Metal-Metal Capacitor Etching Control via Nested Structure and Stop Layer
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Solution Overview
Problem
Existing metal-metal capacitors face challenges in achieving high capacitance density due to narrow process windows and instability in etching processes, leading to issues with dielectric thickness control and leakage current.
Innovation Solution
The method involves forming a metal-metal capacitor structure using multiple mask layers to control etching steps, eliminating the need for a cap layer and metal layer as etching buffers, thereby widening the process window and stabilizing the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the dielectric thickness is reduced to increase capacitance density, then the capacitance density is improved, but the leakage current increases and RF loss tangent deteriorates
Solution Approach 1:
The patent implements a nested capacitor structure where an upper capacitor (C2) is formed within the same footprint as the lower capacitor (C1). The upper capacitor consists of metal layer 16, capacitor dielectric layer 15, and metal layer 14, while the lower capacitor consists of metal layer 12, capacitor dielectric layer 13, and metal layer 14. This nesting allows doubling the capacitance density without reducing dielectric thickness, thereby avoiding increased leakage current and RF loss tangent.
2Ease of manufacture
If cap layer and metal layer are used as etching buffers to control etching stop, then the etching process is simplified, but the process window becomes narrow and etching results become unstable
Solution Approach 1:
The patent introduces a dedicated etch stop layer (silicon nitride layer 24) as an intermediary between the capacitor dielectric layer 13 and the underlying substrate. This etch stop layer has distinct etching characteristics that provide a clear and stable etching stop point, eliminating the need to rely on cap layer and metal layer as etching buffers. The etch stop layer ensures precise control of etching depth with a wide process window, thereby improving manufacturing precision while maintaining ease of manufacture.
3Device complexity
If cap layer and metal layer are used as etching buffers, then the structure is simplified, but the etching process becomes sensitive to variations in film properties and etching rates
Solution Approach 1:
The patent introduces a dedicated etch stop layer (silicon nitride layer 24) as an intermediary with stable and distinct etching characteristics. This etch stop layer is specifically designed to provide a reliable etching stop point that is insensitive to variations in film properties and etching rates of other layers. The etch stop layer acts as a buffer that absorbs process variations, thereby stabilizing the etching process and ensuring consistent etching results across different production batches and equipment.
Data Source
AI summary
A method of making a metal-metal capacitor is disclosed, in which a first metal layer, a first dielectric layer, a second metal layer, a second dielectric layer, and a third metal layer are formed in the order over a substrate; an upper capacitor is defined by etching using a first mask, wherein the stop of the etching can be controlled; a lower capacitor is defined by etching using a second mask; and an anti-reflective third mask is formed to cover the surface, and the capacitor border and metal interconnect conductive wire are defined, so as to make a metal-metal capacitor with a stable structure in a wide process window.