US20120199976A1 - Interconnect structure having a via with a via gouging feature and dielectric liner sidewalls for beol integration - Google Patents
Interconnect structure having a via with a via gouging feature and dielectric liner sidewalls for beol integration Download PDFInfo
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- US20120199976A1 US20120199976A1 US13/448,780 US201213448780A US2012199976A1 US 20120199976 A1 US20120199976 A1 US 20120199976A1 US 201213448780 A US201213448780 A US 201213448780A US 2012199976 A1 US2012199976 A1 US 2012199976A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76801—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing
- H01L21/76802—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing by forming openings in dielectrics
- H01L21/76807—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing by forming openings in dielectrics for dual damascene structures
- H01L21/76808—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing by forming openings in dielectrics for dual damascene structures involving intermediate temporary filling with material
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76801—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing
- H01L21/76802—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing by forming openings in dielectrics
- H01L21/76805—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing by forming openings in dielectrics the opening being a via or contact hole penetrating the underlying conductor
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76801—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing
- H01L21/76829—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing characterised by the formation of thin functional dielectric layers, e.g. dielectric etch-stop, barrier, capping or liner layers
- H01L21/76831—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing characterised by the formation of thin functional dielectric layers, e.g. dielectric etch-stop, barrier, capping or liner layers in via holes or trenches, e.g. non-conductive sidewall liners
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76801—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing
- H01L21/76835—Combinations of two or more different dielectric layers having a low dielectric constant
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2221/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof covered by H01L21/00
- H01L2221/10—Applying interconnections to be used for carrying current between separate components within a device
- H01L2221/1005—Formation and after-treatment of dielectrics
- H01L2221/101—Forming openings in dielectrics
- H01L2221/1015—Forming openings in dielectrics for dual damascene structures
- H01L2221/1036—Dual damascene with different via-level and trench-level dielectrics
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49117—Conductor or circuit manufacturing
- Y10T29/49204—Contact or terminal manufacturing
Definitions
- the present invention relates to a semiconductor interconnect structure, and a method of fabricating the same. More particularly, the present invention relates to a semiconductor interconnect structure in which at least one via has a via gouging feature and dielectric liner sidewalls. The present invention also provides a method of forming such an interconnect structure.
- Manufacture of a semiconductor device is normally divided into two major phases.
- the “front end of the line” (FEOL) is dedicated to the creation of all the transistors in the body of the semiconductor device, and the “back end of the line” (BEOL) creates the metal interconnect structures, which connect all the transistors with each other as well as with the external world.
- the FEOL consists of a repeated sequence of steps that modifies the electrical properties of part of a wafer surface and grows new material above selected regions.
- the second phase of manufacturing begins. During the BEOL, metal interconnects are created to establish the connection pattern of the semiconductor device.
- Semiconductor devices generally include a plurality of circuits which form an integrated circuit fabricated on a semiconductor substrate.
- low k dielectric materials having a dielectric constant of less than silicon dioxide, such as porous dielectric materials have been used as inter-layer dielectric (ILD) to further reduce capacitance.
- Interconnect structures made of metal lines or vias are usually formed in and around the porous dielectric material ILD to connect elements of the circuits.
- An interconnect structure may consist of multilevel or multilayered schemes, such as, for example, single or dual damascene wiring structures.
- metal lines run parallel to the semiconductor substrate, while metal vias run perpendicular to the semiconductor substrate.
- the quality of the metal lines and metal vias is extremely important to ensure yield and reliability.
- the major problem encountered in this area today is poor mechanical strength of deep submicron metal contacts (lines and vias) embedded in low k dielectric materials, which can cause unsatisfied thermal cycling and stress migration resistance in the interconnect structures. This problem becomes more severe when new metallization approaches or porous low k dielectric materials are used.
- via punch-through To solve the weak mechanical strength issue while employing copper damascene and low k dielectric materials in an interconnect structure, a so called “via punch-through” technique has been adopted by the semiconductor industry.
- the “via punch-through” technique provides a via gouging feature as anchoring area within the lower part of the interconnect structure.
- the via gouging feature helps to achieve an improved electrical contact resistance as well as a reasonable reliability requirement through increasing mechanical strength of the metal contacts.
- FIGS. 1A-1E illustrate processing steps of a conventional process for forming an interconnect structure with a via gouging feature.
- FIG. 1A illustrates a prior art interconnect structure that is formed after a dual damascene patterning process.
- the interconnect structure has an upper interconnect level 108 which is located atop a lower interconnect level 100 .
- the lower interconnect level 100 includes a first dielectric material 102 and a copper interconnect 104 .
- the lower interconnect level 100 is separated in part from the upper interconnect level 108 by a dielectric capping layer 106 .
- the upper interconnect level 108 includes a second dielectric material 110 that includes both line openings 112 and a via opening 114 located therein.
- a top surface of the copper interconnect 104 of the lower interconnect level 100 that is beneath the via opening 114 is exposed.
- a diffusion barrier 116 such as TaN, is formed over all of the exposed surfaces, including the sidewalls and bottom horizontal surfaces of the line openings 112 and the via opening 114 .
- argon sputtering is used to clean the bottom horizontal surface of the via opening 114 and to form a gouging feature 118 into the copper interconnect 104 of the lower interconnect level 100 .
- the gouging feature 118 enhances the interconnect strength between the various interconnect levels shown.
- the diffusion barrier located at the bottom horizontal surface of each of the line openings 112 is also removed. Due to the inherent aggressive nature of the argon sputtering process, dielectric damages 120 are also formed in the second dielectric material 110 near the bottom of each of the line openings 112 .
- FIG. 1D shows the prior art interconnect structure of FIG. 1C after forming a metal liner layer 122 on all of the exposed surfaces.
- the line openings 112 and the via opening 114 are filled with a conductive metal 124 , such as copper.
- the prior art interconnect structure has poor diffusion barrier coverage and a bottom roughness at the bottom of the metal filled lines 112 (designated by reference numeral 126 ), as a result of the dielectric damages 120 formed into the second low k dielectric material 110 . Both of these characteristics reduce the quality of the diffusion barrier 116 and degrade the overall wiring reliability.
- the present invention provides a semiconductor interconnect structure in which at least one via has a via gouging feature and dielectric liner sidewalls.
- the present invention also provides a method of forming such an interconnect structure.
- the interconnect structure of the present invention provides improved wiring reliability as compared to conventional interconnect structures mentioned above.
- a first embodiment introduces a method of forming an interconnect structure.
