A high performance molecular beam epitaxy system equipped with the automatic substrate transport mechanism

Abstract

A novel molecular beam epitaxy (MBE) is designed not only for laboratory use but also for the study of its anticipated performance in commercial production of compound semiconductor devices. The system is composed of five chambers, where the operations of deposition, preparation/analysis, transfer, loading, and unloading are carried out. The deposition and the preparation chambers can be evacuated to the level of <6.7×10−9 Pa, and transfer chamber less than 6.7×10−8 Pa. These high levels of vacuum could be reached by the development of a high performance turbomolecular pump (TMP), the use of high quality stainless steel as the structural material of the chambers, and the preparatory practice which reduced the outgassing rate to less than 1.3×10−10 Pa m3 s−1 m−2. The system can handle a substrate of up to 3 in. in diameter. The whole operation of the substrate transfer is controlled by a personal computer. The heating temperature of the substrate can be raised to 800 °C, and the maximum rotational speed of the substrate holder is 120 rpm. Many high quality thin films can be grown in this system. For example, on a GaAs and an AlGaAs epitaxial growth, the following figures were obtained; the Hall mobility 8150 cm2 V−1 s−1, the carrier concentration 1×1014–2×1018 cm−3, the film thickness and mole fraction uniformity for 3 in. substrate ±5%. These figures demonstrate the capability of the present system in fabrication of most GaAs devices.