DD245529A1

DD245529A1 - CHEMICAL SENSOR

Info

Publication number: DD245529A1
Application number: DD28654086A
Authority: DD
Inventors: Tan Pham Minh; Juergen Hueller; Werner Hoffmann
Original assignee: Akad Wissenschaften Ddr
Priority date: 1986-01-28
Filing date: 1986-01-28
Publication date: 1987-05-06

Abstract

Die Erfindung betrifft einen chemischen Sensor, bestehend aus einem chemisch sensitiven feldeffektgesteuerten Bauelement und einem chemisch nichtsensitiven feldeffektgesteuerten Bauelement, zum Nachweis von Ionen, Atomen und Molekuelen in Loesungen und Gasen. Das Ziel der Erfindung besteht in der Bereitstellung eines chemischen Sensors hoher Qualitaet. Der Erfindung liegt die Aufgabe zugrunde, einen chemischen Sensor zu schaffen, bei dem physikalisch bedingte Stoereinfluesse bei der chemischen Analyse vollstaendig kompensiert werden. Erfindungsgemaess wird die Aufgabe dadurch geloest, dass das chemisch nichtsensitive Bauelement des Sensors ohne Feldelektrode in seinem Vertikalaufbau mit dem Vertikalaufbau des chemisch sensitiven Bauelementes identisch ist.The invention relates to a chemical sensor, comprising a chemically sensitive field-effect-controlled component and a chemically non-sensitive field-effect-controlled component, for the detection of ions, atoms and molecules in solutions and gases. The object of the invention is to provide a high quality chemical sensor. The invention has for its object to provide a chemical sensor, are fully compensated in the physically induced interference influences in the chemical analysis. According to the invention, the object is achieved by virtue of the fact that the chemically non-sensitive component of the sensor without field electrode is identical in its vertical construction to the vertical structure of the chemically sensitive component.

Description

Anwendungsgebiet der ErfindungField of application of the invention

Die Erfindung betrifft einen chemischen Sensor, bestehend aus einem chemisch sensitiven feldeffektgesteuerten Bauelement und einem chemisch nichtsensitiven feldeffektgesteuerten Bauelement, zum Nachweis von Ionen, Atomen und Molekülen in Lösungen und Gasen.The invention relates to a chemical sensor consisting of a chemically sensitive field-effect-controlled component and a chemically non-sensitive field-effect-controlled component, for the detection of ions, atoms and molecules in solutions and gases.

Charakteristik der bekannten technischen LösungenCharacteristic of the known technical solutions

Bekannt sind chemisch sensitive Bauelemente, die den Feldeffekt am Halbleiter ausnutzen. Dabei wird die Ladungsträgerdichte im Oberflächenbereich eines Halbleitersubstrates moduliert durch ein von der chemischen Zusammensetzung des Meßmediums abhängendes elektrochemisches Grenzflächenpotential. Meßmedium und Halbleitersubstrat sind durch eine oder mehrere sogenannte Gateisolatorschichten sowie durch eine chemisch sensitive Membran getrennt. Entsprechend der elektronischen Anordnung zur Erfassung der Ladungsträgerdichtemodulation im Halbleitersubstrat leiten sich von diesem Wirkprinzip z. B. chemisch sensitive Feldeffekttransistoen (ChemFET, ISFET) oder chemisch gesteuerte Dioden (ICD) ab. Physikalische Einflüsse während der Messung können das chemisch verursachte Meßsignal stören und zu Drifterscheinungen in der Signalanzeige bzw. zu falscher Signalanzeige führen. Ursachen von Drifterscheinungen können u.a. sein: 1. die Injektion von elektrischen Ladungsträgern aus dem Halbleitersubstrat, oder aus der chemisch sensitiven Membran in den Gateisolator und 2. die Bewegung von Ladungsträgern im Gateisolator unter dem Einfluß des elektrischen Feldes zwischen Halbleitersubstrat und Meßmedium. Ursachen für falsche Signalanzeige sind abweichende Bedingungen — z. B. hinsichtlich Temperatur oder Lichteinwirkung — bei der Eichung des Sensorsund bei der Messung mit dem Sensor. Bekannt sind lediglich Anordnungen und Meßverfahren, die allein zur Kompensation des Temperatur- und Lichteffektes dienen. Dazu wird in einer Differenzschaltung das dem chemisch sensitiven Bauelement analoge Bauelement mit möglichst hoher elektronischer Stabilität ' als Referenzelement benutzt, d. h. die chemisch sensitive Membran wird weggelassen und das Meßmedium wird durch eine Festelektrode substituiert. Damit konnte im Falle von pH-Sensoren eine bereits vielen praktischen Anforderungen genügende Unempfindlichkeit gegenüber Temperatur- und Beleuchtungsschwankungen erreicht werden. Eine Kompensation von Drifterscheinungen, wie sie beispielsweise bei alkaliionensensitiven Festkörpermembranen in ausgeprägter Form zu beobachten sind, ist mit diesen chemischen Sensoren nicht möglich.Known are chemically sensitive components that exploit the field effect on the semiconductor. The charge carrier density in the surface region of a semiconductor substrate is modulated by an electrochemical interface potential which depends on the chemical composition of the measurement medium. Measuring medium and semiconductor substrate are separated by one or more so-called gate insulator layers and by a chemically sensitive membrane. According to the electronic arrangement for detecting the charge carrier density modulation in the semiconductor substrate derived from this principle of action z. As chemically sensitive Feldeffekttransistoen (ChemFET, ISFET) or chemically controlled diodes (ICD) from. Physical influences during the measurement can disturb the chemically caused measuring signal and lead to drift phenomena in the signal display or to wrong signal indication. Causes of drift phenomena can i.a. be: 1. the injection of electrical charge carriers from the semiconductor substrate, or from the chemically sensitive membrane in the gate insulator and 2. the movement of charge carriers in the gate insulator under the influence of the electric field between the semiconductor substrate and the measuring medium. Causes of incorrect signal display are different conditions - eg. In terms of temperature or exposure to light - in the calibration of the sensor and in the measurement with the sensor. Only arrangements and measuring methods are known which serve solely to compensate for the temperature and light effect. For this purpose, in a differential circuit, the component which is analogous to the chemically sensitive component and has the highest possible electronic stability is used as reference element, ie. H. the chemically sensitive membrane is omitted and the measuring medium is substituted by a solid electrode. In the case of pH sensors, it was thus possible to achieve insensitivity to temperature and illumination fluctuations that already satisfies many practical requirements. A compensation of drift phenomena, as they are observed in pronounced form, for example, in the case of alkali-ion-sensitive solid-state membranes, is not possible with these chemical sensors.

