Tungsten Contact Plug Phase Control for Uniform Resistivity
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving uniform phase formation and resistivity in contact plugs during the scaling down of devices, leading to variations in contact resistance and device performance.
Innovation Solution
The process involves treating the surfaces of underlying metallic features with elements like oxygen, silicon, boron, or phosphorous to promote uniform phase formation in subsequently formed upper metallic features, followed by specific plasma and thermal treatments to control the phase of tungsten contact plugs, resulting in a high percentage of alpha-phase tungsten formation for reduced resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional contact formation processes are used during device scaling, then device density increases, but phase uniformity and resistivity control deteriorate
Solution Approach 1:
The patent applies preliminary action by performing surface treatment on the underlying metallic feature before depositing the tungsten contact plug. Specifically, oxygen plasma treatment is applied to the surface of the lower metallic feature (e.g., copper interconnect) prior to tungsten deposition. This pre-treatment modifies the surface chemistry and morphology, creating favorable conditions for uniform alpha-phase tungsten nucleation and growth, thereby ensuring phase uniformity even as device density increases.
Solution Approach 2:
The patent employs parameter changes by controlling the oxygen plasma treatment conditions (power, pressure, duration, oxygen flow rate) and tungsten deposition parameters (temperature, pressure, gas composition) to optimize phase formation. By adjusting these process parameters, the patent achieves consistent alpha-phase tungsten formation across varying device geometries and scales, maintaining manufacturing precision during technology scaling.
2Productivity
If conventional contact formation processes are used during device scaling, then device density increases, but resistivity uniformity deteriorates
Solution Approach 1:
The oxygen plasma pre-treatment is applied uniformly across all contact regions before tungsten deposition. This preliminary action ensures consistent surface properties (cleanliness, oxidation state, roughness) across the entire wafer, which leads to uniform tungsten phase formation and consequently uniform resistivity across different device regions, even as device density increases.
Solution Approach 2:
The patent controls deposition parameters such as substrate temperature, gas composition (H2/O2 ratios), and pressure to favor alpha-phase tungsten formation. By optimizing these parameters, the patent achieves low and uniform resistivity across the wafer. The oxygen plasma treatment parameters are also carefully controlled to ensure consistent surface preparation, which translates to uniform resistivity in the final contact plugs.
3Manufacturing precision
If phase control treatments are applied to underlying metallic features, then uniform phase formation improves, but process complexity increases
Solution Approach 1:
The oxygen plasma treatment is integrated into the existing contact formation process sequence, performed as a brief pre-step before tungsten deposition. This preliminary action adds minimal process steps while delivering significant improvements in phase uniformity. The treatment is automatically performed as part of the deposition chamber cycle, requiring no additional equipment or complex process integration.
4Manufacturing precision
If oxygen plasma treatment is applied to metallic surfaces, then alpha-phase tungsten formation increases, but processing time increases
Solution Approach 1:
The oxygen plasma treatment is performed in-situ immediately before tungsten deposition within the same deposition chamber, eliminating the need for chamber evacuation and re-loading. The treatment duration is optimized to be brief (typically seconds to a minute), providing sufficient surface modification without excessive processing time. This preliminary action is efficiently integrated into the overall process flow, minimizing total processing time while achieving superior phase 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 uniform resistivity and improved device performance across the wafer by controlling the phase of tungsten contact plugs, reducing resistance values and enhancing within-wafer uniformity.
Implementation Method 1
performing a first treatment on the top surface of the first metallic feature, wherein the first treatment is performed through the opening, and the first treatment is performed using a first process gas; after the first treatment, performing a second treatment
Implementation Method 2
treating the surfaces of underlying metallic features with elements like oxygen, silicon, boron, or phosphorous to promote uniform phase formation
Implementation Method 3
performing a first treatment on the top surface of the first metallic feature, wherein the first treatment is performed through the opening, and the first treatment is performed using a first process gas; after the first treatment, performing a second treatment
Implementation Method 4
performing an reduction reaction to reduce the metal oxide layer back to an elemental metal
Implementation Method 5
followed by specific plasma and thermal treatments to control the phase of tungsten contact plugs, resulting in a high percentage of alpha-phase tungsten formation
Data Source
AI summary
A method includes forming a first metallic feature, forming a dielectric layer over the first metallic feature, etching the dielectric layer to form an opening, with a top surface of the first metallic feature being exposed through the opening, and performing a first treatment on the top surface of the first metallic feature. The first treatment is performed through the opening, and the first treatment is performed using a first process gas. After the first treatment, a second treatment is performed through the opening, and the second treatment is performed using a second process gas different from the first process gas. A second metallic feature is deposited in the opening.