Semiconductor Device With Projection-Based Channel Thinning
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Solution Overview
Problem
Existing semiconductor device manufacturing methods struggle to thin the channel formation region without adversely affecting the source and drain regions, leading to increased sheet resistance and contact resistance, and require complex processes or special masks, which increase manufacturing costs and reduce integration density.
Innovation Solution
A method involving the formation of a semiconductor film with a thickness smaller than the projection height on an insulating substrate, followed by selective etching to create an island-shaped film, allowing for the thinning of the channel formation region while maintaining the thickness of the source and drain regions, and the introduction of impurities to form a lightly doped drain region without a sidewall, reducing the number of manufacturing steps and avoiding unnecessary etching of the gate insulating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the whole semiconductor film is thinned to reduce channel formation region thickness, then the subthreshold swing is reduced and switching characteristics are improved, but the source region and drain region are also thinned causing increased sheet resistance and contact resistance
Solution Approach 1:
The patent applies local quality by creating a projection structure at the channel formation region position on the insulating substrate surface. This projection causes the semiconductor film to be raised locally, allowing selective thinning of only the channel formation region while the source and drain regions maintain their original thickness. The different thicknesses in different regions (local quality) enable simultaneous optimization of switching characteristics and electrical properties.
Solution Approach 2:
The patent introduces a vertical dimension (height) by forming a projection on the insulating substrate surface. This dimensional change creates a height difference between the channel formation region and source/drain regions, enabling selective etching and thinning operations. The projection height becomes an additional parameter to control the final thickness distribution of the semiconductor film.
2Productivity
If plasma etching is used to thin the channel formation region, then the etching process is effective, but the upper portion of the semiconductor layer is damaged or made amorphous increasing resistance
Solution Approach 1:
The patent applies preliminary action by forming the projection structure on the insulating substrate before depositing the semiconductor film. This pre-formed projection serves as a template that guides subsequent selective thinning operations. The projection is created in advance to enable precise control of where thinning occurs, preventing damage to regions that should not be thinned.
Solution Approach 2:
The patent uses an insulating film as an intermediary layer between the semiconductor film and the etching process. This insulating film is formed over the semiconductor layer, and selective removal of the insulating film exposes only the channel formation region for thinning. The intermediary insulating film protects the source and drain regions during the thinning process, preventing unwanted damage.
3Manufacturing precision
If a sidewall is formed to create an LDD region, then the LDD structure is achieved, but the manufacturing process becomes more complex with additional steps
Solution Approach 1:
The patent extracts the LDD region formation process from the conventional sidewall-based method. Instead of forming a sidewall structure and then creating the LDD region, the invention directly forms the LDD region by selective ion implantation using the projection structure as a mask. This extraction simplifies the process by removing the sidewall formation step while achieving the same LDD region configuration.
Solution Approach 2:
The patent merges the projection formation function with the LDD region mask function. The projection structure serves dual purposes: it defines the channel formation region boundary and simultaneously acts as the mask for selective ion implantation to create the LDD region. This merging of functions reduces the number of separate manufacturing steps required.
4Manufacturing precision
If a halftone mask is used for selective light exposure to thin the channel formation region, then the selective thinning is achieved, but the process becomes complicated and manufacturing cost increases
Solution Approach 1:
The patent replaces the expensive halftone mask with a simple projection structure formed on the insulating substrate. The projection is a permanent structural feature that serves as a built-in mask, eliminating the need for disposable halftone masks. This substitution with a cheaper, reusable structure simplifies the manufacturing process and reduces costs.
Solution Approach 2:
The projection structure on the insulating substrate serves itself as the masking pattern for selective thinning. Instead of requiring an external halftone mask to define the channel formation region boundaries, the projection's own geometry provides the necessary patterning. This self-service approach eliminates additional masking steps and reduces manufacturing complexity.
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 enables the production of semiconductor devices with improved switching characteristics and reduced power consumption by minimizing subthreshold swing, while simplifying the manufacturing process and reducing costs by eliminating the need for special masks, thus enhancing the reliability and integration density of the semiconductor device.
Implementation Method 1
a second etching step of etching the resist to expose a part of the semiconductor film which covers a top surface of the projection of the substrate, while parts of the semiconductor film which are located over the regions adjacent to both sides of the projection of the substrate, remain covered with the resist
Implementation Method 2
a third etching step of etching the exposed part of the semiconductor film, which covers the top surface of the projection, to thin the exposed part of the semiconductor film
Implementation Method 3
a second ion introduction step of introducing impurities into the portions of the semiconductor film which are over the regions adjacent to both sides of the projection to form a source region and a drain region
Data Source
AI summary
To provide a semiconductor device in which a channel formation region can be thinned without adversely affecting a source region and a drain region through a simple process and a method for manufacturing the semiconductor device. In the method for manufacturing a semiconductor device, a semiconductor film, having a thickness smaller than a height of a projection of a substrate, is formed over a surface of the substrate having the projections; the semiconductor film is etched to have an island shape with a resist used as a mask; the resist is etched to expose a portion of the semiconductor film which covers a top surface of the projection; and the exposed portion of the semiconductor film is etched to be thin, while the adjacent portions of the semiconductor film on both sides of the projection remain covered with the resist.