METHOD OF PRODUCING AN INTEGRATED REFERENCE PRESSURE SENSOR ELEMENT

• US 20030110865A1
• Filed: 08/20/1999
• Published: 06/19/2003
• Est. Priority Date: 02/20/1997
• Status: Active Grant

• Current Assignee: MKS Instruments Incorporated
• Original Assignee: MKS Instruments Incorporated
• Inventors: JOHSSON, STAFFAN
• Granted Patent: US 6,735,845 B2
• Time in Patent Office: Days
• US Class Current: 73/718
• CPC Class Codes: G01L 9/0044 Constructional details of non-semiconductive diaphragms
• CPC Class Codes: G01L 9/0072 using variations in capacitance
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass
• CPC Class Codes: Y10T 29/43 Electric condenser making
• CPC Class Codes: Y10T 29/49007 Indicating transducer
• CPC Class Codes: Y10T 29/49083 Heater type

Abstract

A compact pressure sensor of capacitive type includes a pressure sensor housing assembly, which contains a reference cavity in which a high vacuum exists and which has a minimum volume. The pressure sensor housing comprises an upper base plate, a thinner shielding plate and a movable diaphragm, and a small cavity formed between the shielding plate and movable diaphragm. A narrow channel extends from the cavity to the outside and they form a reference cavity. At the mouth of the channel a recess is provided containing an elastically mounted getter body which is capable of being thermally activated, so that a portion of the surface of the getter body is a wall surface in the reference cavity. A closing lid having a low projecting profile is placed in a gastight way in the recess and engages the getter body. When simultaneously closing the reference cavity and activating the getter body, the lid is attached to a heating probe at a distance from the sensor housing and the getter body is placed in the recess. The whole assembly is placed in a vacuum chamber and the temperature is then increased to the temperature, at which the getter starts to be activated, and thereupon the probe is moved to a position in which the closing lid is in contact with the getter body but not tightly to the sensor housing. The temperature of the probe is increased in order to melt the joint material on the lid, heat then being conducted through the lid to the getter body, and thereupon the lid is tightly attached to the housing and is fixed in this position.

Claims

1. A method of producing a pressure sensor comprising a pressure sensor house assembly which contains a reference cavity, in which a vacuum exists, and furthermore comprising a getter capable of being thermally activated, characterized in that the getter is activated by conducting heat from an exterior heated body, which is made to come in contact with a getter and is then removed.

2. A method according to claim 1, characterized in that the contact of the heated exterior body with the getter is elastic.

3. A method according to any of claims 1-2, characterized in that during the time period, when the body is engaged with the getter, the reference cavity is closed.

4. A method according to any of claims 1-3, for a pressure sensor comprising a connection to the outside which can be closed, characterized in the air is pumped out of the reference cavity and that then the connection is closed by a lid and the getter is then activated by conducting beat through the lid from the exterior body.

5. A method according to any of claims 1-4, characterized in

that a pressure sensor house is produced of substantially ceramic material having a reference cavity arranged therein and a single closing channel from a main portion of the reference cavity to a mouth at the outside,

that air is pumped out of a room containing the pressure sensor house, so that a vacuum is obtained therein and in the reference cavity,

that a closing lid having a glass joint material which is arranged thereon and is capable of being thermally activated, is heated and placed over the mouth of the closing channel, and

that the closing lid then is allowed to cool.

6. A method according to claim 5, characterized in that the joint material is arranged in a dotted pattern on the closing lid in order to allow that gases released in the heating process in the contact of the closing lid with the pressure sensor house can be let out from a small slot which is then formed at the surface of the joint.

7. A method of producing a pressure sensor comprising a pressure sensor housing assembly containing a reference cavity, in which a vacuum exists, and furthermore comprising a getter which is capable of being thermally activated and a connection to the outside which can be closed, characterized in that air is pumped out of the reference cavity and that then the connection is closed by a lid and the getter then is activated by conducting heat from the lid.

8. A method of producing a pressure sensor comprising a pressure sensor house assembly containing a reference cavity, in which a vacuum exists, characterized in

that a pressure sensor house is produced including a reference cavity, which comprises an opening or a channel from the main portion of the cavity to the outside,

that a getter capable of being thermally activated is placed, so that at least a portion of the surface of the getter forms a wall surface of the reference cavity,

that a closing lid is attached to a body at a distance from a pressure sensor housing, so that gas can freely pass between the body comprising the lid attached thereto and the pressure sensor house,

that the temperature of the body and then of the closing lid is increased to the temperature, at which the getter is activated,

that the body is then moved to such a position, that the closing lid is applied tightly to the house and is attached in this position to the house and that then the body and/or the lid conducts heat to the getter, and

that the body is then released from the closing lid.

