Diamond-based chemical sensors

• US 5,362,975 A
• Filed: 07/08/1993
• Issued: 11/08/1994
• Est. Priority Date: 09/02/1992
• Status: Expired due to Term

• Current Assignee: Kobe Steel Limited
• Original Assignee: Kobe Steel Limited
• Inventors: Venkatesan, Vasudev, von Windheim, Jesko
• Primary Examiner(s): MINTEL, WILLIAM A
• Application Number:
  US08/089,170
• Time in Patent Office: 488 Days
• Field of Search: 257/414, 257/76, 257/77, 204/410, 204/411, 204/412, 204/416, 204/419, 204/431, 204/422, 204/424, 204/425, 204/426, 204/421, 422/90
• US Class Current: 257/76
• CPC Class Codes: G01N 27/129 Diode type sensors, e.g. gas sensitive Schottky diodes capacitor type sensors G01N27/227; field-effect transistor type sensors G01N27/414
• CPC Class Codes: H01L 29/1602 Diamond
• CPC Class Codes: H01L 29/45 Ohmic electrodes
• CPC Class Codes: H01L 29/872 Schottky diodes

Abstract

A chemical sensor includes a diode or a transistor fabricated in diamond. A diamond-based diode chemical sensor includes a first diamond layer of first conductivity type and a second diamond or non-diamond layer of second conductivity type. A relatively highly doped region is formed in the first diamond layer, adjacent an electrical contact to reduce the frequency dependance of the sensor'"'"'s capacitance/voltage characteristic. A diamond-based transistor sensor includes a controlling electrode such as a gate which is configured to allow a chemical external to the transistor to alter the characteristics of the transistor. Relatively highly doped regions are formed adjacent the transistor'"'"'s controlling electrodes, such as the source and drain. A heater is thermally coupled to the sensor for heating the sensor to a predetermined operating temperature. A temperature monitor is also coupled to the sensor for monitoring the sensor temperature.

Claims

1. A diamond-based chemical sensor comprising:

a first diamond layer having a first conductivity type;

a second semiconductor layer of a second conductivity type on said first diamond layer, said first and second layers forming a semiconductor junction therebetween;

at least one of said first and second layers being configured to allow a chemical external to said diamond-based chemical sensor to interact with said at least one of said first and second layers and alter an electrical characteristic of said semiconductor junction.

2. The diamond-based chemical sensor of claim 1 wherein said first diamond layer is a P-type diamond layer and wherein said second semiconductor layer is selected from the group consisting of an N-type gas sensitive second diamond layer, an N-type moisture sensitive second semiconductor layer, an N-type gas sensitive semiconducting oxide layer and an N-type carbon layer.

3. The diamond-based chemical sensor of claim 1 further comprising:

an electrical contact on said first diamond layer; and

a region of said first conductivity type in said first diamond layer, adjacent said electrical contact and which is highly doped relative to said first diamond layer, such that said electrical contact forms an ohmic contact with said region.

4. The diamond-based chemical sensor of claim 3 wherein said electrical contact is on said first diamond layer opposite said second semiconductor layer, said diamond-based chemical sensor further comprising a substrate on said first diamond layer, opposite said second semiconductor layer, and surrounding said electrical contact.

5. The diamond-based chemical sensor of claim 4 further comprising heating means in said substrate, for heating said diamond sensor above an ambient temperature.

6. The diamond-based chemical sensor of claim 5 wherein said substrate is an undoped diamond substrate.

7. The diamond-based chemical sensor of claim 1 further comprising means, thermally coupled to at least one of said first and second layers, for heating said diamond sensor above an ambient temperature.

8. The diamond-based chemical sensor of claim 7 further comprising an undoped diamond layer on said first diamond layer, opposite said second semiconductor layer, and wherein said heating means comprises a resistive heater in said undoped diamond layer.

9. The diamond-based chemical sensor of claim 7 further comprising means, thermally coupled to at least one of said first and second layers, for monitoring the temperature of said diamond-based chemical sensor.

10. The diamond-based chemical sensor of claim 1 further comprising means for confining a chemical containing liquid adjacent one of said first and second layers.

11. The diamond-based chemical sensor of claim 1 further comprising:

a substrate on said first diamond layer opposite said second semiconductor layer, said substrate having an aperture therein for exposing said first diamond layer;

an electrical contact on said first diamond layer in said aperture; and

a region of said first conductivity type in said first diamond layer, adjacent said electrical contact and which is highly doped relative to said first diamond layer, such that said electrical contact forms an ohmic contact with said region.

