Remote Plasma Selective Etching of Oxide and Nitride
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Solution Overview
Problem
Existing etching technologies, such as wet etching chemistries and direct plasma, face challenges in uniformly recessing oxide and nitride materials in microelectronic devices, particularly in FINFET production, due to varying fin height, pitch, and material composition, leading to uneven etch rates and potential device failure.
Innovation Solution
The use of remote plasma etching with controlled reactive species, produced by adjusting the composition of plasma gas flows containing nitrogen trifluoride (NF3), ammonia (NH3), and hydrogen (H2), allows for selective etching of oxide and nitride materials, enabling precise control of etch rates and ratios to achieve uniform recessing across diverse materials and complex device structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet etching chemistries are used to recess oxide and nitride materials, then etching can be performed, but the etch rate varies due to differences in fin height, fin pitch, and material composition, leading to uneven recessed field height
Solution Approach 1:
The patent employs a multi-step plasma etching process with different gas compositions to dynamically adjust etching parameters. The first plasma uses NF3 and H2 in a 1:4 to 1:10 ratio for initial oxide removal, while the second plasma uses NF3 and H2 in a 1:1 to 1:3 ratio for final recessing. This parameter change approach allows the process to adapt to varying fin heights and pitches, achieving uniform recessed field height across diverse device geometries
Solution Approach 2:
The etching process is divided into two distinct plasma steps with different gas compositions and process conditions. The first plasma step targets bulk oxide removal with higher H2 content, while the second plasma step provides precise control for final recessing with lower H2 content. This segmentation allows each step to be optimized for its specific function, improving overall etch uniformity across varying fin structures
2Productivity
If direct plasma is used for recess etching, then etching speed can be increased, but selectivity is reduced causing fin erosion and plasma species implantation into the fins
Solution Approach 1:
The patent uses a remote plasma source as an intermediary to deliver reactive species to the workpiece without direct plasma contact. This indirect approach maintains high etching efficiency while preventing plasma-induced damage to the fins. The remote plasma generates reactive fluorine species that etch the oxide and nitride materials efficiently, while the physical separation prevents ion bombardment that would cause fin erosion
Solution Approach 2:
The patent employs NF3-based plasma chemistry in a controlled atmosphere to achieve selective etching. The NF3 provides fluorine species that react with oxide and nitride materials while being relatively gentle on silicon fins. The inert nature of the plasma environment, combined with careful control of reactive species concentration, enables fast etching rates without compromising fin integrity
3Ease of manufacture
If hydrofluoric acid based wet etchants are used for recess etching in FINFETs with fin height ≥35 nm and fin pitch ≤50 nm, then etching can proceed, but uneven recessed field height is produced between fins
Solution Approach 1:
The patent changes plasma gas composition between two steps: the first plasma uses NF3 and H2 in a 1:4 to 1:10 ratio for bulk removal, while the second plasma uses NF3 and H2 in a 1:1 to 1:3 ratio for precise final recessing. This parameter adjustment allows the process to handle high aspect ratio fins (height ≥35 nm, pitch ≤50 nm) uniformly, achieving consistent recessed field height across narrow pitch devices
Solution Approach 2:
The patent uses periodic alternation between two plasma conditions to achieve uniform etching. The first plasma condition removes the majority of the oxide and nitride layers, then the second plasma condition provides controlled final recessing. This periodic switching between different plasma chemistries enables precise control over the etching process, ensuring uniform results even for high aspect ratio fins with narrow pitch
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 enables the production of microelectronic devices with uniform feature heights and reduced integration errors by allowing for precise control of oxide and nitride etching, even in complex geometries with varying fin pitches, enhancing the reliability of FINFET devices.
Implementation Method 1
exposing the work piece to a first plasma comprising reactive species of a first plasma gas flow to remove at least a portion of said oxide and nitride
Implementation Method 2
the first plasma gas flow comprising nitrogen trifluoride gas (NF3), ammonia gas (NH3), and hydrogen gas (H2)
Data Source
AI summary
Technologies for selectively etching oxide and nitride materials on a work piece are described. Such technologies include methods for etching a work piece with a remote plasma that is produced by igniting a plasma gas flow. Microelectronic devices including first and second fins that are laterally offset by a fin pitch to define a first field there between are also described. In embodiments the microelectronic devices include a conformal oxide layer and a conformal nitride layer on at least a portion of the first and second fins, where the conformal nitride layer is on at least a portion of the conformal oxide layer and a sacrificial oxide material is disposed within the first field.