BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional schematic view of a conventional BEOL metallization process for constructing multi-level metal layers on semiconductor wafer.
FIG. 2 is a top plan view of a semiconductor wafer having a conventional layout of chip regions formed on a surface of the wafer.
FIG. 3 illustrates a conventional electroplating apparatus for performing a damascene electroplating process using a continuous metallic seed layer formed on a wafer surface to conduct electroplating current from edge regions to inner/central regions of the wafer.
FIG. 4 is high-level schematic view of a semiconductor wafer having an embedded interconnection structure that provides an electrical path to conduct bulk electroplating current from edge regions to inner/central regions of the wafer, according to an exemplary embodiment of the invention.
FIG. 5 is a schematic top plan view of a semiconductor wafer having a plurality of chip regions and a plurality of embedded interconnection structures each providing electroplating current paths to conduct bulk electroplating current to chip regions electrically coupled to respective embedded interconnection structures, according to an exemplary embodiment of the invention.
FIG. 6 is a schematic cross sectional view of a chip region formed on a semiconductor wafer having embedded interconnection structures for conducting electroplating current, according to an exemplary embodiment of the invention.
FIG. 7 schematically illustrates a top plan layout view of a semiconductor wafer having chip regions that are electrically coupled by embedded electroplating interconnection structures formed in the crack stop regions of the chip regions, according to an exemplary embodiment of the invention.
FIG. 8 schematically illustrates a top plan layout view of a semiconductor wafer having chip regions that are electrically coupled by embedded electroplating interconnection structures formed in the crack stop regions and/or moisture barrier regions of the chip regions, according to an exemplary embodiment of the invention.
FIG. 9 schematically illustrates a top plan layout view of a semiconductor wafer having chip regions that are electrically coupled by embedded electroplating interconnection structures formed in the crack stop regions of the chip regions, according to another exemplary embodiment of the invention.
FIG. 10 schematically illustrates a top plan layout view of a semiconductor wafer having chip regions that are electrically coupled by embedded electroplating interconnection structures formed in the moisture barrier regions of the chip regions, according to another exemplary embodiment of the invention.
FIG. 11 is a schematic top plan view of a semiconductor wafer having a plurality of chip regions and embedded interconnection structures formed in the crack stop regions and moisture barrier regions of the chip regions, according to another exemplary embodiment of the invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
Exemplary embodiments of the invention will now be described more fully with reference to the accompanying drawings in which it is to be understood that the thickness and dimensions of the layers and regions are exaggerated for clarity. It is to be further understood that when a layer is described as being “on” or “over” another layer or substrate, such layer may be directly on the other layer or substrate, or intervening layers may also be present. Moreover, similar reference numerals used throughout the drawings denote elements having the same or similar functions.
FIG. 4 is high-level schematic view of a semiconductor wafer having an embedded interconnection structure that provides an electrical path to conduct bulk electroplating current from edge regions to inner/central regions of the wafer, according to an exemplary embodiment of the invention. FIG. 4 illustrates a conceptual method of forming an embedded interconnection structure (205) as part of a lower level of metallization, e.g., a previous level Mx−1, which provides a continuous low resistance current path (which extends between wafer edges) for conducting bulk plating current for a plating process when form an upper level of metallization Mx. FIG. 4 illustrates an intermediate stage of Mx level fabrication, where via holes/trenches (202) are formed in an ILD (inter level dielectric) layer (201). One or more conformal metallic layers (203) are formed over the entire surface of the wafer (200), i.e., over the surface of the ILD layer (201) and lining the exposed sidewall surfaces of the via holes (202b) and trenches (202a). An insulating etch stop layer (204) is formed between the ILD layers of the Mx and Mx−1 metallization levels.
In the exemplary embodiment of FIG. 4, the metallic layer(s) (203) may be formed of separate layers, e.g., a barrier layer (e.g., TaN) and seed layer (Cu), or a single metallic layer that serves as both a diffusion barrier for copper and seed layer for copper plating (e.g., Ruthenium) using known electroplating techniques. In contrast to conventional methods, however, the metallic (seed) layer (203) does not provide a primary current path to conduct plating current from the periphery of the wafer (200) to the central regions of the wafer (200). Instead, the embedded interconnection structure (205) provides a low resistance current path to conduct bulk plating current from a peripheral region WE of the wafer (200) to inner and central regions of wafer (200) where plating current is locally distributed to inner surface regions of the wafer through short conducting paths along portions of the metallic seed layer (203) disposed in the inner and center regions of the wafer (200), for example.
