3D hollow nanosphere structure by ALD coating on AR 9:1 closely-packed nanopshere

Instrument Technology Research Center (ITRC), affiliated to National Applied Research Laboratories (NARL), has successfully developed a process, called atomic layer deposition (ALD), to grow thin film atom by atom. The excellent thickness control, uniformity and step coverage make ALD an enabling technology for next-generation microelectronic device. With a shrinking feature size, microelectronic device manufacturers have encountered great challenge in maintaining the prediction of Moore's law. 2006 International Technology Roadmap for Semiconductors has predicted that a DRAM trench capacitor with an aspect ratio of 100:1 is needed for the 32nm node technology. The width of trench capacitor is only 60nm, which is only one two-hundredth of the diameter of human finest blood vessel. For the 32nm node technology, a 1nm thick dielectric capacitor should be deposited on the trench capacitor structure with good step coverage. The thickness of dielectric film is only one half of the diameter of human DNA. Therefore, the film thickness should be precisely controlled and uniform within a 12 inch or larger silicon wafer for next-generation technologies. Traditionally, the dielectric films are prepared by using physical vapor deposition (PVD) or chemical vapor deposition (CVD). The line-of-sight characteristic of PVD would result in massive deposition and clog formation at the trench opening and prevent thin film growth at the trench bottom of DRAM capacitor. Though CVD has better coating conformality than PVD, the mass transport of deposited materials through the trench would leads to a slower deposition rate at the bottom and compromises the thickness uniformity and step coverage. ALD was developed in 1970s, but not widely applied in industry due to its relatively low growth rate. Since late 1990s, more and more effort has been put into the applications of ALD in semiconductor due to its excellent thickness control, uniformity and step coverage. In the ALD process, precursor gas is introduced into a growth chamber, and reacts with the substrate surface by means of exchange reaction and form one layer of surface adsorbate. The surface adsorbate does not react with ALD precursor gas and will stop the exchange reaction when a full coverage is formed. The self-limiting behavior makes it possible to grow thin film atom by atom. Since the exchange reaction only takes place on the substrate surface, mass transport through nano-scaled structures is not important factor for ALD. Therefore, ALD is capable of growing thin films with an excellent large-area uniformity and step coverage. Because of the excellent thickness control and uniformity, ALD is regarding as an important tool for preparing the gate dielectric and metal gate in CMOS technology beyond 45 nm node. ALD can also be applied in preparing diffusion barrier, adhesion and nucleation layer. Equipment manufacturers, like Applied Material, Axitron-Genus and ASML are dedicated in developing ALD system for future semiconductor technology. According to VLSI report, the scale of ALD system market, 100 millions USD in 2003, increased rapidly to 400 millions USD in 2003 and will reach 3 billions USD in 2015. Although Taiwan's companies have world-leading technology, they have limited profit due to large investment in device-making equipment and purchasing intellectual properties. If Taiwan's companies want to increase the profit, it is very critical to reduce the reliance of foreign equipment and have their own know-how. However, the local equipment suppliers in Taiwan have very few resources in developing advanced semiconductor system, like ALD. Therefore, National Science Council (NSC) has put great effort on encouraging the development of equipment technology. For many years, ITRC has been dedicated in developing important tools for vacuum, optoelectronic, bio- and nanotechnology industries. The vacuum research team in ITRC developed the Taiwan's first home-built 4" ALD system in 2005. Based on the performance test, we demonstrated that the ALD film is a good candidate dielectric for future microelectronic device and can match the industry's needs. We have co-work with the research team of Professor Chun-Yen Chang, the formal principal of National Chiao Tung University, on the development of advanced non-silicon based metal-oxide-semiconductor field-effect transistor (MOSFET). Our ALD research with Professor Tsong Pyng Peg, the principal of Yuan Ze University, on nanotechnology was published in the well-known joual, Nano Letter, which has an impact factor of 9.96. Based on the long-established knowledge of vacuum technology, ITRC has successfully developed the 4 and 8 inch ALD systems. Advanced researches on high-k dielectrics for MOSFET, and transparent conducting oxides for optoelectronic device and solar cell are undergoing. We are looking forward to more cooperation with academic and industrial fields in semiconductor, optoelectronic and energy. Moreover, NSC has called for projects to develop advanced technologies for next-generation semiconductor devices this year. With the help of NARL, ITRC obtain the NSC support to build a 12 inch ALD system. Gate dielectric and metal gate processes for CMOS technology beyond 45 nm node will be carried out in this project. Development of diffusion barrier materials for copper process is also an important direction. In addition, this 12 inch ALD system is batch-type in this version and will have a higher throughput. ITRC will transfer the knowledge for building ALD system to Taiwan's equipment company this year. By helping the local equipment company, high-quality and affordable ALD will be available, which is the key for maintaining the advantage of Taiwan's semiconductor industry.