Atomic Layer Metal Etching with Selective Surface Modification
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Solution Overview
Problem
As semiconductor devices shrink, traditional subtractive etching processes face challenges in forming small copper features and achieving smooth surfaces on metals like molybdenum and ruthenium, due to uneven etching and rough sidewalls.
Innovation Solution
The method involves atomic layer etching (ALE) of metal-containing layers, where a modification gas is used to form a modified region on the surface, which is then selectively removed using an inert bombardment plasma, allowing for precise control over the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional subtractive etching is used for metal-containing layers, then the etching process can be performed with simple equipment, but the sidewalls become rough and line width control becomes imprecise
Solution Approach 1:
The etching process is divided into multiple sequential steps: modification step where reaction species chemically modify the metal surface, and removal step where physical sputtering removes the modified layer. This segmentation allows each step to be optimized independently, achieving precise line width control through self-limiting modification while maintaining manageable process complexity
Solution Approach 2:
The patent changes the fundamental parameters of the etching process by controlling the flux ratios of reaction species to physical sputtering species, and by controlling the residence time of these species on the surface. This parameter control enables transition from conventional etching to atomic layer etching, achieving superior manufacturing precision
2Manufacturing precision
If wider features are etched using traditional methods, then the etching speed is faster, but narrower features etch slower and have rougher sidewalls
Solution Approach 1:
The modification step performs preliminary chemical action on the metal surface before physical removal. Reaction species adsorb and chemically modify the metal surface in a self-limiting manner, creating a uniform modified layer that is then removed by sputtering. This preliminary chemical modification ensures uniform etching across all feature widths, producing smooth sidewalls while maintaining etching speed
Solution Approach 2:
The etching process uses periodic alternation between modification step and removal step. During modification, reaction species are introduced to chemically alter the surface; during removal, sputtering species remove the modified layer. This periodic action creates a self-limiting process that maintains consistent etching rates and smooth sidewalls across different feature dimensions
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 formation of smooth surfaces and precise control over the etching of small features, reducing line width roughness and aspect ratio-dependent etching issues, thereby improving the effectiveness of metal interconnects in advanced semiconductor technology.
Implementation Method 1
At least a region of a surface of the metal containing layer is modified to form a modified metal containing region by exposing a surface of the metal containing layer to a modification gas
Implementation Method 2
The modified metal containing region is selectively removed with respect to the unmodified metal containing region by exposing the surface of the metal containing layer to an inert bombardment plasma generated from an inert gas
Implementation Method 3
The modified metal containing region is selectively removed with respect to the unmodified metal containing region by exposing the surface of the metal containing layer to an inert bombardment plasma
Data Source
AI summary
A method for atomic layer etching a metal containing layer is provided. At least a region of a surface of the metal containing layer is modified to form a modified metal containing region by exposing a surface of the metal containing layer to a modification gas, wherein adjacent to the modified metal containing region remains an unmodified metal containing region. The modified metal containing region is selectively removed with respect to the unmodified metal containing region by exposing the surface of the metal containing layer to an inert bombardment plasma generated from an inert gas.