Fin-shaped field effect transistor device
阅读说明:本技术 鳍状场效晶体管装置 (Fin-shaped field effect transistor device ) 是由 黄如立 江欣哲 潘育麒 杨峻铭 梁春升 庄英良 叶明熙 于 2019-05-07 设计创作,主要内容包括:本发明实施例说明鳍状场效晶体管装置的结构与形成方法。鳍状场效晶体管装置包括:基板;鳍状物,位于基板上;以及栅极结构,位于鳍状物上。栅极结构包括功函数金属层,位于栅极结构的内侧侧壁上。功函数金属层的最顶侧表面低于栅极结构的上表面。栅极结构亦包括充填栅极金属层,位于功函数金属层的最顶侧表面上。充填栅极金属层的上表面与栅极结构的上表面实质上共平面。栅极结构亦包括自组装单层,位于充填栅极金属层与功函数金属层之间。(Embodiments of the present invention illustrate structures and methods of forming finfet devices. The fin field effect transistor device includes: a substrate; a fin on the substrate; and a gate structure on the fin. The gate structure includes a work function metal layer on an inside sidewall of the gate structure. The topmost surface of the work function metal layer is lower than the upper surface of the gate structure. The gate structure also includes a filled gate metal layer on a topmost surface of the work function metal layer. The upper surface of the gate-filled metal layer is substantially coplanar with the upper surface of the gate structure. The gate structure also includes a self-assembled monolayer between the filled gate metal layer and the work function metal layer.)
1. A finfet device, comprising:
a substrate;
a fin on the substrate;
a gate structure on the fin, the gate structure comprising:
a work function metal layer on the inner sidewall of the gate structure, and the topmost surface of the work function metal layer is lower than the upper surface of the gate structure;
a gate-filled metal layer on a topmost surface of the work function metal layer, an upper surface of the gate-filled metal layer being substantially coplanar with an upper surface of the gate structure; and
a self-assembled monolayer between the filled gate metal layer and the work function metal layer.
Technical Field
Embodiments of the present invention relate to semiconductor structures, and more particularly, to structures and methods for improving gate resistance.
Background
Cmos fets are key components in the semiconductor industry and play a significant role in a variety of electronic devices. In semiconductor processing, metals and high-k dielectric materials are used in place of polysilicon and silicon oxide to form gate structures in transistors that meet performance requirements (e.g., carrier mobility and device speed) as transistor dimensions shrink. To form the metal gate, the dummy gate may be formed first and then removed to form a space (e.g., a trench or a reserved space) for the metal gate. Then, a dielectric material with a high dielectric constant and a metal are deposited in the trench to fill the trench and form a metal gate.
Disclosure of Invention
An embodiment of the present invention provides a finfet device, including: a substrate; a fin on the substrate; and a gate structure on the fin. The grid structure comprises a work function metal layer which is positioned on the inner side wall of the grid structure, and the topmost surface of the work function metal layer is lower than the upper surface of the grid structure; a gate-filled metal layer on a topmost surface of the work function metal layer, an upper surface of the gate-filled metal layer being substantially coplanar with an upper surface of the gate structure; and a self-assembled monolayer between the gate-filled metal layer and the work function metal layer.
An embodiment of the present invention provides a method for forming a semiconductor device, including: providing a substrate, wherein the substrate comprises a grid structure with a work function metal layer; removing the top of the work function metal layer; forming a self-assembled monolayer on a topmost surface of the work function metal layer exposed by removing a top of the work function metal layer; and depositing a fill gate metal layer into the removed top portion of the work function metal layer with the self-assembled monolayer between the fill gate metal layer and the work function metal layer.
An embodiment of the present invention provides a method for forming a semiconductor device, including: providing a substrate, wherein the substrate comprises a grid structure; selectively removing the top of the gate structure; forming an adhesive layer on the upper surface of the gate structure exposed by removing the top of the gate structure; and selectively depositing a conductive layer on the adhesive layer on the removed top of the gate structure, wherein the adhesive layer adheres the upper surface of the gate structure exposed by the removed top of the gate structure and the conductive layer.
