Tungsten Hard Mask Etching with Patterned Region Protection
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Solution Overview
Problem
The challenge lies in the selective removal of metal-containing hard masks, such as tungsten-containing layers, which exhibit substantial thickness variations, making it difficult to remove them without damaging underlying layers during etching processes.
Innovation Solution
The method involves generating a first plasma to deposit a film over patterned regions of the tungsten-containing layer while removing portions in unpatterned regions, followed by a second plasma to remove the deposited film and additional layer portions, and a third plasma to fully remove the tungsten-containing layer without damaging the underlying layers, utilizing specific gas compositions and RF power levels to achieve selective etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If metal-containing hard masks are used for etching deep features, then etching capability is improved, but selective removal becomes difficult due to thickness variations
Solution Approach 1:
The removal process is segmented into multiple distinct plasma steps, each targeting specific regions or functions: (1) depositing a first film in patterned regions while removing tungsten in unpatterned regions, (2) removing the first film and additional tungsten portions, and (3) fully removing remaining tungsten-containing layer. This segmentation allows selective removal despite thickness variations.
Solution Approach 2:
A first film is deposited over the patterned regions before complete tungsten removal. This preliminary action protects the patterned regions during subsequent removal steps while allowing unpatterned region tungsten to be removed, enabling selective removal based on thickness variations.
2Device complexity
If conventional photoresists are used, then process simplicity is maintained, but deep high aspect ratio features cannot be etched
Solution Approach 1:
The patent changes the material parameter of the hard mask from conventional photoresist to metal-containing layers (tungsten, tungsten carbide, tungsten nitride, etc.), which enables etching of deep high aspect ratio features. The multi-step plasma removal process then manages the complexity of removing these metal layers selectively.
3Productivity
If high RF power is used for plasma generation, then etching speed is improved, but damage to underlying layers increases
Solution Approach 1:
The etching process is segmented into multiple plasma steps with different power levels and gas compositions. This allows aggressive etching in early steps when protective films are present, and gentler etching in later steps to remove remaining material without damaging underlying layers.
Solution Approach 2:
A first film is deposited as an intermediary protective layer over patterned regions. This film acts as a mediator that allows high-power plasma etching to proceed without directly exposing and damaging the underlying layers, while still enabling removal of tungsten in unpatterned regions.
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 allows for the selective and efficient removal of tungsten-containing layers with high aspect ratios, maintaining pattern integrity and achieving etching ratios greater than 300:1 relative to silicon oxide and 1000:1 relative to silicon nitride, while minimizing damage to underlying layers.
Implementation Method 1
generating a first plasma in a process volume of a plasma chamber... depositing a first film over the patterned region of the tungsten-containing layer with the first plasma
Implementation Method 2
removing portions of the unpatterned region of the tungsten-containing layer with the first plasma
Implementation Method 3
generating a second plasma in the process volume of the plasma chamber after generating the first plasma, and removing the first film and portions of the patterned region and the unpatterned region of the tungsten-containing layer with the second plasma
Implementation Method 4
wherein an RF bias is supplied to the substrate support at a first power level during the generation of the first plasma and the RF bias is supplied to the substrate support at a second power level during generation of the second plasma
Data Source
AI summary
A method of removing a metal-containing layer (e.g., tungsten) from a substrate is provided. The method includes generating a first plasma in a process volume of a plasma chamber when a patterned device is disposed on a substrate support in the process volume. The patterned device includes a patterned region and an unpatterned region; a substrate; a tungsten-containing layer formed over the substrate; a supporting layer disposed between the tungsten-containing layer and the substrate. The patterned region includes exposed surfaces of the supporting layer and the unpatterned region does not include any exposed surfaces of the supporting layer. The method further includes depositing a first film over the patterned region of the tungsten-containing layer with the first plasma; and removing portions of the unpatterned region of the tungsten-containing layer with the first plasma without depositing the first film over the unpatterned region.