Area-Selective Atomic Layer Deposition and Area-Selective Etching for Self-aligned Patterning

Self-aligned thin film patterning has become a critical technique for the manufacturing of advanced semiconductor devices. The great benefit of the self-alignment is to reduce the manufacturing costs and patterning errors in photolithographic patterning, especially at the state-of-the-art technology nodes. Area-selective atomic layer deposition (AS-ALD) is such a self-aligned thin film deposition and patterning process, where reactions between alternately supplied precursor vapors on the substrate surface direct the film growth on the desired substrate areas while no growth occurs on the other areas. Chemical differences between the growth and nongrowth surfaces are utilized to control the film nucleation and growth. The chemical differences either inherently exist on the substrate or are created by surface passivation or activation. Self-assembled monolayers (SAMs), small molecule inhibitors (SMIs) and polymers are commonly used for surface passivation while noble metals are commonly used as seed layers for surface activation. Previously, inherently selective ALD was studied mostly in selective deposition of metal oxides on OH-terminated surfaces (e.g., SiO2 and metal oxides) versus metals or H-terminated Si. Differences in surface groups between growth and nongrowth surfaces were utilized for the selectivity. In our research, inherently selective ALD of different types of film materials, i.e., polyimide, noble metals, and ZnS were studied on a range of technically relevant substrate surfaces from metals (Cu, Co, Ru, Ti) to dielectrics (SiO2, TiO2, Al2O3, ZrO2, HfO2, SiOC). Differences in surface groups, catalytic activities, and Lewis acidities of the substrate surfaces were exploited for the selective deposition. The surface-dependent nucleation and growth in these processes were thoroughly studied on growth and nongrowth surfaces with SEM, EDS, XPS, ellipsometry, TEM, etc. We optimized the selective deposition conditions and successfully demonstrated the selectivity on nanometer-scale patterns. Furthermore, insights into the selectivity mechanism were obtained based on our experimental observations and literature knowledge. Area-selective etching (ASE) of polymers based on catalytic activities of the underlying substrates was also studied. In a polymer ASE process, a polymer layer on a substrate surface consisting of catalytic and noncatalytic material regions is selectively removed from the catalytic regions while on the noncatalytic surfaces the polymer layer remains. Catalytic thermal etching of polymers can take place in O2, H2 or inert atmospheres where the etching reactions are combustion, hydrogenolysis, and thermal cracking, respectively. Finally, a polymer film patterned by ASE was successfully demonstrated as a passivation layer for AS-ALD of Ir. Large feature scale AS-ALD was studied by using Parafilm as a mask layer to protect Si substrates against the growth. AS-ALD was successfully achieved in an Ir ALD process while in Al2O3 and TiO2 processes the growth undesirably occurred also on the parafilm mask. A lift-off process was thereby implemented by removing the parafilm mask together with the unwanted growth to obtain the Al2O3 and TiO2 patterns.