Precision Capacitor Dielectric Stack Voltage Coefficient Control
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Solution Overview
Problem
Integrated circuits with analog-to-digital converters face limitations in precision due to nonlinear capacitance response to voltage, which restricts the accuracy of converting analog signals to digital values, primarily because existing precision capacitors have high voltage-dependent capacitance coefficients.
Innovation Solution
The development of an integrated circuit with an embedded precision capacitor featuring a dielectric stack of silicon dioxide and silicon nitride, where the silicon nitride has an atomic hydrogen content less than 25% and is deposited using N2 as a nitrogen source with radio frequency low frequency power, reducing the quadratic voltage coefficient to less than 0.5 ppm/V^2, thereby enhancing the breakdown voltage and reducing capacitance nonlinearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional precision capacitors are used in integrated circuits, then analog-to-digital conversion can be performed, but the capacitance exhibits high voltage-dependent coefficients (nonlinearity) which limits measurement precision
Solution Approach 1:
The patent changes the chemical composition parameters of the silicon nitride dielectric by controlling the atomic hydrogen content to be less than 25% (preferably less than 20%). This parameter change in the dielectric material composition directly reduces the capacitance quadratic voltage coefficient to less than 0.5 ppm/V², thereby improving measurement precision while maintaining manufacturability through controlled deposition processes
Solution Approach 2:
The patent employs a composite dielectric stack structure consisting of alternating layers of silicon dioxide and silicon nitride. This composite material approach combines the beneficial properties of both materials: silicon dioxide provides stability while the modified silicon nitride (with reduced hydrogen content) provides low voltage coefficient. The composite structure achieves superior capacitance linearity that neither material could achieve alone
2Reliability
If higher breakdown voltage is achieved through material modification, then capacitor precision improves, but the manufacturing process complexity increases due to specific deposition requirements
Solution Approach 1:
The patent modifies the deposition process parameters by applying both radio frequency (RF) and low frequency (LF) power during plasma-enhanced chemical vapor deposition of silicon nitride. This dual-frequency power approach enables precise control of the dielectric's atomic hydrogen content and breakdown voltage characteristics. The process achieves high reliability (breakdown voltage > 30V) while managing complexity through standardized semiconductor manufacturing techniques
Solution Approach 2:
The patent uses nitrogen gas (N2) as the nitrogen source during silicon nitride deposition, which serves multiple functions: it provides the necessary nitrogen for dielectric formation, acts as a plasma gas for RF-LF power coupling, and enables control of hydrogen content. This multi-functional approach consolidates several process requirements into a single deposition step, reducing overall process complexity while achieving high breakdown voltage
3Area of stationary object
If capacitor size is reduced to decrease integrated circuit area, then cost and area are reduced, but maintaining high precision becomes more difficult due to higher voltage coefficients in smaller capacitors
Solution Approach 1:
The patent changes the fundamental voltage coefficient parameter of the capacitor dielectric by controlling hydrogen content in silicon nitride to less than 25%. This parameter change reduces the quadratic voltage coefficient to less than 0.5 ppm/V², which maintains high precision even in miniaturized capacitors. The improved material properties allow precision capacitors to be scaled down without sacrificing accuracy, enabling smaller integrated circuit area while maintaining measurement precision
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 approach increases the breakdown voltage of the capacitor, allowing for higher precision in analog-to-digital conversions, enabling the use of smaller capacitors and reducing the area and cost of integrated circuits while maintaining high precision.
Implementation Method 1
depositing over the capacitor first plate a dielectric stack of alternating layers of plasma enhanced chemical vapor deposition (PECVD) silicon dioxide and PECVD silicon nitride
Implementation Method 2
the silicon nitride is deposited using N2 as a nitrogen source while applying radio frequency low frequency power
Data Source
AI summary
In a described example, an integrated circuit includes a capacitor first plate; a dielectric stack over the capacitor first plate comprising silicon nitride and silicon dioxide with a capacitance quadratic voltage coefficient less than 0.5 ppm/V2; and a capacitor second plate over the dielectric stack.