Drawings
FIG. 1A is a diagram of a MOSFET device in some embodiments.
Fig. 1B is a top view of the nmos device of fig. 1A, in some embodiments.
Fig. 2 is a cross-sectional view of a gate in some embodiments.
Fig. 3A-3C, 4A-4C, and 5A-5C are cross-sectional views of gates in some embodiments.
Figure 6 is a drawing of a fabrication process for forming a gate metal in an etched-back gate in some embodiments.
Description of reference numerals:
h1, h2, h3 vertical depth
H FFin height
H GHeight of grid
Lg gate length
L SLength of
W fin width
100 semiconductor structure
102 substrate
104 fin
106 isolation structure
108 grid structure
108 ', 108' -1, 108 '-2, 108' -3 intermediate gate structure
110 DDrain region
110 SSource region
111 spacer layer
112 channel region
113 lightly doped drain region
114. 128 upper surface
115. 115 ', 115' high dielectric constant dielectric layer
116. 116 ', 116' cap layer
117 sacrificial gate structure
117' gate forming trench
117A, 117B1, 117B2, 117C1, 117C2 etch back trenches
118. 118 ', 118' barrier metal layer
119. 119 ', 119' work function metal layer
120. 120 ', 120' self-assembled monolayers
121. 121' filled gate metal layer
125 gate dielectric layer
128 dotted line
131 cross section
150 region of transistor
200. 300, 400, 500 structure
600 method
601. 602, 603, 604
Detailed Description
The different embodiments or examples provided below may implement different configurations of the present disclosure. The particular components and arrangements are provided to simplify the present disclosure and not to limit the same.
Also, spatially relative terms such as "below," "lower," "underside," "above," "upper" and the like may be used for ease of description to describe one element's relative relationship to another element in the figures. Spatially relative terms may be extended to elements used in other orientations than the orientation illustrated. The elements may also be rotated 90 or other angles, and thus directional terms are used only to describe directions in the drawings.
An example of the field effect transistor described herein is a metal oxide semiconductor field effect transistor. For example, a mosfet may be (i) a planar structure built in or on a planar surface of a substrate, such as a semiconductor wafer, or (ii) a vertical structure.
The term "fin field effect transistor" refers to a field effect transistor formed on a fin that is oriented vertically with respect to a planar surface of a wafer.
"source/drain" refers to the source/drain junctions that form the two ends of a field effect transistor.
The term "perpendicular" as used herein refers to being approximately perpendicular to the substrate surface.
The term "epitaxial layer" refers to a layer or structure of single crystal material. Likewise, the term "epitaxial growth" refers to a layer or structure of single crystal material. The epitaxially grown material may be doped or undoped.
The term "approximate" as used herein refers to a desired objective, characteristic value or parameter for a component or process step, which has been set at the design stage of a product, along with upper and lower limits for the desired value. The range of values typically comes from slight variations or tolerances in the process (tolerances).
One of the problems in forming metal gates of small gate length is how to deposit a sufficient amount of metal into the gate formation trenches. For example, a metal gate with a gate length of 7nm has a higher gate resistance than a metal gate with a gate length of 20nm because the amount of metal deposited in the metal gate with a length of 7nm is less. Similarly, the gate resistance of the 7nm metal gate and the 20nm metal gate is higher than that of the 240nm metal gate.
To reduce the gate resistance, a dry etch back and a wet etch back may be used to remove portions of the workfunction metal in the metal gate and fill in more metal in the metal gate. However, the etch-back process has a low etch selectivity, which may result in metal loss in the etched metal gate. For example, in addition to the workfunction metal, it is also possible to etch back the gate metal (e.g., tungsten) and the barrier layer (e.g., titanium nitride), resulting in a recess depth in the etched back profile. The above steps also reduce the gate height. In addition, the by-products formed during these etch-back processes may be difficult to remove. These etchback methods do not provide the desired etch selectivity between the workfunction metal and the gate metal. For example, the gate metal may be etched back using a wet etch process. As semiconductor devices continue to shrink, it becomes increasingly difficult to fabricate metal gates with the desired low gate resistance.
