SUBMICROMETER LUMINESCENT POROUS SILICON STRUCTURES USING LITHOGRAPHICALLY PATTERNED SUBSTRATES

Sub-micrometre area porous silicon structures were fabricated by anodi zation of patterned surfaces of crystalline p-type silicon, orientatio n (100) and resistivity 5-7 Omega cm. The mask for selective anodizati on was either silicon dioxide or silicon nitride, deposited onto silic on by low pressure chemical vapour deposition. The second mask was mor e resistant to the anodization solution (HF, ethanol and water solutio n) and was not dissolved during the anodization time used. When silico n dioxide was used as a mask, carl was taken to stop anodization befor e the whole layer was removed. Patterning was done by optical lithogra phy combined with a special process for sub-micrometre dimensions (sil ylation process). Dots and lines of dimensions down to 0.5 mu m were p roduced, which exhibit strong red luminescence under UV excitation. Th e film thickness of the porous silicon structures in the sub-micrometr e areas was smaller than the thickness in larger areas. The lateral gr owth of the structures under the mask was examined by scanning and tra nsmission electron microscopy. Microphotoluminescence experiments in a confocal microscope were also used for mapping the luminescent areas.