Protective Layer for ChemFET Ion Detection
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Solution Overview
Problem
Ion semiconductor DNA sequencing methods face challenges in detecting hydrogen ions due to surface contamination of semiconductor chips, which complicates manufacturing and affects sequencing accuracy.
Innovation Solution
A protective layer is applied over the chemically-sensitive field effect transistors (chemFETs) to prevent surface contamination, comprising materials like polymers, noble metals, or metal oxides, which can be removed before nucleic acid sequencing to ensure clean sensing surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is applied over chemFETs to prevent surface contamination, then reliability of ion detection is improved, but device complexity increases due to additional manufacturing steps
Solution Approach 1:
A protective layer is deposited over the chemFETs before final assembly to prevent surface contamination during manufacturing and storage. This preliminary protective measure ensures clean sensing surfaces are maintained until the moment of use, resolving the contradiction by prioritizing reliability through advance protection despite added manufacturing complexity
Solution Approach 2:
The protective layer is designed to be removable just before sequencing operations. After serving its protective function during manufacturing and storage, the layer is discarded to expose the sensing surface for actual use. This temporary protection approach maintains reliability while allowing the system to return to its functional state
2Measurement precision
If surface contamination is prevented during manufacturing, then measurement precision of hydrogen ion detection is improved, but manufacturing precision requirements increase
Solution Approach 1:
A protective layer acts as an intermediary between the chemFET sensing surface and the contaminated manufacturing environment. This intermediate barrier prevents direct contact between contaminants and the sensitive sensing surface, thereby maintaining measurement precision without requiring extremely stringent manufacturing precision controls
3Reliability
If the protective layer is removed before sequencing, then purity of sensing surface is improved, but loss of time occurs during the removal process
Solution Approach 1:
The protective layer is designed with specific chemical properties that allow for rapid removal through parameter changes - specifically, using chemically selective etchants or solvents that quickly dissolve or detach the protective material without damaging the underlying chemFET structure. This minimizes the time penalty while ensuring complete removal for optimal sensing surface purity
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 protective layer effectively prevents contamination, enhancing the reliability and accuracy of ion detection during nucleic acid sequencing by maintaining chip surface cleanliness throughout the manufacturing and sequencing processes.
Implementation Method 1
A protective layer is applied over the chemically-sensitive field effect transistors (chemFETs) to prevent surface contamination
Implementation Method 2
The release of a hydrogen ion during incorporation causes a change in the pH of the solution in the microwell. That change in the pH of the solution can be detected/measured by the ISFET or chemFET sensor
Implementation Method 3
etching the dielectric layer and the protective layer to form cavities corresponding to sensing surfaces of the chemFETs
Data Source
AI summary
A method of manufacturing a sensor, the method including forming an array of chemically-sensitive field effect transistors (chemFETs), depositing a dielectric layer over the chemFETs in the array, depositing a protective layer over the dielectric layer, etching the dielectric layer and the protective layer to form cavities corresponding to sensing surfaces of the chemFETs, and removing the protective layer. The method further includes, etching the dielectric layer and the protective layer together to form cavities corresponding to sensing surfaces of the chemFETs. The protective layer is at least one of a polymer, photoresist material, noble metal, copper oxide, and zinc oxide. The protective protective layer is removed using at least one of sodium hydroxide, organic solvent, aqua regia, ammonium carbonate, hydrochloric acid, acetic acid, and phosphoric acid.