Embodiments of the present invention illustrate a selective etch back to remove a portion of the workfunction metal surrounding the metal in the metal gate. A relatively low or lower resistance conductive material is then filled into the space formed by the removal of the workfunction metal to increase the metal volume in the metal gate. The selective etch-back process may form one or more self-assembled monolayers on the etched portions. The self-assembled monolayer may improve adhesion between the etched portion and the newly deposited fill gate metal. A selective deposition process may be employed to deposit a newly deposited filler gate metal (e.g., a conductive material) that may include a desired and/or different dopant concentration and/or species to further improve (e.g., reduce) gate resistance. The selective etch back and selective deposition do not require additional masks or additional fabrication processes. Thus, the gate height is substantially unaffected (e.g., reduced), and more metal may be deposited into the metal gate. By using the method disclosed by the embodiment of the invention, the metal grid can have more metal than the metal grid manufactured at the beginning, the resistance of the grid can be reduced, and the electrical property of the semiconductor device can be improved. In addition, the newly deposited filler gate metal may adhere to the etched portions of the metal gate that have no voids or have few voids formed therein. The gate metal formed may be more uniform, thus reducing gate resistance. The method and structure of the embodiments of the invention can improve the device performance.
Fig. 1A, fig. 1B, fig. 2, fig. 3A to fig. 3C, fig. 4A to fig. 4C, and fig. 5A to fig. 5C are metal gates in various semiconductor devices fabricated by a gate resistance improvement method according to an embodiment of the present invention. The fabrication process can form a metal gate with an increased amount of gate metal, which can have a lower gate resistance than other gate metal structures. The additional gate metal according to embodiments disclosed herein may be bonded to the portion of the contact fill gate metal that has no voids or has a small amount of voids therein. The term "fill gate metal" refers to a conductive material subsequently deposited into the removed portion of the workfunction metal layer and may serve as the gate metal for the metal gate structure. Embodiments of the present invention may be used to form metal gates of various metals, such as tungsten, copper, aluminum, any other suitable metal, or combinations thereof. Metal gates may be formed in a variety of semiconductor devices and structures. For example, embodiments of the present invention may be used to form metal gates in planar devices and finfet transistors. The fabrication processes provided herein are merely exemplary, and other processes performed by embodiments of the present invention are not illustrated in subsequent figures.
Figure 1A is an isometric view of a
Each
The
The
The
Figure 1B is a top view of a
Fig. 1B shows the
Lightly doped
Furthermore, any suitable process may be employed to form the source region 110
SA/drain region 110
DLightly doped
Fig. 2-5C are various cross-sectional views of various stages in the fabrication of a finfet in accordance with various embodiments of the present invention. The method provided by the embodiment of the invention can be part of the gate replacement process or after the gate replacement process. In the embodiment of the present invention, the metal gate structure formed by the method disclosed in the embodiment of the present invention may be referred to as the middle gate structure 108'. The
Fig. 2-5C illustrate an exemplary fabrication process for forming the metal gate structure. In some embodiments, the
Figure 2 is a drawing of a structure 200 including an exemplary intermediate gate structure 108' along the
The method of removing the
Fig. 3A-3C are
In some embodiments, the intermediate gate structures 108 '-1, 108' -2, and 108 '-3 of fig. 3A-3C may each be formed from intermediate gate structures (e.g., the intermediate gate structure 108' of fig. 2) having similar structures (e.g., different dimensions and/or different gate lengths). A plurality of layers may be sequentially deposited into the gate formation trench 117 ' to form the intermediate gate structures 108 ' -1, 108 ' -2, and 108 ' -3 of fig. 3A-3C from the intermediate gate structure 108 ' of fig. 2. The subsequently formed metal gate structure may include a barrier layer, a gate dielectric layer, a work function layer, a metal layer, and/or other suitable materials filled in the gate formation trench. In other embodiments, the metal gate structure may further include a cap layer, an etch stop layer, and/or other suitable materials. The
A high-k dielectric layer may be formed on the sidewalls of the
A capping layer may be formed on the high-k dielectric layer in the gate-forming trench 117'. In one example, the capping layer may comprise a high dielectric constant barrier material, such as titanium nitride and/or TSN. In another example, the capping layer can protect the high-k dielectric layer from a subsequently formed barrier metal layer and reduce interface traps between the
