Research Progress on Advanced Atomic Layer Etching Materials and Key Processes AITranslate

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S B Bai，Z H Chen，H H Zhang，G J Chen，S C Cao，S B Zhang. Rate optimization of atomic layer etching process of silicon ［J］. Acta Physica Sinica，2023，72（21）：215214.

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［33］Li C，Zhu H，Zhang Y，Yin X，Jia K，Li J，Wang G，Kong Z，Du A，Yang T，Zhao L，Huang W，Xie L，Li Y，Ai X，Ma S，Radamson H H. Selective digital etching of silicon-germanium using nitric and hydrofluoric acids ［J］. ACS Applied Materials & Interfaces，2020，12（42）：48170.

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［39］Burnham S D，Boutros K，Hashimoto P，Butler C，Wong D，Hu M，Micovic M. Gate‐recessed normally‐off GaN‐on‐Si HEMT using a new O2‐BCl3 digital etching technique ［J］. Physica Status Solidi C，2010，7（7-8）：2010.

［40］Hwang I H，Cha H Y，Seo K S. Low-damage and self-limiting （Al）GaN etching process through atomic layer etching using O2 and BCl3 plasma ［J］. Coatings，2021，11（3）：268.

［41］Hu Q，Li S，Li T，Wang X，Li X，Wu Y. Channel engineering of normally-off AlGaN/GaN MOS-HEMTs by atomic layer etching and high-k dielectric ［J］. IEEE Electron Device Letters，2018，39（9）：1377.

［42］Ohba T，Yang W，Tan S，Kanarik K J，Nojiri K. Atomic Layer Etching of GaN/AlGaN ［A］.38th International Symposium on Dry Process ［C］. Japan：Sapporo，2016. 17.

［43］Fukumizu H，Sekine M，Hori M，Kanomaru K，Kikuchi T. Atomic layer etching of AlGaN using Cl2 and Ar gas chemistry and UV damage evaluation ［J］. Journal of Vacuum Science & Technology A：Vacuum，Surfaces，and Films，2019，37（2）：021002.

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［47］Sherpa S D，Ranjan A. Quasi-atomic layer etching of silicon nitride ［J］. Journal of Vacuum Science & Technology A：Vacuum，Surfaces，and Films，2017，35（1）：01A102.

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［51］Hirata A，Fukasawa M，Tercero J U，Kugimiya K，Hagimoto Y，Karahashi K，Hamaguchi S，Iwamoto H. Five-step plasma-enhanced atomic layer etching of silicon nitride with a stable etched amount per cycle ［J］. Japanese Journal of Applied Physics，2022，61（6）：066002.

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［53］Kim J，Kang H，Kim Y，Jeon M，Chae H. Low global warming C5F10O isomers for plasma atomic layer etching and reactive ion etching of SiO2 and Si3N4 ［J］. Plasma Processes and Polymers，2024，21（5）：1.

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［59］Yoon M Y，Yeom H J，Kim J H，Chegal W，Cho Y J，Kwon D，Jeong J，Lee H. Discharge physics and atomic layer etching in Ar/C4F6 inductively coupled plasmas with a radio frequency bias ［J］. Physics of Plasmas，2021，28（6）：063504.

［60］Kim S Y，Park I S，Ahn J. Atomic layer etching of SiO2 using trifluoroiodomethane ［J］. Applied Surface Science，2022，589：153045.

［61］Kim Y，Kang H，Kim C，Chae H. Plasma atomic layer etching of SiO2 and Si3N4 with low global warming C4H3F7O isomers ［J］. ACS Sustainable Chemistry & Engineering，2023，11（16）：6136.

［62］Lin K Y，Li C，Engelmann S，Bruce R L，Joseph E A，Metzler D，Oehrlein G S. Achieving ultrahigh etching selectivity of SiO2 over Si3N4 and Si in atomic layer etching by exploiting chemistry of complex hydrofluorocarbon precursors ［J］. Journal of Vacuum Science & Technology A，2018，36（4）：040601.

