Abstract
In current nanoscale semiconductor fabrications, high dielectric materials and ultrathin multilayers have been selected to improve the performance of the devices. Thus, interface effects between films and the quantification of surface information are becoming key issues for determining the performance of the semiconductor devices. In this paper, we developed an easy, accurate, and nondestructive diagnosis to investigate the interface effect of hafnium oxide ultrathin films. A roughness scaling method that artificially modified silicon surfaces with a maximum peak-to-valley roughness range of a few nanometers was introduced to examine the effect on the underlayer roughness. The critical overlayer roughness was be defined by the transition of RMS roughness which was 0.18 nm for the 3 nm thick hafnium oxide film. Subsequently, for the inline diagnostic application of semiconductor fabrication, the roughness of a mass produced hafnium film was investigated. Finally, we confirmed that the result was below the threshold set by our critical roughness. The RMS roughness of the mass produced hafnium oxide film was 0.11 nm at a 500 nm field of view. Therefore, we expect that the quantified and standardized critical roughness managements will contribute to improvement of the production yield.
Highlights
In relation to current industrial semiconductor metrology, the management of the thickness of ultrathin films has been conducted in a strict manner
Ellipsometry is a common approach to managing the thickness of the transparent and translucent films used in the semiconductor manufacturing process because this method is fast and nondestructive[5,6]
Spectral ellipsometry is a powerful tool when managing film thicknesses at the angstrom (Å) level using a proper micrometer spot size on the illuminated areas, it does not provide sub-nanoscale local surface information due to the limited lateral resolution associated with this method[5,7]
Summary
The set point of the distance between the probe and the sample was 4.4 nm. When the AFM probe was engaged on the sample, we kept the set point at 7 nm for a wide separation distance to reduce or prevent damage to the probe. The wet etching process was performed at room temperature using a 30:1 buffered oxide etchant (BOE) solution. An ultrathin HfO2 surface was inspected in tapping mode using a silicon probe (RTESPA-300; Bruker, USA) with a normal probe radius of 8 nm and a cantilever spring constant of 40 N/m. The cantilever was oscillated at 25 nm (free-air amplitude) and the set point was 15 nm. TM by changing the amplitude of the oscillating probe with an image isolation function This method isolates the background frequency and the special fingerprint frequency from the environment before the image scan
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