Wet Etchant for DRAM Word-line Titanium Nitride Recess ... · 4/3/2019 · •Employ TiN etching...
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Introduction Wet Etchant for DRAM Word-line Titanium Nitride Recess with Selectivity to Tungsten Wilson Yeh* , Wade Lee, Carol Cheng, Alan Chen, Lester Lee, Cami Shih, Paul Bernatis, Sang-Min Wong, and Chi Yen EKC Technology, DuPont Electronics & Imaging Contact info: [email protected]; [email protected] Design Concept Conclusions Technical Background (a) (b) (c) As dynamic random access memory (DRAM) scales to 20 nm and sub-20 nm, titanium nitride (TiN) recess with selectivity to tungsten (W) becomes one of the key process for fabricating the word-line structure in DRAM. Conventional approach of TiN recess was done by dry etching to etch back the TiN, but in advanced nodes it would damage the underneath gate oxide and induce the time-dependent dielectric breakdown leading to reliability issues. Therefore, many DRAM makers turn to achieve this process by using some commodity cleaning solutions, such as SC1 (mixture of NH 4 OH and H 2 O 2 ), SC2 (mixture of HCl and H 2 O 2 ) and SPM (mixture of H 2 SO 4 and H 2 O 2 ). However, the TiN to W etch rate selectivity of these commodity cleaning solutions are low, and most of these chemicals have high W corrosion rate. In this study, we present a novel selective etchant having high TiN etching with selectivity to W, and compatible with thermal oxide (ThOx), SiN and high-K material. Wet etch TiN recess with selectivity to W and ThOx becomes one of the key process for fabricating the word-line structure in DRAM. Results and Discussion Figure 1. (a) Mechanism of TiN etching; (b) SMF-X1: TiN and W equal etching (TiN=W); (c) SMF-X2: TiN recess with selectivity to W (TiN>W); (d) Oxidizer loading effect on TiN and W etch rate. • Oxidize TiN to soluble TiO 2+ . • Introduce effective W inhibitor with good W protection. • Employ TiN etching enhancer to accelerate TiN recess. Passivation TiN TiN TiO 2+ Oxidizer TiN Enhancer TiN E E E E E E Soluble TiO 2+ -E complex E E E E E E Mechanism of TiN Etching • We have developed SMF-series formulations for DRAM word-line TiN recess with selectivity to W and ThOx; the effective W protection allowing higher TiN/W selectivity. • SMF-series formulations are tunable on TiN and W etch rate according to customer’s requirements, and have good chemical stability. (d) Copyright © 2019 DuPont. All rights reserved. The DuPont Oval Logo and DuPont™ are trademarks of E. I. du Pont de Nemours and Company or its affiliates.
Transcript of Wet Etchant for DRAM Word-line Titanium Nitride Recess ... · 4/3/2019 · •Employ TiN etching...
Introduction
Wet Etchant for DRAM Word-line Titanium Nitride Recess with Selectivity to Tungsten
Wilson Yeh*, Wade Lee, Carol Cheng, Alan Chen, Lester Lee, Cami Shih, Paul Bernatis, Sang-Min Wong, and Chi Yen
EKC Technology, DuPont Electronics & Imaging
Contact info: [email protected]; [email protected]
Design Concept
Conclusions
Technical Background
(a)
(b) (c)
As dynamic random access memory (DRAM) scales to 20 nm and sub-20 nm,
titanium nitride (TiN) recess with selectivity to tungsten (W) becomes one of the key
process for fabricating the word-line structure in DRAM. Conventional approach of TiN
recess was done by dry etching to etch back the TiN, but in advanced nodes it would
damage the underneath gate oxide and induce the time-dependent dielectric
breakdown leading to reliability issues. Therefore, many DRAM makers turn to achieve
this process by using some commodity cleaning solutions, such as SC1 (mixture of
NH4OH and H2O2), SC2 (mixture of HCl and H2O2) and SPM (mixture of H2SO4 and
H2O2). However, the TiN to W etch rate selectivity of these commodity cleaning
solutions are low, and most of these chemicals have high W corrosion rate. In this
study, we present a novel selective etchant having high TiN etching with selectivity to
W, and compatible with thermal oxide (ThOx), SiN and high-K material.
Wet etch
TiN recess with selectivity to W and ThOx becomes one of the key process for
fabricating the word-line structure in DRAM.
Results and Discussion
Figure 1. (a) Mechanism of TiN etching; (b) SMF-X1: TiN and W equal etching (TiN=W); (c) SMF-X2: TiN recess with selectivity to W (TiN>W); (d) Oxidizer loading effect on TiNand W etch rate.
• Oxidize TiN to soluble TiO2+.
• Introduce effective W inhibitor with good W protection.
• Employ TiN etching enhancer to accelerate TiN recess.
Passivation
TiNTiN
TiO2+
Oxidizer TiN Enhancer
TiN
EE
EE
E
E
Soluble TiO2+-E complex
E
E E
EEE
Mechanism of TiN Etching
• We have developed SMF-series formulations for DRAM word-line TiN recess with
selectivity to W and ThOx; the effective W protection allowing higher TiN/W selectivity.
• SMF-series formulations are tunable on TiN and W etch rate according to customer’s
requirements, and have good chemical stability.
(d)
Copyright © 2019 DuPont. All rights reserved. The DuPont Oval Logo and DuPont™ are trademarks of E. I. du Pont de Nemours and Company or its affiliates.
