Patent Publication Number: US-2023154798-A1

Title: Multi-vt nanosheet devices

Description:
BACKGROUND 
     The present invention relates generally to semiconductor devices, and more specifically, to constructing nanosheet stacks with different threshold voltages without degrading logic device performance. 
     In nanometer scale devices, gate structures are often disposed between fin structures or other conducting structures, such as nanosheets. In many instances, the conducting or semiconducting structures are formed closer together due to scaling to smaller node technology sizes. This can be a limiting factor in the reduction of device size scaling. While fin field effect transistors (finFETs) and/or nanosheets can benefit from tight device-device spacing, these dimensions can limit device scaling. Further, devices needing a thicker dielectric for higher voltage operation are even more limited in the allowable dimensions. Higher voltage devices for input and/or output circuits need thicker gate dielectrics as compared to standard gate devices, which have a lower voltage and can be employed, e.g., in logic devices. 
     SUMMARY 
     In accordance with an embodiment, a method is provided for attaining different gate threshold voltages across a plurality of field effect transistor (FET) devices without patterning between nanosheet channels. The method includes forming a first set of nanosheet stacks having a first intersheet spacing, forming a second set of nanosheet stacks having a second intersheet spacing, where the first intersheet spacing is greater than the second intersheet spacing, depositing a high-k (HK) layer within the first and second nanosheet stacks, depositing a material stack that, when annealed, creates a crystallized HK layer in the first set of nanosheet stacks and an amorphous HK layer in the second nanosheet stacks, depositing a dipole material, and selectively diffusing the dipole material into the amorphous HK layer of the second set of nanosheet stacks to provide the different gate threshold voltages for the plurality of FET devices. 
     In accordance with another embodiment, a method is provided for modulating threshold voltages for nanosheet stacks without patterning between nanosheet channels. The method includes forming first nanosheet stacks having a first intersheet spacing, forming second nanosheet stacks having a second intersheet spacing, where the first intersheet spacing is greater than the second intersheet spacing, constructing a crystallized high-k (HK) layer within the first nanosheet stacks, constructing an amorphous high-k (HK) layer within the second nanosheet stacks, depositing a dipole material, and selectively diffusing the dipole material into the amorphous HK layer of the second nanosheet stacks to modulate the threshold voltages for the nanosheet stacks. 
     In accordance with yet another embodiment, a semiconductor structure is provided. The semiconductor structure includes first nanosheet stacks having a first intersheet spacing, second nanosheet stacks having a second intersheet spacing, where the first intersheet spacing is greater than the second intersheet spacing, a crystallized high-k (HK) layer disposed within the first nanosheet stacks, an amorphous high-k (HK) layer disposed within the second nanosheet stacks, and a dipole material disposed within the first and second nanosheet stacks, wherein the dipole material is selectively diffused into the amorphous HK layer of the second nanosheet stacks to modulate the threshold voltages for the nanosheet stacks. 
     It should be noted that the exemplary embodiments are described with reference to different subject-matters. In particular, some embodiments are described with reference to method type claims whereas other embodiments have been described with reference to apparatus type claims. However, a person skilled in the art will gather from the above and the following description that, unless otherwise notified, in addition to any combination of features belonging to one type of subject-matter, also any combination between features relating to different subject-matters, in particular, between features of the method type claims, and features of the apparatus type claims, is considered as to be described within this document. 
     These and other features and advantages will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will provide details in the following description of preferred embodiments with reference to the following figures wherein: 
         FIG.  1    is a cross-sectional view of a semiconductor structure including nanosheet stacks formed over a substrate, where sacrificial layers of a first region of the semiconductor structure have a first thickness and sacrificial layers of a second region of the semiconductor structure have a second thickness, in accordance with an embodiment of the present invention; 
         FIG.  2    is a cross-sectional view of the semiconductor structure of  FIG.  1    where sacrificial layers of the multiple nanosheet stacks are removed, in accordance with an embodiment of the present invention; 
         FIG.  3    is a cross-sectional view of the semiconductor structure of  FIG.  2    where an interfacial layer/high-k dielectric (IL/HK) is formed adjacent remaining layers of the multiple nanosheet stacks, in accordance with an embodiment of the present invention; 
         FIG.  4    is a cross-sectional view of the semiconductor structure of  FIG.  3    where a material stack is deposited, in accordance with an embodiment of the present invention; 
         FIG.  5    is a cross-sectional view of the semiconductor structure of  FIG.  4    where a portion of the material stack is selectively removed and an anneal takes place, in accordance with an embodiment of the present invention; 
         FIG.  6    is a cross-sectional view of the semiconductor structure of  FIG.  5    where a dipole material is deposited, in accordance with an embodiment of the present invention; 
         FIG.  7    is a cross-sectional view of the semiconductor structure of  FIG.  6    where a sacrificial layer is deposited, a capping layer is deposited, and an anneal takes place to affect diffusion or no diffusion of the dipole material, in accordance with an embodiment of the present invention; 
         FIG.  8    is a cross-sectional view of the semiconductor structure of  FIG.  7    where the sacrificial layer and the capping layer are removed, and the un-diffused dipole material is also removed, in accordance with an embodiment of the present invention; and 
         FIG.  9    is a cross-sectional view of the semiconductor structure of  FIG.  8    where a gate material is deposited, in accordance with an embodiment of the present invention. 
