Download - Wet Etchant for DRAM Word-line Titanium Nitride Recess ... · 4/3/2019 · •Employ TiN etching enhancer to accelerate TiN recess. Passivation TiN TiN TiO2+ Oxidizer TiN Enhancer

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)

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