Self-Aligned Contact Formation Using Oxide Gate Recess
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Solution Overview
Problem
The existing methods for forming self-aligned contacts in semiconductor devices result in undesirable loss of protective gate cap layers and sidewall spacers, leading to increased complexity and difficulty in gate etching and spacer etching processes due to the need for additional thickness to compensate for material consumption during the contact etch process.
Innovation Solution
The proposed method involves forming a layer of insulating material above the source/drain region, performing etching to create a contact opening, selectively applying an oxidizable material to the exposed gate structure, and undergoing an oxidation process to convert the material into an oxide, allowing for the formation of a conductive contact while minimizing the consumption of gate cap layers and sidewall spacers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional self-aligned contact formation is used, then contact alignment is achieved, but gate cap layers and sidewall spacers are consumed during etching
Solution Approach 1:
The patent applies preliminary action by forming a mandrel structure and spacer layers before the contact etch process. These pre-formed structures serve as protective templates that prevent consumption of the gate cap layer and sidewall spacers during subsequent etching operations, thereby preserving material thickness while achieving precise contact alignment.
Solution Approach 2:
The patent introduces intermediary structures (mandrel and spacer layers) that mediate between the contact etch process and the gate cap layer/sidewall spacers. These intermediary elements act as sacrificial or protective barriers that absorb the etching action, preventing direct contact and consumption of the critical gate structures.
2Loss of substance
If additional thickness is added to gate cap layers and sidewall spacers to compensate for consumption, then material loss is compensated, but process complexity increases
Solution Approach 1:
The patent segments the protective function into separate, dedicated structures (mandrel and spacer layers) rather than relying on increased thickness of the gate cap and sidewall spacers. This segmentation allows each layer to perform its specific function without requiring complex thickness adjustments to multiple layers, thereby reducing overall process complexity.
3Loss of substance
If gate cap layer and sidewall spacer thickness is increased, then material consumption is compensated, but aspect ratio of contact openings increases
Solution Approach 1:
The patent transitions from compensating for material loss in the vertical dimension (increasing thickness) to solving the problem in the lateral dimension by introducing mandrel and spacer structures. This dimensional shift allows precise contact formation without increasing the aspect ratio, as the protective function is achieved through lateral structuring rather than vertical thickening.
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 reduces the consumption of protective gate cap layers and sidewall spacers, maintaining their thickness and reducing the aspect ratio of contact openings, thereby simplifying the etching processes and improving the efficiency of contact formation.
Implementation Method 1
performing an oxidation process to convert at least a portion of the oxidizable material to an oxide material
Data Source
AI summary
One method includes performing a first etching process to form a contact opening in a layer of insulating material that exposes a portion of a gate structure of the transistor, performing a second etching process on the exposed portion of the gate structure to thereby define a gate recess, selectively forming an oxidizable material in the gate recess, converting the oxidizable material to an oxide material, and forming a conductive contact in the contact opening that is conductively coupled to a source/drain region. A device includes an oxide material that is positioned at least partially in a recess formed in a gate structure, wherein the oxide material contacts a conductive contact and contacts a portion, but not all, of the exterior surface of the gate structure.