We describe a new method of producing ultrasmall structures on thick substrates with electron beam lithography. Using an innovative exposure technique, we obtain features with lateral sizes smaller than the incident beam diameter. These patterns are transferred into GaAs/AlGaAs quantum well heterostructures using chemically assisted ion beam etching, and uniform arrays of structures with lateral dimensions below 10 nm are produced. We employ reflection electron microscopy measurements to correlate the structure size with the exposure and development conditions for this fabrication scheme.