Electronic devices having an inorganic film

#The increased utilization of electronic devices, in an ever widening array of diverse technologies, such as computers, automotive, medical, and household appliances has led to the operation of many of these electronic devices in harsh environments such as high humidity, high temperatures, or combinations thereof. In addition, there is also an increased demand for reliability. The continued improvement in performance and component density, of semiconductor devices, has led to a rapidly growing demand for packaging technologies to yield packaged devices having reduced cost, improved reliability and performance, increased interconnect density, and small package size.

#Typically, a semiconductor device includes a semiconductor die with bond pads formed on its surface, and bond wires that electrically couple the bond pads with lead fingers on a lead frame. The semiconductor die is attached to the lead frame before bonding, and typically a polymer is dispensed or molded around the die, the bond wires, and the majority of the lead frame to encapsulate the device. The device is often electrically coupled with a printed circuit board (PCB) by soldering leads of the lead frame to pads on the PCB. The utilization of some encapsulating polymers can lead to performance degradation and damage from electrical shorting, corrosion, or cracking due to moisture. This tends to be an even greater problem when the electronic device must operate in a harsh environment.

#Hermetic sealing using a metal or ceramic package provides an increased level of protection, however, the manufacturing process is complex and results in a more expensive package of increased size. Another method that can be utilized is sealing a semiconductor chip's active circuitry at the wafer stage, by applying a passivation coating over the active circuitry on the wafer. However, this process may still lead to a non-hermetically sealed device, by causing damage to the ceramic like coating in the vicinity of the bond pads in subsequent processing, thereby permitting corrosion to deleteriously affect chip reliability and life. Further, this process does not provide protection to the bond pads and electrical interconnections. In addition, these technologies do not lend themselves to all applications. For instance, over the past decade, substantial developments have been made in the micromanipulation of fluids, in fields such as electronic printing technology using inkjet printers. The ability to maintain reliable electrical interconnections in such products has become more difficult as the corrosive nature of the fluids increases.

#FIG. 1 is a cross-sectional view of an electronic device according to an embodiment of the present invention;

#FIG. 2a is a perspective view of an electronic device according to an embodiment of the present invention;

#FIG. 2b is a cross-sectional view of an electronic device according to an embodiment of the present invention;

#Referring to FIG. 1, an embodiment of the present invention is shown in a simplified cross-sectional view. In this embodiment, electronic device 100 includes inorganic layer 128 providing moisture and corrosion protection to electrical interconnection 120 and electrical connector 118. Substrate 110 is disposed over base 130, and includes dielectric layer 114 that is formed over at least a portion of substrate 110, providing electrical isolation for one or more electrical connectors 118. Preferably substrate 110 also includes one or more transistors or other logic devices (not shown) formed on substrate 110. Electrical interconnection 120 electrically couples electrical connector 118 to carrier lead 140 providing signal as well as power connections to electronic device 100. Inorganic film 128 is formed over polymer 124 that encloses electrical interconnection 120 and electrical connector 118. The combination of inorganic film 128 and polymer 124 provides protection against environmental degradation as well as mechanical support to reduce damage of electrical interconnection 120 and electrical connector 118.

#Preferably, substrate 110 is a silicon integrated circuit, however, materials such as germanium, gallium arsenide, amorphous silicon, aluminum oxide, polysilicon, and other substrates that support active and passive devices can also be utilized. With reference to FIG. 1 substrate 110 is preferably manufactured using a silicon wafer. Using conventional semiconductor processing equipment, transistors as well as other logic devices required for electronic device 100 are formed in substrate 110. The particular structure of the transistors is not relevant to the present invention, however some type of solid state electronic device is preferably present, such as, metal oxide field effect transistors (MOSFET), bipolar junction transistors (BJT). Although FIG. 1 shows only one electrical connector 118, typically there are a plurality of electrical connectors positioned near opposed edges of substrate 110 that are connected to the transistors or other logic devices. The present invention as described herein is applicable irrespective of the electrical connector position on the substrate.

#In this embodiment base 130 may be formed from metal, ceramic, or plastic materials or some combinations thereof. Materials suitable for base 130 include, metals, metal alloys, liquid crystal polymers, polyphenylene oxide, epoxy resins, polyimide resins, FR4 resins, aluminum oxide, and glass to name a few. For example, base 130 may be a metal lead frame, a ceramic die carrier, or a flexible circuit. In one embodiment, base 130 is a metal lead frame. Substrate 110 has an active surface 112 on which electronic components and electrical circuits are formed and an opposing surface 131. Although FIG. 1 shows substrate 110 coupled directly to base 130 a spacer layer (not shown) may also be utilized, depending on the particular application of electronic device 100. The spacer or compliant layer provides stress relaxation related to the difference in the thermal expansion of the substrate and substrate carrier materials, thereby providing a wider choice of materials.