Heavy Metal Removal from Thinned Semiconductor Substrates
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Solution Overview
Problem
The intrinsic gettering method for semiconductor substrates is ineffective in capturing heavy metals during thinning processes, as the gettering site is ground along with the substrate, and heavy metals from polishing slurries are incorporated as positive ions, leading to contamination.
Innovation Solution
Attaching a material that lowers the potential barrier on the rear surface of the semiconductor substrate, applying a thermal treatment based on substrate thickness and resistivity, and depositing heavy metals on the rear surface to facilitate their removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the semiconductor substrate is polished to reduce thickness to 100 μm or lower, then the weight and size of electronic devices are reduced, but the gettering site is ground along with the substrate causing heavy metal elements to be incorporated from polishing slurry
Solution Approach 1:
The patent applies preliminary thermal treatment before polishing to form a modified layer with different properties that prevents heavy metal incorporation during subsequent polishing. This preliminary action creates a protective barrier that maintains gettering functionality while allowing substrate thinning.
Solution Approach 2:
The patent changes physical parameters of the substrate surface through thermal treatment, creating a modified layer with altered crystalline structure or composition that has different interaction properties with polishing slurry, thereby preventing heavy metal incorporation while maintaining mechanical properties for thinning.
2Manufacturing precision
If the semiconductor substrate is thinned by chemical-mechanical polishing, then the substrate thickness is reduced, but heavy metal elements from polishing slurry are incorporated into the substrate as positive ions
Solution Approach 1:
The patent introduces an intermediary layer or modified surface zone that acts as a barrier between the polishing slurry and the bulk substrate. This intermediary prevents the incorporation of heavy metal ions while allowing the polishing process to achieve the desired thickness precision.
Solution Approach 2:
The patent replaces or supplements the mechanical polishing process with thermal treatment that creates a modified surface layer, reducing reliance on purely mechanical removal and thereby reducing incorporation of contaminants from polishing slurry.
3Reliability
If the intrinsic gettering method is used to capture heavy metal elements, then the gettering capability is enhanced, but the gettering site is ground away during thinning process
Solution Approach 1:
The patent creates the gettering site through preliminary thermal treatment before thinning, and simultaneously creates a protective modified layer that prevents the gettering site from being ground away during subsequent polishing, thus preserving gettering capability while achieving substrate thinning.
Solution Approach 2:
The patent creates a nested structure where the gettering site is embedded within a modified layer or protective zone that extends to the surface, allowing the gettering functionality to be preserved even as the substrate is thinned, as the protective layer protects the embedded gettering site.
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 method reliably removes heavy metals from thinned semiconductor substrates, enhancing the deposition of contaminants to the rear surface and preventing them from reaching the active circuit area, thus maintaining device properties.
Implementation Method 1
applying a thermal treatment to the semiconductor substrate under a condition based on a thickness and a resistivity of the semiconductor substrate
Implementation Method 2
attaching, to a rear surface of the semiconductor substrate, a material that lowers a potential barrier of the rear surface
Data Source
AI summary
To provide a method of removing a heavy metal contained in a thinned semiconductor substrate.A method of removing a heavy metal in a semiconductor substrate of the present invention comprises: attaching, to a rear surface of the semiconductor substrate, a material that lowers a potential barrier of the rear surface of the semiconductor substrate, on a front surface of which a circuit is to be formed or is formed; applying a thermal treatment to the semiconductor substrate under a condition based on a thickness and a resistivity of the semiconductor substrate; and, depositing the heavy metal in the semiconductor substrate on the rear surface.