Spiral Polysilicon Resistor Shielding for Voltage Linearity

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Solution Overview

Problem

Existing semiconductor devices with high-voltage resistors face limitations due to voltage differences causing depletion regions and non-linear resistance variations, as well as unpredictable resistivity changes during annealing, affecting the accuracy of voltage dividers.

Innovation Solution

A semiconductor device with a spiral resistive structure and conductive shielding strips, where the shielding strips are electrically coupled to the resistive structure and prevent direct contact, providing uniform protection and maintaining the resistive structure's potential, thereby reducing depletion effects and ensuring consistent voltage division.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If doped polysilicon resistors are used for high-voltage applications, then the resistors can withstand high voltages and exploit available area well, but voltage differences cause depletion regions that increase resistivity and make the division ratio non-linear and variable

Engineering Contradiction:

Improvevoltage withstanding capabilityVSAvoidresistance value stability

Core Design Contradiction:

StrengthVSStability of the object's composition

Solution Approach 1:

An intermediate conductive structure is introduced between the polysilicon resistor and the substrate. This intermediate structure acts as a mediator that provides a controlled potential reference, preventing the formation of depletion regions at the polysilicon-substrate interface while maintaining the high-voltage withstanding capability of the original resistor structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The conductive structure is designed to maintain an equipotential condition between the polysilicon resistor and the substrate by providing a controlled potential reference. This eliminates voltage differences that would otherwise cause depletion regions, thereby stabilizing the resistance value and making the division ratio linear and predictable.

Inventive Principle:

Principle #12Equipotentiality

2Ease of manufacture

If metallization regions are placed in proximity to the resistor for contacts and taps, then electrical connections are provided, but the metallization regions provide shielding that attenuates the action of forming gas during annealing, resulting in non-uniform and unpredictable resistivity changes

Engineering Contradiction:

Improveelectrical connection provisionVSAvoidresistivity control during annealing

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The annealing process is segmented into controlled stages, with the conductive structure being formed or modified at specific stages to allow uniform exposure to forming gas. This segmentation ensures that the resistivity changes are predictable and uniform, while still maintaining the necessary electrical connections through the conductive structure.

Inventive Principle:

Principle #1Segmentation

3Reliability

If a cylindrical power component is integrated concentric to the spiral resistor to limit substrate voltage effects, then the depletion of polysilicon due to substrate voltage is prevented, but the solution has no effect regarding the package and overlying protection structures

Engineering Contradiction:

Improvepolysilicon depletion preventionVSAvoidprotection against package and overhead structures

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The conductive structure is designed to serve multiple functions simultaneously: it acts as a potential reference to prevent polysilicon depletion from substrate voltage, and also provides shielding against voltage effects from the package and overlying protection structures. This multi-functionality eliminates the need for separate components for each protection function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 solution enhances the linearity and stability of the resistive structure's response to applied voltage and maintains a consistent division ratio, improving the performance and predictability of the semiconductor device.

Implementation Method 1

a conductive shielding structure, comprising a plurality of first shielding strips arranged in sequence along respective portions of the first resistive structure and separated from the first resistive structure by a second dielectric layer

Methodology Applied

Scientific EffectElectrostatic shielding: Faraday Cage

Data Source

PatentUS9461104B2Semiconductor device integrating a voltage divider and process for manufacturing a semiconductor device

Publication Date: 2016.10.04 STMICROELECTRONICS INT NV

AI summary

A semiconductor device includes: a semiconductor substrate; a high-voltage first resistive structure which extends along a spiral path above the substrate and is separated from the substrate by a first dielectric layer; and a conductive shielding structure, including a plurality of first shielding strips, which are arranged in sequence along respective portions of the first resistive structure and are separated from the first resistive structure by a second dielectric layer.