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

Abstract

The influence of surface pretreatments by remote hydrogen and/or argon plasma on the silicon nucleation density on thermally grown SiO 2 in the early stages of low pressure chemical vapor deposition (LPCVD) using monosilane (SiH 4) has been studied to control the areal density of Si quantum dots (Si-QDs) on SiO 2. In the remote H 2 (or D 2) plasma treatments prior to SiH 4-LPCVD, the formation of Si OH (Si OD) surface bonds, which act as reactive sites, was confirmed from no changes in the SiO 2 surface microroughness and in the thickness. In fact, by a H 2 plasma pretreatment, the areal density of Si-QDs as high as 7 × 10 10 cm −2 was obtained in the LPCVD condition of the dot density with as low as 6 × 10 8 cm −2 on as-grown SiO 2. By changing the pressure and the substrate temperature in the H 2 plasma pretreatment, the dot density was controlled in the range of 4 × 10 9 to 7 × 10 10 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 H 2 plasma, presumably because of improved uniformity and integrity in SiO 2 surface coverage with OH bonds just before LPCVD.