The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generation of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (e.g., the number of interconnected devices per chip area) has generally increased while geometry size (e.g., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs.
Accompanying the scaling down of devices, manufacturers have begun using new and different materials and/or combination of materials to facilitate the scaling down of devices. Scaling down, alone and in combination with new and different materials, has also led to challenges that may not have been presented by previous generations at larger geometries.
Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “over,” “on,” “top,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.
Generally, the present disclosure provides example embodiments relating to conductive features, such as metal contacts, vias, lines, etc., and methods for forming those conductive features. Example embodiments described herein are described in the context of forming conductive features in middle of the line (MOL) processing for a fin field effect transistor (FinFET). Other embodiments may be implemented in other contexts, such as forming conductive features in back end of the line (BEOL), or with different devices, such as planar field effect transistors (FETs), vertical gate all around (VGAA) FETs, horizontal gate all around (HGAA) FETs, bipolar junction transistors (BJTs), diodes, capacitors, inductors, resistors, etc. Implementations of some aspects of the present disclosure may be used in other processes and/or in other devices.
Some variation of the example methods and structures are described. A person having ordinary skill in the art will readily understand other modifications that may be made that are contemplated within the scope of other embodiments. Although method embodiments may be described in a particular order, various other method embodiments may be performed in any logical order and may include fewer or more steps than what is described herein. In some figures, some reference numbers of components or features illustrated therein may be omitted to avoid obscuring other components or features; this is for ease of depicting the figures.
The semiconductor device structure 100 includes first and second fins 46 formed on a semiconductor substrate 42, with respective isolation regions 44 on the semiconductor substrate 42 between neighboring fins 46. First and second dummy gate stacks are along respective sidewalls of and over the fins 46. The first and second dummy gate stacks each include an interfacial dielectric 48, a dummy gate 50, and a mask 52.
The semiconductor substrate 42 may be or include a bulk semiconductor substrate, a semiconductor-on-insulator (SOI) substrate, or the like, which may be doped (e.g., with a p-type or an n-type dopant) or undoped. In some embodiments, the semiconductor material of the semiconductor substrate 42 may include an elemental semiconductor such as silicon (Si) or germanium (Ge); a compound semiconductor; an alloy semiconductor; or a combination thereof.
The fins 46 are formed in the semiconductor substrate 42. For example, the semiconductor substrate 42 may be etched, such as by appropriate photolithography and etch process, such that trenches are formed between neighboring pairs of fins 46 and such that the fins 46 protrude from the semiconductor substrate 42. Isolation regions 44 are formed with each being in a corresponding trench. The isolation regions 44 may include or be an insulating material such as an oxide (such as silicon oxide), a nitride, the like, or a combination thereof. The insulating material may then be recessed after being deposited to form the isolation regions 44. The insulating material is recessed using an acceptable etch process such that the fins 46 protrude from between neighboring isolation regions 44, which may, at least in part, thereby delineate the fins 46 as active areas on the semiconductor substrate 42. The fins 46 may be formed by other processes, and may include homoepitaxial and/or heteroepitaxial structures, for example.
The dummy gate stacks are formed on the fins 46. In a replacement gate process as described herein, the interfacial dielectrics 48, dummy gates 50, and masks 52 for the dummy gate stacks may be formed by sequentially forming respective layers by appropriate deposition processes, for example, and then patterning those layers into the dummy gate stacks by appropriate photolithography and etch processes. For example, the interfacial dielectrics 48 may include or be silicon oxide, silicon nitride, the like, or multilayers thereof. The dummy gates 50 may include or be silicon (e.g., polysilicon) or another material. The masks 52 may include or be silicon nitride, silicon oxynitride, silicon carbon nitride, the like, or a combination thereof.
