By 2012 ST’s MEMS were doing well in consumer electronics, and particularly in smartphones, but the problem Vigna saw was that each of those MEMS design wins lasted only a few months and even though volumes were high and getting higher, more design wins were always needed to replace those in retiring products. What Vigna wanted was additional MEMS design wins in longer-lived products that could command higher average selling prices with less price erosion.
Benedetto Vigna, executive vice president and general manager of the Analog MEMS and Sensors group within STMicroelectronics.
This involved – and continues to involve – developing novel products for ST’s established markets while at the same time developing new markets for adaptions of ST’s established consumer MEMS. In addition there is the hope of developing original MEMS sensors to help foster entirely new markets.
Meanwhile increased competition in the supply of inertial MEMS sensors in the consumer market has impacted ST. There was the loss of some design slots with customers such as Apple as attested to by third-party deconstructions of iPhones. ST, like all Apple suppliers, is tight lipped about where it is design in. But one result was that ST has dropped from being MEMS market leader in 2012, to a distant second to Robert Bosch GmbH (see Bosch pulls ahead in MEMS top 30 ranking), according to market research firm Yole Developpement. A ranking from IC Insights even put ST in fourth position in 2014 (see ST falls to fourth in 2014 sensor sales ranking).
Rise of the microphones
But ST’s rise in microphone supply can be seen as one of the fruits of that diversity planning. ST says it has shipped over 500 million MEMS microphones and has seen its market share go from less than 2 percent in 2012 to about 10 percent of the market in 2014.
ST MEMS microphone market share: Source ST
In terms of opening up applications ST is also successfully adding automotive applications for its MEMS. Market analysis company IHS Inc. has identified ST as the leader in automotive sensors for navigation and telematics, as well as the fastest growing automotive-sensor supplier worldwide in the first half of 2015.
The diversification-into-automotive approach is also being attempted by rival MEMS vendor InvenSense Inc. and is the reverse of the diversification journey taken by market leader Robert Bosch. According to ST the automotive motion MEMS market is currently worth about $1.2 billion annually with a steady compound annual growth rate of 4 percent. Having started in motion MEMS in the cabin for navigation and telematics ST is now gaining passive safety design wins for its sensors in airbag applications. ST is now entering a third phase, with MEMS sensors for the most demanding applications in a vehicle: active-safety applications, such as electronic stability control .
"STMicroelectronics is really capitalizing on two major trends in the automotive MEMS sensor market," said Jeremie Bouchaud, senior principal analyst at IHS. One is that tier-1 automotive suppliers are starting to outsource safety-critical applications such as airbags and electronic stability control. The second is that multiple-axis inertial sensors, originally developed from the consumer industry, are simplifying mounting of units and bringing additional functionality.
Good news for ST but also for its competitors – and so ST also active in other markets.
In terms of developing a new application ST has worked with Intel to develop an infrared "structured light" projector that uses a single-axis micromirror for scanning. This is now designed into Intel’s RealSense vision module used for gesture recognition and depth sensing and intended to be a standard part of personal computers going forward (see Intel selects ST micromirrors for human-machine interface).
SIngle-axis micromirror deployed within Intel’s RealSense. Source: ST, Chipworks
It includes a gold coating on the mirror and one reason ST was able to win the business is that it can also offer the required driver IC in a silicon-on-insulator BCD process that operates in the region of 130 to 170V.
Sandro Dalle Feste, product development manager in ST’S AMS group explained that micro-mirror driving can be done electrostatically or electromagnetically. In essence the first uses high voltages and low currents while the second has low voltages and high currents. In the interests of energy saving the former is preferable.
And ST is also in production for MicroVision and Sony in the MPCL1 laser picoprojector, although this requires either two mirrors or a double axis mirror. The advantage of a laser-based "flying spot" system is that the image does not need to be focused – saving weight and energy – and "keystone" correction can yield a rectangular image on most flat surfaces. And ST provides the processor to perform the image correction.
(Ed note. Chipworks Inc. has performed a teardown of the Sony MP-CL1 that can be found here)
Picoprojectors do have challenges. It is hard for them to be bright enough while staying within the "eye-safe" laser category and while being sufficiently low power for mobile and battery-operated applications. However, Vigna points out that optical MEMS can be used for many as yet undeveloped applications; for beam-steering of automobile headlights, for polymer curing in 3D printing.
ST’s optical MEMS program is not quite at the same state of readiness as the inertial MEMS platform where ST introduced has standardized process platforms such as THELMA, says Vigna. "It’s more, engage with the right partners and then let the market take off," he said.
ST is also ramping up the use of lead zirconate titanate (PZT) as a piezoelectric material in MEMS, Vigna said. PoLight AS (Horten, Norway) a vendor of an autofocus lens for cameras is a lead customer. The TLens (Tuneable Lens) uses a piezoelectric actuator to change the shape of a transparent polymer film, imitating the focussing function of the human eye. Other companies are also introducing piezoelectric materials into their processes to obtain superior sensing performance compared with conventional capacitive sensing, such as Vesper Technologies Inc.
But Vigna says piezo-electric principles are good for actuators, such as inkjet printing, 3D printing or medical applications such as insulin dispensing, but not for motion sensing. "There is not enough profit in motion sensors to develop a new infrastructure," he said.
However, for the actuator applications targeted Vigna reckons ST is in a leading position being able to manufacture piezo MEMS technology on 200mm-diameter wafers and therefore more cost-effectively than most of the competition.
Next: Going gas and environmental
Microfluidic and gas
ST is also a broad supplier of MEMS and is developing microfluidic devices as well as environmental gas sensors. Indeed the company claims to be the only company to offer the "full range" of MEMS sensors and micro-actuators. This includes microfluidics for which ST has worked for many years with Debiotech SA (Lausanne, Switzerland). The insulin Nanopump, developed by Debiotech, industrialized by ST and announced in 2007, was the first use of microfluidic MEMS technology in diabetes treatment.
"The capability is there in microfluidics, but it is a question of priorities," said product development manager Dalle Feste. However, in terms of gas sensors, ST plans to have a volatile organic sensor in the market in 2016 and has carbon monoxide, carbon dioxide and ethanol sensors under development.
For ST the analog MEMS and sensors market has delivered tremendous sales over the last decade however, with intense pressure to reduce costs and therefore die size it has also been a difficult market, particularly in the consumer electronics area. Vigna makes the point that in just the last five years accelerometer die sizes have reduced to a quarter of what they were in 2010.
One benefit of that continual redesign is that there is no imminent need to extend manufacturing or move to 300mm-diameter wafers, he said. And another benefit is that MEMS developed for smartphones and sensor fusion concepts are starting to be picked up across all sectors of electronics; automotive, industrial and medical. The benefits of a diversity strategy are already starting for ST but the best is yet to come, said Vigna.
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