A barrier metal layer may be further formed on the cap layer in the gate forming trench 117'. The barrier layer may comprise a metal and/or compound such as tantalum nitride and/or niobium nitride. The barrier metal layer can improve the adhesion between the cap layer and the subsequently formed work function metal layer. The barrier metal layer may also prevent carrier and/or ion diffusion between the cap layer and the work function metal layer. The barrier metal layer may be formed by chemical vapor deposition, physical vapor deposition, atomic layer deposition, plasma enhanced chemical vapor deposition, metal organic chemical vapor deposition, sputtering, other suitable deposition methods, or any combination thereof. The thickness of the barrier metal layer may be between about 1nm and about 3 nm. In some embodiments, the thickness of the barrier metal layer is about 1.5 nm. In the embodiment of the present invention, the intermediate gate structures 108 '-1, 108' -2, and 108 '-3 have
A workfunction metal layer may also be formed on the barrier gold layer in the gate formation trench 117'. Exemplary p-type work function metals that may be included in the metal gate structure include titanium nitride, tantalum nitride, ruthenium, molybdenum, aluminum, tungsten nitride, zirconium silicide, molybdenum silicide, tantalum silicide, nickel silicide, other suitable p-type work function materials, or combinations thereof. Exemplary n-type workfunction metals that may be included in the metal gate structure include titanium, silver, tantalum aluminum carbide, titanium aluminum nitride, tantalum carbide, tantalum carbonitride, tantalum silicon nitride, manganese, zirconium, other suitable n-type workfunction materials, or combinations thereof. The work function is related to the material composition of the work function layer, and thus the material of the first work function layer may be selected to adjust its work function to achieve a desired threshold voltage for the devices to be formed in the respective regions. In some embodiments, the work function metal layer may comprise a work function metal such as titanium nitride, titanium aluminum carbide, other suitable work function metals, or any combination thereof. The work function metal layer may change the threshold voltage of the intermediate gate structure 108' to a desired value. The work function metal layer may be formed by chemical vapor deposition, physical vapor deposition, atomic layer deposition, plasma enhanced chemical vapor deposition, organometallic chemical vapor deposition, sputtering, other suitable deposition methods, or any combination thereof. In some embodiments, the work function metal layer has a thickness between about 1nm and about 3 nm. In an embodiment of the present invention, the intermediate gate structures 108 '-1, 108' -2, and 108 '-3 have work
A fill gate metal (e.g., a gate metal layer) may be further formed on the workfunction metal layer in the gate formation trench 117'. The gate-filling metal layer may fill the remaining space in the gate-forming trench 117'. The filler gate metal layer may comprise a suitable conductive material such as copper, aluminum, and/or tungsten. In some embodiments, the filled gate metal layer comprises tungsten. The gate metal layer may be formed by chemical vapor deposition, physical vapor deposition, plasma enhanced chemical vapor deposition, metal organic chemical vapor deposition, sputtering, other suitable deposition methods, or any combination thereof. In some embodiments, the thickness of the gate metal layer is between about 1nm and 3 nm. In the present embodiment, the intermediate gate structures 108 ' -2 and 108 ' -3 have gate-filled
In some embodiments, a planarization process such as chemical mechanical polishing may be used after the formation of the above-mentioned layers to remove the excess thickness of the layers on the
As shown in fig. 3A-3C, the high-k dielectric layers 115, 115 ', and 115 ", the capping layers 116, 116 ', and 116", and the
As shown in fig. 3A-3C, the gate-filling
Fig. 4A-4C illustrate
In some embodiments, the top of the workfunction metal layer in the intermediate gate structure 108' is removed and an etch back trench is formed. The above steps may expose the inner surface of the etched portion. For example, for the etch back
In some embodiments, the etch-back process may be performed using a suitable etch process. In some embodiments, a wet etch is performed to selectively etch the top of the respective workfunction metal layer. In some embodiments, an etchant (e.g., an etching solution) may selectively etch the workfunction metal layer on other layers and/or materials in the gate formation trench 117'. For example, the etch selectivity (e.g., the ratio of etch rates) of the etchant on the gate metal may be at least about 2, and/or the etch selectivity on the high-k dielectric material may be at least about 2. In some embodiments, the etch selectivity over the gate metal is at least about 3. The etch selectivity over other layers and/or materials may be as high as desired so that the selective etch may remove the top of the workfunction metal layer while the other layers in the gate formation trench 117' may remain substantially the same in thickness, height, and/or shape.