In other examples, instead of and/or in addition to the dummy gate stacks, the gate stacks can be operational gate stacks (or more generally, gate structures) in a gate-first process. In a gate-first process, the interfacial dielectric 48 may be a gate dielectric layer, and the dummy gate 50 may be a gate electrode. The gate dielectric layers, gate electrodes, and masks 52 for the operational gate stacks may be formed by sequentially forming respective layers by appropriate deposition processes, and then patterning those layers into the gate stacks by appropriate photolithography and etch processes. For example, the gate dielectric layers may include or be silicon oxide, silicon nitride, a high-k dielectric material, the like, or multilayers thereof. A high-k dielectric material may have a k value greater than about 7.0, and may include a metal oxide of or a metal silicate of hafnium (Hf), aluminum (Al), zirconium (Zr), lanthanum (La), magnesium (Mg), barium (Ba), titanium (Ti), lead (Pb), multilayers thereof, or a combination thereof. The gate electrodes may include or be silicon (e.g., polysilicon, which may be doped or undoped), a metal-containing material (such as titanium, tungsten, aluminum, ruthenium, or the like), a combination thereof (such as a silicide (which may be subsequently formed), or multiple layers thereof. The masks 52 may include or be silicon nitride, silicon oxynitride, silicon carbon nitride, the like, or a combination thereof.
Recesses are then formed in the fins 46 on opposing sides of the dummy gate stacks (e.g., using the dummy gate stacks and gate spacers 54 as a mask) by an etch process. The etch process can be isotropic or anisotropic, or further, may be selective with respect to one or more crystalline planes of the semiconductor substrate 42. Hence, the recesses can have various cross-sectional profiles based on the etch process implemented. The epitaxy source/drain regions 56 are formed in the recesses. The epitaxy source/drain regions 56 may include or be silicon germanium, silicon carbide, silicon phosphorus, silicon carbon phosphorus, pure or substantially pure germanium, a III-V compound semiconductor, a II-VI compound semiconductor, or the like. The epitaxy source/drain regions 56 may be formed in the recesses by an appropriate epitaxial growth or deposition process. In some examples, epitaxy source/drain regions 56 can be raised with respect to the fin 46, and can have facets, which may correspond to crystalline planes of the semiconductor substrate 42.
A person having ordinary skill in the art will also readily understand that the recessing and epitaxial growth may be omitted, and that source/drain regions may be formed by implanting dopants into the fins 46 using the dummy gate stacks and gate spacers 54 as masks. In some examples where epitaxy source/drain regions 56 are implemented, the epitaxy source/drain regions 56 may also be doped, such as by in situ doping during epitaxial growth and/or by implanting dopants into the epitaxy source/drain regions 56 after epitaxial growth. Hence, a source/drain region may be delineated by doping (e.g., by implantation and/or in situ during epitaxial growth, if appropriate) and/or by epitaxial growth, if appropriate, which may further delineate the active area in which the source/drain region is delineated.
The CESL 60 is conformally deposited, by an appropriate deposition process, on surfaces of the epitaxy source/drain regions 56, sidewalls and top surfaces of the gate spacers 54, top surfaces of the masks 52, and top surfaces of the isolation regions 44. Generally, an etch stop layer (ESL) can provide a mechanism to stop an etch process when forming, e.g., contacts or vias. An ESL may be formed of a dielectric material having a different etch selectively from adjacent layers or components. The CESL 60 may include or be silicon nitride, silicon carbon nitride, silicon carbon oxide, carbon nitride, the like, or a combination thereof.
The dielectric layer 62 is deposited, by an appropriate deposition process, on the CESL 60. In some embodiments, the dielectric layer 62 is a first interlayer dielectric (ILD). The dielectric layer 62 may include or be silicon dioxide, a low-k dielectric material (e.g., a material having a dielectric constant lower than silicon dioxide), silicon oxynitride, phosphosilicate glass (PSG), borosilicate glass (BSG), borophosphosilicate glass (BPSG), undoped silicate glass (USG), fluorinated silicate glass (FSG), organosilicate glasses (OSG), SiOxCy, spin-on-glass, spin-on-polymers, silicon carbon material, a compound thereof, a composite thereof, the like, or a combination thereof.