12. A diamond-based chemical sensor comprising:

a diamond layer;

a transistor in said diamond layer, said transistor including a controlling electrode, a first controlled electrode and a second controlled electrode;

said controlling electrode being configured to allow a chemical external to said diamond-based chemical sensor to interact with said controlling electrode and alter an electrical characteristic of said transistor.

13. The diamond-based chemical sensor of claim 12 wherein said transistor is a field effect transistor, wherein said controlling electrode is a gate electrode, wherein said first controlled electrode is a source electrode and wherein said second controlling electrode is a drain electrode.

14. The diamond-based chemical sensor of claim 13 wherein said gate electrode comprises an insulating layer on said diamond layer and a gate contact on said gate insulating layer, opposite said diamond layer, at least one of said insulating layer and said gate contact being selected to allow a chemical external to said diamond-based chemical sensor to interact therewith, and alter the characteristics of said field effect transistor.

15. The diamond-based chemical sensor of claim 12 wherein said first controlled electrode includes a first electrical contact on said diamond layer and a first region adjacent said first electrical contact and which is highly doped relative to said diamond layer, such that said first electrical contact forms a first ohmic contact with said first region;

and wherein said second controlled electrode includes a second electrical contact on said diamond layer and a second region adjacent said second electrical contact and which is highly doped relative to said diamond layer, such that said second electrical contact forms a second ohmic contact with said second region.

16. The diamond-based chemical sensor of claim 13 wherein said source, drain and gate electrodes are formed on a first face of said diamond layer.

17. The diamond-based chemical sensor of claim 13 wherein said gate electrode is formed on a first face of said diamond layer and wherein said source electrode and said drain electrode are formed on a second face of said diamond layer.

18. The diamond-based chemical sensor of claim 16 further comprising a substrate on said diamond layer, opposite said source, drain and gate electrodes.

19. The diamond-based chemical sensor of claim 18 further comprising heating means in said substrate, for heating said diamond sensor above an ambient temperature.

20. The diamond-based chemical sensor of claim 19 wherein said substrate is an undoped diamond substrate.

21. The diamond-based chemical sensor of claim 17 further comprising a substrate on said second face, and surrounding said source and drain electrodes.

22. The diamond-based chemical sensor of claim 21 further comprising heating means in said substrate, for heating said diamond sensor above an ambient temperature.

23. The diamond-based chemical sensor of claim 22 wherein said substrate is an undoped diamond substrate.

24. The diamond-based chemical sensor of claim 12 further comprising means, thermally coupled to at least one of said diamond layer, for heating said diamond-based sensor above an ambient temperature.

25. The diamond-based chemical sensor of claim 24 further comprising an undoped second diamond layer on said first diamond layer, opposite said gate electrode, and wherein said heating means comprises a resistive heater in said undoped second diamond layer.

26. The diamond-based chemical sensor of claim 24 further comprising means, thermally coupled to at least one of said first and second layers, for monitoring the temperature of said diamond-based chemical sensor.

27. The diamond-based chemical sensor of claim 12 further comprising means for confining a chemical containing liquid adjacent said gate electrode.

28. The diamond-based chemical sensor of claim 27 wherein said gate electrode is spaced apart from said insulating layer, and wherein said confining means confines said chemical containing liquid between said gate electrode and said insulating layer.

29. A diamond-based chemical sensor comprising:

a diamond layer;

a chemically sensitive layer on said diamond layer;

heating means, thermally coupled to said diamond layer, for heating said diamond-based chemical sensor above an ambient temperature; and

temperature monitoring means, thermally coupled to said diamond layer, for monitoring the temperature of said diamond-based chemical sensor.

30. The diamond-based chemical sensor of claim 29 wherein said heating means is a resistive heating means in said diamond layer.

31. The diamond-based chemical sensor of claim 29 wherein said temperature monitoring means includes at least a second diamond layer on said diamond layer.

32. The diamond-based chemical sensor of claim 30 wherein said temperature monitoring means includes at least a second diamond layer on said diamond layer.

33. The diamond-based chemical sensor of claim 29 further comprising at least one electrode, said at least one electrode in combination with at least said diamond layer and said chemically sensitive layer forming one of a junction diode, a Schottky diode, a capacitor and a transistor.