Our work

Line width roughness measurement

Semiconductor device performance is influenced by the uniformity of the line width of the transistor gate. A rough line can lead to yield loss. Control of the line width roughness (LWR) is thus a critical issue in lithography, even more so when line widths approach tens of nanometers.

LWR occurs even if the projected image on the photoresist is perfectly smooth. It is caused by the material properties of the resist, post-lithography processing steps and shot noise. The latter is related to the statistical behaviour of the irradiating particles that land on the resist. Statistical influences can generally be reduced by sampling over longer periods. However, if we extend the illumination time, the waferstepper throughput decreases. Researching the influences on the LWR is therefore crucial.

Even when the resist properties, the projected image and the shot noise statistics are kept the same, many other factors influence the LWR: the measurement itself and the way the lines are printed. The major challenge lies in isolating the relevant LWR influence from the measurement method and the printing method. For this purpose, we automatically calculated the correlation between tens of thousands of SEM images. The influence of fundamental physical processes is studied using computer simulations.

Finding resists with good sensitivity, good resolution and low LWR is considered to be top priority for EUV lithography. Theoretical models of resists help us to develop promising materials for the semiconductor industry.


TNO at Holst Centre launches 3D battery spinoff LionVolt

03 March 2021
TNO is spinning off its 3D battery activities from Holst Centre under the name of LionVolt BV. LionVolt will now accelerate the development of a revolutionary solid-state battery based on the 3D technology... Read more

Major release of NetSquid for designing quantum networks

23 December 2020
The first major version of NetSquid, a specialised simulator for quantum networks, has been publicly released. NetSquid is developed at QuTech, a collaboration between the TU Delft and TNO. The software... Read more

Position Paper: Envisioning a European Platform Economy

23 October 2020
Studies show that digitisation is the key to growth in European industry. But digitisation comes with many challenges. And the complications of a global pandemic and trade wars between the US and China... Read more


Dr. ir. Diederik Maas

  • Helium ion microscopy
  • HIM
  • HeIM
  • metrology
  • SEM


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