When DB HiTek licensed Weebit ReRAM, we mentioned that the ReRAM (RRAM) will be implemented in their 130nm Bipolar-CMOS-DMOS (BCD) process. We also mentioned that a BCD process is ideal for mixed-signal and high-voltage designs in applications such as consumer, industrial, automotive and IoT devices.
But what is a BCD process, and why is it a good fit for these applications?
A quick look at the Swiss Army knife
Perhaps the best way to start talking about BCD is with an analogy. So, let’s take a quick look at the Swiss Army knife! This well-known tool was conceived in the late 1880s, when the Swiss Army decided to provide soldiers with a folding implement that would enable them to open cans of food and disassemble their service rifles – which needed a screwdriver. Thus, the Swiss Army knife – the first folding pocket multi-tool – was born. It combined three functions into one valuable tool that would make the lives of soldiers much easier.
In 1896, Karl Elsener redesigned the knife around a spring mechanism that enabled tools to attach to both sides of the handle, making it possible to increase the number of tools on the knife. Since that time, the Swiss Army knife has evolved to include many other tools, but the original premise remains, and recruits in the Swiss Army still receive a knife when they join up. You can read more about the history of Swiss Army knife on the Alpenwild travel site.
Above: A typical Swiss army knife integrating various tools in one platform
BCD: A hybrid process for power management applications
Like the Swiss Army knife, BCD is a multifaceted platform with versatile characteristics. BCD was originally built as a hybrid technology platform based on advances in several areas over several decades, and it continues to evolve today.
After the introduction of integrated circuits (ICs) in the 1950s, various substrate technologies emerged, starting with Bipolar analog focused processes in the 1950s. In the 1960s, we saw the introduction of Complementary Metal-Oxide-Semiconductors (CMOS) for digital processing. In the 1970s, Double-diffused Metal-Oxide-Semiconductors (DMOS) transistors were introduced for power functions and high voltage elements.
Throughout this time, end products and their analog and digital components continued to grow in complexity, often with different voltage and power requirements within the same product. Processors, communication, and other digital ICs focused on CMOS substrates, while analog focused on Bipolar, and power designs were more likely to use DMOS. However, over time, the need to have a mixture of these in the same design grew, presenting a challenge in integrating mixed-signal and high-voltage designs on a single die.
In 1985, the manufacturer SGS (now STMicroelectronics) introduced BCD (Bipolar-CMOS-DMOS) technology which combines Bipolar, CMOS, and DMOS technologies all in one. BCD makes it possible to combine three different types of transistors – analog, digital and power/high voltage– all on the same silicon die, leveraging the strengths of each type of transistor. The result is the ability to design and fabricate a chip that can handle various voltage requirements and power levels.
Each of the technologies in BCD provides distinct advantages. For example, DMOS makes it possible to accommodate a wide range of voltages, so it can be used for high-voltage or low-power applications. The inclusion of CMOS enables designers to integrate digital blocks while optimizing power efficiency. With Bipolar transistors, a design can manage large currents for power-intensive use cases.
There are also benefits based on the combination. This includes enabling higher integration density for end solutions with a more compact footprint. This is like the Swiss Army knife, which puts multiple functions into one tiny instrument that fits in your pocket! System integration also enables solutions with greater energy efficiency, improved system reliability, and reduced electromagnetic interference (EMI).
Where does BCD make a difference?
Because it enables integration of analog components, power transistors, and digital logic in one chip, the applications for BCD technology are broad. It is most applicable where there is a need for power efficiency, thermal stability and high-voltage capabilities. BCD is also used where it makes sense to integrate various components on a single chip.
Applications include power management ICs (PMICs) where it helps reduce standby power and increase efficiency and system reliability. Many of today’s power management units use smart PMIC designs where the PMIC is integrated with a microcontroller (MCU) on one die. This enables them, for example, to optimize the charging speed based on the state of the battery, extending battery life. You can read more about this in our article, “The Power of ReRAM for PMICs.” For PMICs, BCD leads to performance, security, power and cost advantages.
Other key applications include motor control in industrial automation and robotics, display driver ICs and wireless charging. It is also essential in automotive applications, especially where analog (motor control) and power management (for smart charging) are integrated in areas such as body electronics (e.g., lighting, power windows, door locks, mirrors, windshield wipers, etc.), powertrain control, and electric vehicles.
Since the 1980s, ST and many other industry players have continued to develop techniques to make BCD processes more effective alongside advancements in end products, manufacturing techniques and process nodes. Because of its broad applicability, developments have continued to maximize separately for high power, high density and high voltage. This work continues, and today many major foundries and IDMs offer their own flavors of BCD.
NVM for BCD
Non-Volatile Memory (NVM) is broadly used in many BCD and high-voltage designs. At the minimum, such NVM is used to store calibration and trimming information, on top of some ID/security data. More recently, as we see BCD designs integrating further resources onto a single die, such NVM can be used also for code storage – especially for designs that integrate a microcontroller. This enables cost-effective support for updates in the field, secure data storage, and diagnostic capabilities, which enhance the flexibility, reliability, and safety of such devices.
A high-quality BCD process requires precise calibration of the front-end-of-line (FEOL) in the manufacturing process, which is very sensitive to variations. Typical NVMs like flash are integrated in the FEOL, making their integration into a BCD flow very difficult and costly. In addition, this impacts the design’s transistors which must take NVM integration into account, making the design less than optimal. Think about integrating new tools into the Swiss Army knife. Depending on their size and shape, everything in the knife may need to be shifted around to make room for the new tools (this is why there are today more than 100 versions of the knife!).
Weebit ReRAM offers significant advantages because it is a back-end-of-line (BEOL) technology which doesn’t require any process tuning and doesn’t impact the transistors in the front-end-of-line. Like the toothpick in the Swiss Army knife – it doesn’t influence the other parts of the knife. ReRAM also requires fewer masks than flash, making it less complex and cheaper to manufacture.
Many companies designing power management and high-voltage designs are looking to enjoy the advantages of embedded ReRAM – including low cost, low power, easy integration, and proven excellent retention at high temperatures. At Weebit, we’re working with foundries like DB HiTek to make our ReRAM IP available in their portfolios. We recently taped-out our module in DB HiTek’s 130nm BCD process.
And while we can’t open our customers’ cans and bottles for them, we can make their lives easier by providing a low-power, cost-effective and high-density NVM that can help them save cost and power and reduce the complexity and size of their solutions.
