FIR Sensor Dielectric Thickness Control Using a Sacrificial Metal Layer

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Solution Overview

Problem

Existing far infrared (FIR) sensor devices manufactured using CMOS processes have a fixed sensor dielectric layer thickness, limiting the precision and adjustability of sensor performance and frame rate when sensing FIR signals.

Innovation Solution

A sacrificial metal layer is used to determine the thickness of the sensor dielectric layer, with a two-step etching process involving anisotropic and isotropic etch steps, employing etch solutions like TMAH and KOH, to form a thinner and more controllable dielectric layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the sensor dielectric layer thickness is fixed by CMOS process limitations, then the manufacturing process is simple, but the sensor performance precision and frame rate are adversely impacted

Engineering Contradiction:

Improvesensor dielectric layer thickness controlVSAvoidmanufacturing process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

A sacrificial metal layer is deposited on the sensor dielectric layer before final processing. This sacrificial layer serves as a thickness reference that is removed later, allowing the sensor dielectric layer thickness to be precisely controlled based on the known thickness of the sacrificial layer, thereby achieving precise thickness control without complicating the overall manufacturing process

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The sacrificial metal layer acts as an intermediary element between the sensor dielectric layer and the etching process. By using this intermediate layer with known thickness, the system can transfer the thickness specification from the sacrificial layer to the sensor dielectric layer, enabling precise thickness control while maintaining manufacturing simplicity

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the sensor dielectric layer thickness cannot be adjusted, then the manufacturing process is straightforward, but the sensor performance and frame rate cannot be precisely controlled

Engineering Contradiction:

Improvesensor dielectric layer thickness adjustabilityVSAvoidmanufacturing process complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The sacrificial metal layer is deposited in advance with a predetermined thickness that corresponds to the desired sensor dielectric layer thickness. This preliminary action establishes the thickness reference before any etching occurs, enabling flexible thickness adjustment by simply changing the sacrificial layer thickness without modifying the overall process flow

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The thickness of the sensor dielectric layer is controlled by changing the thickness parameter of the sacrificial metal layer. By adjusting the deposition parameters or material composition of the sacrificial layer, the system can flexibly control the final sensor dielectric layer thickness, achieving adaptability while maintaining process simplicity

Inventive Principle:

Principle #35Parameter changes

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 allows for precise adjustment of the sensor dielectric layer thickness, enhancing the accuracy and stability of FIR signal sensing and increasing the sensor performance and frame rate by reducing the distance FIR signals need to travel.

Implementation Method 1

etching the intermediate dielectric layer by a first etch process step, wherein an etch rate of the first etch process step etching the intermediate dielectric layer is higher than an etch rate of the first etch process step etching the sacrificial metal layer, wherein the sacrificial metal layer is an etch stop layer of the first etch process step

Methodology Applied

Scientific EffectDifferential etching rate:

Implementation Method 2

employing etch solutions like TMAH and KOH, to form a thinner and more controllable dielectric layer

Methodology Applied

Scientific EffectChemical etching:

Data Source

PatentUS20250003802A1Far infrared (FIR) sensor device and manufacturing method thereof and determination method of thickness of sensor dielectric layer thereof

Publication Date: 2025.01.02 PIXART IMAGING INC

AI summary

The present invention provides a far infrared (FIR) sensor device formed on a substrate, wherein the FIR sensor device includes: a sensor region, which is formed on the substrate, and is configured to operably sense a far infrared signal; and a sensor dielectric layer, which is formed on the sensor region, wherein a thickness of the sensor dielectric layer is determined by a sacrificial metal layer.