Aluminum Sputtering Sequence for Semiconductor Step Coverage
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Solution Overview
Problem
Conventional sputtering techniques face challenges in achieving adequate step coverage for metal layers on semiconductor devices with decreasing cell dimensions, leading to reduced reliability and wire bond strength.
Innovation Solution
A multi-step sputtering process for depositing an aluminum layer with distinct sputtering parameters in each step, including varying power levels, bias voltages, and chamber pressures, to improve step coverage and maintain or enhance wire bond reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cell dimensions are decreased to increase cell density, then current capacity and footprint are improved, but step coverage of metal layers deteriorates
Solution Approach 1:
The patent divides the single sputtering process into multiple sequential sputtering steps (first sputtering step, second sputtering step, third sputtering step), each with different parameters. This segmentation allows optimization of step coverage in high-aspect-ratio openings while maintaining overall process efficiency and achieving adequate metallization on stepped surfaces.
Solution Approach 2:
The patent systematically changes sputtering parameters between steps: power levels (first power level, second power level, third power level), bias voltages (first bias voltage, second bias voltage, third bias voltage), and chamber pressures (first pressure, second pressure, third pressure). These parameter changes enable control over deposition rate, film density, and step coverage to achieve at least 75% coverage in openings with aspect ratios greater than 1:1.
2Device complexity
If conventional sputtering is used for metal layer deposition, then process simplicity is maintained, but step coverage and reliability deteriorate
Solution Approach 1:
The patent segments the deposition process into three distinct sputtering steps, each optimized for specific requirements. This segmentation improves reliability by ensuring adequate step coverage (at least 75%) in high-aspect-ratio openings, which is critical for device performance and wire bond strength, while maintaining reasonable process complexity through systematic parameter variation.
Solution Approach 2:
The patent employs systematic parameter changes across three sputtering steps, varying power levels, bias voltages, and chamber pressures to achieve optimal step coverage and film quality. This approach enhances device reliability and wire bond strength while keeping the process complexity manageable through controlled parameter adjustments rather than fundamentally different deposition techniques.
3Productivity
If single-step sputtering is used, then manufacturing efficiency is maintained, but step coverage and wire bond strength deteriorate
Solution Approach 1:
The patent divides the deposition into three sputtering steps with different parameters, which improves wire bond strength by achieving at least 75% step coverage in openings with aspect ratios greater than 1:1. This segmentation ensures adequate metal layer coverage on stepped surfaces, providing sufficient material for reliable wire bonding while maintaining manufacturing efficiency through systematic parameter variation.
Solution Approach 2:
The patent varies power levels, bias voltages, and chamber pressures across three sputtering steps to optimize both step coverage and wire bond strength. The first sputtering step uses a first power level and first bias voltage, the second step uses a second power level and second bias voltage, and the third step uses a third power level and third bias voltage, ensuring adequate metallization for strong wire bonds while maintaining reasonable process time.
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 process achieves step coverage of at least 75% for the aluminum layer, significantly improving the reliability and bond strength of semiconductor devices compared to conventional methods.
Implementation Method 1
A multi-step sputtering process for depositing an aluminum layer with distinct sputtering parameters in each step
Data Source
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AI summary
A method for sputtering an aluminum layer on a surface of a semiconductor device is presented. The method includes three sputtering steps for depositing the aluminum layer, where each sputtering step includes at least one sputtering parameter that is different from a corresponding sputtering parameter of another sputtering step. The surface of the semiconductor device includes a dielectric layer having a plurality of openings formed through the dielectric layer.