     
    
    
     Throughout the drawings, same or similar reference numerals represent the same or similar elements. 
     DETAILED DESCRIPTION 
     Embodiments in accordance with the present invention provide methods and devices for achieving different threshold voltages for field effect transistor (FET) devices without degrading logic device performance. The methods and structures achieve multi-Vt with selective dipole diffusion on selected nanosheet regions. Nanosheets provide for viable device architectures for scaling complementary metal oxide semiconductors (CMOS) beyond the 7 nm node. Thin gate dielectric nanosheet transistors can be used, e.g., for logic and static random access memory (SRAM) applications, whereas thick gate dielectric nanosheet transistors can be used, e.g., for high voltage and analog applications. 
     Embodiments in accordance with the present invention provide methods and devices for achieving different threshold voltages for FET devices by introducing a dopant into the gate dielectric layer, which decreases the crystalline temperature of the gate dielectric layer. Further, by selectively crystallizing the gate dielectric in a designed device region, the dipole material can selectively diffuse through the amorphous dielectric layer, but no diffusion occurs in the crystalline dielectric layer. This enables multi-Vt without patterning between nanosheet channels. The dipole forming element is present at the interfacial layer of the high Vt nFET and the low Vt pFET. Thus, a high Vt nFET and a low Vt pFET can include a crystallized HK layer with larger intersheet spacing (T sus ), whereas a low Vt nFET and a high Vt pFET can include an amorphous HK layer, with no dopant in the HK layer, and with smaller intersheet spacing (T sus ). The crystallized HK layer has a dopant, such as ZrO, due to its lower crystallization temperature than a pure HK material. 
     Examples of semiconductor materials that can be used in forming such nanosheet structures include silicon (Si), germanium (Ge), silicon germanium alloys (SiGe), silicon carbide (SiC), silicon germanium carbide (SiGeC), III-V compound semiconductors and/or II-VI compound semiconductors. III-V compound semiconductors are materials that include at least one element from Group III of the Periodic Table of Elements and at least one element from Group V of the Periodic Table of Elements. II-VI compound semiconductors are materials that include at least one element from Group II of the Periodic Table of Elements and at least one element from Group VI of the Periodic Table of Elements. 
     It is to be understood that the present invention will be described in terms of a given illustrative architecture; however, other architectures, structures, substrate materials and process features and steps/blocks can be varied within the scope of the present invention. It should be noted that certain features cannot be shown in all figures for the sake of clarity. This is not intended to be interpreted as a limitation of any particular embodiment, or illustration, or scope of the claims. 
       FIG.  1    is a cross-sectional view of a semiconductor structure including nanosheet stacks formed over a substrate, where sacrificial layers of a first region of the semiconductor structure have a first thickness and sacrificial layers of a second region of the semiconductor structure have a second thickness, in accordance with an embodiment of the present invention. 
     In various example embodiments, a semiconductor structure  5  includes shallow trench isolation (STI) regions  12  formed within a substrate  10 . Multiple field effect transistor (FET) devices can be formed over the substrate  10 . In one example, two FET devices can be formed over the substrate  10 . The FET devices can be formed by constructing nanosheet stacks. In one example, first and second nanosheet stacks  20  can be constructed over the substrate  10 . 
     Similarly, in various example embodiments, a semiconductor structure  5 ′ includes shallow trench isolation (STI) regions  12  formed within a substrate  10 . Multiple field effect transistor (FET) devices can be formed over the substrate  10 . In one example, two FET devices can be formed over the substrate  10 . The FET devices can be formed by constructing nanosheet stacks. In one example, first and second nanosheet stacks  20 ′ can be constructed over the substrate  10 . 
