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Size is everything

Size is everything

The world's first 300mm analogue fab should be a bonus for system designers.

The launch of the first high capacity 300mm analogue wafer fab demonstrates how essential the integration of analogue, digital and power technologies at cost effective price points has become to the growth of the electronics industry.

Driven by increasing demand for sophisticated and integrated analogue components, the manufacturing capacity of Texas Instruments' wafer fabrication facility in Richardson, Texas – known as RFAB – will extend the capabilities of its analogue technologies into new applications and systems.
RFAB is the world's most advanced analogue manufacturing facility.

The number of analogue chips that can be produced on a 300mm wafer is more than double that of a 200mm wafer; the dominant wafer size in other analogue fabs. In addition, according to Gartner, the transition from 200mm to 300mm wafers can save approximately 30% in production costs.
This increased ability to manufacture cost effective analogue chips will meet increasing demand for such components from applications ranging from smartphones and netbooks to computing and medical systems.

Analogue innovation
Analogue processes are generally fairly complex because of the need for active and passive devices to have good performance and, in some cases, optimised performance. These requirements do not leave much room for harmonising between process steps (for example, double use process features for different devices). As a result, there is great opportunity for an improvement in analogue R&D in order to get the required performance from the simplest flow.

In addition, RFAB will allow devices to be created on smaller lithographies if that is appropriate. Smaller lithography is not necessarily a great thing for analogue because it is expensive relative to the small volumes for most analogue products. And, because analogue products have a very long life span, this requires a facility that can support them for decades in many cases.

Unlike digital semiconductor process technologies, where Moore's Law is often cited as the standard measure of advancement, analogue innovation is derived from a broad range of factors. It is the combination of these factors taken as a whole in any one device that generates the value that system designers look for in analogue chips. The combinination of RFAB's high manufacturing capacity with TI's proprietary LBC7 linear bicmos process technology means the company will be able to meet growing demand while extending the performance and cost effectiveness of its analogue components.

Demand for devices fabricated on the LBC7 process – which has already been deployed in three fabs – continues to expand. Capable of integrating a variety of analogue, digital and power components in one chip, LBC7 is a modular 0.25µm 40V mixed signal process technology which, at its most basic, can provide ldmos power devices with voltage scaling from 5V up to 40V. However, more complex devices – such as 0.25µm bipolar-cmos-dmos (BCD) technology with 3.3V and/or 5V digital/analogue cmos capabilities – can be created.

LBC7 not only offers a diverse range of features for analogue and power products, but its adaptable process flow can also be configured for simple chips or more complex custom mixed signal devices with fairly large digital cores. Quite simply, LBC7 can produce a range of analogue products and, in particular, is adept at producing cost effective power management devices.
Since it is a modular process, LBC7 offers several options, depending on the power device architecture and the ratio of the analogue and digital content. Different combinations of the LBC7 process can be deployed to meet the particular needs of an application, such as low cost, high power or precision, and – even in the simplest process flow – passive analogue components such as poly and diffused resistors, OTP trimming and capacitors.

Other active analogue devices, such as high voltage drain extended cmos, diodes and bipolar transistors, are supported. LBC7's various flows can accommodate up to three levels of standard aluminium interconnect, with the option for thick power metals.

The versatility of LBC7 and the increased manufacturing capacity of RFAB are likely to give system designers a range of solutions for their next generation applications. In particular, implantable medical diagnostic and monitoring systems provide an example of where new analogue processes can make a difference.

Because LBC7 enables competitive solutions to be created with outstanding performance, RFAB will enable an increase in TI's competitiveness and ability to meet the capacity demands of its customers. Moore's Law will continue to add an advantage where there is a need for high digital to analogue content and will also offer some scaling ability for analogue devices. The competitive nature of analogue will drive R&D to new innovation for improvement in silicon device technology and hence drive process integration innovation for less complex manufacturing process flows. To go along with this there will need to be continued innovation and advances in packaging solutions to complement and add diversity.

Extending technology's reach
One of the most critical – and most frequently ignored – innovations associated with any technology is its cost effectiveness. And it is its cost effectiveness that frequently leads to a technology's rapid and widespread adoption in the marketplace. RFAB's greater production capacity, enabled by the transition to 300mm wafers, will drive down manufacturing costs and improve the cost effectiveness of the devices produced there.

In addition, the fact that TI has obtained the equipment for 20% of the cost of state of the art 90nm equipment will add significantly to RFAB's cost effectiveness.
Because RFAB is the first 300mm fab for analogue chips, some 200mm analogue fabrication processes will need to be transitioned to the new wafer diameter. Fortunately, moving designs from 200mm to 300mm wafers does not involve extensive R&D; migrating most processes to 300mm wafers only involves an optimisation of the 200mm processes to match the larger wafer size.

For example, in order to employ the same photoresist material for producing the patterns on 300mm wafers, the viscosity of the 200mm photoresist material must be altered. This will involve a characterisation and qualification process of the new material as well as optimisation of RFAB's lithography tools to the photoresist's different characteristics.

A flexible manufacturing strategy
RFAB and the LBC7 process are manifestations of the TI's flexible manufacturing strategy that is moving beyond the old thresholds of performance and cost effectiveness for analogue chips. This strategy – unique amongst broadline chip manufacturers – calls for a blending of internal fabrication capacity for analogue technology with external foundry production for digital technology. In addition, the ready availability of external analogue production capacity for periods of exceedingly high demand also helps maintain the edge in cost effectiveness that TI's chips have achieved.

In the future, TI's analogue fabrication capabilities will continue to focus on faster speeds, higher precision, lower power consumption, smaller sizes and increased functionality so the end systems enabled by these analogue chips will be among the most competitive in the markets they serve.

Author
Bob Eklund, RFAB process integration and product engineering manager and Taylor Efland, TI's chief technologist, power management.

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