As any engineer who has spent hours mulling over a malfunctioning piece of hardware can attest, nothing lasts forever. Years ago, finding defects wasn’t so complicated. But now, more features, complex packaging, and smaller nodes in modern technology make identifying defects more difficult. As a result, some devices never make it out of the lab— and others die in the fab.
The race to determine why or how a device failed is a story as old as time. Engineers are in a perpetual state of testing and recreating problems in the lab, instead of pursuing innovative work. While many factors can cause chip problems, it’s helpful to know the most common ones engineers can expect to find.
Open circuit defects
Open circuit defects can take many forms, including cracks or scratches on the surface, improperly etched metal traces, or poorly connected wire bonding. Other defects like improper drilling between metal layers and misalignment between dice are more difficult to find. Often, open circuit faults are a result of improper manufacturing and can lower product yield. As these defects vary in shape, location, and severity, using traditional inspection methods may not be enough to find device faults.
Latent or reliability defects occur when conditions like size or location contribute to die defects. Complex circuitry often has latent flaws that rest in untested areas of the die. These defects can pass electrical tests and “escape” into the field, causing failure later in the process. Additionally, yield or killer defects happen similarly to latent defects. The two differ only in their size and location on the device pattern.
According to Semiconductor Digest, undetected failures like latent or yield defects are the most expensive costs, resulting in millions of dollars in losses per year. When electrical testing is no longer a reliable way to detect latent defects, engineers need other methods to find these defects before it impacts the company’s bottom line.
Electrical over-stress (EOS) occurs when a device is exposed to higher voltage levels than it can withstand. The exposure can be accidental (due to electrostatic discharge or power surges) or negligent (due to misuse of their applications).
In dramatic cases, the damage may be more difficult to find. Detecting faults may require much more advanced techniques. But most times, failure analysts can find excessive currents by isolating heat using precise tools and techniques.
Electrostatic discharge (ESD)
ESD is a subset of EOS. Leakage, contact damage, gate oxide rupture, and resistor-metal interface damage are all forms of ESD-induced damages. These defects often happen when people or other equipment mismanages devices during IC manufacture, transportation, and application. Shrinking chip sizes and high-speed circuit operation, among other factors, contribute to ESD sensitivity.
Detecting ESD can be a common challenge for IC designers. According to Electronic Design, ESD causes more than one-third of the field failures in the semiconductor industry. To reduce ESD failures, IC designers need effective failure analysis (FA) testing and solid circuit protection.
No trouble found
All too often, the root cause is never found. Despite retests, some parts fail for no reason leading to No Trouble Found (NTF) rates, an elusive and frustrating statistic where no defects are found in malfunctioning devices. According to consulting firm Accenture, 68 percent of all consumer returns are characterized as NTFs. If this rate continues, manufacturers and retailers face the risk of huge financial burdens and poor brand reputation.
For chipmakers to stay on top of the industry, effective FA and reliability is critical to everyone down the value chain. Regardless of the cause of failure, it’s important to pinpoint what’s happening and prevent failure recurrence in the future. Partnering with a team of IC failure analysis experts can be the best way to get the knowledge and resources you need without falling into the trap of constant testing and respins.
Ready to ensure the highest quality for your ICs, on time and cost effectively? Contact Talent 101 today to get a needs assessment and talk to a specialist.