Method of manufacturing miniaturized components of chemical and biological detection sensors that employ ion-selective membranes, and supports for such components

• US 5,393,401 A
• Filed: 01/07/1993
• Issued: 02/28/1995
• Est. Priority Date: 05/10/1991
• Status: Expired due to Fees

• Current Assignee: Meinhard Knoll
• Original Assignee: Meinhard Knoll
• Inventors: Knoll, Meinhard
• Primary Examiner(s): Niebling, John
• Assistant Examiner(s): Bell, Bruce F.
• Application Number:
  US07/966,148
• Time in Patent Office: 782 Days
• Field of Search: 204/403, 204/416, 204/418, 204/419, 204/414, 204/433, 204/435, 427/534, 427/581, 427/289, 427/290, 427/307
• US Class Current: 204/403.06
• CPC Class Codes: G01N 27/414 Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS

Abstract

The invention relates to a process for producing miniaturized chemical and biological sensor elements with ion-selective membranes. To simplify production in the micro range, an aperture (5,6) starting from the front (3) and tapering toward the back (4) is made in a thin silicon substrate (1) so that the front and back are interconnected. A liquid with which the ion-selective membrane is formed is poured into the containment (2) thus formed. Vertical ISFETs may also be made on the above principle.

Claims

1. In a method of manufacturing supports for miniaturized components of sensors that detect chemicals and biologicals by means of ion-selective membranes, said method comprising the following steps:

(a) producing a thin substrate of a single-crystal silicon having a front side and a back side and having one of a (100) and a (110)-orientation in its plane,

(b) etching said substrate anisotropically from the front side to the back side, thereby forming an opening that tapers from the front side to the back side in the form of a truncated pyramid, when etched in a silicon substrate having a (100)-orientation, and an opening with two parallel as well as perpendicular walls and two sloping walls when etched in a silicon substrate having a (110)-orientation, said opening forming a containment;

the improvement wherein

(1) at least one electrode is applied against one of the internal walls of the opening;

(2) a liquid solution is introduced into the containment from the front side, said solution comprising one of a polymer in a solvent which is allowed to evaporate and a solution which is allowed to solidify into an hydrogel; and

(3) leaving the solidified polymer or hydrogel as ion-selective membrane within the containment and with contact with the electrode.

2. Method as in claim 1, wherein the containment is anisotropically etched in the form of a truncated pyramid into a (100)-oriented silicon substrate.

3. Method as in claim 1, wherein the containment is anisotropically etched into a (110)-oriented silicon substrate, generating an opening with two parallel and perpendicular walls and two sloping walls.

4. Method as in claim 1, wherein the back of the silicon substrate is provided with a layer of resist before being anisotropically etched, wherein the containment is then etched through from the front to the resist, and wherein the layer of resist is then etched through to the back of the substrate where the opening narrows.

5. Method as in claim 1, further comprising the step of providing the containment, at least in the vicinity of its opening on the front and of its opening on the back along with the opening'"'"'s internal walls, with a continuous layer of silicon dioxide.

6. Method as in claim 5, further comprising the step of silanizing the layer of silicon dioxide that constitutes the phase interface with the ion-selective membrane.

7. Method as in claim 5, further comprising the step of providing a second layer in addition to the layer of silicon dioxide on the internal walls of the containment.

8. Method as in claim 7, wherein said second layer is Si₃ N₄.

9. Method as in claim 5, wherein said layer of silicone dioxide is provided by a process selected from the group consisting of thermal oxidation, chemical-vapor deposition and sol-to-gel condensation.

10. Method as in claim 1, wherein the electrode is applied by a process selected from the group consisting of vapor deposition and sputtering and is a lithographically structured film.

11. Method as in claim 10, wherein said structured film is formed of a material selected from the group consisting of silver, silver chloride over silver, platinum and gold.

12. Method as in claim 10, wherein the filling opening and the capillary channel are blanketed with a protective coating.

13. Method as in claim 1, wherein the liquid introducing step includes the step of introducing a solution, containing a polymer in a solvent, into the containment and allowing the solvent to evaporate, leaving the solidified polymer of liquid membrane.

14. Method as in claim 13, wherein the liquid membrane produced is polyvinyl chloride.

15. Method as in claim 1, wherein the liquid introducing step includes the steps of introducing a solution into the containment and allowing the solution to solidify into an electrochemically relevant layer.

16. Method as in claim 15, wherein the electrochemically relevant layer is a hydrogel.

17. Method as in claim 1, wherein the liquid introducing step includes the steps of introducing a solution into the containment and allowing the solution to solidify into a membrane with a biochemically active material embedded in it.

18. Method as in claim 17, wherein the biologically active material is an enzyme.

19. Method as in claim 1, further comprising the steps of applying a solidified interior-electrolyte layer over the ion-selective membrane in the containment and connecting the same to a diversion electrode.

20. Method as in claim 19, wherein the solidified interior-electrolyte layer is connected to a gate contact.

21. Method as in claim 20, wherein the gate contact is formed by a layer of silver chloride over silver.

22. Method as in claim 1, wherein the containment communicates through a capillary channel with a filling opening and wherein the membrane liquid is a solvent that is introduced into the filling opening in a solvent atmosphere.

23. Method as in claim 22, wherein the silicon substrate forms a plurality of silicon chips each providing at least one containment, and wherein all the containments in adjacent chips are supplied with liquid from one filling opening and the chips are then isolated.

24. Method as in claim 23, wherein the chips are arranged in a single wafer, and are supplied with liquid from one filling opening on the wafer.

25. Method as in claim 1, wherein the front opening into the containment is blanketed with a protective coating.

26. Method as in claim 1, wherein the sensor component is accommodated in a housing and sealed off with a protective coating and wherein the active surfaces of the membrane are in contact with the fluid being analyzed at the rear of the chip.

27. A component for a sensor that detects chemicals and biologicals, manufactured by the method according to claim 1.

28. A method of manufacturing a vertical ISFET on a thin silicon substrate having a front side and a back side comprising the steps of (1) providing the front side of the silicon substrate with superimposed positive and negative layers constituting a source, drain and gate;

(2) producing in the substrate an opening that tapers from the front side to the back side and provides communication and containment therebetween, and (3) introducing a-liquid into the containment opening to form an ion-selective membrane, wherein the containment is anisotropically etched, sloping together through the layers, and accommodates the ion-selective membrane, and wherein walls of the containment are provided with a dielectric layer.

29. Method as in claim 28, wherein the containment is etched through from the back of the substrate and wherein the small opening from the containment is positioned along with the active surface of the membrane at the front of the substrate.

30. Method as in claim 28, further comprising the steps of applying a solidified interior-electrolyte layer over the ion-selective membrane in the containment and connecting it to a diversion electrode.

31. Method as in claim 30, wherein said solidified interior-electrolyte layer is connected to the gate contact.

32. Method as in claim 31, wherein the gate contact is formed by a layer of silver chloride over silver.

33. Method as in claim 28, wherein the dielectric layer is a material selected from the group consisting of SiO₂ and Si₃ N₄ over SiO₂.