Using Self-assembly and Selective Chemical Vapor Deposition for Precise Positioning of Individual Germanium Nanoparticle
- PDF / 688,540 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 94 Downloads / 203 Views
0921-T07-09
Using Self-assembly and Selective Chemical Vapor Deposition for Precise Positioning of Individual Germanium Nanoparticles on Hafnia Shawn S Coffee1, Wyatt A Winkenwerder1, Scott K Stanley1, Shahrjerdi Davood2, Sanjay K Banerjee2, and John G Ekerdt1 1 Chemical Engineering, University of Texas at Austin, 1 University Station C0400, Austin, TX, 78712 2 Electrical and Computer Engineering, University of Texas at Austin, 1 University Station C0803, Austin, TX, 78712 ABSTRACT Germanium nanoparticle nucleation was studied in organized arrays on HfO2 using a SiO2 thin film mask with ~20-24 nm pores and a 6×1010 cm-2 pore density. Poly(styrene-b-methyl methacrylate) diblock copolymer was employed to pattern the SiO2 film. Hot wire chemical vapor deposition produced Ge nanoparticles using 4-19 monolayer Ge exposures. By seeding adatoms on HfO2 at room temperature before growth and varying growth temperatures between 725-800 K, nanoparticle size was demonstrated to be limited by Ge etching of SiO2 pore walls. INTRODUCTION Column IV semiconductor nanoparticles have many desirable properties such as photoluminescence and the ability to retain a quantized number of electrons. Strict size control is required for successful integration into devices since the properties are dependent upon nanoparticle size. Tiwari et al. [1,2] proposed a nanocrystal-based flash memory utilizing Coulomb blockade charge retention in a layer of silicon nanoparticles. Optimal device operation requires monodisperse particles able to trap a discrete amount of electrons in a given nanoparticle and then discharge them repeatedly. Lateral spacing between particles is required to prevent electrons from tunneling through the gate control oxide into neighboring particles. Bringing the proposed flash memory into production while maintaining the standards set forth by the semiconductor industry in the International Technology Roadmap for Semiconductors (ITRS) [3] requires repeatable fabrication. Using values set forth in the ITRS, the gate size and number of required nanoparticles can be estimated using geometric considerations. Placing 5 nm diameter nanoparticles laterally spaced 4.5 nm (~5×1011 cm-2 density) upon the 2010 Roadmapestimated gate length of 180 nm and a 150 nm width leads to ~480 nanoparticles per device. In 2018, ~80 nanoparticles will fill the 120×48 nm-sized gates. Exact size control and lateral placement is necessary with future device fabrication ensuring the proper nanoparticle quantity is present. The material system and growth method herein are motivated by device performance and process capability. Semiconductor deposition using chemical vapor deposition (CVD) is a well characterized process and should be easily implemented into the nanoparticle based flash memory fabrication process. Germanium is selected as an alternative to silicon since it is shown to improve device performance [4] and germanium use in memory devices is well documented [5-7]. Hafnia as a tunnel dielectric choice is dictated by its ability to prevent the na
Data Loading...