- the method includes the steps of providing an initial interconnect structure that includes a lower interconnect level comprising a first dielectric layer having a first conductive material embedded therein, an upper interconnect level comprising a second dielectric layer having at least one via opening that exposes a portion of the first conductive material located atop the lower interconnect level, the lower and upper interconnect levels are separated in part by a dielectric capping layer, and a patterned hard mask on a surface of the upper interconnect level; removing an exposed portion of the conductive material to form at least one via gouging feature within the conductive material at a bottom of the at least one via opening; forming a dielectric liner layer on all exposed surfaces; forming at least one line opening in the second dielectric layer that extends above the at least one via opening; selectively removing the dielectric liner layer from the at least one via gouging feature while keeping at least a portion of the dielectric liner layer at sidewalls of the at least one via opening unremoved; forming a first diffusion barrier layer on all
- a second embodiment introduces an interconnect structure including a lower interconnect level including a first dielectric layer having a first conductive material embedded therein; a dielectric capping layer located on the first dielectric layer and some, but not all, portions of the first conductive material; an upper interconnect level including a second dielectric layer having at least one via opening filled with a second conductive material and at least one overlying line opening filled with the second conductive material disposed therein, wherein the at least one via opening is in contact with the first conductive material in the lower interconnect level by a via gouging feature; a dielectric liner on sidewalls of the at least one via opening; and a first diffusion barrier layer on sidewalls and a bottom of both the at least one via opening and the at least one overlying line opening.
- FIGS. 1A-1E are cross-sectional views that illustrate the basic processing steps used in the prior art for forming an interconnect structure including at least one via gouging feature.
- FIGS. 2-11 are cross-sectional views that illustrate the exemplary steps of a method of making an interconnect structure having a via with a via gouging feature and dielectric liner layer sidewalls, in accordance with embodiments of the present invention.
- the present invention provides an interconnect structure in which at least one via has a via gouging feature and dielectric liner sidewalls.
- the via also has a metallic liner layer on top of the dielectric liner layer.
- the via is filled with a conductive material.
- the dielectric liner layer acts as an additional diffusion barrier layer which prevents the conductive filling material from diffusing into the dielectric material layer.
- the interconnect structure has an improved wiring reliability over the one fabricated with a conventional process discussed above.
- the present invention also provides a method of forming an interconnect structure in which at least one via has a via gouging feature and dielectric liner sidewalls.
- a dielectric liner layer is coated on all exposed surfaces after the via gouging feature is formed, but before a line opening is formed.
- the dielectric liner layer can compensate the thickness loss of the dielectric material layer in the upper interconnect level which occurs during the process of forming the via gouging feature.
- the dielectric liner layer prevents an overlying planarization material layer from contaminating the conductive material layer in the lower interconnect level during the process of forming the line opening.
- the dielectric material layer of the upper interconnect level is subject to less harsh etch condition. As a result, there is a less chance for causing damages on the dielectric material layer.
- the initial interconnect structure 200 includes a lower interconnect level 202 and an upper interconnect level 212 that are separated in part by a dielectric capping layer 210 .
- the lower interconnect level 202 may be located above a semiconductor substrate (not shown) including one or more semiconductor devices.
- the lower interconnect level 202 includes a first dielectric layer 204 and at least one conductive material 206 .
- the conduct material 206 forms a conductive region or feature embedded in the first dielectric layer 204 .
- the lower interconnect level 202 further includes a diffusion barrier layer 208 which separates the conductive material region 206 from the first dielectric material layer 204 .
- the upper interconnect level 212 of FIG. 2 includes a second dielectric layer 214 that has at least one via opening 218 located therein.
- the at least one via opening 218 exposes a portion of the conductive material 206 in the lower interconnect level 202 .
- On top of the second dielectric layer is a patterned hard mask 216 .
- the patterned hard mask 216 is used as an etch mask to form the at least one via opening 218 in the second dielectric layer 214 .
- FIG. 2 illustrates a single via opening 218
- the present invention contemplates forming any number of such via openings in the second dielectric layer 214 which may expose other conductive regions that may be present in the first dielectric layer 204 .
- the initial structure 200 maybe made by conventional techniques well known to those skilled in the art.
- the initial interconnect structure 200 can be formed by first applying the first dielectric layer 204 to a surface of a substrate (not shown).
- the substrate may be a semiconducting material, an insulating material, a conducting material or a combination of two or more of the foregoing materials.
- a semiconductor material such as Si, SiGe, SiGeC, SiC, Ge alloys, GaAs, InAs, InP or other group IIIN or IINI semiconductor materials may be used.
- the present invention also contemplates cases in which the substrate is a layered semiconductor such as, for example, Si/SiGe, Si/SiC, silicon-on-insulators (SOIs) or silicon germanium-on-insulators (SGOIs).
- the substrate is a semiconducting material
- one or more semiconductor devices such as, for example, complementary metal oxide semiconductor (CMOS) devices may be fabricated thereon.
- CMOS complementary metal oxide semiconductor
- the insulating material can be an organic insulator, an inorganic insulator or a combination of an organic insulator and an inorganic insulator.
- the substrate can be either single layer or multilayers.
- the substrate When the substrate is a conducting material, the substrate may include, for example, polysilicon, an elemental metal, an alloy of elemental metals, a metal silicide, a metal nitride or a combination of two or more of the foregoing materials.
- the substrate can be either single layer or multilayers.
- the first dielectric layer 204 of the lower interconnect level 202 may be any interlevel or intralevel dielectrics including inorganic dielectrics or organic dielectrics.
- the first dielectric layer 204 may be porous or non-porous.
- suitable dielectrics that can be used as the first dielectric layer 204 include, but are not limited to, SiO 2 , silsesquioxanes, C doped oxides (i.e., organosilicates) that include atoms of Si, C, O and H, thermosetting polyarylene ethers, or multilayers thereof.
- polyarylene is used in this application to denote aryl moieties or substituted aryl moieties which are linked together by bonds, fused rings, or inert linking groups such as, for example, oxygen, sulfur, sulfone, sulfoxide, carbonyl and the like.
- the first dielectric layer 204 has a dielectric constant of about 4.0 or less. More preferably, the first dielectric layer 204 has a dielectric constant of about 2.8. These dielectrics generally have a lower parasitic crosstalk as compared with dielectric materials that have a dielectric constant higher than 4.0. The dielectric constants mentioned herein are measured in a vacuum.
- the thickness of the first dielectric layer 204 may vary depending on the dielectric material used as well as the exact number of dielectrics within the lower interconnect level 202 . Typically, and for normal interconnect structures, the first dielectric layer 204 has a thickness from about 200 nm to about 450 nm.
- the conductive material 206 of the lower interconnect level 202 may form a conductive region or feature embedded in the first dielectric layer 204 .
- the conductive region or feature may be formed by lithography. For example, a photoresist layer is applied to the surface of the first dielectric layer 204 . The photoresist layer is exposed to a desired pattern of radiation. The exposed photoresist layer is developed utilizing a conventional resist developer. The patterned photoresist layer is used as an etch mask to transfer the pattern into the first dielectric layer 204 . The etched region of the first dielectric layer 204 is then filled with conductive material 206 to form the conductive region or feature.
- the conductive material 206 includes, but is not limited to, polysilicon, a conductive metal, an alloy of two or more conductive metals, a conductive metal silicide or a combination of two or more of the foregoing materials.
- the conductive material 206 is a conductive metal such as Cu, W or Al. More preferably, the conductive material 206 is Cu or a Cu alloy (such as AlCu).
- the conductive material 206 is filled into the etched region of the first dielectric layer 204 using a conventional deposition process including, but not limited to, chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), sputtering, chemical solution deposition or plating.
- CVD chemical vapor deposition
- PECVD plasma enhanced chemical vapor deposition
- sputtering chemical solution deposition or plating.
