Semiconductor Interconnect Air Gap Exclusion Design
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Solution Overview
Problem
Conventional methods for generating air gaps in semiconductor integrated circuits fail to consider the detrimental effects of reduced parasitic capacitance, leading to increased hold timing errors, power supply noise, and increased processing time, while also risking yield due to improper air gap formation and alignment issues.
Innovation Solution
A design method and device that control air gap exclusion areas to minimize parasitic capacitance effects, specifying timing error positions, forming or deleting air gap exclusion areas based on calculated capacitance changes, and using air gap exclusion layers to prevent air gaps between interconnects and vias, thereby optimizing interconnect spacing and reducing processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If air gaps are generated without considering timing effects, then parasitic capacitance between interconnects is reduced, but hold timing errors increase
Solution Approach 1:
The patent applies local quality by selectively forming air gaps only in specific regions where they provide benefit without causing timing issues. The method identifies regions adjacent to interconnects and selectively generates air gaps in those regions, rather than uniformly across all areas, thus locally optimizing capacitance reduction while avoiding hold timing errors in critical paths.
Solution Approach 2:
The patent employs preliminary action by performing timing verification before final air gap formation. The method calculates timing values for signal paths, identifies paths that would be affected by air gaps, and uses this information to control where air gaps are formed, preventing timing errors before they occur.
2Loss of energy
If air gaps are formed between interconnects and vias, then parasitic capacitance is reduced, but alignment deviations cause air gaps to communicate with vias reducing yield
Solution Approach 1:
The patent uses an intermediary approach by introducing a via exclusion region as a buffer zone. This exclusion region acts as a mediator that prevents direct interaction between air gaps and vias, compensating for alignment deviations during fabrication. The exclusion region is calculated based on via dimensions and alignment tolerances, ensuring that even with deviations, air gaps remain isolated from vias.
3Reliability
If resist patterns for air gap exclusion are generated for all vias, then air gap communication with vias is prevented, but graphic data amount increases causing increased OPC processing time
Solution Approach 1:
The patent extracts only the essential information needed for air gap control by calculating via exclusion regions programmatically rather than generating complete resist patterns for all vias. The method extracts via position and dimension data, calculates the necessary exclusion zones, and uses this simplified representation to control air gap formation, avoiding the computational burden of full pattern generation while maintaining isolation effectiveness.
4Loss of energy
If interconnect spacing is reduced to increase air gap density, then parasitic capacitance is reduced, but timing convergence requires a huge number of steps
Solution Approach 1:
The patent performs preliminary timing analysis before air gap formation to identify which signal paths would be affected. By pre-calculating timing values and identifying critical paths, the method可以避免 iterative timing convergence steps, reducing the number of design iterations needed while still achieving optimal capacitance reduction.
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
The solution minimizes hold timing errors and power supply noise, improves yield by ensuring precise air gap formation, and reduces processing time through efficient air gap management, allowing for the production of interconnects with reduced parasitic capacitance impacts.
Implementation Method 1
an interconnect structure has been proposed in which voids (hereinafter, called air gaps) are intentionally formed of the air in an insulating film between interconnects... Such air gaps using the air whose dielectric constant is 1 are argued to give a further low relative dielectric constant than the low-k film
Data Source
AI summary
A method for designing an interconnect structure of an interconnect layer in a semiconductor integrated circuit device includes the steps of: (a) inputting layout data of the semiconductor integrated circuit device; (b) controlling an air gap exclusion area based interconnects in the layout data; and (c) outputting layout data including the air gap exclusion area determined in the step (b).