Nickel Alloy Sputtering Target for Stable NiSi Gate Electrodes
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Solution Overview
Problem
Conventional nickel silicide films used in gate electrode materials face issues such as phase transition to NiSi2, boundary roughness, oxidation, and poor thermal stability, leading to increased resistance and particle generation during sputtering, with inferior plastic workability and uniformity.
Innovation Solution
A nickel alloy sputtering target is developed with 22 to 46 wt% platinum and 5 to 100 wtppm of iridium, palladium, or ruthenium, which inhibits phase change from NiSi to NiSi2, improving thermal stability and reducing particle generation, while maintaining favorable uniformity and plastic workability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional nickel silicide film is used in gate electrode material, then it can form silicide film with less silicon consumption, but it easily undergoes phase transition to NiSi2 causing boundary roughness and high resistance
Solution Approach 1:
The patent uses a composite cap film structure consisting of TiN layer and silicon oxide layer. The TiN layer provides nitrogen source for nitridation while the silicon oxide layer protects against oxidation. This composite structure enables simultaneous achievement of low silicon consumption and high thermal stability by preventing NiSi to NiSi2 phase transition through controlled nitridation.
Solution Approach 2:
The patent controls the nitrogen content in the cap film by adjusting the TiN film thickness (5-50 nm) and oxidation conditions. By changing the nitrogen concentration parameter in the cap film, the nitridation rate is controlled to maintain NiSi phase stability at high temperatures while minimizing silicon consumption during the salicide process.
2Object-affected harmful factors
If TiN cap film is sputtered on Ni film and heat treated to nitride the surface, then oxidation is prevented and irregularity formation is suppressed, but the thin nitride film cannot maintain barrier properties for long period
Solution Approach 1:
The patent applies preliminary nitridation by forming TiN cap film on the Ni film before the salicide process. This preliminary nitrogen incorporation creates a nitrogen-enriched layer that suppresses oxidation and irregularity formation during subsequent high-temperature processing, establishing protective properties in advance.
Solution Approach 2:
The patent creates a composite cap film system where TiN layer (5-50 nm) serves as nitrogen source and is combined with silicon oxide layer. This composite structure provides sustained nitrogen release and oxidation protection throughout the salicide process and subsequent annealing, maintaining barrier properties for the required duration.
3Manufacturing precision
If sputtering is performed under mixed gas atmosphere with nitrogen added, then roughness is reduced and grain size is increased, but cap film formation is still required on Ni
Solution Approach 1:
The patent modifies the sputtering atmosphere by adding nitrogen gas (2.5-10%) to the argon atmosphere during TiN cap film formation. This parameter change enables nitrogen incorporation into the cap film structure, which subsequently provides nitrogen during nitridation to suppress oxidation and control grain growth, achieving better film uniformity.
Solution Approach 2:
The TiN cap film formed under nitrogen-containing atmosphere serves multiple functions: (1) provides nitrogen source for nitridation, (2) protects against oxidation, (3) controls grain size, and (4) reduces surface roughness. This multi-functionality reduces the need for separate process steps while achieving multiple objectives.
4Reliability
If nickel alloy target with platinum and secondary metals is used, then phase change temperature is improved and particle generation is reduced, but target composition control becomes more difficult
Solution Approach 1:
The patent uses a composite alloy composition consisting of nickel (balance), platinum (22-46 wt%), and secondary metals (5-100 wtppm each of Ir, Pd, Ru). This composite material structure leverages platinum for high melting point and phase stability, while trace secondary metals suppress particle generation and improve uniformity. The specific composition ranges are optimized to achieve phase change temperature of 750°C or higher while maintaining manufacturability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The nickel silicide film formed using this target exhibits enhanced thermal stability, reduced particle generation, and improved uniformity, effectively preventing phase change and maintaining low resistance even at high temperatures, making it suitable for gate electrode material production.
Implementation Method 1
a nickel alloy film is formed on a silicon substrate by sputtering a nickel alloy sputtering target
Implementation Method 2
reacting the nickel alloy film and the silicon substrate to form nickel silicide
Data Source
Figure 1
AI summary
Provided are a nickel alloy sputtering target, and a nickel silicide film formed with such a target, enabling the formation of a thermally stable silicide (NiSi) film, scarcely causing the aggregation of films or excessive formation of silicides, having low generation of particles upon forming the sputtered film, having favorable uniformity and superior plastic workability to the target, and which is particularly effective for the manufacture of a gate electrode material (thin film). This nickel alloy sputtering target contains 22 to 46 wt% of platinum and 5 to 100 wtppm of one or more components selected from iridium, palladium, and ruthenium, and remainder is nickel and inevitable impurities.