Thermal Flow Sensor Chip Impurity Distribution
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Solution Overview
Problem
Conventional thermal flow sensor chips face challenges in achieving high sensitivity and low power consumption due to limitations in heat generation efficiency, increased risk of disconnection, and manufacturing complexity, particularly when attempting to narrow the heater wire width or thin the film thickness.
Innovation Solution
A thermal flow sensor chip design featuring a substrate with a thin film heater and opposing thermopiles, where the heater's impurity concentration is lower at the center than at the periphery, and the thermopile's impurity concentration matches the heater's main part concentration, enhancing resistance and sensitivity while reducing parasitic resistance and manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the wire width in the center part of the heater is made narrow to increase resistance, then the resistance in the center part increases, but the sensor sensitivity decreases due to reduced heat radiation area and the risk of disconnection increases due to higher current density
Solution Approach 1:
The patent applies local quality by creating a non-uniform impurity concentration distribution within the heater, specifically making the impurity concentration in the center region lower than in the outer peripheral regions. This results in higher resistance in the center part without narrowing the wire width, thereby maintaining both sensitivity and connection reliability while achieving the desired resistance distribution for improved heat generation efficiency
Solution Approach 2:
The patent changes the physical parameter of impurity concentration in the semiconductor material to control heater resistance. By adjusting the impurity concentration distribution (lower in center, higher at periphery), the resistance distribution is controlled without modifying the geometric dimensions of the heater, thus avoiding the reliability issues associated with narrow wire widths
2Ease of manufacture
If the wire width in the outer peripheral parts of the heater is widened, then the manufacturing becomes easier, but heat is easily conducted to the substrate from those parts reducing heat generation efficiency
Solution Approach 1:
The patent applies local quality by creating a non-uniform impurity concentration distribution within the heater, specifically making the impurity concentration in the center region lower than in the outer peripheral regions. This results in higher resistance in the center part without narrowing the wire width, thereby maintaining both sensitivity and connection reliability while achieving the desired resistance distribution for improved heat generation efficiency
Solution Approach 2:
The patent changes the physical parameter of impurity concentration in the semiconductor material to control heater resistance. By adjusting the impurity concentration distribution (lower in center, higher at periphery), the resistance distribution is controlled without modifying the geometric dimensions of the heater, thus avoiding the reliability issues associated with narrow wire widths
3Manufacturing precision
If the film thickness in the center part of the heater is thinned to increase resistance, then the resistance increases, but the manufacturing complexity increases due to additional etching steps and cost
Solution Approach 1:
The patent changes the physical parameter of impurity concentration in the semiconductor material to control heater resistance. By adjusting the impurity concentration distribution (lower in center, higher at periphery), the resistance distribution is controlled without modifying the geometric dimensions of the heater, thus avoiding the reliability issues associated with narrow wire widths
Solution Approach 2:
The patent makes the impurity concentration in the heater main part the same as in the thermopile silicon region, allowing both structures to be formed using the same doping process. This multi-functional approach simplifies manufacturing by using a single impurity doping step to achieve both heater and thermopile formation with appropriate resistance characteristics
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 improves heat generation efficiency, reduces power consumption, and maintains sensitivity performance while simplifying manufacturing by using the same impurity type for both heater and thermopile regions, thus overcoming previous limitations.
Implementation Method 1
a heater part (15) provided on the thin film part (11)... The heater part is formed by doping silicon with an impurity that reduces the electrical resistance
Implementation Method 2
a pair of thermopiles (13) provided on the thin film part (11) and arranged opposite each other across the heater part (15)... each thermocouple having a hot junction (12h) arranged closer to the heater part (15) and a cold junction (12c) arranged farther from the heater part (15)
Data Source
AI summary
A thermal flow sensor chip has a heater part, and a pair of thermopiles provided so as to be opposite each other across the heater part. The heater part is famed by doping silicon with an impurity that reduces the electrical resistance. In each of the thermopiles: a silicon region is formed by doping silicon with an impurity that reduces the electrical resistance; the concentration of the impurity in a heater main part, including the lengthwise center of the heater part extending in the first direction, is lower than the concentration of the impurity in a heater outer peripheral part, the heater outer peripheral part being different from the heater main part and including a lengthwise end part of the heater part; and the concentration of the impurity in the heater main part is the same as the concentration of the impurity in at least part of the silicon region of the thermopile.