| Summary: | 博士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 100 === When copper interconnect began to be mass produced in the semiconductor industry, Tantalum or Tantalum compounds has been widely applied as the most important diffusion barrier layer candidate in Copper interconnect. After several technological generations and being adopted for various manufacturing evolutionary stages, it is still in use. Specifically, the diffusion bilayer with Ta-TaN, which allows for well integration with copper interconnects, is the most critical technology.
In addition to technological advancement, the current semiconductor industry must also consider fabrication cost requirements in order that production can meet current demand. Meeting both technological and cost requirements present a major challenge on research and development.
According to the latest copper wire development trends, ruthenium (Ru) or ruthenium nitride (RuNx) as diffusion barrier layer for 20nm~28nm technology. That is mainly the low-resistivity performance under the ultra-thin thickness. Hoewever, the Ruthenium target cost of is higher than that of Tantalum metal about 84 times.
This paper will focus on developing a robust fabrication method to meet technological requirements while achieving cost competitiveness. It aims to find a breakthrough method to reach the low resistance under the thin-thickness. The key points of this research are as below: (1) The Ta-TaN bilayer, as the material candidate, is combined with optimized resputter fabricate methodology. The methodology provides conformality with good step coverage in the subsequent barrier and copper seed steps. (2) The method can fabricate without extra heat needed under low thermal budge condition. Besides, the Resputter fabrication acts as the treatment method to improve the interface between Ta-TaN to reach the low resistance requirement. (3) Effectively integrated overall copper interconnect production to get electriccal and reliability test on the product wafer; (4) Integrate the barrir layer/copper seed advantages and combine with production speed that up to at least 70 wafers per hour production. The points described above, under a combination of study and industry, to complete the actual product to make application.
The key points of this study of the interface Argon bombard treatment list as below (1) The Resputter process can be stable to guide a low resistance α phase - tantalum metal. (2) The resputter fabrication can improve the gap fill ability to get good step coverage; however, if the fabrication is not optimized, it is easy to produce over-etching phenomenon in the trench corner area. The defect will induce the copper diffuse and thus compromise device reliability. This study aims to find the deposition and resputter correlation and prevent this defect through process optimize. (3) This study will identify the Tantalum microstructure by high-magnification microscope (High Resolution TEM, HRTEM) and the stable α-phase formation factors. Besides, we also study the Titanium and Tungsten underlayer to enhance the stable low resistance α phase Tantalum produce. That can be effectively achieved so that low resistance is measured even under thinhickness to meet the requirements of trends of 28 to 20 nanometers copper interconnect Technology Roadmap under low cost on manufacturing.
The above, this study with use of argon ion bombardment interface approach combine the manufacturing cost advantages. The Ta/treated-TaN bilayer structure not only meets the requirements under the thin thickness, can reach the goal of the low resistance. Furthermore, Ta/Ti and Ta/W bilayer structure can prove low resistance under thin structure.It is the hope of the researcher can be used as the development of other products application.
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