Atomic Layer Etching Process Window Optimization
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Solution Overview
Problem
Current semiconductor fabrication processes face challenges in performing atomic layer etching (ALE) in a self-limiting manner without sputtering for various materials, particularly as feature sizes shrink, requiring precise control of energy barriers and process conditions to achieve layer-by-layer etching while avoiding material damage.
Innovation Solution
The method involves identifying process conditions for atomic layer etching using a modification gas and a removal gas, with energies carefully selected to ensure self-limiting etching, including substrate temperature, bias power, and plasma generation, to maintain energy levels within specific windows that prevent sputtering and achieve high synergy in the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional etching methods are used to remove material, then etching speed is improved, but sputtering occurs causing material damage and loss of precision
Solution Approach 1:
The etching process is segmented into two distinct sequential steps: (1) a modification step where a first gas reacts with the material surface to form a modified layer, and (2) a removal step where a second gas selectively removes only the modified layer. This segmentation allows each step to be optimized independently, achieving high precision atomic-layer etching without sputtering damage.
Solution Approach 2:
The modification gas acts as an intermediary that temporarily transforms the material surface into a more reactive state. This intermediate modified layer serves as the target for selective removal by the second gas, enabling precise etching control while protecting the underlying unmodified material from direct exposure to the removal gas.
2Productivity
If high energy is applied to remove material quickly, then productivity is improved, but sputtering occurs causing material damage
Solution Approach 1:
The process utilizes parameter changes by switching between two distinct gas environments with different chemical properties. The first gas parameters are optimized for surface modification, while the second gas parameters are optimized for selective removal. This parameter switching enables efficient material removal without the need for high-energy sputtering that causes damage.
Solution Approach 2:
The process replaces mechanical/physical sputtering removal with a chemical reaction-based removal mechanism. Instead of using high-energy particle bombardment to physically knock off atoms, the method uses chemical reactions between the second gas and the modified layer to selectively remove material through volatile product formation.
3Manufacturing precision
If self-limiting etching is achieved through chemical reactions, then precision is improved, but etching speed decreases
Solution Approach 1:
The process maintains continuity of useful action by ensuring that both the modification and removal steps proceed to completion without interruption. The modification gas continuously reacts with the surface until saturation, and the removal gas continuously removes the modified layer until complete clearance, maximizing the etching rate while maintaining atomic-layer precision control.
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 precise, self-limiting etching of materials like silicon, tungsten, and tantalum, reducing sputtering and achieving high etch selectivity, thereby improving the control and efficiency of ALE processes, particularly for advanced semiconductor manufacturing.
Implementation Method 1
the modification gas is selected to adsorb to the material without etching the material
Implementation Method 2
exposing the modified surface to the removal gas and igniting a plasma to remove the modified surface
Implementation Method 3
the removal gas is selected to remove the modified surface without etching underlying unmodified material
Data Source
AI summary
Methods for evaluating synergy of modification and removal operations for a wide variety of materials to determine process conditions for self-limiting etching by atomic layer etching are provided herein. Methods include determining the surface binding energy of the material, selecting a modification gas for the material where process conditions for modifying a surface of the material generate energy less than the modification energy and greater than the desorption energy, selecting a removal gas where process conditions for removing the modified surface generate energy greater than the desorption energy to remove the modified surface but less than the surface binding energy of the material to prevent sputtering, and calculating synergy to maximize the process window for atomic layer etching.