Patent Publication Number: US-2004051166-A1

Title: Shielding line system for an integrated circuit

Description:
FIELD  
       [0001] This invention generally relates to integrated circuits having conductive channels or lines. More particularly, this invention relates to integrated circuits having shielding lines to reduce crosstalk and other transmission line effects.  
       BACKGROUND  
       [0002] An integrated circuit or other semiconductor device typically has many resistors, capacitors, transistors, and/or other electrical components fabricated on a semiconductor wafer. The electrical components are interconnected by numerous conductive channels or lines formed by conductive material between the components. The conductive lines act like wires carrying electrical and other signals between the components. With a suitable configuration of electrical components and conductive lines, an integrated circuit can function as an amplifier, a microprocessor, a memory device or the like. The memory device may be a dynamic random access memory (DRAM), another type of random access memory (RAM), or another type of memory.  
       [0003] DRAM and other memory devices usually have an array of memory cells formed on the semiconductor wafer. Each memory cell has a configuration of transistors and capacitors that is repeated throughout the array. The memory cells store data as electronically-charged points using the capacitors and transistors. Typically, the memory cells receive new electronic charges to refresh or prevent the capacitors from losing any electrical charge.  
       [0004] DRAM devices have numerous conductive channels for interconnecting transistors and capacitors with each memory cell and for interconnecting memory cells and other electronic components on the semiconductor wafer. As with other integrated circuits, the conductive channels or lines are close together. Recent designs have closer conductive channels or lines to reduce the size of the DRAM device or integrated circuit.  
       [0005] In many DRAM and integrated circuit designs, there can be crosstalk and other transmission line effects between the conductive channels or lines. Crosstalk is the interference caused when signals in adjacent or nearby conductive channels or lines are superimposed on each other. The conductive channels or lines form an electromagnetic (inductive) or an electrostatic (capacitive) coupling, which causes the signals or voltages on one conductive channel to jump to other conductive channels. Crosstalk can be reduced by increasing the distance between the conductive channels or lines or by using shielding lines between the conductive channels or lines.  
       [0006]FIG. 1 is a block diagram of a shielding line system according to the prior art. Shielding lines are disposed between signal and critical lines. Signal lines usually carry data and control signals in a DRAM device. Critical lines usually carry timing signals or reference voltages. The shielding lines have constant potential, which creates an electromagnetic field between the signal and critical lines. However, crosstalk occurs when the interference between the signal and critical lines passes over or around the shielding lines and their respective electromagnetic field.  
       SUMMARY  
       [0007] This invention provides a shielding line system that reduces or eliminates crosstalk between conductive lines in an integrated circuit. The shielding line system radially encloses a conductive line with a shielding line conduit and an electromagnetic field.  
       [0008] The shielding line system may have a first conductive line, one or more second conductive lines, and a shielding line conduit. The shielding line conduit is disposed between the first and second conductive lines. The shielding line conduit radially encloses the first conductive line. An electromagnetic field radially encloses the first conductive line.  
       [0009] The shielding line system also may have a first conductive line, a second conductive line, a third conductive line, first and second side shielding lines, and top and bottom shielding lines. The first side shielding line is disposed between the first and second conductive lines. The second side shielding line is disposed between the first and third conductive lines. The top shielding line is connected to the first and second shielding lines. The bottom shielding line is connected to the first and second shielding lines. As a result, an electromagnetic field radially encloses the first conductive line when potential is applied to the interconnected shielding lines.  
       [0010] Other systems, methods, features, and advantages of the invention will be or will become apparent to one skilled in the art upon examination of the following figures and detailed description. All such additional systems, methods, features, and advantages are intended to be included within this description, within the scope of the invention, and protected by the accompanying claims. 
     
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
     [0011] The invention may be better understood with reference to the following figures and detailed description. The components in the figures are not necessarily to scale, emphasis being placed upon illustrating the principles of the invention. Moreover, like reference numerals in the figures designate corresponding parts throughout the different views.  
     [0012]FIG. 1 is a block diagram of a shielding line system according to the prior art.  
