Backside Contact Structure Using a Wide Placeholder Profile
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Solution Overview
Problem
In semiconductor devices with backside contact structures, the removal of the substrate during manufacturing can lead to the loss of source/drain regions due to the use of wet etchants, which also attack the silicon-based source/drain regions, resulting in performance deterioration.
Innovation Solution
The implementation of a placeholder structure with a wide profile in the backside isolation structure prevents the loss of source/drain regions by ensuring the wet etchant does not affect them during substrate removal, and the backside contact structure with a wider upper portion provides improved connection performance with reduced contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional backside contact structure is formed without a wide placeholder structure, then the manufacturing process is simpler, but the source/drain region is lost due to wet etchant attack during substrate removal
Solution Approach 1:
A placeholder structure is formed in advance at the target location where the backside contact structure will eventually be formed. This placeholder structure has a wide profile that extends beyond the source/drain region boundaries. The placeholder structure serves as a protective barrier during substrate removal, preventing wet etchant from attacking the source/drain region. After substrate removal, the placeholder structure is replaced with the actual backside contact structure, which has a narrower profile matching the source/drain region dimensions.
Solution Approach 2:
The placeholder structure acts as an intermediary element that temporarily occupies the space where the backside contact structure will be formed. It mediates between the substrate removal process and the final contact structure formation, protecting the source/drain region during the critical substrate removal step while enabling the subsequent formation of a properly-sized contact structure.
2Reliability
If a narrow backside contact structure is formed matching the source/drain region width, then the contact resistance is lower, but the source/drain region is damaged by wet etchant during substrate removal
Solution Approach 1:
The placeholder structure is formed in advance with a wide profile that provides etchant protection. This preliminary structure enables the substrate removal to proceed safely without damaging the source/drain region. The placeholder is subsequently replaced with a precisely-sized backside contact structure that matches the source/drain region dimensions, achieving both protection and precision.
Solution Approach 2:
The placeholder structure serves as an intermediary that temporarily provides the wide profile needed for protection, while allowing the final contact structure to achieve the precise narrow dimensions required for low contact resistance. The intermediary placeholder enables a two-stage process that achieves both protection and precision.
3Reliability
If a wide backside contact structure is formed to prevent etchant attack, then the source/drain region is protected, but the contact resistance increases
Solution Approach 1:
The placeholder structure is formed in advance with a wide profile for protection, but it is subsequently replaced with a backside contact structure of precise dimensions. This two-stage approach allows the temporary wide structure to provide protection during substrate removal, while the final narrow structure provides low contact resistance.
Solution Approach 2:
The wide placeholder structure is discarded after serving its protective function during substrate removal. It is then recovered or replaced with a narrow backside contact structure that provides the desired low contact resistance. The temporary wide structure is sacrificed to enable the formation of the optimal narrow contact structure.
4Productivity
If substrate removal is performed without a protective placeholder structure, then the manufacturing process is faster, but the source/drain region is lost
Solution Approach 1:
The placeholder structure is formed in advance to provide immediate protection during substrate removal. This preliminary protective measure enables the substrate removal process to proceed at full speed using aggressive wet etchants, while the placeholder structure prevents source/drain region loss. The placeholder acts as a pre-positioned shield that does not slow down the etching process.
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 maintains the integrity of the source/drain regions and enhances the connection performance by preventing etchant attack, thereby improving the overall performance of the semiconductor device.
Implementation Method 1
the removal of the substrate during manufacturing can lead to the loss of source/drain regions due to the use of wet etchants, which also attack the silicon-based source/drain regions
Data Source
AI summary
Provided is a semiconductor device including a backside contact structure formed based on a placeholder structure having a wide profile, an a method of manufacturing the same. The method may include: forming a source/drain region; and forming a backside contact structure on a bottom surface of the source/drain region such that a width of an upper portion of the backside contact structure is greater than a width of the source/drain region in a channel-length direction.