The semiconductor integrated circuit (IC) industry has experienced rapid growth. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., 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. Such scaling down has also increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC manufacturing are needed.
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,” “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. As used herein, “around,” “about,” “approximately,” or “substantially” shall generally mean within 20 percent, or within 10 percent, or within 5 percent of a given value or range. Numerical quantities given herein are approximate, meaning that the term “around,” “about,” “approximately,” or “substantially” can be inferred if not expressly stated.
Structures of the GAA device or the nanosheet device may be patterned by any suitable method. For example, the structures may be patterned using one or more photolithography processes, including double-patterning or multi-patterning processes. Generally, double-patterning or multi-patterning processes combine photolithography and self-aligned processes, allowing patterns to be created that have, for example, pitches smaller than what is otherwise obtainable using a single, direct photolithography process. For example, in one embodiment, a sacrificial layer is formed over a substrate and patterned using a photolithography process. Spacers are formed alongside the patterned sacrificial layer using a self-aligned process. The sacrificial layer is then removed, and the remaining spacers may then be used to pattern the GAA structure.
As with the other method embodiments and exemplary devices discussed herein, it is understood that parts of the semiconductor device may be fabricated by a CMOS technology process flow, and thus some processes are only briefly described herein. Further, the exemplary semiconductor device may include various other devices and features, such as other types of devices such as additional transistors, bipolar junction transistors, resistors, capacitors, inductors, diodes, fuses, static random access memory (SRAM) and/or other logic circuits, etc., but is simplified for a better understanding of the concepts of the present disclosure. In some embodiments, the exemplary semiconductor device includes a plurality of semiconductor devices (e.g., transistors), including PFETs, NFETs, etc., which may be interconnected.
Referring to
The epitaxial stack 120 includes epitaxial layers 122 of a first composition interposed by epitaxial layers 124 of a second composition. The first and second compositions can be different. In some embodiments, the epitaxial layers 122 are SiGe and the epitaxial layers 124 are silicon (Si). However, other embodiments are possible including those that provide for a first composition and a second composition having different oxidation rates and/or etch selectivity. In some embodiments, the epitaxial layers 122 include SiGe and where the epitaxial layers 124 include Si, the Si oxidation rate of the epitaxial layers 124 is less than the SiGe oxidation rate of the epitaxial layers 122.
The epitaxial layers 124 or portions thereof may form nanosheet channel(s) of the multi-gate transistor. The term nanosheet is used herein to designate any material portion with nanoscale, or even microscale dimensions, and having an elongate shape, regardless of the cross-sectional shape of this portion. Thus, this term designates both circular and substantially circular cross-section elongate material portions, and beam or bar-shaped material portions including for example a cylindrical in shape or substantially rectangular cross-section. The use of the epitaxial layers 124 to define a channel or channels of a device is further discussed below. It is noted that three layers of the epitaxial layers 122 and three layers of the epitaxial layers 124 are alternately arranged as illustrated in
The epitaxial layers 122 in channel regions(s) may eventually be removed and serve to define a vertical distance between adjacent channel region(s) for a subsequently-formed multi-gate device. Accordingly, the epitaxial layers 122 may also be referred to as sacrificial layers, and epitaxial layers 124 may also be referred to as channel layers.
By way of example, epitaxial growth of the layers of the stack 120 may be performed by a molecular beam epitaxy (MBE) process, a metalorganic chemical vapor deposition (MOCVD) process, and/or other suitable epitaxial growth processes. In some embodiments, the epitaxially grown layers such as, the epitaxial layers 324 include the same material as the substrate 110. In some embodiments, the epitaxially grown layers 122 and 124 include a different material than the substrate 110. As stated above, in at least some examples, the epitaxial layers 122 include an epitaxially grown silicon germanium (SiGe) layer and the epitaxial layers 124 include an epitaxially grown silicon (Si) layer. Alternatively, in some embodiments, either of the epitaxial layers 122 and 124 may include other materials such as germanium, a compound semiconductor such as silicon carbide, gallium arsenide, gallium phosphide, indium phosphide, indium arsenide, and/or indium antimonide, an alloy semiconductor such as SiGe, GaAsP, AlInAs, AlGaAs, InGaAs, GaInP, and/or GaInAsP, or combinations thereof. As discussed, the materials of the epitaxial layers 122 and 124 may be chosen based on providing differing oxidation and/or etching selectivity properties. In some embodiments, the epitaxial layers 122 and 124 are substantially dopant-free (i.e., having an extrinsic dopant concentration from about 0 cm−3 to about 1×1018 cm−3), where for example, no intentional doping is performed during the epitaxial growth process.
