What is a Semiconductor Parametric Test?
Semiconductor Industry Strives to Attain High-Yields for Greater Profit
The semiconductor industry works hard to maintain high yields from their substrates. Parametric testing measures a device's electrical parameters for:
- Integrated Circuits
- Resistors
- Capacitors
- Diodes
- Tranistors
- Inductors
To name a few.
There are many reasons for low yield including malfunctioning equipment, called process drift, and human error. UniversityWafer, Inc. help our clients obtain the highest quality wafers for all their research and production.
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Understanding the Drift Process in Semiconductors
Drift is a term used to describe the motion of electrons 
and holes in a semiconductor. When an electric field is applied to a semiconductor, carriers start moving. Positively charged holes move with the electric field, while negatively charged electrons move against it. The drift process describes the motion of carriers by their constant drift velocity, which takes into account collisions, setbacks, and the direction in which they are moving.
The electrons move from the negative to the positive terminal by drifting. During this process, they change direction because they hit atoms. The electrons then bounce back in a random direction. The applied voltage causes the electrons to drift towards the positive terminal. This process is known as drift transport, and the rate of decrease of the electron concentration in the semiconductor is proportional to the increase in drift velocity. When the electrons move in a straight line, they have the same charge, 1.602 x 10-19 Coulombs (C).
Drift and diffusion currents are both caused by the non-uniformity of charge carriers in semiconductor materials. When the two types of charge carriers are present on a single crystal, they form a p-n junction, resulting in the formation of a p-n junction diode. This process is important in the fabrication of switching devices, which rely on the diffusion of electrons and holes.
What is Parametric Test in Semiconductor Manufacturing?
When we ask "What is parametric test in semiconductor" we are often confronted with many questions. These include what are its types, what are its duties, and how does it compare with Wafer Level Reliability testing. In addition to answering these questions, this article also explores the cost of this test. Let's take a look! Read on to learn more about parametric tests in semiconductor manufacturing.
Duty factors for parametric test in semiconductor
The development of a useful parametric test suite requires understanding the cause-and-effect relationships among process and electrical test parameters. This requires close collaboration between IC designers, process engineers, device integrators, and test engineers. Figure 1 illustrates the interaction between test and process parameters. It applies quality function deployment techniques to define the correlation between process and device parameters. For example, each row represents a significant process parameter; each column represents a device parameter; and each cell ranks the correlation between the two.
The most common uses of parametric tests in semiconductor manufacturing include process control monitoring (PCM) and wafer level reliability testing (WLR). PCM focuses on gathered data rather than stressing the device. The duty factor is also an important parameter when multiple pulses are used for a single test. The pulse width of each input must be measured between the required measurement levels. In addition, multiple pulses must have the same duty cycle and phase relationship to the prime input.
Types of parametric test in semiconductor
Traditionally, parametric test has been confined to DC measurements at the final metal. The trend is shifting to testing at the first metal or subsequent layers. The increasing complexity of integrated circuits at the top end, and the desire to maximize yield feedback, have contributed to the development of these types of tests. Here are some common types of parametric tests:
Parametric tests measure all parameters of the device within specified limits. In contrast, functional testing is limited to a small portion of special test die. As the amount of data continues to grow, functional testing is becoming impractical. In the meantime, parametric tests provide historical data for decision-making. The results of parametric tests are used in production. By identifying the performance characteristics of the product under test, these tests are critical for semiconductor manufacturers.
Today, these tests are becoming more important in semiconductor development and production. Advanced manufacturing processes have increased the need for this type of measurement. With reliable, repeatable measurements, designers can reduce uncertainty in the design process and speed up product development. In this fast-paced industry, every second counts. The ability to test a wide variety of devices at the same time reduces the costs associated with parametric testing. For high-volume production and fast design cycles, Keithley has solutions to meet the demands of semiconductor manufacturers.
Interactions between parametric test and Wafer Level Reliability (WLR) testing
PCM and WLR are statistical process control methods that both collect data and identify process anomalies. WLR testing stresses a special structure on the wafer and measures the degradation it causes. The stress can be so great that it causes the structure to fail, but it does not affect the rest of the wafer. Results of WLR testing can be interpreted based on predetermined stress levels and test times.
The importance of parametric test systems in semiconductor fabrication cannot be underestimated. These automated systems collect and analyze IC electrical data, which can be related to the parameters of the process. A percentage point in yield can cost a semiconductor fabricator $1 to $8 million. Thus, the semiconductor industry controls processes to meet yield targets. However, the variability of yield results is due to errors in batch processing and undetected interaction effects.
Cost of parametric test in semiconductor
The P9002A parallel parametric test system offers high throughput and cost-effective wafer test capabilities. Its software compatibility with SPECS for 4080 series parametric testers means customers can take advantage of existing test plans and programs. Cost of parametric test in semiconductor manufacturing: P9000 series testers feature a flexible option structure with up to 100 parallel test resources. Keysight's P9000 series also offers software compatibility with SPECS for 4080 parametric testers.
Alternatively, you can purchase an expander to add two MPSMUs and two voltage source units. This expander will enable you to further extend the capabilities of your equipment. The cost of parametric test in semiconductor manufacturing can be very high. But if you're a startup, cost-effective parametric test solutions will help you cut costs while maximizing measurement performance. And don't forget that a complete, integrated solution can cost up to $1 million.