Integrated infrared sensors with optical elements and methods

Abstract

An infrared (IR) radiation sensor device ( 27 ) includes an integrated circuit radiation sensor chip ( 1 A) including first ( 7 ) and second ( 8 ) temperature-sensitive elements connected within a dielectric stack ( 3 ) of the chip, the first temperature-sensitive element ( 7 ) being more thermally insulated from a substrate ( 2 ) than the second temperature-sensitive element ( 8 ). Bonding pads ( 28 A) on the chip ( 1 ) are coupled to the first and second temperature-sensitive elements. Bump conductors ( 28 ) are bonded to the bonding pads ( 28 A), respectively, for physically and electrically connecting the radiation sensor chip ( 1 ) to corresponding mounting conductors ( 23 A). A diffractive optical element ( 21,22,23,31,32 or 34 ) is integrated with a back surface ( 25 ) of the radiation sensor chip ( 1 ) to direct IR radiation toward the first temperature-sensitive element ( 7 ).

1 . An infrared (IR) radiation sensor device comprising:
 an integrated circuit radiation sensor chip including first and second temperature-sensitive elements in a dielectric stack of the radiation sensor chip, the first temperature-sensitive element being more thermally insulated from a substrate of the radiation sensor chip than the second temperature-sensitive element;   a plurality of bonding pads on the radiation sensor chip coupled to the first and second temperature-sensitive elements;   a plurality of bump conductors bonded to the bonding pads, respectively, for physically and electrically connecting the radiation sensor chip to corresponding mounting conductors, respectively; and   an diffractive optical element integrated with a back surface of the radiation sensor chip.   
     
     
         2 . The radiation sensor device of  claim 1  wherein the optical element is a diffractive optical element, and wherein the first temperature-sensitive element is insulated from the substrate by means of a cavity between the substrate and the dielectric stack. 
     
     
         3 . The radiation sensor device of  claim 2  wherein the diffractive optical element includes a Fresnel lens focused on a portion of the dielectric layer bounding the cavity. 
     
     
         4 . The radiation sensor device of  claim 3  wherein the Fresnel lens is a binary Fresnel lens formed of concentric regions etched into the back surface of the radiation sensor chip. 
     
     
         5 . The radiation sensor device of  claim 3  wherein the Fresnel lens is a binary Fresnel lens formed of concentric rings of infrared-opaque material deposited on the back surface of the radiation sensor chip. 
     
     
         6 . The radiation sensor device of  claim 2  wherein the diffractive optical element includes a diffraction grating. 
     
     
         7 . The radiation sensor device of  claim 6  wherein the diffraction grating is formed of a plurality of elongated parallel rectangular regions etched into the back surface of the radiation sensor chip. 
     
     
         8 . The radiation sensor device of  claim 3  wherein concentric regions of the Fresnel lens are circular. 
     
     
         9 . The radiation sensor device of  claim 3  wherein the Fresnel lens includes at least approximately 100 concentric regions. 
     
     
         10 . The radiation sensor device of  claim 5  wherein the infrared-opaque material is composed of metal. 
     
     
         11 . The radiation sensor device of  claim 2  wherein the first and second temperature-sensitive elements include first and second thermocouple groups, respectively, connected in series to form a thermopile, and wherein the dielectric stack is a semiconductor process dielectric stack including a plurality of SiO 2  sublayers and various polysilicon traces, titanium nitride traces, tungsten contacts, and aluminum metallization traces between the various sublayers patterned to provide the first and second thermocouple groups connected in series to form the thermopile. 
     
     
         12 . The radiation sensor device of  claim 11  including CMOS circuitry coupled between first and second terminals of the thermopile to receive and operate on a thermoelectric voltage generated by the thermopile in response to infrared (IR) radiation received by the radiation sensor chip, the CMOS circuitry also being coupled to the bonding pads. 
     
     
         13 . The radiation sensor device of  claim 12  wherein the substrate is composed of silicon to pass infrared radiation to the thermopile and block visible radiation, and further including a passivation layer disposed on the dielectric stack and a plurality of generally circular etchant openings located between the various traces and extending through the passivation layer and the dielectric layer to the cavity for introducing silicon etchant to produce the cavity by etching the silicon substrate. 
     
     
         14 . The radiation sensor device of  claim 1  wherein the first and second temperature-sensitive elements include first and second resistive devices, respectively. 
     
     
         15 . A method for making a radiation sensor device, comprising:
 providing first and second temperature-sensitive elements connected in a dielectric stack of a radiation sensor chip, and thermally insulating the first temperature-sensitive element from a substrate of the radiation sensor chip;   forming a plurality of bonding pads on the radiation sensor chip, the bonding pads being coupled to the first and second temperature-sensitive elements;   bonding the bonding pads to a plurality of corresponding mounting conductors, respectively; and   integrating an optical element with a back surface of the radiation sensor chip.   
     
     
         16 . The method of  claim 14  wherein the optical element is a refractive optical element, the method including insulating the first temperature-sensitive element from the substrate by etching a cavity in the substrate between the first temperature-sensitive element and the substrate. 
     
     
         17 . The method of  claim 16  wherein step (d) includes forming a Fresnel lens on a back surface of the radiation sensor chip so that the Fresnel lens is focused on a portion of the dielectric layer bounding the cavity. 
     
     
         18 . The method of  claim 16  wherein step (d) includes forming a diffraction grating on a back surface of the radiation sensor chip so that the diffraction grating directs infrared radiation to the first temperature-sensitive element. 
     
     
         19 . The method of  claim 17  including forming the Fresnel lens as a binary Fresnel lens by etching a plurality of concentric regions into the back surface of the radiation sensor chip. 
     
     
         20 . A infrared radiation sensor device, comprising:
 a radiation sensor chip including first and second temperature-sensitive elements connected in a dielectric stack of a radiation sensor chip, and thermally insulating the first temperature-sensitive element from a substrate of the radiation sensor chip;   means for thermally insulating the first temperature-sensitive element from a substrate of the radiation sensor chip;   bump conductor means bonded to a plurality of bonding pads coupled to the thermopile, respectively, for physically and electrically connecting the radiation sensor chip to corresponding mounting conductors; and   optical means integrated with a back surface of the radiation sensor chip for directing incoming infrared radiation to a portion of the dielectric stack bounding the thermally insulating means.