Manufacturing Bits: Oct. 15

Sandia’s fab upgrade
Sandia National Laboratories has completed the first phase of a three-year upgrade program in its semiconductor wafer fab.

The goal of the program is to convert Sandia’s Albuquerque, N.M.-based fab from 150mm (6-inch) to 200mm (8-inch) wafer sizes. As part of the move, Sandia is converting its 0.35-micron (350nm) rad-hard process from 150mm to 200mm. The process is called CMOS7.

The conversion is well underway. Prototyping and product development activities have already resumed. Chips produced at Sandia are used for the nation’s nuclear stockpile. The upgrade will help sustain production of devices for national security applications through 2040.

In the fab, Sandia conducts both R&D and production work. “We’re effectively a low-volume, high-mix facility with a diverse flow in the fab,” said Mike Holmes, a senior manager at Sandia. “Moving to 8-inch wafers aligns us with industry, which means we have a more sustainable supply of starting materials, tools and service.”

Sandia has been developing and producing devices since the 1970s. Sandia National Labs is operated by the National Technology and Engineering Solutions of Sandia LLC, a subsidiary of Honeywell International, for the U.S. Department of Energy’s National Nuclear Security Administration. Sandia Labs has R&D responsibilities in nuclear deterrence, security, defense and energy technologies.

Over time, Sandia has advanced its efforts in microelectronics. Its fab is part of Sandia’s Microsystems Engineering, Science and Applications (MESA) complex.

The organization has two device production facilities in Albuquerque. The first is the semiconductor fab, which is being upgraded. The second is a compound semiconductor facility, which develops MEMS, photonics and RF devices.

“On the silicon side, our primary areas that we do work are in CMOS,” Holmes said. “On the compound side in that facility, it’s pretty diverse. We do heterogenous integration in that facility. We also do III-Vs.”

The CMOS-based fab conversion has been underway since mid-2018. The first phase was to covert the fab tools from 150mm to 200mm, which has been completed.

The second phase, which is underway, is to develop the process recipes on 200mm tools. Then, the next phase is to bring up the CMOS7 process on 200mm. The final phase, called requalification, is expected to be finished in 2021.

“Re-establishing the process on 8-inch wafers is extremely challenging,” Holmes said. “We have to tune hundreds of interrelated parameters to get the same end result as before but with different equipment and at a larger scale.”

Sandia’s fab has been accredited by the Department of Defense to provide “trusted foundry” services.

Nanoantenna detectors
In a separate development, Sandia National Labs has developed tiny gold antennas that promise to improve the thermal infrared radiation capabilities in systems.

Cameras and sensors have used thermal infrared capabilities for decades. These systems are used to detect heat in stars and galaxies. They are also used to detect people in various locations and items requiring security.

The problem? The technology is reaching its limits.

In the lab, Sandia has developed a new technology—a nanoantenna-enabled detector for infrared systems. The technology can boost the signal of a thermal infrared camera by up to threefold. It can improve the image quality by reducing dark current by 10 to 100 times.

There are several issues in making an infrared sensor. “The sensitivity and image quality of an infrared detector usually depends on a thick layer of detector material that absorbs incoming heat and turns it into an electrical signal that can be collected and turned into an image,” according to Sandia. “The thickness of the detector layer determines how much heat can be absorbed and read by the camera, but thick layers also have drawbacks.”

Instead of the traditional design, researchers developed a subwavelength nanoantenna. This involves a patterned array of gold squares, which in turn concentrates the light on a thinner layer of detector material.

“For example, with nanoantennas, it’s possible to dramatically expand the amount of information acquired in an image by exquisitely controlling the spectral response at the pixel level,” said David Peters, a Sandia manager.

“Now, we are to the point where we have proven this concept and this technology is ready to be commercialized. This concept can be applied to different detector types, so there’s an opportunity for existing manufacturers to integrate this new technology with their existing detectors,” Peters said.