Multi-Tier Tungsten Filling to Prevent Voids in Narrow Openings
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Solution Overview
Problem
Conventional tungsten deposition processes in semiconductor manufacturing often result in voids and seams within high aspect ratio features, leading to incomplete filling and vulnerability to corrosion, especially in multi-tier structures with varying channel sidewall widths.
Innovation Solution
A method involving cyclic exposure of tungsten-containing gases and reducing agents, combined with nitrogen-containing gases or plasmas, to form a nucleation layer and inhibit growth at narrow portions, ensuring a void-free and seam-free tungsten fill layer deposition within a single processing chamber without transferring the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional tungsten deposition processes are used to fill high aspect ratio features, then the deposition speed is relatively fast, but voids and seams form within the features leading to incomplete filling
Solution Approach 1:
The patent employs periodic action by alternating between tungsten deposition cycles and nitrogen-containing gas exposure cycles. During deposition, tungsten is deposited in controlled intervals followed by nitrogen gas exposure that inhibits growth at narrow portions. This periodic alternation allows the fill layer to progressively advance through the high aspect ratio feature without forming voids or seams, resolving the contradiction between deposition speed and filling completeness.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the deposition parameters - specifically controlling the precursor gas flow rate, reducing agent flow rate, and nitrogen gas exposure timing. By changing these parameters cyclically, the process achieves both fast overall deposition and complete void-free filling, as the nitrogen exposure temporarily modifies growth parameters at critical narrow portions while allowing rapid deposition in wider regions.
2Ease of manufacture
If tungsten fill layer grows uniformly throughout the opening, then deposition is simple, but voids form at narrow portions due to pinching off of the opening
Solution Approach 1:
The patent implements local quality by applying nitrogen-containing gas specifically to narrow portions of the opening where void formation is problematic. The nitrogen exposure selectively inhibits tungsten growth at these critical locations while allowing normal deposition in wider regions. This localized control prevents pinching off and void formation without requiring complex process changes overall, thus resolving the contradiction between process simplicity and void prevention.
3Productivity
If high concentration of precursor gases is used to deposit tungsten quickly, then deposition speed increases, but void formation increases in multi-tier structures
Solution Approach 1:
The patent resolves this contradiction through periodic action by cycling between high-concentration precursor gas deposition (for speed) and nitrogen-containing gas exposure (to prevent voids). During deposition phases, high precursor concentration enables fast deposition, while subsequent nitrogen phases inhibit growth at narrow portions before voids can form. This periodic alternation maintains both high productivity and reliable void-free filling in multi-tier structures.
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 effectively prevents void formation and seam creation, enabling complete filling of high aspect ratio features with low resistivity tungsten, enhancing the reliability and durability of semiconductor devices.
Implementation Method 1
exposing at least one opening formed in a multi-tier portion of the substrate to a tungsten-containing gas at a precursor gas flow rate and exposing the at least one opening of the substrate to a reducing agent comprising boron at a reducing agent flow rate. The tungsten-containing gas and the reducing agent are alternated cyclically to form a nucleation layer within the at least one opening of the substrate
Implementation Method 2
exposing the at least one opening of the substrate to a nitrogen-containing gas or a nitrogen-containing plasma to inhibit growth of portions of the fill layer along the at least one opening
Data Source
AI summary
A method of forming a structure on a substrate includes forming a tungsten nucleation layer within at least one opening within a multi-tier portion of a substrate. The method includes exposing the nucleation layer a nitrogen-containing gas to inhibit growth of the nucleation layer at narrow portions within the at least one opening. The method includes exposing the at least one opening to the tungsten-containing precursor gas to form a fill layer over the nucleation layer within the at least one opening. The method includes exposing the at least one opening of the substrate to the nitrogen-containing gas or a nitrogen-containing plasma to inhibit growth of portions of the fill layer along the at least one opening.