Interconnection structures are widely used in semiconductor integrated circuits to connect semiconductor devices or circuit parts to each other or to external pads. Memory cells of memory arrays such as volatile or non-volatile memory arrays use interconnection structures to connect the memory cells of the array to support circuits such as sense amplifiers or decoders, for example. Future technologies aim for smaller minimum feature sizes to increase the storage density and to reduce the cost of semiconductor chips. When scaling semiconductor devices of integrated circuits to smaller minimum feature sizes, interconnection structures also have to be scaled down. Scaling of interconnection structures such as bitlines and bitline contacts to smaller minimum feature sizes is crucial and challenging in view of feasibility of lithography, taper of contact plugs, contact fills and short circuits between neighboring contact plugs, for example.
Features and advantages of embodiments of the invention will be apparent from the following detailed description. The drawings are not necessarily to scale. Emphasis is placed up on illustrating the principles. Like reference numerals refer to like elements throughout the drawings.
In the following detailed description reference is made to the accompanying drawings, which form a part thereof and in which specific embodiments are shown by way of illustration. In this regard, directional terminology such as “top,” “bottom,” “front,” “back,” etc., is used with reference to the orientation of the figures being described. Since components of embodiments may be positioned in a number of different orientations, the directional terminology is used for purposes of illustration only and in no way limiting. It is to be understood that further embodiments may be utilized and structural or logical changes may be made. The following detailed description thereof is not to be taken in a limiting sense.
According to an embodiment, a method of manufacturing an integrated circuit comprises forming a structure on a carrier, the structure comprising at least a conductive portion, etching recesses into the conductive portion to segment the conductive portion into a plurality of conductive regions arranged along a first direction, filling the recesses with a dielectric material and forming conductive lines above the conductive regions, wherein each of the conductive lines is electrically coupled to at least one of the conductive regions and extends along a second direction intersecting the first direction.
As an example, the conductive lines and conductive regions may form bitlines and bitline contacts connecting memory cells to support circuits. However, the conductive lines and conductive regions may also be used to connect any circuit part, e.g., a functional region of an integrated circuit to a further circuit part. The conductive lines and conductive regions may be formed of any conductive material such as metal, noble metal, metal alloys or doped semiconductors. Although a common material may be used to realize the conductive lines and the conductive regions, material compositions of these parts may also entirely or partly differ from each other. Exemplary materials include W, Ti, Wn, TaN, Cu, Ta, Al, metal suicides, doped silicon of any crystal structure such as doped polysilicon or doped amorphous silicon, or any combination thereof. The conductive lines and the conductive regions may further comprise a liner, for example.
The carrier may comprise a semiconductor substrate such as a silicon substrate, which may be pre-processed in any way. As a further example the carrier may be a SOI (silicon-on-insulator) carrier. Hence, the carrier may already include semiconductor zones formed therein in order to provide semiconductor devices. Furthermore, the carrier may also comprise any kind of insulating or conductive structure formed thereon before the structure is provided. In case of a non-volatile memory, the carrier may be pre-processed in such a way that source and drain regions as well as gate dielectrics and gate electrodes are already provided before provision of the structure on the pre-processed carrier.
It is further to be noted that etching the conductive portion to achieve separate conductive regions may not only lead to a chain of consecutive conductive regions arranged along the first direction but also to a plurality of parallel chains, each of the chains comprising conductive regions consecutively arranged along the first direction. Hence, the conductive portion may be etched to provide a plurality of bitline contact chains in a flash NAND memory, for example.
The structure may comprise a conductive and an insulating portion. Such a structure may be provided by first etching an opening into an insulating layer followed by filling the opening with a conductive material to provide the conductive portion laterally adjacent to the remaining insulating layer constituting the insulating portion.
The conductive portion may constitute the structure. Thus, the structure may be made up only of the conductive portion. Hence, the recesses etched into the conductive portion remove those material parts of the conductive portion that are not to be used as conductive regions. As an example, a major part of the conductive portion may be removed by etching recesses therein to achieve one or even more chains of conductive regions along the first direction.
The conductive portion may comprise a liner layer and a metal layer formed thereon. As an example, the liner layer may comprise Ti/TiN and the metal layer may be of W. However, any kind of liner layer and metal layer appropriately chosen to achieve a desired resistance with regard to the contact to be formed may be utilized.
According to a further embodiment, the conductive portion comprises a doped semiconductor layer. As an example, the doped semiconductor layer may be of doped polysilicon. Again, any kind of doped semiconductor layer may be chosen which allows to achieve an interconnection structure comprising desired properties, e.g., with regard to conductivity or process integration.
According to a further embodiment, the opening and recesses are formed by tapered etch processes such that a dimension of a bottom side of the conductive regions is larger along the first direction and smaller along the second direction than the corresponding dimensions of the top side of the conductive regions, respectively. Taking into account a taper caused by an etch process starting from the top side to the bottom side, opposite slopes of sidewall profiles of the conductive regions are introduced if sidewalls opposite along the first direction are determined by a taper of an etch process affecting the conductive portion and sidewalls opposite along the second direction are determined by a taper of an etch process affecting the insulating layer.
The recesses may also be formed by a tapered etch process such that the dimensions of the conductive regions along the first and second directions are larger at a bottom side than at a top side. Here, the recesses etched into the conductive portion surround each of the conductive regions such that a taper of sidewalls opposed along the first direction is similar or equal to a taper of sidewalls opposed along the second direction. Hence, the conductive regions may be shaped from the conductive portion in a single patterning step, e.g., a single etch process.