The etchant may be dispensed on a wafer or
In some embodiments, the
The etchant may be used to form a self-assembled monolayer when reacting with the work function metal layer and/or other layers of the intermediate gate structure 108', such as the fill gate metal layer and/or the barrier metal layer. In some embodiments, the etchant facilitates the formation of a self-assembled monolayer when reacting with the fill gate metal, the work function metal layer, and the barrier metal layer, and the self-assembled monolayer after the etching process may cover the exposed surfaces of these layers. As shown in fig. 4A-4C, the self-assembled
Specifically, the self-assembled monolayer may be formed between the phosphate and the material of the intermediate gate structures 108 ' -1, 108 ' -2, and 108 ' -3 (e.g., the work function metal layer, the material filling the gate metal layer, and/or the barrier metal layer). For example, the phosphate may form a self-assembled monolayer with the metal oxide in these layers. In some embodiments, the metal layer comprises tungsten, the work function metal layer comprises titanium nitride, and the barrier metal layer comprises tantalum nitride. The phosphate may then react with the titanium oxide in the work function metal layer to form a self-assembled monolayer of titanium phosphate on the exposed surface of the work function metal layer, with the tantalum oxide in the barrier metal layer to form a self-assembled monolayer of tantalum phosphate on the exposed surface of the barrier metal layer, and with the tungsten oxide in the gate-filled metal layer to form a self-assembled monolayer of tungsten phosphate on the exposed surface of the gate-filled metal layer. In the present embodiments, the term "self-assembled monolayer of phosphate of a metal" is merely for convenience of description to distinguish between different chemical compounds, and does not denote the chemical composition or formula of the compound.
The self-assembled monolayer may cover the material that reacts with the phosphate. In some embodiments, the etchant composition may be selected to match the material being etched and/or the material being exposed, so that the self-assembled monolayer may completely cover the inner surface of the etched-back trench. The self-assembled monolayer may improve adhesion between subsequently deposited gate-filled metal and the etched-back trench, so that the gate-filled metal may fill the etched-back trench with little or no voids. In summary, the amount of gate metal in the subsequently formed metal gate structure may be increased, and the gate resistance may be reduced. In some embodiments, a self-assembled monolayer is formed on the work function metal layer to improve adhesion between the fill gate metal and the work function metal layer. In some embodiments, the self-assembled monolayer is formed on the gate metal filling layer to improve adhesion between the gate metal and the metal filling layer, so that no voids are formed between the gate metal and the metal filling layer. In some embodiments, the resistance of the self-assembled monolayer is sufficiently low or negligible so that the presence of the self-assembled monolayer has little or no effect on the conductivity of the filled gate metal layer and the filled gate metal. In various embodiments, other suitable materials may be used to form the work function metal layer, the fill gate metal layer, and/or the metal barrier layer. The etchant composition may be varied to ensure that a self-assembled monolayer (having an adhesion function to bond the fill gate metal to the work function metal layer) is formed at least on the work function metal layer. The particular choice of etchant composition may not be limiting to the embodiments of the invention.
