Double-Digit Growth in Power Semiconductor Modules Fueled by Energy Concerns
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By Paula Doe, SEMI Adjacent Markets
From solar inverters and hybrid vehicles to household appliances, reducing energy usage means using more sophisticated power semiconductor devices with new manufacturing issues.
Growth for power semiconductor modules continues on its double-digit growth pace this year, driven by demand for more efficient PV inverters, hybrid electric vehicles, and industrial motor drives, reports IMS Research.
The $15.8 billion total market for discrete power semiconductors and modules recovered sharply from its plunge in 2009. It increased more than 10% in 2010 from its 2008 level, and is forecasted to pass $25 billion by 2015. “Demand in China and India to reduce electricity consumption by using inverters with appliance motors has caused sales of IGBTs to grow dramatically,” says Richard Eden, IMS senior market analyst for power and energy. “Fewer companies can make IGBTs than other MOSFETs, so this has led to shortages.” Replacing the typical thyristor-based on-off motor controls with variable speed motors using discrete insulated-gate bipolar transistors (IGBT) devices that can start up slowly saves energy in washers, dryers and room air conditioners.
Demand for Energy Efficiency Drives Power Semi Growth and Move to Wide-Band Gap Materials
Interest in improving energy efficiency is also driving interest in wide band gap materials. Demand for SiC Schottky diodes is already approaching $100 million annually and is growing twice as fast as that for silicon devices, though from a much smaller base. The SiC performs better at higher voltages (>600V) where silicon struggles, and can run at hotter temperatures (up to ~200°C vs ~120°C), reducing heat sink needs and allowing smaller power supplies. Initial sales are mainly for high-voltage PV and HEV markets, and volumes are still low, but Eden figures SiC MOSFETs and JFETs will eventually dominate at 1200V and above. One sweet spot where SiC can currently compete with silicon is the mid-range/string solar inverter market, where fewer of the higher performance SiC devices can be combined into a lower cost module. SiC costs so far remain too high for either the simpler needs of micro inverters, or for the utility-scale market, where efficiencies are already very high and competition has moved largely to price.
There’s plenty of headroom to bring down the high cost of SiC, however, by scaling to volume production from the current very low run levels. And the industry counts on moving to larger wafers to bring down costs as well. Eden says the sector is now moving from 2-inch to 3-inch wafers, with some leaders starting to look at 4-inch.
GaN power devices are still in much lower volumes than SiC, despite all the money being spent on development recently. Major markets will likely be those where its high switching frequency at 600V brings a boost in efficiency, such as PV inverters and high grade power supplies for things like servers and cellular phone network base stations, at lower voltages and lower costs than SiC. GaN has major long-term cost advantages over SiC due to its similarity in processing techniques to silicon and the existing high-volume production processing experience from GaN LED wafer fabrication.
Advances in silicon technology are aiming at some of these higher voltage applications as well. Super junction MOSFETS made in a conventional silicon process with improved trench technology at a handful of the leading semiconductor suppliers target applications of >400V. as well as with the larger motors in washers and air conditioners that need modules.
Lower Costs Drive Interest in High-Efficiency SiC
Though high efficiency wide band gap solutions have been around for some time, lower costs are starting to drive real demand.
SemiSouth Laboratories (Starkwell, MS) says that after three years on the market, its SiC JFETs are getting serious interest this year, as lower costs start to make the economics of the higher efficiency systems more compelling. Main push is coming from central PV inverters (8-30kW) and for industrial markets like power supplies for servers and welding tools. “Several top PV inverter companies are now in production with our JFET, and many others are looking at new product development for introduction in the next 12-18 months,” says president and CTO Jeff Casady.
“Cost is decreasing rapidly,” he argues. “Our first transistors were 10X higher than silicon, but they’re now down to 2X-3X higher, while at much lower volumes than silicon. We expect they’ll be only 20%-30% higher in 2-3 years.” And SiC costs have plenty more headroom to come down from ramping volume, as current run levels are extremely low relative to Si run levels.
Suppliers also note that the higher efficiency of the higher cost SiC devices can mean lower total systems cost. Since the semiconductor is only a small percentage of the total bill of materials cost of a 15kW central PV inverter, but can bring a 7X-10X reduction in switching losses, it can potentially reduce the size and associated metal costs of the magnetics for filtering and the heat sinks by perhaps as much as a third.
SemiSouth designed its SiC devices for low-cost production, introducing a trench structure similar to those used in silicon to SiC to reduce die area, and using a self-aligned patterning technology to define both the source and the gate at once at the first lithography level to reduce mask steps. It’s currently producing on 4-inch wafers with 6-inch and 8-inch tools, but expects 6-inch wafers to be commercially available by 2013, and run on the same tools. “Six-inch wafers are 18-24 months away--they’ve been ‘demo-ed’ by all the major suppliers,” says Cassady. He noted, however, that it remains a “chicken and egg” problem between having sufficient volume demand to support moving to the larger wafer size, and having a larger wafer to bring down costs to spur increased volume demand.
Performance can also be further improved by development of better packaging solutions at both the discrete and the module level for high temperatures and low inductance.
The company is also seeing some initial demand from consumer products, from audio amps to LCD televisions.
Major Improvements Possible in Silicon Too
Don’t count silicon out yet either. Improvements to super junction silicon processes may have potential to extend performance to higher voltages as well. Among the several interesting recent announcements of new approaches to such devices on silicon, IceMOS Technology Corp. says it is using MEMS deep etching technology to make 400V-700V MOSFETs with only a single epi layer instead of the usual multi layers. Manufacturing partner OMRON reported at last week’s MEMS Executive Congress that the first generation device with 17:1 aspect ratio trenches is in volume production in its MEMS fab.
POWER SEMICONDUCTOR TECHNOLOGY
November 17, 2011 — 8:30am (U.S. Pacific time)
To meet growing member interest in power semiconductor technology, SEMI will host a webcast on Thursday, November 17, at 8:30am (U.S. Pacific time, 5:30pm central Europe) time. Webcast is free for SEMI members and $100 for non-members.
- Yole Développement’s Philippe Roussel will discuss how wide bandgap technologies will drive the demand for new substrates and dedicated process equipment.
- Marianne Germain, CEO of imec spinoff EpiGaN, recently funded by Bosch’s venture group, will update on GaN on silicon technology issues and market prospects.
- SEMATECH’s Richard Hill will discuss issues and learnings from his research group’s work making III-Vs and III-Ns on silicon on a silicon line.
As high-voltage wide-band gap technologies begin to impact the power electronics industry, substrate suppliers have made tremendous progress to provide optimized wafers of SiC or GaN, points out Roussel. SiC is now available in 6” with a close-to-zero defects and GaN will likely enter into mass-production in 200mm diameter and several µm-thick on silicon in the next couple of years. To reach such specs, equipment makers are developing variations of their core Si-based processes dedicated to these exotic materials. Deposition will move from CVD to MOCVD and HT-CVD for both GaN and SiC, dicing will be adjusted for such hard and brittle materials, wafer handling & bonding will adapt to thin layer transfer, laser technologies will develop techniques for lift-off.
The webcast is no charge for SEMI members and $100 for non-members.
November 8, 2011