High Aspect Ratio Via Cleaning via Remote and Local Plasma
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Solution Overview
Problem
Current dry etch processes face challenges in achieving high selectivity and efficient removal of materials in high aspect ratio vias, particularly in semiconductor manufacturing, where debris at the via bottom hinders the growth of epitaxial single crystal silicon films, and liquid etchants can damage delicate surface patterns.
Innovation Solution
A method involving reactive-ion etching with remote and local plasmas, using fluorine and nitrogen-hydrogen precursors, and inert gases to selectively remove silicon oxide and amorphous silicon layers, creating a clean environment for epitaxial single crystal silicon growth, suitable for 3D NAND device formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reactive ion etching is used to etch high aspect ratio vias, then etch selectivity is improved, but debris is created at the via bottom that hinders epitaxial growth
Solution Approach 1:
The patent segments the debris removal process into distinct stages: first removing photoresist by ashing, then selectively removing silicon oxide layer, and finally removing amorphous silicon layer. Each stage uses optimized plasma conditions (different gas compositions, powers, and pressures) to remove one type of debris while preserving the underlying single crystal silicon substrate for epitaxial growth
Solution Approach 2:
The patent employs parameter changes by adjusting plasma conditions (gas composition, RF power, pressure) between different etching stages. For example, using CF4-based plasma for oxide removal and B2H6-based plasma for amorphous silicon removal, with optimized power levels to achieve selective removal of debris layers while maintaining substrate integrity
2Object-generated harmful factors
If liquid etchants are used to remove debris, then debris removal is achieved, but delicate surface patterns are damaged
Solution Approach 1:
The patent replaces liquid chemical etching with gas-phase plasma etching processes. The plasma-based removal methods use reactive species in the gas phase to selectively etch debris materials without the mechanical and chemical damage caused by liquid etchants, thereby preserving the integrity of delicate surface patterns while effectively removing debris
Solution Approach 2:
The patent uses inert or controlled atmosphere plasma processes that create a clean reaction environment. The plasma etching occurs in a controlled gas atmosphere that selectively reacts with debris materials while being gentle on the underlying patterns and substrate, avoiding the uncontrolled chemical reactions and physical damage associated with liquid etchants
3Power
If high RF power is used in remote plasma, then plasma generation efficiency is improved, but ionization in the substrate region increases causing damage
Solution Approach 1:
The patent extracts the plasma generation function to a remote region separated from the substrate processing zone. The remote plasma source generates reactive species that are then transported to the substrate region without significant ionization, separating the high-power plasma generation from the low-damage substrate exposure area
Solution Approach 2:
The patent uses an intermediary transport mechanism (gas flow through showerheads) to carry reactive species from the remote plasma region to the substrate region. This intermediary transport allows the reactive species to reach the substrate without undergoing significant ionization, thereby maintaining high plasma generation efficiency while minimizing ion damage
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 enables the exposure of single crystal silicon at the via bottom, facilitating epitaxial growth and improving the performance of 3D NAND devices by maintaining high etch selectivity and minimizing physical disturbance, while avoiding the limitations of liquid etchants.
Implementation Method 1
A method is disclosed which involves a remote plasma including fluorine and a local plasma including fluorine
Implementation Method 2
Chemical etching is used for a variety of purposes including transferring a pattern in photoresist into underlying layers
Implementation Method 3
Reactive-ion etching (RIE) involves the removal of material by ions accelerated in a predetermined direction
Implementation Method 4
The bombardment The bombardment in combination with oxidation (to remove remaining mask) creates a challenging debris at the bottom of vias
Implementation Method 5
The bottom of the vias may then possess exposed single crystal silicon which is conducive to epitaxial single crystal silicon film growth
Data Source
AI summary
A method of removing an amorphous silicon/silicon oxide film stack from vias is described. The method may involve a remote plasma comprising fluorine and a local plasma comprising fluorine and a nitrogen-and-hydrogen-containing precursor unexcited in the remote plasma to remove the silicon oxide. The method may then involve a local plasma of inert species to potentially remove any thin carbon layer (leftover from the photoresist) and to treat the amorphous silicon layer in preparation for removal. The method may then involve removal of the treated amorphous silicon layer with several options possibly within the same substrate processing region. The bottom of the vias may then possess exposed single crystal silicon which is conducive to epitaxial single crystal silicon film growth. The methods presented herein may be particularly well suited for 3d NAND (e.g. VNAND) device formation.