- Case Studies of
the Technology and Business of MEMS Motion Sensors
A companion study
guide for Foundations of MEMS textbook.
By Chang Liu
The MEMS
technology and motion sensors market is growing rapidly. Motion sensors are
fueling the growth of new consumer electronics devices, which in turn helps the
growth of the MEMS industry. This article provides a review of the technology
and business of MEMS motion sensors – accelerometer and gyroscopes. The
article provides an inside view of the technology/business evolution and device
at world’s major companies in this space – Analog Devices, MEMSIC,
InvenSense, and STMicroelectronics. This document attempts to chronicle major
development history of MEMS motion sensors up to 2010.
This article
provides the following parts.
Part 1: Overview
Part 2: How it
works
Part 3: Story of
the pioneer – Analog Devices (1987-1993)
Part 4: Transition
Era. MEMSIC’s innovation
Part 5: The
InvenSense Story
Part 6: Sensor
Fusion
Part 7: The
STMicroelectronics Approach
Motion sensing
refers to measuring the spatial bearing, linear motion, and rotational movement.
Here are a few examples:
-
A motion sensor in the
Nintendo Wii controller (called Wii mote) can detect the movement of hand and
allows a game player to play simulated games of tennis, golf, boxing, etc.
-
Motion sensors in smart
phones such as iPhone can detect the orientation of the phone with respect to
gravity and change the format of display (landscape vs. portrait) when a user
holds the phone differently.
-
Gyros in iPhones measures
the rotation speed, allowing users to play interactive games such as simulated
car driving – a user simply rotate the device to simulate the action of
turning steering wheels.
Figure 1:
Gyros (rotation speed sensors) allows an
iPhone app JetCar to simulate driving a car by using the phone itself as
a steering wheel.
A review paper by
Prof. Walters provides a very detailed account of the development of
accelerometer. (Citation provided at the end of this section. Do a web search
with the terms “history of accelerometer walters” to find the article). It
is believed that the first accelerometer was made in 1920. The first devices
were based on resistance-bridge of carbon resistors. This device weighted a
pound. Later, around 1938-1941, bonded metal resistance strain gauges are
developed. However, such devices suffer from signal-to-noise ratio issues.
Later, piezoelectric accelerometers were developed. Such devices were
used in vibration monitoring for space and air force programs.
Around 1960 Walter Kistler established Kistler Instrument Company to
commercialize piezoelectric sensors. Endevco was formed in 1947 in Pasadena,
California and commercialized accelerometer in 1951. Endevco focused on
microminiature, high shock, high temperature accelerometers. It also pioneered
diffused semiconductor strain gauge in 1967.
Around 1960-1975,
a number of companies start to take advantage of diffused silicon resistors for
acceleration sensing. These include Fairchild, IC Transducers, Kulite, and
National Semiconductors. Kulite was founded in
1959 as the first commercial source of bare
silicon strain gages. National
Semiconductor was founded in 1959 by Dr. Bernard J Rothlein
after leaving the Rand Corporation (which is founded in 1910 as the Sperry
Gyroscope Company by Elmer
Ambrose Sperry). In 1982, National Semiconductors exited the sensors business. Around
1983, a new group of sensor companies were formed, after the bulk silicon
micromachining process development. These
companies include IC Sensors (1983) and Nova Sensors (1985).
Before 2006, MEMS
motion sensors were exclusively developed for the automotive market (crash
sensor). The typical volume demand is on the order of tens of millions per year.
In 2006, the five major suppliers of accelerometers are Freescale, Analog
Devices, Bosch, VTI, and Denso. The leader of automotive MEMS is Bosch, with
overall revenue of $457M (M means million) in 2007 and $429M in 2008.
The MEMS sensors
business was already a business in 2006. However, it is about to get bigger. In
fact, it is predicted to grow so fast that it will overtake the current MEMS
revenue leaders – Texas Instrument DLP and Hewlett Packard ink jet printer
heads. Why?
In 2006, three
things happened:
-
Low cost of MEMS: the
MEMS field, after over 15 years of active research and production, is finally
able to make motion sensors for less than $1 each;
-
Growing consumer
electronics (CE) market: the CE market exploded, with innovative products such
as gaming, smart phones, etc. This is the result of multiple factors, including consumer
habit. The Internet infrastructure is fully innovated and people’s use of
Internet starts to change (Web 2.0), making portable CE devices highly practical
and desirable. Consumers appetite for new electronics gadgets increased
dramatically.
