CMOS Image Sensor Buffer Via for Ohmic Contact
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CMOS image sensors face challenges in achieving sufficient Ohmic contact between metal contact plugs and lightly-doped semiconductor substrates due to potential barriers, which can lead to dark electron generation and performance degradation.
Innovation Solution
Incorporating a buffer via with a work function between that of the semiconductor substrate and the metal contact plugs, made of materials like carbon nanotubes or organic-inorganic hybrids, to lower the potential barrier and facilitate better electron transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal contact plugs are used to contact lightly-doped semiconductor substrates, then electrical connection is established, but potential barriers form causing dark electron generation and performance degradation
Solution Approach 1:
An organic buffer layer is introduced as an intermediary between the metal contact plug and the lightly-doped semiconductor substrate. This buffer layer has a work function intermediate between the metal and semiconductor, creating a gradual transition that reduces the potential barrier height. The buffer layer acts as a mediator that facilitates smoother electron transfer, thereby reducing dark electron generation while maintaining reliable electrical connection.
Solution Approach 2:
The work function parameter of the contact interface is modified by introducing the organic buffer layer. The buffer layer's work function is specifically selected to be between that of the metal contact plug and the semiconductor substrate, creating an optimized energy level gradient. This parameter change in the contact interface properties reduces the potential barrier and minimizes harmful effects.
2Reliability
If a buffer layer is added between the contact and substrate, then potential barrier is lowered and electron transfer is improved, but device structure becomes more complex
Solution Approach 1:
A thin organic buffer film is used instead of a bulky or complex structural modification. The buffer layer is deposited as a thin film with controlled thickness, providing the necessary electrical function (work function transition) while minimizing additional structural complexity. This thin film approach maintains device simplicity while achieving the desired electrical performance improvement.
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 solution enhances the ohmic contact between the semiconductor substrate and the interconnection structure, reducing dark electron generation and improving the overall performance of the CMOS image sensor.
Implementation Method 1
a buffer interposed between the via contact and the storage node and electrically connecting the via contact to the storage node, and in which the buffer is of material having a work function between that of semiconducting material of the semiconductor substrate and material of the via contact
Data Source
AI summary
An image sensor includes a semiconductor substrate, a storage node region in the semiconductor substrate, an insulating portion on the semiconductor substrate, a via contact extending through the insulating portion, a photo-electric converter in the semiconductor substrate and spaced apart from the storage node region, an organic photo-electric layer on the insulating portion, and a buffer interposed between and electrically connecting the via contact and the storage node region.