SEM image of a heterostructure etched in a RIE plasma shows the SiGe undercut beneath Si, after Ref. 5.
Schematic diagram of helicon plasma tool. The diode laser shown was used to form a thin film interferometer on the substrate surface for in situ etch rate measurements.
Heterostructures with a spacer layer and a dopant layer were used for patterned etching to define quantum dots, and a spacer layer and a dopant layer were used for in situ etch rate measurements. Undesired undercutting due to enhanced etching of SiGe compared to Si is depicted, as observed in -based RIE etching, and shown in Fig. 1.
Etch rate (a) and selectivity (b) as a function of average bias voltage when using sinusoidal and tailored bias voltage wave forms. Plasma etch conditions: , Ar, and ; helicon power; gas pressure. Based on the etch selectivity of over PMMA, tailored bias voltage wave form was chosen to etch patterned quantum dot samples subsequently.
SEM image of structure etched in a helicon plasma shows a straight sidewall etch profile. The plasma conditions: , Ar, and ; helicon power; and gas pressure; tailored bias voltage.
AFM images of quantum dot pattern: (a) after etching and PMMA removal with acetone; (b) after etching, PMMA removal in acetone and plasma cleaning. The plasma conditions: , helicon power, and gas pressure.
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