Thermal isolation microstructure

• US 5,534,111 A
• Filed: 02/29/1988
• Issued: 07/09/1996
• Est. Priority Date: 02/29/1988
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Hocker, G. Benjamin, Johnson, Robert G., Holmen, James O.
• Primary Examiner(s): Nelson, Peter A.
• Application Number:
  US07/172,118
• Time in Patent Office: 3,053 Days
• Field of Search: 156/345, 156/643, 156/646, 156/655, 156/668, 204/192.32, 357/15, 357/16, 342/5, 257/16
• US Class Current: 216/15
• CPC Class Codes: B81B 2203/0109 Bridges
• CPC Class Codes: B81C 1/0069 Thermal properties, e.g. improve thermal insulation
• CPC Class Codes: G01J 5/02 Constructional details
• CPC Class Codes: G01J 5/023 Particular leg structure or construction or shape; Nanotubes
• CPC Class Codes: G01J 5/04 Casings
• CPC Class Codes: G01J 5/046 Materials; Selection of thermal materials
• CPC Class Codes: H10N 19/00 Integrated devices, or assemblies of multiple devices, comprising at least one thermoelectric or thermomagnetic element covered by groups H10N10/00 - H10N15/00

Abstract

A thermal isolation microstructure fabricated by a process which allows the ultra thinning of support legs for the microdetector.

Claims

1. A process for fabricating a thermal isolation microbridge used as an infrared radiation detection element, the steps comprising:

providing a monocrystalline silicon substrate wafer having a planar surface;

depositing a thin film silicon nitride layer on said surface;

depositing and delineating a thin film layer of temperature-sensitive, electrically-resistive material for a sensor and electrode leadout on said silicon nitride layer;

depositing a further thin film silicon nitride layer over said material and said first silicon nitride layer;

depositing a thin absorber layer over the last deposited silicon nitride in the area of the sensor;

depositing and delineating a thin film photo-lithographic mask;

making a plurality of silicon nitride cuts outlining the elongated legs containing the electrode leadout and the support tabs for the microbridge;

dry etching the legs and the support tabs to remove about 1/2 the thickness of silicon nitride;

introducing anisotropic etchant through said cuts and anisotropically etching away silicon to form a pit beneath the microbridge sensor and legs;

removing the thin film photolithographic mask with a liquid etch;

etching with a plasma dry etch the exposed silicon nitride on said elongated legs to remove the Si₃ N₄ down to the electrode leadouts, which act as an etch stop to the dry etch, the plasma dry etch also removing the Si₃ N₄ of the leg extending laterally of the electrode.

2. The process according to claim 1 and directly following said step "depositing a thin absorber layer over the lest deposited silicon nitride in the area of the sensor", further comprising the step:

covering said absorber layer with a thin film layer of silicon nitride.

3. The process according to claim 1 in which said temperature sensitive electrically-resistive material is nickel-iron.

4. The process according to claim 1 in which said absorber layer is a thin film layer of nickel-iron.

5. The process according to claim 1 in which said photolithographic mask is chrome metal.

6. A process for fabricating a thermal isolation microbridge used as an infrared radiation detection element, the steps comprising:

providing a monocrystalline silicon substrate wafer having a planar surface

depositing a thin film silicon nitride layer on said surface;

depositing and delineating a thin film layer of nickel-iron for a sensor and leadout on said silicon nitride layer;

depositing a further thin film silicon nitride layer over said material and said first silicon nitride layer;

depositing a thin film absorber layer of nickel-iron over the last deposited silicon nitride in the area of the nickel-iron sensor;

covering said absorber layer with a thin film layer of silicon nitride;

depositing and delineating a thin film chrome metal mask;

making a plurality of silicon nitride cuts outlining the elongated legs containing the nickel-iron leadout and the support tabs for the microbridge;

dry etching the legs and the support tabs to remove about 1/2 the thickness of silicon nitride;

introducing anisotropic etchant through said cuts and anisotropically etching away silicon to form a pit beneath the microbridge sensor and legs;

removing the thin film chrome layer with a liquid etch;

etching with a plasma dry etch the exposed silicon nitride on said elongated legs to remove the Si₃ N₄ down to the NiFe leadout, which NiFe acts as an etch stop to the dry etch, the plasma dry etch also removing the Si₃ N₄ of the leg extending laterally of the NiFe.