Deep silicon etch technology enables next-gen power devices

Article By : Maurizio Di Paolo Emilio

Lam Research's Syndion GP allows chipmakers to develop next-gen power devices and power management ICs using deep silicon etch technology.

Demand for high power devices is increasing in several electronics applications, including automotive, industrial, data center, and energy industries. Today, power devices have to meet stringent requirements such as high efficiency, high power density, low power consumption, and excellent thermal management. In order to successfully address these challenges, greater cross-wafer uniformity for higher aspect-ratio structures is needed during chip manufacturing. These advanced device structures can be achieved, without compromising the required form factor, by using very precise and uniform deep silicon etch process.

Chip manufacturers are facing a growing demand for specialty devices, including power devices, micro-electromechanical systems (MEMS), analog and mixed signal semiconductors, radio frequency IC (RF) solutions, optoelectronic devices, and CMOS image sensors (CIS), able to support a wide range of consumer and industrial applications, such as electric vehicles (EVs), Internet of Things (IoT), and 5G.

Lam Research launches Syndion GP

Lam Research Corporation, a global supplier of innovative wafer fabrication equipment and services to the semiconductor industry, has recently announced the Syndion GP, a new product that allow chipmakers to develop next generation power devices and power management integrated circuits using deep silicon etch technology. Michelle Bourke and David Haynes of Lam Research’s Customer Support Business Group will introduce us to this new product.

“At Lam Research, we have our own engineering and process development, that support these specialty technologies. The one that we are focused on today is silicon-based power devices and power management ICs,” said the speakers.

Lam Research is a manufacturer of plasma etch and deposition tools and  single wafer clean solutions for the fabrication of semiconductors, including advanced power semiconductor devices. These days, a lot of attention gets paid to wide bandgap semiconductors, such as gallium nitride and silicon carbide, and Lam Research is involved in those areas, as well. However, silicon-based power devices are the by far the biggest part of the market today, and there is still a lot of advanced development taking place on power devices like conventional MOSFETs, super junction MOSFETs, IGBTs, and analogue ICs.

Today, most FETs have migrated from planar structures to trench gate, whose structures and fabrication are absolutely critical from a performance point of view. At the same time, there has been a tendency to shift from 200mm to 300mm wafer fabrication, thus reducing the overall costs and taking advantage of leading advanced equipment available. Figure 1 shows a wafer processed with the Syndion GP product.

wafer on Lam Research equipment

Figure 1 A wafer on Lam Research equipment.

“We have launched Syndion GP to address those key challenges. This new product will give our customers the ability to run either 200 or 300mm wafer fabrication, allowing them a smooth transition towards increased capacity, as well as  improved technical capability”, said the speakers.

Most advanced silicon-based devices require higher power density and improved switching performance, without compromising the form factor. This requirement can be addressed by moving to a higher aspect ratio trench, which, however, requires a precise and uniform deep silicon etch processes to create the trenches. These deep trenches are very dense arrays of parallel lines, separated by submicron vertical sidewalls. As shown in Figure 2, deep trenches can have aspect ratios of 60:1 (or even higher), thus requiring excellent etch uniformity and profile. Just to give you an idea, the Burj Khalifa (one of tallest buildings in the world) has an aspect ratio of about 9:1, which is only 1/6 the aspect ratio of deep silicon trenches.

geometry of deep trenches

Figure 2 Geometry of deep trenches is critical to performance. (Source: Lam Research)

The control of etching of those structures is very important. In prior generations of IGBTs, the area of silicon involved in the etching process during the fabrication of the device was relatively low, it was 10-15% of the wafer size. In these advanced structures, capable of handling higher power densities, the area of etching silicon may be 50% or even 60% of the wafer surface, and that creates technical challenges for the chipmakers.

“With this migration from 200 to 300mm wafers, achieving the required uniformity across a much bigger wafer is even harder. Not only you need to go to 300mm, but you need your device yield to be extremely good, as well. And that’s what we are able to offer by developing specific solutions, such as Syndion GP, to address these applications,” said the speakers.

Syndion GP brings together many of the elements of Lam Research’s  technologies. It can provide very good control of the plasma across the wafer, achieved by controlling the distribution of radicals and ions for the deep silicon etch process, or DRIE process.

Since a large proportion of silicon-based devices has historically been manufactured on 200 mm wafers, today there is a limited amount of capacity, as most of 200mm fabs are full.

“The shortage of 200mm equipment is one of the reasons why our customers are moving to 300 mm, thus opening up more options for capacity. We wanted a tool that was flexible enough to process 200 and 300 millimeter wafers, and able to address conventional MOSFETs, IGBTs, super junction MOSFETs,  smart power applications, all with just one chamber technology,” said the speakers.

According to Lam Research’s speakers, silicon-based devices will coexist with wide bandgap materials (SiC and GaN) for a long time to come. There is still a lot of advanced research on silicon to improve the performance of IGBTs or super junction MOSFETs, allowing them to operate at higher voltages and higher frequencies. If the move to 300mm will certainly drive the economics and availability of manufacturing capacity, it will require an improved process control.

“That’s really what we have been focused on with the launch of our new product. We think that bringing these more advanced and high volume manufacturing tools to making silicon-based power devices will help to extend the life of those technologies for a long time to come,” said the speakers.

This article was originally published on EEWeb.

Maurizio Di Paolo Emilio holds a Ph.D. in Physics and is a telecommunication engineer and journalist. He has worked on various international projects in the field of gravitational wave research. He collaborates with research institutions to design data acquisition and control systems for space applications. He is the author of several books published by Springer, as well as numerous scientific and technical publications on electronics design.

 

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