Reference is made to
As illustrated in
The fins FS may subsequently be fabricated using suitable processes including photolithography and etch processes. The photolithography process may include forming a photoresist layer (not shown) over the HM layer 910, exposing the photoresist to a pattern, performing post-exposure bake processes, and developing the resist to form a patterned mask including the resist. In some embodiments, patterning the resist to form the patterned mask element may be performed using an electron beam (e-beam) lithography process or an extreme ultraviolet (EUV) lithography process using light in EUV region, having a wavelength of, for example, about 1-100 nm. The patterned mask may then be used to protect regions of the substrate 110, and layers formed thereupon, while an etch process forms trenches T1 in unprotected regions through the HM layer 910, through the epitaxial stack 120, and into the substrate 110, thereby leaving the plurality of extending fins FS. The trenches T1 may be etched using a dry etch (e.g., reactive ion etching), a wet etch, and/or combination thereof. The photoresist layer may be removed by suitable stripping process after the etching processes.
Reference is made to
Reference is made to
By way of example and not limitation, a dielectric layer is first deposited over the substrate 110, filling the trenches T1′ with the dielectric material. In some embodiments, the dielectric layer may include silicon oxide, silicon nitride, silicon oxynitride, fluorine-doped silicate glass (FSG), a low-k dielectric, combinations thereof, and/or other suitable materials. In various examples, the dielectric layer may be deposited by a CVD process, a subatmospheric CVD (SACVD) process, a flowable CVD process, an ALD process, a physical vapor deposition (PVD) process, and/or other suitable process. In some embodiments, the dielectric layer (and subsequently formed STI features 130) may include a multi-layer structure, for example, having one or more liner layers.
In some embodiments of forming the isolation (STI) features 130, after deposition of the dielectric layer, the deposited dielectric material is thinned and planarized, for example by a chemical mechanical polishing (CMP) process. In some embodiments, the HM layer 910 (as illustrated
Reference is made to
The dummy gate structures 140 may include gate lines 140A and 140B extending along substantially parallel to each other, for example, substantially long a direction Y. The gate lines 140A are at least partially over the fins FS, for example, extending across the fins FS. The portion of the fins FS underlying the gate lines 140A may be referred to as the channel region. The gate lines 140A may also define a source/drain (S/D) region of the fins FS, for example, the regions of the fin FS adjacent and on opposing sides of the channel region. The gate lines 140B are entirely over the STI features 130 and not over the fins. For example, the gate lines 140B does not extend across the fins FS. The gate lines 140A and 140B may have a substantial same line width Gw in a range from about 1 nanometer to about 50 nanometers. The gate lines 140A and 140B are spaced apart from each other by a substantially fixed distance Gd. The distance Gd may be in a range from about 1 nanometer to about 100 nanometers. Stated differently, every two adjacent gate lines 140A and 140B have a center-to-center line pitch Gp, which is substantially equal to a sum of the line width Gw and the distance Gd.
In a process of fabricating a semiconductor device, one or more wet chemical process during the fabrication process may consume oxides in the STI features 130 and provide strong surface tension force on poly lines (e.g., gate lines 140A and 140B). In some cases where the adjacent two gate lines 140B are structurally separated (or disconnected), the gate lines 140B may be unstable and collapse easily as a result of the consumed STI features 130 and the strong surface tension force on poly lines. For example, the wet chemical process may include one or more cleaning processes (e.g., using HF, diluted water, or the like). HF may react with silicon oxide, and yield water and H2SiF6, thereby consume oxides in the STI features 130. One of the cleaning processes may be performed after a source/drain recess etching process as illustrated in
In some embodiments of the present disclosure, the dummy gate structures 140 include bridge portions 140C extending from a sidewall of at least one gate lines 140B and connecting the gate lines 140B to each other along a direction X perpendicular to the direction Y. The bridge portions 140C may extend through plural gate lines 140B from the top view of
Each of the bridge portions 140C may have a width Cxw measured along the direction X and a width Cyw measured along the direction X. The width Cxw may be in a range from about one times the line pitch Gp to about 7 times the line pitch Gp, or from about two times the line pitch Gp to about 7 times the line pitch Gp. For example, as the figure shows, the width Cxw of the bridge portions 140C may be substantially equal to a sum of the line width Gw and the line pitch Gp, or approximately the line pitch Gp. If the width Cxw is less than one line pitch Gp, the bridge portions 140C may not connecting two gate lines 140B to each other. If the width Cxw is greater than about 7 times the line pitch Gp, the active areas (e.g., a length of the fins FS measured along the direction Y) may be shrunk. The width Cyw may be in a range from about 15 nanometers to about 45 nanometers. If the width Cyw is less than 15 nanometers, the bridge portions 140C may not provide enough mechanical support to the gate lines 140B to avoid collapse. For example, the width Cyw may be greater than the line width Gw of the gate lines 140A and 140B for provide good mechanical support. If the width Cyw is greater than about 45 nanometers, process loading effects (e.g., CMP loading effects) on the gate lines 140A may not be well compensated by the gate lines 140B.
