optical properties of the sample and nanometer range.
The resolution from this microscope is a thousand times better than conventional scanning electron microscopes.
Park Systems’ atomic force microscope analyzes defects such as particles or bump on the mask. It then recognizes whether the defective material on the mask is soft or hard and uses the best method to remove them. For instance, if the defective material is hard, the equipment will push it out of the circuit physically.
Park Systems’ kit is being tested by a top foundry firm abroad. It was also being tested by a South Korean foundry through joint development manufacturing method.