- a conventional planarization process such as, for example, chemical mechanical polishing (CMP) can be used to provide a structure in which the conductive material 206 has an upper surface that is substantially coplanar with the upper surface of the first dielectric layer 204 .
- CMP chemical mechanical polishing
- the conductive material 206 is preferably separated from the first dielectric layer 204 by a diffusion barrier layer 208 .
- the diffusion barrier layer 208 may include, but is not limited to, Ta, TaN, Ti, TiN, Ru, RuTaN, RuTa, W, WN or any other material that can serve as a barrier to prevent a conductive material from diffusing into a dielectric material layer.
- the diffusion barrier layer 208 may be formed by a deposition process such as, for example, atomic layer deposition (ALD), CVD, PECVD, physical vapor deposition (PVD), sputtering, chemical solution deposition, or plating.
- the diffusion barrier layer 208 may also include a bilayer structure that includes a lower layer of a metallic nitride such as, for example, TaN and an upper metallic layer such as, for example, Ta.
- the thickness of the diffusion barrier layer 208 may vary depending on the exact means of the deposition process as well as the material employed. Typically, the diffusion barrier layer 208 has a thickness from about 4 nm to about 40 nm, with a thickness from about 7 nm to about 20 nm being more typical.
- a dielectric capping layer 210 is formed on the surface of the lower interconnect level 202 .
- the dielectric capping layer 210 is formed by a conventional deposition process such as, for example, CVD, PECVD, chemical solution deposition, or evaporation.
- the dielectric capping layer 210 may be any suitable dielectric capping material including, but not limited to, SiC, Si 4 NH 3 , SiO 2 , a carbon doped oxide, a nitrogen and hydrogen doped silicon carbide (SiC(N,H)), or multilayers thereof.
- the thickness of the dielectric capping layer 210 may vary depending on the exact means of the deposition process as well as the material employed. Typically, the dielectric capping layer 210 has a thickness from about 15 nm to about 55 nm, with a thickness from about 25 nm to about 45 nm being more typical.
- the upper interconnect level 212 is formed by applying the second dielectric layer 214 on the upper exposed surface of the dielectric capping layer 210 .
- the second dielectric layer 214 may be the same or different dielectric material as that of the first dielectric layer 204 of the lower interconnect level 202 .
- the second dielectric layer 214 is the same dielectric material as that of the first dielectric layer 204 .
- suitable dielectrics that can be used as the second dielectric layer 214 include, but are not limited to, SiO 2 , silsesquioxanes, C doped oxides (i.e., organosilicates) that include atoms of Si, C, O and H, thermosetting polyarylene ethers, or multilayers thereof.
- the second dielectric layer 214 has a dielectric constant of about 4.0 or less. More preferably, the second dielectric layer 214 has a dielectric constant of about 2.8 or less.
- the processing techniques and thickness ranges for the first dielectric layer 204 are also applicable here for the second dielectric layer 214 .
- the second dielectric layer 214 can also comprise two different materials, i.e., deposition of one dielectric material first, followed by deposition of a different dielectric material.
- the second dielectric layer 214 comprises two different low k dielectric materials, such as a porous low k dielectric material and a dense (or non-porous) low k dielectric material.
- the upper interconnect level 212 has a hybrid structure with the subsequently filled conductive line embedded in a porous low k dielectric material, and the subsequently filled via embedded in a dense low k dielectric material.
- the porous low k dielectric has a dielectric constant of about 2.8 or less
- the dense porous low k dielectric has a dielectric constant of about 4.0 or less.
- the hard mask 216 includes an oxide, nitride, oxynitride or a combination of two or more of the foregoing materials.
- the hard mask 216 may have a single layer or multilayer structure.
- the hard mask 216 is an oxide such as SiO 2 or a nitride such as Si 3 N 4 .
- the hard mask 216 is formed utilizing a conventional deposition process such as, for example, CVD, PECVD, chemical solution deposition or evaporation.
- the thickness of the as-deposited hard mask 216 may vary depending upon the type of hard mask material formed, the number of layers that make up the hard mask layer 216 and the deposition technique used in forming the same. Typically, the as-deposited hard mask 216 has a thickness from about 10 nm to about 80 nm, with a thickness from about 20 nm to about 60 nm being even more typical.
- the hard mask 216 is patterned by a lithographic process.
- a photoresist (not shown) is formed atop the hard mask 216 by a conventional deposition process such as, for example, spin-on coating or chemical solution deposition.
- the photoresist may be a positive-tone or a negative-tone photoresist.
- the photoresist is then subjected to a lithographic process which includes exposing the photoresist to a pattern of radiation and developing the exposed resist utilizing a conventional resist developer.
- the lithographic step provides a patterned photoresist atop the hard mask 216 that defines the width of the via opening 218 .
- the via pattern is transferred into the hard mask 216 and then subsequently into the second dielectric layer 214 utilizing one or more etching processes.
- the patterned photoresist can be stripped immediately after the via pattern is transferred into the hard mask 216 by utilizing a conventional stripping process. Alternatively, the patterned photoresist can be stripped after the via pattern is transferred into the second dielectric layer 214 .
- the etching used in transferring the via pattern may comprise a dry etching process, a wet chemical etching process or a combination thereof.
- dry etching is used herein to denote an etching technique such as reactive-ion etching, ion beam etching, plasma etching, or laser ablation.
- an ion-sputtering process is employed to remove an exposed portion of the conductive material 206 and create a via gouge feature 220 at the bottom of the via opening 218 .
- the ion-sputtering is conducted with a gas source including, but not limited to, Ar, He, Xe, Ne, Kr, Rn, N 2 or H 2 .
- the ion-sputtering process used to create the via gouging feature 220 also removes a portion of the upper interconnect level 212 .
- the ion-sputtering process removes portion of the hard mask 216 .
- the ion-sputtering process completely removes the hard mask 216 and also removes portion of the second dielectric layer 214 . In either case, the ion-sputtering process costs a thickness loss in the total dielectric stack which includes the hard mask 216 and the second dielectric layer 214 .
- FIGS. 4A and 4B illustrate the structures of FIGS. 3A and 3B respectively after a dielectric liner layer 222 is formed on all exposed surfaces including the upper surface of the upper interconnect level 212 and the sidewalls and the bottom of the via opening 218 .
- the dielectric liner layer 222 increases the thickness of the total dielectric stack and compensates the thickness loss of the total dielectric stack which occurs during the ion-sputtering process.
- the dielectric liner layer 222 can be a dielectric material. Suitable dielectric materials for the dielectric liner layer 222 include, but are not limited to, SiO 2 , Si 3 N 4 , SiC, a nitrogen and hydrogen doped silicon carbide (SiC(N, H)), and all other dielectric materials commonly used in the semiconductor industry.
- the dielectric liner layer 222 may be formed by a CVD process, a PECVD process, an ALD process, or a plasma enhanced atomic layer deposition (PEALD) process.
- CVD chemical vapor deposition
- PECVD plasma enhanced atomic layer deposition
- the thickness of the dielectric liner layer 222 may vary depending on the exact means of the deposition process as well as the material employed. Typically, the dielectric liner layer 222 has a thickness from about 2 nm to about 100 nm, with a thickness from about 5 nm to about 20 nm being more typical.
