Semiconductor Wafer Backside Patterning for Selective Thinning
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Solution Overview
Problem
Semiconductor substrate thickness adds resistance to vertical power devices, leading to performance issues, and traditional photolithography processes are costly due to multiple steps and masks.
Innovation Solution
A semiconductor wafer processing method involving laser ablation and etching processes to form a specified pattern on the back side of the wafer, reducing thickness and preserving the pattern without the need for hard masks or photosensitive materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wafer thickness is ground below 100 micron to reduce substrate resistance, then resistance of semiconductor substrate is reduced, but wafer warpage and wafer breakage occur
Solution Approach 1:
The patent applies selective thinning only in specific regions where resistance reduction is needed, rather than uniformly thinning the entire wafer. This localized approach reduces substrate resistance in critical areas while maintaining sufficient thickness in other regions to prevent warpage and breakage, thus resolving the contradiction between resistance reduction and structural integrity.
Solution Approach 2:
The wafer thinning process is segmented into different regions with different thickness requirements. The patent divides the wafer into areas requiring thinning (for resistance reduction) and areas maintaining original thickness (for structural support), allowing simultaneous achievement of low resistance and high strength through region-specific processing.
2Manufacturing precision
If traditional photolithography process is used to selectively thin substrate, then patterned thinning can be achieved, but multiple masks and process steps increase costs
Solution Approach 1:
The patent extracts and eliminates the photolithography step (photosensitive materials, exposure, and development) from the traditional selective thinning process. By using direct laser ablation or alternative masking methods, the process achieves the same patterned thinning result with fewer steps, reducing manufacturing complexity while maintaining precision.
Solution Approach 2:
The patent replaces the chemical-based photolithography system with a direct physical ablation method or simplified masking approach. This substitution eliminates the need for photosensitive materials and complex exposure equipment, reducing process steps while achieving comparable or superior patterning precision.
3Manufacturing precision
If multiple etching steps with masks are used to remove substrate material, then selective portion removal is achieved, but process time and cost increase
Solution Approach 1:
The patent employs periodic pulsed laser ablation or intermittent etching cycles that remove material in controlled bursts. This periodic action allows selective removal of substrate material with precise depth control in a single pass, eliminating the need for multiple sequential etching steps and masks, thus improving processing speed while maintaining selective removal precision.
Solution Approach 2:
The patent performs preliminary patterning or pre-thinning steps that prepare the substrate for final selective removal. By pre-defining the pattern or pre-thinning specific regions, the subsequent material removal step can proceed more efficiently with fewer iterations, reducing total process time while achieving the desired selective thinning precision.
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
Reduces substrate resistance and improves thermal performance while minimizing costs by using a single-pass laser ablation and etching process, eliminating the need for multiple masks and reducing wafer warpage and breakage.
Implementation Method 1
ablating a back side of a semiconductor wafer with a laser ablation process
Implementation Method 2
etching the back side of the semiconductor wafer with an etching process
Data Source
AI summary
A semiconductor wafer processing method, having: ablating a back side of a semiconductor wafer with a laser ablation process; and etching the back side of the semiconductor wafer with an etching process; wherein the laser ablation process forms a pattern in the back side of the semiconductor wafer; wherein the etching process preserves the pattern in the back side of the semiconductor wafer.