IPF 2010: A ‘light’ repair to silicon chips

The 2009 Nobel Prize in Physics for the development of CCDs and fiber-based telecommunications underscored the importance of basic research in industrial labs and the impact that research can have on society. The American Institute of Physics’s (AIP*) Corporate Associates was created to foster interest in exactly that kind of work.

The Industrial Physics Forum (IPF) is the Corporate Associates’ annual showcase, bringing together researchers and executives to hear leading scientists discuss forefront topics. This year’s IPF, held October 25-26 in Rochester, New York, is associated with the Frontiers in Optics meeting sponsored chiefly by an AIP Member Society, the Optical Society of America, with the American Physical Society’s Division of Laser Science also playing a role.

This year marks the 50th anniversary of the invention of the laser, so the IPF’s theme is applications of laser technology. The talks are divided into three broad topic areas: biomedical applications, environmental applications, and metrology.

Laser fuse technology

In modern memory devices such as DRAM and Flash, the fabrication is not perfect and requires repair steps in the back end of the manufacturing process. For this purpose, lasers can be used to sever a conducting metal line by heating it up. Lasers can also be used to link up a new conducting path. By these operations, bad elements in the devices can be replaced with fresh ones. Laser repair can, for instance, be carried out on liquid crystal displays to turn off the broken bright pixels.

How important is the step of repairing defective elements in the integrated circuit industry? Joohan Lee , a scientist at the GSI Group (Bedford, MA), said that the ability to repair microchips is critical: “Microelectronic devices have been designed with redundancy in their cells in order to improve the yields of manufacturing. For example, the modern DRAM chips have near 0% yields before the laser repair step.”

Lee reported on the latest advances in laser repair technology and discussed various aspects of laser applications in the electronics industry. The laser repair process consists of laser cutting or linking of fine metal lines (typically less than 1 micron wide) that are called laser fuses. The cutting and linking require a high degree of accuracy and fine energy control of the laser beam. Generally, small-wavelength laser light (often green and ultraviolet beams), short pulse widths, and polarization of the beam, are all necessary for reliable processing.

Of course as circuits shrink, the fuse elements—the laser-activated back-up parts of the circuit—have to shrink too. Over the past 10 years, Lee said, the fuse pitch has been decreased from 10 µm to less than 2 µm. Dealing with such fine-pitch fuses requires exquisite alignment and control of the laser beam.

Phillip F. Schewe

All the talks at IPF 2010 were recorded and are now available on video .