Optical IC Contact Formation via Segmented Etch Stops
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Solution Overview
Problem
The production of integrated circuits with optical modulators and photodetectors faces challenges in maintaining a consistently sized interlayer dielectric and controlling the contact formation process, leading to impaired photodetector operation due to excess overburden removal and varying contact lengths.
Innovation Solution
The method involves forming an upper interlayer dielectric overlying an optical modulator and a photodetector with a shoulder and plug, using an etch stop of different distances to control the formation of contacts with varying lengths, and incorporating a third contact with high copper content to physically contact the plug, ensuring proper electrical communication and reducing the risk of shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contacts are formed with varying lengths to reach different components (optical modulator, photodetector shoulder, photodetector plug), then electrical connection to all components is achieved, but the via etch process becomes difficult to control and manufacturing precision deteriorates
Solution Approach 1:
The contact formation process is segmented into multiple stages: first forming contacts of uniform length through the upper interlayer dielectric to the etch stop, then selectively removing the etch stop in specific regions to expose underlying layers, and finally forming additional contact portions in those regions. This segmentation allows the via etch process to be controlled at each stage rather than requiring one complex etch for varying depths.
Solution Approach 2:
The etch stop layer is formed preliminarily over the upper interlayer dielectric at a uniform depth, providing a standardized termination point for the first contact etch. This preliminary structure enables consistent contact formation before selective removal creates the varying contact lengths needed for different components.
2Shape
If excess overburden is removed after contact formation, then a flat surface is achieved, but the interlayer dielectric over the photodetector is removed and photodetector operation is impaired
Solution Approach 1:
The etch stop layer serves as an intermediary protective layer between the upper interlayer dielectric and the photodetector. During contact formation and overburden removal, the etch stop protects the underlying interlayer dielectric and photodetector structures. The etch stop is selectively removed only in regions where additional contact access is needed, preserving the photodetector operation while enabling necessary contact formation.
Data Source
AI summary
Integrated circuits and methods of producing such integrated circuits are provided. In an exemplary embodiment, a method of producing an integrated circuit includes forming an upper interlayer dielectric overlying an optical modulator and a photodetector, where the photodetector has a shoulder and a plug. An etch stop is formed overlying the upper interlayer dielectric. The etch stop is a first, second, and third distance from an uppermost surface of the optical modulator, the shoulder, and the plug, respectively, where the first, second, and third distances are all different from each other. A first, second, and third contact are formed through the upper interlayer dielectric, where the first, second and third contacts are in electrical communication with the optical modulator, the shoulder, and the plug, respectively.