Indeed, as depicted in FIG. 4, when an electrode clamp is connected to the seed layer (203) on the edges WE of the wafer surface, the bulk current can flow through short paths of the continuous seed layer (203) to the embedded interconnection structure (205) at the wafer edges WE and then flow to the inner regions of the wafer (200) through the embedded interconnection (205). In this manner, plating current can flow from the embedded interconnection (205) to various regions of the thin seed layer (203) where the plating current can flow along shorter paths through the thin copper seed layer to provide a more uniform potential across the surface of the wafer (200).
By way of example, FIG. 5 is a schematic top plan view of a semiconductor wafer having a plurality of chip regions and embedded interconnection structures providing electroplating current paths to conduct bulk electroplating current to chip regions electrically coupled to respective embedded interconnection structures, according to an exemplary embodiment of the invention. FIG. 5 illustrates a semiconductor wafer (300) having a plurality of chip regions (30) and a plurality of embedded current paths P1˜P8 that longitudinally extend in a horizontal (row) direction between end regions of the wafer (300). Each embedded current path P1˜P8 (or Pi) represents a continuous interconnection structure (formed at a given metallization level, Mi) which extends through, and is formed as part of metal structures in peripheral regions of a plurality of adjacent chip regions (30) (e.g., all chip regions (30) aligned in row direction between edge regions of the wafer (300) as in FIG. 5). As explained in further detail below, each embedded current path Pi can be a continuous metal line that is formed as part of crack stop regions and/or as part moisture barrier regions of adjacent chip regions (30) to provide low resistance current paths from the wafer edges to inner regions of the wafer. The plating current that is conducted in a given embedded current path Pi can readily flow to each chip region (30) connected to such path Pi, whereby the electroplating current can be fed to those regions of the metallic seed layer within, or in proximity to, each of the chip regions coupled to the given path Pi. This method allows for a more uniform voltage potential over the seed layer to achieve plating uniformity across the wafer surface.
FIG. 6 is a schematic cross sectional view of a chip region formed on a semiconductor wafer having embedded interconnection structures for conducting electroplating current, according to an exemplary embodiment of the invention. FIG. 6 is schematic cross sectional view of an exemplary framework for each chip region (30) formed on the semiconductor wafer (300) of FIG. 5. FIG. 6 illustrates a portion of a wafer substrate (301) having an active circuit region (31), moisture barrier (MOB) region (32) and crack stop region (33). Active devices are formed in the active circuit region (31) and the active region (31) is surrounded by the MOB region (32) and the crack stop region (33). Moreover, FIG. 6 illustrates a plurality of BEOL metallization levels M1˜M5 each comprising an ILD layer having interlevel metal wiring and/or plugs formed therein using known single and dual damascene techniques, for example.
In accordance with exemplary embodiments of the invention, embedded electroplating current interconnect structures can be formed in one or more metallization levels in the MOB region (32) and/or crack stop region (33). For instance, in one exemplary embodiment of the invention, one or more of crack stop plugs (L1) in the crack stop region (33) (which are formed as part of the first level of metallization M1) can be formed to continually extend through the crack stop regions of adjacent chip regions to form a metal line L1 that serves as an embedded current path for M2 copper metallization. By way of example, in the exemplary embodiment of FIG. 5, each embedded current path Pi can be a continuous metal line L1 which is formed by connecting contact plugs in the crack stop regions of adjacent chip regions (30) which extends in the horizontal direction between wafer edges.
