Nanosheet Transistor Backside Contacts for Self-Aligned Isolation
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Solution Overview
Problem
As nanosheet technology scales down, forming properly aligned contacts between increasingly dense devices becomes challenging due to interference and alignment issues, making it difficult to create necessary contacts effectively.
Innovation Solution
A microelectronic device with a nanosheet transistor featuring a first source/drain and a second source/drain, where a frontside contact is connected to the first source/drain and a backside contact is connected to the second source/drain, with a plurality of isolation layers beneath the nanosheet transistor, allowing the second source/drain to extend through these layers to connect with the backside contact. This is achieved by forming backside contact placeholders and alternating layers on separate substrates, flipping and bonding them, and then etching and processing to create aligned source/drain regions and contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nanosheet technology is scaled down to increase device density, then the number of devices per area increases, but alignment precision and contact formation become more difficult due to interference between closely spaced devices
Solution Approach 1:
The patent introduces a vertical dimension by forming backside contacts that extend through isolation layers from the rear surface of the substrate. This third-dimensional approach to contact formation allows contacts to be established without relying solely on planar alignment in the traditional front-side contact geometry, thereby resolving the alignment precision problem while maintaining high device density
Solution Approach 2:
The methodology performs preliminary actions by forming backside contact placeholders and isolation layers before final device assembly and contact formation. The placeholders are positioned in advance on the backside of the substrate, and isolation layers are prepared beforehand, enabling self-aligned contact formation that eliminates alignment issues during final device integration
2Area of stationary object
If devices are placed closer together to increase integration density, then area utilization improves, but interference between adjacent devices increases making contact formation more difficult
Solution Approach 1:
The patent segments the contact formation process into distinct front-side and back-side operations. By dividing the contact formation into separate stages with placeholders positioned on the backside, the methodology eliminates interference between adjacent devices during contact formation, as each device's backside contact placeholders are formed independently before final assembly
Solution Approach 2:
The backside contact placeholders serve as intermediary structures that mediate between the isolation layers and the final contact formation. These placeholders are formed in advance on the backside of the substrate and guide the subsequent formation of source/drain contacts, eliminating direct interference between adjacent devices while enabling high-density integration
Data Source
AI summary
A microelectronic device including a nanosheet transistor that includes a first source/drain and a second source/drain. A frontside contact connected to the first source/drain and a backside contact connected to the second source/drain. A plurality of isolation layers located beneath the nanosheet transistor, and the second source/drain extends through the plurality of isolation layers to connect with the backside contact.