Method for manufacturing a pressure-measuring device equipped with a resonating element

• US 6,207,470 B1
• Filed: 11/06/1998
• Issued: 03/27/2001
• Est. Priority Date: 09/18/1997
• Status: Expired due to Fees

• Current Assignee: ABB Kent-Taylor Limited
• Original Assignee: ABB Kent-Taylor Limited
• Inventors: De Bortoli, Eros
• Primary Examiner(s): Picardat, Kevin M.
• Application Number:
  US09/186,647
• Time in Patent Office: 872 Days
• Field of Search: 438/50, 438/51, 438/52, 438/53, 737/17--28
• US Class Current: 438/53
• CPC Class Codes: G01L 9/0019 of a semiconductive element

Abstract

Method for manufacturing a pressure-measuring device comprising a diaphragm of semiconductor material having a resonating element fixed thereto, said diaphragm being exposed to the pressure of a process fluid, wherein it comprises the following phases:

i) machining a multilayer semiconductor material to obtain a diaphragm having on the upper side a resonating element, an excitation element and a detection element for measuring the pressure applied to said diaphragm;

ii) machining a semiconductor material having one or more layers to obtain a support having a pressure port for the flow of the process fluid;

iii) making a bond between the lower side of said diaphragm and the upper side of said support.

Claims

1. A method for manufacturing a pressure-measuring device comprising a diaphragm of semiconductor material having a resonating element fixed thereto, said diaphragm being exposed to the pressure of a process fluid, comprising the following phases, whatever the order:

i) machining a multilayer semiconductor material to obtain a diaphragm having on the upper side a resonating element, an excitation element and a detection element for measuring the pressure applied to said diaphragm;

ii) machining a semiconductor material having one or more layers to obtain a support having a pressure port for the flow of the process fluid;

iii) making a bond between the lower side of said diaphragm and the upper side of said support.

2. The method of claim 1, further comprising the following phase:

iv) machining the lower part of the diaphragm to obtain a protective structure against overrange pressure pulses.

3. The method of claim 1, wherein the multilayer semiconductor material used in phase i) is a three-layer semiconductor material having a top layer, an intermediate layer and a bottom layer.

4. The method of claim 3, wherein the resonating element, the excitation element and related connections to the pad contacts and the detection elements and related connections to the pad contacts are created on the top layer of the three-layer semiconductor material.

5. The method of claim 3, wherein the bottom layer is machined to obtain a protective structure against overrange pressure pulses.

6. The method of claim 4, wherein the phase i) comprises the following steps:

a) machining the top layer to selectively remove portions of said top layer and define thereon the structures of the resonating element, the excitation element and the detection element;

b) creating metallized portions on said top layer in order to provide electrical connections to said excitation element and detection element; and

c) selectively removing portions of the intermediate layer to create a cavity in said intermediate layer allowing free vibration of the resonating element.

7. The method of claim 6, wherein said step a) comprises:

depositing a layer of protective material on the surface of top layer;

depositing a layer of photosensitive material over said layer of protective material;

selectively removing portions of said photosensitive material using photolithografic techniques to create a mask defining the profile of the resonating element, excitation element and the detection element;

selectively removing the unmasked portions of said protective layer;

removing said mask of photosensitive material;

removing portions of said top layer not masked by said protective layer creating openings reaching said intermediate layer;

masking with a layer of protective material the portion of the top layer where the resonator has to be positioned; and

removing said layer of protective material on the surface of the top layer.

8. The method of claim 7, wherein the removal of said mask of photosensitive material is carried out after making the openings in said top layer.

9. The method of claim 6, wherein said step b) comprises:

covering the top layer with a layer of protective material;

selectively removing portions of said layer of protective material using photolithographic techniques to create a mask defining thereon the path of said electrical connections;

selectively removing the unmasked portions of the top layer creating cavities for the seatings of said electrical connections;

removing of said protective material;

masking the portion of the top layer, where said resonator has to be positioned, using a layer of protective material;

selectively doping the unmasked portions of the top layer;

removing said protective layer from the surface of the top layer;

covering the top layer with one or more layers of metallic material;

masking the portion of said layer of metallic material matching the seatings of said electrical connections;

removing the unmasked portions of said layer of metallic material; and

removing the protective material.

10. The method of claim 6, wherein said step b) comprises:

covering the top layer with a layer of protective material;

selectively removing portions of said layer of protective material using photolithographic techniques to create a mask defining thereon the path of said electrical connections;

selectively removing the unmasked portions of the top layer creating cavities for the seatings of said electrical connections;

removing said protective material;

masking the portion of the top layer, where said resonator has to be positioned, using a layer of protective material;

selectively doping the unmasked portions of the top layer;

masking with a layer of protective material the portion of the top layer not occupied by the seatings of said electrical connections;

depositing metallic material into said seatings; and

removing said protective material.

11. The method of claim 6, wherein said step c) comprises:

cleaning the top layer of the three-layer material;

covering the top layer with a layer of protective material creating a mask with openings matching the area where the resonating element is positioned;

selectively removing the intermediate layer of said three-layer semiconductor material creating a cavity in said intermediate layer allowing free vibration of the resonating element;

removing said protective material; and

rinsing said three-layer semiconductor material using cleaning solutions.

12. The method of claim 6, wherein the phase i) comprises the steps described in claim 6 with the following order:

step a), step b) and step c).

13. The method of claim 6, wherein said phase i) comprises the steps described in claim 6 in the following order:

step a), step c) and step b).

14. The method of claim 5, wherein the machining of the bottom layer comprises:

depositing a layer of protective material on the bottom layer of said three-layer semiconductor material;

selectively removing said protective material to create a mask defining the contour of said protection structure; and

selectively removing the unmasked portion of the bottom layer of said three-layer semiconductor material; and

removing said protective material.

15. The method of claim 1, further comprising the following phase:

v) making a bond on the lower side of said support and a further support.

16. The method of claim 1, further comprising the following phase:

vi) making a bond between the upper side of said diaphragm and a protective layer.

17. The method of claim 16, wherein said phase vi) comprises:

depositing an insulating layer on the portion of the top layer not comprising the resonating element;

lapping said insulating layer;

bonding said insulating layer and said protective layer.

18. The method of claim 16, wherein said bond of a protective layer seals the cavity in the intermediate layer of said three-layer semiconductor material allowing free vibration of the resonating element in high vacuum.

19. Pressure measuring device obtained according to the method of claim 1.