CMUT Wafer Membrane Bow Compensation via Variable Plates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The manufacturing of capacitive micro-machined ultrasound transducer (CMUT) wafers faces challenges in yield loss due to non-uniform membrane bow across the wafer, which affects electrical and acoustical characteristics, leading to variations in acoustical output pressure and center frequency.
Innovation Solution
The solution involves varying the configurations of compensating plates across the wafer, specifically across its diameter, to uniformly adjust the membrane bow, using different shapes, sizes, or thicknesses of compensating plates to compensate for the non-uniformity, thereby reducing yield loss in manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If compensating plates with uniform configuration are used across the wafer, then the manufacturing process is simple, but the membrane bow remains non-uniform causing yield loss
Solution Approach 1:
The patent applies local quality by varying the configuration of compensating plates according to their specific location on the wafer. Cells at different radial positions (center vs. periphery) receive compensating plates with different configurations tailored to their local membrane bow characteristics, achieving uniform membrane bow across the entire wafer while maintaining a systematic manufacturing approach.
2Manufacturing precision
If compensating plates are added to each cell, then membrane bow can be adjusted, but device complexity increases
Solution Approach 1:
The patent applies parameter changes by modifying the configuration parameters (size, shape, thickness) of compensating plates based on their position on the wafer. Instead of adding complex active components to each cell, the solution varies geometric parameters of the compensating plates to achieve the desired membrane bow control, thereby managing complexity through parameter optimization rather than structural complexity.
3Reliability
If strict specifications are enforced on all cells, then product quality is high, but yield loss increases due to non-uniform membrane bow
Solution Approach 1:
The patent applies preliminary action by pre-compensating for the known non-uniform membrane bow through strategically configured compensating plates before the cells undergo testing and sorting. By addressing the membrane bow issue during the manufacturing process itself rather than through post-manufacturing selection, the patent improves yield while maintaining quality specifications.
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 results in substantially uniform membrane bows across the wafer, improving manufacturing efficiency and reducing yield loss by ensuring consistent electrical and acoustical characteristics across the transducer array.
Implementation Method 1
Residual stress in these layers causes the cell membrane to bend upwards or downwards, depending on the sign or direction of the stress.
Implementation Method 2
each compensating plate having a configuration for influencing a bow of the membrane
Data Source
AI summary
The present invention relates to a wafer (100) being subdivided and separable into a plurality of dies. Each die (110) comprises an array of capacitive micro-machined transducer cells (1). Each cell comprises a substrate (10) comprising a first electrode (11), a membrane (13) comprising a second electrode (14), and a cavity (12) between the substrate (10) and the membrane (13). Each cell (1) of at least a part of the dies (110) comprises a compensating plate (15) on the membrane (13), each compensating plate (15) having a configuration for influencing a bow (h) of the membrane (13). The configurations of the compensating plates (13) vary across the wafer (100). The present invention further relates to a method of manufacturing such a wafer and a method of manufacturing such a die.