Sealed sensor device and method of manufacture thereof

Patent metadata

Field	Value
Publication number	US-2024295443-A1
Application number	US-202418592437-A
Country	US
Kind code	A1
Filing date	Feb 29, 2024
Priority date	Mar 3, 2023
Publication date	Sep 5, 2024
Grant date	—

Abstract

A sealed sensor device ( 104 ) comprising: an internal atmosphere comprising a gas pressurised to a predetermined pressure, the predetermined pressure being below atmospheric pressure when the internal atmosphere is hermetically sealed from ambient. A sensor cavity ( 214 ) is also provided having a periphery and is in fluid communication with the internal atmosphere, thereby comprising the gas and the gas having a mean free path at the predetermined pressure associated therewith. A thermopile ( 256 ) is disposed in the sensor cavity ( 214 ) for detecting a change in pressure of the internal atmosphere and detecting failure of the hermetic seal. A membrane structure ( 234 ) disposed within the cavity comprises the thermopile ( 256 ). The membrane structure ( 234 ) also comprises a heating element, and a shortest distance from substantially any point on the membrane structure ( 234 ) to the periphery of the sensor cavity ( 214 ) is less than the mean free path of the gas at the predetermined pressure.

First claim

What is claimed is:

1 . A sealed sensor device comprising:
an internal atmosphere comprising a gas pressurised to a predetermined pressure, the predetermined pressure being below atmospheric pressure when the internal atmosphere is hermetically sealed from ambient; a sensor cavity having a periphery and in fluid communication with the internal atmosphere, thereby comprising the gas and the gas having a mean free path at the predetermined pressure associated therewith; a thermopile disposed in the sensor cavity for detecting a change in pressure of the internal atmosphere and detecting failure of the hermetic seal; a membrane structure disposed within the sensor cavity and comprising the thermopile; wherein the membrane structure also comprises a heating element; and a shortest distance from substantially any point on the membrane structure to the periphery of the sensor cavity is less than the mean free path of the gas at the predetermined pressure.

2 . The device according to claim 1 , further comprising:
a sensor pixel in fluid communication with the internal atmosphere and substantially insensitive to the pressure of the internal atmosphere.

3 . The device according to claim 2 , wherein the sensor pixel comprises:
a sensor cavity, the sensor cavity comprising a getter material disposed therein.

4 . The device according to claim 1 , wherein the thermopile is blind to infrared radiation external to the cavity.

5 . The device according to claim 2 , wherein the sensor pixel is an infrared sensor pixel comprising a measurement cavity, a measurement membrane and a measurement thermopile disposed on the measurement membrane.

6 . The device according to claim 5 , wherein the sensor pixel further comprises a measurement heater element, the measurement heater element being configured to provide a heat output matched to a heat output of the heating element.

7 . The device according to claim 2 , further comprising:
a blind measurement pixel, the blind measurement pixel being in fluid communication with the internal atmosphere and disposed adjacent the sensor pixel.

8 . The device according to claim 1 , wherein the thermopile, the membrane and the cavity constitute a pressure sensor pixel, the pressure sensor pixel having a responsivity associated therewith that is dominated by a thermal conductance of the gas.

9 . The device according to claim 1 , further comprising:
a measurement circuit operably coupled to the thermopile; wherein the measurement circuit is configured to calculate a first responsivity in respect of the internal atmosphere.

10 . The device according to claim 5 , further comprising:
a measurement circuit operably coupled to the thermopile; wherein the measurement circuit is configured to calculate a first responsivity in respect of the internal atmosphere.

11 . The device according to claim 10 , wherein the measurement circuit is operably coupled to the measurement thermopile and configured to calculate a second responsivity in respect of the internal atmosphere and to calculate a relative responsivity using the first and second responsivities.

12 . The sealed sensor array comprising a plurality of measurement sensor pixels and the sealed sensor device according to claim 1 .

13 . The array according to claim 12 , wherein the plurality of measurement pixels is in fluid communication with the internal atmosphere.

14 . A method of detecting failure of a hermetic seal of a sealed pressure sensor device, the method comprising:
providing the pressure sensor device according to claim 1 ; measuring a responsivity of the pressure sensor device; and determining whether the pressure of the internal atmosphere has increased and caused the responsivity to fall below a predetermined expected responsivity value.

15 . A method of manufacturing a sealed pressure sensor device, the method comprising:
forming a sensor cavity having a periphery; forming a membrane structure comprising a thermopile within the cavity; forming a heating element adjacent a hot end of the thermopile structure; backfilling the sealed pressure sensor device with a gas to a predetermined pressure below atmospheric pressure and hermetically sealing the pressure sensor device, thereby providing an internal atmosphere; wherein the sensor cavity is in fluid communication with the internal atmosphere, thereby comprising the gas and the gas having a mean free path at the predetermined pressure associated therewith; and a shortest distance from substantially any point on the membrane to the periphery of the cavity is less than the mean free path of the gas at the predetermined pressure.

Assignees

• Melexis Technologies Nv

Inventors

• Van Thienen Jietse
• Van Buggenhout Carl
• Reekmans Stijn

Classifications

• G01L19/0092 Primary

  Pressure sensor associated with other sensors, e.g. for measuring acceleration or temperature (G01L9/025, G01L9/045, G01L9/065, G01L9/085, G01L9/105, G01L9/125, G01L19/02, G01L19/04 take precedence; measuring two or more variable G01D21/02; temperature sensors with pressure compensation G01K1/26) · CPC title

• G01L11/002

  by thermal means, e.g. hypsometer · CPC title

• B81C1/00277

  for maintaining a controlled atmosphere inside of the cavity containing the MEMS · CPC title

• B81C1/00158

  Diaphragms, membranes (manufacture process for semi-permeable inorganic membranes B01D67/0039) · CPC title

• B81B7/0096

  by heating · CPC title