     [0013]FIG. 2 is a schematic diagram of a shielding line system for an integrated circuit according to an embodiment.  
     [0014]FIG. 3 is a schematic diagram of a shielding line system for an integrated circuit according to another embodiment.  
     [0015]FIG. 4 is a flowchart of an embodiment of a method for shielding a conductive line in an integrated circuit. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0016]FIG. 2 is a schematic diagram of a shielding line system  100  for an integrated circuit according to an embodiment. The shielding line system  100  includes a critical line  102 , signal lines  106  and  108 , and a shielding line conduit  110 . There may be one or other multiples of signal lines. Critical line  102  carries timing signals or reference voltages. Signal lines  106  and  108  carry data, control signals, or other signals. The critical and signal lines may carry other signals and the same or similar signals for the integrated circuit. The shielding line conduit  110  is disposed between the critical line  102  and signal lines  106  and  108 . The shielding line conduit  110  reduces or eliminates crosstalk between the critical line  102  and signal lines  106  and  108 . The integrated circuit may be a memory device such as a dynamic random access memory (DRAM) or another semiconductor device. While particular configurations have been shown and described, other configurations may be used including those with fewer or additional components such as just critical lines shielded from external interference.  
     [0017] Critical line  102 , signal lines  106  and  108 , and shielding line conduit  110  are conductive channels or lines, which are combined with electrical components (resistors, capacitors, transistors, and like) to create an integrated circuit. The electrical components and conductive channels are formed on a semiconductor wafer using a photolithographic or similar process for manufacturing integrated circuits. The semiconductor wafer usually is a single crystal silicon wafer; however germanium, gallium arsenide, and other semiconductor materials may be used. To fabricate the integrated circuit, the various materials comprising the finished circuit are layered onto the semiconductor wafer. These materials include conductive materials, dielectrics, and the like. After each layer, photoresist and etching processes are used to form the layer into the desired configuration. A photoresist material is applied to portions of the layer that remain on the semiconductor wafer. The etching process removes portions of the layer not protected by the photoresist material. The photoresist material is removed and another layer is formed on the semiconductor wafer. The conductive channels are separated by dielectric materials.  
     [0018] The shielding line conduit  110  has a top shielding line  112 , a bottom shielding line  114 , a first side shielding line  116 , and a second side shielding line  118 . The top shielding line  112  is connected to the first side shielding line  116  by a first line contact or via  126 . The top shielding line  112  is connected to the second side shielding line  118  by a second line contact or via  124 . The bottom shielding line  114  is connected to the first side shielding line  116  by a third line contact or via  120 . The bottom shielding line  114  is connected to the second side shielding line  118  by a fourth line contact or via  122 .  
     [0019] The top and bottom shielding lines  112  and  114  are on opposite sides of the critical line  102 . The first and second side shielding lines  116  and  118  are on opposite sides of critical line  102 . The first and second side shielding lines  116  and  118  also are adjacent to critical line  102 . The shielding lines  112 ,  114 ,  116 , and  118  and critical line  102  may have one or more lines or other components between any or all of them.  
     [0020] The shielding line conduit  110  forms a rectangular shape that radially encloses critical line  102 . The shielding line conduit  110  may extend longitudinally along a portion or the entire length of critical line  102 . Shielding line conduit  110  has constant potential, thus creating an electromagnetic field that also radially encloses critical line  102 . The electromagnetic field may extend longitudinally along the entire length or a portion of the critical line  102 . The electromagnetic field may be continuous (present whenever the integrated circuit is operating) or may be intermittent (present only when critical line  102  is carrying a signal). The radial enclosure of the critical line  102  by the shielding line conduit  110  and the electromagnetic field reduces or eliminates any crosstalk between critical line  102  and signal lines  106  and  108 . Shielding line conduit  110  may have other shapes and have other electromagnetic fields that reduce or eliminate cross talk. While the arrangement of the critical line  102  and shielding line conduit  110  has been described, they may have other arrangements as long as the mechanical and/or electromagnetic properties to reduce or eliminate crosstalk are achieved.  
