Semiconductor Dummy Active Region for Isolation Groove Width Control
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Solution Overview
Problem
Semiconductor devices with trench capacitors experience increased leak current due to optical proximity effects during etching, leading to reduced capacitance and data integrity issues, particularly at the boundaries between cell regions and peripheral circuits.
Innovation Solution
Incorporating a dummy active region in the semiconductor substrate beside the cell region to equalize the optical proximity effects and maintain consistent element isolation groove widths, thereby reducing the likelihood of leak current formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If element isolation grooves are formed by etching at cell region boundaries, then the semiconductor device can be manufactured with standard processes, but optical proximity effects cause groove width reduction and increased leak current
Solution Approach 1:
The dummy active region is formed in advance before the element isolation groove etching process. This preliminary structure compensates for the optical proximity effect by providing additional light scattering centers that equalize the exposure conditions during photolithography, ensuring consistent groove widths at cell region boundaries without requiring process adjustments.
Solution Approach 2:
The dummy active region acts as an intermediary structure between the cell active regions and the element isolation grooves. It mediates the optical proximity effects by modifying the light distribution during photolithography, thereby preventing groove width reduction at critical boundaries while maintaining standard etching processes.
2Reliability
If dummy active region is added to compensate for optical proximity effects, then groove width consistency improves and leak current reduces, but device structure becomes more complex
Solution Approach 1:
The dummy active region is strategically placed only at specific locations where optical proximity effects are most pronounced, namely at the boundaries between cell regions and peripheral circuits. This localized approach improves reliability where needed without adding complexity to the entire device structure, maintaining simplicity in non-critical areas.
3Quantity of substance
If element isolation groove width is reduced due to optical proximity effects, then capacitance increases, but leak current also increases reducing data integrity
Solution Approach 1:
The dummy active region is formed preliminarily to prevent optical proximity effect-induced groove width reduction. By compensating for the exposure variations before etching, it ensures that grooves maintain their designed width, thereby preventing leak current formation while allowing the capacitor structure to achieve the desired capacitance through proper design.
Data Source
AI summary
It is disclosed a semiconductor device including a silicon substrate, provided with a plurality of cell active regions in a call region, an element isolation groove, formed in a portion, between any two of the plurality of cell active region, of the silicon substrate, a capacitor dielectric film, formed in the element isolation groove, a capacitor upper electrode, formed on the capacitor dielectric film, and configuring a capacitor together with the silicon substrate and the capacitor dielectric film. The semiconductor device is characterized in that a dummy active region is provided next to the cell region in the silicon substrate.