Sidewall Spacer Formation for Semiconductor Dopant Profiles
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Solution Overview
Problem
The existing methods for forming semiconductor structures require multiple photolithographic processes to achieve different spacings between source, drain, and gate electrodes in transistors, leading to increased complexity and cost due to the need for multiple masks and precise alignment.
Innovation Solution
A method that reduces the number of photolithographic processes by forming sidewall spacer structures and dopant regions using a single mask for each transistor type, allowing for different dopant profiles with fewer mask formations, thereby simplifying the manufacturing process and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple photolithographic processes are used to form different dopant profiles, then manufacturing precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent segments the material layer into different portions that are selectively etched to form sidewall spacers of different thicknesses adjacent to different transistor features. By using a single mask and selectively removing portions of the material layer, the method achieves different dopant profiles without requiring multiple photolithographic processes. This segmentation approach maintains manufacturing precision while reducing process complexity.
Solution Approach 2:
The patent transitions from a two-dimensional photolithographic approach (multiple masks on the surface) to a three-dimensional approach using sidewall spacers. The material layer is formed and then selectively etched from the sidewalls, creating vertical spacer structures that define horizontal dopant regions. This dimensional transition allows multiple dopant profiles to be created from a single photolithographic step.
2Manufacturing precision
If multiple masks are formed for different transistor elements, then manufacturing precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent merges the function of multiple masks into a single mask by forming a unified material layer that covers all transistor features. Instead of applying separate masks for each transistor element, the method uses one mask and a single photolithographic process to define all dopant regions. The selective etching of the material layer then creates the necessary spacing variations, significantly simplifying the manufacturing process while maintaining precision.
Solution Approach 2:
The material layer and sidewall spacers serve a dual function: they act as both the structural element defining transistor geometry and as the self-aligned mask for subsequent ion implantation. The spacers automatically position the dopant regions at precise distances from gate electrodes without requiring additional masking steps. This self-service approach eliminates the need for multiple photolithographic processes.
3Manufacturing precision
If multiple photolithographic processes are used, then manufacturing precision is improved, but productivity deteriorates
Solution Approach 1:
The patent performs preliminary actions by forming the complete material layer structure and selectively etching sidewall spacers before the ion implantation step. This preliminary structuring is done in advance using a single photolithographic process, so that when ion implantation occurs, the dopant regions are already precisely defined. This eliminates the need for multiple photolithographic steps during the manufacturing sequence, thereby improving throughput while maintaining precision.
Solution Approach 2:
The method maintains continuous useful action by using a single photolithographic process that continuously defines all dopant regions across the wafer in one step. Instead of interrupting production with multiple separate photolithographic steps, the continuous process forms all necessary sidewall spacers and defines all dopant profiles in a unified operation, maximizing manufacturing throughput while preserving precision.
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 allows for the formation of different dopant profiles in transistors with reduced photolithographic steps, lowering the complexity and cost of semiconductor manufacturing while maintaining precise control over transistor characteristics.
Implementation Method 1
At least one etch process adapted to form a sidewall spacer structure adjacent the second feature from a portion of the material layer is performed
Implementation Method 2
An ion implantation process is performed wherein ions are incorporated into portions of the substrate adjacent the second feature and the sidewall spacer structure
Data Source
AI summary
According to an illustrative example, a method of forming a semiconductor structure comprises providing a semiconductor substrate comprising a first feature and a second feature. A material layer is formed over the first feature and the second feature. A mask is formed over the first feature. At least one etch process adapted to form a sidewall spacer structure adjacent the second feature from a portion of the material layer is performed. The mask protects a portion of the material layer over the first feature from being affected by the at least one etch process. An ion implantation process is performed. The mask remains over the first feature during the ion implantation process.