Investigations of Area Selective Atomic Layer Deposition

Abstract

The demand for semiconductor devices has grown over the past decades as the volume of data stored or processed have exponentially increased. To accommodate the needs, the capacity per volume was required to increase by order of magnitudes. Therefore, the scale down of the semiconductors has drawn semiconductor manufacturers’ attention. Film deposition techniques, including Atomic Layer Deposition (ALD), have been investigated as result. ALD not only has layer-by-layer control of the film, but also has superior conformality compared to Chemical Vapor Deposition (CVD), another popular film deposition technique. In the effort to further scale down from the known ALD processes, area selective ALD has been researched in Engstrom Research Group (ERG). As the possible method for area selective ALD, the natural selectivity of newly discovered chemicals and adding the third species for site blocking, reversible chemisorption, and adduct formation are proposed. Di-sec-butylaminosilane (DSBAS) showed the possibility for the area selectivity, as DSBAS showed suppressed growth on Al2O3 substrate while showing normal growth on Cu substrate. Introducing the third species, denoted as co-adsorbate, also showed the possibility for certain combinations of the precursor and co-adsorbate: Study on Zirconium(IV) tert-butoxide (ZTB) as precursor and triethylamine (TEA) or pyridine as co-adsorbate, Trimethylaluminum (TMA) as precursor and TEA or 4-methylpyridine as co-adsorbate, and Tetrakis(ethylmethylamido) zirconium(IV) (TEMAZ) as precursor and Phenyl Acetylene (PA) as co-adsorbate. All the combinations listed showed suppressed growth on one substrate but the normal growth on the other substrate. Up to certain number of ALD cycle at certain conditions. For evaluating which co-adsorbate should be investigated with our ALD experiments, DiStasio group’s calculation of binding energy between the co-adsorbate and the two substrates, SiOx and Cu, was considered. The co-adsorbates with 10kcal/mol or more differences of binding energy with SiOx and Cu were selected and conducted in our experiments. The study includes the observation of film growth as condition modification which includes the modifications of the substrate temperature, partial pressure ratio of co-adsorbate and precursor, and residence time of precursor and co-adsorbate exposed to each other before reaching the substrates. The experiment results are analyzed by X-ray photoelectron spectroscopy (XPS) and reported in original spectra and integrated intensity.