Plasma-Induced Damage in High-$k$/Metal Gate Stack Dry Etch

Hussain, Muhammad Mustafa; Song, Seung-Chul; Barnett, Joel; Kang, Chang Yong; Gebara, G.; Sassman, B.; Moumen, N.

doi:10.1109/led.2006.886327

Cited by 20 publications

(8 citation statements)

References 17 publications

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“…The thermal ALE approach avoids any damage to the underlying substrate resulting from high energy ions or energetic neutrals. Ions from plasmas have been implicated in the performance degradation of high-k/metal gate stacks . Using neutral noble gas beams is able to mitigate the structural and electrical damage caused by ions …”

Section: Resultsmentioning

confidence: 99%

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Atomic Layer Etching of Al₂O₃ Using Sequential, Self-Limiting Thermal Reactions with Sn(acac)₂ and Hydrogen Fluoride

2015

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The atomic layer etching (ALE) of Al2O3 was demonstrated using sequential, self-limiting thermal reactions with tin(II) acetylacetonate (Sn(acac)2) and hydrogen fluoride (HF) as the reactants. The Al2O3 samples were Al2O3 atomic layer deposition (ALD) films grown using trimethylaluminum and H2O. The HF source was HF-pyridine. Al2O3 was etched linearly with atomic level precision versus number of reactant cycles. The Al2O3 ALE was monitored at temperatures from 150 to 250 °C. Quartz crystal microbalance (QCM) studies revealed that the sequential Sn(acac)2 and HF reactions were self-limiting versus reactant exposure. QCM measurements also determined that the mass change per cycle (MCPC) increased with temperature from -4.1 ng/(cm(2) cycle) at 150 °C to -18.3 ng/(cm(2) cycle) at 250 °C. These MCPC values correspond to etch rates from 0.14 Å/cycle at 150 °C to 0.61 Å/cycle at 250 °C based on the Al2O3 ALD film density of 3.0 g/cm(3). X-ray reflectivity (XRR) analysis confirmed the linear removal of Al2O3 and measured an Al2O3 ALE etch rate of 0.27 Å/cycle at 200 °C. The XRR measurements also indicated that the Al2O3 films were smoothed by Al2O3 ALE. The overall etching reaction is believed to follow the reaction Al2O3 + 6Sn(acac)2 + 6HF → 2Al(acac)3 + 6SnF(acac) + 3H2O. In the proposed reaction mechanism, the Sn(acac)2 reactant donates acac to the substrate to produce Al(acac)3. The HF reactant allows SnF(acac) and H2O to leave as reaction products. The thermal ALE of many other metal oxides using Sn(acac)2 or other metal β-diketonates, together with HF, should be possible by a similar mechanism. This thermal ALE mechanism may also be applicable to other materials such as metal nitrides, metal phosphides, metal sulfides and metal arsenides.

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Section: Resultsmentioning

confidence: 99%

“…Ions from plasmas have been implicated in the performance degradation of high-k/ metal gate stacks. 42 Using neutral noble gas beams is able to mitigate the structural and electrical damage caused by ions. 8 ALE based on ion or neutral noble atom bombardment also requires line-of-sight to the substrate.…”

Section: Resultsmentioning

confidence: 99%

Atomic Layer Etching of Al₂O₃ Using Sequential, Self-Limiting Thermal Reactions with Sn(acac)₂ and Hydrogen Fluoride

2015

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“…The thermal ALEt approach avoids any damage to the underlying substrate resulting from high energy ions or energetic neutrals. 59 ALEt based on ion or neutral noble atom bombardment requires line-of-sight to the substrate. This requirement can be used advantageously to minimize undercutting with directional ions or energetic neutral atoms during ALEt.…”

Section: Extensions To Other Materials and Advantages Of Thermal Alet-mentioning

confidence: 99%

Atomic Layer Etching of HfO₂Using Sequential, Self-Limiting Thermal Reactions with Sn(acac)₂and HF

Lee

DuMont

George

2015

ECS J. Solid State Sci. Technol.

