Deep Source/Drain Backside Contact With Liner Protection
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Solution Overview
Problem
The integration of the power delivery network (PDN) in the back end of line (BEOL) structure of semiconductor devices has become challenging due to increasing device densities, leading to difficulties in avoiding shorting between backside contacts and gate contacts.
Innovation Solution
The implementation of deep source/drain structures with sidewall liner protection and direct backside contact, which involves forming deep nanosheet trenches, depositing a deep trench liner, and creating a backside contact that physically contacts the exposed bottom end of the source/drain, thereby increasing the interface between the backside source/drain contact and the source/drain epitaxy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If backside power delivery is implemented to improve power delivery network integration, then power delivery capability is improved, but risk of shorting between backside contacts and gate contacts increases
Solution Approach 1:
The patent implements backside power delivery by moving the power delivery network from the front side to the back side of the semiconductor substrate, utilizing the third dimension (depth/substrate thickness) to resolve the spatial conflict between power delivery paths and gate contacts. This dimensional transition allows PDN layers to be formed on the opposite side of the chip, eliminating overlap with front-side gate structures while maintaining effective power delivery to high-density devices.
Solution Approach 2:
The patent introduces deep source/drain structures with divots as intermediary elements that extend from the front side through the substrate to the back side. These deep source/drain regions serve as conductive pathways that connect front-side transistor sources/drains to backside contact pads, enabling controlled electrical connection while the trench liner acts as a protective intermediary barrier preventing direct shorting between backside contacts and gate structures.
2Quantity of substance
If deep source/drain structures are formed to enable backside contact, then interface area is improved, but fabrication complexity increases
Solution Approach 1:
The patent performs preliminary actions by forming the deep source/drain structures and trench liners before final backside contact formation. The deep source/drain regions are epitaxially grown and shaped with divots in advance, and trench liners are deposited and patterned beforehand, creating pre-prepared pathways and protective structures that simplify subsequent backside contact fabrication and reduce overall process complexity.
Solution Approach 2:
The patent segments the source/drain structure into multiple functional regions: the upper source/drain region at the front side, the deep source/drain region extending through the substrate with divots, and the lower source/drain region at the back side. This segmentation allows each region to be optimized independently for its specific function while simplifying the overall fabrication process by breaking down the complex deep structure formation into manageable steps.
3Reliability
If trench liner is deposited to protect source/drain during etching, then source/drain protection is improved, but material usage increases
Solution Approach 1:
The patent applies the trench liner selectively only in regions where protection is needed - specifically lining the deep nanosheet trenches and surrounding the deep source/drain regions. This localized application provides targeted protection during backside etching processes while minimizing unnecessary material deposition in other areas, optimizing the balance between protection effectiveness and material consumption.
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 enhances device performance by increasing the interface between the backside source/drain contact and the source/drain epitaxy, while also omitting the need for placeholders, thus preventing backside contact-to-gate shorting and reducing material and fabrication complexity.
Implementation Method 1
etching a backside of the semiconductor substrate to form a backside contact trench which exposes the deep nanosheet trench while the deep trench liner prevents etching of the source/drain
Implementation Method 2
forming a backside contact in the backside contact trench to establish physical contact between the backside contact and the bottom end of the source/drain
Data Source
AI summary
A semiconductor device includes a first nanosheet stack on a front side of a semiconductor substrate, a second nanosheet stack on the front side of the semiconductor substrate separated from the first nanosheet stack by a source/drain region, and a deep nanosheet trench extends into the source/drain region between first and second nanosheet stacks. A source/drain is in the deep nanosheet trench and includes a bottom end having a backside source/drain divot formed therein. A deep trench liner is interposed between the deep nanosheet trench and the source/drain, the deep trench liner having an opening exposing the bottom end of the source/drain. A backside contact is on a backside of the semiconductor device, the backside contact physically contacting the exposed bottom end of the source/drain.