- a line opening 230 is formed in the second dielectric layer 214 .
- the line opening 230 extends above the via opening 218 .
- a second line opening 231 is also formed in the second dielectric layer 214 .
- the second line opening 231 is away from, and not overlying, the via opening 218 .
- Line openings 230 and 231 are formed by a lithographic process known in the art.
- the via opening 218 may be filled with a material 224 suitable for planarization.
- Material 224 may include, but not limited to, OPL (organic planarizing layer), IPL (inorganic planarizing layer), ARC (anti-reflective coating) or combinations thereof.
- a top surface of material 224 may then be planarized.
- a second hard mask 226 may be formed on the planarized top surface of material 224 .
- a photoresist layer is formed atop the hard mask 226 by a conventional deposition process such as, for example, spin-on coating or chemical solution deposition.
- the photoresist layer may be a positive-tone or a negative-tone photoresist.
- the photoresist is then subjected to a lithographic process which includes exposing the photoresist to a pattern of radiation and developing the exposed resist utilizing a conventional resist developer.
- the lithographic step provides a patterned photoresist 228 atop the hard mask 226 that defines the width of the line openings 230 and 231 .
- the line patterns are transferred into the hard mask 226 and then subsequently into the second dielectric layer 214 utilizing one or more etching processes.
- the one or more etching processes form line openings 230 and 231 in the second dielectric layer 214 .
- at least one of the line openings 230 is located above and connect to the via opening 218 , which is protected by the remaining planarization material 224 .
- the one or more etching processes remove, in sequential order, exposed portions of the second hard mask 226 , the underlying portions of the planarization material 224 , and exposed portions of the second dielectric layer 214 .
- the patterned photoresist 228 and the patterned second hard mask 226 are typically consumed during the above mentioned etching processes.
- the conductive material 206 in the lower interconnect level 202 is separated from the planarization material 224 by the dielectric liner layer 222 .
- the existence of the dielectric liner layer 222 can prevent potential contamination of the conductive material 206 by the planarization material 224 , and therefore enhances reliability of the final interconnect structure.
- FIG. 7 shows the structure of FIG. 6 after the remaining planarization material 224 is stripped from the via opening 218 .
- the stripping of the remaining planarization material 224 is performed by either a chemical wet etching process or a chemical ashing process that is selective in removing the planarization material 224 from the structure.
- a portion of the dielectric liner layer 222 is selectively removed. As shown in FIG. 8 , the selective removing process only removes the portion of the dielectric liner layer 222 at the via gouging feature 220 located at the bottom the via opening 218 , while keeping the portion of the dielectric liner layer 222 at sidewalls of the via opening 218 unremoved.
- the selective removing process includes, but is not limited to, a plasma stripping process, a wet chemical etching process, and an ion-sputtering process with a gas resource.
- the plasma stripping process includes a hydrogen plasma stripping process.
- the selective removing process is a wet chemical etching process
- the process includes a wet chemical etching process with a dilute HF solution, a dilute HCl solution, a H 2 O 2 solution, or a combination comprising two or more of the foregoing solutions.
- the gas source may include Ar, He, Xe, Ne, Kr, Rn, N 2 or H 2 .
- a diffusion barrier layer 232 is formed on all exposed surfaces of the structure, including the exposed surfaces of the line openings 230 and 231 , the via opening 218 and the via gouging feature 220 ( FIG. 9 ).
- the diffusion barrier layer 232 may include, but is not limited to, Ta, TaN, Ti, TiN, Ru, RuN, RuTa, RuTaN, W, WN, Co, CoW, Mn, MnO, a combination comprising two or more of the foregoing materials or any other material that can serve as a barrier to prevent a conductive material from diffusing there through. Combinations of these materials are also contemplated to form a multilayered stacked diffusion barrier layer.
- the diffusion barrier layer 232 is formed utilizing a deposition process such as, for example, ALD, CVD, PECVD, PVD, sputtering, chemical solution deposition, or plating. It is noted that the diffusion barrier layer 232 is continuously present in the line openings 230 and 231 throughout the inventive process.
- the thickness of the diffusion barrier layer 232 may vary depending on the number of material layers within the barrier layer, the technique used in forming the same as well as the material of the diffusion barrier layer itself. Typically, the diffusion barrier layer 232 has a thickness from about 4 nm to about 40 nm, with a thickness from about 7 nm to about 20 nm being more typical.
- An optional adhesion/plating seed layer (not shown) can be located atop the diffusion barrier layer 232 .
- the optional adhesion/plating seed layer is comprised of a metal or metal alloy from Group VIIIA of the Periodic Table of Elements.
- suitable Group VIIIA elements for the adhesion/plating seed layer include, but are not limited to, Ru, TaRu, Ir, Rh, Pt, Pd, Co and alloys thereof. In some embodiments, it is preferred to use Ru, Ir, Co or Rh as the adhesion/plating seed layer.
- the adhesion/plating seed layer is formed by a conventional deposition process including, for example, CVD, PECVD, ALD, plating, sputtering and PVD.
- the thickness of the adhesion/plating seed layer may vary depending on number of factors including, for example, the compositional material of the adhesion/plating seed layer and the technique that was used in forming the same.
- the adhesion/plating seed layer has a thickness from about 0.5 nm to about 10 nm, with a thickness of about 0.5 nm to about 6 nm being more typical.
- the line openings 230 and 231 , the via opening 218 as well as the via gouging feature 220 are filled with a second conductive material 234 .
- the second conductive material 234 may be the same or different, preferably the same, conductive material as that of the first conductive material 206 .
- the second conductive material 234 is Cu, Al, W or an alloy of two or more of the foregoing metals. More preferably, the second conductive material 234 is Cu or AlCu alloy. It is noted that when polysilicon is used as the conductive material 234 , the adhesion/plating seed layer is typically not used.
- the adhesion/plating seed layer is typically used.
- the second conductive material 234 is formed utilizing the same deposition processing as described above in forming the first conductive material 206 . As shown, the second conductive material 234 extends above the upper surface of the second dielectric layer 214 .
- planarization which provides the planar interconnect structure shown in FIG. 11 .
- the planarization process removes various materials that are located atop the second dielectric layer 214 of the upper interconnect level 212 .
- Chemical mechanical polishing (CMP) and/or grinding may be used in this step of the present invention.
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Abstract
Description
- The present application is a divisional application of co-pending U.S. application Ser. No. 12/608,377, filed on Oct. 29, 2009, the contents of which are incorporated by reference in its entirety herein.
- The present invention relates to a semiconductor interconnect structure, and a method of fabricating the same. More particularly, the present invention relates to a semiconductor interconnect structure in which at least one via has a via gouging feature and dielectric liner sidewalls. The present invention also provides a method of forming such an interconnect structure.
