Introduction to semiconductor quality and reliability—Part I

Semiconductor devices are the core of all electronic products we use today, be they phones, radios, computers, toys or cars. For the most part, this industry and its products are embedded and hidden from view. As each year goes by, semiconductor devices are becoming smaller and thinner, using less energy and offering increased computing power. These strides in technology have fueled a boom in new products that capture the consumer's imagination: 60-in. televisions, razor-thin cell phones, and computers that double in power every six months. This industry is characterized by very high-quality standards paired with rapid new technology introductions. A missed design cycle often means no growth and loss of market share.

During these times of change, quality, reliability, and improvements continue to be important. The most demanding customers and the highest expectations for quality are found in the semiconductor sector. Reliability and quality of product, process, or service is vital to any successful enterprise. In today's highly competitive business and industrial environments, it is mandatory that top management are fully conversant with new thinking, techniques, and developments in the field so they can take a competitive lead – and then maintain it.


What is Quality?
Quality is typically defined as the reduction of variability around a target so that conformance to customer requirements and expectations can be achieved in a cost effective way. Alternatively, it is the probability that a component will perform a specific function under specific conditions for a specific period of time. Failure rate is measured in Defects per Million (DPM) or Parts per Million (PPM).

It is important to note that the meaning of quality differs depending upon perceptions and circumstances. For example, quality has a different meaning when comparing a product with respect to a service.  The meaning of quality is also time based or situational.


Various Meanings of Quality:

• Quality for fitness of USE:  the product or service performs as intended

• Quality of Meeting Customer Expectations: satisfying customer expectations with respect to the quality of a product or a service.
• Quality is superior to competitors: the quality of products and service are superior to the company’s competitors.

Table 1.

Methods of Quality Implementation:

• Quality of Design versus Quality of Conformance
• Quality of Planning, Control and Improvement

 

What is reliability?
Reliability is defined as the Intrinsic Failure rate over time and is measured in FITS (Failure in Time per Billion Device Hours). Traditionally, the measurement of electronic failures has been straightforward. If a person assumed all failure rates were constant, as they might be in a large system or machine, then a MEAN time between failures (MTBF) would be expected. In contrast, most integrated circuits, including TriQuint GaAs devices, follow a lognormal distribution, which rarely approximates a constant rate.

Generally, semiconductors have a very low wear out failure rate early in life, and then have increasing failure rates as they wear out. At a point when about half of the devices fail in a group of circuits, the failure rate begins decreasing again. A very small part of an IC's population may fail early in life. These early failures have been associated with manufacturing or assembly defects. Early failures are sometimes called "infant" failures. As semiconductor reliability improves and more samples are stressed, early failures become easier to detect and eliminate.

Reliability Objectives:

• Meet customer expectations
• Meet customer demands on mean time to failure
• Eliminate reliability concerns prior to qualification/ramp
• Allow more aggressive performance without increasing risk of failure