Copper Etching Verticality via Sequential Plasma Gas Steps
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Solution Overview
Problem
The challenge in the semiconductor manufacturing process is maintaining the verticality of copper wire side surfaces during etching, particularly when using a plasma of hydrogen and argon gases, which often results in tapered shapes and difficulties with fine feature formation.
Innovation Solution
A method involving a sequence of plasma etching steps using different gas plasmas, including a hydrocarbon gas, a rare gas, and hydrogen gas, to form, sputter, and remove carbon films on the copper layer, ensuring high selectivity and preventing excess carbon accumulation, thereby improving the verticality of the copper wire side surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a plasma of hydrogen gas and argon gas is used to etch the copper layer, then the etching process can be performed, but the verticality of the side surface of the copper wire deteriorates
Solution Approach 1:
The etching process is divided into multiple sequential steps with different gas compositions: first step (hydrocarbon gas to form carbon film), second step (rare gas or mixed gas to sputter and remove carbon film and form mixed layer), and third step (hydrogen gas to remove excess carbon). This segmentation allows each step to optimize for its specific function, achieving both productivity and verticality.
Solution Approach 2:
The gas composition parameter is changed between steps to achieve different etching mechanisms. The process transitions from carbon film formation (hydrocarbon gas) to sputtering (rare gas) to carbon removal (hydrogen gas), with each gas composition optimized for its specific purpose to maintain vertical side surfaces.
2Manufacturing precision
If a plasma of hydrocarbon gas is used to form a carbon film on the copper layer, then the carbon film is formed, but excess carbon accumulates and stops the etching process
Solution Approach 1:
The process maintains continuous etching action by sequentially removing excess carbon through the second step (sputtering with rare gas) and third step (hydrogen plasma treatment). This prevents process interruption while maintaining the carbon film's beneficial effect on verticality throughout the etching process.
Solution Approach 2:
Excess carbon that would normally stop the etching process is systematically removed in the second and third steps. The carbon film is partially retained to maintain verticality while excess carbon is discarded through sputtering and hydrogen treatment, ensuring continuous productive etching.
3Productivity
If physical sputtering is used to remove the copper layer, then the copper layer is removed, but the processed shape becomes tapered
Solution Approach 1:
A mixed layer of copper and carbon is formed on the copper layer surface during the second step. This composite structure modifies the etching behavior, allowing copper removal while maintaining vertical side surfaces and preventing the tapered shape that would result from pure physical sputtering.
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 allows for reliable and high-selectivity etching of copper layers without stopping the process due to excess carbon, enhancing the verticality of the pattern side surfaces and preventing tapered shapes, even in complex geometries.
Implementation Method 1
in the first step, the film containing carbon is formed on the copper layer
Implementation Method 2
in the second step subsequent to the first step, the film containing carbon is sputtered and is thus removed
Implementation Method 3
carbon contained in the film diffuses into the copper layer, and a mixed layer of copper and carbon is formed on the surface of the copper layer
Implementation Method 4
in the third step subsequent to the second step, excess carbon is removed from the mixed layer
Data Source
AI summary
A method MT in an embodiment is a method for etching an etching target layer EL which is included in a wafer W and contains copper. The wafer W includes the etching target layer EL, and a mask MK provided on the etching target layer EL. In the method MT, the etching target layer EL is etched by repeatedly executing a sequence SQ including a first step of generating a plasma of a first gas in a processing container 12 of a plasma processing apparatus 10 in which the wafer W is accommodated, a second step of generating a plasma of a second gas in the processing container 12, and a third step of generating a plasma of a third gas in the processing container 12. The first gas contains a hydrocarbon gas, the second gas contains either a rare gas or a mixed gas of a rare gas and hydrogen gas, and the third gas contains hydrogen gas.