Semiconductor Contact Structures Using Sacrificial Etch Caps
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Solution Overview
Problem
As semiconductor processes scale down, it becomes challenging to fabricate features with smaller pitch and critical dimensions due to the need for tall self-aligned contact gate caps, which are not viable in advanced technology nodes like 7 nm and beyond.
Innovation Solution
The implementation of a structure with over-etched sidewall spacers, source and drain regions, and a sacrificial cap with etch selectivity different from surrounding materials, allowing for the formation of metallization features without shorting, even during over-etching, using a method that includes forming T-shaped α-Si caps and depositing dielectric and metal materials within trenches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tall self-aligned contact gate cap is used to prevent shorting during etching, then the reliability of contact formation is improved, but the device complexity and manufacturing difficulty increase as technology nodes scale down
Solution Approach 1:
A sacrificial cap layer is introduced as an intermediary material between the gate structure and the contact formation process. This sacrificial cap has etch selectivity different from the sidewall spacer, allowing it to be removed selectively after serving its protective function during etching, thereby preventing shorting without requiring a permanently tall gate cap structure
Solution Approach 2:
The etch selectivity parameter is changed by using a sacrificial cap material with different etch characteristics compared to the sidewall spacer. This allows the etching process to selectively remove the sacrificial cap while preserving the sidewall spacer, enabling precise control over the contact formation geometry without increasing overall structure height
2Productivity
If the pitch between features is reduced to achieve smaller technology nodes, then the productivity and integration density are improved, but the manufacturing precision required increases significantly
Solution Approach 1:
The etching process is segmented into multiple selective steps: first etching through the sacrificial cap with different etch selectivity, then removing the sacrificial cap material. This segmentation allows each step to be optimized independently, achieving the required precision for small pitch features while maintaining productivity
Solution Approach 2:
The sacrificial cap acts as a temporary intermediary structure that enables precise contact alignment at reduced pitch. By providing a distinct etch target that can be selectively removed, it facilitates the formation of accurately positioned contacts without requiring the sidewall spacer to be excessively tall or complex
3Ease of manufacture
If over-etching is performed to ensure complete trench formation, then the manufacturing robustness is improved, but the risk of shorting between gate and source/drain regions increases
Solution Approach 1:
The sacrificial cap serves as a protective intermediary layer that remains in place during the etching process, allowing robust over-etching to ensure complete trench formation. After etching, the sacrificial cap is selectively removed, revealing the properly formed contact that does not short to the gate, thus combining manufacturing robustness with electrical isolation
Solution Approach 2:
The sacrificial cap provides beforehand cushioning protection during the etching process. It cushions the underlying structures from direct exposure to the etch plasma, allowing the etch to proceed aggressively and completely without risking damage or shorting. The sacrificial cap is then removed after it has served its protective purpose
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
Enables the fabrication of semiconductor structures in advanced technology nodes by preventing shorting and allowing for precise control of etching, ensuring reliable connections between gate and source/drain regions without compromising the integrity of the gate structures.
Implementation Method 1
depositing a sacrificial layer over the gate structures having an etch selectivity different than the sidewall spacers
Implementation Method 2
depositing a metal material within the trench to form a source and drain contact
Data Source
AI summary
The present disclosure generally relates to semiconductor structures and, more particularly, to contact structures and methods of manufacture. The structure includes: a plurality of gate structures comprising source and drain regions and sidewall spacers; contacts connecting to at least one gate structure of the plurality of gate structures; and at least one metallization feature connecting to the source and drain regions and extending over the sidewall spacers.