The dielectric layer 62 may be planarized after being deposited, such as by a chemical mechanical polishing (CMP). In a gate-first process, a top surface of the dielectric layer 62 may be above the upper portions of the CESL 60 and the gate stacks, and processing described below with respect to
With the dummy gates 50 exposed through the dielectric layer 62 and the CESL 60, the dummy gates 50 are removed, such as by one or more etch processes. The dummy gates 50 may be removed by an etch process selective to the dummy gates 50, where the interfacial dielectrics 48 act as ESLs, and subsequently, the interfacial dielectrics 48 can optionally be removed by a different etch process selective to the interfacial dielectrics 48. Recesses are formed between gate spacers 54 where the dummy gate stacks are removed, and channel regions of the fins 46 are exposed through the recesses.
The replacement gate structures are formed in the recesses where the dummy gate stacks were removed. The replacement gate structures each include, as illustrated, an interfacial dielectric 70, a gate dielectric layer 72, one or more optional conformal layers 74, and a gate conductive fill material 76. The interfacial dielectric 70 is formed on sidewalls and top surfaces of the fins 46 along the channel regions. The interfacial dielectric 70 can be, for example, the interfacial dielectric 48 if not removed, an oxide (e.g., silicon oxide) formed by thermal or chemical oxidation of the fin 46, and/or an oxide (e.g., silicon oxide), nitride (e.g., silicon nitride), and/or another dielectric layer.
The gate dielectric layer 72 can be conformally deposited in the recesses where dummy gate stacks were removed (e.g., on top surfaces of the isolation regions 44, on the interfacial dielectric 70, and sidewalls of the gate spacers 54) and on the top surfaces of the dielectric layer 62, the CESL 60, and gate spacers 54. The gate dielectric layer 72 can be or include silicon oxide, silicon nitride, a high-k dielectric material (examples of which are provided above), multilayers thereof, or other dielectric material.
Then, the one or more optional conformal layers 74 can be conformally (and sequentially, if more than one) deposited on the gate dielectric layer 72. The one or more optional conformal layers 74 can include one or more barrier and/or capping layers and one or more work-function tuning layers. The one or more barrier and/or capping layers can include a nitride, silicon nitride, carbon nitride, and/or aluminum nitride of tantalum and/or titanium; a nitride, carbon nitride, and/or carbide of tungsten; the like; or a combination thereof. The one or more work-function tuning layer may include or be a nitride, silicon nitride, carbon nitride, aluminum nitride, aluminum oxide, and/or aluminum carbide of titanium and/or tantalum; a nitride, carbon nitride, and/or carbide of tungsten; cobalt; platinum; the like; or a combination thereof.
A layer for the gate conductive fill material 76 is formed over the one or more optional conformal layers 74 (e.g., over the one or more work-function tuning layers), if implemented, and/or the gate dielectric layer 72. The layer for the gate conductive fill material 76 can fill remaining recesses where the dummy gate stacks were removed. The layer for the gate conductive fill material 76 may be or include a metal-containing material such as tungsten, cobalt, aluminum, ruthenium, copper, multi-layers thereof, a combination thereof, or the like. Portions of the layer for the gate conductive fill material 76, one or more optional conformal layers 74, and gate dielectric layer 72 above the top surfaces of the dielectric layer 62, the CESL 60, and gate spacers 54 are removed, such as by a CMP. The replacement gate structures including the gate conductive fill material 76, one or more optional conformal layers 74, gate dielectric layer 72, and interfacial dielectric 70 may therefore be formed as illustrated in
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In some embodiments, the metal layer 94 is treated to form a nitride layer 96, as shown in
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In some embodiments, the PVD process to form the metal liner 99 may be a DC self-ionized PVD process. For example, the PVD process is performed in a process chamber with a chamber pressure ranging from about 0 mTorr to about 50 mTorr. The processing temperature ranges from about 20 degrees Celsius to about 450 degrees Celsius. The plasma source power (DC) ranges from about 1 kW to about 50 kW, and a plasma bias power ranges from about 0 kW to about 2 kW. The process gases may include Ar, Kr, or other suitable gases. The electro-magnets may be pull in or pull out for ion directional control.
