Abstract
Low resistivity polycrystalline Si could be selectively grown in the deep (~200 nm) and narrow patterns (~20 nm) of 20 nm pitch design rule DRAM (Dynamic Random Access Memory) by microwave plasma-enhanced chemical vapor deposition (MW-CVD). We were able to achieve the high phosphorus (CVD gap-fill in a large electrical contact area which does is affected by line pitch size) doping concentration (>2.5 × 1021 cm−3) and, thus, a low resistivity by adjusting source gas (SiH4, H2, PH3) decomposition through MW-CVD with a showerhead controlling the decomposition of source gases by using two different gas injection paths. In this study, a selective growth mechanism was applied by using the deposition/etch cyclic process to achieve the bottom–up process in the L-shaped contact, using H2 plasma that simultaneously promoted the deposition and the etch processes. Additionally, the cyclic selective growth technique was set up by controlling the SiH4 flow rate. The bottom-up process resulted in a uniform doping distribution, as well as an excellent filling capacity without seam and center void formation. Thus, low contact resistivity and higher transistor on-current could be achieved at a high and uniform phosphorus (P)-concentration. Compared to the conventional thermal, this method is expected to be a strong candidate for the complicated deep and narrow contact process.
Highlights
Since the design rule of the DRAM (Dynamic Random Access Memory) device and its contact size has continuously shrunk and its aspect ratio of contact has steadily increased, the traditional doped Si gap-fill method by thermal chemical vapor deposition (CVD) may no longer be extendable to the deep and narrow contact hole with a complicated design, e.g., the L-shaped gate buried contact
Numerous alternative solutions for these difficulties have been proposed, such as thermal CVD with an amino-silane seed layer [1], Si implantation after Si etch-back, flowable CVD and laser-induced epitaxial growth [2]. All of these methods cannot meet simultaneously requirements. Considering these needs and difficulties, bottom–up growth using a selective growth technique is a candidates for Si gap-filling without void and seam formation
The microwaves radiating from a radial-line slot antenna (RLSA) were used at a CVD system for oxidation and nitridation processes [5,6,7]
Summary
Since the design rule of the DRAM (Dynamic Random Access Memory) device and its contact size has continuously shrunk and its aspect ratio of contact has steadily increased, the traditional doped Si gap-fill method by thermal chemical vapor deposition (CVD) may no longer be extendable to the deep and narrow contact hole with a complicated design, e.g., the L-shaped gate buried contact (gBC). The main reasons for this limitation are seam and void formation near the middle of the contact area, which results from higher doping concentrations.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
