Pinoy physicists develop way to detect IC defects

Detecting faulty integrated circuits (IC) could now become a less expensive procedure through a cutting-edge technology developed by a team of physicists led by Dr. Caesar Saloma of the National Institute of Physics of the University of the Philippines Diliman.

The advanced technique produces high-contrast, layer-by-layer images of semiconductor sites in the ICs by combining the capabilities of a reflectance laser confocal microscope with single-photon, optical beam-induced current (1P-OBIC) imaging.

The technique offers an inexpensive way of detecting accurately the presence of defects and failure in an IC.

"The number of transistors contained in semiconductor devices has increased very rapidly over the years," Saloma said. "To fit them in a semiconductor, each of the electronic elements is made smaller than a hundredth of the width of the human hair. Moreover, they are stacked on top of each other in layers. With millions of them in a single device, how are we going to detect which of them is not working?"

"This is the challenge that scientists around the world, including us, are working on at the moment." Saloma added.

The 1P-OBIC enables the viewing of the semiconductor site by scanning a one-photon light beam across the semiconductor device. As the device is illuminated, it generates electric currents which translate into light images on the computer screen. Since defective elements cannot produce currents, they appear onscreen as dark spots.

Meanwhile, the laser confocal microscope produces high-contrast images of highly reflecting samples such as metals and semiconductor surfaces. It can also show three-dimensional images of a thick IC sample which ordinary microscopes cannot do.

Semiconductors have become prolific because most machines nowadays such as airconditioning units, cars, airplanes and ATMs are already computerized. A vital part of the computer, the semiconductor has millions of electrical elements that work together to do specific tasks. A failure in one of these elements could break down the entire computer system. Quality control is, therefore, a critical part of semiconductor device manufacturing.

Competing method

According to Saloma, the competing method for detecting IC failures is the two-photon OBIC which uses infrared light to penetrate deep layers of semiconductor materials. This makes it quite expensive as its light source alone costs $200,000 compared with Saloma’s 1P-OBIC that uses a light source costing from $100 to $500.

"We are currently working on an even cheaper design," Saloma disclosed.

Saloma said the technology, being accurate and less expensive, could lead to lower production cost of ICs and help prevent wastage losses in semiconductor industries caused by undetected defects or failures in ICs. He added that waste reduction is beneficial to the environment.

The project has gained favorable worldwide exposure through its publication in Applied Optics (July 10, 2002 issue) which is a peer-review journal of the Optical Society of America (www.osa.org). The publication was later highlighted in the August 2002 issue of Photonics Spectra (www.photonics.com), an independent technology magazine with worldwide circulation.

The technology is expected to boost the semiconductor and electronic industries, the country’s most dynamic economic sectors with semiconductors and components comprising majority of Philippine exports.

The Philippine Council for Advanced Science and Technology Research and Development (PCASTRD) of the Department of Science and Technology provided a P1.9-million grant to the project for the acquisition of laboratory facilities needed for the research.

This support is part of PCASTRD’s Institution Development Program aimed at upgrading the capabilities of institutions to conduct research in the advanced science and technology fields.

PCASTRD, as one of the DOST’s sectoral planning councils, is tasked to develop, integrate and coordinate the national research systems for the advanced science and technology sector. Its priority areas are photonics technology, biotechnology, information and communications technology, materials research, optic technology applications, and electronics, instrumentation and controls.

For more information on the technology, contact PCASTRD at [email protected] or tel. nos. 837-2071 to 82 local 2100-2109 or Dr. Caesar Saloma at (02) 454-4239 or e-mail [email protected].