Ziel der ErfindungObject of the invention

Das Ziel der Erfindung besteht in der Bereitstellung eines chemischen Sensors hoher Qualität.The object of the invention is to provide a high quality chemical sensor.

Darlegung des Wesens der ErfindungExplanation of the essence of the invention

Der Erfindung liegt die Aufgabe zugrunde, einen chemischen Sensor zu schaffen, bei dem physikalisch bedingte Störeinflüsse bei der chemischen Analyse vollständig kompensiert werden.The invention has for its object to provide a chemical sensor in which physically induced interference in the chemical analysis are completely compensated.

Erfindungsgemäß wird die Aufgabe dadurch gelöst, daß das chemisch nichtsensitive Bauelement des Sensors ohne Feldelektrode in seinem Vertikalaufbau mit dem Vertikalaufbau des chemisch sensitiven Bauelementes identisch ist. Durch den identischen Aufbau beider Elemente im Bereich des Gateisolators und der chemisch sensitiven Membran lassen sich physikalisch verursachte Störungen der Meßsignalanzeige in elektronischen Differenzschaltungen vorteilhaft kompensieren. Eine solche Verfahrensweise der absichtlichen Integration einer instabilen (ionensensitiven Membran —) Schicht in ein übereine Gateelektrode gesteuertes Halbleiter-Bauelement ist bisher vollkommen unüblich gewesen, führt aber in dieser besonderen Sensoranordnung zu überraschend hoher Stabilität.According to the invention the object is achieved in that the chemically non-sensitive component of the sensor without field electrode is identical in its vertical structure with the vertical structure of the chemically sensitive device. Due to the identical construction of both elements in the region of the gate insulator and the chemically sensitive membrane, physically caused disturbances of the measurement signal display in electronic differential circuits can be advantageously compensated. Such a procedure of deliberately integrating an unstable (ion-sensitive membrane) layer into a semiconductor device controlled via a gate electrode has hitherto been completely unusual, but leads to surprisingly high stability in this particular sensor arrangement.

Diese Kompensation ist besonders vorteilhaft möglich, wenn das chemisch sensitive Bauelement und das chemisch nicht sensitive Bauelement weiterhin auch hinsichtlich ihrer Lateralstruktur identisch sind und sich örtlich in enger Nachbarschaft befinden, wobei die monolithische Integration der Hybridintegration vorzuziehen ist. Zusätzliche technologische Prozeßschritte ergeben sich daraus nicht.This compensation is particularly advantageously possible if the chemically sensitive device and the chemically non-sensitive device continue to be identical in terms of their lateral structure and are located locally in close proximity, with the monolithic integration of the hybrid integration is preferable. Additional technological process steps do not result from this.

