Camera-Based Endpoint Detection for Through-Silicon Via Etching
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Solution Overview
Problem
Current endpoint detection techniques, such as Optical Emission Spectroscopy (OES) and Radio Frequency (RF) methods, are inadequate for precisely determining the endpoint of plasma etching processes, especially in through-silicon via (TSV) reveal processes that etch blanket silicon without a stop layer, leading to potential over-etching and damage.
Innovation Solution
A system utilizing a camera mounted outside the plasma processing chamber to capture sequential images of the wafer surface during etching, with a pattern recognition program matching these images against a reference image to determine the endpoint, allowing for precise detection and control of the etching operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Optical Emission Spectroscopy (OES) is used to detect endpoint, then emission changes can be detected, but detection precision deteriorates when features reduce in size and high selectivity is required
Solution Approach 1:
The patent replaces the OES optical detection system with a camera-based imaging system. Instead of measuring plasma emission spectroscopy signals, the system captures sequential images of the wafer surface during etching and uses image processing to detect when TSV nodes are exposed. This substitution enables precise endpoint detection for high-selectivity processes where OES fails to detect emission changes.
2Reliability
If high selectivity is defined for the etch process to preserve liner material, then TSV node functionality is maintained, but endpoint detection becomes extremely difficult as no new species are emitted
Solution Approach 1:
The patent replaces spectral analysis with direct visual imaging of the wafer surface. The camera system captures images showing the physical exposure of TSV nodes, providing direct visual confirmation of endpoint without relying on plasma emission species. This allows high-selectivity etching to proceed while enabling reliable endpoint detection through image pattern recognition.
Solution Approach 2:
The system creates a visual copy (image) of the wafer surface state during etching. By capturing and analyzing sequential images, the system monitors the physical state of the wafer surface and detects endpoint conditions through pattern matching, providing a direct visual representation of the etching progress and final state.
3Manufacturing precision
If fixed-time approach with pre-etch and post-etch metrology is used, then endpoint control is attempted, but process variations cause unnecessary and excess variation in results
Solution Approach 1:
The patent implements real-time feedback during the etching process by continuously capturing images and analyzing wafer surface conditions. The system provides immediate endpoint detection based on visual confirmation of TSV node exposure, allowing dynamic adjustment of the etching process. This feedback mechanism eliminates the need for fixed-time approaches and compensates for process variations, ensuring consistent results.
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 enables reliable and precise detection of endpoint conditions, reducing the risk of over-etching and ensuring accurate exposure of TSV nodes, even for infinitesimally small patterns, thereby improving the consistency and reliability of the etching process.
Implementation Method 1
A camera is mounted outside a plasma processing chamber that is configured to take sequential snapshots of a semiconductor wafer surface
Data Source
AI summary
Systems and methods for processing a semiconductor wafer includes a plasma processing chamber. The plasma processing chamber includes an exterior, an interior region with a wafer receiving mechanism and a viewport disposed on a sidewall of the plasma processing chamber providing visual access from the exterior to the wafer received on the wafer receiving mechanism. A camera is mounted to the viewport of the plasma processing chamber on the exterior and coupled to an image processor. The image processor includes pattern recognition logic to match images of emerging pattern captured and transmitted by the camera, to a reference pattern and to generate signal defining an endpoint when a match is detected. A system process controller coupled to the image processor and the plasma processing chamber receives the signal from the image processor and adjusts controls of one or more resources to stop the etching operation.