Etch Stop Layer Diffusion for Undercut-Free Semiconductor Processing
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Solution Overview
Problem
The existing etching processes for integrated circuit manufacturing, using aluminum oxide as an etch stop layer, face issues with reliability and yield due to undercut during wet etching and damage to metal layers during dry etching, leading to reliability and high Rc concerns.
Innovation Solution
A method is introduced where a diffused area is formed in the etch stop layer by diffusing material from the metal pattern into the etch stop layer, creating a compound with a lower etch rate than the non-diffused area, allowing for selective etching and minimizing damage to the metal layer, using UV light or heat to achieve this diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wet etching is used to remove the Al2O3 etch stop layer, then the etch stop layer can be properly removed, but an undercut equal to the thickness of the Al2O3 results which causes reliability and yield issues
Solution Approach 1:
The patent applies local quality by creating a non-uniform etch stop layer with different compositions at different locations. The etch stop layer includes a first portion with higher Al2O3 content (formed by thermal oxidation) and a second portion with lower Al2O3 content (formed by atomic layer deposition). This compositional gradient allows the upper portion to provide mechanical support while the lower portion enables complete etch removal without undercut, thus resolving the contradiction between reliability and manufacturing precision.
2Manufacturing precision
If dry etching is used to remove the etch stop layer, then undercut is avoided, but damage to the metal underneath the etch stop layer occurs which leads to reliability issues and high Rc
Solution Approach 1:
The patent changes the physical and chemical parameters of the etch stop layer by creating a compositional gradient through controlled thermal oxidation followed by atomic layer deposition. The thermal oxidation creates a dense Al2O3 layer that can be selectively removed by wet etching without damaging the underlying metal, while the subsequent ALD layer provides the necessary mechanical support. This parameter change in composition and structure allows wet etching to proceed without the usual undercut problem, thus resolving the contradiction between undercut control and metal layer integrity.
3Device complexity
If a standard etch stop layer is used, then the process is simple, but gap filling reliability is compromised due to undercut or metal damage
Solution Approach 1:
The patent segments the etch stop layer into two distinct functional portions: a first portion formed by thermal oxidation that serves as the etchable layer, and a second portion formed by atomic layer deposition that serves as the support layer. This segmentation allows each layer to perform its specific function optimally - the thermal oxidation layer provides etch selectivity while the ALD layer provides mechanical support - thereby improving gap filling reliability without excessive complexity increase.
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 enables precise and reliable removal of the etch stop layer without damaging the underlying metal, improving the gap filling process and reducing reliability issues, while maintaining the integrity of the metal pattern.
Implementation Method 1
transforming the exposed portion of the etch stop layer into a region having a higher etch rate to a second etchant than the non-exposed portion of the etch stop layer
Implementation Method 2
forming a diffused area in the etch stop layer by diffusing material from the metal pattern into the etch stop layer, creating a compound with a lower etch rate than the non-diffused area, allowing for selective etching and minimizing damage to the metal layer, using UV light or heat to achieve this diffusion
Data Source
AI summary
The present disclosure provides a method for forming a semiconductor device. The method includes providing a substrate having a metal pattern, and forming an etch stop layer over the substrate. The etch stop layer includes a first material. The method also includes forming a diffused area in the etch stop layer by diffusing a second material from the metal pattern to the etch stop layer, and forming an insulative layer over the etch stop layer. The diffused area includes a lower etch rate to a first etchant than the insulative layer. A semiconductor device is also provided.