Materials Science Forum Vols. 573-574

Abstract: The role of single wafer Rapid Thermal Processing (RTP) in semiconductor manufacturing has been steadily expanding over the last 2 decades. There are several reasons for the successful adaptation of this technology. These include more critical requirements by advanced semiconductor technologies with respect to thermal exposure and control, as well as tremendous improvements by the RTP equipment community in resolving some fundamental limitations of the tooling, historically restricting wide spread implementation. From rather humble beginnings, RTP technology has now established itself as indispensable to the production of advanced semiconductor products. We review the history and implementation of RTP technology in semiconductor processing technology at International Business Machines Corporation (IBM) from the late 1980s to recent time.

Abstract: Rapid Thermal Processing (RTP) has been a key technology for semiconductor manufacturing. The ability to rapidly change wafer-processing temperature in a well-controlled way is a distinguishing characteristic of RTP. Today’s state of the art single wafer RTP equipment is used for a wide range of thermal processes for the manufacturing of advanced semiconductor devices. Two different designs of halogen lamp based RTP equipment dominate the applications. The two equipment designs can be traced back to the early development of the semiconductor industry before there was wide acceptance of RTP. Two junctures in the evolutions of these designs resulted in the growth of RTP. The first juncture occurred when the conventional batch diffusion furnace could not satisfy some of the thermal budget and ambient control process requirements for semiconductor devices. A second juncture occurred with breakthrough developments in RTP equipment that enabled better control and repeatability of the process temperature. Developments of alternatives to tungsten halogen lamp based RTP will likely be seen in the future.

Abstract: The study of fast diffusion processes in materials requires short isothermal annealing treatments combined with an accurate temperature measurement. The paper discusses the special demands on rapid thermal annealing (RTA) devices in diffusion research and how these can be met in practice. The scientific impact of RTA for diffusion research in semiconductors is demonstrated by several examples dealing with fast impurities in Ge and Si.

Abstract: The use of Rapid Thermal Processing to install lattice vacancy profiles into silicon wafers for the purpose of forming a template for the nucleation and ideal control of oxygen precipitation has become an important materials engineering tool for the microelectronics industry. This paper reviews the principles of the technique and the precise materials/defect engineering that it engenders. It furthermore discusses what has been learned regarding the elusive properties of the intrinsic point defects in silicon through studies of the distributions of vacancies created by use of the technique. Also discussed are recent discoveries about the critical role of the other intrinsic point defect, the self-interstitial and the development of oxygen precipitates and their distributions post-nucleation and the critical importance of what has become to be called the “ninja transformation” in the switching-on of gettering efficiency of oxygen precipitate systems.

Abstract: Significant performance enhancements are offered by silicon on insulator (SOI) or strained silicon, SOI being adopted for advanced devices in sustaining Moore’s law. Sub-45 nm device options are including fully depleted (FD) devices, that are stressing even more specifications for thickness uniformity. Nano-uniformity, considering thickness variation contributions from device level to wafer scale, has been introduced in substrate optimization and latest Unibond products are verifying FD requirements. Rapid Thermal Processing (RTP) based surface smoothing has been introduced in Unibond processing to combine thickness control and product quality requirements.

Abstract: An overview of various cleaning procedures for silicon surfaces is presented. Because in-situ cleaning becomes more and more important for nanotechnology the paper concentrates on physical and dry chemical techniques. As standard ex-situ wet chemical cleaning has a significant impact on surface quality und thus device properties, its influence on further processes is also considered. Oxygen and carbon are unavoidable contaminations after wet chemical treatment and therefore we discuss their in-situ removal as one of the main goals of modern silicon substrate cleaning. As surface roughness strongly influences the electrical quality of interfaces for epitaxy and dielectric growth, we concentrate on techniques, which meet this requirement. It will be shown that multi-step thermal sequences in combination with simultaneous passivation of the clean surface are necessary in order to avoid recontamination. This can be achieved not only for ultra hich vacuum but also for inert gas atmosphere. In this case the process gases have to be extremely purified and the residual partial pressure of contaminats such as oxygen and carbon has to be negligible. It will be demonstrated that 800°C is an upper limit for thermal treatment of silicon surfaces in the presence of carbon because at this temperature SiC formation in combination with a high mobility of silicon monomers leads to surface roughness. In addition mechanical stress causes dislocations and crystal defects.