Aluminum Replacement Gate Oxidation for Contact Isolation
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Solution Overview
Problem
As semiconductor devices shrink, the formation of contact structures to source and drain regions becomes challenging due to increased likelihood of electrical shorting to gate conductors, affecting product yield and reliability.
Innovation Solution
A semiconductor structure is developed with an aluminum-containing material for replacement gate electrodes, where a contact-level dielectric layer is formed, and physically exposed portions of the aluminum-containing material are oxidized to create dielectric aluminum compound portions, which electrically isolate the contact via structures from the gate electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contact structures are formed to source and drain regions, then electrical contact to active regions is provided, but electrical shorting to gate electrode may occur
Solution Approach 1:
A dielectric spacer is introduced as an intermediary component between the contact structure and the gate electrode. The spacer is formed by depositing dielectric material conformally over the gate electrode and performing anisotropic etching to create a vertical wall structure. This dielectric barrier physically separates the contact from the gate, preventing electrical shorting while allowing the contact to reach the source/drain regions.
Solution Approach 2:
The dielectric spacer is formed in advance before the contact structure is created. By performing the spacer formation process (dielectric deposition and anisotropic etching) prior to contact opening and filling, the protective barrier is already in place to prevent potential shorting during subsequent processing steps and final device operation.
2Length of moving object
If lateral dimension of dielectric spacer is reduced with device scaling, then contact structures can be formed, but likelihood of electrical shorting increases
Solution Approach 1:
The methodology changes the critical parameter from the horizontal width of the dielectric spacer to its vertical height. By making the spacer height the dominant dimension for electrical isolation rather than relying on narrow lateral dimensions, the process maintains reliable electrical separation even as device features are scaled down to smaller dimensions.
Solution Approach 2:
The solution transitions from relying on two-dimensional lateral separation (width of spacer) to three-dimensional vertical separation (height of spacer). The anisotropic etching process creates a vertical wall structure where the height dimension provides the electrical isolation barrier, allowing the horizontal footprint to be minimized for scaling while maintaining isolation reliability.
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 solution effectively prevents electrical shorting between source/drain regions and gate conductors, enhancing the reliability and yield of semiconductor devices by forming borderless contact structures.
Implementation Method 1
Any physically exposed portions of the aluminum-containing material within the replacement gate electrodes are oxidized to form dielectric aluminum compound portions
Data Source
AI summary
An aluminum-containing material is employed to form replacement gate electrodes. A contact-level dielectric material layer is formed above a planarization dielectric layer in which the replacement gate electrodes are embedded. At least one contact via cavity is formed through the contact-level dielectric layer. Any portion of the replacement gate electrodes that is physically exposed at a bottom of the at least one contact via cavity is vertically recessed. Physically exposed portions of the aluminum-containing material within the replacement gate electrodes are oxidized to form dielectric aluminum compound portions. Subsequently, each of the at least one active via cavity is further extended to an underlying active region, which can be a source region or a drain region. A contact via structure formed within each of the at least one active via cavity can be electrically isolated from the replacement gate electrodes by the dielectric aluminum compound portions.