Offset MOL Contacts Prevent Gate Shorts
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Solution Overview
Problem
As semiconductor processes scale down, it becomes increasingly difficult to fabricate middle of line (MOL) metallization features due to critical dimension scaling and process limitations, leading to shorts between gate and source/drain contacts.
Innovation Solution
The structure and method involve forming gate and source/drain contacts offset from each other and at different heights, using a sacrificial layer and dielectric cap in the interlevel dielectric layer to prevent shorts during fabrication, allowing for simultaneous formation of metallization features on both gate and source/drain regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional etching processes are used to remove dielectric material adjacent to gate structures, then source and drain contact openings can be formed, but the low-k dielectric spacer material is eroded away exposing the gate metal, resulting in shorts between gate and contact metals
Solution Approach 1:
A liner layer is deposited over the gate structure before the etching process to protect the gate metal from exposure. The liner is applied in advance to prevent the erosion of spacer material from causing shorts during subsequent etching operations.
Solution Approach 2:
The liner layer acts as an intermediary protective barrier between the etching process and the gate metal structure. This intermediate layer prevents direct contact between the eroding dielectric material and the gate metal, thereby preventing shorts.
2Length of moving object
If minimum spacing between gate structures is reduced to achieve smaller technology nodes, then device scaling is enabled, but design rules become difficult to achieve and shorts occur between gate contacts and source/drain contacts
Solution Approach 1:
The contacts are formed at different heights (vertical dimension) rather than maintaining horizontal spacing alone. Gate contacts and source/drain contacts are offset vertically, allowing minimum horizontal spacing to be reduced while preventing shorts through vertical separation.
Solution Approach 2:
Gate contacts and source/drain contacts are positioned asymmetrically at different heights rather than symmetrically at the same level. This asymmetric vertical offsetting allows for reduced pitch while maintaining electrical isolation between different contact types.
3Length of moving object
If pitch between features is reduced for scaling, then smaller technology nodes are achieved, but it becomes difficult to fabricate metallization features due to process capabilities and material limitations
Solution Approach 1:
The liner layer is deposited in advance before metallization feature formation to protect underlying structures during subsequent fabrication processes. This preliminary protective action enables processing at smaller pitches without compromising structure integrity.
Solution Approach 2:
The liner layer serves as a disposable protective element that can be deposited and removed without significant cost or complexity. This temporary protective structure enables fabrication at reduced pitches by preventing damage during processing, then is discarded after serving its protective function.
Data Source
AI summary
The present disclosure generally relates to semiconductor structures and, more particularly, to middle of line structures and methods of manufacture. The structure includes: a plurality of gate structures comprising source and drain regions; contacts connecting to the source and drain regions; contacts connecting to the gate structures which are offset from the contacts connecting to the source and drain regions; and interconnect structures in electrical contact with the contacts of the gate structures and the contacts of the source and drain regions.