Alucone Interlayers to Minimize Stress Caused by Thermal Expansion Mismatch between Al2O3 Films and Teflon Substrates

作者：Jen Shih Hui; George Steven M^*

来源：ACS Applied Materials & Interfaces, 2013, 5(3): 1165-1173.

DOI：10.1021/am303077x

• thermal stress
• Al2O3
• Teflon
• atomic layer deposition
• molecular layer deposition
• alucone

Alucone films were employed as interlayers to minimize stress caused by thermal expansion mismatch between Al2O3 films grown by atomic layer deposition (ALD) and Teflon fluorinated ethylene propylene (FEP) substrates. The alucone films were grown by molecular layer deposition (MLD) using trimethylaluminum (TMA), ethylene glycol (EG), and H2O. Without the alucone interlayer, the Al2O3 films were susceptible to cracking resulting from the high coefficient of thermal expansion (CTE) mismatch between the Al2O3 film and the Teflon PEP substrate. Cracking was observed by field emission scanning electron microscopy (FE-SEM) images of Al2O3 films grown directly on Teflon FEP substrates at temperatures from 100 to 160 degrees C and then cooled to room temperature. With an alucone interlayer, the Al2O3 film had a crack density that was reduced progressively versus alucone interlayer thickness. For Al2O3 film thicknesses of 48 nm deposited at 135 degrees C, no cracks were observed for alucone interlayer thicknesses >60 nm on 50 mu m thick Teflon FEP substrates. For thinner Al2O3 film thicknesses of 21 nm deposited at 135 degrees C, no cracks were observed for alucone interlayer thicknesses >40 nm on 50 mu m thick Teflon FEP substrates. Slightly higher alucone interlayer thicknesses were required to prevent cracking on thicker Teflon FEP substrates with a thickness of 125 mu m. The alucone interlayer linearly reduced the compressive stress on the Al2O3 film caused by the thermal expansion mismatch between the Al2O3 coating and the Teflon FEP substrate. The average compressive stress reduction per thickness of the alucone interlayer was determined to be 8.5 +/- 2.3 MPa/nm. Comparison of critical tensile strains for alucone films on Teflon FEP and HSPEN substrates revealed that residual compressive stress in the alucone film on Teflon FEP could help offset applied tensile stress and lead to the attainment of much higher critical tensile strains.

• 出版日期2013-2-13