- Manufacture of a semiconductor device is normally divided into two major phases. The “front end of the line” (FEOL) is dedicated to the creation of all the transistors in the body of the semiconductor device, and the “back end of the line” (BEOL) creates the metal interconnect structures, which connect all the transistors with each other as well as with the external world. The FEOL consists of a repeated sequence of steps that modifies the electrical properties of part of a wafer surface and grows new material above selected regions. Once all active components are created, the second phase of manufacturing (BEOL) begins. During the BEOL, metal interconnects are created to establish the connection pattern of the semiconductor device.
- Semiconductor devices generally include a plurality of circuits which form an integrated circuit fabricated on a semiconductor substrate. To improve the performance of the circuits, low k dielectric materials having a dielectric constant of less than silicon dioxide, such as porous dielectric materials, have been used as inter-layer dielectric (ILD) to further reduce capacitance. Interconnect structures made of metal lines or vias are usually formed in and around the porous dielectric material ILD to connect elements of the circuits. An interconnect structure may consist of multilevel or multilayered schemes, such as, for example, single or dual damascene wiring structures. Within a typical interconnect structure, metal lines run parallel to the semiconductor substrate, while metal vias run perpendicular to the semiconductor substrate.
- The quality of the metal lines and metal vias is extremely important to ensure yield and reliability. The major problem encountered in this area today is poor mechanical strength of deep submicron metal contacts (lines and vias) embedded in low k dielectric materials, which can cause unsatisfied thermal cycling and stress migration resistance in the interconnect structures. This problem becomes more severe when new metallization approaches or porous low k dielectric materials are used.
- To solve the weak mechanical strength issue while employing copper damascene and low k dielectric materials in an interconnect structure, a so called “via punch-through” technique has been adopted by the semiconductor industry. The “via punch-through” technique provides a via gouging feature as anchoring area within the lower part of the interconnect structure. The via gouging feature helps to achieve an improved electrical contact resistance as well as a reasonable reliability requirement through increasing mechanical strength of the metal contacts.
-
FIGS. 1A-1E illustrate processing steps of a conventional process for forming an interconnect structure with a via gouging feature.FIG. 1A illustrates a prior art interconnect structure that is formed after a dual damascene patterning process. The interconnect structure has anupper interconnect level 108 which is located atop alower interconnect level 100. Thelower interconnect level 100 includes a firstdielectric material 102 and acopper interconnect 104. Thelower interconnect level 100 is separated in part from theupper interconnect level 108 by adielectric capping layer 106. Theupper interconnect level 108 includes a seconddielectric material 110 that includes bothline openings 112 and a via opening 114 located therein. A top surface of thecopper interconnect 104 of thelower interconnect level 100 that is beneath thevia opening 114 is exposed. - In
FIG. 1B , adiffusion barrier 116, such as TaN, is formed over all of the exposed surfaces, including the sidewalls and bottom horizontal surfaces of theline openings 112 and thevia opening 114. InFIG. 1C , argon sputtering is used to clean the bottom horizontal surface of the via opening 114 and to form agouging feature 118 into thecopper interconnect 104 of thelower interconnect level 100. Thegouging feature 118 enhances the interconnect strength between the various interconnect levels shown. As shown inFIG. 1C , during the argon sputtering process, the diffusion barrier located at the bottom horizontal surface of each of theline openings 112 is also removed. Due to the inherent aggressive nature of the argon sputtering process,dielectric damages 120 are also formed in the seconddielectric material 110 near the bottom of each of theline openings 112. -
FIG. 1D shows the prior art interconnect structure ofFIG. 1C after forming ametal liner layer 122 on all of the exposed surfaces. InFIG. 1E , theline openings 112 and thevia opening 114 are filled with aconductive metal 124, such as copper. As shown inFIG. 1E , the prior art interconnect structure has poor diffusion barrier coverage and a bottom roughness at the bottom of the metal filled lines 112 (designated by reference numeral 126), as a result of thedielectric damages 120 formed into the second low kdielectric material 110. Both of these characteristics reduce the quality of thediffusion barrier 116 and degrade the overall wiring reliability. - The present invention provides a semiconductor interconnect structure in which at least one via has a via gouging feature and dielectric liner sidewalls. The present invention also provides a method of forming such an interconnect structure. The interconnect structure of the present invention provides improved wiring reliability as compared to conventional interconnect structures mentioned above.
- A first embodiment introduces a method of forming an interconnect structure.
- The method includes the steps of providing an initial interconnect structure that includes a lower interconnect level comprising a first dielectric layer having a first conductive material embedded therein, an upper interconnect level comprising a second dielectric layer having at least one via opening that exposes a portion of the first conductive material located atop the lower interconnect level, the lower and upper interconnect levels are separated in part by a dielectric capping layer, and a patterned hard mask on a surface of the upper interconnect level; removing an exposed portion of the conductive material to form at least one via gouging feature within the conductive material at a bottom of the at least one via opening; forming a dielectric liner layer on all exposed surfaces; forming at least one line opening in the second dielectric layer that extends above the at least one via opening; selectively removing the dielectric liner layer from the at least one via gouging feature while keeping at least a portion of the dielectric liner layer at sidewalls of the at least one via opening unremoved; forming a first diffusion barrier layer on all exposed surfaces; and filling the at least one line opening and at least one via opening with a second conductive material.
- A second embodiment introduces an interconnect structure including a lower interconnect level including a first dielectric layer having a first conductive material embedded therein; a dielectric capping layer located on the first dielectric layer and some, but not all, portions of the first conductive material; an upper interconnect level including a second dielectric layer having at least one via opening filled with a second conductive material and at least one overlying line opening filled with the second conductive material disposed therein, wherein the at least one via opening is in contact with the first conductive material in the lower interconnect level by a via gouging feature; a dielectric liner on sidewalls of the at least one via opening; and a first diffusion barrier layer on sidewalls and a bottom of both the at least one via opening and the at least one overlying line opening.
- The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
-
FIGS. 1A-1E are cross-sectional views that illustrate the basic processing steps used in the prior art for forming an interconnect structure including at least one via gouging feature. -
FIGS. 2-11 are cross-sectional views that illustrate the exemplary steps of a method of making an interconnect structure having a via with a via gouging feature and dielectric liner layer sidewalls, in accordance with embodiments of the present invention. - It will be appreciated that for simplicity and clarity of illustration, elements shown in the drawings have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for purpose of clarity.
- The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numerals refer to like features throughout.
- It will be understood that when an element, such as a layer, is referred to as being “on” or “over” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or “directly over” another element, there are no intervening elements present.
- The present invention provides an interconnect structure in which at least one via has a via gouging feature and dielectric liner sidewalls. The via also has a metallic liner layer on top of the dielectric liner layer. The via is filled with a conductive material. The dielectric liner layer acts as an additional diffusion barrier layer which prevents the conductive filling material from diffusing into the dielectric material layer. As a result, the interconnect structure has an improved wiring reliability over the one fabricated with a conventional process discussed above.
- The present invention also provides a method of forming an interconnect structure in which at least one via has a via gouging feature and dielectric liner sidewalls. In this method, a dielectric liner layer is coated on all exposed surfaces after the via gouging feature is formed, but before a line opening is formed. The dielectric liner layer can compensate the thickness loss of the dielectric material layer in the upper interconnect level which occurs during the process of forming the via gouging feature. In addition, the dielectric liner layer prevents an overlying planarization material layer from contaminating the conductive material layer in the lower interconnect level during the process of forming the line opening. Furthermore, during the line opening formation process, since there is no metal liner layer involved, the dielectric material layer of the upper interconnect level is subject to less harsh etch condition. As a result, there is a less chance for causing damages on the dielectric material layer.
