Adjacent Field Poly Features for End Gate Etch Stability
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Solution Overview
Problem
In integrated circuit (IC) fabrication, particularly at advanced nodes, the critical dimension (CD) of mask features approaches the resolution limit of optical exposure tools, leading to challenges in maintaining gate dielectric integrity and preventing leakage/shorts during the gate etch process, which affects device performance and yield.
Innovation Solution
The use of adjacent electrically connected field poly features, which extend over the edge of the active area, provides a solution by maintaining gate dielectric integrity and preventing leakage/shorts, while also increasing IC density by allowing these features to function as interconnects, thus improving device performance and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dummy field poly assist features are used adjacent to end gates, then gate etch process stability and CD uniformity are improved, but IC density is reduced due to electrical isolation requirements
Solution Approach 1:
The patent inverts the conventional approach by using electrically connected field poly features instead of electrically isolated dummy features. This reversal allows the field poly to serve dual purposes: maintaining gate etch stability through proper electrical connection while simultaneously functioning as interconnects to increase IC density.
Solution Approach 2:
The field poly features perform multiple functions: they act as assist features for gate etch process stability, serve as electrical interconnects for circuit functionality, and maintain CD uniformity. This multi-functionality eliminates the need for separate dummy features, thereby increasing IC density.
2Productivity
If electrically connected field poly features are used to increase IC density, then leakage/shorts to the topside semiconductor surface may occur, but using dummy features prevents this at the cost of reduced density
Solution Approach 1:
The patent applies different electrical connection strategies to different locations. Field poly features adjacent to end gates are electrically connected to provide etch stability, while extension portions crossing active area corners are electrically isolated to prevent leakage/shorts. This local differentiation maintains gate dielectric integrity while enabling high IC density.
3Productivity
If the critical dimension of mask features is reduced to increase IC density, then the resolution limit of optical exposure tools is approached, affecting manufacturing precision
Solution Approach 1:
The field poly assist features act as intermediaries that enhance the visibility and controllability of end gate features during lithography. By providing contrasting optical signals and maintaining proper electrical connections, they help overcome the resolution limits of optical exposure tools, enabling precise CD control at higher IC densities.
Data Source
AI summary
A method of forming an IC includes forming a first and a second gate portion using a poly mask. The first portion includes a first active poly gate having a line width W1 over an end of a first active area framed by a first active area edge and a first adjacent active field poly feature having a line width 0.8W1 to 1.3W1 in a first field region. The first field poly feature has a horizontal portion and a first extension portion along a gate width direction extending over the first active area edge having a first minimum spacing (S1). The second gate portion includes a second active poly gate over an end of a second active area framed by a second active area edge electrically connected to a second field poly feature in a second field region having a horizontal portion and a second extension portion along a gate width direction extending over the second active area edge having a second minimum spacing (S2). A dummy field poly feature is between the second active poly gate and the second field poly feature. S1≧1.25S2.