Exponential-Weighted Trimmable Resistor for Tight Resistance Control
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Solution Overview
Problem
Precision resistors formed on semiconductor substrates exhibit a large distribution of resistance values due to process nonuniformity, requiring sorting and sometimes scrapping resistors with significant deviations from the target resistance.
Innovation Solution
A trimmable resistor design featuring a plurality of fused resistors with doped resistive regions and fusible links, allowing for adjustable resistance through an exponential progression by selectively blowing fuses, and a method of forming integrated circuits with interconnected unit resistors in series and parallel configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If precision resistors are formed on a semiconductor substrate using conventional processes, then manufacturing cost is reduced, but resistance value distribution becomes large due to process nonuniformity
Solution Approach 1:
The resistor is divided into multiple discrete resistive elements (first resistor, second resistor, third resistor, etc.) that can be independently trimmed by selectively opening fusible links. This segmentation allows individual adjustment of each element to achieve precise total resistance values despite process variations in the underlying substrate.
Solution Approach 2:
The resistor structure incorporates fusible links that can be selectively opened to change the circuit configuration dynamically. This allows the resistance value to be adjusted after manufacturing by trimming specific fusible links, transforming a static resistor into a dynamically adjustable one that compensates for process nonuniformity.
2Manufacturing precision
If resistors with large deviation from target resistance are scrapped, then resistance precision is improved, but productivity decreases
Solution Approach 1:
Multiple fusible links are pre-configured in the resistor structure before final trimming. This preliminary arrangement of trimmable elements allows for post-manufacturing adjustment, ensuring that resistors can be corrected to specification rather than scrapped, thereby maintaining high production yield while achieving precise resistance values.
Solution Approach 2:
Instead of scrapping resistors with deviations, the invention recovers them by selectively opening specific fusible links to adjust the resistance value. This transforms potential waste into usable components, improving both resistance precision and productivity simultaneously.
3Manufacturing precision
If multiple fusible links are added to enable trimming, then resistance precision is improved, but device complexity increases
Solution Approach 1:
Multiple resistive elements and their associated fusible links are merged into a single integrated resistor structure. This combining approach allows the trimming functionality to be incorporated within the resistor itself rather than requiring external adjustment mechanisms, reducing overall system complexity while maintaining precision.
Solution Approach 2:
The fusible links serve multiple functions: they act as current paths during normal operation and as trimmable elements for resistance adjustment. This multi-functionality reduces the need for separate trimming components, thereby reducing device complexity while enabling precise resistance control.
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 design achieves precise control over resistance values, reducing variability and enabling cost-effective production of thermistors with tight resistance distribution, suitable for sensitive applications.
Implementation Method 1
Each fused resistor includes one or more doped resistive regions formed in a semiconductor substrate. The doped resistive regions may be thermistors.
Data Source
AI summary
An electronic device, e.g. a trimmable resistor, includes a plurality of fused resistors, each fused resistor including one or more doped resistive regions formed in a semiconductor substrate. The doped resistive regions may be thermistors. Each fused resistor further includes a corresponding one of a plurality of fusible links. A first terminal of each of the fused resistors is connected to a first terminal of the corresponding fusible link. First and second interconnection buses are located over the substrate, with the first interconnection bus connecting to a second terminal of each of the fused resistors, and the second interconnection bus connecting to a second terminal of each of the fusible links. The plurality of fused resistors have resistance values that form an exponential progression.