- Referring to
FIG. 2 , aninitial interconnect structure 200 is provided. Theinitial interconnect structure 200 includes alower interconnect level 202 and anupper interconnect level 212 that are separated in part by adielectric capping layer 210. Thelower interconnect level 202 may be located above a semiconductor substrate (not shown) including one or more semiconductor devices. Thelower interconnect level 202 includes a firstdielectric layer 204 and at least oneconductive material 206. Theconduct material 206 forms a conductive region or feature embedded in thefirst dielectric layer 204. Preferably, thelower interconnect level 202 further includes adiffusion barrier layer 208 which separates theconductive material region 206 from the firstdielectric material layer 204. - The
upper interconnect level 212 ofFIG. 2 includes asecond dielectric layer 214 that has at least one viaopening 218 located therein. The at least one viaopening 218 exposes a portion of theconductive material 206 in thelower interconnect level 202. On top of the second dielectric layer is a patternedhard mask 216. The patternedhard mask 216 is used as an etch mask to form the at least one viaopening 218 in thesecond dielectric layer 214. Although the structure shown inFIG. 2 illustrates a single viaopening 218, the present invention contemplates forming any number of such via openings in thesecond dielectric layer 214 which may expose other conductive regions that may be present in thefirst dielectric layer 204. - The
initial structure 200 maybe made by conventional techniques well known to those skilled in the art. For example, theinitial interconnect structure 200 can be formed by first applying thefirst dielectric layer 204 to a surface of a substrate (not shown). The substrate may be a semiconducting material, an insulating material, a conducting material or a combination of two or more of the foregoing materials. When the substrate is comprised of a semiconducting material, a semiconductor material such as Si, SiGe, SiGeC, SiC, Ge alloys, GaAs, InAs, InP or other group IIIN or IINI semiconductor materials may be used. In addition to these listed types of semiconducting materials, the present invention also contemplates cases in which the substrate is a layered semiconductor such as, for example, Si/SiGe, Si/SiC, silicon-on-insulators (SOIs) or silicon germanium-on-insulators (SGOIs). When the substrate is a semiconducting material, one or more semiconductor devices such as, for example, complementary metal oxide semiconductor (CMOS) devices may be fabricated thereon. - When the substrate is an insulating material, the insulating material can be an organic insulator, an inorganic insulator or a combination of an organic insulator and an inorganic insulator. The substrate can be either single layer or multilayers.
- When the substrate is a conducting material, the substrate may include, for example, polysilicon, an elemental metal, an alloy of elemental metals, a metal silicide, a metal nitride or a combination of two or more of the foregoing materials. The substrate can be either single layer or multilayers.
- The
first dielectric layer 204 of thelower interconnect level 202 may be any interlevel or intralevel dielectrics including inorganic dielectrics or organic dielectrics. Thefirst dielectric layer 204 may be porous or non-porous. Examples of suitable dielectrics that can be used as thefirst dielectric layer 204 include, but are not limited to, SiO2, silsesquioxanes, C doped oxides (i.e., organosilicates) that include atoms of Si, C, O and H, thermosetting polyarylene ethers, or multilayers thereof. The term “polyarylene” is used in this application to denote aryl moieties or substituted aryl moieties which are linked together by bonds, fused rings, or inert linking groups such as, for example, oxygen, sulfur, sulfone, sulfoxide, carbonyl and the like. - Preferably, the
first dielectric layer 204 has a dielectric constant of about 4.0 or less. More preferably, thefirst dielectric layer 204 has a dielectric constant of about 2.8. These dielectrics generally have a lower parasitic crosstalk as compared with dielectric materials that have a dielectric constant higher than 4.0. The dielectric constants mentioned herein are measured in a vacuum. - The thickness of the
first dielectric layer 204 may vary depending on the dielectric material used as well as the exact number of dielectrics within thelower interconnect level 202. Typically, and for normal interconnect structures, thefirst dielectric layer 204 has a thickness from about 200 nm to about 450 nm. - The
conductive material 206 of thelower interconnect level 202 may form a conductive region or feature embedded in thefirst dielectric layer 204. The conductive region or feature may be formed by lithography. For example, a photoresist layer is applied to the surface of thefirst dielectric layer 204. The photoresist layer is exposed to a desired pattern of radiation. The exposed photoresist layer is developed utilizing a conventional resist developer. The patterned photoresist layer is used as an etch mask to transfer the pattern into thefirst dielectric layer 204. The etched region of thefirst dielectric layer 204 is then filled withconductive material 206 to form the conductive region or feature. - The
conductive material 206 includes, but is not limited to, polysilicon, a conductive metal, an alloy of two or more conductive metals, a conductive metal silicide or a combination of two or more of the foregoing materials. Preferably, theconductive material 206 is a conductive metal such as Cu, W or Al. More preferably, theconductive material 206 is Cu or a Cu alloy (such as AlCu). Theconductive material 206 is filled into the etched region of thefirst dielectric layer 204 using a conventional deposition process including, but not limited to, chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), sputtering, chemical solution deposition or plating. After deposition, a conventional planarization process such as, for example, chemical mechanical polishing (CMP) can be used to provide a structure in which theconductive material 206 has an upper surface that is substantially coplanar with the upper surface of thefirst dielectric layer 204. - The
conductive material 206 is preferably separated from thefirst dielectric layer 204 by adiffusion barrier layer 208. Thediffusion barrier layer 208 may include, but is not limited to, Ta, TaN, Ti, TiN, Ru, RuTaN, RuTa, W, WN or any other material that can serve as a barrier to prevent a conductive material from diffusing into a dielectric material layer. Thediffusion barrier layer 208 may be formed by a deposition process such as, for example, atomic layer deposition (ALD), CVD, PECVD, physical vapor deposition (PVD), sputtering, chemical solution deposition, or plating. Thediffusion barrier layer 208 may also include a bilayer structure that includes a lower layer of a metallic nitride such as, for example, TaN and an upper metallic layer such as, for example, Ta. - The thickness of the
diffusion barrier layer 208 may vary depending on the exact means of the deposition process as well as the material employed. Typically, thediffusion barrier layer 208 has a thickness from about 4 nm to about 40 nm, with a thickness from about 7 nm to about 20 nm being more typical. - After forming the at least one conductive feature comprising the
conductive material 206 within thefirst dielectric layer 204, adielectric capping layer 210 is formed on the surface of thelower interconnect level 202. Thedielectric capping layer 210 is formed by a conventional deposition process such as, for example, CVD, PECVD, chemical solution deposition, or evaporation. Thedielectric capping layer 210 may be any suitable dielectric capping material including, but not limited to, SiC, Si4NH3, SiO2, a carbon doped oxide, a nitrogen and hydrogen doped silicon carbide (SiC(N,H)), or multilayers thereof. The thickness of thedielectric capping layer 210 may vary depending on the exact means of the deposition process as well as the material employed. Typically, thedielectric capping layer 210 has a thickness from about 15 nm to about 55 nm, with a thickness from about 25 nm to about 45 nm being more typical. - Next, the
upper interconnect level 212 is formed by applying thesecond dielectric layer 214 on the upper exposed surface of thedielectric capping layer 210. Thesecond dielectric layer 214 may be the same or different dielectric material as that of thefirst dielectric layer 204 of thelower interconnect level 202. Preferably thesecond dielectric layer 214 is the same dielectric material as that of thefirst dielectric layer 204. Examples of suitable dielectrics that can be used as thesecond dielectric layer 214 include, but are not limited to, SiO2, silsesquioxanes, C doped oxides (i.e., organosilicates) that include atoms of Si, C, O and H, thermosetting polyarylene ethers, or multilayers thereof. Preferably, thesecond dielectric layer 214 has a dielectric constant of about 4.0 or less. More preferably, thesecond dielectric layer 214 has a dielectric constant of about 2.8 or less. The processing techniques and thickness ranges for thefirst dielectric layer 204 are also applicable here for thesecond dielectric layer 214. - The
