As well as measuring CD, monitoring pattern profile is becoming important for semiconductor metrology. Illuminating
the wafer and detecting the reflective light, reflective light intensity in the Fourier space includes the information of CD
and pattern profile variation by form birefringence effect. CD change and profile variation could be detected separately
for the actual wafer. Mathematical simulation is presented the background of our unique approach. The detail results of
CD and pattern profile monitor is shown in this paper.
There are two kinds of critical dimension (CD) management tools; CD-SEM and Optical CD (OCD). OCD is
preferable to other existing measurement tools, because of its higher throughput and lower photoresist damage. We have
developed an Automated Pattern profile Management (APM) systems based on the OCD concept. For the monitoring
thin line, APM detects light intensity from an optical system consisting of a polarizer and an analyzer set in a cross-
Nicol configuration as a polarization fluctuation. This paper reports our development of monitoring technology for hole.
In the case of hole management, APM detects light intensity from diffraction intensity fluctuation. First of all, the best
conditions for hole management were designed from simulations. The best conditions were off-axis aperture and S
polarizer. In our evaluation of wafers without underlayer, we obtained a good correlation with CD-SEM value. From the
simulation, we consider the APM system to be very effective for shrinking hole process management of the next
generation from the simulation.
We tried to detect the CD variation of the 4x generation hole pattern using the diffraction light on Fourier space with the
polarized light and the modified illumination.
The new technology named DD (Dual Diffraction) method has been developed based on the optical simulation and the
experimental approaches. We introduce the case of detection for the diameter variation on a multi-layered hole pattern
with new method.
A new technology was developed to detect Critical Dimension (CD) variations in a Fourier space. The detection
principle is a form birefringence of the wafer. Utilizing this principle, CD and Pattern Edge Roughness (PER) variations
are detected as a polarization fluctuation and converted into light intensity. We have achieved high resolution and high
sensitivity by combining a form birefringence with a novel optical system. This system detects the light intensity in a
Fourier space with a high NA objective, enabling the detection of various lights with different incident angles and
polarization states at a time. We have confirmed through simulations that this system has high sensitivity toward CD
variations. Furthermore, in partnership with Toshiba Corporation, and through the evaluation of wafers fabricated at
Toshiba, we conclude that the light intensity detected by the new system strongly correlates with CD values, and that the
new system is capable of detecting CD variations in sufficient sensitivity.