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Four point probe

Are you having problems with your 4- point probe?

NPS can solve that problem for you!


In this article, we will focus on the four-point probe. A standard instrument in use for over 40 years.

The four-point probe was developed by A&M FELL of the UK in the 1960s as an electrode for measuring the resistivity of semiconductor materials.  Later, the company was acquired by Kulick & Soffer, a major U.S. manufacturer of semiconductor equipment, which took notice of its performance and began selling it, and it became a tool widely used worldwide.


In Japan, NPS (formerly known as Nakamura Precision Shokai) started selling the product in 1971, and introduced it to semiconductor manufacturers and equipment manufacturers.

At that time, it was still difficult to find a simple and stable way to measure the resistivity of silicon wafers, and engineers quickly recognized the FELL probe as an important tool to solve the problem of semiconductor resistivity measurement, along with the development of measuring instruments.


After repeated prototyping until the completion of the FELL probe, we established a design concept that predicted the next several decades and a theoretical structure that enabled high-precision measurement, and succeeded in creating a four-pronged probe that could be used with today's diversified objects to be measured.


Later, the patented FELL probe became a worldwide standard instrument used by semiconductor and device manufacturers.


(There was an episode where the engineers who were involved in the development of the probe created a separate company to market the probe because it was so good even at the prototype level, but in the end, the difference in performance and durability was so great that it could not be used as an industrial tool.


Unlike a four-terminal probe, which simply has four needles, a four-prong probe is a high-performance probe created by "the science and technology of semiconductor contact.


For example, the internal spring that pressurizes the needle (patented part) was determined from dozens of prototypes, and is a specification that has a basis in performance.

For the mechanical part, we adopted the classic ruby guide for needle movement technique, which was the only cutting-edge watchmaking technology at that time 50 years ago, to pursue the accuracy of the hand guide.

(Ruby sliding is still used in some of our FELL type probes, but for the sake of accuracy control and functionality, we use parts made with new materials and manufacturing technology for new probes.)

For the needle part in particular, which comes into contact with the object to be measured, the tip structure is formed to correspond to the type of object to be measured, taking into consideration the physical and electrical elements.  These technical considerations greatly affect the measurement accuracy, durability, measurement capability, and so on.


In the 1970s, NPS President Hayato Nakamura spent a long period of time training at A&M FELL's factory in England to learn the manufacturing technology and know-how of four-point probes, and the technology he inherited directly from the engineers at that time is utilized in the current four-point probes.



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