1
Development of Metal Free Wet Etching Chemical for Ruthenium Interconnect
TOK (Tokyo Ohka Kogyo Co., Ltd.), Japan *Takuya Ohashi, Yukihisa Wada, Mai Sugawara, Tomoya Kumagai
IMEC, Belgium Quoc Toan Le, Els Kesters, Yusuke Oniki, Jens Rip, Frank Holsteyns
© 2019 TOKYO OHKA KOGYO CO., LTD. 2 OUTLINE
1. Introduction
2. Design of Ru wet etch chemical
3. CVD-Ru Bulk properties
4. Summary
© 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 3 OUTLINE
1. Introduction
2. Design of Ru wet etch chemical
3. CVD-Ru Bulk properties
4. Summary
© 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 4 ALTERNATIVE METAL FOR INTERCONNECT
Ruthenium has been recently considered as a promising candidate to replace copper and cobalt as MOL and BEOL interconnect material.
✔ Low resistivity in the scaled dimensions ✔ Better EM
[Marleen H. van der Veen et al, IITC2018, IMEC]
© 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 5 TARGET RUTHENIUM WET-ETCH APPLICATIONS
Ru Bevel and Backside clean Liner/Metal deposition BV/BS clean CMP
Ru recess for FULLY SELF-ALIGNED VIAS
After M1 CMP M2V1 Etching M2 Fill
Metal recess
[Efrain Altamirano Sanchez, IITC2018 Short course, IMEC]
© 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 6 RUTHENIUM IN THE PERIODIC TABLE
The periodic table
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
H He
Li Be B C N O F Ne Platinum-Group Metal Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg TI Pb Bi Po At Rn
Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg Cn Hn FI Mc Lv Ts Og
La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
© 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 7 CHEMICAL RESISTANCE OF RUTHENIUM
Commodity Pourbaix diagram of Ru-water system CVD-Ru* E.R. @R.T. chemistry
HCl 0.0nm/min CAN
H2SO4 0.0nm/min
HNO3 0.0nm/min HF 0.0nm/min NaOCl
H2O2 0.0nm/min SC2 SC1 0.0nm/min H2O2 SC2 0.0nm/min SC1 NH3 0.0nm/min KOH 0.0nm/min TMAH 0.0nm/min
** CAN+HNO3 1.1nm/min NaOCl 5% 11.9nm/min [M. Pourbaix, Atlas of Electrochemical Equilibria in Aqueous Solutions * As depo CVD-Ru p. 346, National Association of Corrosion Engineers, 1974-644]
** 50mM CAN (Ceric Ammonium Nitrate) + HNO3 1M Strong oxidizers (CAN, NaOCl, ...) can etch ruthenium.
+ - 0 Ru(s) + 4H2O ⇔ RuO4 + 8H + 8e E = 1.032V © 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 8 OUTLINE
1. Introduction
2. Design of Ru wet etch chemical
3. CVD-Ru Bulk CVD-Ru Bulk properties
4. Summary
© 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 9 DESIGN OF RUTHENIUM WET ETCH CHEMICAL
TOK Ruthenium Wet Etch chemical is targeting the following requirements.
Metal free solution
Metal impurities should be avoided for advanced semiconductor processing.
Currently, most of the strong oxidizers include metal elements. (CAN, NaOCl etc.)
High selectivity to low-k, SiOx, SiNx, TiN and TaN
Prevent ruthenium tetroxide (RuO4) generation
Volatile and toxic RuO4 should be avoided for EHS reasons.
Preservation of surface roughness to be targeted after controlled Ru recess
© 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 10 DESIGN OF RUTHENIUM WET ETCH CHEMICAL
Metal free solution
Metal impurities should be avoided for advanced semiconductor processing.
Currently, most of the strong oxidizers include metal elements. (CAN, NaOCl etc.)
High selectivity to low-k, SiOx, SiNx, TiN and TaN
Prevent ruthenium tetroxide (RuO4) generation
Volatile and toxic RuO4 should be avoided for EHS reasons.
Preservation of surface roughness to be targeted after controlled Ru recess
Chemical Metal Ru etching Low-k (2.55) SiN TiN TaN NaOCl Yes Good - - - - CAN Yes Good - - - - Chemical A No Good <0.1nm/min <0.1nm/min <0.1nm/min <0.1nm/min Chemical B No Good <0.1nm/min <0.1nm/min <0.1nm/min <0.1nm/min Chemical C No Good <0.1nm/min <0.1nm/min <0.1nm/min <0.1nm/min
© 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 11 DESIGN OF RUTHENIUM WET ETCH CHEMICAL
Metal free solution
Metal impurities should be avoided for advanced semiconductor processing.
Currently, most of the strong oxidizers include metal elements. (CAN, NaOCl etc.)
High selectivity to low-k, SiOx, SiNx, TiN and TaN
Prevent ruthenium tetroxide (RuO4) generation
Volatile and toxic RuO4 should be avoided for EHS reasons.
Preservation of surface roughness to be targeted after controlled Ru recess
© 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 12 RUTHENIUM TETROXIDE
Mechanism of RuO4 toxic gas generation
Ru(s) + *CAN(Ⅳ) ⇒ RuO4↑ + Ce(Ⅲ)↓
*CAN (Ceric Ammonium Nitrate)
Ruthenium tetroxide is volatile and toxic.