-
CE and gaming
manufacturers seek differentiation and growth. The CE devices need new
human-computer interface (HCI) devices because of their small sizes. Traditional
mouse and keyboard are no longer suitable for such platforms. Traditional gaming
companies also enter stagnant growth and wants to have new game titles in their
business pipelines.
2006-2008 was a
turning point for MEMS industry, because of the booming of smart consumer
electronics and mobile electronics, which themselves are contributed by the
maturation of microelectronics industry (CPU, hard drives, memory, display). The
success of motion-based products – Nintendo Wii (released Nov 19, 2006), Apple
iPhone (January 9, 2007), and Google Android based smart phones (released Nov 5,
2007), changed the landscape of MEMS motion sensors.
(In fact, these phones changed the landscapes of MANY industries). Apple
iPod becomes the first smart phone product to use gyros. However, the iPod only
opens up people’s mind about the potential market.
Android phones and future generation of smart phones have much bigger
consumer followings. As the price of some MEMS sensors dips below a dollar,
every smartphone vendor is scrambling to match Apple's sensor complement.
Even in a
generally favorable climate, it still takes tremendous vision, technical skills
and courage to succeed. Companies that took advantage of the CE market boom,
innovate boldly in time, and bet heavy on the trend, starts to become leaders.
For example, in 2008, STMicroelectronics, a company that only started to make
accelerometers in 2006, takes a lead in accelerometers for consumer electronics
market. By September 2010, ST has made over 850 million accelerometers and
gyroscopes!
2008 is also the
same year that sales from CE outpaced automotive applications. The sales are now
driven by smart phones. Automotive applications account for 40% of global
accelerometer revenue in 2008, down from 78% in 2006. In the same period, the
revenue from CE applications of accelerometer rise from 22% to 58%.
The growth of CE
will lift revenue of MEMS field in general. Global revenue for MEMS devices in
cell phones will increase to $1.3b by 2012, up from projected $1 b in 2011, $
821 m in 2010 and $299m in 2007. The MEMS-for-cell phone market is expected to
be $2 b in 2015.
Compared to
accelerometers, gyroscope is a new entry. The gyroscope market is growing fast
in a number of application segments. In addition to automotive electronic
stability systems and GPS receivers, MEMS gyroscopes took off in the consumer
segment around 2007, including computer game controllers (e.g. Nintendo Wii),
motion-user interfaces in portable communication devices and image stabilizers
in camcorders and digital cameras. Analysts expect the total available market
for MEMS gyroscopes to grow from $400 million in 2006 to more than $1.2 billion
in 2012.
The price drop is
significant, and the application volume increased. A major catalyst for the rise in accelerometer sales is
pricing. The price of accelerometers goes below $1 in 2008, making it attractive
for a large number of products. Pricing and volume is a chicken-egg problem. Pricing
and volume, which is the chicken and which is the egg?
A happy marriage
between MEMS and CE goes like this: because MEMS is cheap enough, CE vendors
starts to incorporate them in units – the units are large volume demand, very
well suited for the MEMS industry. In fact, MEMS has a difficult time dealing
with small volume and high cost – high volume CE application seems to be a
natural fit. The large demand
drives down the price, which further make MEMS more suitable, and make more CE
vendors and consumer want more MEMS products. On paper, having pressure for unit
pricing is not good economics for the MEMS industry. Many MEMS companies would
secretly admit they love to make more money per unit. However, the price drop
opens new, often unexpected market and in turn grows the field in previously
unestablished new application arena.
It is fair to say
that the MEMS field and the consumer electronics field is symbiotic – mutually
beneficial and growing together.
The dynamics
between MEMS chip manufacturers, chip packaging factories, and system
manufacturers are blurring. The line between electronics and MEMS is blurring.
Sensors that draw
low power and have built-in intelligence will be major trends in future. MEMS
Chips are becoming more circuit and computing oriented, whereas IC chips and
computers are increasingly becoming MEMS-augmented. In the next five years, the
following trends will fully play out:
-
MEMS foundries will
mature and able to handle large volume production of complex products;
-
MEMS will become more
intelligent by incorporating growing degree of circuit sophistication;
