SOI Well Tap With Asymmetric Sidewall Spacers
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Solution Overview
Problem
The formation of conductive contacts, such as well taps, in integrated circuits is challenging due to variations in topology and space constraints, particularly when formed on semiconductor-on-insulator substrates, which can lead to processing difficulties and occupation of valuable space.
Innovation Solution
A well tap structure is developed with first and second opposing sidewall surfaces, featuring a first sidewall spacer with a specific vertical height and a second sidewall spacer with a lesser height, positioned around the well tap, which extends through the buried insulation layer of an SOI substrate to contact a doped well region, allowing for precise formation and reduced spatial occupancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a well tap is formed to contact the doped well region, then electrical connection is achieved, but the topology variation and processing complexity increase
Solution Approach 1:
The well tap contact structure is segmented into multiple components: a contact opening through the buried insulation layer, a conductive material filling the opening, and sidewall spacers positioned on opposing sides. This segmentation allows each component to be optimized independently while achieving reliable electrical connection without excessive topology variation
Solution Approach 2:
The sidewall spacers are positioned locally at specific locations adjacent to the well tap contact structure, providing localized control over the contact geometry and electrical connection properties without affecting the entire device topology
2Reliability
If a well tap is formed to contact the doped well region, then electrical connection is achieved, but the occupied plot space increases
Solution Approach 1:
The well tap contact structure utilizes the vertical dimension by extending through the buried insulation layer, allowing electrical connection to be achieved in the depth direction rather than requiring additional lateral space. This dimensional transition reduces the horizontal plot space occupation while maintaining reliable electrical connection
3Ease of manufacture
If the well tap structure is simplified, then manufacturing is easier, but processing precision and topology control deteriorate
Solution Approach 1:
The sidewall spacers are formed through self-aligned processes where the spacers automatically position themselves relative to the well tap contact structure. This self-service approach simplifies the manufacturing process by eliminating complex alignment steps while simultaneously achieving precise topology control through the inherent geometric relationships of the self-aligned structure
Data Source
AI summary
An illustrative device disclosed herein includes a doped well region and a conductive well tap conductively coupled to the doped well region, the conductive well tap including first and second opposing sidewall surfaces. In this example the device also includes a first sidewall spacer that has a first vertical height positioned around the conductive well tap and a second sidewall spacer positioned adjacent the first sidewall spacer along the first and second opposing sidewall surfaces of the conductive well tap, wherein the second sidewall spacer has a second vertical height that is less than the first vertical height.