By way of example, FIG. 7 schematically illustrates a top plan layout view of a semiconductor wafer having chip regions that are electrically coupled by embedded electroplating interconnection structures formed in the crack stop regions of the chip regions, according to an exemplary embodiment of the invention. In particular, FIG. 7 illustrates adjacent chip regions C1 and C2 formed on a wafer, where each chip region C1 and C2 comprises respective chip guard rings GR1, GR2, crack stop regions, CS1, CS2, and moisture barrier regions MOB1, MOB2. FIG. 7 illustrates an exemplary embodiment of FIG. 6 where the embedded current path L1 is formed by forming some or all of the 3 contact plugs in the horizontal portions of crack stop regions CS1, CS2 as continuous metal lines that extend in a horizontal direction through the crack stop regions of adjacent chip regions.
Moreover, referring back to FIG. 6, the metal lines L2 and/or L2′ that are formed in respective crack stop (33) and MOB (32) regions as part of the second level of metallization M2 can be formed to continually extend through the crack stop/MOB regions of adjacent chip regions to serve as embedded electroplating current paths for M3 copper metallization. Similarly, the metal lines L3 and/or L3′ that are formed in respective crack stop (33) and MOB (32) regions as part of the third level metallization M3 can be formed to continually extend through the crack stop/MOB regions of adjacent chip regions to serve as embedded electroplating current paths for M4 copper metallization, and the metal lines L4 and/or L4′ that are formed in respective crack stop (33) and MOB (32) regions as part of the fourth level metallization M4 can be formed to continually extend through the crack stop/MOB regions of adjacent chip regions to serve as embedded electroplating current paths for M5 copper metallization.
FIG. 8 schematically illustrates a top plan layout view of a semiconductor wafer having chip region regions that are electrically coupled by embedded electroplating interconnection structures formed in the crack stop regions and/or moisture barrier regions of the chip regions, according to an exemplary embodiment of the invention. In particular, FIG. 8 illustrates adjacent chip regions C1 and C2 formed on a wafer similar to FIG. 7, but showing a continuous embedded current path formed by the L2, L3, or L4 metal line (FIG. 6), which extends in the horizontal direction in the crack stop regions of adjacent chip regions C1 and C2 and a continuous embedded current path from by the L2′, L3′, or L4′ metal line (FIG. 6), which extends in the horizontal direction in the MOB regions of adjacent chip regions C1 and C2.
FIG. 9 schematically illustrates a top plan layout view of a semiconductor wafer having chip regions that are electrically coupled by embedded electroplating interconnection structures formed in the crack stop regions of the chip regions, according to another exemplary embodiment of the invention. FIG. 9 illustrates an exemplary embodiment in which embedded current paths are formed as continuous metal lines that extend in a horizontal direction through the crack stop regions of adjacent chip regions in a row direction, as well as continuous metal lines that extend in a vertical direction through the crack stop regions of adjacent chip regions in a column direction. In particular, FIG. 9 illustrates 4 adjacent chip regions C1, C2, C3 and C4 formed on a wafer. The adjacent chip regions C1 and C2 are connected by a continuous metal line (embedded current path) CP1 that extends in a horizontal direction through the crack stop regions CS1 and CS2 of the chip regions C1 and C2. Moreover, the adjacent chip regions C1 and C4 are connected by a continuous metal line (embedded current path.) CP2 that extends in a vertical direction through the crack stop regions CS1 and CS4 of the chip regions C1 and C4.
FIG. 10 schematically illustrates a top plan layout view of a semiconductor wafer having chip regions that are electrically coupled by embedded electroplating interconnection structures formed in the moisture barrier regions of the chip regions, according to another exemplary embodiment of the invention. In particular, FIG. 10 illustrates an exemplary embodiment in which embedded current path CP3 is formed to connect the wiring in the MOB regions MOB 1, MOB2 of adjacent chip regions C1 and C2. For example, in the embodiment of FIG. 6, the embedded current path CP3 can be formed to connect the L2′, L3′, or L4′ metal lines (FIG. 6) of adjacent chip regions.
FIG. 11 is a schematic top plan view of a semiconductor wafer having a plurality of chip regions and embedded interconnection structures formed in the crack stop regions and moisture barrier regions of the chip regions, according to another exemplary embodiment of the invention. In particular, FIG. 11 illustrates a plurality of wafer chip regions that are interconnected using embedded current paths CP1, CP2 formed by continuous interconnection formed at a given metallization level, Mi) in the MOB and/or crack stop regions of adjacent chip regions Ln a row direction and adjacent chip regions in a column direction, as well as embedded current paths CP3 connecting the MOB wiring between adjacent chip regions.