second dielectric layer 214 can also comprise two different materials, i.e., deposition of one dielectric material first, followed by deposition of a different dielectric material. In one embodiment of the present invention, thesecond dielectric layer 214 comprises two different low k dielectric materials, such as a porous low k dielectric material and a dense (or non-porous) low k dielectric material. Thus, theupper interconnect level 212 has a hybrid structure with the subsequently filled conductive line embedded in a porous low k dielectric material, and the subsequently filled via embedded in a dense low k dielectric material. In such an embodiment, the porous low k dielectric has a dielectric constant of about 2.8 or less, and the dense porous low k dielectric has a dielectric constant of about 4.0 or less. - Next, at least one via
opening 218 is formed into thesecond dielectric layer 214 by first forming a patternedhard mask 216 atop the upper surface of thesecond dielectric layer 214. Thehard mask 216 includes an oxide, nitride, oxynitride or a combination of two or more of the foregoing materials. Thehard mask 216 may have a single layer or multilayer structure. Preferably, thehard mask 216 is an oxide such as SiO2 or a nitride such as Si3N4. Thehard mask 216 is formed utilizing a conventional deposition process such as, for example, CVD, PECVD, chemical solution deposition or evaporation. The thickness of the as-depositedhard mask 216 may vary depending upon the type of hard mask material formed, the number of layers that make up thehard mask layer 216 and the deposition technique used in forming the same. Typically, the as-depositedhard mask 216 has a thickness from about 10 nm to about 80 nm, with a thickness from about 20 nm to about 60 nm being even more typical. - The
hard mask 216 is patterned by a lithographic process. A photoresist (not shown) is formed atop thehard mask 216 by a conventional deposition process such as, for example, spin-on coating or chemical solution deposition. The photoresist may be a positive-tone or a negative-tone photoresist. The photoresist is then subjected to a lithographic process which includes exposing the photoresist to a pattern of radiation and developing the exposed resist utilizing a conventional resist developer. The lithographic step provides a patterned photoresist atop thehard mask 216 that defines the width of the viaopening 218. The via pattern is transferred into thehard mask 216 and then subsequently into thesecond dielectric layer 214 utilizing one or more etching processes. - The patterned photoresist can be stripped immediately after the via pattern is transferred into the
hard mask 216 by utilizing a conventional stripping process. Alternatively, the patterned photoresist can be stripped after the via pattern is transferred into thesecond dielectric layer 214. The etching used in transferring the via pattern may comprise a dry etching process, a wet chemical etching process or a combination thereof. The term “dry etching” is used herein to denote an etching technique such as reactive-ion etching, ion beam etching, plasma etching, or laser ablation. - Referring now to
FIGS. 3A and 3B , an ion-sputtering process is employed to remove an exposed portion of theconductive material 206 and create a viagouge feature 220 at the bottom of the viaopening 218. The ion-sputtering is conducted with a gas source including, but not limited to, Ar, He, Xe, Ne, Kr, Rn, N2 or H2. - The ion-sputtering process used to create the via
gouging feature 220 also removes a portion of theupper interconnect level 212. In one embodiment, as shown inFIG. 3A , the ion-sputtering process removes portion of thehard mask 216. In another embodiment, as shown inFIG. 3B , the ion-sputtering process completely removes thehard mask 216 and also removes portion of thesecond dielectric layer 214. In either case, the ion-sputtering process costs a thickness loss in the total dielectric stack which includes thehard mask 216 and thesecond dielectric layer 214. -
FIGS. 4A and 4B illustrate the structures ofFIGS. 3A and 3B respectively after adielectric liner layer 222 is formed on all exposed surfaces including the upper surface of theupper interconnect level 212 and the sidewalls and the bottom of the viaopening 218. Thedielectric liner layer 222 increases the thickness of the total dielectric stack and compensates the thickness loss of the total dielectric stack which occurs during the ion-sputtering process. - The
dielectric liner layer 222 can be a dielectric material. Suitable dielectric materials for thedielectric liner layer 222 include, but are not limited to, SiO2, Si3N4, SiC, a nitrogen and hydrogen doped silicon carbide (SiC(N, H)), and all other dielectric materials commonly used in the semiconductor industry. - The
dielectric liner layer 222 may be formed by a CVD process, a PECVD process, an ALD process, or a plasma enhanced atomic layer deposition (PEALD) process. - The thickness of the
dielectric liner layer 222 may vary depending on the exact means of the deposition process as well as the material employed. Typically, thedielectric liner layer 222 has a thickness from about 2 nm to about 100 nm, with a thickness from about 5 nm to about 20 nm being more typical. - In
FIGS. 5 and 6 , aline opening 230 is formed in thesecond dielectric layer 214. Theline opening 230 extends above the viaopening 218. Optionally, a second line opening 231 is also formed in thesecond dielectric layer 214. The second line opening 231 is away from, and not overlying, the viaopening 218. -
Line openings FIG. 5 , the viaopening 218 may be filled with a material 224 suitable for planarization.Material 224 may include, but not limited to, OPL (organic planarizing layer), IPL (inorganic planarizing layer), ARC (anti-reflective coating) or combinations thereof. A top surface ofmaterial 224 may then be planarized. On the planarized top surface ofmaterial 224, a secondhard mask 226 may be formed. - Next, a photoresist layer is formed atop the
hard mask 226 by a conventional deposition process such as, for example, spin-on coating or chemical solution deposition. The photoresist layer may be a positive-tone or a negative-tone photoresist. The photoresist is then subjected to a lithographic process which includes exposing the photoresist to a pattern of radiation and developing the exposed resist utilizing a conventional resist developer. The lithographic step provides apatterned photoresist 228 atop thehard mask 226 that defines the width of theline openings - In
FIG. 6 , the line patterns are transferred into thehard mask 226 and then subsequently into thesecond dielectric layer 214 utilizing one or more etching processes. As shown inFIG. 6 , the one or more etching processes formline openings second dielectric layer 214. In accordance with the present invention, at least one of theline openings 230 is located above and connect to the viaopening 218, which is protected by the remainingplanarization material 224. The one or more etching processes remove, in sequential order, exposed portions of the secondhard mask 226, the underlying portions of theplanarization material 224, and exposed portions of thesecond dielectric layer 214. The patternedphotoresist 228 and the patterned secondhard mask 226 are typically consumed during the above mentioned etching processes. - As shown in
FIG. 6 , theconductive material 206 in thelower interconnect level 202 is separated from theplanarization material 224 by thedielectric liner layer 222. The existence of thedielectric liner layer 222 can prevent potential contamination of theconductive material 206 by theplanarization material 224, and therefore enhances reliability of the final interconnect structure. -
FIG. 7 shows the structure ofFIG. 6 after the remainingplanarization material 224 is stripped from the viaopening 218. The stripping of the remainingplanarization material 224 is performed by either a chemical wet etching process or a chemical ashing process that is selective in removing theplanarization material 224 from the structure. - After stripping of the remaining
planarization material 224, a portion of thedielectric liner layer 222 is selectively removed. As shown inFIG. 8 , the selective removing process only removes the portion of thedielectric liner layer 222 at the viagouging feature 220 located at the bottom the viaopening 218, while keeping the portion of thedielectric liner layer 222 at sidewalls of the viaopening 218 unremoved. - The selective removing process includes, but is not limited to, a plasma stripping process, a wet chemical etching process, and an ion-sputtering process with a gas resource. When the selective removing process is a plasma stripping process, the plasma stripping process includes a hydrogen plasma stripping process. When the selective removing process is a wet chemical etching process, the process includes a wet chemical etching process with a dilute HF solution, a dilute HCl solution, a H2O2 solution, or a combination comprising two or more of the foregoing solutions. When the selective removing process is an ion-sputtering process with a gas resource, the gas source may include Ar, He, Xe, Ne, Kr, Rn, N2 or H2.
