Low Temperature Nitrides
Emerging materials, 3-dimensional structures, and new display technologies impose thermal constraints on deposition methods.
Key Challenges for Device Performance
Device performance and size are limited by material heat tolerance in Middle of the Line (MOL) and Back-End of the Line (BEOL) processes. Improved metal contacts, thinner barrier layers and thinner liners are required to minimize parasitic losses as devices shrink.
New Channel Materials
Current processes for next generation channel materials in logic devices are inadequate. Integration imposes new low temperature constraints for several process steps including TiN electrode, AlN2 heat spreader, GaN, and SiN side wall deposition.
Memory density requirements for future 3-D NAND devices requires large increases in vertical scaling. Temperature limits on SiN deposition will continue to decrease from 550°C.
Solving Device Performance Challenges
Hydrazine gas creates low resistivity TiN, SiN, AlN2, GaN, and InGaN films by growing nitrides at lower temperatures than with ammonia.
Uniform High Aspect Ratio Deposition
Hydrazine gas deposits uniform nitride film on high aspect ratio (HAR) features to create effective sidewall materials. This deposition is effective at temperatures as low as 320°C-350°C.
High Density, Low WER
Hydrazine gas builds high density, low wet-etch-rate (WER) SiN . Operating temperatures can be as low as 450°C-550°C.
Technical Brief: Effective Silicon and Metal Nitride Deposition at Reduced Temperature
Hydrazine Gas as a Nitride Source
Low Temperature, High Aspect Ratio
Hydrazine is an excellent low temperature thermal ALD nitride source. Next generation devices have low thermal budgets and high aspect ratio structures that create new challenges for conformal III-V nitride films. Old solutions cannot meet these new challenges. Nitrogen from ammonia does not yield quality films below 400°C. Plasma delivery does not uniformly coat internal side walls of high aspect ratio structures and causes surface damage.
Advantages of Hydrazine Gas
- Highly reactive, enabling thermal ALD at much less than 400°C
- No line of sight required, providing uniform films on high aspect ratio structures
- No oxygen or carbon, eliminating contamination
- Fewer device defects
- Better electrical performance
BRUTE Hydrazine Gas More Reactive than Ammonia
High Uniformity Low Temperature SiN
Silicon nitride materials are used in many memory and logic device elements including dielectric insulating layers, device layers, liners, spacers, etch hardmasks and etch stops. These various elements must all have high uniformity/conformality on 3D structures, low wet etch rate, and excellent dielectric properties. Emerging device requirements include low temperature deposition, which is not attainable with thermal ammonia processes.
No Substrate Damage
Unlike traditional plasma approaches, hydrazine gas does not damage the substrate surface. Plasma requires a line of site, leading to uniformity problems in HAR structures used in memory applications. Nitrogen created by plasma methods cannot uniformly coat the internal sidewalls. Hydrazine gas enables low resistivity, supporting better electrical characteristics in subsequent layers.
Plasma methods have a tendency to incorporate oxygen into the film. Low temperature ammonia plasma methods lead to incomplete dissociation, leaving residual hydrogen N-H bonds. This leads to very low growth per cycle and poor electrical properties. Raising plasma power can cause physical damage to HAR structures and other very thin films. In contrast, BRUTE Hydrazine has purity levels of less than 1.0ppm in the gas phase.
Higher Growth Rate
Researchers have found higher growth rates, higher density films and improved resistivity for films grown with hydrazine versus ammonia under similar low temperature conditions (Kummel). University of Texas (Dallas) researchers have reported similar effective results for hydrazine in low temperature deposition of silicon nitride.
Thermal ALD of TiN below 400°C with NH3/TiCl4 is problematic as Chlorine content increases and resistivity properties escalate. Use of RASIRC BRUTE® Hydrazine has been shown to yield resistivity far lower that ammonia at 400°C and nearly 5x lower at 300°C (Kummel).
Low Temperature HAR Deposition
Recent studies have shown that RASIRC BRUTE Hydrazine is capable of depositing high quality SiN down to temperatures of 320°C with good uniformity and conformality. Process optimization is underway to achieve density and Wet Etch Rates that approach those of high temperature SiN grown at 630°C with ammonia.
Crystalline Aluminum Nitride Deposition
Achieve crystalline Aluminum Nitride deposition with minimal oxygen contamination.
Processes to grow crystalline heat-spreading layers at low temperatures (≤400C) are of interest for several applications. Potential candidates for heat spreaders include diamond, hexagonal boron nitride (h-BN), aluminum nitride (AlN), and gallium nitride (GaN). AlN and GaN have already been reportedly grown at sufficiently low temperatures for widespread implementation.
See Latest Research on Nitrides.
Low Resistivity Halogen-Free TiN Films Grown with Hydrazine at Low Temperature
RASIRC announced new UCSD research shows that TiN film grown by low temperature ALD can yield resistivity below 220 uΩ-cm with a non-halogenated precursor on a variety of surfaces. Low resistivity is an indicator of high-quality metal film that works well as a barrier layer or conductor.
PUBLISHED JUNE 23, 2022
RASIRC Study Shows Nitride Film Growth at 225°C with Hydrazine
RASIRC research shows that aluminum nitride can be grown thermally at 225°C without detrimental oxygen incorporation. The resulting paper is one of the first published demonstrating this ability, which will be useful for memory and logic devices as well as future semiconductor manufacturing.
PUBLISHED MARCH 15, 2022
China Grants Patent to RASIRC for BRUTE® Hydrazine
China has granted a patent related to the delivery of anhydrous hydrazine gas to process.
PUBLISHED MARCH 3, 2022
RASIRC Survey of Hydrazine (N2H4) in Semiconductor Applications Shows Growing Activity in Thin Films at Low Temperature
Jeffrey Spiegelman and Dan Alvarez
PUBLISHED FEBRUARY 21, 2022
Record Low Resistivity Titanium Nitride Film Fabricated by Thermal ALD – Ultra-dry hydrazine enables growth at low temperature
Authored by researchers from UCSD, Samsung, and RASIRC
PUBLISHED JANUARY 18, 2022
RASIRC products generate and deliver water vapor, hydrogen peroxide and hydrazine gas in controlled, repeatable concentrations to critical processes.
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