CVD Tungsten Gap Fill Using Growth Suppression to Prevent Voids
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Solution Overview
Problem
Existing tungsten deposition processes in semiconductor manufacturing result in voids and seams due to conformal growth in multi-tier structures with varying channel sidewall widths, leading to issues like corrosion and poor electrical conductivity.
Innovation Solution
A growth suppression deposition (GSD) process using alternating tungsten-containing precursors and nucleation reducing agents, combined with nitrogen-containing gases and gapfill reducing agents, creates a non-uniform tungsten nitride passivation layer with a gradient, promoting bottom-up tungsten growth to fill channels seamlessly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conformal tungsten deposition is used to fill channels in multi-tier structures, then the deposition process is simple and uniform, but voids and seams form due to varying channel sidewall widths
Solution Approach 1:
The patent applies local quality by creating a non-uniform tungsten nitride passivation layer with varying thickness across different regions of the channel. The passivation layer is thicker at the top and thinner at the bottom, matching the varying channel width profile. This local variation in passivation layer thickness controls the local tungsten deposition rate, enabling seamless fill despite geometric variations.
Solution Approach 2:
The patent changes the parameters of the passivation layer (thickness, composition gradient) to control tungsten deposition. By adjusting the nitrogen-containing gas flow rate and using thermal treatment, the passivation layer parameters are modified to create the desired thickness profile, which in turn controls the tungsten fill uniformity across channels with varying widths.
2Productivity
If higher precursor gas concentration is used to deposit tungsten faster, then deposition speed increases, but void formation is exacerbated in high aspect ratio features
Solution Approach 1:
The patent performs preliminary action by forming the tungsten nitride passivation layer before tungsten deposition. This passivation layer is created with a specific thickness profile that pre-determines the subsequent tungsten deposition rate. By preparing this protective layer in advance, the patent controls where and how fast tungsten deposits, preventing void formation even when using higher precursor gas concentrations for faster overall deposition.
Solution Approach 2:
The tungsten nitride passivation layer acts as an intermediary between the precursor gas and the substrate. It mediates the tungsten deposition process by controlling the local reaction rate and tungsten nucleation. The passivation layer thickness modulates the precursor gas interaction, allowing faster deposition without voids by controlling where tungsten forms and how rapidly it grows.
3Ease of manufacture
If a uniform passivation layer is formed on channel walls, then deposition is straightforward, but it cannot accommodate varying channel widths in multi-tier structures
Solution Approach 1:
The patent applies dynamics by creating a passivation layer with a dynamic thickness profile rather than a static uniform layer. The passivation layer thickness varies continuously along the channel depth, adapting to the changing channel width. This dynamic structure allows the same deposition process to effectively accommodate multi-tier structures with varying geometries without requiring different processes for each tier.
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
The GSD process effectively prevents voids and seams, ensuring seamless tungsten deposition in high aspect ratio features, enhancing electrical conductivity and resistance to corrosion.
Implementation Method 1
expose the at least one opening of the substrate, disposed in the processing chamber, to a nitrogen-containing gas, a tungsten-containing gas, and a gapfill reducing agent gas, using the gas delivery system, to produce a non-uniform tungsten nitride passivation layer in the at least one opening
Implementation Method 2
The tungsten-containing precursor and the nucleation reducing agent are alternated cyclically to form a nucleation layer within the at least one opening of the substrate
Data Source
AI summary
Embodiments of the disclosure provided herein include systems and methods for forming low resistivity tungsten features in a semiconductor device manufacturing scheme using growth suppression techniques. The system includes a processing chamber, a gas delivery system, and a system controller configured to expose at least one opening formed in a multi-tier structure of a substrate to a tungsten-containing precursor and a nucleation reducing agent. The tungsten-containing precursor and the nucleation reducing agent are alternated cyclically to form a nucleation layer within the at least one opening of the substrate. The system controller is further configured to expose the at least one opening of the substrate to a nitrogen-containing gas, a tungsten-containing gas, and a gapfill reducing agent gas to produce a non-uniform tungsten nitride passivation layer in the at least one opening.