Strained Metal Nitride Films via Dual Precursor Reactivity
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Solution Overview
Problem
Current semiconductor technologies face challenges in forming strained metal nitride films that are compatible with existing ULSI integration techniques, particularly in maintaining strain in CMOS transistor channels due to the introduction of metal gate stacks, which reduce the strain imparted in the channel region.
Innovation Solution
A method is developed to form strained metal nitride films by utilizing a difference in reactivity of nitrogen precursors with metal precursors, creating a density gradient across the film thickness to induce tensile or compressive strain, employing techniques like atomic layer deposition, plasma-enhanced chemical vapor deposition, and varying the ratio and plasma power of nitrogen precursors during the deposition process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal gate stacks are introduced to improve device performance, then transistor performance is improved, but the strain imparted in the channel region is reduced
Solution Approach 1:
A strained metal nitride film is introduced as an intermediary layer between the metal gate stack and the channel region. This intermediary film provides additional strain to the channel, compensating for the strain reduction caused by the metal gate stack's higher modulus. The film acts as a mediator that transfers strain from the gate structure to the channel through controlled density gradients.
Solution Approach 2:
The invention changes the physical and chemical parameters of the nitride film by controlling the reactivity ratios of different nitrogen precursors during deposition. By varying precursor reactivity, the film's density gradient is controlled, which directly adjusts the strain magnitude and distribution in the channel region, allowing optimization of both performance and strain.
2Reliability
If highly tensile strained silicon nitride films are deposited to increase channel carrier mobility, then carrier mobility is improved, but compatibility with existing fabrication processes becomes difficult
Solution Approach 1:
The invention modifies deposition parameters by using different nitrogen precursors with varying reactivity characteristics. This allows precise control over the nitride film's density and strain properties while maintaining compatibility with standard semiconductor fabrication processes such as atomic layer deposition and plasma-enhanced chemical vapor deposition.
Solution Approach 2:
The strained metal nitride film functions as a composite material system where metal and nitrogen elements are combined in controlled stoichiometric ratios. This composite structure enables simultaneous achievement of high strain, desired mobility enhancement, and process compatibility through adjustable composition and density distribution.
3Stress or pressure
If stressed films are placed within the gate stack to increase imparted strain, then strain proximity to channel is improved, but film density and thickness uniformity become harder to control
Solution Approach 1:
The nitride film is segmented into regions with different density characteristics through controlled precursor reactivity during deposition. The film contains a density gradient that transitions from lower density near the channel interface to higher density toward the gate electrode, allowing strain to be concentrated where needed while maintaining overall film uniformity and controllability.
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
This method allows for better control of strain and thickness uniformity in metal nitride films, enhancing channel carrier mobility in transistors and improving integration with existing fabrication processes, thereby improving transistor performance.
Implementation Method 1
Nitride films can be deposited at low pressure or at atmospheric pressure using a variety of processing systems and process gases
Implementation Method 2
employing techniques like atomic layer deposition, plasma-enhanced chemical vapor deposition
Data Source
AI summary
A method for forming a strained metal nitride film and a semiconductor device containing the strained metal nitride film. The method includes exposing a substrate to a gas containing a metal precursor, exposing the substrate to a gas containing a first nitrogen precursor configured to react with the metal precursor with a first reactivity characteristic, and exposing the substrate to a gas pulse containing a second nitrogen precursor configured to react with the metal precursor with a second reactivity characteristic different than the first reactivity characteristic such that a property of the metal nitride film formed on the substrate changes to provide a strained metal nitride film.