Metal Seed Layer Deposition for Semiconductor Recessed Features
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Solution Overview
Problem
As integrated circuit features shrink, depositing continuous metal seed layers becomes increasingly challenging, particularly in Damascene processing, leading to issues with void formation and terminal effects during electroplating.
Innovation Solution
A method involving the sequential deposition and redistribution of metal layers using iPVD sputtering and resputtering techniques to achieve improved step coverage and conformality of seed layers, with aggressive redistribution and additional flash layers to ensure adequate coverage and thickness, particularly in recessed features like vias and trenches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single layer of metal is deposited to cover recessed features, then the deposition process is simple and fast, but the sidewall coverage is insufficient and voids form in interconnects
Solution Approach 1:
The deposition process is divided into multiple sequential steps: initial deposition to fill recessed features, redistribution to improve sidewall coverage, and flash layer deposition to ensure complete coverage. This segmentation transforms a single complex deposition into manageable stages, each optimizing specific aspects of seed layer quality.
Solution Approach 2:
The method performs preliminary redistribution of the initially deposited metal layer before final flash layer deposition. This preliminary action ensures that subsequent layers are deposited on an optimized substrate, improving overall sidewall coverage and preventing void formation in interconnects.
2Productivity
If thin seed layers are used in electroplating, then the fabrication process is faster and material usage is reduced, but terminal effects occur and reliability decreases
Solution Approach 1:
The invention changes the physical and chemical parameters of the seed layer through controlled deposition and redistribution processes. By optimizing thickness, uniformity, and material distribution, the seed layer achieves adequate conductivity for electroplating while maintaining reliability and preventing terminal effects.
Solution Approach 2:
The method performs preliminary optimization of the seed layer through redistribution and flash layer deposition before the electroplating process. This ensures the seed layer has sufficient thickness and uniformity to support reliable electroplating, eliminating terminal effects while maintaining fabrication efficiency.
3Manufacturing precision
If aggressive metal redistribution is performed to improve sidewall coverage, then step coverage is enhanced, but material is removed from bottom portions of recessed features
Solution Approach 1:
The redistribution process is designed to be spatially selective, aggressively redistributing metal from field regions and top surfaces while preserving material at the bottom portions of recessed features. This local quality approach ensures sidewall coverage is improved without compromising the metal quantity needed at critical recess bottoms.
Solution Approach 2:
The flash layer deposition serves as a preliminary corrective action after redistribution. It replenishes any metal removed from recess bottoms during redistribution, ensuring both improved sidewall coverage and adequate material presence at feature bottoms before final electroplating.
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 results in improved resistance characteristics, reduced void formation, and increased reliability of interconnects, along with enhanced fabrication yield by ensuring continuous and uniform seed layer coverage.
Implementation Method 1
depositing a first layer of metal on at least the bottom portions of the recessed features and on the field region
Implementation Method 2
subsequently redistributing the deposited metal on the wafer, at least from the bottom portions of the recessed features to the sidewalls of the recessed features
Data Source
AI summary
Metal seed layers are deposited on a semiconductor substrate having recessed features by a method that involves at least three operations. In this method, a first layer of metal is deposited onto the substrate to cover at least the bottom portions of the recessed features. The first layer of metal is subsequently redistributed to improve sidewall coverage of the recessed features. Next, a second layer of metal is deposited on at least the field region of the substrate and on the bottom portions of the recessed features. The method can be implemented using a PVD apparatus that allows deposition and resputtering operations. This sequence of operations can afford seed layers with improved step coverage. It also leads to decreased formation of voids in interconnects, and to improved resistance characteristics of formed IC devices.