Failure analysis

Failure analysis (FA) entails vast analytical methods and techniques to understand issues that may occur in the manufacturing or application of TI products. Our FA engineers or analysts are equipped to address the complex process, as they are proficient in design, process, assembly and test, and applications, with deep knowledge of physics, electrical, chemical and mechanical engineering.

TI is equipped with state-of-the-art instrumentation and engineering expertise to understand and resolve problems through semiconductor and packaging analysis. Analysis laboratories are available globally to support customer returns, reliability failures, manufacturing fallout and design. These labs include a number of tools that are used for unit analysis, process characterization, destructive physical analysis, and construction analysis. Our FA sites operate autonomously, but in partnership across TI sites around the world to share information and resources.

Failure analysis process

TI’s FA process discovers electrical and physical evidence to clearly identify the cause of failure through straightforward but sophisticated analytical measurement systems, bench top equipment, and a range of other techniques. Using appropriate equipment and work processes, the location of the failure cause is determined, isolated on the die, and physically characterized. The FA team then collaborates with other engineering disciplines (product, test, design, assembly and process) to move analysis forward. Progress, results and conclusions are communicated to internal and external contacts supporting the processes, to implement changes that limit and/or eliminate the cause of failure.

Information review, failure confirmation

Customer reported failure documentation is crucial for efficient FA, and must go through the TI customer return process, which helps provide a clear and detailed description of device history, usage, characteristics of the failure, and any analytical findings prior to returning the device. This information will help the investigation and ensure resolution in a more timely matter.

The minimum set of background information that a customer should include when reporting a failure includes:

1. Component handling prior to receipt at TI. Precautions should be taken when removing and handling components to ensure that electrical or physical damage does not occur and package testability is maintained.
2. Failure history and failure rate at the customer site. Is this a new product or have any changes occurred in this time frame?
3. Application conditions under which the failure occurred. Can a customer schematic be sent to TI?
4. The application’s failure mode and how it relates to the returned component.

The FA team reviews TI’s historical databases to provide additional perspective and guidance. After a review of all information, an initial analysis strategy is formed. Confirmation of the reported failure mode should occur prior to further analysis steps. Good correlation to reported failure modes insures confidence in any subsequent findings. Bench test equipment, such as curve tracers or application-based bench testing, and production-level automatic test equipment ('ATE') may be used for electrical characterization.

Non–destructive testing

FA in itself is reverse engineering and can be destructive to the returned product. Since the package will be at least partially destroyed to expose the die, non–destructive techniques are carried out first to observe package or assembly-related failure mechanisms. The most common techniques TI uses are acoustic microscopy and radiographic (XRAY) inspections to look for internal assembly or molding anomalies.

Internal inspection

TI carries out an internal optical inspection to check for any obvious assembly anomalies or wafer fabrication issues. Re–testing is also recommended to determine if the failure mode has changed.

Global isolation

In many cases, TI’s internal inspection will not reveal an obvious failure mechanism. Depending on the technology and level of testability, the FA lab will utilize one or more technique to isolate the failure site. The majority of these techniques attempt to observe the properties of the failure site, such as thermal dissipation or photon emission.

Local isolation

Locally isolating the failure site to a block or single node on the die is a common, but critical step. However, it can also be time consuming. In most cases, extensive internal probing is required and is generally iterative, with deprocessing, layer by layer. Deprocessing is the process of removing one layer of the die at a time, which may entail wet chemistry, dry plasma etching, and mechanical polishing techniques to reveal the underlying structures. The proper techniques are critical due to the destructive nature of the process and potential loss of vital information. During the process, the FA analyst performs probing and other specific techniques to highlight potential anomalies. From a probing standpoint, the use of layout/schematic navigational tools and a focused ion beam (FIB) are employed to assist in component and circuit isolation.

Analysis of failure site

Once a potential site has been determined or revealed, documentation and analysis is conducted. Further analytical techniques are employed depending on whether the morphology or material composition is required.

Report conclusion

Once analysis is complete, work is documented in a written report stating the relationship of the physical anomaly to the failure mode, and including sufficient documentation for root cause analysis.