Temperature sensor with buffer layer

Abstract

A temperature sensor with a bandgap circuit is provided. The bandgap circuit is covered by a buffer layer of photoresist. The device is packaged in a housing. By providing the buffer layer, mechanical stress in the bandgap circuit, as it is e.g. caused by different thermal expansion coefficients of the packaging and the chip, can be reduced. This improves the accuracy of the device.

1 . A temperature sensor comprising
 a semiconductor chip,   a bandgap circuit integrated on a first surface of said semiconductor chip, and   a housing, with said semiconductor chip being covered by said housing,   wherein said temperature sensor further comprises a polymer buffer layer applied to said semiconductor chip and covering said bandgap circuit.   
     
     
         2 . The temperature sensor of  claim 1  wherein said buffer layer is a photoresist. 
     
     
         3 . The temperature sensor of  claim 2  wherein said buffer layer comprises an epoxy-based photoresist. 
     
     
         4 . The temperature sensor of  claim 3  wherein said buffer layer comprises SU-8. 
     
     
         5 . The temperature sensor of  claim 1  wherein said semiconductor chip comprises contact pads wherein said buffer layer does not cover said contact pads. 
     
     
         6 . The temperature sensor of  claim 1  further comprising an integrated sensitive structure and wherein said housing comprises an access opening extending to said integrated sensitive structure. 
     
     
         7 . The temperature sensor of  claim 6  wherein said integrated sensitive structure is a polymer film for measuring humidity. 
     
     
         8 . The temperature sensor of  claim 6  wherein said buffer layer does not extend over all of said integrated sensitive structure. 
     
     
         9 . The temperature sensor of any of  claim 1  wherein said housing covers the whole of said first surface ( 5   a ) of said chip. 
     
     
         10 . The temperature sensor of  claim 1  not comprising a MEMS device. 
     
     
         11 . A method for manufacturing a temperature sensor comprising a semiconductor chip with a band gap circuit integrated thereon, said method comprising the steps of
 applying, onto a first surface of said chip, a photoresist buffer layer,   lithographically structuring said buffer layer in order to remove part of said buffer layer but leaving said buffer layer covering said bandgap circuit,   casting a housing over said chip, with said housing covering said buffer layer.   
     
     
         12 . The method of  claim 11  wherein said chip further comprises an integrated sensitive structure, and wherein said method further comprises the steps of
 structuring said buffer layer such that at least part of said sensitive structure is uncovered,   providing a mold defining an interior space and having a section extending into said interior space,   placing said chip in said mold with said section abutting against said buffer layer,   introducing a hardening material into said mold ( 8 ,  9 ) for casting said housing over said chip,   after hardening said material at least partially, removing said section thereby forming an access opening extending to said sensitive structure.   
     
     
         13 . The method of  claim 11  comprising the steps of
 manufacturing a plurality of said chips together on a single wafer,   applying said buffer layer to said wafer,   lithographically structuring said buffer layer and, thereafter,   cutting said wafer into said chips.