Semiconductor Wafer Anodization With Pulsed Current Oxide Removal
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Solution Overview
Problem
Conventional ECMP processes for semiconductor wafers face limitations in processing speed due to saturation of oxidation rate and uneven oxide film removal, leading to defective surfaces and strain in the crystal structure, particularly in larger wafers with facet regions.
Innovation Solution
Implementing a pulsed current with a density of at least 20 mA/cm2 during anodization, which allows for improved supply of reactive species and maintains stable anodization current, enabling effective oxide film formation and removal with increased abradability and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional ECMP process is used, then oxide film is formed on semiconductor wafer surface, but processing speed is limited due to saturation of oxidation rate
Solution Approach 1:
The patent applies periodic pulsed current instead of continuous current during the anodization process. By using pulsed current with specific duty cycles and frequencies, the oxidation rate is enhanced during the 'on' periods while allowing recovery and uniform distribution during 'off' periods, thereby preventing saturation and significantly improving processing speed without compromising oxide film quality
2Manufacturing precision
If conventional ECMP process is used, then oxide film is formed, but uneven oxide film removal occurs leading to defective surfaces
Solution Approach 1:
The pulsed current creates periodic oxidation and removal cycles that allow uniform oxide film formation across the wafer surface. The periodic nature ensures that oxide film is formed and removed uniformly, preventing localized defects and achieving consistent surface quality across the entire wafer including facet regions
Solution Approach 2:
The patent optimizes multiple parameters including current density, pulse width, duty cycle, and electrolyte composition to achieve uniform oxide film removal. By carefully controlling these parameters, the process achieves both high surface quality and improved productivity, eliminating the trade-off between uniformity and speed
3Manufacturing precision
If conventional ECMP process is used, then oxide film is removed, but strain in crystal structure occurs particularly in larger wafers with facet regions
Solution Approach 1:
The pulsed current allows periodic relaxation periods during which the crystal structure can recover from stress, preventing accumulation of strain particularly in facet regions of large wafers. This periodic action maintains crystal integrity while enabling effective processing of large diameter wafers
Solution Approach 2:
The patent addresses local variations in current distribution across the wafer surface, particularly in facet regions. By optimizing pulse parameters and electrolyte flow, uniform oxide film formation and removal is achieved across different regions of the wafer, preventing localized strain and maintaining crystal structure integrity throughout
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 enhances processing speed, improves surface flatness, and prevents residual oxide films, achieving a high-quality mirror surface with reduced process-modified layers and facet region defects, even in larger wafers.
Implementation Method 1
causing a pulsed current of which the current density is larger than or equal to 20 mA/cm2 to flow through the semiconductor wafer as an anode in an electrolyte solution, thereby anodizing an object surface
Implementation Method 2
a voltage is applied to an object to be processed (i.e. workpiece) as an anode in an electrolyte solution to cause a current having a predetermined current density to flow, thereby forming an oxide film on the surface of the workpiece
Implementation Method 3
causing a pulsed current of which the current density is larger than or equal to 20 mA/cm2 to flow through the semiconductor wafer as an anode in an electrolyte solution... allows for improved supply of reactive species and maintains stable anodization current
Data Source
AI summary
A surface processing method of a semiconductor wafer includes the following processes, procedures or steps: a pulsed current of which the current density is larger than or equal to 20 mA/cm2 is caused to flow through the semiconductor wafer as an anode in an electrolyte solution, thereby anodizing an object surface of the semiconductor wafer; and in a state where a surface processing pad having a grinding stone layer is disposed such that the grinding stone layer faces the object surface, an oxide generated by the anodization is selectively removed by the grinding stone layer.