Wafer Displacement Mapping for CMP Warpage Compensation
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Solution Overview
Problem
Semiconductor wafers often warp or bow due to stress from added layers and features, leading to uneven polishing and non-uniform surfaces during chemical mechanical polishing (CMP) processes.
Innovation Solution
A system and method that includes rotating the wafer around its center, using displacement sensors to measure warpage, and adjusting carrier head parameters based on displacement data to compensate for warpage during polishing and cleaning processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the wafer is polished using conventional CMP processes, then the polishing can be completed, but the surface uniformity deteriorates due to wafer warpage
Solution Approach 1:
The system performs preliminary measurement of wafer warpage using displacement sensors before the CMP process. The measured displacement data is used to pre-calculate compensation values and adjust carrier head parameters (such as grip angle, pressure distribution, and chamber pressures) before polishing begins, enabling the system to compensate for warpage effects during the subsequent polishing process
Solution Approach 2:
The system applies local compensation by adjusting carrier head parameters specifically for regions affected by warpage. The displacement data identifies specific areas of bowing or warping, and the carrier head applies differential pressure or grip adjustments to those specific regions rather than treating the entire wafer uniformly
2Manufacturing precision
If displacement measurement is implemented to compensate for warpage, then surface uniformity improves, but device complexity increases
Solution Approach 1:
The system replaces complex mechanical measurement systems with optical displacement sensors that use light-based measurement. This substitution provides accurate warpage measurement without requiring complex mechanical contact systems, simplifying the overall measurement apparatus while maintaining precision
Solution Approach 2:
The system uses the wafer's own rotation during the measurement process to enable the displacement sensor to map the entire wafer surface. The wafer's rotational movement serves the dual purpose of both transporting the wafer and enabling comprehensive displacement measurement, eliminating the need for additional complex measurement mechanisms
3Manufacturing precision
If carrier head parameters are adjusted to compensate for warpage, then polishing quality improves, but process time increases
Solution Approach 1:
The system performs rapid displacement measurement and calculates compensation parameters before the CMP process begins. This preliminary setup, while adding some time, enables the main polishing process to proceed efficiently with pre-optimized parameters, avoiding the need for time-consuming iterative adjustments during polishing
Solution Approach 2:
The system dynamically adjusts carrier head parameters (grip angle, pressure, chamber pressures) based on measured displacement data. By changing these parameters optimally before and during the process, the system achieves high-quality polishing in fewer passes or with reduced polishing time compared to conventional uniform polishing
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
Ensures uniform polishing and cleaning by adjusting grip angle, pressure, and process parameters to account for wafer warpage, improving throughput and surface quality.
Implementation Method 1
one or more displacement sensors positioned to measure a displacement of the wafer as the wafer is rotated
Data Source
AI summary
Wafers that begin as flat surfaces during a semiconductor manufacturing process may become warped or bowed as layers and features are added to an underlying substrate. This warpage may be detected between manufacturing processes by rotating the wafer adjacent to a displacement sensor. The displacement sensor may generate displacement data relative to a baseline measurement to identify areas of the wafer that bow up or down. The displacement data may then be mapped to locations on the wafer relative to an alignment feature. This mapping may then be used to adjust parameters in subsequent semiconductor processes, including adjusting how a carrier head on a polishing process holds or applies pressure to the wafer as it is polished. A model may be trained to provide control signals for a polishing/cleaning process, or to generate metrology data.