This paper investigates the ability of second harmonic generation (SHG) to probe the passivation quality of atomic layer deposited (ALD) Al2O3 on Si by estimating the induced interface electric field due to fixed charges in the oxide. Samples with various oxide charges (Qox) and interface state densities (Dit) were fabricated, using different deposition parameters. The samples were characterized by capacitance-voltage (C-V) and microwave photoconductance decay (µ-PCD) measurements in order to evaluate Qox and Dit, as well as the effective minority carrier lifetime τeff. The SHG results were consistent with Qox, Dit and τeff values, proving the ability of the technique to monitor the interfacial quality in a contactless and non-destructive way. Optical simulations which use the electric field values obtained from the C-V measurements could reproduce the measured SHG signal. This demonstrates that SHG coupled with optical simulation can give access to the electric field magnitude and thus characterize the electrical properties of oxide/Si interfaces.
The second harmonic generation (SHG) proved to be a very promising characterization technique for dielectric-semiconductor interfaces because it is sensitive, non-destructive, can be applied directly on wafer, at different stages of wafer processing. The method, based on non-linear optics effects, is measuring a signal encompassing the "static" electric field at the dielectricsemiconductor interface which is directly related to the oxide charges Q ox and to the interface state density D it. A general methodology for Q ox and D it extraction from SHG measurements requires (i) calibration based on parameters obtained by classical electrical methods and (ii) modeling to capture the optical propagation phenomena that impact the SHG signal. In this paper, we discuss these issues based on a review of our recent advances on how to exploit SHG for dielectrics on semiconductor characterization.
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