Atomic layer etching of InP using a low angle forward reflected Ne neutral beam

232

162

The ability to achieve near-atomic precision in etching different materials when transferring lithographically defined templates is a requirement of increasing importance for nanoscale structure fabrication in the semiconductor and related industries. The use of ultra-thin gate dielectrics, ultra thin channels, and sub-20 nm film thicknesses in field effect transistors and other devices requires near-atomic scale etching control and selectivity. There is an emerging consensus that as critical dimensions approach the sub-10 nm scale, the need for an etching method corresponding to Atomic Layer Deposition (ALD), i.e. Atomic Layer Etching (ALE), has become essential, and that the more than 30-year quest to complement/replace continuous directional plasma etching (PE) methods for critical applications by a sequence of individual, self-limited surface reaction steps has reached a crucial stage. A key advantage of this approach relative to continuous PE is that it enables optimization of the individual steps with regard to reactant adsorption, self-limited etching, selectivity relative to other materials, and damage of critical surface layers. In this overview we present basic approaches to ALE of materials, discuss similarities/crucial differences relative to thermal and plasma-enhanced ALD, and then review selected results on ALE of materials aimed at pattern transfer. The overview concludes with a discussion of opportunities and challenges ahead. A requirement of increasing importance for nanoscale device fabrication is the ability to achieve atomic scale etching control and materials selectivity during pattern transfer.1-8 An etching method corresponding to Atomic Layer Deposition (ALD), i.e. Atomic Layer Etching (ALE), is expected to satisfy these needs as critical dimensions continue to shrink below the 10 nm scale.Demonstrations of self-limited dry etching methods capable of near-atomic resolution have a long history in the dry etching community and a brief review will be presented below. Key challenges for these approaches have been specialized equipment, long process times and low throughput.9,10 However, a recent demonstration using a commercial plasma etch tool 10 and activities within the dry etching community 11 provide indications that the situation has changed, and that we may have reached for ALE the Tipping Point which Gladwell defined as the "the moment of critical mass, the threshold, the boiling point" when "ideas and products and messages and behaviors spread like viruses do".12 This is due to several factors, including unprecedented demands on dry etching technology introduced by the semiconductor device evolution according to Moore's law that can be satisfied by atomic layer etching, advanced capabilities in plasma etch, and the existence of a critical level of information on plasma etch and ALD methods as applied in the semiconductor fabrication space.In this article we will provide a review of background of these approaches, and focus on issues that have to be overcome for widespread implement...

Section: Iii-v: Gaasmentioning

confidence: 99%

Atomic Layer Etching at the Tipping Point: An Overview

Oehrlein

Metzler

2015

232

162

“…Using this approach, ALEt has been reported for Si, 2,3,[8][9][10][11][12] Ge, 6,13 and compound semiconductors. [14][15][16][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.…”

mentioning

confidence: 99%

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

Lee

DuMont

George

2015

118

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...

“…For example, Metzler et al 2 have reported such a mechanism to remove an atomic layer of SiO 2 using a combination of C 4 F 8 plasma to create a surface fluorocarbon (FC) layer followed by an ion bombardment with low-energy Ar + ions to remove the surface FC layer. Park et al 3 have reported a similar mechanism for atomic z E-mail: satyarth.suri@intel.com layer removal of Si using a combination of Cl 2 adsorption and Ne neutral beam. Such atomic layer etching processes have also been reported for GaAs 5 and Ge.…”

Section: What Is Atomic Layer Etching?mentioning

confidence: 97%

“…They have demonstrated InP recess stopping on an InAlAs/InGaAs transistor channel. 3,4 The benefit of the ALEt process was observed by fabricating transistors with superior Hall mobilities relative to devices patterned with conventional plasma processes. They have also used a Ne neutral beam for ALEt of GaAs and demonstrated preservation of the surface stoichiometry, which was not achieved through a continuous ICP plasma etch.…”

Section: Potential Applications For Atomic Layer Etchingmentioning

confidence: 99%

“…The idealized sequence described in Figure 1a-1d enables formation of an anisotropic atomic layer removal of material. Several reports are present in the literature [2][3][4][5][6][7][8] where variations of the idealized flow have been successfully demonstrated. A requirement for this flow, and hence somewhat of a limitation, is that the modified surface layer released during the process in Figure 1c should be a stable volatile by-product so that it can be efficiently pumped out of the process chamber.…”

Section: What Is Atomic Layer Etching?mentioning

confidence: 99%

See 1 more Smart Citation

Atomic Layer Etching: An Industry Perspective

Carver

Plombon

Romero

et al. 2015

145

128

This paper provides an industry perspective on atomic layer etching (ALEt) process. Two process sequences representing two different methods of ALEt are described, followed by several examples where ALEt can be an enabling process technology in the semiconductor industry. The authors believe that there needs to be an increased understanding of surface functionalization, modification and chemistry-based material removal. We are confident that this review article will allow for increased scientific and technological solutions for enabling ALEt.