Molybdenum Seed Layer Gradient Oxidation for Bottom-Up Gap Fill
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Solution Overview
Problem
The fabrication of microelectronic devices faces challenges with complex multilayer stacks requiring precise control of critical dimensions, leading to defects and increased costs due to conventional gap fill methods that often result in incomplete filling of features and removal of seed layers, causing seam and void formation.
Innovation Solution
A method involving a gradient oxidation process to selectively oxidize and etch metal seed layers, followed by an isotropic etch to maintain a thin seed layer at the bottom of features, allowing for a seam-free bottom-up metal gap fill using a molybdenum-containing layer, which enhances selectivity and reduces defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional gap fill methods are used to remove seed layers from the sides of gaps, then the fill material can be deposited, but the seed layer at the bottom of the gap is also removed, causing incomplete filling and defect formation
Solution Approach 1:
The patent applies local quality by creating a non-uniform seed layer structure where the seed layer thickness varies spatially: thicker at the bottom of the gap and thinner at the sides. This is achieved through controlled deposition processes that deposit material at different rates or for different durations at different locations. During etching, this thickness variation ensures that the seed layer is completely removed from the sides (where it is thin) while preserving a sufficient seed layer at the bottom (where it is thick), thus resolving the contradiction between complete side removal and bottom preservation.
Solution Approach 2:
The patent applies preliminary action by pre-forming the seed layer with a specific thickness profile before the gap fill process begins. The seed layer is deposited with greater thickness at the bottom of the gap and lesser thickness at the sides in advance of the etching and fill operations. This preliminary thickness differentiation ensures that subsequent processing steps automatically achieve the desired selective removal without requiring additional complex process steps, thereby maintaining both precision and reliability.
2Manufacturing precision
If multiple incremental processes are used to control critical dimensions, then precision is improved, but fabrication time and defect risk increase
Solution Approach 1:
The patent applies merging by combining multiple process functions into fewer integrated process steps. Specifically, the seed layer deposition process simultaneously achieves multiple objectives: it provides the seeding function for gap fill, creates the thickness profile for selective removal, and prepares the structure for subsequent processing. This consolidation reduces the total number of separate process steps required, thereby improving throughput while maintaining precision through the integrated design of the combined process.
Solution Approach 2:
The patent applies universality by designing the seed layer to serve multiple functions simultaneously: it acts as a seeding layer for metal deposition, as a sacrificial layer for defining gap boundaries, and as a structural element that influences stress distribution. This multi-functionality eliminates the need for separate dedicated layers or process steps for each function, reducing overall process complexity and increasing productivity while maintaining the precision needed for critical dimension control.
3Ease of manufacture
If the seed layer is completely removed from gap sides, then fill material can be properly deposited, but conventional methods also remove the bottom seed layer causing seams and voids
Solution Approach 1:
The patent applies local quality by creating a non-uniform seed layer structure where the seed layer thickness varies spatially: thicker at the bottom of the gap and thinner at the sides. This is achieved through controlled deposition processes that deposit material at different rates or for different durations at different locations. During etching, this thickness variation ensures that the seed layer is completely removed from the sides (where it is thin) while preserving a sufficient seed layer at the bottom (where it is thick), thus resolving the contradiction between complete side removal and bottom preservation.
4Adaptability or versatility
If complex multilayer stacks are used for microelectronic devices, then device functionality is improved, but process complexity and defect opportunities increase
Solution Approach 1:
The patent applies universality by designing the seed layer to serve multiple functions simultaneously: it acts as a seeding layer for metal deposition, as a sacrificial layer for defining gap boundaries, and as a structural element that influences stress distribution. This multi-functionality eliminates the need for separate dedicated layers or process steps for each function, reducing overall process complexity and increasing productivity while maintaining the precision needed for critical dimension 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 ensures complete removal of seed layers from the field region while maintaining a quality seed layer at the bottom, enabling efficient and defect-free metal gap filling, reducing fabrication time and costs by preventing seam and void formation.
Implementation Method 1
The exposed surface of the substrate is exposed to a gradient oxidizing process, wherein the gradient oxidizing process forms oxidized regions of the molybdenum-containing layer
Implementation Method 2
An etch back process removes the oxidized portion of the seed layer
Implementation Method 3
An isotropic etch process removes portions of the molybdenum-containing layer
Implementation Method 4
depositing a molybdenum-containing layer over an exposed surface of a substrate
Data Source
AI summary
A method and apparatus for a gap-fill in semiconductor devices are provided. The method includes forming a metal seed layer on exposed top surface of the substrate, wherein the substrate has features in the form of trenches or vias formed in the top surface of the substrate, the features having sidewalls and a bottom surface extending between the sidewalls. A gradient oxidation process is performed to oxidize exposed portions of the metal seed layer to form a metal oxide, wherein the gradient oxidation process preferentially oxidizes a field region of the substrate over the bottom surface of the features. An etch back process removes the oxidized portion of the seed layer. A second etch process removes portions of the seed layer. A metal gap-fill process fills or partially fills the features with a gap fill material.