Automakers are discovering that speed and comfort are not the only things they should work to improve. They are rushing to create breakthroughs by incorporating electronics and intelligence to automate driving in order to improve efficiency and safety. Statista, a research and statistical data company, predicts that electronics as a percentage of total manufacturing cost will increase dramatically in the coming years (Figure 1). With semiconductor advancement at full speed, what will the future look like?
What is ADAS?
Advanced driver-assistance systems (ADAS) are based on the human-machine interface (HMI) concept to automate certain driving functions such as auto-braking, auto-speed adjustment, and lane departure warnings. ADAS will increase comfort and convenience, but its primary goal is to improve safety by eliminating human errors. To that end, the U.S. Department of Transportation’s National Highway Traffic Safety Administration (NHTSA) is requiring that vehicles add additional safety features to assist driving.
ADAS fundamentally depends on various sensors, including light detection and ranging technology (lidar), radar, and ultrasonic to detect nearby objects. Radar using electromagnetic waves and ultrasonic using sound waves are familiar to most. Lidar is relatively new and is being tested by most automakers. It relies on light to detect an object in front of the car or on the road. Lumina, a leader in lidar sensors, has introduced a device based on the 1550 nm wavelength technology. It is able to detect a dark object 600 ft away at 75 mph. Currently, ADAS are being deployed in a range of new car models, which typically includes one or more sensor types. A few years ago, I sat in a demo vehicle equipped with ADAS. The auto-braking feature worked so well, it was immediately obvious that no human being could react that fast if an object suddenly appeared in front of the vehicle, at night, with no warning.
Semiconductor Advancement Is Driving the Future
A sensor is a module or a semiconductor device which converts physical parameters such as motion, heat, weight, moisture, as well as pressure or light into electronic signals, and ultimately to digital data. Three types of semiconductor advancements will enhance the development of sensors and the future of driving. They include:
- Continual development of MEMS (micro electro-mechanical systems)
- Advanced silicon packaging
- 3D silicon
How MEMS Integrate More Electro-Mechanical Functions in One Small Package
Micro electro-mechanical systems (MEMS) technology has made incredible progress in the last 20 years. Previously, multiple chips were used to do sensing and signal conditioning. Now, these two functions can be combined in a single MEMS chip, and some processing functions will soon be integrated as well. The end result will be smaller packaging with a lower cost overall. With this progress comes many new commercial MEMS products that are available for use in a wide variety of automotive applications. This includes motion sensing, which enables the chassis to give feedback to the engine to provide a more comfortable drive, airbag deployment systems in case of collision, detection of oil pressure in the transmission system, and so on.
Advanced Silicon Packaging Integrates More Chips
Package-on-package (PoP) techniques are used to stack two chips together, such as flash memory and a processor, to achieve more functions using the same real estate. The challenges of implementing PoP include mastering the precision assembly technique required during the manufacturing process, and finding suppliers for the PoP silicon components. The payoff, however, is substantial, with even smaller size components for automotive applications.
Building 3D Silicon
Traditionally, silicon manufacturers tend to shrink the die size to squeeze more chips in one wafer. But making a smaller die is becoming more and more difficult. It is one thing to move from 22 nm to 14 nm, but moving from 14 nm to 7 nm is proving extremely difficult. That is why GlobalFoundries, a large silicon fabrication facility, has decided to stop pouring billions of investment dollars into the 7nm project.
So what is the alternative? By building 3D silicon using a bigger die size, 20 nm technology, and silicon foundries can put multiple chips in the same package. The concept of a 3D chip is not difficult to understand, but actually building them is far from simple. There are thermal considerations and yield issues to wrestle with. One way to design 3D silicon is to move certain elements, such as a capacitor in a flash memory chip, to the top of the cell instead of placing them side by side. Another approach is to use a thinner wafer and stack multiple chips on top of each other, sometimes referred to as chip-on-chip (CoC). The end goal is to create more functionality and higher capacities in smaller packages, enabling low cost, and high integration components for automotive applications.
How Integration Helps TDK Create a Tiny 6-Axis Sensor
TDK, a manufacturer of 6- and 7-axis gyroscope silicon, provides a great example of how the integration of functions can reduce silicon packages. Traditional gyroscopes can be greater than 500 mm³ for a single axis device. TDK-InvenSense’s MEMS technology, the IAM-20680, is able to integrate the accelerometer and gyroscope into the same die. By combining three gyroscopes and three accelerometers in one package, TDK is able to create the smallest automotive sensor on the market at less than 7 mm³.
Future Trends
Where will these semiconductor advancements lead us? In the future, silicon will be able to incorporate many functions such as communication, control, and sensors in a single package. These small package and low cost smart sensors will bring us new possibilities and safer driving. Here are some examples on how the future is limitless:
- Mini airbags can be deployed dynamically. Right now, most vehicles have limited airbags installed and are only deployed when the car senses the shock from a collision. With high-performance smart sensors, mini airbags do not need to be installed in one fixed location. Rather, there can be a bank of airbags installed in multiple locations of the vehicles, including the top, ready to be deployed. When a collision occurs, mini airbags will be sent to the location where the most impact will be felt, and space will be filled with mini airbags to prevent the human body from hitting hard objects.
- Vehicles may have a new balancing act. The vehicle can be installed with moving weights or bars. When the vehicle is hit from one side, for example, the weights will be shifted to balance the vehicle to prevent it from rolling over.
- The ultimate goal is collision avoidance. With sensors installed around the vehicle, the vehicle will be able to detect the movement of surrounding objects and control the movement of the car including speeding up and slowing down to prevent, short stops or collisions. Additionally, besides providing lane departure warnings, the vehicle will provide corrections to avoid being hit by another approaching vehicle.
- V2V communication protocol will be installed in each vehicle. V2V research has been conducted for many years, and high-performance chips with low cost memory will enable V2V protocols to be pre-programmed and ready for automakers to install. This will further increase driving safety by allowing vehicles to warn each other of accidents or sudden stops ahead.
