Control of the nucleation density of Si quantum dots by remote hydrogen plasma treatment

The influence of surface pretreatments by remote hydrogen and/or argon plasma on the silicon nucleation density on thermally grown SiO2 in the early stages of low pressure chemical vapor deposition (LPCVD) using monosilane (SiH4) has been studied to control the areal density of Si quantum dots (Si-QDs) on SiO2. In the remote H2 (or D2) plasma treatments prior to SiH4-LPCVD, the formation of SiOH (SiOD) surface bonds, which act as reactive sites, was confirmed from no changes in the SiO2 surface microroughness and in the thickness. In fact, by a H2 plasma pretreatment, the areal density of Si-QDs as high as 7 × 1010 cm−2 was obtained in the LPCVD condition of the dot density with as low as 6 × 108 cm−2 on as-grown SiO2. By changing the pressure and the substrate temperature in the H2 plasma pretreatment, the dot density was controlled in the range of 4 × 109 to 7 × 1010 cm−2. Further increase in the dot density and improvement of the dot size uniformity was also demonstrated by the pretreatment of Ar plasma followed by H2 plasma, presumably because of improved uniformity and integrity in SiO2 surface coverage with OH bonds just before LPCVD.