Low pass filter semiconductor structures for use in transducers for measuring low dynamic pressures in the presence of high static pressures

• US 8,307,713 B2
• Filed: 11/02/2010
• Issued: 11/13/2012
• Est. Priority Date: 04/23/2004
• Status: Active Grant

• Current Assignee: Kulite Semiconductor Products Inc
• Original Assignee: Kulite Semiconductor Products Inc
• Inventors: Kurtz, Anthony D., Shang, Tonghuo, Kochman, Boaz
• Primary Examiner(s): NOORI, MAX H
• Application Number:
  US12/938,141
• Publication Number:
  US 20110061467A1
• Time in Patent Office: 742 Days
• Field of Search: 73715-716, 737/21, 737/27
• US Class Current: 73/715
• CPC Class Codes: G01L 13/025 using diaphragms
• CPC Class Codes: G01L 19/0609 Pressure pulsation damping arrangements
• CPC Class Codes: G01L 7/08 of the flexible-diaphragm type
• CPC Class Codes: G01L 9/06 of piezo-resistive devices

Abstract

A semiconductor filter is provided to operate in conjunction with a differential pressure transducer. The filter receives a high and very low frequency static pressure attendant with a high frequency low dynamic pressure at one end, the filter operates to filter said high frequency dynamic pressure to provide only the static pressure at the other filter end. A differential transducer receives both dynamic and static pressure at one input port and receives said filtered static pressure at the other port where said transducer provides an output solely indicative of dynamic pressure. The filter in one embodiment has a series of etched channels directed from an input end to an output end. The channels are etched pores of extremely small diameter and operate to attenuate or filter the dynamic pressure. In another embodiment, a spiral tubular groove is found between a silicon wafer and a glass cover wafer, an input port of the groove receives both the static and dynamic pressure with an output port of the groove providing only static pressure. The groove filters attenuate dynamic pressure to enable the differential transducer to provide an output only indicative of dynamic pressure by cancellation of the static pressure.

Claims

1. A differential pressure transducer, comprising:

a filter adapted to receive a first pressure comprising a static pressure component and a dynamic pressure component at an input, attenuate at least the dynamic pressure component, and output a filtered second pressure at an output;

a diaphragm comprising a first surface and a second surface, wherein the first surface is adapted to receive the first pressure and the second surface is in communication with the output of the filter and adapted to receive the filtered second pressure; and

a sensor in communication with the diaphragm and adapted to measure a difference between the first pressure and the filtered second pressure.

2. The differential pressure transducer of claim 1, wherein the filter comprises a high frequency attenuator adapted to attenuate at least the dynamic pressure component.

3. The differential pressure transducer of claim 1, wherein the filter defines a plurality of etched apertures, the apertures being of a number and of a cross-section sufficient to attenuate at least the dynamic pressure component.

4. The differential pressure transducer of claim 3, wherein the cross-section is circular, comprising a diameter less than approximately 0.001 inches.

7. The differential pressure transducer of claim 1, wherein the filter is fabricated from a semiconductor wafer.

5. A differential pressure transducer, comprising:

a filter adapted to receive a first pressure comprising a static pressure component and a dynamic pressure component at an input, attenuate at least the dynamic pressure component, and output a filtered second pressure at an output;

a diaphragm comprising a first surface and a second surface, wherein the first surface is adapted to receive the first pressure and the second surface is in communication with the output of the filter and adapted to receive the filtered second pressure; and

a sensor in communication with the diaphragm and adapted to measure a difference between the first pressure and the filtered second pressure,

wherein the filter defines a helical structure, the helical structure comprising a depth and a length sufficient to attenuate at least the dynamic pressure component.

6. The differential pressure transducer of claim 5, further comprising a cover member secured to a top surface of the filter to cover the helical structure.

8. A differential pressure transducer, comprising:

a filter adapted to receive a first pressure comprising a static pressure component and a dynamic pressure component at an input, attenuate at least the dynamic pressure component, and output a filtered second pressure at an output;

a first diaphragm comprising a first surface and a second surface, wherein the first surface of the first diaphragm is adapted to receive the first pressure and the second surface of the first diaphragm is in communication with the output of the filter and adapted to receive the filtered second pressure;

a second diaphragm comprising a surface, wherein the surface of the second diaphragm is adapted to received the first pressure;

a first sensor in communication with the first diaphragm and adapted to measure a difference between the first pressure and the filtered second pressure; and

a second sensor in communication with the second diaphragm and adapted to measure the first pressure.

9. The differential pressure transducer of claim 8, wherein the filter comprises a high frequency attenuator to attenuate at least the dynamic pressure component.

10. The differential pressure transducer of claim 8, wherein the filter defines a plurality of apertures, the apertures being of a number and of a cross-section sufficient to attenuate at least the dynamic pressure component.

11. The differential pressure transducer of claim 10, wherein the cross-section is circular and of a diameter sufficient to attenuate at least the dynamic pressure component.

12. The differential pressure transducer of claim 11, wherein the diameter is less than approximately 0.001 inches.

13. The differential pressure transducer of claim 10, wherein a desired frequency attenuation value, τ

, is achieved in accordance with the following;

14. The differential pressure transducer of claim 8, wherein the filter defines a helical structure, the helical structure comprising a diameter and a length sufficient to attenuate at least the dynamic pressure component.

15. The differential pressure transducer of claim 14, wherein a desired filtering frequency, f, is achieved in accordance with the following:

16. The differential pressure transducer of claim 14, furthering comprising a cover member secured to a top surface of the filter to cover the helical structure.

17. The differential pressure transducer of claim 16, wherein the cover member is fabricated from glass.

18. The differential pressure transducer of claim 8, wherein the first diaphragm is substantially thinner than the second diaphragm.

19. The differential pressure transducer of claim 8, wherein the filter is a semiconductor wafer.

20. The differential pressure transducer of claim 19, wherein the semiconductor wafer is fabricated from silicon.

21. The differential pressure transducer of claim 20, wherein the silicon is n-type silicon.