Indistinguishable from magic

The new sapphire capacitance diaphragm gauge designed by Azbil is a perfect example.

Sixty-five years of exponential growth. This is the unstoppable rise of computer chips, since they were patented at the end of the 1950s. Today, what is a Bluetooth earbud if not a miniaturised computer? What is a car if not a computer transporting people? All sectors have been conquered, from the most recent (AI, etc.) to the oldest (agriculture, etc.).

Such staggering progress is still imaginable to a “normal” human mind. However, it is no longer the case when it comes to the performance of chips and their design. Honestly, billions of transistors on a single chip? A laptop capable of performing billions of calculations every second? (don’t even try to explain how a supercomputer can perform more than 400 million billion calculations within the time it takes to read this sentence).

Unsurprisingly, the leading companies in semiconductor and PCB design have become the queens of the world. Whether US chip designers (Intel, Broadcom, Qualcomm, AMD, etc.) or Asian (Samsung, TSMC, Foxconn, etc.) or European manufacturers. Their technological and economic influence has even geostrategic impacts (tensions between China and the USA over Taiwan).

Around these giants gravitate a galaxy of companies, providing equipment and services that are essential to their production (including LEMO for the past decade).

There are those who supply the entire process, such as the Dutch company ASML, a heavyweight in the field, whose ultraviolet photolithography systems enable TSMC and others to etch their printed circuits with extreme precision. There are also companies that provide for a specific function which is just as important. This being the case of Azbil Corporation founded in 1906, based in Tokyo with over 10,000 employees globally, Azbil provides a vast array of solutions, including control systems (industry, buildings, etc.) and measurement instruments. Among these, its sapphire capacitance diaphragm gauge model V8, launched in early 2023, has been rapidly adopted in semiconductor production.

In a nutshell, photolithography is used to etch integrated circuits by applying a “protective” film (film deposition) to a silicon wafer and removing anything not protected by a film (etching). This operation is repeated, nanometric layer after nanometric layer, until the required integrated circuit is obtained.

For the process to be successful, the total control of its working environment is a prerequisite. The process takes place in a vacuum chamber filled with one or more gases at constant pressure. The slightest variation in pressure may have an impact on precision and quality. This is where Azbil’s sapphire capacitance diaphragm gauge
model V8, adopted by manufacturers of film deposition and etching equipment, comes into the picture.

Diaphragm capacity gauges measure the pressure of gas under vacuum. They feature an elastic diaphragm that deforms according to the pressure applied. The instrument converts this pressure into a measurable electrical signal. Pressure being measured directly on the diaphragm, it doesn’t matter which gas is used (this is important, as the industry uses several gases). As for accuracy: plus/minus 0.25% of the measurement guaranteed by Azbil.

To establish its solution as a benchmark, the Japanese company had to overcome a whole series of challenges better than other companies.

Producing such a solution is an industrial challenge in itself. The size of the gauge is an important factor, with customers looking for the smallest possible solutions so that they can be better integrated into their equipment. The sapphire capacitance diaphragm gauge model V8 is more compact than those of most competitors, and even more compact than Azbil’s previous model. 

Azbil has kept the production details of its gauge confidential. All it reveals is that the diaphragm sensor surface – the heart of the instrument – is using MEMS processing technology. MEMS integrate electronic and mobile components on a microscopic scale (by photolithography on silicon wafers, as with integrated circuits). This may give an idea of the level of precision required.

What are the benefits of the MEMS process? As described above, the design of the printed circuits involves a series of film depositions on the silicon wafers. As the diaphragm of the gauge faces the chamber, it is also covered. If the film adheres to the diaphragm, it causes stress and a zero-point shift by depot. The user has to adjust the measurements and the errors become decreasingly consistent. With the MEMS process, Azbil turns the surface of the diaphragm irregular, so the film adheres less to it – the sapphire capacitance diaphragm gauge model V8 is therefore 10 times more resistant to deposition than the previous model, according to the manufacturer.

Last, but not least, high temperatures need to be kept under control.

Temperature and gas pressure being inter-related, a variation in the former can lead to an error in the consistency of the measurement. It isn’t enough to have a thermometer, many diaphragm gauges also have an integrated heater. This enables them to keep the outside surface of the diaphragm at the same temperature as that facing the inside of the chamber.