     [0021]FIG. 3 is a schematic diagram of a shielding line system  200  for an integrated circuit according to another embodiment. The shielding line system  200  includes a signal line  206 , critical lines  202  and  204 , and a shielding line conduit  210 . There may be one or other multiples of critical lines. Critical lines  202  and  204 , signal line  206 , and shielding line conduit  210  are conductive channels or lines as previously discussed. Critical lines  202  and  204  carry timing signals or reference voltages. Signal line  206  carries data and control signals. The critical and signal lines may carry other signals and the same or similar signals for the integrated circuit. The shielding line conduit  210  is disposed between the critical lines  202  and  204  and signal line  206 . The shielding line conduit  210  reduces or eliminates crosstalk between the critical lines  202  and  204  and signal line  206 . The integrated circuit may be a memory device such as a dynamic random access memory (DRAM) or another semiconductor device. While particular configurations have been shown and described, other configurations may be used including those with fewer or additional components.  
     [0022] The shielding line conduit  210  has a top shielding line  212 , a bottom shielding line  214 , a first side shielding line  216 , and a second side shielding line  218 . The top shielding line  212  is connected to the first side shielding line  216  by a first line contact or via  226 . The top shielding line  212  is connected to the second side shielding line  218  by a second line contact or via  224 . The bottom shielding line  214  is connected to the first side shielding line  216  by a third line contact or via  220 . The bottom shielding line  214  is connected to the second side shielding line  218  by a fourth line contact or via  222 .  
     [0023] The top and bottom shielding lines  212  and  214  are on opposite sides of the signal line  206 . The first and second side shielding lines  216  and  218  are on opposite sides of signal line  206 . The first and second side shielding lines  216  and  218  also are adjacent to signal line  206 . The shielding lines  212 ,  214 ,  216 , and  218  and signal line  206  may have one or more lines or other components between any or all of them.  
     [0024] The shielding line conduit  210  forms a rectangular shape that radially encloses signal line  206 . The shielding line conduit  210  may extend longitudinally along a portion or the entire length signal line  206 . Shielding line conduit  210  has constant potential, thus creating an electromagnetic field that also radially encloses signal line  206 . The electromagnetic field may extend longitudinally along the entire length or a portion of the signal line  206 . The electromagnetic field may be continuous (present whenever the integrated circuit is operating) or may be intermittent (present only when signal line  206  is carrying a signal). The radial enclosure of the signal line  206  by the electromagnetic field and the shielding line conduit  210  reduces or eliminates any crosstalk between critical lines  202  and  204  and signal line  206 . Shielding line conduit  210  may have other shapes and have other electromagnetic fields that reduce or eliminate cross talk. While the arrangement of signal line  206  and shielding line conduit  210  has been described, they may have other arrangements as long as the mechanical and/or electromagnetic properties to reduce or eliminate crosstalk are achieved.  
     [0025]FIG. 4 is a flowchart of an embodiment of a method for shielding a conductive line in an integrated circuit. A conductive line is radially enclosed  332  by a shielding line conduit as previously discussed. The conductive line may be a signal line or a critical line. The shielding line conduit may have top and bottom shield lines, first and second shield lines, and side line vias. The shielding line conduit may have another configuration and/or arrangement including fewer or additional components. The shielding line conduit may extend a portion or the entire length of the conductive line. The conductive line is radially enclosed  334  by an electromagnetic field as previously discussed. The electromagnetic field may extend the entire length or a portion of the conductive line. The electromagnetic field may be continuous (present whenever the integrated circuit is operating) or may be intermittent (present only when the conductive line is carrying a signal).  
     [0026] Various embodiments of the invention have been described and illustrated. However, the description and illustrations are by way of example only. Other embodiments and implementations are possible within the scope of this invention and will be apparent to those of ordinary skill in the art. Therefore, the invention is not limited to the specific details, representative embodiments, and illustrated examples in this description. Accordingly, the invention is not to be restricted except in light as necessitated by the accompanying claims and their equivalents.