In some embodiments, the PVD process to form the metal liner 99 may be an RF/DC PVD process. For example, the PVD process is performed in a process chamber with a chamber pressure ranging from about 0 mTorr to about 600 mTorr. The processing temperature ranges from about 20 degrees Celsius to about 450 degrees Celsius. The plasma source power (DC) ranges from about 0 W to about 100 W, the plasma source power (RF) ranges from about 1 kW to about 7 kW, and a plasma bias power ranges from about 0 W to about 200 W. The process gases may include Ar, Kr, or other suitable gases.
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In some embodiments, the PVD process to form the metal cap 108 may be a DC self-ionized PVD process. For example, the PVD process is performed in a process chamber with a chamber pressure ranging from about 0 mTorr to about 50 mTorr. The processing temperature ranges from about 20 degrees Celsius to about 450 degrees Celsius. The plasma source power (DC) ranges from about 1 kW to about 50 kW, and a plasma bias power ranges from about 0 kW to about 2 kW. The process gases may include Ar, Kr, or other suitable gases. The electro-magnets may be pull in or pull out for ion directional control.
In some embodiments, the PVD process to form the metal cap 108 may be an RF/DC PVD process. For example, the PVD process is performed in a process chamber with a chamber pressure ranging from about 0 mTorr to about 600 mTorr. The processing temperature ranges from about 20 degrees Celsius to about 450 degrees Celsius. The plasma source power (DC) ranges from about 0 W to about 100 W, the plasma source power (RF) ranges from about 1 kW to about 7 kW, and a plasma bias power ranges from about 0 W to about 200 W. The process gases may include Ar, Kr, or other suitable gases.
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The top surface of the conductive feature 110, which is the top surface of the metal cap 108, is free of a barrier layer, such as TiN or TaN. The material of the metal cap 108 has a lower electrical resistivity compared to TiN or TaN. As a result, contact resistance of the conductive feature 110 is reduced compared to conventional conductive features having TiN or TaN barrier layer as part of the top surface. The metal cap 108 provides a single grain interface to reduce interface resistance between a conductive feature disposed on the conductive feature 110 and the conductive feature 110. Furthermore, the metal cap 108 is seamless, which further reduces electrical resistance.
The present disclosure in various embodiment provide the semiconductor device structure 100 and the methods of forming the same. In some embodiments, the semiconductor device structure 100 includes a conductive feature 120. The conductive feature 120 includes a bottom portion 112 and a metal cap 108 disposed on the bottom portion 112. The bottom portion 112 includes a metal liner 99 and a metal fill 102 in contact and surrounded by the metal liner 99. Some embodiments may achieve advantages. For example, the contact resistance of the conductive feature 120 is reduced because the top surface of the conductive feature 120 is barrier free. Furthermore, the method to form the conductive feature 120 is simple and is a low-cost method.
An embodiment is a semiconductor device structure. The structure includes a dielectric layer disposed over an epitaxy source/drain region and a conductive feature disposed in the dielectric layer. The conductive feature includes a metal liner including a first material and a metal fill surrounded by the metal liner. The metal fill includes the first material having a first grain size. The conductive feature further includes a metal cap disposed on the metal liner and the metal fill, and the metal cap includes the first material having a second grain size different from the first grain size.
Another embodiment is a semiconductor device structure. The structure includes a gate conductive fill material, an epitaxy source/drain region disposed on one side of the gate conductive fill material, a first dielectric layer disposed over the epitaxy source/drain region, a dielectric layer disposed over the first dielectric layer, and a conductive feature disposed in the first dielectric layer and the second dielectric layer. The conductive feature includes a metal liner disposed in the first dielectric layer, a metal fill in contact with the metal liner, and a seam located in the metal fill. The structure further includes a metal cap disposed on the metal liner and the metal fill, and the metal cap is seamless.
A further embodiment is a method. The method includes forming a first opening in a dielectric layer disposed over an epitaxy source/drain region, forming a metal liner in the first opening by a first process, and forming a metal fill to fill the first opening by a second process different from the first process. A seam is formed in the metal fill. The method further includes recessing the metal liner and the metal fill to form a second opening and forming a metal cap to fill the second opening with a third process different from the second process. The metal cap is seamless.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.