Silicon Nitride Film Hydrogen Removal via Segmented LPCVD
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor devices, particularly DRAM, the desorption of hydrogen atoms from silicon nitride films leads to increased leakage current and reduced information retention and reliability due to the presence of Si—H bonds.
Innovation Solution
A method involving low-pressure chemical vapor deposition to form a silicon nitride film with a predetermined thickness, followed by exposure to nitrogen under decompressed conditions, reducing the number of Si—H bonds and hydrogen density to less than 1 atom %.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon nitride film is formed by conventional CVD method, then the film formation process is simple and fast, but hydrogen atoms are contained in the film causing increased leakage current and reduced reliability
Solution Approach 1:
The silicon nitride film formation process is segmented into multiple thin layers (first through fourth silicon nitride layers) with alternating deposition and nitrogen exposure steps. This segmentation allows each thin layer to be treated differently, enabling hydrogen removal through nitrogen exposure while maintaining film integrity, ultimately reducing leakage current despite increased process complexity
Solution Approach 2:
Nitrogen exposure is performed preliminarily between each silicon nitride layer deposition step. This preliminary nitrogen exposure removes hydrogen atoms from the previously deposited layer before the next layer is formed, preventing hydrogen accumulation and reducing leakage current in the final multi-layer structure
2Reliability
If a thick silicon nitride film is formed to ensure coverage, then gate insulating film coverage is improved, but hydrogen content increases leading to higher leakage current
Solution Approach 1:
Instead of forming one thick silicon nitride film, the process segments the total film thickness into four thinner layers. Each thin layer contains less hydrogen, and the alternating nitrogen exposure steps remove hydrogen between layers, achieving both adequate coverage and reduced total hydrogen content
Solution Approach 2:
The film formation parameters are changed from conventional single-step CVD to multi-step LPCVD with controlled layer thickness and alternating nitrogen exposure. This parameter change reduces hydrogen incorporation in each layer while maintaining total film coverage, thereby reducing leakage current
3Reliability
If conventional CVD method is used for silicon nitride film formation, then production efficiency is maintained, but information retention and DRAM reliability decrease due to hydrogen desorption
Solution Approach 1:
The film formation is segmented into four deposition steps with three nitrogen exposure steps in between. While this increases process steps, each step is relatively quick, and the nitrogen exposure eliminates costly rework due to leakage failures, ultimately improving information retention while maintaining acceptable productivity
Solution Approach 2:
The process converts the harmful effect of hydrogen-containing silicon nitride films into a benefit by intentionally forming hydrogen-containing layers and then systematically removing hydrogen through nitrogen exposure. This converts what was previously a harmful byproduct into a controlled intermediate state that is subsequently eliminated, improving reliability
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 approach effectively reduces leakage current and threshold voltage variations, enhancing the retention of information and reliability in DRAM devices by minimizing Si—H bonds and hydrogen density in the silicon nitride film.
Implementation Method 1
a step of forming a silicon nitride layer of a predetermined thickness by the low-pressure chemical vapor deposition method on a portion that covers at least the gate insulating film and the side portions of the gate electrode
Implementation Method 2
a step of exposing the silicon nitride layer to nitrogen under a decompressed atmosphere
Data Source
AI summary
A method of manufacturing a semiconductor device of the present invention is a method of manufacturing a semiconductor device that is provided with a step of successively forming a gate insulating film and a gate electrode on a semiconductor substrate and a step of forming a silicon nitride film that covers at least the gate insulating film and the side portions of the gate electrode, in which the silicon nitride film is formed by laminating a plurality of silicon nitride layers by repeating a step of forming a silicon nitride layer of a predetermined thickness by the low-pressure chemical vapor deposition method and a step of exposing the silicon nitride layer to nitrogen.