Nickel Silicide Layer Nitridation for Oxidation Suppression
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Solution Overview
Problem
Conventional methods for forming nickel silicide layers in semiconductor devices face challenges in suppressing oxidation and resistivity increase, especially in thin films, which affect transistor characteristics and device performance.
Innovation Solution
A semiconductor device with a nickel silicide layer configured to have a first region with no nitrogen and a second region containing nitrogen, formed through a process involving two-step annealing and selective nitridation to control nitrogen distribution, thereby suppressing oxidation and resistivity increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional single-step annealing is used to form nickel silicide, then the process is simple and fast, but oxidation occurs and resistivity increases
Solution Approach 1:
The single-step annealing process is divided into two distinct steps: a first annealing step at a lower temperature (200-350°C) to form nickel-rich silicide, and a second annealing step at a higher temperature (400-600°C) to complete silicide formation and reduce resistivity. This segmentation allows each step to perform its specific function optimally, preventing oxidation while achieving low resistivity.
Solution Approach 2:
The first annealing step performs preliminary silicide formation under controlled conditions that prevent oxidation. By pre-forming the nickel silicide layer at lower temperature before the second high-temperature annealing step, the process prepares the structure in advance to avoid oxidation issues that would occur with direct high-temperature processing.
2Length of moving object
If thin nickel silicide layer is formed, then device scaling is improved, but oxidation and resistivity increase become more significant
Solution Approach 1:
The two-step annealing process creates different local conditions within the thin nickel silicide layer. The first step creates a nickel-rich region with specific properties, while the second step modifies the deeper regions. This local differentiation allows the thin film to maintain low resistivity throughout its volume while the surface region remains protected from oxidation.
3Manufacturing precision
If high temperature annealing is used, then silicide formation is complete and resistivity is low, but oxidation occurs on the surface
Solution Approach 1:
The annealing process is segmented into two temperature zones applied sequentially. The first low-temperature step (200-350°C) forms the silicide nucleus without causing surface oxidation. The second high-temperature step (400-600°C) then completes the silicide formation and reduces resistivity. This temporal and thermal segmentation allows high-temperature benefits without the harmful oxidation effects.
Solution Approach 2:
The first annealing step performs the preliminary action of forming nickel silicide under protected conditions. By establishing the silicide structure first at lower temperature, the surface is prepared in advance to withstand the subsequent high-temperature treatment without oxidizing, as the silicide formation kinetics are already initiated and protected.
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 configuration effectively suppresses oxidation of the nickel silicide surface and reduces resistivity, improving the characteristics and performance of semiconductor devices, particularly in thin film applications.
Implementation Method 1
a first annealing step, in which the nickel film and the silicon substrate are heated, so that nickel silicide is formed
Implementation Method 2
nickel in the Ni film and silicon in the silicon substrate are reacted, to thereby form a Ni2Si layer
Implementation Method 3
nitrogen is introduced into the nickel silicide in a region ranging from a surface to a predetermined depth
Implementation Method 4
the nickel silicide layer is configured to have a first region provided as being in contact with a silicon surface, and containing substantially no nitrogen, and a second region provided in contact with an upper portion of the first region, and containing nitrogen
Data Source
AI summary
A semiconductor device includes a silicon substrate, and a NiSi layer provided on the silicon substrate aiming to suppress oxidation of the surface of a NiSi layer and the resistivity increase. The NiSi layer includes a bottom NiSi region and a top NiSi region. The bottom NiSi region provided in contact with silicon surface, and containing substantially no nitrogen. The top NiSi region is a nitrided NiSi region provided in contact with the bottom NiSi region, and containing nitrogen. The NiSi layer has a total thickness of 50 nm or below.