In-situ Pre-clean Plasma for Selective Tungsten Deposition
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Solution Overview
Problem
Existing methods for selectively depositing tungsten films face significant selectivity loss after chemical-mechanical planarization, particularly between metal and dielectric surfaces, leading to poor tungsten growth on cobalt surfaces due to non-selective passivation of both surfaces.
Innovation Solution
An in-situ pre-clean plasma process using argon or hydrogen is applied to substrates to remove surface damage and oxides, enhancing selectivity by creating a pre-cleaned substrate that allows for tungsten deposition with a selectivity of greater than or equal to 50:1 on metal surfaces relative to dielectric surfaces, employing a thermal CVD process with WF6/H2 at temperatures between 200°C to 300°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an in-situ passivation process using a surfactant is applied to improve selectivity, then selectivity is significantly improved, but tungsten cannot grow on the cobalt surface either, leaving no tungsten growth at all
Solution Approach 1:
The patent removes the harmful passivation effect from the cobalt surface by applying a pre-clean plasma treatment that selectively removes the surfactant passivation layer from metal surfaces while leaving dielectric surfaces unaffected. This extraction of the passivation layer from the metal surface restores tungsten growth capability while maintaining the selectivity benefit.
Solution Approach 2:
The patent applies a preliminary plasma clean step before the deposition process to remove surface damage and oxides from both metal and dielectric surfaces. This preliminary action creates a clean substrate that enables subsequent selective tungsten deposition on cobalt surfaces while preventing deposition on dielectric surfaces.
2Adaptability or versatility
If selective tungsten processes are used after chemical-mechanical planarization, then device integration is enabled, but severe selectivity loss occurs from >50:1 to near 1:1
Solution Approach 1:
The patent implements a preliminary plasma treatment step after CMP and before deposition to restore surface cleanliness. This preliminary action removes CMP-induced damage and oxides, recovering the selectivity that was lost during planarization while maintaining process integration capability.
Solution Approach 2:
The patent changes the surface state parameters by applying plasma treatment that modifies surface chemistry and removes contamination. This parameter change restores the surface properties needed for high-selectivity deposition while maintaining compatibility with the overall process flow.
3Manufacturing precision
If current surfactants are used for passivation, then dielectric surface selectivity is improved, but both dielectric and cobalt surfaces are passivated, preventing tungsten growth
Solution Approach 1:
The patent selectively removes the passivation layer from metal surfaces using plasma treatment while leaving dielectric surfaces unaffected. This extraction restores tungsten deposition capability on cobalt surfaces while maintaining the selective protection of dielectric surfaces.
Solution Approach 2:
The patent introduces plasma treatment as an intermediary step between passivation and deposition. This intermediary action selectively modifies the passivation state of different surfaces, enabling subsequent selective tungsten deposition by removing passivation from metal surfaces while preserving it on dielectric surfaces.
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 pre-clean plasma process significantly improves the selectivity of tungsten deposition, recovering it to levels greater than 50:1, enabling effective tungsten growth on metal surfaces while minimizing deposition on dielectric surfaces, suitable for capping layers and post-CMP defect reduction.
Implementation Method 1
The substrate is exposed to a pre-clean plasma comprising one or more of argon or hydrogen to form a pre-cleaned substrate
Implementation Method 2
The deposition conditions comprise a thermal CVD process using WF6/H2 at a temperature in the range of about 200° C. to about 300° C.
Data Source
AI summary
Methods to selectively deposit a film on a first surface (e.g., a metal surface) relative to a second surface (e.g., a dielectric surface) by exposing the surface to a pre-clean plasma comprising one or more of argon or hydrogen followed by deposition. The first surface and the second surface can be substantially coplanar. The selectivity of the deposited film may be increased by an order of magnitude relative to the substrate before exposure to the pre-cleaning plasma.