Self-Aligned Contact Work Function Material Recessing
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Solution Overview
Problem
In modern integrated circuits, the formation of self-aligned contacts results in undesirable loss of protective gate cap layers and sidewall spacers during the contact etching process, leading to potential contact-to-gate shorts and defective devices due to variations in gate electrode height and spacer thickness.
Innovation Solution
The method involves forming gate cavities with a work function material layer, recessing this layer selectively to define cap recesses, and forming a cap layer within these recesses to maintain spacer thickness and prevent contact-to-gate shorts, using techniques like replacement gate processing and selective etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional masking and etching techniques are used to form contact openings, then alignment can be established, but the physical space between adjacent gate structures is insufficient for accurate positioning
Solution Approach 1:
The gate cap layer and sidewall spacers serve as self-aligned etch masks that automatically define the contact opening positions. The etch process uses these structures themselves as the alignment reference, eliminating the need for separate masking steps and achieving precise alignment in high-density configurations where traditional masking would fail.
Solution Approach 2:
The gate cap layer and sidewall spacers are formed in advance before the contact opening etch process. These protective structures are prepared beforehand to serve as etch masks, ensuring that the contact openings are precisely positioned relative to the gate structures before the actual contact formation begins.
2Productivity
If contact etching is performed to form self-aligned contacts, then contact openings are created, but the gate cap layer and sidewall spacers are eroded leading to potential shorts
Solution Approach 1:
The gate cap layer is formed as a protective cushion structure before the contact etch process. This additional layer provides a safety margin that prevents the etch process from reaching and eroding the critical sidewall spacers and gate electrode, thereby preventing contact-to-gate shorts while still enabling efficient contact formation.
Solution Approach 2:
The gate cap layer serves as a preliminary protective barrier that counteracts the harmful erosion effect of the contact etch process. By placing this protective layer beforehand, the patent prevents the adverse effect of spacer thinning and gate electrode exposure that would otherwise occur during contact formation.
3Ease of manufacture
If the contact etch process is performed to remove dielectric material, then contact openings are formed, but portions of the protective gate cap layer and sidewall spacers are consumed
Solution Approach 1:
The gate cap layer is deposited as an additional protective cushion before the contact etch process. This preliminary protective layer absorbs the material loss during etching, preventing the consumption of the critical sidewall spacers and gate electrode materials, thereby maintaining structural integrity while enabling easy contact opening formation.
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 likelihood of contact-to-gate shorts and maintains the integrity of gate structures, even with variations in gate electrode height and spacer thickness, enhancing the reliability of self-aligned contact formation in semiconductor devices.
Implementation Method 1
The work function material layer is recessed selectively to the first and second conductive materials to define a plurality of cap recesses
Data Source
AI summary
One method disclosed includes, among other things, forming a first plurality of gate cavities in a first dielectric layer. A work function material layer is formed in the first plurality of gate cavities. A first conductive material is formed in at least a subset of the first plurality of gate cavities above the work function material layer to define a first plurality of gate structures. A first contact recess is formed in the first dielectric layer between two of the first plurality of gate structures. A second conductive material is formed in the first contact recess. The work function material layer is recessed selectively to the first and second conductive materials to define a plurality of cap recesses. A cap layer is formed in the plurality of cap recesses.