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How to achieve accurate, fast and automated wafer test

Release time:2021-12-08Source: semishare

Driven by Moore's Law, integrated circuits are also greatly reducing circuit size, volume and cost, and continuously improving processing speed and performance. The continuous advancement of aerospace, the development trend of automobile electrification, and the arrival of the 5G era, how to ensure stable operation in various complex environments, all of which have put forward higher requirements for the new generation of integrated circuits, and wafer testing has also changed. It gets more complicated. As the amount of semiconductor investment continues to increase, the tolerance for design errors is almost zero, so strict verification tests must be carried out before the chip enters mass production and during mass production.

WAT (Wafer Acceptance Test) test is an important site for wafer manufacturing. It is used in conjunction with a probe station and a tester. It is used to test the testkey  on the completed wafer for electrical testing. Generally, sampling tests are performed (5 points or more per wafer). If some important parameters do not meet the requirements, the wafer will be scrapped and will not enter the next stage. The WAT test reflects the stability of the wafer factory's processing technology.

CP (Chip Probing) test is used in conjunction with a probe station and an ATE tester to test the functions and electrical parameters of the chips on the wafer. The probe station is responsible for the transportation and positioning of the wafer, ensuring that the surface of the wafer is moved to the precision The instrument delivers a more stable signal, so that the Dies on the wafer are in contact with the probes and tested one by one (or in parallel) to achieve more accurate data testing and measurement. After the completion of the wafer production, due to various manufacturing defects introduced due to process reasons, there will be a certain amount of unqualified products in the Die distributed on the wafer. The purpose of CP testing is to find out these unqualified products before packaging. On the one hand, it analyzes the cause of failure, so as to increase the yield of the product subsequently, and on the other hand, reduce the cost of subsequent packaging and testing.

With the rapid development of global informatization, networking and knowledge economy, semiconductor products are also constantly undergoing innovation and technological iteration. The pressure from the market forces engineers and scientists to constantly update their technologies, reduce the time to market, and leave the wafer test time for fabs or laboratories more tight and precious. In the process of WAT test and CP test, how does the probe station, which plays an important role, meet the needs of engineers? SEMISHARE has intensively cultivated the probe station industry for more than ten years and is one of the few domestic manufacturers with independent technology and production strength. The A12 developed by SEMISHARE is a 12-inch (8-inch compatible) mass production fully automatic wafer probe station. The equipment can be combined with different types of Parametric and ATE test units. Precise contact between them to complete wafer WAT/CP testing. The equipment is easy to operate and has good mechanical stability. It can provide customers with a cost-effective and high-yield wafer testing solution to meet the requirements of (fabs, Packaging and testing plants, testing plants) and other test requirements of different customers.

Self-developed software, simple and easy to operate, can realize 7×24 hours unattended

The self-developed software system has strong compatibility, powerful functions and simple operation, which is very friendly to novice operators. The measurement job can be put into operation at night or on weekends. Through high-resolution and high-precision temperature control, all devices on the wafer can be tested at different temperatures without operator intervention. If the probe deviates from the state of alignment with the Pad, the system will automatically realign them to save test time. It has a powerful Wafermap editing function and supports offline and file import and export functions.

Vision automatic and precise calibration

In the test situation, the precise placement of the light is crucial, and the vision is automatically and precisely calibrated, which can reduce the test time from several months to a matter of minutes in some cases. The self-designed upper and lower microscope system, unique upper and lower focusing and centering optical technology, and 4 sets of 2 million pixel high-definition digital cameras, precision pneumatic upper microscope structure, ensure that the calibration and needle sticking are in the same area, and each microscope is With high and low magnification, it can meet the needs of high-precision alignment and needle point recognition.

High strength and low center of gravity design structure, high precision and test speed, greatly improve test efficiency

Multi-directional environmental monitoring and compensation functions to solve the position accuracy changes caused by temperature and humidity changes.High-precision XYZR four-dimensional platform, XYZ accuracy up to ±1μm, R accuracy up to 0.0001°, 0.1μm resolution grating ruler, to ensure ultra-high precision motion performance. The machine frame with integrated casting and long-term aging treatment can realize 7×24 hours of uninterrupted work. The movement rate of the XY axis can reach 200mm/s, which greatly improves the test efficiency.

The core of realizing accurate, fast and automated wafer testing is to enable our equipment to operate autonomously according to the set requirements through continuous innovation of software and hardware technologies, to achieve more precise contact and shorten the time of data acquisition. SEMISHARE has been committed to provide our customers with professional test and measurement solutions.

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