In some embodiments, along the direction X, two adjacent bridge portions 140C have a center-to-center pitch Cxp therebetween. The pitch Cxp may be in a range from about 6 times the line pitch Gp to about 20 times the line pitch G. If the pitch Cxp is less than 6 times the line pitch Gp, there may be no enough space for the fins FS. If the pitch Cxp is greater than 20 times the line pitch Gp, the active area (e.g., a length of the fins FS measured along the direction Y) may be too large to achieve suitable device design. For example, along the direction X, two adjacent bridge portions 140C are spaced apart from each other by a distance Cxd, and the pitch Cxp is substantially equal to a sum of the width Cxw and the distance Cxd.
In some embodiments, along the direction Y, two adjacent bridge portions 140C have a center-to-center pitch Cyp therebetween. The pitch Cyp may be in a range from about 0.4 micrometers to about 5 micrometers. If the pitch Cyp is less than about 0.4 micrometers, there may be no enough space to receive metals in later source/drain contact formation step. If the pitch Cyp is greater than about 5 micrometers, the bridge portions 140C may not provide enough support to the gate line 140B to avoid collapse. For example, along the direction Y, two adjacent bridge portions 140C are spaced apart from each other by a distance Cyd, and the pitch Cyp is substantially equal to a sum of the width Cyw and the distance Cyd. The distance Cyd may be in a range from about 300 nanometers to about 5000 nanometers. If the distance Cyd is less than about 300 nanometers, there may be no enough space to receive metals in later source/drain contact formation step. If the pitch Cyp is greater than about 5000 nanometers, the bridge portions 140C may not provide enough support to the gate line 140B to avoid collapse.
In some embodiment, the fins FS may have a length Fxw along the direction X and a width Fyw along the direction Y. The length Fxw may be equal to or greater than about four times the line pitch Gp for achieving suitable device design. In some embodiments, the width Cyw of the bridge portions 140C may equal to, greater than, or less than the width Fyw of the fins FS. The fins FS may have a vertical center-to-center pitch Fyp therebetween, and the pitch Fyp is less than the pitch Cyp of the bridge portions 140C for high device density. In some embodiment, as shown in
In the illustrated embodiments, the formation of the gate structures 140 first forms a dummy gate dielectric layer 142 over the fins FS. In some embodiments, the dummy gate dielectric layer 142 may include SiO2, silicon nitride, a high-k dielectric material and/or other suitable material. In various examples, the dummy gate dielectric layer 142 may be deposited by a CVD process, a subatmospheric CVD (SACVD) process, a flowable CVD process, an ALD process, a PVD process, or other suitable process. By way of example, the dummy gate dielectric layer 142 may be used to prevent damages to the fins FS by subsequent processes (e.g., subsequent formation of the dummy gate structure). Subsequently, the formation of the gate structures 140 forms a dummy gate electrode layer 144 and a hard mask 146 which may include multiple layers (e.g., an oxide layer and a nitride layer). In some embodiments, the dummy gate structure 140 is formed by various process steps such as layer deposition, patterning, etching, as well as other suitable processing steps. Exemplary layer deposition processes include CVD (including both low-pressure CVD and plasma-enhanced CVD), PVD, ALD, thermal oxidation, e-beam evaporation, or other suitable deposition techniques, or combinations thereof. In forming the gate structure for example, the patterning process includes a lithography process (e.g., photolithography or e-beam lithography) which may further include photoresist coating (e.g., spin-on coating), soft baking, mask aligning, exposure, post-exposure baking, photoresist developing, rinsing, drying (e.g., spin-drying and/or hard baking), other suitable lithography techniques, and/or combinations thereof. In some embodiments, the etching process may include dry etching (e.g., RIE etching), wet etching, and/or other etching methods. In some embodiments, the dummy gate electrode layer 144 may include polycrystalline silicon (polysilicon). In some embodiments, the hard mask 146 includes an oxide layer such as a pad oxide layer that may include SiO2, and a nitride layer such as a pad nitride layer that may include Si3N4 and/or silicon oxynitride. In some embodiments, after patterning the dummy gate electrode layer 144, the dummy gate dielectric layer 142 is removed from the S/D regions of the fins FS. The etch process may include a wet etch, a dry etch, and/or a combination thereof. The etch process is chosen to selectively etch the dummy gate dielectric layer 142 without substantially etching the fins FS, the dummy gate electrode layer 144, and the hard mask 146.
