BEOL Thin Film Resistor Stack for High Resistance in Less Area
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Solution Overview
Problem
Conventional resistors in VLSI and thermistor circuits occupy substantial area due to their extended line lengths, which is a challenge in achieving dense integration and compact size necessary for modern semiconductor devices.
Innovation Solution
The development of thin film resistors integrated in the back end of line (BEOL) via level, comprising a lower resistor film, insulating layers, and upper metal lines connected via vias or contacts, allowing for a more compact and scalable design using cermet materials like ruthenium oxide and tantalum nitride.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional resistors are formed in FEOL processes with extended line lengths to achieve desired resistance characteristics, then the resistance value can be obtained, but the area occupied on the substrate increases substantially
Solution Approach 1:
The patent transitions from planar extended line resistors to vertically stacked thin film resistor structures. By adding the vertical dimension with multiple resistor films stacked on top of each other (separated by insulating layers), the patent achieves high resistance values without requiring extended horizontal line lengths, thus reducing substrate area occupancy while maintaining desired resistance characteristics
Solution Approach 2:
The patent employs composite material structures consisting of multiple thin film resistor layers (e.g., first resistor film, second resistor film) with different materials and resistance characteristics. These composite structures allow for precise control of overall resistance by combining materials with different resistivities, enabling high resistance values in compact vertical configurations rather than requiring long single-layer traces
2Manufacturing precision
If conventional resistors use extended line lengths to achieve desired resistance, then resistance characteristics can be obtained, but integration density decreases
Solution Approach 1:
By stacking resistor films vertically in the BEOL process, the patent enables multiple high-resistance elements to occupy a small footprint area. This vertical integration dramatically increases the number of resistors that can be placed on the substrate, thereby improving integration density while maintaining precise resistance control through the composite film structure
Solution Approach 2:
The patent forms the complete stacked resistor structure (multiple films and insulating layers) during the BEOL process before final interconnect formation. This preliminary structuring allows subsequent via and metal line formation to easily access and connect to the resistor elements, simplifying the overall fabrication process and enabling higher integration density
Data Source
AI summary
An apparatus includes a resistor structure within a back end of line (BEOL) via level. The resistor structure includes a lower resistor film, a first insulating layer over the lower resistor film, an upper resistor film over the first insulating layer, and a second insulating layer over the upper resistor film. First and second upper metal lines are above the second insulating layer, a first end of the upper resistor film is coupled to the first upper metal line by a first upper via or contact, and a second end of the upper resistor film is coupled to the second upper metal line by a second upper via or contact. The apparatus may be a resistor or a thermistor of a semiconductor device.