In some embodiments, the workfunction metal layer may be etched back by other methods. For example, a planarization process may be used to expose and etch the topmost surface of the work function metal layer in the intermediate gate structure 108' and a mask may be used to cover the topmost surface of the other layers. As noted above, the top of the workfunction metal layer may be removed by a suitable etch, such as a time controlled wet and/or dry etch process. The mask may be removed after the etch back. An adhesion layer (e.g., a liner layer or a self-assembled monolayer) may optionally be formed on the inner surfaces of the etched-
Fig. 5A-5C illustrate
In some embodiments, the fill gate metal is deposited via a selective deposition process and is in-situ doped during the selective deposition. In some embodiments, the gate-filled metal layer comprises tungsten and the gate-filled metal comprises tungsten. A selective deposition method for forming tungsten may include atomic layer deposition. In some embodiments, an atomic layer deposition process may be performed using precursor gases of tungsten pentachloride gas and hydrogen gas. Solid tungsten may be selectively formed in the etch-back trench. In some embodiments, the flow rate of tungsten pentachloride is between about 50sccm to about 100sccm and the flow rate of hydrogen is between about 1000sccm to about 2000 sccm. Tungsten pentachloride may be carried by argon to pump into a reaction chamber at a temperature between about 450 ℃ and 550 ℃ to a chamber pressure of about 40 Torr. Hydrogen gas may be pumped into the reaction chamber to a pressure of about 60 Torr. As described above, tungsten may be deposited to fill the etch-back trench. In some embodiments, a selective deposition process is used to form tungsten without an additional mask to ensure that tungsten is formed in the etch-back trench. In some embodiments, after forming the tungsten, a chemical mechanical polish may be performed to planarize the upper surface of the intermediate gate structures 108 ' -1, 108 ' -2, and 108 ' -3.
In some embodiments, other deposition methods (e.g., selective or non-selective) may be used to fill the filled gate metal into the etched-back trench. If a non-selective deposition method is used, an etch back process may be performed to remove excess gate metal outside the etch back trench. For example, a patterning process may be performed to expose and remove excess gate metal outside the etched-back trench. A chemical mechanical polishing process may then be performed to planarize the upper surface of the intermediate gate structures 108 ' -1, 108 ' -2, and 108 ' -3.
In some embodiments, a filler gate metal having a different gate metal (e.g., a different native gate metal material than the filler gate metal layer) may also be deposited. The filled gate metal may have a relatively low resistance or lower resistance than the filled gate metal layer. In some embodiments, the self-assembled monolayer covering the etch-back trench may improve adhesion between the filled gate metal (such as comprising a metal and/or conductive material different from the original gate metal material filled with the gate metal layer) and the work-function metal layer.
In some embodiments, appropriate dopants may be formed into the filled gate metal to further reduce gate resistance. For example, boron may be doped into the fill gate metal to increase the doping level and thus reduce the gate resistance. Boron may be deposited on the filled gate metal (which may comprise the same or different material than the original gate metal material of the filled gate metal layer). In some embodiments, the self-assembled monolayer covers the etch-back trench, improving adhesion between the doped filled gate metal and at least the workfunction metal layer. In some embodiments, the self-assembled monolayer adheres the doped filled gate metal to the filled gate metal layer with little or no voids therein.
After depositing the gate metal into the etch-
In some embodiments, after forming the metal gate structures, the metal gate structures may be separated, and/or segmented along the x-axis or direction in which the metal gate structures extend to form short channel metal gate structures. For example, a metal gate structure may be located on a
In the embodiment of the invention, the method for replacing part of the work function metal layer with the conductive material can reduce the gate resistance of the metal gate structure. In some embodiments, other portions and/or layers of the metal gate structure may also be replaced with a conductive material (e.g., a conductive material having a desired resistance and/or doping level) to further reduce the gate resistance. For example, the top of the barrier metal layer and the top of the workfunction metal layer may be removed (or selectively removed) together to further increase the amount of gate metal in the metal gate structure. One or more etch back processes may be performed. In summary, the etchant used to remove these portions can be adjusted to form a self-assembled monolayer on the etched surface and improve adhesion between other layers exposed on the etched surface and the subsequently deposited conductive material. In addition, a suitable conductive material may be formed (or selectively formed) in the etch-back trench to fill the metal gate structure. Specific methods and structures may be had by reference to the embodiments of the invention and are not described in detail herein.