After the formation of the dummy gate structures 140, gate spacers 150 are formed on sidewalls of the dummy gate structures 140. For example, a spacer material layer is conformally deposited on the substrate using processes such as, CVD process, a subatmospheric CVD (SACVD) process, a flowable CVD process, an ALD process, a PVD process, or other suitable process. The spacer material layer may include a dielectric material such as silicon oxide, silicon nitride, silicon carbide, silicon oxynitride, SiCN films, silicon oxycarbide, SiOCN films, and/or combinations thereof. The spacer material layer is subsequently etched back to form the gate spacers 150. For example, an anisotropic etching process is performed on the deposited spacer material layer to expose portions of the fins FS not covered by the dummy gate structures 140 (e.g., in source/drain regions of the fins FS). Portions of the spacer material layer directly above the dummy gate structures 140 may be completely removed by this anisotropic etching process. In some embodiments, the spacer material layer includes multiple layers, and therefore the gate spacers 150 may be multi-layer structures.
Reference is made to
The, end surfaces of the sacrificial layers 122 are laterally or horizontally recessed by using suitable selective etching process, resulting in lateral recesses R2 each vertically between corresponding channel layers 124. By way of example and not limitation, the sacrificial layers 122 are SiGe and the channel layers 124 are silicon allowing for the selective etching of the sacrificial layers 122. In some embodiments, the selective wet etching includes an APM etch (e.g., ammonia hydroxide-hydrogen peroxide-water mixture) that etches SiGe at a faster etch rate than it etches Si. In some embodiments, the selective etching includes SiGe oxidation followed by a SiGeOx removal. For example, the oxidation may be provided by O3 clean and then SiGeOx removed by an etchant such as NH4OH that selectively etches SiGeOx at a faster etch rate than it etches Si. Moreover, because oxidation rate of Si is much lower (sometimes 30 times lower) than oxidation rate of SiGe, the channel layers 324 is not significantly etched by the process of laterally recessing the sacrificial layers 322. As a result, the channel layers 124 laterally extend past opposite end surfaces of the sacrificial layers 122.
Inner spacers 160 are subsequently formed on opposite end surfaces of the laterally recessed sacrificial layers 122. In some embodiments, an inner spacer material layer is formed to fill the recesses R2. The inner spacer material layer may be a low-K dielectric material, such as SiO2, SiN, SiCN, or SiOCN, and may be formed by a suitable deposition method, such as ALD. After the deposition of the inner spacer material layer, an anisotropic etching process may be performed to trim the deposited inner spacer material, such that only portions of the deposited inner spacer material that fill the recesses R2 left by the lateral etching of the sacrificial layers 122 are left. After the trimming process, the remaining portions of the deposited inner spacer material are denoted as inner spacers 160. The inner spacers 160 serve to isolate metal gates from source/drain regions formed in subsequent processing. In the example of
In some embodiments, the etching process of forming the recess R1 and R2 may consume oxides of the STI features 130. In absence of the bridge portion 140C, the poly line (e.g., the gate lines 140B) may collapse due to the oxide consume and strong surface tension on the poly lines.
In some embodiments of the present disclosure, by using the bridge portion 140C providing structural support between the gate lines 140B, the stability of the poly lines is improved, thereby avoiding poly collapse.
