Atomic layer deposition of oxide films and planarization of small trenches by superfilling

Atomic layer deposition (ALD) has attracted remarkable attention in recent years as an important technique for thin film deposition. Based on alternating self-limiting surface reactions, ALD can coat substrates with conformal films, control the film thickness precisely, and tune the film composition flexibly. These three characteristics of ALD are utilized in this dissertation to prepare oxide films for specific applications.;Conformal coatings of Al2O3 and ZnO films on carbon nanotube (CNT) forests are studied in Chapter 2. CNT forests are functionalized by NO2 and trimethylaluminum first, and conformally coated by ALD Al2O3 or ZnO films with large exposures. Based on Al-doped-ZnO/Al 2O3/CNT-forest structures, solid state supercapacitors have been fabricated. The performance of the device shows the promising potential for the lightweight energy storage.;Coaxially-gated field emission transistors (FET) can be made from WN/Al 2O3/CNTs with the metal-insulator-semiconductor structure. In order to fabricate FETs on a large scale, the efforts have been made in Chapter 3 to selectively place WN/Al2O3/CNTs onto the desired surface. Two methods are tried: one method is to use the affinity between Au and NH2-terminated surface, and the other method is based on electrostatic attractions from surface charges. The selective placements have been achieved in both methods.;As one of transparent conductive materials, Sb-doped SnO2 films have been prepared by ALD in Chapter 4. Dopant can be easily added into the film during the layerby-layer deposition process and the dopant concentration can be well controlled by adjusting ALD cycle ratios. The lowest resistivity of Sb-doped SnO2 films is ∼2x10-3 O·cm for the thickness range of 15∼30nm.;Due to the conformailty of ALD films the planarization can't be obtained by filling the trenches with ALD films. A new deposition method is developed in Chapter 5 to planarize the small trenches. The planar SiAlO x film is prepared from the condensation of tris(tert-pentoxy) silanol vapor on cold substrates, followed by the reaction with TMA and UV-Ozone curing. The film thickness can be well controlled in the range of 20∼100 nm by adjusting the condensation time. Planarization of 19-nm-deep and 45-nm-wide Si trenches is demonstrated by superfilling with 70 nm SiAlOx film.