Compared with other schemes, the metal gate structure formed by the method and the structure disclosed by the embodiment of the invention has lower gate resistance. A selective etch may be performed to remove the top of the workfunction metal layer and form a self-assembled monolayer on the inside surface of the etched portion to improve adhesion between the subsequently deposited filler gate metal and the workfunction metal layer. A selective deposition may be performed to fill the etched portions with a fill gate metal. The filled gate metal has a relatively low or low gate resistance compared to the original gate metal material. For metal gate structures with little or no gate metal layer on the work function metal layer prior to the gate metal filling process, the gate metal may be deposited into the gate metal structure after the filling process and the gate resistance may be reduced. For metal gate structures that have sufficient gate metal in the gate metal layer filled prior to the gate metal filling process, more gate metal (or conductive material having a relatively low or lower resistance) may be included in the metal gate structure to further reduce the gate resistance. In some embodiments, the selective etching and selective deposition do not require an additional mask for the process, and thus no additional fabrication processes are required in forming the
Fig. 6 is a flow diagram of an
In
In
In
The
Embodiments of the present invention illustrate a selective etch-back process for a method of removing a work function metal surrounding a gate metal in a metal gate. A relatively low resistance or less resistive conductive material is then filled into the space created by the removal of the workfunction metal to increase the gate metal volume in the metal gate. A selective etch-back process forms a self-assembled monolayer over the etched portions. The self-assembled monolayer may improve adhesion between the etched portion and the newly deposited filled gate metal. The newly deposited fill gate metal (e.g., conductive material) may be deposited by selective deposition and may include desired and/or different dopant concentrations and/or species to further improve (e.g., reduce) gate resistance. The selective etch back and selective deposition do not require additional masks or additional fabrication processes. Thus, the gate height is not substantially affected (e.g., reduced) and more gate metal may be deposited into the metal gate. By adopting the method disclosed by the embodiment of the invention, the grid metal amount of the metal grid can be higher than that of the metal grid manufactured at the beginning, the grid resistance can be reduced, and the electrical property of the semiconductor device can be improved. In addition, the newly deposited filled gate metal may adhere to the etched portions of the metal gate with little (or no) voids formed therein. The gate metal formed may be more uniform. The gate resistance can be further reduced. Thus, the method and structure disclosed in the embodiments of the present invention can improve device performance.
In some embodiments, a finfet device, comprising: a substrate; a fin on the substrate; and a gate structure on the fin. The grid structure comprises a work function metal layer which is positioned on the inner side wall of the grid structure, and the topmost surface of the work function metal layer is lower than the upper surface of the grid structure; a gate-filled metal layer on a topmost surface of the work function metal layer, an upper surface of the gate-filled metal layer being substantially coplanar with an upper surface of the gate structure; and a self-assembled monolayer between the gate-filled metal layer and the work function metal layer.
In some embodiments, the self-assembled monolayer includes an adhesion layer between the work function metal layer and the filled gate metal layer.
In some embodiments, the finfet device further comprises an additional gate-filled metal layer surrounding the work function metal layer, and an upper surface of the additional gate-filled metal layer is substantially coplanar with an upper surface of the gate structure, wherein the self-assembled monolayer is between the additional gate-filled metal layer and the gate-filled metal layer.
In some embodiments, the self-assembled monolayer comprises: a first portion formed of a phosphate and a work function metal layer located between the work function metal layer and the filled gate metal layer; and a second portion formed by the phosphate and the other gate-filled metal layer, between the gate-filled metal layer and the other gate-filled metal layer.
In some embodiments, the finfet device further comprises a barrier metal layer surrounding the work-function metal layer, wherein a top surface of the barrier metal layer is substantially coplanar with a top surface of the gate structure, wherein the self-assembled monolayer further comprises a third portion formed by a phosphate and the barrier metal layer, the third portion being located between the barrier metal layer and the gate-filled metal layer.
In some embodiments, the filled gate metal layer and the other filled gate metal layer each comprise a common conductive material.
