With the Area Selective Deposition (ASD) technique, the material is deposited on desired areas of the sample surface. The control of such process implies accurate characterization of the deposited material on both growth and non-growth surfaces.
This requires, first a good measurement capability to quantify the geometry of the deposited layer, and second, a proper assessment of the process selectivity. In this work, we show how to combine two complementary measurement techniques to overcome their individual inherent limitations 1 for ASD applications. Scatterometry, the first measurement technique,has been applied to the characterization of the deposited layer geometry properties because of its high sensitivity to dimensional features and material. To complement the ASD performance characterization with the local information,Atomic Force Microscopy (AFM) has been used to access the topography details of the analyzed surfaces. We have analyzed the AFM images with the power spectral density (PSD) approach to identify undesired material deposition in the non-growth area and thus to characterize process selectivity through the comparison to a reference sample.
Experimental validation of the scatterometry and AFM techniques for ASD applications has been done on wafers having various selectivity levels. The scatterometry metrology measured accurately the thickness of the deposited layer on both growth and non-growth areas when the deposited layer became uniform. The lateral overgrowth was quantified as well with the same technique and showed some changes from process condition to another. In addition, the PSD analysis applied to the AFM images was able to probe minutely the nanoparticles nucleation on the non-growth area and as result has revealed the selectivity transition regimes. Later, we have built a hybrid model by the combination of the 2 metrologies results and validated its predictions on test wafers.
Keywords: Scatterometry, AFM, Area-Selective Deposition, Power Spectral Density, Hybrid metrology, ALD