Area Selective Deposition
Moving to bottom up patterning with self-limiting functionalization for ultra-thin devices.
Reasons for Area Selective Deposition
Smaller Line Width
EUV technology is not widely available. Multiple patterning schemes cannot handle the large number of steps. Bottom up fabrication with area selective deposition offers greater precision. This can greatly reduce the number of fabrication steps required by advanced lithography methods. Success depends on chemistry that will not react with protecting groups on adjacent surfaces or cause contamination in non-targeted areas.
More Device Layers
Nanoscale devices have many complex structures (e.g., 3D or High Aspect Ratio) deposited at the atomic level. Layers must be extremely thin, uniform, and defect free. Many more layers are required to make devices perform to specifications. Deposition processes must be fast to be cost effective.
Key Challenges for Area Selective Deposition
Highly Selective Chemistries
ASD requires new reactive precursors that enable better surface specificity. Oxidants must deposit materials on metal surfaces uniformly without reacting with adjacent protected surfaces.
Temperature and Reactivity
Current technologies operate at higher temperatures or use highly reactive non-compatible oxidants that do not adequately form to the surface. New oxidants are required to deposit high quality oxide films at low temperature and not cause sub-surface oxidation. Thermal ALD is preferred because it leads to conformal deposition on 3D surfaces.
Interfacial Defects Caused by Island Growth
ASD requires fast nucleation and initiation of film growth with minimal cycle delay. Water can require up to 7 cycles to deposit the equivalent of one monolayer. This leads to non-uniform growth and interfacial defects. Microdroplets are common, staining the wafer surface and increasing island growth.
Solving ASD Challenges
Highly Selective Chemistries
Anhydrous hydrogen peroxide gas creates Hydroxyl groups that react rapidly with select surfaces while leaving protecting groups unaffected. Hydrogen peroxide will not remove photoresist materials, leaving protected structures untouched.
Fast, Dense Nucleation
Hydrogen peroxide readily breaks into OH groups that efficiently attach to deposition surfaces. Nucleation density is improved 5x on SiGe and over 3x on germanium versus water. This leads to shorter ALD incubation periods and few interfacial defects on the resulting oxide films.
Anhydrous hydrogen peroxide gas has been shown to deposit films high quality dielectric properties, equivalent to ozone, and without the detrimental effects of ozone.
Anhydrous hydrogen peroxide (HOOH) readily splits into OH radicals, which results in a high concentration of -OH groups on the surface, creating a large diffusion barrier. It is difficult for additional HOOH to penetrate this barrier. HOOH ensures a self-limiting reaction. In contrast HOH (water) splits into -H and -OH groups, which results in a low concentration of –OH groups on the surface, creating a poor diffusion barrier.
More Uniform Nucleation without Sub-Surface Oxidation
Hydrogen peroxide readily splits into O-H groups due to its high reactivity and can achieve higher nucleation density. On a germanium surface, over 3x OH nucleation concentration is achieved. without the presence of water, hydrogen peroxide reacts with the surface and does not oxidize the sub-surface.
Steric Hindrance of Hydrogen Peroxide versus Water
Water splits into H and OH groups and leads to poor nucleation. Unlike water, hydrogen peroxide will not penetrate beneath the surface and cause sub-surface oxidation. In addition, hydrogen peroxide has nucleated more densely than water as it does not suffer from steric hindrance.
Hydrogen peroxide is non-reactive with photoresists up to 350°C. This allows for high quality oxide deposition without damaging the subsurface or protected structures.
Learn About BRUTE Peroxide
Introducing BRUTE® Peroxide
Brute Peroxide utilizes a proprietary vapor-delivery vessel to provide virtually water-free hydrogen peroxide (H2O2) gas for customer processes. The solution is pre-loaded at RASIRC, combining hydrogen peroxide liquid with a proprietary solvent, which ensures that the liquid source remains below 30% by weight hydrogen peroxide.
BRUTE Peroxide Gas from Innovative Design
BRUTE Peroxide includes a vaporizer preloaded with a proprietary non-volatile solvent that ensures safety. The hydrogen peroxide liquid concentration is kept below 30% by weight. Hydrogen peroxide diffuses across a proprietary membrane assembly, leaving the solvent behind. Once across the membrane, hydrogen peroxide is swept to process by a carrier gas or diffuses via vacuum conditions. Hydrogen peroxide vapor pressure is 0.5 Torr at room temperature. BRUTE Peroxide generates ultra-dry hydrogen peroxide gas and can be used with or without a carrier gas.
See Latest Research on Oxides.
BRUTE Peroxide Datasheet
PUBLISHED IN 2017
RASIRC BRUTE Peroxide provides a breakthrough method to deliver virtually water-free hydrogen peroxide (H2O2) gas into Atomic Layer Deposition (ALD) and Etch (ALE) processes. BRUTE Peroxide solution is preloaded in a RASIRC vaporizer. This solution combines hydrogen peroxide liquid and a proprietary solvent, which ensures that the liquid source remains below 30% by weight hydrogen peroxide.
Anhydrous Hydrogen Peroxide Gas Delivery for Atomic Layer Deposition
PUBLISHED IN 2016
In order to minimize defects, enhance uniformity and increase device performance, researchers have begun to focus on the interface between dielectric materials and Si, SiGe, Ge and InGaAs. Most defects, which lead to charge traps and decreased mobility, are believed to occur in this interfacial region. While cartoons of ALD show nice monolayer continuous growth, ALD growth usually occurs in islands on the surface with 3 cycles typically needed for each monolayer. More surprising is that initiation of ALD growth on the surface is far from ideal. Initial film growth of the first monolayer may take up to 6-7 cycles. Research suggests that significant device improvements can be made if the surface is functionalized with a dense layer of hydroxyl groups –OH, prior to deposition.
RASIRC to Present Anhydrous Hydrogen Peroxide Surface Preparation and Enhanced Nucleation for ASD at ASD2018
PUBLISHED ON APRIL 24, 2018
Area selective deposition is becoming increasingly important for the immense scaling effort continuously taking place in the semiconductor industry for Logic and Memory Devices. Today double and multiple pattering schemes using Plasma Enhanced ALD are in High Volume Manufacturing (HVM) for all sub 28 nm nodes and any moment now the industry expect to ramp EUV lithography, possibly at the 7 nm Foundry Node. Beyond that in a joint effort the researchers and the industry are looking for alternative patterning methods and many of them are based on so called bottom-up patterning.
RASIRC products generate and deliver water vapor, hydrogen peroxide and hydrazine gas in controlled, repeatable concentrations to critical processes.
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