In some embodiments, the gate-filled metal layers have a first doping level, the other gate-filled metal layers have a second doping level, and the first doping level is higher than the second doping level.
In some embodiments, the work function metal layer comprises titanium nitride, titanium aluminum nitride, or titanium aluminum carbide; the barrier metal layer comprises tantalum nitride or niobium nitride; each of the filled gate metal layer and the other filled gate metal layers comprises one or more of tungsten and aluminum; and the fill gate metal layer comprises boron.
In some embodiments, a first portion of the self-assembled monolayer comprises titanium oxide and phosphate, a second portion of the self-assembled monolayer comprises tungsten oxide and phosphate, and a third portion of the self-assembled monolayer comprises tantalum oxide and phosphate.
In some embodiments, a method of forming a semiconductor device includes: providing a substrate, wherein the substrate comprises a grid structure with a work function metal layer; removing the top of the work function metal layer; forming a self-assembled monolayer on a topmost surface of the work function metal layer exposed by removing a top of the work function metal layer; and depositing a fill gate metal layer into the removed top portion of the work function metal layer with the self-assembled monolayer between the fill gate metal layer and the work function metal layer.
In some embodiments, the step of removing the top portion of the work-function metal layer comprises performing a selective etch-back that etches the work-function metal layer at a higher rate than other materials of the substrate.
In some embodiments, the work function metal layer comprises titanium nitride, titanium aluminum nitride, or titanium aluminum carbide; and the step of performing the selective etch back includes using a mixture of hydrogen peroxide, phosphoric acid, and hot deionized water to remove the top of the work function metal layer at room temperature to 80 ℃.
In some embodiments, the step of selectively etching back further comprises forming a self-assembled monolayer on the work-function metal layer, and wherein the self-assembled monolayer comprises a portion formed by the mixture and the work-function metal layer.
In some embodiments, the step of depositing a gate fill metal layer into the top portion of the removed work function metal layer comprises selectively depositing a gate metal into the top portion of the removed work function metal layer, and the self-assembled monolayer is an adhesion layer between the gate fill metal layer and the work function metal layer.
In some embodiments, the substrate further comprises an additional filled gate metal layer surrounded by the work function metal layer, wherein the selectively etching back further comprises forming another portion of the self-assembled monolayer on the additional filled gate metal layer, the other portion of the self-assembled monolayer being formed from the mixture with the additional filled gate metal layer, and the additional filled gate metal layer being bonded to the filled gate metal layer via the other portion of the self-assembled monolayer.
In some embodiments, the step of depositing the gate-fill metal layer includes performing atomic layer deposition and in-situ doping processes, and wherein the gate-fill metal layer and the other gate-fill metal layer include a common conductive material.
In some embodiments, the common conductive material comprises tungsten; and the doping level of the gate-filled metal layer is higher than the doping levels of the other gate-filled metal layers, and the gate-filled metal layer comprises boron.
In some embodiments, a method of forming a semiconductor device includes: providing a substrate, wherein the substrate comprises a grid structure; selectively removing the top of the gate structure; forming an adhesive layer on the upper surface of the gate structure exposed by removing the top of the gate structure; and selectively depositing a conductive layer on the adhesive layer on the removed top of the gate structure, wherein the adhesive layer adheres the upper surface of the gate structure exposed by the removed top of the gate structure and the conductive layer.
In some embodiments, the doping level of the conductive layer is higher than the doping level of the top of the removed gate structure.
In some embodiments, the step of selectively removing the top portion of the gate structure comprises a selective etching process, and the step of depositing the conductive layer comprises a selective deposition process and an in-situ doping process.
It is to be understood that paragraphs (not abstract) of the embodiments may be used to interpret the claims. The abstract may describe one or more but not all exemplary embodiments, and thus the appended claims are not to be limited.
Features of the above-described embodiments or examples may be helpful to one skilled in the art in understanding embodiments of the present invention. Those skilled in the art should appreciate that they may readily use the present embodiments 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 above. It should also be understood by those skilled in the art that such equivalent substitutions 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.
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