Metal Silicide Contact Plug Formation on Silicided Source Drain Regions
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Solution Overview
Problem
In semiconductor devices, the varying impurity concentrations of impurity diffusion regions lead to uneven thermal oxidation film growth, causing issues with etching, which can result in increased leak current and electrical shorts due to the acceleration of oxidation, particularly affecting the formation of metal silicide layers and device isolation insulating films.
Innovation Solution
A method is developed to form a semiconductor device with specific impurity diffusion regions and a thermal oxidation film, where a partial region of the impurity diffusion region has the thermal oxidation film removed, allowing for the formation of a metal silicide layer and conductive plug connection, while avoiding unnecessary etching of device isolation insulating films by using resist patterns and selective etching techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the etching time is adjusted for the thickly formed thermal oxidation film in high impurity concentration regions, then the thermal oxidation film can be removed, but the device isolation insulating films are also etched in portions where the thermal oxidation film is formed thinly, causing increased leak current
Solution Approach 1:
The patent divides the thermal oxidation film removal process into two distinct stages: first removing the thick thermal oxidation film from high impurity concentration regions, then removing the thermal oxidation film from low impurity concentration regions. This segmentation allows each etching step to be optimized for its specific target without affecting other regions, thereby preventing leak current issues while ensuring complete thermal oxidation film removal.
Solution Approach 2:
The patent performs preliminary removal of the thick thermal oxidation film from high impurity concentration regions before addressing the thin thermal oxidation film in low impurity concentration regions. This preliminary action prevents the need for prolonged etching that would otherwise be required to remove the thick film, thereby protecting the device isolation insulating films from being etched during the process.
2Reliability
If a thermal oxidation film is covered by a silicon nitride film to prevent accelerating oxidation, then the thermal oxidation film under the silicon nitride film is protected, but the process complexity increases
Solution Approach 1:
The patent applies a preliminary thermal oxidation treatment to form a preliminary thermal oxidation film before forming the main thermal oxidation film. This preliminary film serves as a protective layer that prevents accelerating oxidation during subsequent processing steps, eliminating the need for additional silicon nitride film layers while maintaining the same protective function.
Solution Approach 2:
The patent changes the oxidation parameters (temperature, time, atmosphere) to create a preliminary thermal oxidation film with specific properties that provide oxidation resistance. By adjusting these parameters, the patent achieves the same protective effect as silicon nitride films but using only thermal oxidation processes, thereby simplifying the overall film structure.
3Ease of manufacture
If the thermal oxidation film is removed completely from impurity diffusion regions, then metal silicide layer formation is enabled, but the device isolation insulating films may be damaged
Solution Approach 1:
The patent segments the thermal oxidation film removal process into region-specific steps: first removing the thick thermal oxidation film from high impurity concentration regions where metal silicide formation is needed, then separately removing the thin thermal oxidation film from low impurity concentration regions. This segmentation ensures that metal silicide layers can be formed where required while preserving the integrity of device isolation films in other areas.
Solution Approach 2:
The patent applies different etching conditions and durations to different regions of the substrate based on their local requirements. High impurity concentration regions receive aggressive etching to enable metal silicide formation, while low impurity concentration regions receive milder treatment to protect device isolation films. This local quality approach allows optimized processing for each region's specific needs.
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 contact resistance and prevents electrical shorts by ensuring the metal silicide layer is formed only where necessary, maintaining the integrity of device isolation films and improving the semiconductor device's operational characteristics.
Implementation Method 1
a thermal oxidation film is formed on the impurity diffusion region as a gate insulating film
Implementation Method 2
The thermal oxidation film is needed to be removed by etching before a metal silicide layer is formed
Implementation Method 3
a metal silicide layer is formed in the surface layer of the impurity diffusion region
Data Source
AI summary
A method for manufacturing a semiconductor device includes the steps of forming a flash memory cell provided with a floating gate, an intermediate insulating film, and a control gate, forming first and second impurity diffusion regions, thermally oxidizing surfaces of a silicon substrate and the floating gate, etching a tunnel insulating film in a partial region through a window of a resist pattern; forming a metal silicide layer on the first impurity diffusion region in the partial region, forming an interlayer insulating film covering the flash memory cell, and forming, in a first hole of the interlayer insulating film, a conductive plug connected to the metal silicide layer.