Effects of Nitrogen Reactive Species on Germanium Plasma Nitridation Processes
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0917-E01-02
Effects of Nitrogen Reactive Species on Germanium Plasma Nitridation Processes Takuya Sugawara1,2, Raghavasimhan Sreenivasan2, and Paul C. McIntyre2 1 Technology Development Center, Tokyo Electron America Inc., 2953 Bunker Hill Lane, Suite 300, Santa Clara, California, 95054 2 Dept. of Materials Science and Engineering, Stanford University, 476 Lomita Mall, McCullough Bldg., Stanford, California, 94305
ABSTRACT Roles of reactive species of germanium and silicon plasma nitridation were investigated by comparing nitrogen plasma chemistry and oxynitride layer physical properties. In high pressure remote plasma nitridation process, hydrogen containing neutral radicals (NH* and H*) were important to nitride germanium and silicon substrates. This process required high substrate temperature to nitride germanium substrate, whereas silicon substrates could be nitrided at low substrate temperature. In low pressure Radial Line Slot Antenna (RLSA) plasma nitridation process, N2+ ion species acted as dominant reactive species. Using this process, germanium could be nitrided at low substrate temperature without hydrogen and high nitrogen concentration (~22at.%) GeON was obtained.
INTRODUCTION Germanium is a one of the promising candidates for future channel material because of its high carrier mobility, small band gap for voltage scaling and high solubility of p-type dopants [1, 2]. As issues of germanium based metal oxide semiconductor (MOS) technology, we have poor performance of germanium dioxide (GeO2) such as water solubility and thermal instability [3-5]. H. Kim et al. suggested that intermixing of High-k and GeO2, and abrupt interface of High-k/GeO2 causes poor electrical property of Metal/High-k/GeO2/Ge gate stack structure [6]. Therefore, forming more stable passivation oxide layer on germanium surface is an important issue. To solve this problem, germanium oxynitride (GeON) is known as a good passivation layer on germanium surface [6]. Plasma nitridation is a promising technique to form silicon oxynitride (SiON) gate dielectric films and now being utilized in industry [7-9]. The unique character of this process is excellent controllability of nitrogen concentration and profile under low substrate temperature (
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