［63］Tsutsumi T，Kondo H，Hori M，Zaitsu M，Kobayashi A，Nozawa T，Kobayashi N. Atomic layer etching of SiO2 by alternating an O2 plasma with fluorocarbon film deposition ［J］. Journal of Vacuum Science & Technology A，2016，35（1）：01A103.

［64］Miyoshi N，Kobayashi H，Shinoda K，Kurihara M，Kawamura K，Kouzuma Y，Izawa M. Atomic layer etching of SiO2 with self-limiting behavior on the surface modification step using sequential exposure of HF and NH3 ［J］. Journal of Vacuum Science & Technology A，2021，40（1）：012601.

［65］Gill Y J，Kim D S，Gil H S，Kim K H，Jang Y J，Kim Y E，Yeom G Y. Cyclic etching of silicon oxide using NF3/H2 remote plasma and NH3 gas flow ［J］. Plasma Processes and Polymers，2021，18（11）：2100063.

［66］Park S D，Lim W S，Park B J，Lee H C，Bae J，Yeom G. Precise depth control and low-damage atomic-layer etching of HfO2 using BCl3 and Ar neutral beam ［J］. Electrochemical and Solid State Letters，2008: 11.

［67］Park J B，Lim W S，Park B J，Park I H，Kim Y W，Yeom G Y. Atomic layer etching of ultra-thin HfO2 film for gate oxide in MOSFET devices ［J］. Journal of Physics D：Applied Physics，2009，42（5）：055202.

［68］Lim W S，Park J B，Park J Y，Park B J，Yeom G Y. Low damage atomic layer etching of ZrO2 by using BCl3 gas and Ar neutral beam ［J］. Journal of Nanoscience and Nanotechnology，2009，9（12）：7379.

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［70］Min K S，Kang S H，Kim J K，Jhon Y I，Jhon M S，Yeom G Y. Atomic layer etching of Al2O3 using BCl3/Ar for the interface passivation layer of Ⅲ–Ⅴ MOS devices ［J］. Microelectronic Engineering，2013，110：457.

［71］Lee Y，George S M. Atomic layer etching of Al2O3 using sequential，self-limiting thermal reactions with Sn（acac）2 and hydrogen fluoride ［J］. ACS Nano，2015，9（2）：2061.

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［73］Lee Y，George S M. Thermal atomic layer etching of Al2O3，HfO2，and ZrO2 using sequential hydrogen fluoride and dimethylaluminum chloride exposures ［J］. J. Phys. Chem. C，2019，123（30）：18455.

［74］Lee Y，George S M. Thermal atomic layer etching of HfO2 using HF for fluorination and TiCl4 for ligand-exchange ［J］. Journal of Vacuum Science & Technology A：Vacuum，Surfaces，and Films，2018，36（6）：061504.

［75］Gertsch J C，Cano A M，Bright V M，George S. SF4 as the fluorination reactant for Al2O3 and VO2 thermal atomic layer etching ［J］. Chemistry of Materials，2019，31（10）：3624.

［76］Sharma V，Elliott S D，Blomberg T，Haukka S，Givens M，Tuominen M，Ritala M. Thermal atomic layer etching of aluminum oxide （Al2O3） using sequential exposures of niobium pentafluoride （NbF5） and carbon tetrachloride （CCl4）：a combined experimental and density functional theory study of the etch mechanism ［J］. Chemistry of Materials，2021，33（8）：2883.

［77］Chittock N J，Vos M F J，Faraz T，（Erwin）Kessels W M M，Knoops H C M，Mackus A J M. Isotropic plasma atomic layer etching of Al2O3 using a fluorine containing plasma and Al（CH3）3 ［J］. Applied Physics Letters，2020，117（16）：162107.

［78］Lee Y，Huffman C，George S M. Selectivity in thermal atomic layer etching using sequential，self-limiting fluorination and ligand-exchange reactions ［J］. Chemistry of Materials，2016，28（21）：7657.

