Alternative Gate Dielectrics for Microelectronics
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Alternative Gate
Dielectrics for Microelectronics
Robert M. Wallace and Glen Wilk, Guest Editors Abstract This brief article sets the context for the March 2002 issue of MRS Bulletin focusing on Alternative Gate Dielectrics for Microelectronics. Contributors are several experts from industry and academia engaged in the search for manufacturable solutions for a suitable alternative gate dielectric to SiO2 using high-dielectric-constant (high-) materials. Issues discussed in the articles include thermodynamics criteria for materials selection, materials interactions in the construction of the transistor gate stack, characterization of alternative materials, determination of suitable band offsets for candidate dielectrics, and integration of these alternative gate dielectrics in a manufacturable environment. Keywords: high-dielectric-constant materials, high- dielectrics, integration, materials characterization, process compatibility, thermal stability.
The scaling of integrated-circuit (IC) technology continues to be a critical capability for the Si-based microelectronics industry in order to increase functionality and fuel market expansion. The International Technology Roadmap for Semiconductors (ITRS) provides a periodic assessment of the technology requirements and challenges for the industry.1 The 1999 ITRS (updated in 2001) highlights several “grand challenges” for the industry to meet, and many of these challenges appear to require the introduction of new materials to the manufacturing process. This presents a golden opportunity for the materials science community, as the effort requires substantial research and development in materials science and, more important, materials integration. The well-established Si-based semiconductor industry has been immensely successful by engineering a common set of materials for several decades, mainly through an electrical engineering perspective. The introduction of new materials to the IC manufacturing process, however, will require the perspective of the materials technologist in concert with electrical engineering
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considerations. This is particularly apparent in the most aggressive (and dominant) Si-based technologies, such as complementary metal oxide semiconductor (CMOS) devices and memory applications such as dynamic random-access memory (DRAM). A key challenge that affects near-term CMOS transistor technologies includes the prospect of replacing SiO2 (and SiOxNy) as the transistor gate insulator in a time frame as soon as 4–5 years from now. Indeed, it is often argued that the natural formation of this stable, insulating amorphous oxide on Si is largely responsible for the tremendous growth of the Si-based industry over the last several decades. The identification of promising candidates for alternative gate dielectrics requires consideration of a number of important materials properties that, in turn, affect the electrical performance of an associated device. Additionally, the entire structure of the transistor (for example, the gate electrode and dielectr
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