Backside Through Vias for Semiconductor Wafer Thinning
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Solution Overview
Problem
Existing methods for controlling the backside grinding process in semiconductor wafer thinning are limited by mechanical precision, risking damage to active device layers due to inaccurate thickness control, and require costly optical metrology that halts the grinding process, reducing manufacturing throughput.
Innovation Solution
Incorporating through-silicon vias (TSVs) formed at specific depths as thickness indicators, which detect changes in current or eddy currents to signal when to stop grinding or polishing, allowing for precise endpoint detection and enabling pattern recognition for thickness verification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mechanical thickness dial gauge is used to control backside grinding, then manufacturing simplicity is maintained, but thickness control precision deteriorates due to intrinsic mechanical limitations
Solution Approach 1:
The patent replaces the mechanical thickness dial gauge system with an electrical measurement system. Through-silicon vias (TSVs) are formed at predetermined depths, and their electrical continuity is detected during grinding to determine endpoint. This substitution eliminates mechanical precision limitations while maintaining process simplicity, as the electrical detection can be performed continuously without complex optical infrastructure.
Solution Approach 2:
The patent introduces TSVs as intermediary structures that serve dual purposes: they function as electrical interconnects in the final device and simultaneously serve as depth markers for the grinding process. By detecting electrical continuity through these intermediary TSV structures, the system achieves precise thickness control without requiring direct measurement of the substrate thickness itself.
2Manufacturing precision
If optical metrology is used to detect endpoint, then thickness measurement precision is improved, but productivity deteriorates due to process halting and high cost
Solution Approach 1:
The patent enables continuous grinding operation by implementing electrical endpoint detection through TSVs. Unlike optical metrology that requires halting the process for measurement, the electrical continuity detection can be performed continuously during grinding without interrupting the useful action of material removal, thereby maintaining high productivity while achieving precise endpoint control.
Solution Approach 2:
The patent replaces expensive optical metrology systems with a simpler electrical detection system based on TSV continuity. This substitution eliminates the need for costly optical infrastructure and process interruptions, achieving both high precision and maintained productivity through a more economical measurement approach.
3Volume of moving object
If backside thinning is performed to 20-30 μm, then packaging size is reduced and stress performance is improved, but reliability deteriorates due to risk of damage to active device layer
Solution Approach 1:
The patent implements real-time feedback control during backside thinning by continuously monitoring electrical continuity through TSVs. When the grinding approachs the predetermined depth where TSV continuity is detected, the system provides immediate feedback to stop the grinding process. This feedback mechanism prevents over-grinding and potential damage to the active device layer, enabling safe thinning to 20-30 μm while maintaining reliability.
Solution Approach 2:
The patent performs preliminary formation of TSVs at predetermined depths before the thinning process. These pre-formed TSVs serve as early warning markers that indicate approaching critical depths. By having these preliminary structures in place, the system can detect endpoint before the active device layer is at risk, allowing aggressive thinning to 20-30 μm while protecting device integrity.
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 provides accurate and efficient control of the grinding and polishing processes, preventing damage to active device layers and improving manufacturing throughput by allowing continuous operation without the need for costly optical metrology.
Implementation Method 1
detect changes in current or eddy currents to signal when to stop grinding or polishing
Implementation Method 2
polishing continues to remove an additional amount of the substrate material
Data Source
AI summary
A wafer thinning system and method are disclosed that includes grinding away substrate material from a backside of a semiconductor device. A current change is detected in a grinding device responsive to exposure of a first set of device structures through the substrate material, where the grinding is stopped in response to the detected current change. Polishing repairs the surface and continues to remove an additional amount of the substrate material. Exposure of one or more additional sets of device structures through the substrate material is monitored to determine the additional amount of substrate material to remove, where the additional sets of device structures are located in the semiconductor device at a known depth different than the first set.