［79］Iwasaki A，Akanishi Y，Mazzamuto F，Kesters E，Le Q T，Holsteyns F. Study of copper surface preparation by sequential atomic layer wet etching and laser annealing treatments ［J］. ECS Transactions，2017，80（2）：233.

［80］Toyoda N，Ogawa A. Atomic layer etching of Cu film using gas cluster ion beam ［J］. Journal of Physics D：Applied Physics，2017，50（18）：184003.

［81］Mohimi E，Chu X I，Trinh B B，Babar S，Girolami G S，Abelson J R. Thermal atomic layer etching of copper by sequential steps involving oxidation and exposure to hexafluoroacetylacetone ［J］. ECS Journal of Solid State Science and Technology，2018，7（9）：P491.

［82］Gong Y，Venkatraman K，Akolkar R. Communication-electrochemical atomic layer etching of copper ［J］. Journal of The Electrochemical Society，2018，165（7）：D282.

［83］Johnson N R，George S M. WO3 and W thermal atomic layer etching using “conversion-fluorination” and “oxidation-conversion-fluorination” mechanisms ［J］. ACS Applied Materials & Interfaces，2017，9（39）：34435.

［84］Xie W，Lemaire P C，Parsons G N. Thermally driven self-limiting atomic layer etching of metallic tungsten using WF6 and O2 ［J］. ACS Applied Materials & Interfaces，2018，10（10）：9147.

［85］Xie W，Parsons G N. Thermal atomic layer etching of metallic tungsten via oxidation and etch reaction mechanism using O2 or O3 for oxidation and WCl6 as the chlorinating etchant ［J］. Journal of Vacuum Science & Technology A：Vacuum，Surfaces，and Films，2020，38（2）：022605.

［86］Kim D S，Kim J E，Lee W O，Park J W，Gill Y J，Jeong B，Yeom G. Anisotropic atomic layer etching of W using fluorine radicals/oxygen ion beam ［J］. Plasma Process Polym.，2019，16：1900081.

［87］Shim D，Kim J，Kim Y，Chae H. Plasma atomic layer etching for titanium nitride at low temperatures ［J］. Journal of Vacuum Science & Technology B，2022，40（2）：022208.

［88］Hossain A A，Wang H，Catherall D S，Leung M，Knoops H C M，Renzas J R，Minnich A J. Isotropic plasma-thermal atomic layer etching of superconducting titanium nitride films using sequential exposures of molecular oxygen and SF6/H2 plasma ［J］. Journal of Vacuum Science & Technology A，2023，41（6）：062601.

［89］Shinoda K，Miyoshi N，Kobayashi H，Izawa M，Ishikawa K，Hori M. Rapid thermal-cyclic atomic-layer etching of titanium nitride in CHF3/O2 downstream plasma ［J］. Journal of Physics D：Applied Physics，2019，52（47）：475106.

［90］Miyoshi N，Mcdowell N，Kobayashi H. Atomic layer etching of titanium nitride with surface modification by Cl radicals and rapid thermal annealing ［J］. Journal of Vacuum Science & Technology A，2022，40（3）：032601.

［91］Konh M，He C，Lin X，Guo X，Pallem V，Opila R L，Teplyakov A V，Wang Z，Yuan B. Molecular mechanisms of atomic layer etching of cobalt with sequential exposure to molecular chlorine and diketones ［J］. Journal of Vacuum Science & Technology A：Vacuum，Surfaces，and Films，2019，37（2）：021004.

［92］Wang Z，Opila R L. In operando x-ray photoelectron spectroscopy study of mechanism of atomic layer etching of cobalt ［J］. Journal of Vacuum Science & Technology A：Vacuum，Surfaces，and Films，2020，38（2）：022611.

［93］Murdzek J A，lii-Rosales A，George S M. Thermal atomic layer etching of nickel using sequential chlorination and ligand-addition reactions ［J］. Chemistry of Materials，2021，33（23）：9174.

