# US 5,350,701 A · Process for producing a surface gate of an integrated electro-chemical sensor, consisting of a field-effect transistor sensitive to alkaline-earth species and sensor obtained

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- Number: US 5,350,701 A
- Document ID: US5350701A
- Status: Granted
- Kind: A
- Application number: 07/988,912
- Filed: 1993-05-06
- Granted: 1994-09-27
- Earliest claimed: 1990-09-14
- Assignees: Ecole Centrale De Lyon
- Inventors: Nicole Jaffrezic-Renault; Jean-Marc Chovelon; Hubert Perrot; Pierre Le Perchec; Yves Chevalier
- Web page: https://patentgrep.com/patent/US5350701A

## CPC

- G01N 27/414: Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

A process for producing a surface gate comprising a selective membrane for an integrated chemical sensor comprising a field effect transistor, and the integrated chemical sensor thus produced, wherein the surface gate is particularly sensitive to alkaline-earth species, and more particularly, sensitive to the calcium ion. The process comprises forming grafts on the surface gate, and making the grafts operative utilizing phosphonate-based, iono-sensitive molecules.

## Claims

### Claim 1

A process for making a surface gate of an integrated electrochemical sensor comprising a field-effect transistor having two doped zones comprising a source and a drain and a median surface on which a surface gate is to be formed, wherein the process comprises the steps of:
subjecting the median surface to a treatment of hydroxylation in order to obtain 10.sup.14 to 10.sup.15 OH sites per cm.sup.2,
washing and drying the surface, and further comprising the steps of:
grafting the median surface with a grafting product in order to produce grafts on some or all sites on the median surface,
preparing phosphonate-based iono-sensitive molecules,
making operative one or more of the grafts using the iono-sensitive molecules.

### Claim 2 (depends on 1)

The process according to claim 1, wherein the grafting product is selected from pure silane, aminosilane, alkoxysilane, halosilane, of general formula: ##STR5## in which: --R.sub.1 is either:
--(CH.sub.3).sub.2 --N--,
--CH.sub.3 --O--,
--CH.sub.3 --CH.sub.2 --O--,
--Cl--,
--R'.sub.1 is either:
--CH.sub.3 --,
--CH.sub.3 --O--,
--CH.sub.3 --CH.sub.2 --O--,
--R.sub.2 is in all cases:
--Cl.

### Claim 3 (depends on 1)

The process according to claim 1, wherein the step of grafting the surface comprises the following steps:
hydroxylation,
degassing in vacuo, and
reaction by immersion in the presence of the grafting product.

### Claim 4 (depends on 3)

The process according to claim 3, wherein the degassing step comprises heating the surface to a temperature range of 120.degree. to 160.degree. C. for a duration of 1 to 5 hours in vacuo.

### Claim 5 (depends on 3)

The process according to claim 3, wherein the grafting product is based on phosphonate, the surface is subjected to heating to a temperature range of 60.degree. to 80.degree. C. for a duration of 15 to 48 hours in an enclosure at ambient pressure in the presence of a neutral gas, and the surface is washed and dried.

### Claim 6 (depends on 1)

The process according to claim 1, wherein the iono-sensitive molecules are characterized by a group (CH.sub.3).sub.2 --N--, a spacer group --(CH.sub.2).sub.n, and a group containing phosphorus-oxygen bonds and selected from the group consisting of phosphonate, ethylphosphonate and phosphate.

### Claim 7 (depends on 1)

The process according to claim 1, wherein the iono-sensitive molecules are selected from the group consisting of ##STR6##

### Claim 8 (depends on 1)

The process according to claim 1, characterized in that the step of making operative one or more of the grafts comprises forming a mixture comprising 0.5 g of iono-sensitive molecules in 40 ml of methanol; and contacting the surface with the mixture, for 1 to 5 days, to a reflux temperature.

### Claim 9 (depends on 8)

The process according to claim 8, characterized in that from 100 to 500 mg of sodium iodide is added to mixture comprising the iono-sensitive molecules and methanol.

### Claim 10 (depends on 1)

An integrated electromechanical sensor comprising a field-effect transistor having a surface gate made in accordance with the process of claim 1, and characterized in that its pH response curve shows two zones of inflexion between pH 3 and 4 and pH 7 and 8, characteristic of the presence of phosphonate-based iono-sensitive molecules.