Influence of Bottom Contact Material on the Selective Chemical Vapor Deposition of Crystalline GeSbTe Alloys
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Influence of bottom contact material on the selective chemical vapor deposition of crystalline GeSbTe alloys Alejandro G. Schrott1, Chieh-Fang Chen2, Matthew J. Breitwisch1 , Eric A. Joseph1, Ravi K. Dasaka1, Roger W. Cheek1 ,Yu Zhu1 and Chung Lam1 1 IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA 2 Macronix Emerging Central Laboratory, Macronix International Co., Ltd. ABSTRACT Selective Chemical Vapor Deposition of Crystalline Ge-Sb-Te alloys initiating at the bottom metal contact of vias of various sizes has been accomplished. The method is based on selecting Sb and Te precursors which do not decompose on dielectric surfaces in the utilized temperature range. INTRODUCTION Due to the stringent demands imposed by the scaling roadmap of phase change memory devices, it is becoming increasingly important to understand the Chemical Vapor Deposition (CVD) and Atomic Layer Deposition (ALD) processes options that can be utilized to fill small but high aspect ratio vias in structures that may constitute future memory cells. Due to the technological potential, both CVD and ALD methods have provided the means for an increasing number studies on phase change materials properties [1-5]. Recently, it has been shown that vias with very small critical dimensions (CD) can be filled with phase change material via an ALD process [6]. The latter, however, is a lengthy process. Furthermore, the adhesion to the bottom electrode has not been proven. In the current work, towards achieving the goals put forth by the scaling roadmap for phase change memory, the potential of selective CVD deposition of crystalline phase change materials alloys, and the role on selectivity of the material that forms the bottom contact of via holes formed in dielectrics, has been investigated. In this work, the growth is effected without using any reactive gas or plasma, so that the decomposition selectivity of the precursors utilized allows for growing the material starting at the bottom contact, with no deposition on the dielectric top surface. EXPERIMENTAL The CVD process was effected on 200 mm wafers in an Applied Materials chamber, attached to an Endura HP 5500 platform, modified for CVD processes. The system modifications include replacing the chamber lid, for one with a shower head; building an ampoule box containing 3 ampoules for precursors which connect to a mixing ampoule. The latter releases the mixture into the feeding line which leads to the shower head. Ampoules and lines are kept heated. The deposition was carried out at a chamber pressure of 4 torr, with Ar carrier gas flow ranging from 20 to 60 sccm, depending on the precursor. The running parameters were controlled by the chamber control program. However, the pneumatic valves attached to the ampoules were controlled by manually operated switches. Figure 1 shows a schematic diagram of the system.
Figure 1. Schematic diagram of the CVD assembly The ampoules and lines were heated to minimize adsorption during precursors transport. We used TETRAKIS (DIMETHY
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