High-pressure mass spectrometers offer robust, real-time, in-situ analysis

San Jose, May 15, 2018

Control Magazine coverage of Atonarp’s recently introduced molecular sensor.

Atonarp recently introduced a molecular sensor (quadrupole mass spec) solution

Industrial process control is facing one of its greatest challenges. Billions of dollars of pharmaceuticals and advanced process node semiconductor devices will be manufactured using processes where fast, accurate molecular analysis is critical to the quality of the end product. There’s a pressing need for in-situ molecular analysis that delivers real-time results that are accurate, repeatable and quantitative from a small, rugged and easy-to-integrate solution. However, existing molecular analysis solutions such as residual gas analysis (RGA), gas chromatography-mass spectrometry (GC-MS) and optical solutions like near-infrared (NIR) and optical emission spectroscopy (OES) have limitations that make them impractical solutions.

Current solutions for molecular gas analysis applications have significant shortcomings. Mass spectrometry and residual gas analysis solutions have required low-pressure vacuum on the order of 1 x10-6 Torr to operate. Low-pressure operation requires sizable and expensive vacuum pumps, and ensuring there are no leaks makes installation and maintenance complex and costly. Further, low-pressure operation limits the sensitivity of the mass spectrometer or RGA, and while electron multipliers can be used to increase sensitivity, this comes at the expense of stability and repeatability, neither of which are process control-friendly issues. Gas chromatography (GC) has historically been used to isolate mixed gas components for quantitative analysis, but this process is slow, has significant consumable running costs and a high maintenance burden. Fourier transform infrared (FTIR) optical spectroscopy techniques can detect the presence of specific molecules, but getting quantitative data is very difficult, rendering them less useful in process control applications.

So how about ruggedized, high-pressure mass spectrometry? To be a useful process control tool, it must be process control production-ready. Basic production requirements are: to be fast and accurate, small and easy to install, field serviceable, robust, deliver stable and repeatable results, support easy software and system integration, and be low-maintenance.

Atonarp recently introduced a molecular sensor (quadrupole mass spec) solution that delivers on these requirements with: as many as 100 samples per second operation; sensitivity down to part-per-million (ppm) concentrations; small (20.4 x 20.0 x 25.6 cm) form factor; integrated vacuum pumps; and a rugged Faraday cup sensor that delivers high stability and infinite lifetime.

The miniature molecular sensor is about 5 cc and is mounted on 1.33-in. Conflat flange. It features an array of nine quadrupole mass filters operating in parallel. A single electron-impact ion source supplies ions to the individual quadrupoles to be filtered and collected on individual Faraday cups connected together. Driven at 11 MHz radio frequency (RF), the sensor is able to filter ions on the basis of mass-to-charge ratio with unit mass resolution from ultra-high vacuum (UHV) to pressures as high as several mTorr. Making the quadrupole small is offset by increasing the control electronics RF. The combination provides real-time, quantitative molecular analysis and virtually eliminates memory effects while allowing the system to work at higher pressures, which increase sensitivity.

Further, intuitive web-browser software, accessible via an Ethernet connection and industry-standard data file support (.json), make software integration, process datalogging and setup easy. To ease hardware integration, industrial analog and digital I/O are available, and can be used to control (and get input from) standard industrial sensors, actuators or PLCs.

Having the ability to do real-time, quantitative molecular analysis in-situ is an enabling capability for many industrial processes. Examples are given below for the pharmaceutical and semiconductor manufacturing markets of how small, rugged molecular sensor (mass spectrometer) is enabling disruptive process control techniques.

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