1. Tilt-SEM for Observing 3D Shape of Semiconductor Devices
With the advancement of information society, the demand for high-performance and reliability of the Internet of Things (IoT) and automotive devices is rapidly increasing. To ensure the quality of the devices during their fabrication processes, a scanning electron microscope (SEM) capable of in-line three-dimensional (3D) metrology and inspection of fine device structures is important.
Observation of structures from various directions is a good way to visualize their 3D features. To observe an in-line wafer with high resolution and at a large stage tilt angle, an objective lens that has a short focal length and can avoid colliding with the wafer is required. Moreover, shifting in the field-of-view (FOV) when the stage is tilted needs to be kept to a minimum because the operator needs to look for the target pattern again after tilting the stage.
To fulfill these requirements, Hitachi has developed a novel conical objective lens equipped an assisting electrode to achieve high-resolution, large stage tilt of up to 55 degrees, and a small shift in the FOV. Equipped with the novel objective lens, Tilt-SEM, the CT1000 enables observation of fine roughness with an amplitude of a standing wave less than 10 nm formed on the sidewall of resist patterns. It also reduces the shift in FOV caused in optics by tilting the stage to less than 1 µm, which prevents the operator from missing the target pattern.
In the future, Hitachi will establish a 3D monitoring method of various semiconductor devices using the Tilt-SEM, thereby contributing to improve the device performances, shorten the turn-around time, and enhance the production yields.
[1] Novel objective lens structure and SEM images of resist patterns