A bottom side of each of the conductive regions may adjoin to a top side of a conductive zone. The conductive zone may be a semiconductor zone of an active area of a semiconductor device, for example. As an example, the conductive regions may serve as bitline contacts contacting an active area assigned to a string of NAND flash memory cells. Although the conductive zones may be active areas of any kind of semiconductor device, these zones may also be part of a metal layer such as a metal line.
The conductive regions may be shaped as contact plugs.
A further embodiment relates to a method of manufacturing an integrated circuit comprising etching a linear opening into an insulating layer formed on a carrier, the linear opening extending along a first direction, filling the linear opening with a conductive structure, etching recesses into the conductive structure to segment the conductive structure into a plurality of conductive regions arranged along the first direction, filling the recesses with a dielectric material and forming conductive lines above the insulating layer and the conductive regions, wherein each of the conductive lines is electrically coupled to at least one of the conductive regions and extends along a second direction intersecting the first direction.
The linear opening and recesses may be formed by tapered etch processes such that a dimension of a bottom side of the conductive regions is larger along the first direction and smaller along the second direction than the corresponding dimensions of the top side of the conductive regions, respectively. It is to be noted that the term “linear opening” used herein refers to an opening that extends along a specified direction. However the opening may extend along the specified direction not only as a linear line but also as a undulated line or it may comprise any other kind of modulation.
According to a further embodiment, prior to etching the recesses into the conductive structure, an etch mask structure comprising parallel lines is formed on the insulating layer and the conductive structure, wherein the parallel lines are equally spaced along the first direction and extend along the second direction. The conductive regions to be formed are delimited along the second direction by the insulating layer and their arrangement along the first direction may be defined by the coverage provided by the etch mask structure. An etch process allows for a segmentation of the conductive structure along the first direction by selective removal of those parts of the conductive structure which are not covered by the etch mask structure.
A pitch between two neighboring conductive lines may equal 2×F, wherein F denotes a minimum lithographic feature size.
A further embodiment relates to a method of manufacturing an interconnection structure comprising forming a conductive structure on a carrier, etching recesses into the conductive structure to segment the conductive structure into a plurality of conductive regions arranged along a first direction, filling the recesses with a dielectric material and forming conductive lines above the conductive regions and the dielectric material, wherein each of the conductive lines is electrically coupled to at least one of the conductive regions and extends along a second direction intersecting the first direction. Here, the recesses etched into the conductive structure surround each of the conductive regions. Hence, a profile of sidewalls opposed along the first direction is similar or equal to a profile of sidewalls opposed along the second direction. The patterning of the conductive structure resulting in the conductive regions may thus be carried out by a single patterning step, e.g., a single etch process.
According to a further embodiment, an integrated circuit comprises contact plugs of a doped semiconductor material consecutively arranged along a first direction and conductive lines extending along a second direction intersecting the first direction, wherein a top side of each of the contact plugs is in contact with one of the conductive lines and opposing sidewalls delimiting the contact plugs along the first direction are tapered from a bottom side to the top side. Hence, a dimension of the contact plugs along the first direction is larger at the bottom side than at the top side.
A bottom side of each of the contact plugs may be in contact with a top side of a conductive zone.
A further embodiment relates to an integrated circuit, wherein opposing sidewalls delimiting the contact plugs along the second direction are tapered from the top side to the bottom side.
An integrated circuit according to a further embodiment comprises contact plugs consecutively arranged along a first direction and conductive lines extending along a second direction intersecting the first direction, wherein a top side of each of the contact plugs is in contact with one of the conductive lines, opposing sidewalls delimiting the contact plugs along the first direction are tapered from a bottom side to the top side and the contact plugs further comprise a liner being present at the bottom side as well as at opposing sidewalls delimiting the contact plugs along the second direction but absent at opposing sidewalls delimiting the contact plugs along the first direction.
A further embodiment relates to an integrated circuit comprising contact plugs including a liner being present at a bottom side but absent at sidewalls thereof, the contact plugs being consecutively arranged along a first direction, conductive lines extending along a second direction intersecting the first direction, wherein a top side of each of the contact plugs is in contact with one of the conductive lines, and opposing sidewalls delimiting the contact plugs along the first direction are tapered from a bottom side to the top side.
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A further embodiment related to yet another method of manufacturing an interconnection structure will now be explained with reference to schematic top views and cross-sectional views illustrated in
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As the patterning of the conductive structure 330 by means of the etch mask structure 319 does not affect the profile of sidewalls of the contact plugs 321 opposed along the second direction 306, the liner 331 still covers those sidewalls. Furthermore, when comparing opposing sidewalls of the contact plugs 321 along the first and second directions 305, 306, it is to be noted that a taper of the sidewalls opposed along the first direction is not only opposite to a taper of sidewalls opposed along the second direction 306, but there is a further structural difference in that the conductive liner 331 merely covers sidewalls delimiting the contact plugs 321 along the second direction 306 whereas the liner 331 is absent at sidewalls delimiting the contact plugs 321 along the first direction 305. It is to be further noted that a taper angle of sidewalls opposed along the first direction 305 may differ from the taper angle of sidewalls opposed along the second direction 306.
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In the following, embodiments of a method of manufacturing an interconnection structure will be briefly explained with reference to flow charts illustrated in
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According to a further embodiment, an electronic system 406 is provided that comprises an integrated circuit 401 as explained above. The electronic system 406 may be an audio system, a video system, a computer system, a game console, a communication system, a cell phone, a data storage system, a data storage module, a graphic card or portable storage device comprising an interface to a computer system, an audio system, a video system, a game console or data storage system.
Having described exemplary embodiments of the invention, it is believed that other modifications, variations and changes will be suggested to those skilled in the art in view of the teachings set forth herein. It is therefore to be understood that all such variations, modifications and changes are believed to fall within the scope of the present invention as defined by the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.