Transistor Gate Insulating Cap for Source-Drain Contact Isolation
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Solution Overview
Problem
As transistor pitch scaling increases, the separation between source/drain contacts and the gate decreases, leading to the unavoidable creation of unwanted electrical contact, which existing manufacturing techniques cannot prevent.
Innovation Solution
A protective etch stop layer, specifically an electrically insulating cap formed in a self-aligned trench using a wet etchant chemistry with carboxylic acid and a corrosion inhibitor, is introduced to prevent electrical contact between the gate and source/drain contacts, thereby protecting the gate during source/drain contact etch and allowing for larger source/drain contacts with reduced resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pitch scaling continues to increase packing density, then transistor packing density is improved, but unwanted electrical contact between source/drain contact and gate becomes unavoidable
Solution Approach 1:
A sacrificial cap is formed over the gate electrode before source/drain contact formation. This sacrificial cap serves as a preliminary protective structure that prevents unwanted electrical contact during the etching process. The cap is removed after the source/drain contact is formed, having fulfilled its protective function during the critical manufacturing step.
Solution Approach 2:
An etch stop layer is introduced as an intermediary protective layer between the gate electrode and the etchant used to form source/drain contacts. This etch stop layer acts as a mediator that allows the etching process to proceed while protecting the gate electrode from direct exposure to the etchant, thereby preventing unwanted electrical contact.
2Productivity
If separation between source/drain contact and gate is decreased to increase packing density, then transistor density is improved, but manufacturing precision becomes more difficult to maintain
Solution Approach 1:
A sacrificial cap made of removable material is deposited over the gate electrode. This disposable structure is intentionally created, used for protection during etching, and then completely removed after serving its purpose. The sacrificial cap provides temporary protection during manufacturing without affecting the final device structure, enabling precise source/drain contact formation even at reduced separations.
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
The electrically insulating cap effectively prevents unwanted electrical contact, increasing the margin for source/drain contact registration and critical dimension, enabling the formation of larger source/drain contacts with lower resistance and improved manufacturing reliability.
Implementation Method 1
removing a sacrificial cap using a wet etchant chemistry that comprises an aqueous solution comprising a carboxylic acid and a corrosion inhibitor
Implementation Method 2
The electrically insulating cap prevents electrical contact between the gate and the source/drain contact
Data Source
AI summary
A transistor comprises a gate (110) comprising a gate electrode (111) and a gate dielectric (112), an electrically insulating cap (120, 720) over the gate, and a source/drain contact (130) adjacent to the gate. The electrically insulating cap prevents electrical contact between the gate and the source/drain contact. In one embodiment, the electrically insulating cap is formed in a trench (160, 660) that is self-aligned to the gate and that is created by the removal of a sacrificial cap using an aqueous solution comprising a carboxylic acid and a corrosion inhibitor.