Al-Cu Metal Layer Formation via Segmented Sputtering
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Solution Overview
Problem
The magnetron sputtering process for forming metal layers in semiconductor devices often results in undesired bumps, leading to surface roughness and reduced yield due to large, irregularly distributed crystal grains and poor etching selectivity, which impairs the appearance and functionality of the semiconductor devices.
Innovation Solution
A method involving the formation of a first metal sub-layer by magnetron sputtering at a low temperature, followed by a second metal sub-layer at a higher temperature with a heated gas stream, both composed of aluminum doped with copper, to achieve uniformly-sized small crystal grains with minimal gaps, reducing surface roughness and bumps during etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thermal magnetron sputtering is performed at high temperature to speed up metal layer formation, then productivity is improved, but manufacturing precision deteriorates due to undesired bumps and surface irregularities
Solution Approach 1:
The metal layer is divided into two sub-layers: a first metal sub-layer formed at low temperature to provide a flat base, and a second metal sub-layer formed at high temperature to achieve fast deposition. This segmentation allows each layer to serve different functions, resolving the contradiction between speed and surface quality.
Solution Approach 2:
The first metal sub-layer is formed in advance as a preliminary step before forming the second metal sub-layer. This preliminary action creates a flat foundation that prevents bump formation during the subsequent high-temperature deposition process.
2Productivity
If thermal magnetron sputtering is performed at high temperature to increase sputtering rate, then productivity is improved, but manufacturing precision deteriorates due to large irregular crystal grains
Solution Approach 1:
The deposition process is segmented into two stages with different temperatures. The first stage at low temperature produces fine uniform crystal grains, while the second stage at high temperature adds material quickly. The combined structure achieves both fine grain uniformity and high deposition rate.
Solution Approach 2:
Different temperature conditions are applied to different portions of the deposition process. The first sub-layer receives low temperature treatment for fine grain control, while the second sub-layer receives high temperature treatment for rapid deposition, achieving local optimization of crystal grain properties.
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 results in a smoother metal layer with fewer undesired bumps, enhancing the appearance and yield of semiconductor devices by minimizing surface irregularities and improving etching precision.
Implementation Method 1
Magnetron sputtering is a physical vapor deposition (PVD) technique widely used in the fabrication of semiconductor devices, in which a magnetic field is applied to the surface of a cathode target in order to confine charged plasma particles, thereby increasing the plasma density and hence the sputtering rate.
Implementation Method 2
forming a second metal sub-layer on the first metal sub-layer by performing another magnetron sputtering process and concurrently introducing a heated gas stream in the sputtering chamber
Data Source
AI summary
A semiconductor device and a method of fabricating the device are disclosed. The method of forming a metal layer includes: placing a substrate in a sputtering chamber; forming a first metal sub-layer on the substrate by performing a magnetron sputtering process; and forming a second metal sub-layer on the first metal sub-layer by performing another magnetron sputtering process and concurrently introducing a heated gas stream in the sputtering chamber, wherein the first metal sub-layer and the second metal sub-layer together constitute the metal layer and are each formed of aluminum doped with copper. The metal layer resulting from this method contains uniformly-sized small crystal grains separated from one another by minimal gaps between their grain boundaries. This imparts to the metal layer high surface flatness with fewer undesired bumps and hence good appearance, resulting in an increase in its yield.