Ausführungsbeispielembodiment

Ausgehend von p(100)-Si-Scheiben werden n-Kanaldepletion-FET's mit Si02/Si3N4-Gateisolatoren präpariert. Durch lonenbeschuß mit Kalium- und Aluminiumionen sowie nachfolgende Temperprozesse werden älkalisensitive Chem FET-Chips erhalten. Nach der Chipverkapselung weisen die so präparierten Chem FET's eine vergleichsweise größere Drift des Meßsignals auf als nicht implantierte FET-Strukturen. Eine Kompensation dieser Drift- sowie von Temperatur- und Lichteffekten — gelingt mit Hilfe von auf dem Sensorchip integrierten und gegenüber dem Meßmedium isolierten Metallgate-Strukturen, die zwischen Metallgate und Si-Substrat identische Kalium- und Aluminium-dotierte Isolatorschichten von gleicher Dicke wie die Chem FET's enthalten und die auch in ihren Lateralabmessungen mit den Chem FET-Strukturen identisch sind.Starting from p (100) Si disks, n-channel depletion FETs are prepared with SiO 2 / Si 3 N 4 gate insulators. By ion bombardment with potassium and aluminum ions and subsequent annealing processes älkalisensitive Chem FET chips are obtained. After the chip encapsulation, the thus prepared Chem FETs have a comparatively greater drift of the measurement signal than non-implanted FET structures. A compensation of these drift as well as temperature and light effects - succeeds with the help of on the sensor chip and insulated from the measuring medium metal gate structures, the metal gate and Si substrate identical potassium and aluminum-doped insulator layers of the same thickness as the Chem FET's and which are also identical in their lateral dimensions with the Chem FET structures.

Claims

Invention claim:

Chemical sensor, consisting of a chemically sensitive and a chemically non-sensitive field effect controlled device, wherein the measuring medium is substituted on the non-sensitive device by an opposite the measuring medium field electrode, characterized in that the chemically non-sensitive device without field electrode in its vertical structure with the vertical structure of the chemical sensitive component is identical.

Field of application of the invention

The invention relates to a chemical sensor consisting of a chemically sensitive field-effect-controlled component and a chemically non-sensitive field-effect-controlled component, for the detection of ions, atoms and molecules in solutions and gases.

Characteristic of the known technical solutions

Known are chemically sensitive components that exploit the field effect on the semiconductor. The charge carrier density in the surface region of a semiconductor substrate is modulated by an electrochemical interface potential which depends on the chemical composition of the measurement medium. Measuring medium and semiconductor substrate are separated by one or more so-called gate insulator layers and by a chemically sensitive membrane. According to the electronic arrangement for detecting the charge carrier density modulation in the semiconductor substrate derived from this principle of action z. As chemically sensitive Feldeffekttransistoen (ChemFET, ISFET) or chemically controlled diodes (ICD) from. Physical influences during the measurement can disturb the chemically caused measuring signal and lead to drift phenomena in the signal display or to wrong signal indication. Causes of drift phenomena can i.a. be: 1. the injection of electrical charge carriers from the semiconductor substrate, or from the chemically sensitive membrane in the gate insulator and 2. the movement of charge carriers in the gate insulator under the influence of the electric field between the semiconductor substrate and the measuring medium. Causes of incorrect signal display are different conditions - eg. B. in terms of temperature or exposure to light - in the calibration of the sensor and in the measurement with the sensor. Only arrangements and measuring methods are known which serve solely to compensate for the temperature and light effect. For this purpose, in a differential circuit, the component which is analogous to the chemically sensitive component is used as the reference element with the highest possible electronic stability, ie. H. the chemically sensitive membrane is omitted and the measuring medium is substituted by a solid electrode. Thus, in the case of pH sensors, insensitivity to temperature and illumination fluctuations already satisfying many practical requirements has been achieved. A compensation of drift phenomena, as they are observed in pronounced form, for example, in the case of alkali-ion-sensitive solid-state membranes, is not possible with these chemical sensors.

Object of the invention

The object of the invention is to provide a high quality chemical sensor.

Explanation of the essence of the invention

The invention has for its object to provide a chemical sensor in which physically induced interference in the chemical analysis are completely compensated.

According to the invention the object is achieved in that the chemically non-sensitive component of the sensor without field electrode is identical in its vertical structure with the vertical structure of the chemically sensitive device. Due to the identical construction of both elements in the region of the gate insulator and the chemically sensitive membrane, physically caused disturbances of the measurement signal display in electronic differential circuits can be advantageously compensated. Such a procedure of deliberately integrating an unstable (ion-sensitive membrane layer into a semiconductor device controlled by a gate electrode has hitherto been completely unusual, but leads to surprisingly high stability in this particular sensor arrangement.

This compensation is particularly advantageously possible if the chemically sensitive device and the chemically non-sensitive device continue to be identical in terms of their lateral structure and are located locally in close proximity, with the monolithic integration of the hybrid integration is preferable. Additional technological process steps do not result from this.

embodiment

Starting from p (100) Si disks, n-channel depletion FETs are prepared with Si0 ₂ / Si ₃ N ₄ gate insulators. Ion bombardment with potassium and aluminum ions and subsequent annealing processes gives alkali-sensitive Chem FET chips. After the chip encapsulation, the thus prepared Chem FETs have a comparatively greater drift of the measurement signal than non-implanted FET structures. A compensation of these drift as well as temperature and light effects - succeeds with the help of on the sensor chip and insulated from the measuring medium metal gate structures, the metal gate and Si substrate identical potassium and aluminum-doped insulator layers of the same thickness as the Chem FET's and which are also identical in their lateral dimensions with the Chem FET structures.