Chemistry for Positive Pattern Transfer Using Area‐Selective Atomic Layer Deposition

Abstract

This paper demonstrates a new chemically selective method for achieving high-resolution, area-selective atomic layer deposition (ALD) of Pt thin films on dielectrics. By utilizing the intrinsically selective adsorption behavior of 1-octadecene, a monolayer resist is attached only to the hydride-terminated silicon surfaces, but not to the oxide surfaces, of an oxide-patterned silicon substrate. Subsequently, a Pt thin film is selectively deposited only onto the non-deactivated oxide regions by ALD.ALD is a powerful thin-film growth technique that uses sequential self-terminating surface reaction steps to afford subnanometer control of the growth process. [1,2] It has received significant attention recently as a method for depositing highquality thin films of insulators, semiconductors, and metals. The surface-reaction-controlled deposition mechanism ensures precise control of the film thickness, excellent conformality, and very good uniformity over large areas. [2] In addition, many ALD processes are very sensitive to the conditions of the substrate surfaces. As a consequence, the surface functional groups can be manipulated prior to ALD to carry out an area-selective ALD process. Instead of a conventional subtractive-patterning strategy, area-selective ALD is an additive process, in which material is deposited only where needed. Figure 1 illustrates dual pathways for achieving area-selective ALD on a patterned SiO 2 /Si surface. Patterned SiO 2 /Si is an excellent starting substrate, because conventional photolithography can be used to form an oxide pattern of arbitrary design on silicon with a size down to the submicrometer scale. We will show that with the appropriate choice of chemistry, this single patterned substrate can be used to achieve either positive or negative pattern transfer using area-selective ALD. The overall processes of negative and positive patterning require two chemically selective steps. These two methods are complementary.The negative-patterning method shown in Figure 1 has been introduced previously.[3] In the prior work, octadecyltrichlorosilane (ODTS) was selectively attached to a SiO 2 surface as shown, leaving the hydride-terminated silicon surface unreacted. Subsequently, HfO 2 was deposited selectively by using the ALD process only on the hydride regions.[3]In this work, we utilize hydrosilylation chemistry of 1-alkenes on hydride-terminated silicon. The reaction is selective, leading to the adsorption of 1-alkene on the hydride surface but not on the oxide surface of a patterned silicon substrate. Subsequently, a thin film is selectively deposited only onto the oxide regions by ALD.We have focused on the deposition of Pt for the positivepatterning area-selective ALD method presented here. Pt is a promising electrode material for dynamic random-access memories because of its high chemical stability in an oxidizing atmosphere and its excellent electrical properties. [4,5] It is also a promising gate-metal candidate owing to its high work function (5.6 eV) and compatibility with high-...

Issues and Challenges in Vapor-Deposited Top Metal Contacts for Molecule-Based Electronic Devices

“…ALD via deposition of organometallic complexes has been used to prepare the top contact between metal and SAMs [90][91][92][93]. The concept of ALD is quite similar to CVD in terms of using organometallic precursors rather than a metal atom vapor.…”

Nanopatterning by Area‐Selective Atomic Layer Deposition

“…For example, ODTS preferentially reacts with an OHterminated surface while an alkene preferentially reacts with a H-terminated surface [33,100,101]. If a substrate with patterns of OH-and H-terminated regions is exposed to ODTS or alkenes, under proper conditions a SAM can be selectively formed for each surface termination [49,68]. This allows the patterns of surface termination to be propagated into a pattern of SAMS, which in turn provide a pathway to fabricate the final film pattern through AS-ALD.…”

“…By utilizing this property of the SAMs, the patterning step can be simplified through the use of predefined substrate patterns. Chen and Bent have used this approach with a prepatterned substrate combined with selective SAM formation to carry out AS-ALD [49]. They reported both positive and negative patterning using this concept as shown in Figure 9.8.…”

Review Article: Catalysts design and synthesis via selective atomic layer deposition

“…The area-selective ALD has been applied to fabricate defect-free 3D patterns and nanostructures for electronic applications. 32,33 In catalysis, the motivations of selective-ALD enable directionally and precisely tailoring of the structural parameters, interfaces, and active sites, that is of great significance for advanced catalysis. In this article, fabrication of composite catalysts via selective ALD methods is introduced.…”

“…A patterned area of substrate is initially activated or passivated with assistance of electron/ ion beam, self-assembled monolayers (SAMs), or polymer resists. 31,32 Then during the deposition, materials can be deposited only where needed. The area-selective ALD has been applied to fabricate defect-free 3D patterns and nanostructures for electronic applications.…”