Selective atomic layer deposition on flexible polymeric substrates employing a polyimide adhesive as a physical mask

Abstract

The rise of low-temperature atomic layer deposition (ALD) has made it very attractive to produce high-κ dielectric for flexible electronic devices. Similarly, selective deposition of ALD films is of great relevance for circuitry. We demonstrated a simple method of using a physical mask to block the film’s growth in selected polymeric and flexible substrate areas during a low-pressure ALD process. A low-cost silicone adhesive polyimide tape was used to manually mask selected areas of bare substrates and aluminum strips deposited by evaporation. 190 cycles of aluminum oxide (Al2O3) and hafnium oxide (HfO2) were deposited at temperatures ranging from 100 to 250 °C. Using x-ray photoelectron spectroscopy (XPS) analysis and energy dispersive x-ray spectroscopy (EDS), we showed that the mask was effective in protecting the areas under the tape. The mask did not show any modification of shape for an exposure of 10 h at 250 °C, hence keeping the form of the masked area intact. An analysis of the unmasked area by ellipsometry (632.8 nm) and x ray shows a regular film with a thickness variation under 2 nm for a given temperature and constant refractive index. EDS, selected-area XPS, and imaging XPS show an evident change of elemental content at the interface of two areas. By XPS, we established that the structure of the films was not affected by the mask, the films were stoichiometric, and there was no effect of outgassing from the adhesive film.

Crystallinity Effect on Electrical Properties of PEALD–HfO2 Thin Films Prepared by Different Substrate Temperatures

“…D. Blaschke et al [ 30 ] studied the hydrogen impurity level in thermal ALD deposited HfO 2 films using tetrakis(dimethylamino)hafnium (TDMAHf) precursor and water at the growth temperature between 100 °C and 350 °C. In 2021, Matin Forouzmehr et al [ 31 ] deposited HfO 2 films on flexible polymeric substrates at temperatures changing from 100 to 250 °C. Although a lot of effort has been carried out to investigate the stability and interface chemistry of HfO 2 films at a variety of temperatures, there exists much less literature about the effects of crystalline behavior on the electrical properties of HfO 2 films.…”

Area Selective Deposition of Metal Films Using Temperature Sensitive Masking Materials and Plasma Electrons as Reducing Agents

“…16,17 Another approach is to block areas of the substrate by applying a layer of masking materials such as polymers. 18,19 The latter method offers a cheap and easy way to achieve selective deposition, not only on large areas but also on micro/nano dimensions.…”