Self-aligned contact scheme using segmented hard masks
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Solution Overview
Problem
As semiconductor devices shrink, conductive features connecting to layers above and below can become shorted due to misalignment during the etching process, leading to unintended exposure of adjacent conductive features.
Innovation Solution
A self-alignment scheme using multiple mask layers, including metal nitride or metal oxide mask layers, is employed to protect conductive features during contact opening etching processes, ensuring that the self-aligned contact does not short gate electrodes to source/drain regions by utilizing an upper hard mask layer made of metal nitride or metal oxide and recessing the lower hard mask layer to remove seams and voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional single mask layer etching is used, then the etching process is simple and fast, but misalignment occurs causing conductive features to short adjacent features
Solution Approach 1:
The patent divides the single mask layer into multiple segmented mask layers (first hard mask layer and second hard mask layer) with different materials and functions. The first mask layer provides etch selectivity for the contact opening, while the second mask layer protects the gate electrode during subsequent etching steps. This segmentation resolves the alignment precision problem by assigning specific protective functions to each layer.
Solution Approach 2:
The patent forms the second hard mask layer over the gate electrode before performing the contact opening etch. This preliminary action ensures that the gate electrode is protected in advance during the etching process, preventing misalignment-related shorts without requiring complex real-time alignment adjustments.
2Manufacturing precision
If multiple mask layers are used to prevent misalignment, then alignment precision improves, but the manufacturing process becomes more complex
Solution Approach 1:
The patent changes the material parameters of the mask layers, using metal nitride or metal oxide for the second hard mask layer and a different material for the first hard mask layer. This parameter change provides etch selectivity, allowing the etching process to differentiate between layers and proceed automatically without complex alignment steps, thus simplifying the overall fabrication process despite the multiple layers.
Solution Approach 2:
The patent employs composite material structure with different hard mask materials (metal nitride/oxide and another material) that provide complementary functions. The composite structure enables both protection of the gate electrode and precise contact opening through etch selectivity, achieving high alignment precision while maintaining ease of manufacture through material properties rather than complex process control.
3Reliability
If metal nitride or metal oxide mask layers are used, then etch selectivity and film density improve, but the material deposition becomes more challenging
Solution Approach 1:
The patent specifies metal nitride or metal oxide materials for the second hard mask layer, changing the material parameter to achieve high etch selectivity and non-volatile etching byproducts. These material properties ensure that the etching process selectively removes the first mask layer and dielectric material while leaving the second mask layer intact, providing reliable process control despite the challenging deposition requirements.
Data Source
AI summary
An embodiment is a method including forming a first gate over a substrate, the first gate having first gate spacers on opposing sidewalls, forming a first hard mask layer over the first gate, forming a second hard mask layer over the first hard mask layer, the second hard mask layer having a different material composition than the first hard mask layer, forming a first dielectric layer adjacent and over the first gate, etching a first opening through the first dielectric layer to expose a portion of the substrate, at least a portion of the second hard mask layer being exposed in the first opening, filling the first opening with a conductive material, and removing the second hard mask layer and the portions of the conductive material and first dielectric layer above the first hard mask layer to form a first conductive contact in the remaining first dielectric layer.