The patent's assignee is
News editors obtained the following quote from the background information supplied by the inventors: "Focal Planes (FPA) consist of a compound semiconductor sensing element (i.e., detector) and a silicon readout array (i.e., CMOS read-Out Integrated Circuit (ROIC)) joined on a pixel by pixel level. In infrared sensing systems that utilize flip chip assemblies of FPAs, indium bump technology is used to bond the detector array to the ROIC. Specifically, each of the detector array and the ROIC include indium bumps formed on the surface thereof. The indium bumps on the opposing surfaces of each device may be mated and joined together in a process called hybridization.
"Although indium has proved to be a good material for these applications, layers of native oxide may be formed on the indium bumps during the fabrication of the FPA. The native oxide may prevent proper interconnection between the detector array and ROIC. As the number of pixels increases and the sizes of the pixels decreases, the formation of native oxide on indium bumps may pose significant challenges. As such, the native oxide must be removed prior to the hybridization process.
"Known techniques for removing the native oxide include a mechanical scrubbing process that includes rubbing the mated indium bumps against each other until the oxide layer breaks. This process may impose harmful mechanical stress on chip contacts and have a negative impact on yield. For example, as the surface area of the detector array increases, the force that is required to break through the oxide increases exponentially and may exceed the limits that may be withstood by commercially available devices. As a result, mechanical scrubbing may induce crystal damage and have detrimental effects on device performance. Other known techniques include the use of cleaning agents or acid etches that may also cause corrosion and/or degradation of the indium. Accordingly, known techniques for chemically or mechanically removing the native oxide layers may result in damage to FPA components and the fabrication of defective circuits."
As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "According to embodiments of the present disclosure, a method for removing oxide includes placing a sensor chip assembly having an oxide layer formed on a portion thereof within an enclosed and controlled environment. The portion of the sensor chip assembly is exposed to a reactive gas and a UV light to result in a substantial removal of the oxide layer formed on the portion of the sensor chip assembly.
"Embodiments of the disclosure may provide numerous technical advantages. For example and according to one embodiment, the native oxide layers formed on the indium bumps of a focal plane array may be removed prior to the hybridization process. In particular, the indium bumps that are used to form the interconnects may be simultaneously exposed to a combination of UV light and a reactive gas. This combination of UV light and the reactive gas may result in the substantial removal of the native oxide from the indium bumps. However, because the components of the focal plane array are not subject to mechanical forces during the removal of the native oxide, damage resulting from mechanical stress is prevented. A further technical advantage may be that the combination of UV light and the reactive gas results in removal of the native oxide layers at temperatures that are below the melting temperature of indium. Accordingly, the native oxide may be removed from a focal plane array without having a negative impact on yield or negatively effecting device performance.
"Certain embodiments of the present disclosure may include some, all, or none of the above advantages. One or more other technical advantages may be readily apparent to those skilled in the art from the figures, descriptions, and claims included herein.
BRIEF DESCRIPTION OF THE DRAWINGS
"To provide a more complete understanding of the present invention and the features and advantages thereof, reference is made to the following description taken in conjunction with the accompanying drawings, in which:
"FIG. 1A illustrates an example Focal Plane Array (FPA), according to certain embodiments of the present disclosure;
"FIG. 1B illustrates example indium bump interconnections in the example FPA of FIG. 1A, according to certain embodiments of the present disclosure;
"FIG. 2 illustrates an example system for removing native oxide from components of the FPA, according to certain embodiments of the present disclosure; and
"FIG. 3 illustrates an example method for removing native oxide from components of the FPA, according to certain embodiments of the present disclosure."
For additional information on this patent application, see: Hampp, Andreas; Harris, Sean F.; Sadighi, Talieh H.; Hanyaloglu, Bengi F. System and Method for Removing Oxide from a
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