Thin-film transistor used as heating element for microreaction chamber

• US 6,504,226 B1
• Filed: 12/20/2001
• Issued: 01/07/2003
• Est. Priority Date: 12/20/2001
• Status: Expired due to Term

• Current Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Bryant, Frank R.
• Primary Examiner(s): Nelms, David
• Assistant Examiner(s): LE, DUNG ANH
• Application Number:
  US10/028,849
• Time in Patent Office: 383 Days
• Field of Search: 257/77, 257/510, 257/519, 257/637, 257/647, 257/648, 257/640, 257/641
• US Class Current: 257/510
• CPC Class Codes: B01J 19/0093 Microreactors, e.g. miniaturised or microfabricated reactors laboratory containers with capillary fluid transport in microfabricated channels or chambers B01L3/5027
• CPC Class Codes: B01J 2219/00783 Laminate assemblies, i.e. the reactor comprising a stack of plates
• CPC Class Codes: B01J 2219/00828 Silicon wafers or plates
• CPC Class Codes: B01J 2219/00853 Employing electrode arrangements
• CPC Class Codes: B01J 2219/00873 Heat exchange
• CPC Class Codes: B01L 3/5027 by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip B01L3/5023 takes precedence; micromixers B01F33/30; microreactors for synthesis B01J19/0093; microcapillary devices in general B81B1/00
• CPC Class Codes: B41J 2/14129 Layer structure
• CPC Class Codes: F24V 99/00 Subject matter not provided for in other main groups of this subclass
• CPC Class Codes: G01N 2035/00376 Conductive heating, e.g. heated plates
• CPC Class Codes: G01N 25/4826 concerning the heating or cooling arrangements heating apparatus for chemical or physical laboratory apparatus in general B01L7/00
• CPC Class Codes: H01L 29/66765 Lateral single gate single channel transistors with inverted structure, i.e. the channel layer is formed after the gate
• CPC Class Codes: H01L 29/78624 the source and the drain regions being asymmetrical
• CPC Class Codes: H01L 29/78696 characterised by the structure of the channel, e.g. multichannel, transverse or longitudinal shape, length or width, doping structure, or the overlap or alignment between the channel and the gate, the source or the drain, or the contacting structure of the channel H01L29/78612 takes precedence; transistors having a drain offset region or a lightly doped drain [LDD] H01L29/78621
• CPC Class Codes: H05B 2203/013 Heaters using resistive films or coatings
• CPC Class Codes: H05B 2203/017 Manufacturing methods or apparatus for heaters
• CPC Class Codes: H05B 3/26 heating conductor mounted on insulating base for transparent areas H05B3/84, H05B3/86

Abstract

The thin film transistor formed of polycrystalline silicon is positioned adjacent a heat reaction chamber. The gate electrode for the transistor is formed within a silicon substrate and a gate dielectric is positioned over the gate electrode. A pass transistor is coupled to the gate electrode, the pass transistor having a source/drain region in the same semiconductor substrate and positioned adjacent to the gate electrode of the thin film heating transistor. When the pass transistor is enabled, a voltage is applied to the gate electrode which causes the current to flow from the drain to the source of the thin film transistor. The current flow passes through a highly resistive region which generates heat that is transmitted to the heat reaction chamber.

Claims

1. A thin-film, semiconductor heater assembly, comprising:

a semiconductor substrate;

a gate electrode formed within the substrate;

an gate dielectric layer positioned over the gate electrode and overlying the semiconductor substrate;

a channel member having a resistive region with a selected resistivity positioned over the gate dielectric layer;

a source region positioned adjacent the channel region;

a drain region positioned adjacent the channel region;

a current carrying conductor coupled to the drain for carrying current from the drain, through the channel and to the source in response to the gate electrode applying an electric field to the channel region; and

a heat responsive reaction chamber positioned adjacent the channel region.

2. The heater assembly according to claim 1, further including:

an electrical insulating member positioned over the channel member and in between the channel member and the heat responsive reaction chamber.

3. The heater assembly according to claim 2 wherein the electrical insulating member is comprised of a material having high heat conductivity.

4. The heater assembly according to claim 2 wherein the electrical insulating member has a shape and size to rapidly conduct heat from the channel member to the heat responsive reaction chamber.

5. The heater assembly according to claim 1 wherein the resistivity is selected to provide a selected heat response for selected current flow through the channel member.

6. The heater assembly according to claim 1 wherein the resistive region is positioned within the channel region, directly over the gate electrode and has a smaller length than the channel region.

7. The heater assembly according to claim 1 wherein the resistive region is partially positioned within the channel region and partially positioned within the drain region, the resistive region being longer in length than the channel region.

8. The heater assembly according to claim 1 wherein the location and size of the resistive region are selected to provide a directed heating response within the reaction chamber at a selected location.

9. The heater assembly according to claim 1 wherein the resistive region is longer in length than the gate electrode.

10. The heater assembly according to claim 1, further including:

a cover positioned over the heat responsive reaction chamber, the cover having a selected size and material to modify the heating response within the reaction chamber.

11. The heater assembly according to claim 1, further including:

an enable transistor coupled to the gate electrode, the enable transistor having a source and a drain positioned within the same semiconductor substrate as the heater assembly gate electrode.

12. The heater assembly according to claim 11 further including:

a voltage source coupled to the enable transistor, the voltage source providing a selected voltage on the gate electrode to create an electrical field within the channel member via the enable transistor.

13. The heater assembly of claim 11 in which the enable transistor further includes:

a channel region in the same semiconductor substrate as the heater assembly gate electrode;

a second gate dielectric positioned over channel region;

a polysilicon gate electrode positioned over the second gate dielectric.

14. The heater assembly of claim 12 in which the heater assembly gate dielectric is the same contiguous layer as the second gate dielectric.

15. The heater assembly of claim 12 in which the heater assembly gate dielectric is a different layer than the second gate dielectric, having a different thickness.

16. A method of making a semiconductor heater assembly comprising:

forming electrically insulating regions within a semiconductor substrate;

forming a gate electrode within the semiconductor substrate;

forming a gate dielectric over the gate electrode and located between the insulating regions;

forming a layer of polycrystalline silicon overlying the insulating regions and the gate dielectric;

doping source and drain regions within the polycrystalline silicon layer to have a selected low resistivity to obtain a thin-film trnasistor;

forming a heat reponsive reaction chamber over the resistive region.