Stress-Compensated Metal Layer Fabrication for Semiconductor Defect Reduction
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Solution Overview
Problem
Conventional methods for depositing thick metal layers in semiconductor devices often result in metal defects due to thermal expansion and stress issues, which affect yield and reliability, despite attempts to manage thermal budgets by breaking the deposition process into multiple steps.
Innovation Solution
The method involves segmenting the metal layer into portions with stress-compensating layers in between, where each portion is deposited with specific stress characteristics, counteracting the inherent stress in the metal layer to reduce defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the metal layer thickness is increased to 1-3 microns for inductor fabrication, then the inductor performance is improved, but metal defects occur due to thermal expansion and stress during deposition
Solution Approach 1:
The patent divides the thick metal layer into multiple sub-layers by interrupting the deposition process into separate steps. Between these steps, the substrate is cooled down to reduce thermal stress accumulation. This segmentation allows the thick metal layer to be formed while managing thermal budget and reducing metal defects that would otherwise occur with continuous deposition.
Solution Approach 2:
The deposition process is conducted periodically with alternating deposition and cooling cycles. The substrate undergoes repeated heating during deposition followed by cooling periods, creating a periodic thermal cycle that prevents excessive stress buildup while still achieving the required thick metal layer for inductor fabrication.
2Volume of moving object
If the deposition time is extended to achieve thick metal layers, then the metal thickness is sufficient for inductors, but wafer temperature increases causing metal defects upon cooling
Solution Approach 1:
The continuous deposition process is segmented into multiple discrete deposition steps. After each deposition step, the substrate is cooled down before the next deposition begins. This segmentation of the deposition timeline allows thick metal layers to be formed while controlling peak wafer temperature and preventing excessive thermal stress that causes metal defects.
Solution Approach 2:
The patent implements periodic deposition and cooling cycles. Instead of continuous deposition that would cause monotonically increasing temperature, the process alternates between deposition (heating) and cooling phases, creating a periodic temperature profile that manages thermal budget while achieving required metal thickness.
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 significantly reduces metal defects, enhancing product reliability and yield by effectively managing stress and thermal expansion during the deposition process.
Implementation Method 1
A stress-compensating layer is deposited over the first portion, such that the stress-compensating layer has a stress associated with it that is opposite to the compressive or tensile stress associated with the first portion
Implementation Method 2
When the wafer is finally cooled down at the end of the deposition process, the thick metal will often contract and the resulting force will cause metal defects
Data Source
AI summary
The invention, in one aspect, provides a method of manufacturing a semiconductor device. This method includes providing a semiconductor substrate and depositing a metal layer over the semiconductor substrate that has an overall thickness of about 1 micron or greater. The metal layer is formed by depositing a first portion of the thickness of the metal layer, which has a compressive or tensile stress associated therewith over the semiconductor substrate. A stress-compensating layer is deposited over the first portion, such that the stress-compensating layer imparts a stress to the first portion that is opposite to the compressive or tensile stress associated with the first portion. A second portion of the thickness of the metal layer is then deposited over the stress-compensating layer.