Cyclic Copper Etching via Passivation Layer
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Solution Overview
Problem
The semiconductor industry faces challenges in etching copper layers due to the impracticality of subtractive processes, particularly with copper and chlorine, which result in poor morphology, surface damage, and contamination, limiting the use of copper in advanced semiconductor fabrication.
Innovation Solution
A cyclic etch process is employed, involving a chlorine exposure step to form a passivation layer on the copper surface, followed by a plasma etch step using a noble gas to incrementally remove the passivation layer and extend recesses in the copper layer, allowing for controlled and selective etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a subtractive etching process using copper and chlorine is employed, then copper can be removed from the semiconductor structure, but the process results in poor morphology, surface damage, and contamination
Solution Approach 1:
The patent introduces a passivation layer as an intermediary substance between the copper layer and the etching environment. This passivation layer prevents direct harmful interaction between chlorine and copper surfaces, thereby eliminating surface damage and contamination while enabling controlled etching of copper features
Solution Approach 2:
The patent employs an inert atmosphere by using a passivation layer that creates a protective environment around the copper surfaces. This inert barrier prevents harmful chemical reactions and contamination during the etching process, allowing precise copper removal without surface degradation
2Loss of substance
If conventional etching methods are used to remove copper, then copper removal can be achieved, but the process causes poor morphology and surface roughness
Solution Approach 1:
The passivation layer serves as a mediator that enables controlled copper removal while preserving surface morphology. By forming this protective intermediate layer, the process achieves selective copper etching without causing the poor morphology and surface roughness associated with conventional methods
Solution Approach 2:
The patent changes the chemical parameters of the etching process by introducing a passivation layer formation step. This parameter change transforms the etching mechanism from direct aggressive removal to a controlled process where the passivation layer mediates copper removal, thereby maintaining smooth surface morphology
3Productivity
If deep recesses are formed in copper layers for advanced semiconductor features, then feature density increases, but the etching process becomes more difficult to control
Solution Approach 1:
The patent employs periodic action through cyclic etching processes that repeatedly form and remove passivation layers. This periodic formation and removal enables precise control over deep recess etching, allowing high feature packing density while maintaining manufacturing precision through incremental, controlled removal cycles
Solution Approach 2:
The etching process is segmented into multiple discrete cycles of passivation layer formation and removal. This segmentation allows precise control over deep recess formation by breaking down the complex etching task into manageable steps, thereby achieving high feature density with maintained precision
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 provides a controlled, incremental, and selective etching process suitable for high-volume manufacturing, reducing surface roughness and pattern defects, and enabling the formation of deep recesses for advanced semiconductor features.
Implementation Method 1
exposing the substrate with the copper-containing layer to a chlorine gas (Cl2) to convert a portion of the copper-containing layer into copper chloride (CuCl) structures
Implementation Method 2
exposing, in a plasma etch step, the substrate with the copper-containing layer to a first plasma. The first plasma includes a noble gas and is directed to the target exposed surface of the copper-containing layer with sufficient energy to cause at least a portion of the CuCl structures to be removed from the copper-containing layer
Data Source
AI summary
In certain embodiments, a method of processing a semiconductor structure includes forming a patterned layer over a copper layer to be etched. The copper layer is disposed over a substrate. The method includes patterning the copper layer, using the patterned layer as an etch mask, by performing a cyclic etch process to form a recess in the copper layer. The cyclic etch process includes forming, in a first etch step, a passivation layer on an exposed surface of the copper layer by exposing the exposed surface of the copper layer to a chlorine gas. The passivation layer replaces at least a portion of a surface layer of the copper layer. The cyclic etch process includes subsequently etching, in a second etch step, the passivation layer using a first plasma that includes a noble gas. Each cycle of the cyclic etch process extends the recess in the copper layer.