Environmental safety issues for molecular beam epitaxy platform growth technology

Abstract

The choice of a technology must clearly depend on its ability to fulfill not only material requirements but also environmental safety criteria. Therefore, the possibility of environmental impact raises questions related to safety and in the near future, the tolerable amount of hazardous materials, particularly for crystal growth of compound semiconductors. In the epitaxial field, both molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD) have already been acknowledged as well-established production methods and are playing important roles in the mass production of various device structures. Currently, however, it is common knowledge that there still exists one critical issue, namely, that of environmental safety with respect to the use of many hazardous materials. In MOCVD growth, large amounts of arsine (AsH 3) and phosphine (PH 3) are used, and in MBE growth the problem of higher amounts of arsine generation than the TLV (threshold limited value: 50 ppb) is commonly faced, particularly during maintenance procedures. By using gas source MBE (GSMBE), the arsenic contamination (adhesion) onto the wall inside the growth chamber is markedly reduced compared with that in the case of conventional MBE, and unintentional arsine generation is suppressed to be under the TLV. In addition, the consumption efficiency for hydrides is higher than 80%. This value is significantly higher than in the case of alternative growth methods, such as MBE (3–10%) and MOCVD (1–20%).