Deep Trench Capacitor Structure Without Metal Etch-Stop Layers
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Solution Overview
Problem
The use of metal etch-stop layers in forming trenches for capacitive devices reduces the depth and size of the dielectric sensor, leading to decreased capacitance and humidity-sensing performance in MEMS devices.
Innovation Solution
Omitting metal etch-stop layers allows for the formation of deep trench structures that extend down to the interlayer dielectric layer, increasing the volume and capacitance of the capacitive device, while reducing parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If metal etch-stop layers are used in forming trenches, then the trench formation process is simplified and manufacturing precision is improved, but the depth and size of the dielectric sensor are reduced, leading to decreased capacitance
Solution Approach 1:
The patent removes the metal etch-stop layer from the trench formation process. By extracting this layer, the etch process can proceed through the full depth of the interlayer dielectric without being terminated by the metal etch-stop, thereby enabling deeper trenches and larger dielectric sensor volume while accepting the need for alternative precision control methods
Solution Approach 2:
The patent changes the etch depth parameter by removing the constraint imposed by the metal etch-stop layer. This allows the trench etch to penetrate deeper into the interlayer dielectric, increasing the dielectric sensor volume and capacitance by extending the trench depth beyond what would be possible with the metal etch-stop layer in place
2Manufacturing precision
If metal etch-stop layers are used in forming trenches, then the trench depth is controlled, but the capacitance and humidity-sensing performance of the capacitive device are decreased
Solution Approach 1:
The metal etch-stop layer is extracted from the structure to eliminate its depth-limiting effect. This extraction enables the trench to extend deeper into the interlayer dielectric, increasing the dielectric sensor volume and improving capacitance, which directly enhances humidity-sensing performance despite losing the automatic depth control provided by the metal layer
Solution Approach 2:
The patent replaces the metal etch-stop layer with a composite approach using multiple dielectric layers (first interlayer dielectric and second interlayer dielectric) with different etch selectivities. This composite dielectric structure allows precise depth control through selective etching while enabling deeper trench formation that improves capacitance and humidity-sensing performance
3Volume of moving object
If deep trench structures are formed by omitting metal etch-stop layers, then the volume and capacitance of the capacitive device are increased, but the manufacturing process complexity increases
Solution Approach 1:
The patent uses parameter changes in the form of selective etching with different etch rates for different dielectric layers. By controlling the etch depth to reach a specific depth in the first interlayer dielectric while stopping before significantly penetrating the second interlayer dielectric, the process achieves deep trench formation with manageable complexity through precise parameter control rather than additional structural layers
4Reliability
If trenches extend deeper into the interlayer dielectric, then the capacitance increases, but the manufacturing precision for trench depth becomes more difficult to control
Solution Approach 1:
The patent employs a composite dielectric structure with two interlayer dielectric layers having different etch selectivities. The first interlayer dielectric is etched to a greater depth than the second, creating a stepped profile. This composite approach allows precise depth control because the etch process naturally stops or slows when encountering the second dielectric layer with different properties, providing self-limiting depth control while achieving the desired deep trench volume for high capacitance
Data Source
AI summary
A deep trench structure may be formed between electrodes of a capacitive device. The deep trench structure may be formed to a depth, a width, and/or an aspect ratio that increases the volume of the deep trench structure relative to a trench structure formed using a metal etch-stop layer. Thus, the deep trench structure is capable of being filled with a greater amount of dielectric material, which increases the capacitance value of the capacitive device. Moreover, the parasitic capacitance of the capacitive device may be decreased by omitting the metal etch-stop layer. Accordingly, the deep trench structure (and the omission of the metal etch-stop layer) may increase the sensitivity of the capacitive device, may increase the humidity-sensing performance of the capacitive device, and/or may increase the performance of devices and/or integrated circuits in which the capacitive device is included.