Method of fabricating a device having a wafer with integrated processing circuits thereon

• US 5,688,698 A
• Filed: 06/07/1995
• Issued: 11/18/1997
• Est. Priority Date: 03/31/1994
• Status: Expired due to Term

• Current Assignee: Iowa State University Research Foundation Incorporated (Iowa State University)
• Original Assignee: Iowa State University Research Foundation Incorporated (Iowa State University)
• Inventors: Robinson, Douglas S., Jensen, Terrence C., Gray, Joseph N.
• Primary Examiner(s): Niebling, John
• Assistant Examiner(s): MULPURI, SAVITRI
• Application Number:
  US08/475,331
• Time in Patent Office: 895 Days
• Field of Search: 437/2, 437/3, 437/5, 250/370.09, 250/385.1, 250/374, 250/395, 257/660, 257/428, 257/444, 257/759
• US Class Current: 438/59
• CPC Class Codes: G01T 1/185 with ionisation chamber arrangements
• CPC Class Codes: G01T 1/2935 using ionisation detectors
• CPC Class Codes: H01L 31/115 Devices sensitive to very short wavelength, e.g. X-rays, gamma-rays or corpuscular radiation

Abstract

An integrated x-ray detection system includes an x-ray detector fabricated on a wafer with a housing for containing a gas. The detector has a plurality of microstrip anodes and the housing passes x-rays which partially ionize the gas thereby producing a pulse at one of the anodes. The same wafer also has a plurality of integrated active signal processing circuits which are respectively coupled to the anodes. Each active signal processing circuit receives and processes pulses from respective ones of the anodes and outputs a digital signal indicating the location and energy of x-rays detected by the detector. An isolation layer separates the x-ray detector from the active signal processing circuits.

Claims

1. A method for fabricating an integrated x-ray detection system, comprising the steps of:

integrating a plurality of active signal processing circuits into a wafer having a corresponding plurality of digital input/output contacts, said plurality of active signal processing circuits receiving pulses at a respective plurality of active signal inputs and processing said pulses to output digital information at said corresponding plurality of digital input/output contacts;

forming an isolating layer over said plurality of active signal processing circuits; and

applying a polyimide layer over said wafer having a plurality of vias, said plurality of vias exposing said plurality of digital input/output contacts; and

fabricating an x-ray detector over said wafer by metal deposition and application of insulating layers at temperatures sufficiently low such that said plurality of active signal processing circuits are not damaged, said x-ray detector having alternating potential strip and a plurality of anodes being electrically coupled to said plurality of active signal processing circuits, wherein said x-ray detector receives x-ray photons and outputs pluses at particular ones of said plurality of anodes closest to said x-ray photons, said active signal processing circuits processing said pulses and outputting digital information indicating locations and energies of said x-ray photons at said plurality of digital input/output contacts, wherein said isolating layer electrically isolates said x-ray detector from said plurality of signal processing circuits.

2. The method for fabricating an integrated x-ray detection system according to claim 1, further comprising the step of:

applying a metal shield layer between said plurality of active signal processing circuits and said x-ray detector for shielding said plurality of active signal processing circuits from electromagnetic radiation.

3. The method for fabricating an integrated x-ray detection system according to claim 2, wherein said step of applying said metal shield layer further comprises fabricating a plurality of vias in said metal shield layer corresponding to said plurality of vias in said polyimide layer.

4. The method for fabricating an integrated x-ray detection system according to claim 3, wherein said step of fabricating an x-ray detector further comprises electrically coupling said plurality of anodes to said plurality of active signal processing circuits through said further plurality of vias in said metal shield layer and through said plurality of vias in said polyimide layer.

5. The method for fabricating an integrated x-ray detection system according to claim 1, further comprising the step of:

applying a metal back potential plane between said plurality of active signal processing circuits and said x-ray detector for receiving a potential during operation to establish a control electrostatic field.

6. The method for fabricating an integrated x-ray detection system according to claim 1, further comprising the steps of:

mounting said wafer in a pressure cell; and

connecting each of said plurality of digital input/output contacts and at least one of said plurality of anodes to a corresponding pin of a plurality of pins mounted in said pressure cell.

7. The method for fabricating an integrated x-ray detection system according to claim 6, further comprising the steps of:

mounting a cathode plane in said pressure cell; and

connecting said cathode plane to a corresponding pin of said plurality of pins mounted in said pressure cell.

8. The method for fabricating an integrated x-ray detection system according to claim 6, further comprising the steps of:

evacuating said pressure cell;

backfilling said pressure cell with a detector gas; and

sealing said pressure cell.

9. The method for fabricating an integrated x-ray detection system according to claim 6, further comprising the step of:

mounting an x-ray transparent window in said pressure cell.

10. A method for fabricating a system, comprising the steps of:

providing a wafer capable of supporting integrated circuitry;

integrating a plurality of active signal processing circuits into said wafer;

fabricating a plurality of anodes on said wafer, wherein said plurality of active signal processing circuits are respectively coupled into said plurality of anodes;

arranging a plurality of potential strips alternately among said plurality of anodes;

arranging a cathode plane along said wafer;

fabricating a back potential plane on said wafer;

separating said plurality of anodes, said plurality of potential strips, and said back potential plane from said plurality of active signal processing circuits with an insulation layer; and

housing said wafer and providing a gas in a housing.

11. A method of fabricating a integrated microstrip gas proportional chamber x-ray system, comprising the steps of:

applying and processing a first polyimide resin layer on top of a passivation layer over a plurality of integrated signal processing circuits in a layer of a wafer;

depositing and lifting off metal for a shield layer on top of said first polyimide resin layer;

applying and processing a second polyimide layer on top of said shield layer;

depositing and lifting off metal for a back potential plane on top of said second polyimide layer;

applying and processing a third polyimide layer on top of said back potential plane;

depositing and lifting off metal for an anode and potential strip layer on top of said third polyimide layer automatically connecting portions of said anode and potential strip layer to said plurality of integrated signal processing circuits;

applying and processing a fifth polyimide layer on top of said anode and potential strip layer;

cutting said wafer to size and package in a pressure cell;

connecting bond wires disposed on said wafer to pins of a feedthrough passing through said pressure cell; and

evacuating and backfilling said pressure cell with a gas, and sealing said system.

12. A method of fabricating an integrated device, comprising the steps of:

applying and processing a first polyimide resin layer on top of a passivation layer over a plurality of integrated signal processing circuits in a layer of a wafer;

depositing and lifting off metal for a shield layer on top of said first polyimide resin layer;

applying and processing a second polyimide layer on top of said shield layer;

depositing and lifting off metal for a back potential plane on top of said second polyimide layer;

applying and processing a third polyimide layer on top of said back potential plane;

depositing and lifting off metal for an anode and potential strip layer on top of said third polyimide layer automatically connecting portions of said anode and potential strip layer to said plurality of integrated signal processing circuits; and

applying and processing a fifth polyimide layer on top of said anode and potential strip layer.