This disclosure relates to semiconductors. In particular, this disclosure relates to layouts of semiconductor die that improve electrical isolation between seal rings and active circuits.
Integrated circuits are often implemented using semiconductors. Semiconductor integrated circuit designs can be mixed-signal active circuit designs that include both analog and digital circuits. In addition to the analog and digital circuits, a seal ring may surround the active circuit to provide mechanical support for the semiconductor and to protect against harmful environmental effects.
The innovation may be better understood with reference to the following drawings and description. In the figures, like reference numerals designate corresponding parts throughout the different views.
The discussion below makes reference to semiconductor die. Semiconductor die are typically integrated circuits that are formed in large batches on a semiconductor wafer. Integrated circuits are then cut away from the wafer as a semiconductor die. The semiconductor die may be a layered structure, where the layers provide specific electrical and physical properties to form integrated circuits with desired functionality. The integrated circuits formed on a semiconductor material may be active circuits including analog circuits or digital circuits or both. The various layers of the semiconductor die may include a substrate. In addition, the semiconductor die may include a conducting layer. The conducting layer with the substrate may have electrical and physical properties that may be beneficial for forming a circuit with the desired functionality. As the volume of circuitry increases as the die area shrinks, improved layouts may provide sufficient isolation between analog and digital circuitry. In semiconductors with a seal ring, improved layouts can be used to prevent the seal ring from allowing noise to couple between analog and digital circuitry.
In addition the active circuit 110 may be connected to the substrate and may include a digital circuit 112 and an analog circuit 114. In some examples, a semiconductor die may include regions of active circuitry, where one region of active circuitry is isolated from another region of active circuitry. Isolating regions of active circuitry includes that the circuits may not share a common electrical ground and may be electrically separated from one another by a high impedance. Isolation may be desirable when, for example, the active circuit is a mixed-signal circuit having analog circuitry and digital circuitry. Circuit designers may design such a mixed-signal circuit to provide adequate electrical isolation between digital circuitry and analog circuitry. It may be important to isolate the analog circuitry from the digital circuitry because, as one example, the analog circuitry may be noise sensitive circuitry that is sensitive to spurious emissions, noise, or other extraneous signals. For example, the digital circuitry may be noisy circuitry containing clock signals and other noise that may adversely affect the analog circuitry. To prevent the digital circuitry from adversely affecting the analog circuitry, the digital circuitry may be isolated from the analog circuitry.
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Surrounding the periphery of the active circuit 110 is an assembly isolation region 104. This may be a physical gap that separates the periphery of the active circuit 110 from the seal ring 102. The physical gap between the active circuit 110 and the seal ring may help prevent physically or electrically connecting the seal ring 102 with the active circuit 110. As one example, the width of the assembly isolation region 104 may be approximately 6 to 10 microns.
A seal ring 102 may surround the periphery of the assembly isolation region 104. The seal ring 102 may provide mechanical support and serve as a barrier to environmental penetrants, such as moisture, chemicals, or corrosive gases, from reaching the active circuit 110. The outermost periphery of the seal ring 102 may be a scribe line 118 where the individual semiconductor die is cut away from the semiconductor wafer. The seal ring 102 may serve as a mechanical barrier that helps prevent cracks from propagating into the active circuit 100 during the die cut operation.
The seal ring 102 and active circuit 110 can be physically separated by an assembly isolation region 104 that may form an air gap between seal ring 102 and active circuit 110. Additionally, to reduce current leakage between active circuit 110 and seal ring 102, a shallow trench isolation (STI) region 208 may be placed in the substrate below the assembly isolation region 104. The STI region 208 may provide a high impedance path and may reduce coupling between seal ring 102 and active circuit 110 through STI region 208. However, even with STI region 208, it is possible that seal ring 102 and active circuit 110 may be electrically connected, as shown by coupling path 210, through conducting layer 204. When seal ring 102 and active circuit 110 are electrically connected, it is possible for signals, noise, and other interference from digital circuit 112 (
While various embodiments of the invention have been described, it will be apparent that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted.