Quadruple Electromagnet Array for Sputter Reactor Field Control
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Solution Overview
Problem
Current sputter reactors face challenges in achieving uniform deposition and etching of tantalum and tantalum nitride layers in high aspect-ratio holes, with limited control over magnetic fields and narrow process windows, which affects the quality and uniformity of semiconductor integrated circuits.
Innovation Solution
A plasma sputter reactor equipped with a quadruple array of electromagnetic coils, allowing for flexible magnetic field tailoring through independent powering of each coil, and a multi-step process that includes different magnetic field distributions for various deposition and etching modes, reducing stray magnetic fields and enhancing magnetic shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single magnetron is used in conventional sputter reactors, then the structure is simple and easy to operate, but the control over magnetic field distribution is limited and deposition uniformity in high aspect-ratio holes is poor
Solution Approach 1:
The single magnetron is divided into multiple independent electromagnets arranged in an array. Each electromagnet can be independently controlled to create specific magnetic field patterns, enabling precise control over ion and radical flux distribution to achieve uniform deposition in high aspect-ratio holes.
Solution Approach 2:
The electromagnets are powered independently with variable power supplies, allowing dynamic adjustment of magnetic field strength and distribution. This enables real-time optimization of deposition patterns for different hole geometries and process requirements, achieving uniform coverage in challenging high aspect-ratio structures.
2Adaptability or versatility
If conventional magnetron sputtering is used, then the process is simple, but the process window is narrow and control over deposition and etching modes is limited
Solution Approach 1:
The electromagnet array can generate different magnetic field distributions by varying power to individual coils, enabling a single reactor to perform multiple functions including deposition, etching, and cleaning operations. The system can switch between different process modes by reconfiguring magnetic field patterns without requiring separate equipment.
Solution Approach 2:
By independently controlling the power to each electromagnet, the system can dynamically change magnetic field parameters to optimize different process steps. This includes adjusting field strength, distribution patterns, and temporal sequences to achieve desired deposition or etching modes for various materials and structures.
3Manufacturing precision
If strong magnetic fields are used to improve deposition control, then deposition uniformity improves, but stray magnetic fields increase affecting surrounding equipment
Solution Approach 1:
The electromagnet array creates localized magnetic field regions targeted at specific areas of the substrate, particularly enhancing field concentration in high aspect-ratio holes where it is most needed. This localized approach achieves improved sidewall coverage without requiring uniformly strong fields across the entire chamber, thereby reducing stray magnetic fields.
Solution Approach 2:
The system uses computer-controlled power adjustment to confine magnetic fields within the processing region. By precisely controlling current in each electromagnet, the design converts what would be stray fields into useful localized field patterns, achieving both good deposition control and minimal interference with surrounding equipment.
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 configuration improves the uniformity and control of sputtering processes, enabling high sidewall coverage and low bottom coverage in vias, while reducing stray magnetic fields and allowing for flexible adaptation to different deposition steps and materials, thus enhancing the quality and reliability of semiconductor fabrication.
Implementation Method 1
A plasma sputter reactor equipped with a quadruple array of electromagnetic coils, allowing for flexible magnetic field tailoring through independent powering of each coil
Implementation Method 2
An RF power supply 34 is connected to the pedestal 30, which is conductive and act as an electrode, through a capacitive coupling circuit 36. In the presence of a plasma, the RF biased pedestal 30 develops a negative DC bias, which is effective at attracting and accelerating positive ions in the plasma
Implementation Method 3
An RF power supply 48 applies RF current to the coil 46 to induce an axial RF magnetic field within the chamber and hence generate an azimuthal RF electric field that is very effective at coupling power into the plasma and increasing its density
Implementation Method 4
The magnetron 50 preferably is small, strong, and unbalanced. The smallness and strength increase the ionization ratio and the imbalance projects a magnet field into the processing region for at least two effects of guiding sputtered ions to the wafer and reducing plasma loss to the walls
Implementation Method 5
The magnetic field extending between the poles 52, 54 in front of the target 38 creates a high-density plasma region 56 adjacent the front face of the target 46, which greatly increases the sputtering rate. The unbalanced magnetic field projects from the target 38 toward the wafer 32 to extend the plasma and to guide sputtered ions to the wafer 32 and reduce plasma diffusion to the sides
Implementation Method 6
Sputtering, alternatively called physical vapor deposition (PVD), is used to deposit several different layers of metals and related materials in the fabrication of semiconductor integrated circuits
Data Source
AI summary
A multi-step process performed in a plasma sputter chamber including sputter deposition from the target and argon sputter etching of the substrate. The chamber includes a quadruple electromagnetic coil array coaxially arranged in a rectangular array about a chamber axis outside the sidewalls of a plasma sputter reactor in back of an RF coil within the chamber. The coil currents can be separately controlled to produce different magnetic field distributions, for example, between a sputter deposition mode in which the sputter target is powered to sputter target material onto a wafer and a sputter etch mode in which the RF coil supports the argon sputtering plasma. A TaN/Ta barrier is first sputter deposited with high target power and wafer bias. Argon etching is performed with even higher wafer bias. A flash step is applied with reduced target power and wafer bias.