- After the portion of the
dielectric liner layer 222 at the viagouging feature 220 located at the bottom the viaopening 218 is selectively removed, adiffusion barrier layer 232 is formed on all exposed surfaces of the structure, including the exposed surfaces of theline openings opening 218 and the via gouging feature 220 (FIG. 9 ). Thediffusion barrier layer 232 may include, but is not limited to, Ta, TaN, Ti, TiN, Ru, RuN, RuTa, RuTaN, W, WN, Co, CoW, Mn, MnO, a combination comprising two or more of the foregoing materials or any other material that can serve as a barrier to prevent a conductive material from diffusing there through. Combinations of these materials are also contemplated to form a multilayered stacked diffusion barrier layer. - The
diffusion barrier layer 232 is formed utilizing a deposition process such as, for example, ALD, CVD, PECVD, PVD, sputtering, chemical solution deposition, or plating. It is noted that thediffusion barrier layer 232 is continuously present in theline openings - The thickness of the
diffusion barrier layer 232 may vary depending on the number of material layers within the barrier layer, the technique used in forming the same as well as the material of the diffusion barrier layer itself. Typically, thediffusion barrier layer 232 has a thickness from about 4 nm to about 40 nm, with a thickness from about 7 nm to about 20 nm being more typical. - An optional adhesion/plating seed layer (not shown) can be located atop the
diffusion barrier layer 232. The optional adhesion/plating seed layer is comprised of a metal or metal alloy from Group VIIIA of the Periodic Table of Elements. Examples of suitable Group VIIIA elements for the adhesion/plating seed layer include, but are not limited to, Ru, TaRu, Ir, Rh, Pt, Pd, Co and alloys thereof. In some embodiments, it is preferred to use Ru, Ir, Co or Rh as the adhesion/plating seed layer. - The adhesion/plating seed layer is formed by a conventional deposition process including, for example, CVD, PECVD, ALD, plating, sputtering and PVD. The thickness of the adhesion/plating seed layer may vary depending on number of factors including, for example, the compositional material of the adhesion/plating seed layer and the technique that was used in forming the same. Typically, the adhesion/plating seed layer has a thickness from about 0.5 nm to about 10 nm, with a thickness of about 0.5 nm to about 6 nm being more typical.
- In
FIG. 10 , theline openings opening 218 as well as the viagouging feature 220 are filled with a secondconductive material 234. The secondconductive material 234 may be the same or different, preferably the same, conductive material as that of the firstconductive material 206. Preferably, the secondconductive material 234 is Cu, Al, W or an alloy of two or more of the foregoing metals. More preferably, the secondconductive material 234 is Cu or AlCu alloy. It is noted that when polysilicon is used as theconductive material 234, the adhesion/plating seed layer is typically not used. On the other hand, when other types of conductive materials are used as theconductive material 234, the adhesion/plating seed layer is typically used. The secondconductive material 234 is formed utilizing the same deposition processing as described above in forming the firstconductive material 206. As shown, the secondconductive material 234 extends above the upper surface of thesecond dielectric layer 214. - Next, the structure shown in
FIG. 10 is subjected to a planarization which provides the planar interconnect structure shown inFIG. 11 . The planarization process removes various materials that are located atop thesecond dielectric layer 214 of theupper interconnect level 212. Chemical mechanical polishing (CMP) and/or grinding may be used in this step of the present invention. - While the present invention has been particularly shown and described with respect to preferred embodiments, it will be understood by those skilled in the art that the foregoing and other changes in forms and details may be made without departing from the spirit and scope of the invention. It is therefore intended that the present invention not be limited to the exact forms and details described and illustrated but fall within the scope of the appended claims.
Claims (16)
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US12/608,377 Expired - Fee Related US8232196B2 (en) | 2009-10-29 | 2009-10-29 | Interconnect structure having a via with a via gouging feature and dielectric liner sidewalls for BEOL integration |
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US7122462B2 (en) | 2003-11-21 | 2006-10-17 | International Business Machines Corporation | Back end interconnect with a shaped interface |
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US7488679B2 (en) | 2006-07-31 | 2009-02-10 | International Business Machines Corporation | Interconnect structure and process of making the same |
JP5103914B2 (en) * | 2007-01-31 | 2012-12-19 | 富士通セミコンダクター株式会社 | Semiconductor device manufacturing method and semiconductor device |
US7867895B2 (en) | 2007-09-20 | 2011-01-11 | International Business Machines Corporation | Method of fabricating improved interconnect structure with a via gouging feature absent profile damage to the interconnect dielectric |
US7846834B2 (en) | 2008-02-04 | 2010-12-07 | International Business Machines Corporation | Interconnect structure and method for Cu/ultra low k integration |
-
2009
- 2009-10-29 US US12/608,377 patent/US8232196B2/en not_active Expired - Fee Related
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2012
- 2012-04-17 US US13/448,780 patent/US20120199976A1/en not_active Abandoned
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US10586732B2 (en) | 2016-06-30 | 2020-03-10 | International Business Machines Corporation | Via cleaning to reduce resistance |
US11557507B2 (en) | 2016-06-30 | 2023-01-17 | International Business Machines Corporation | Via cleaning to reduce resistance |
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US20110100697A1 (en) | 2011-05-05 |
US8232196B2 (en) | 2012-07-31 |
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