Reference is made to
In some embodiments, the source/drain epitaxial structures 170 may include Ge, Si, GaAs, AlGaAs, SiGe, GaAsP, SiP, or other suitable material. The source/drain epitaxial structures 290S/290D may be in-situ doped during the epitaxial process by introducing doping species including: p-type dopants, such as boron; n-type dopants, such as phosphorus or arsenic; and/or other suitable dopants including combinations thereof. If the source/drain epitaxial structures 170 are not in-situ doped, an implantation process (i.e., a junction implant process) is performed to dope the source/drain epitaxial structures 170. In some exemplary embodiments, the source/drain epitaxial structures 170 in an NFET device include SiP, while those in a PFET device include GeSnB and/or SiGeSnB.
A dielectric material 180 is formed over the substrate 110 and filling the space between the dummy gate structures 140. In some embodiments, the dielectric material 180 includes a contact etch stop layer (CESL) 182 and an interlayer dielectric (ILD) layer 184 formed in sequence. In some examples, the CESL 182 includes a silicon nitride layer, silicon oxide layer, a silicon oxynitride layer, and/or other suitable materials having a different etch selectivity than the ILD layer 184. The CESL 182 may be formed by plasma-enhanced chemical vapor deposition (PECVD) process and/or other suitable deposition or oxidation processes. The ILD layer 184 is then deposited over the CESL 182. In some embodiments, the ILD layer 184 includes materials such as tetraethylorthosilicate (TEOS) oxide, un-doped silicate glass, or doped silicon oxide such as borophosphosilicate glass (BPSG), fused silica glass (FSG), phosphosilicate glass (PSG), boron doped silicon glass (BSG), and/or other suitable dielectric materials having a different etch selectivity than the CESL 182. The ILD layer 184 may be deposited by a PECVD process or other suitable deposition technique. In some embodiments, after formation of the ILD layer 184, the semiconductor device may be subject to a high thermal budget process to anneal the ILD layer 184.
After depositing the ILD layer 184, a planarization process may be performed to remove excessive materials of the ILD layer 184. For example, a planarization process includes a chemical mechanical planarization (CMP) process which removes portions of the ILD layer 184 and the CESL layer 182 overlying the dummy gate structures 140 and planarizes a top surface of the semiconductor device. In some embodiments, the CMP process also removes the hard mask layer 146 in the dummy gate structures 140 (as shown in
Reference is made to
In some embodiments, the sacrificial layers 122 (referring to
Reference is made to
In various embodiments, the high-k/metal gate structure 190 includes a gate dielectric layer 192 formed around the nanosheets 124 and a gate metal layer 194 formed around the dielectric layer 192 and filling a remainder of gate trenches GT. Formation of the high-k/metal gate structures 190 may include one or more deposition processes to form various gate materials, followed by a CMP processes to remove excessive gate materials, resulting in the high-k/metal gate structures 190 having top surfaces level with a top surface of the dielectric material 180. Thus, transistors (e.g., GAA FET) are formed, and the high-k/metal gate structure 190 surrounds each of the nanosheets 124, and thus is referred to as a gate of the transistors (e.g., GAA FET).
The gate dielectric layer 192 may include an interfacial layer and a high-k gate dielectric layer over the interfacial layer. In some embodiments, the interfacial layer is silicon oxide formed on exposed surfaces of semiconductor materials in the gate trenches GT by using, for example, thermal oxidation, chemical oxidation, wet oxidation or the like. As a result, surface portions of the nanosheets 124 and the substrate 110 exposed in the gate trenches GT are oxidized into silicon oxide to form interfacial layer. In some embodiments, the high-k gate dielectric layer includes dielectric materials such as hafnium oxide (HfO2), hafnium silicon oxide (HfSiO), hafnium silicon oxynitride (HfSiON), hafnium tantalum oxide (HfTaO), hafnium titanium oxide (HfTiO), hafnium zirconium oxide (HfZrO), lanthanum oxide (LaO), zirconium oxide (ZrO), titanium oxide (TiO), tantalum oxide (Ta2O5), yttrium oxide (Y2O3), strontium titanium oxide (SrTiO3, STO), barium titanium oxide (BaTiO3, BTO), barium zirconium oxide (BaZrO), hafnium lanthanum oxide (HfLaO), lanthanum silicon oxide (LaSiO), aluminum silicon oxide (AlSiO), aluminum oxide (Al2O3), the like, or combinations thereof.
