Saturday, April 27, 2013

Circuit Design for Reliability

By Sam Sangani

As gate oxide thickness and dimensions of scale shrink in integrated circuit design, reliability problems occur and need to be considered early in the design process. Some of the more problematic issues include negative bias temperature instability (NBTI) and hot carrier injection (HCI). NBTI is a critical factor in PMOS devices and leads to current degradation, yield loss, and functional failure of integrated circuits. HCI has primarily affected NMOS devices, but today it is also a concern for PMOS devices. HCI is caused by hot carriers in the gate oxide that lead to oxide damages, which manifest themselves as current degradation, Vt shift, leakage current increase, etc.

Over time, both NBTI and HCI degrade device currents and will cause failures in integrated circuits. Circuit designers need to consider these reliability effects in the early stages of design to make sure there are enough margins for circuits to function correctly over their entire lifetime.
HCI and NBTI introduce a threshold voltage increase for the MOS. This may be a real issue for mixed signal applications. There is also a gm transconductance variation. This characteristic changes the gain of transistors, which may not be expected by analog designers.

With HCI and NBTI circuit simulation, designers can detect and locate potential issues. Because HCI is dependent of the horizontal electrical field in the channel, designers can improve the robustness of the devices by increasing their length. There is also an exponential decrease in hot carriers with a decrease in supply voltage. Designers can change the bias conditions of the devices where the issue is found.

NBTI problems are more difficult to fix. Designers can check voltage overshoot to avoid the damage caused by NBTI. They may decide to increase capacitive loads, increase the transconductances, or reduce the supply voltage of the function to reduce NBTI susceptibility.

Designers should make it a priority to study the IO blocks of their designs. Creating robust HCI/NBTI circuits is a new challenge for digital/analog designers.

Designers must need to know to design for reliability and they should be educated on additional reliability analyses. The value is the reduction of failure and redesign costs.

Thursday, April 4, 2013

PNC Secures Ventec Polyimide Qualification

Friday, March 15, 2013 | PNC Inc.

PNC Inc. is proud to announce its latest UL qualification of polyimide base materials. PNC has partnered with Ventec USA using VT-901 laminate and VT-901PP prepreg. These high-temperature, high-reliability products expand PNC’s wide product offering and introduces the manufacturer into new industries at a new competitive level. The qualification includes 0.002” inner layer cores and a minimum overall board thickness stack up of 0.025”. The qualification also includes a minimum outer layer copper thickness of half ounce copper while inner layer maximum is two ounce copper. 


PNC President Sam Sangani states,“We are proud to include the VT-901 in our product offering to our military and commercial customers. Ventec has proven to be a high quality partner in both material reliability and service in the U.S. that provides us the competitive edge we always look for.” 


Ventec recently achieved AS9100C certification and manufactures both in China and two locations in the U.S.


About PNC
PNC, an ISO 9001:2008, MIL55110, MIL31032, UL certified, and ITAR registered manufacturer has over 44 years of experience as a quality PCB manufacturer (est. 1968). Its northern New Jersey-based 38,000 square foot facility is a full service engineering and manufacturing site, offering both leaded and non-leaded finish solutions. They offer PCB design, PCB fabrication, PCB assembly, SMT stencils and membrane switches.
For more information,contact PNC Inc. via phone at (973) 284-1600, e-mail:, and
Ventec USA is the US based distribution/QTA manufacturing wing of Ventec Laminates in Suzhou China. For more information, call (978) 521-9700