There is a great desire to utilize pressure transducers in harsh environments. In such environments, apart from deleterious substances which may destroy the transducer, there are others factors which are involved. Such factors include high temperatures, such as those temperatures which are found in various engines such as automobile engines, jet engines and so on. In other applications such as the use of pressure transducers in injection molding and for other environments, extremely high temperatures are found. In regard to such operations transducers have been fabricated which operate in excess of 600° C. As one can readily ascertain it would be desirable to provide a transducer capable of operation at even higher temperatures while further being protected from deleterious environments, such as those environments containing noxious gases as well as various harsh chemicals. The prior art cognizant to those problems utilized transducers which involved the use of silicon. On the silicon wafer an oxide layer was formed. This oxide layer produced a silicon on oxide sensor. This sensor had appropriate high temperature platinum based metallization and was bonded to a glass wafer, such as a low expansion borosilicate glass. The borosilicate glass wafer had apertures which extended to the platinum based contact regions on the silicon wafer. Contact was made to the platinum region of the silicon wafer by means of a metallic frit and contact was made to the metallic frit by very short pins. This work was performed by Kulite Semiconductor Products, the assignee herein. For examples of such prior art device reference is made to U.S. Pat. No. 5,955,771, entitled “Sensor for Use in High Vibrational Applications and Methods for Fabricating the Same”. The patent issued to Anthony D. Kurtz et al. on Sep. 21, 1999 and is assigned to the assignee herein. Other examples of such sensors can be had by referring to U.S. Pat. No. 5,973,590 entitled “Ultra Thin Surface Mount Wafer Sensor Structures and Methods for Fabricating the Same” issued to Kurtz on Oct. 26, 1999. A further patent of interest is U.S. Pat. No. 6,210,989, also entitled “Ultra Thin Surface Mount Wafer Sensor Structures and Methods for Fabrication”, issued to Kurtz et al. on Apr. 3, 2001. In the prior designs, there are described extremely high temperature operation transducers, which serve to operate in very harsh environments. The upper limit of the bond which is the interconnection between the platinum metallization on the silicon sensor wafer and the conductive glass metallic frit was, in the prior designs, approximately 600° C. By bonding appropriate small diameter wires, such as platinum wires to the platinum metallization on the contacts, the upper temperature ranges could be extended to over 700° C. These sensors are state of the art sensors which exhibit extremely high temperature operation.
It is desirable to obtain an improved transducer which is capable of operating at temperatures in excess of 700° C., which transducer further provides hermetic sealing in regard to the operating environment.
USPTO Backgrounds
USPTO Backgrounds