Area-selective atomic layer deposition of platinum using photosensitive polyimide

Abstract

Area-selective atomic layer deposition (AS-ALD) of platinum (Pt) was studied using photosensitive polyimide as a masking layer. The polyimide films were prepared by spin-coating and patterned using photolithography. AS-ALD of Pt using poly(methyl-methacrylate) (PMMA) masking layers was used as a reference. The results show that polyimide has excellent selectivity towards the Pt deposition, after 1000 ALD cycles less than a monolayer of Pt is deposited on the polyimide surface. The polyimide film could easily be removed after ALD using a hydrogen plasma, due to a combination of weakening of the polyimide resist during Pt ALD and the catalytic activity of Pt traces on the polyimide surface. Compared to PMMA for AS-ALD of Pt, polyimide has better temperature stability. This resulted in an improved uniformity of the Pt deposits and superior definition of the Pt patterns. In addition, due to the absence of reflow contamination using polyimide the nucleation phase during Pt ALD is drastically shortened. Pt patterns down to 3.5 μm were created with polyimide, a factor of ten smaller than what is possible using PMMA, at the typical Pt ALD processing temperature of 300 °C. Initial experiments indicate that after further optimization of the polyimide process Pt features down to 100 nm should be possible, which makes AS-ALD of Pt using photosensitive polyimide a promising candidate for patterning at the nanoscale.

Atomic Layer Deposition for Graphene Device Integration

“…The figure shows the deposition of Pt by ALD on CVD graphene grown on Cu foil. The Pt was deposited using MeCpPtMe 3 precursor and O 2 gas as co‐reactant at a temperature of 300 °C . Increasing the pressure of the co‐reactant (effectively increasing the O 2 dose) results in a more selective deposition towards the wrinkles and grain boundaries of the graphene, most likely due to the diffusion of Pt.…”

Nanoscale selective area atomic layer deposition of TiO2using e-beam patterned polymers

“…7, So far, majority of the AS-ALD studies have been performed using area-deactivated approach where mostly selfassembled monolayers (SAMs) are utilized as the growthblocking layers by covering the chemically reactive sites on the substrate and exposing non-reactive groups. 7,9,23,27,[29][30][31][32][33][34][35][36][37][38][39][40] Alkyl silanes e.g., alkyl trichlorosilanes, alkyl triethoxysilanes, etc. have been exploited as mono-layered surface modiers to block ALD nucleation of various metal oxide thin lms and metallic nanoparticles/thin lms.…”

“…Moreover, preparing defect-free SAMs is not easy and generally takes extremely long synthesis times (up to 48 h). 23,31,41,48 Even with a decent quality SAM coating, growth selectivity might still be limited to a few nanometers of lm thickness. In addition, patterning of SAMs has generally been attained using nonstandard lithographic techniques such as micro-contact printing which further makes it a laborious task to obtain defect-free SAMs.…”

Graphene devices with bottom-up contacts by area-selective atomic layer deposition

“…[33][34][35] Moreover, the combination of conventional lithography and ALD introduces significant challenges such as reflowing of the resist films at the temperatures required for metal ALD. [36] Both issues can be avoided by using direct-write ALD, which is a previously introduced technique that allows bottom-up deposition of ALD contacts. [37][38][39] Briefly, direct-write ALD combines the direct-write patterning technique of electron-beam induced deposition (EBID) with ALD to fabricate high-quality platinum (Pt) structures without the need for conventional lithography, resist films or lift-off steps.…”