It is to be understood that the exemplary frameworks and methods for constructing embedded electroplating current paths discussed above are illustrative examples that are not intended to limit the scope of the invention. One of ordinary skill in the art can readily envision other frameworks and techniques for building and implementing embedded electroplating structures to provide low resistive paths for conducting bulk electroplating current from wafer edge to inner/central regions of the wafer to achieve electroplating uniformity over the wafer surface. Indeed, the amount and/or layout of embedded current paths needed to achieve electroplating uniformity of BEOL processing for a given wafer can widely vary depending on factors such as the electroplating process and plating solution used, the materials used to form the chips, the size of the semiconductor wafer, etc. In all exemplary embodiments, the embedded electroplating current paths in a given wafer will be formed so as to obtain a desired voltage potential across the wafer surface and achieve plating uniformity for a given electroplating process.
Moreover, semiconductor wafers having embedded electroplating current paths can be formed using known fabrication techniques, while requiring no additional processing steps. For instance, the exemplary structure of FIG. 6 can be fabricated using various processing steps as follows. Starting with the semiconductor wafer substrate (301), an isolation layer (302) (e.g., STI (shallow trench isolation) can be formed to define an active circuit region (31), a MOB region (32) and a crack stop region (33) for each of a plurality of chip regions (30) formed on the wafer substrate (301). A plurality of active devices (e.g., transistors are formed in the active region (31).
Thereafter, a first ILD layer (d1) (e.g., silicon dioxide) is formed over the surface of the wafer substrate (301), followed by an dielectric etch process and metal deposition process to form a plurality of metallic plugs in the ILD layer (d1) to provide contacts to active devices in the active region (31) and wiring/pads in the next level of metallization (M2) using known techniques and materials. The conductive plug structures L1′ and L1 in the MOB region (32) and crack stop region (33) are trench via plugs that are formed to extend around the active region (31). In one exemplary embodiment of the invention as discussed above, the trench via plugs L1 and/or L1′ can be formed to provide continuous metal traces that extend through and connect a plurality of adjacent chip regions extending in row or column direction between wafer edges. The contact via plugs in the active region (31) and trench via plugs in the MOB and crack stop regions (32), (33) can be formed using a refractory metal such as tungsten (W) using CVD. A barrier layer such as titanium (Ti) or titanium nitride (TiN) is preferably formed between the tungsten and the semiconductor material d1 to enhances adhesion and lowers the contact resistance between the tungsten layers and the impurity regions. A TiN layer may be deposited, for example, by sputtering prior to tungsten deposition by low pressure CVD, sputtering or electron beam evaporation.
Next, a thin etch stop layer and ILD layer (d2) is formed over the first level of metallization M1, followed by a dielectric etch and metal deposition processes to form wiring or traces forming the second level of metallization M2. In one exemplary embodiment, the metal wiring in M2 can be copper wiring that is formed using a single damascene process to form the trench openings in the ILD layer (d2) and copper electroplating to fill the trenches with copper and planarizing/polishing to remove excess copper. A liner material is deposited to line the trenches prior to metal deposition to provide a seed layer for metal plating. In one exemplary embodiment of the invention, as noted above, the liner layer may be formed from a layer Ta/TaN to provide a diffusion barrier and a thin conformal copper seed layer to provide a good electrolytic plating surface. In other embodiments, the liner layer may be a singly metallic layer of material such as Ru that serves as a diffusion barrier and seed layer for electroplating.
Next, a third dielectric layer (D3) is deposited, over the planarized dielectric layer (d2) of the second level of metallization M2, followed by dielectric etch process to form vias/trenches in the various regions (31), (32) and (33). A metal deposition process is then performed using dual damascene techniques to deposit a conformal liner and copper electroplating to fill the vias/trenches to form copper plugs and traces in the ILD layer d4. The above dual damascene process is repeated for each subsequent metal-plug level M4, M5, etc.
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Patent Application
20080093746
