Continuous environmental surveillance guarantees high-quality electron microscope imaging

Electron microscopes (EMs) are vital quality control (QC) tools in semiconductor production, helping manufacturers to guarantee a high standard of product. However, the precision of EMs and the resolution of resulting images can be hindered by external interruptions, such as acoustic noises, vibrations and magnetic fields. Low resolution and perturbed images can make it hard to detect faults in semiconductor products, which could in turn decrease the yield and performance of manufactured goods. Therefore, continually assessing the quality of the imaging environment and pinpointing any potential sources of disturbances is critical to maintaining a high standard of production. Fortunately, there are dedicated systems on the market designed especially for continuous monitoring of the environment surrounding sensitive EMs, which now provide uninterrupted and automatic logging of various environmental parameters to revolutionise electron beam (EB) instrument applications.

Failure analysis is an important component of QC in semiconductor production, which can ultimately help to enhance yield and guarantee a high standard of manufacturing excellence. However, smaller and smaller semiconductor devices are being developed, making it increasingly difficult to perform failure analysis and locate defects in products. Various high-resolution EM tools – including scanning electron microscopy (SEM), focused ion beam scanning electron microscopy (FIB-SEM) and transmission electron microscopy (TEM) – are helping to analyse the structure of even the smallest devices. This is crucial for localising and characterising defects and electrical problems that may affect performance, solidifying these EM instruments as cornerstones of the QC process. 

Unfortunately, the environment in which the EM is located can have a significant impact on image quality, as external factors – such as acoustic noises, vibrations, and magnetic fields – lower the resolution and make it harder to find defects. In addition, these disturbances can also cause instability or shifts in the EB, resulting in significant reductions in resolution, so that instruments perform below their intended design specifications. It is therefore important to the quality of imaging that these types of disturbances are identified when the instrument is first installed within a semiconductor manufacturing or research environment. They must also be continually monitored throughout their use, as subsequent or transient changes to conditions can cause ongoing problems for operators. 

Surveying the environment

Surveillance of the environment prior to installation should be a standard when investing in any EB instrument, in order to ensure that the microscope or lithography machine is placed in an appropriate location that will enable it to operate to its desired specifications. There are purpose-made survey systems for this application – such as Spicer Consulting's SC11 family – which are able to measure both vibrations and external magnetic fields. Once installed, many EB instrument users also perform long-term surveillance of the environment to help identify any drifts in continuous fields or transient disruptions that could impact performance. However, until recently, the technologies available for this ongoing environmental monitoring have been missing one critical feature – the ability to measure several parameters simultaneously without any interruptions in data collection. 

Continuous feedback

An innovative monitoring system (SC28 Monitoring System, Spicer Consulting) that continuously logs magnetic fields and floor vibration in three axes, as well as acoustic levels, temperature and humidity, has recently launched onto the market. This system can be controlled via a computer connected to the same local area network, and all the gathered information is automatically stored in date-stamped files by the software. This program can also be used to define environmental specifications, either as minimum/maximum values, or as a spectrum of maximum amplitude versus frequency. The software constantly compares the measured values for each parameter with the user-defined specifications, and real-time results are displayed in a small window. The SC28 can be configured to send an email to the user if any parameters shift beyond the allowed margins. This can be done either once or at a specified frequency, making sure that the issue is dealt with in a timely manner. In addition, a traffic light beacon can be used to give a visual warning, something that can be useful in a manufacturing environment such as semiconductor production.