Polysilicon Thin Film Resistor Resistance Variation Control
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Solution Overview
Problem
In semiconductor devices, particularly in analog ICs, the accuracy of voltage division by bleeder resistor circuits is compromised due to resistance variations in thin film resistors caused by processing variations during manufacturing, making it difficult to achieve the required voltage division ratio.
Innovation Solution
A semiconductor device design featuring first and second high-resistance regions made from polysilicon films, with the second high-resistance region having a higher sheet resistance than the first, and low-resistance regions arranged at the ends, along with a manufacturing method that involves ion implantation and heat treatment to define these regions, reducing resistance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thin film resistors are formed using a mask with the same width, then all thin film resistors are expected to have the same width, but processing variations cause resistance variations making it difficult to achieve the required voltage division ratio
Solution Approach 1:
The patent applies local quality by creating high-resistance regions with different sheet resistances (first high-resistance regions with sheet resistance of 10kΩ/sq to 100kΩ/sq, and second high-resistance region with sheet resistance of 50kΩ/sq to 200kΩ/sq) within the same thin film resistor structure. This local differentiation allows the resistor to compensate for processing variations and achieve more uniform resistance values across multiple resistors in the bleeder resistor circuit.
Solution Approach 2:
The patent changes the sheet resistance parameter by forming regions with different impurity concentrations through selective ion implantation. The first high-resistance regions have lower impurity concentration while the second high-resistance region has higher impurity concentration, creating distinct resistance characteristics that improve overall resistance uniformity despite processing variations.
2Measurement precision
If potentials of conductors mounted on polysilicon resistors are fixed, then a highly accurate voltage division ratio can be obtained, but the device complexity increases
Solution Approach 1:
The patent changes the sheet resistance parameter by forming regions with different impurity concentrations through selective ion implantation. The first high-resistance regions have lower impurity concentration while the second high-resistance region has higher impurity concentration, creating distinct resistance characteristics that improve overall resistance uniformity despite processing variations.
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
This configuration significantly reduces resistance variations in thin film resistors, enabling highly accurate voltage division and improving the accuracy of semiconductor devices like voltage detectors and regulators.
Implementation Method 1
forming a first impurity region of a first conductivity type by implanting impurities into the non-doped polysilicon film in a first ion implantation
Implementation Method 2
forming third impurity regions of the first conductivity type by performing a first heat treatment to diffuse impurities in the second impurity regions toward the first impurity region
Data Source
AI summary
A thin film resistor includes a high-resistance region and low-resistance regions which are formed at both ends of the high-resistance region. The high-resistance region includes first high-resistance regions and a second high-resistance region, and the first high-resistance regions are arranged at both side surfaces in a first direction in the second high-resistance region. The second high-resistance region has a higher sheet resistance than that of the first high-resistance regions.