9. A method according to claim 8, characterized in that before increasing the temperature of the body, that air is pumped away to become substantially a vacuum, which is located in a room surrounding the body having the lid attached thereto and the pressure sensor house including the getter.

10. A method according to any of claims 8-9, characterized in that when increasing the temperature of the body the temperature of the body is increased to a temperature at which the getter start to be activated to a substantial extent and that the body is then maintained at this temperature during such a long time period, that a substantial activation of the getter is produced.

11. A method according to claim 10, characterized in that directly before moving the body to the position, in which the closing lid is applied tightly to the house, the temperature of hew body is increased further during a short period of time in order to produce a final activation of the getter.

12. A method according to any of claims 8-11, characterized in that for attaching the closing lid to the house a sealing adhesive which is capable of being thermally activated is applied to the closing lid in order to seal and attach the closing lid to the pressure sensor house, when the body is moved to the position in which the closing lid is applied tightly to the house.

13. A method of producing a pressure sensor including a pressure sensor house assembly comprising a reference cavity, in which a vacuum exists, characterized in

that a pressure sensor house is produced of substantially ceramic material having a reference cavity arranged herein and a single closing channel extending from a main portion of the reference cavity up to a mouth at an outside of the pressure sensor house,

that air is pumped out of a room containing the pressure sensor house, so that a vacuum is obtained therein and in the reference cavity,

that a closing lid including a joint material, which is arranged thereon and can be thermally activated, is heated and placed on top of the mouth of the closing channel, and

that the closing lid is then allowed to cool.

14. A method according to claim 13, characterized in that the joint material is arranged in a dotted pattern on the closing lid in order to allow that gases released in the heating procedure in the engagement of the closing lid with the pressure sensor house can be let out from a narrow slot which is then formed at the surface of the joint.

15. A pressure sensor comprising a pressure sensor house assembly of substantially ceramic material containing a reference cavity, in which a vacuum exists, characterized by a single closing channel, which is a part of the reference cavity and extends from a main portion thereof to a single closing lid, by means of which the reference cavity is closed.

16. A pressure sensor according to claim 15, characterized in that a getter body is located in the reference cavity or forms a wall surface thereof.

17. A pressure sensor according to any of claims 15-16, characterized in that the closing lid has the shape of a plug, which with only a low plate shaped portion projects from the rest of the pressure sensor house assembly.

18. A pressure sensor according to any of claims 15-17, characterized in that the pressure sensor comprises thin plates which are stacked on top of each other and are attached to each other and that the closing lid is arranged at the surface of an exterior plate, the closing lid being so arranged that a portion thereof projecting above the surface has a thickness at most substantially equal to the thickness of the thinnest plate, whereby the pressure sensor also has the shape of a thin plate including at most only a very low projecting portion for closing he reference cavity.

19. A pressure sensor according to any of claims 15-18, characterized in the closing lid has the shape of a whole body including no holes arranged therein.

20. A pressure sensor according to any of claim 15-19, characterized in that the closing lid is attached and scaled to the rest of the pressure sensor house assembly by means of at least one dotted joint.

21. A pressure sensor according to any of claims 15-20, characterized in that a getter body which is thermally activated is located in the channel in contact with the closing lid.

22. A pressure sensor according to claim 21, characterized by a spring, which is arranged to act on the getter body, whereby it is elastically arranged in a portion of the reference cavity, so tat it is free to move and can absorb heat stresses.

23. A pressure sensor according to claim 22, characterized in that the spring is arranged, so that it presses the getter body against an interior side of the closing lid.

24. A pressure sensor including a pressure sensor house assembly containing a reference cavity, in which a vacuum exists, and further comprising a thermally activated getter body, characterized by a spring, which is arranged to act on the getter body, whereby the getter body is elastically arranged in a portion of the reference cavity, so that it is free to move and can absorb heat stresses.

25. A pressure sensor according to claim 24, characterized in that the getter body is arranged in a closed channel, which extends from a main portion of the reference cavity.

26. A pressure sensor according to claim 25, characterized by a closing lid, which is mounted as a closure of the channel and which is in contact with the getter body.