Semiconductor devices are commonly found in modern electronic products. Semiconductor devices vary in the number and density of electrical components. Semiconductor devices perform a wide range of functions such as analog and digital signal processing, sensors, transmitting and receiving electromagnetic signals, controlling electronic devices, power management, and audio/video signal processing. Discrete semiconductor devices generally contain one type of electrical component, e.g., light emitting diode (LED), small signal transistor, resistor, capacitor, inductor, diodes, rectifiers, thyristors, and power metal-oxide-semiconductor field-effect transistor (MOSFET). Integrated semiconductor devices typically contain hundreds to millions of electrical components. Examples of integrated semiconductor devices include microcontrollers, application specific integrated circuits (ASIC), power conversion, standard logic, amplifiers, clock management, memory, interface circuits, and other signal processing circuits.
A semiconductor wafer includes a base substrate material and plurality of semiconductor die formed on an active surface of the wafer separated by a saw street. FIG. 1a shows a conventional semiconductor wafer 10 with base substrate material 12, active surface 14, and back surface 16. Conductive vias 18 are formed through semiconductor wafer 10 for electrical interconnect. Conductive vias 18 are created prior to wafer thinning and may be made of tungsten or other hard metal, sometimes with an oxide material between the conductive via and base substrate material 12 for isolation.
Many applications require the semiconductor die to be reduced in height or thickness to minimize the size of the semiconductor package. FIG. 1b shows a grinding operation with grinding wheel 20 removing a portion of base substrate material 12 from back surface 16 of semiconductor wafer 10 and reducing the thickness of the semiconductor wafer. Grinding wheel 20 operates on a constant feed rate of the grinding wheel into the grinding surface. Grinding wheel 20 typically goes through some portion of base substrate material 12 before reaching conductive vias 18. The grinding operation leaves particles 22 from base substrate material 12, conductive vias 18, and grinding wheel 20, and other contaminants on the grinding surface. The particles and contaminants 22 become lodged between grinding wheel teeth 21, and between grinding wheel 20 and base substrate material 12. The grinding wheel rotation with the various particles and contaminants 22 form surface cracks, gouges, and other damage 24 in final post-grinding surface 26, as shown in FIG. 1c. In particular, the tungsten conductive vias 18 are brittle and break apart and become lodged between the grinding wheel and grinding surface, leaving the cracks, gouges, scratches, and other damage 24 in final post-grinding surface 26. The damage to final surface 26 may cause semiconductor wafer 10 to fail inspection. In addition, the cracks, gouges, and other damage 24 in final post-grinding surface 26 may create stress concentration points which can lead to wafer and die breakage and reduce production yield.
USPTO Backgrounds
USPTO Backgrounds