Membrane Sensor Spacers for Etch Stop Control

The patent applies preliminary action by forming spacers on the front side of the substrate before performing the backside trench etching. These spacers are positioned to define the membrane boundaries and act as etch stops during the trench formation process. By preparing these structural guides in advance, the patent prevents the trench position and diameter variations that would otherwise occur during the etching process, thereby maintaining consistent membrane dimensions and sensor performance across multiple wafers.

The patent applies segmentation by dividing the membrane structure into an inner membrane region and an outer membrane region, separated by the spacer structures. The inner membrane is defined by the spacers and is isolated from external stresses, while the outer membrane can accommodate stress. This segmentation allows the sensor to maintain stable performance by preventing stress coupling to the active sensing region, while still allowing environmental response through the outer membrane structure.

The patent introduces spacers as intermediary structures that extend from the front side through the substrate to the back side. These spacers serve as physical guides and etch stops during the backside trench etching process. By providing this intermediary reference structure, the patent prevents the trench from stopping on the oxide layer at varying depths, thereby eliminating the footing effect and ensuring consistent trench geometry and membrane shape across all sensors.