［94］Sang X，Chen E，Chang J P. Patterning nickel for extreme ultraviolet lithography mask application I. Atomic layer etch processing ［J］. Journal of Vacuum Science & Technology A：Vacuum，Surfaces，and Films，2020，38（4）：042603.

［95］Chen J K C，Altieri N D，Kim T，Chen E，Lill T，Shen M，Chang J P. Directional etch of magnetic and noble metals. Ⅱ. Organic chemical vapor etch ［J］. Journal of Vacuum Science & Technology A，2017，35（5）：05C305.

［96］Sang G Q，Jiang R J，Wei Y Z，Li Q K，Zhang M H，Yao J X，Lu Y H，Cao L，Li J F，Qin X L，Zhang Q Z，Yin H X. Low-temperature atomic-level trimming on Ge interfused surface for gate-all-around Si nanosheets transistors ［J］. Rare Metals，2024，43（12）：6516.

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DOI：10.13373/j.cnki.cjrm.XY24060012

Chinese Library Classification Number:TF803.21

Citation Information:

For a long time，the semiconductor industry has followed Moore's Law，with transistor sizes constantly shrinking and process nodes constantly advancing. Etching technology，as an important means of pattern transfer in integrated circuit （IC） manufacturing，has long been of great concern to the industry. Currently，advanced processes in the IC industry have entered the nanoscale process node，which requires the etching process to have extremely high precision and selectivity as well as good pattern definition ability. Conventional reactive ion etching，in which reactions occur continuously and simultaneously during the etching process，can be represented by A+B. Where A represents a neutral reaction and B represents the sputtering of energetic ions above the etching threshold. Reactive ion etching is difficult to meet the high pattern fidelity requirements of certain structures （e.g.，high aspect ratio structures，three-dimensional stacked structures） due to the transport-limiting phenomenon of continuous etching，coupling of different fluxes，and so on. However，the emerging atomic layer etching technique，where the reactions during the etching process occur separately and independently，can be represented by A to B. Where A represents the modification step and B represents the removal step of the modified layer. Due to the self-limiting characteristic of the reaction process，it provides a viable solution to realize the device fabrication process with nanoscale size and precision. This article is a review article on atomic layer etching，which begins with a history of the development of etching technology and the origin of reactive ion etching. The current bottlenecks in reactive ion etching were explained，and the optimization and improvement of the process was becoming increasingly difficult and expensive. This led to the need for a revolutionary etching method other than continuous synchronization，i.e.，atomic layer etching，an advanced etching technology. The origin，concept and characteristics of atomic layer etching （ALE） were then described. In this part，the correlation between atomic layer etching and atomic layer deposition in the development of ALE technology，the understanding of the term "atomic layer" in ALE，as well as the three important test methods to characterize the excellence of the ALE process could be seen. Next，the realization of two types of atomic layer etching，namely thermal atomic layer etching and plasma atomic layer etching，was introduced. According to the different modification methods，plasma ALE could be subdivided into four types："chemical adsorption"，"deposition"，"transformation"，and "extraction"，while thermal ALE had three etching strategies："fluoride-ligand exchange"，"transformation-etching"，and "oxidation-fluoride-etching". After that，the materials that could be processed by atomic layer etching were summarized and elaborated in detail，mainly including semiconductor materials，dielectric materials，and metal materials used in IC manufacturing. Among them，semiconductor materials included first-generation semiconductor materials （Si，SiGe），second-generation semiconductors （GaAs，InP），and third-generation semiconductors （GaN，etc.）；dielectric materials included conventional dielectric materials （SiN，SiO₂）and high-K materials （HfO₂ and other metal oxides）；metal materials introduced interconnect materials （Cu，W），gate metal materials （TiN），and materials for reducing contact resistance （Co，Ni，etc.）. Finally，a summary of the whole article was made，analyzing and discussing the opportunities and challenges of ALE. It was believed that through the unremitting efforts of academia and industry，the emerging atomic layer etching technology would be as promising and broad in the future as atomic layer deposition.