Semiconductor Structure With Separation Layer To Limit Wet Etch Undercut
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Solution Overview
Problem
Patterned wet chemical etching in semiconductor structures often results in an undercut of the etched material, reducing the dimension of the etched pattern compared to the masking pattern, necessitating new methods to limit the extent of this undercut.
Innovation Solution
A semiconductor structure is formed by depositing a barrier layer over a workpiece, followed by a separation layer that physically separates the barrier layer from a conductive layer, preventing direct contact and thus minimizing the undercut during wet etching. The barrier layer may comprise tungsten, while the separation layer lacks tungsten, and the conductive layer can include copper, with a specific etchant used to selectively etch the conductive layer without significantly etching the separation layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet chemical etching is used to pattern the conductive layer, then the etching process is simple and cost-effective, but undercut of the etched material occurs reducing the dimension of the etched pattern
Solution Approach 1:
A separation layer is introduced as an intermediary between the barrier layer and the conductive layer. This separation layer prevents direct contact between the etchant and the barrier layer, thereby eliminating the undercut effect while maintaining the simplicity of wet chemical etching. The separation layer acts as a mediator that allows the etching process to proceed without the harmful interaction that causes dimensional loss.
Solution Approach 2:
The original two-layer structure (barrier layer directly contacting conductive layer) is segmented into three distinct layers by inserting the separation layer. This segmentation isolates the barrier layer from the etching process, allowing the conductive layer to be etched with precise dimensional control without the barrier layer interfering and causing undercut.
2Device complexity
If the barrier layer directly contacts the conductive layer, then the structure is simple, but chemical interactions during etching contribute to undercut
Solution Approach 1:
The separation layer serves as a chemical intermediary that prevents direct interaction between the barrier layer and the conductive layer during wet etching. This intermediary layer allows the etchant to selectively remove the conductive layer without the barrier layer participating in chemical reactions that would cause undercut, thus maintaining manufacturing precision.
Solution Approach 2:
The separation layer is designed to be selectively etched or removed after serving its protective function during the conductive layer etching process. The layer self-regulates the etching process by providing temporary protection and then being removed or etched away, eliminating the need for additional complex protection steps.
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 method effectively reduces or eliminates the undercut in the conductive layer, maintaining the pattern dimensions and preventing chemical interactions that contribute to the undercut, thereby enhancing the precision and reliability of semiconductor structures.
Implementation Method 1
Patterned wet chemical etching may come with an undercut of the etched material
Implementation Method 2
a specific etchant used to selectively etch the conductive layer without significantly etching the separation layer
Implementation Method 3
A method is provided for making a semiconductor structure. A barrier layer is formed over a workpiece. A separation layer is formed over the barrier layer
Data Source
AI summary
One or more embodiments relate to a method for making a semiconductor structure, comprising: providing a workpiece; forming a barrier layer over the workpiece; forming a separation layer over the barrier layer; forming a conductive layer over the separation layer; and wet etching the conductive layer.