118

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The atomic layer etching (ALEt) of HfO 2 was performed using sequential, self-limiting thermal reactions with tin(II) acetylacetonate (Sn(acac) 2 ) and HF as the reactants. The HF source was a HF-pyridine solution. The etching of HfO 2 was linear with atomic level control versus number of Sn(acac) 2 and HF reaction cycles. The HfO 2 ALEt was measured at temperatures from 150-250 • C. Quartz crystal microbalance (QCM) measurements determined that the mass change per cycle (MCPC) increased with temperature from −6.7 ng/(cm 2 cycle) at 150 • C to −11.2 ng/(cm 2 cycle) at 250 • C. These MCPC values correspond to etch rates from 0.070 Å/cycle at 150 • C to 0.117 Å/cycle at 250 • C. X-ray reflectivity analysis confirmed the linear removal of HfO 2 and measured an HfO 2 ALEt etch rate of 0.11 Å/cycle at 200 • C. Fourier transform infrared (FTIR) spectroscopy measurements also observed HfO 2 ALEt using the infrared absorbance of the Hf-O stretching vibration. FTIR analysis also revealed absorbance features consistent with HfF 4 or HfF x surface species as a reaction intermediate. The HfO 2 etching is believed to follow the reaction: HfO 2 + 4Sn(acac) 2 + 4HF → Hf(acac) 4 + 4SnF(acac) + 2H 2 O. In the proposed reaction mechanism, Sn(acac) 2 donates acac to the substrate to produce Hf(acac) 4 . HF allows SnF(acac) and H 2 O to leave as reaction products. The thermal ALEt of many other metal oxides, as well as metal nitrides, phosphides, sulfides and arsenides, should be possible by a similar mechanism. Atomic layer etching (ALEt) is a thin film removal technique based on sequential, self-limiting surface reactions.1-3 ALEt can be viewed as the reverse of atomic layer deposition (ALD). 4 ALEt is able to remove thin films with atomic layer control. ALD and ALEt are able to provide the necessary processing techniques for surface engineering at the atomic level. 5,6 This atomic level control is needed for the nanofabrication of a wide range of nanoscale devices. 7Until recently, ALEt processes have been reported using only ionenhanced or energetic noble gas atom-enhanced surface reactions. [1][2][3] In these ALEt processes, a halogen is adsorbed on the surface of the material. Subsequently, ion or noble gas atom bombardment is used to desorb halogen compounds that etch the material. Using this approach, ALEt has been reported for Si,2,3,[8][9][10][11][12] Ge, 6,13 and compound semiconductors.14-17 ALEt has also been demonstrated for a variety of metal oxides. 7,[18][19][20] Additional ALEt studies have been conducted on various carbon substrates. 21-23The ALEt of Al 2 O 3 was recently reported using sequential, selflimiting thermal reactions with Sn(acac) 2 and HF as the reactants. 24The linear removal of Al 2 O 3 was observed at temperatures from 150-250• C without the use of ion or noble gas atom bombardment. Al 2 O 3 ALEt etch rates varied with temperature from 0.14 Å/cycle at 150• C to 0.61 Å/cycle at 250• C. 24 The Sn(acac) 2 and HF thermal reactions were both self-limiting versus reactant exposure. In addition, the Al 2...

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“…Therefore, in the gate dielectric etch processing of nanoscale MOSFET devices, precise control of the etch rate (depth) has become a greater prerequisite than achieving a high etch rate due to the extreme thinness of the gate dielectric material. In addition, the etched surface and the gate dielectric material must remain undamaged for the gate dielectric processing of nanoscale devices [7,8]. However, conventional RIE tends to cause electrical and physical damage to the surface of the devices due to use of energetic reactive ions and the difficulty in the precise etch rate (depth) control at an atomic scale.…”

Section: Introductionmentioning

confidence: 99%

Photoassisted Kelvin Probe Force Microscopy on Multicrystalline Si Solar Cell Materials

Takahashi

2011

Jpn. J. Appl. Phys.

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Precise etch depth control of ultra-thin HfO 2 (3.5 nm) films applied as a gate oxide material was investigated by using atomic layer etching (ALET) with an energetic Ar beam and BCl 3 gas. A monolayer etching condition of 1.2 Å/cycle with a low surface roughness and an unchanged surface composition was observed for ultra-thin, ALET-etched HfO 2 by supplying BCl 3 gas and an Ar beam at higher levels than the critical pressure and dose, respectively. When HfO 2 -nMOSFET devices were fabricated by ALET, a 70% increase in the drain current and a lower leakage current were observed compared with the device fabricated by conventional reactive ion etching, which was attributed to the decreased structural and electrical damage.

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Plasma-Induced Damage in High-$k$/Metal Gate Stack Dry Etch

Cited by 20 publications

References 17 publications

Atomic Layer Etching of Al₂O₃ Using Sequential, Self-Limiting Thermal Reactions with Sn(acac)₂ and Hydrogen Fluoride

Atomic Layer Etching of Al₂O₃ Using Sequential, Self-Limiting Thermal Reactions with Sn(acac)₂ and Hydrogen Fluoride

Atomic Layer Etching of HfO₂Using Sequential, Self-Limiting Thermal Reactions with Sn(acac)₂and HF

Photoassisted Kelvin Probe Force Microscopy on Multicrystalline Si Solar Cell Materials

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Plasma-Induced Damage in High-$k$/Metal Gate Stack Dry Etch

Cited by 20 publications

References 17 publications

Atomic Layer Etching of Al2O3 Using Sequential, Self-Limiting Thermal Reactions with Sn(acac)2 and Hydrogen Fluoride

Atomic Layer Etching of Al2O3 Using Sequential, Self-Limiting Thermal Reactions with Sn(acac)2 and Hydrogen Fluoride

Atomic Layer Etching of HfO2Using Sequential, Self-Limiting Thermal Reactions with Sn(acac)2and HF

Photoassisted Kelvin Probe Force Microscopy on Multicrystalline Si Solar Cell Materials

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Product

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Atomic Layer Etching of Al₂O₃ Using Sequential, Self-Limiting Thermal Reactions with Sn(acac)₂ and Hydrogen Fluoride

Atomic Layer Etching of Al₂O₃ Using Sequential, Self-Limiting Thermal Reactions with Sn(acac)₂ and Hydrogen Fluoride

Atomic Layer Etching of HfO₂Using Sequential, Self-Limiting Thermal Reactions with Sn(acac)₂and HF