Thickness measurement of nano-metallic film with electromagnetic sensor under large sensor-sample distance

Abstract

The requirement for noncontact thickness measurement of metallic film with nanometer precision in semiconductor industry is urgent to be satisfied. Using the flat coil model, the magnetic field distributions along the axis of the sensors with close-packed and loose-packed coils were calculated and optimized. The calculation results based on the model have shown that the sensitivity of the sensor made of close-packed coils with a constant height increases with the outer diameter, and decreases with the inner diameters for a given sensor-sample distance. The designed coils with different sizes were fabricated by self-adhered enameled copper wire. The coils were used as the sensor for the thickness measurement of the copper films deposited on silicon wafer. Measurement results verified that the designed coil sensor can achieve the nanometer resolution of thickness measurement under large lift-off, which can be widely used in semiconductor industry.

Nanometric Metal-Film Thickness Measurement Based on a Planar Spiral Coils Stack

“…Another important element to notice is that the sensitivity of the sensor improves with the frequency, reaching a maximum of 3.8 mV/nm for 20 MHz in the range of 20-70 nm. This value is higher than sensitivity ratios found on literature, showing the potential of the proposed sensor to measure thickness of metallic films in the range of nanometers [8] [40]. On the contrary, when the frequency is decreased the sensor is able to measure thickness of several microns: this way, for 1 MHz the output voltage is not saturated up to 3.5 microns, showing a sensitivity of 0.01 mV/nm, suitable for these values of thickness.…”

The semi-analytic solution to the magnetic field of frequency-band-selecting eddy current testing for local corrosion flaw in large diameter pipeline

“…Values in the "Verification by numerical simulation" section External radius of the excitation coil (mm) magnetic field in regions 1 and 2 and obtain equations ( 8) to (10). You can find the detailed description for equations ( 5) to ( 7) by Yu et al 23 C 11 = C 22 + e 2λd C 21 (5)…”

“…By substituting equations ( 8) to (10) into equations ( 11) and (12), which are the magnetic vector potentials in regions 1 and 2 investigated by Yu et al, 23 we can obtain the series expression for the magnetic vector potential in regions 1 and 2 for a single coil as equation ( 13) 11)…”

“…Following that, Li et al 8 and Fan et al 9 derived an analytical expression for the magnetic field for multilayered specimens and proposed a relationship between the thickness of the specimen and the magnetic field. Zhao et al 10 studied the influencing factors on the resolution of coil sensors and experimentally demonstrated the feasibility of nano-metallic film thickness measurements using ECT. Yu et al 11 , 12 proposed the coating thickness measurement approach and conductivity measurement by the traditional eddy current technology (ECT) and dual-frequency ECT for conductive coatings.…”

An Impedance-Permeability Self-Resonance of Inductance Coil With Metamaterials

“…However, this technique works in microwave range which is complex and not easy for practical instrumentation. Besides, as the semiconductor process develops, higher accuracy is needed and nanometer-scale thickness measurement becomes an urgent requirement [11]. However, the increase of the resolution of EC sensors runs into a bottle neck by using the common design and common materials.…”