Furthermore, RuO4 is a strong oxidizer.
[H. Aoki et. al Extended Abstracts of the 2001 International Conference on Solid State Device and Materials. 2001]
Staining reaction by OsO Plastic coloration by RuO4 reaction 4 O O O O RuO and OsO are used as staining agent for 4 4 Os TEM observation of polymeric materials. Os O O O O
OsO4 : Oxidize unsaturated type polymer C C C C
RuO4 : Oxidize saturated and unsaturated type polymer H H H H
Staining reaction can be used to detect the generation of RuO4 © 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 13 RUTHENIUM TETROXIDE GENERATION TEST PLASTIC COLORATION BY RUTHENIUM TETROXIDE GAS Bottle A : Reference Plastic
2days
Chemical
Bottle B : Ru wafer dipping (Bottle C : Ru Powder dipping)
RuO4 RuO4
RuO 2days CVD-Ru/40ml RuO 4 RuO4 4 (2×2cm, 30nm) Check discoloration of the RuO RuO or 4 4 plastic on top of the bottle Ru powder 0.01g/10ml
© 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 14 RESULT OF PLASTIC COLORATION TEST PLASTIC COLORATION BY RUTHENIUM TETROXIDE GAS w/Ru WF w/Ru powder Chemical Bottle A w/o Ru Bottle B w/Ru WF Bottle C w/Ru powder NaOCl NaOCl NaOCl No change Change to black Change to black CAN No change Change to black Change to black Chemical A No change Change to black Change to black CAN Chemical B No change No change No change CAN Chemical C No change No change No change
SEM-EDX of plastic C Ru Chemical A Chemical A O
Chemical B Chemical B
Chemical C Chemical C
Chemical B and C can prevent RuO4 gas
© 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 15 OUTLINE
1. Introduction
2. Design of Ru wet etch chemical
3. CVD-Ru Bulk properties
4. Summary
© 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 16 CVD RUTHENIUM BULK PROPERTIES
IMPACT OF THERMAL BUDGET OF POST DEPOSITION ANNEAL IN N2/H2 (FGA)
© 2019 TOKYO OHKA KOGYO CO., LTD. 17 IMPACT ON ETCHING BEHAVIOR
IMPACT OF THERMAL BUDGET OF POST DEPOSITION ANNEAL IN N2/H2 (FGA) By NaOCl 5% wet etching @R.T. (See SPCC2019 Q.T. Le for more detail)
Etching rate decrease and delay for higher anneal temp.
Passivation by surface oxide?
© 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 18 RUTHENIUM OXIDE GROWTH
IMPACT OF THERMAL BUDGET OF POST DEPOSITION ANNEAL IN N2/H2 (FGA)
© 2019 TOKYO OHKA KOGYO CO., LTD. 19 RUTHENIUM WET ETCHING BEHAVIOR
NaOCl 5% @R.T. CAN50mM+HNO3 @R.T.
Chemical C @R.T. Chemical C @35°C
Chemical C @35°C can break through
the passivation layer in© a201 short9 TOKYO OHKAtime KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 20 DESIGN OF RUTHENIUM WET ETCH CHEMICAL
Metal free solution
Metal impurities should be avoided for advanced semiconductor processing.
Currently, most of the strong oxidizers include metal elements. (CAN, NaOCl etc.)
High selectivity to low-k, SiOx, SiNx, TiN and TaN
Prevent ruthenium tetroxide (RuO4) generation
Volatile and toxic RuO4 should be avoided for EHS reasons.
Preservation of surface roughness to be targeted after controlled Ru recess
© 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 21 SURFACE ROUGHNESS
30nm CVD-Ru (FGA 420°C 20min) AFM 5×5um2 NaOCl CAN+HNO Chemical C Chemical C@35°C Reference 3 4.8nm etch 9.9nm etch 6.8nm etch 8.8nm etch
2.5
2 : Pit corrosion 1.5 Rq Ra 1 : Particle
0.5 Surface roughness
0 Ref. NaOCl CAN+HNO3 Chemical C Chemical C @35C No significant surface roughness change observed with Chemical C
© 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 22 OUTLINE
1. Introduction
2. Design of Ru wet etch chemical
3. CVD-Ru Bulk properties
4. Summary
© 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 23 Summary
New chemical is developed for Ru BV/BS clean and controlled recess.
TOK Ru etching chemical targets the following requirements a. Metal free process (no need for an additional clean step)
b. Eco and tool friendly process (no RuO4 by product) c. Preservation of surface roughness after controlled Ru recess d. High selectivity to dielectrics and barrier metals
Chemical Metal RuO4 by product Ru etching Roughness Selectivity* NaOCl Yes Yes Good Non uniform - CAN Yes Yes Good Non uniform - Chemical B No Undetected Good Good Good Chemical C No Undetected Good Good Good
*low-k, SiN, TiN and TaN
© 2019 TOKYO OHKA KOGYO CO., LTD. ©2019 Tokyo Ohka Kogyo Co., Ltd 24
Thank you for your kind attention.
© 2019 TOKYO OHKA KOGYO CO., LTD.