In some embodiments, the gate metal layer 194 includes one or more metal layers. For example, the gate metal layer 194 may include one or more work function metal layers stacked one over another and a fill metal filling up a remainder of gate trenches GT. The one or more work function metal layers in the gate metal layer 194 provide a suitable work function for the high-k/metal gate structures 310. For an n-type GAA FET, the gate metal layer 194 may include one or more n-type work function metal (N-metal) layers. The n-type work function metal may exemplarily include, but are not limited to, titanium aluminide (TiAl), titanium aluminium nitride (TiAlN), carbo-nitride tantalum (TaCN), hafnium (Hf), zirconium (Zr), titanium (Ti), tantalum (Ta), aluminum (Al), metal carbides (e.g., hafnium carbide (HfC), zirconium carbide (ZrC), titanium carbide (TiC), aluminum carbide (AlC)), aluminides, and/or other suitable materials. On the other hand, for a p-type GAA FET, the gate metal layer 194 may include one or more p-type work function metal (P-metal) layers. The p-type work function metal may exemplarily include, but are not limited to, titanium nitride (TiN), tungsten nitride (WN), tungsten (W), ruthenium (Ru), palladium (Pd), platinum (Pt), cobalt (Co), nickel (Ni), conductive metal oxides, and/or other suitable materials. In some embodiments, the fill metal in the gate metal layer 194 may exemplarily include, but are not limited to, tungsten, aluminum, copper, nickel, cobalt, titanium, tantalum, titanium nitride, tantalum nitride, nickel silicide, cobalt silicide, TaC, TaSiN, TaCN, TiAl, TiAlN, or other suitable materials.
The high-k/metal gate structures 190 may include gate lines 190A and 190B and bridge portions 190C, respectively corresponding to the dummy (or sacrificial) gate lines 140A and 140B and bridge portions 140C in
Reference is made to
Reference is made to
In some embodiments of the present disclosure, conductive features 220B and 220C may be formed on the STI features 130. The conductive features 220B and 220C and the source/drain contacts 220A may be formed by the same source/drain contact formation step. The conductive features 220B and 220C and the source/drain contacts 220A may include the same metal materials. The conductive features 220B and 220C may not be electrically connected with source/drain epitaxial structures 170. For example, the conductive features 220B and 220C may be electrically floating. In some embodiments, the source/drain contacts 220A can be referred to as active/operative conductive features, the conductive features 220B and 220C can be referred to as inactive/non-operative conductive features. The conductive features 220B may be located between the active gate lines 190A and the inactive gate lines 190B. Each of the conductive features 220C may be between two adjacent gate lines 190B and between two adjacent bridge portions 190C.
Based on the above discussions, it can be seen that the present disclosure offers advantages. It is understood, however, that other embodiments may offer additional advantages, and not all advantages are necessarily disclosed herein, and that no particular advantage is required for all embodiments. One advantage is that horizontal poly lines are inserted between vertical poly lines, thereby provide horizontal structural support to the vertical poly lines, and preventing poly lines from collapse. Another advantage is that defects due to poly line collapse is reduced. Still another advance is that while some wet chemicals may consume the oxide and provide strong surface tension on the poly lines, the insertion of the horizontal poly lines can relax the the process window.
According to some embodiments of the present disclosure, a semiconductor device includes a semiconductor substrate, an isolation feature, gate lines, and a first gate structure. The isolation feature is over the semiconductor substrate and surrounding an active region of the semiconductor substrate. The gate lines extend across the active region of the semiconductor substrate. The first gate structure is over the isolation feature from a cross-sectional view. From a top view, the first gate structure comprises a first gate line, a second gate line, and a first bridge portion. From a top view the first and second gate lines are substantially parallel with the gate lines, and the first bridge portion connects the first gate line to the second gate line.
According to some embodiments of the present disclosure, the semiconductor device includes a semiconductor substrate; and a first gate structure over the semiconductor substrate. The first gate structure comprises at least one gate line and at least one bridge portion, the at least one gate line extends along a gate direction, and the at least one bridge portion extends from a sidewall of the at least one gate line along a direction perpendicular to the gate direction from a top view.
According to some embodiments of the present disclosure, a method for fabricating a semiconductor device is provided. The method includes forming an isolation structure over a semiconductor substrate, wherein the isolation structure surrounds an active region of the semiconductor substrate; and forming a gate line across the active region of the semiconductor substrate and a gate structure over the isolation structure, wherein the gate structure comprises a first gate line, a second gate line, and a bridge portion connecting the first gate line to the second gate line. 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.