Enabling Thermal Processing of High and Low Dielectric Constant Materials
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INTRODUCTION Overview Since the invention of integrated circuits in 1957, silicon dioxide, silicon nitride, and silicon oxynitride have played the role of the most important dielectric materials used in the silicon IC industry [1]. The continued trend towards smaller feature sizes in the microelectronics industry is forcing researchers to develop processing techniques for the deposition of materials with dielectric constants less than that of SiO 2 as well as materials with dielectric constants higher than that of Si 3N4. Various professional societies such as the Materials Research Society and the The Electrochemical Society have organized conferences dedicated to the subject of high and low dielectric constant materials. Because these, new materials will be incorporated into subquarter micron feature size circuits, the issues related to performance, reliability, manufacturing compatibility and process integration must be considered in developing any new processes [2]. A careful examination of all of the published results shows that in many cases, rapid thermal processing (RTP) offers the best prospect for meeting the process requirements previously mentioned [3,4]. The objective of this paper is to explain the importance of rapid thermal processing and provide supporting experimental results. Specifically, in the case of low dielectric materials, we report the results of rapid thermal processing-assisted chemical vapor deposition 369 Mat. Res. Soc. Symp. Proc. Vol. 470 0 1997 Materials Research Society
(CVD) of amorphous Teflon fluoropolymer (K= 1.93) thin films. In the case of high dielectric materials, using RTP processes both pre- and post-Ta 20 5 deposition is discussed, as well as using RTP for extending silicon nitride technology for use in yet another generation of DRAM capacitors. Why Rapid Thermal Processing As manufacturing process flows move to 0.25 jim and below, RTP processes become enabling in many areas that previously did not exist or where RTP was only an alternative solution. Most of the advanced low and high dielectric constant materials are extremely sensitive to the subsequent thermal processing steps [5]. RTP technology is required in many cases to keep or achieve a desirable crystalline phase in these new materials without exceeding the limited thermal budget available for the advanced process flows. The transient nature of RTP technology lends itself to the formation of dielectric materials with stable crystalline phases, which are achieved without excessive thermal budget loss.
Most of the advanced low and high K materials, such as Teflon and Ta2Os, are deposited using organic precursors [6,7]. These processes inherently incorporate contaminants such as carbon during the decomposition of the complex precursor. This often leads to the degradation of the structural and electrical performance of the dielectric films. RTP conditioning, partly because of the cold wall processing and also the spectral content advantage, promotes defect-free films with desirable physical and chemical properti
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