Wafer Thickness Control via Carrier Mapping and Sensor Feedback
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Solution Overview
Problem
Conventional wafer grinding processes face challenges in accurately thinning wafers to predefined thicknesses, especially when using stacked wafers with carrier-wafers, due to variations in thickness and surface shape, which can lead to inconsistent grinding results and potential damage during the process.
Innovation Solution
The implementation of a system that positions a stacked wafer with a carrier-wafer, activates sensors to monitor thickness, and modifies the grinding process based on the carrier-wafer's surface mapping to ensure precise thickness control and prevent damage, using integrated sensors and a rotary indexer for adaptive spindle alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pressure is applied while grinding the wafer backside to achieve desired thickness, then the wafer thickness can be reduced, but the risk of wafer damage and inconsistent grinding results increases due to thickness variations and surface shape variations
Solution Approach 1:
The system performs preliminary mapping of the carrier-wafer surface shape before grinding the device wafer. This advance knowledge allows the grinding process to be pre-configured with appropriate pressure distribution and motion patterns that compensate for anticipated thickness variations, preventing damage while achieving precise thickness control
Solution Approach 2:
The system continuously monitors the device wafer thickness during grinding using sensors and adjusts the grinding parameters in real-time based on feedback. This closed-loop control prevents over-grinding and damage by dynamically adapting the grinding pressure and removing material only where needed to achieve the target thickness
2Manufacturing precision
If conventional grinding processes are used on stacked wafers with carrier-wafers, then the overall wafer stack can be thinned, but accurate thickness measurement of the device wafer becomes difficult due to the presence of the carrier-wafer
Solution Approach 1:
The system separates the thickness measurement of the device wafer from the carrier-wafer by independently mapping the carrier-wafer surface shape first, then using this information to isolate and measure only the device wafer thickness. This segmentation allows accurate measurement of the device wafer despite it being stacked on the carrier-wafer
Solution Approach 2:
The system uses the carrier-wafer surface map as an intermediary reference to determine the device wafer thickness. By establishing a baseline of the carrier-wafer geometry, the system can differentiate between carrier-wafer and device wafer contributions to the total stack thickness, enabling accurate device wafer measurement
Data Source
AI summary
Some embodiments provide methods of processing wafers comprising: positioning a stacked wafer into a position to be ground, wherein the stacked wafer comprises a first wafer secured with a carrier-wafer, wherein the first wafer is secured with the carrier-wafer such that a surface of the first wafer is exposed to be ground; initiating a grinding of the first wafer while supported by the carrier-wafer; activating one or more sensors relative to the first wafer while grinding the first wafer; determining, while grinding the first wafer, a thickness of the first wafer separate from a thickness of the carrier-wafer as a function of data from the one or more sensors; determining whether the determined thickness of the first wafer has a predefined relationship with a first thickness threshold; and halting the wafer grinding when the thickness of the first wafer has the predefined relationship with the first thickness threshold.