     An isolation layer  14  can be formed between the substrate  10  and the nanosheet stacks  20 ,  20 ′ of structures  5 ,  5 ′. Additionally, a dummy capping layer  26  can be formed over the nanosheets stacks  20 ,  20 ′ of structures  5 ,  5 ′. 
     The nanosheet stacks  20  of structure  5  can include alternating layers of a first semiconductor layer  22  and a second semiconductor layer  24 . The first semiconductor layer  22  can be, e.g., silicon germanium (SiGe) and the second semiconductor layer  24  can be, e.g., silicon (Si). 
     The nanosheet stacks  20 ′ of structure  5 ′ can include alternating layers of a first semiconductor layer  22 ′ and a second semiconductor layer  24 ′. The first semiconductor layer  22 ′ can be, e.g., silicon germanium (SiGe) and the second semiconductor layer  24 ′ can be, e.g., silicon (Si). 
     The difference between the structure  5  (left-hand side) and the structure  5 ′ (right-hand side) is the thickness of the sacrificial layers  22 ,  22 ′. The thickness of first semiconductor layer  22  can be Tsus 1  and the thickness of second semiconductor layer  22 ′ can be Tsus 2 , where Tsus 1  &gt; Tsus 2 . It is noted that the nanosheet stacks  20 ,  20 ′ can be formed on a common substrate  10 . Thus, the dipole devices can be formed with no dipole devices on a common substrate  10 . The left-hand side are the nanosheet stacks with no dipole devices and the right-hand side are the nanosheet stacks with dipole devices. 
     In one or more embodiments, the substrate  10  can be a semiconductor or an insulator with an active surface semiconductor layer. The substrate  10  can be crystalline, semicrystalline, microcrystalline, or amorphous. The substrate  10  can be essentially (e.g., except for contaminants) a single element (e.g., silicon), primarily (e.g., with doping) of a single element, for example, silicon (Si) or germanium (Ge), or the substrate  10  can include a compound, for example, Al 2 O 3 , SiO 2 , GaAs, SiC, or SiGe. The substrate  10  can also have multiple material layers, for example, a semiconductor-on-insulator substrate (SeOI), a silicon-on-insulator substrate (SOI), germanium-on-insulator substrate (GeOI), or silicon-germanium-on-insulator substrate (SGOI). The substrate  10  can also have other layers forming the substrate  10 , including high-k oxides and/or nitrides. In one or more embodiments, the substrate  10  can be a silicon wafer. In an embodiment, the substrate  10  is a single crystal silicon wafer. 
     The shallow trench isolation (STI) regions  12  can be formed by etching a trench in doped bottom source/drain (S/D) regions (not shown) utilizing a conventional dry etching process such as reactive ion etching (RIE) or plasma etching. The trenches can optionally be lined with a conventional liner material, e.g., silicon nitride or silicon oxynitride, and then chemical vapor deposition (CVD) or another like deposition process is used to fill the trench with silicon oxide or another like STI dielectric material. The STI dielectric can optionally be densified after deposition. A conventional planarization process such as chemical-mechanical polishing (CMP) can optionally be used to provide a planar structure. 
     Referring to, e.g., the first nanosheet stacks  20 , the first semiconductor layer  22  can be the first layer in a stack of sheets of alternating materials. The first nanosheet stacks  20  include first semiconductor layers  22  and second semiconductor layers  24 . Although it is specifically contemplated that the first semiconductor layers  22  can be formed from silicon germanium and that the second semiconductor layers  24  can be formed from silicon, it should be understood that any appropriate materials can be used instead, as long as the two semiconductor materials have etch selectivity with respect to one another. As used herein, the term “selective” in reference to a material removal process denotes that the rate of material removal for a first material is greater than the rate of removal for at least another material of the structure to which the material removal process is being applied. The alternating semiconductor layers  22 / 24  can be deposited by any appropriate mechanism. It is specifically contemplated that the semiconductor layers  22 / 24  can be epitaxially grown from one another, but alternate deposition processes, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), or gas cluster ion beam (GCIB) deposition, are also contemplated. A similar process can be applied to the semiconductor layers  22 ′/ 24 ′ of the nanosheet stacks  20 ′ in structure  5 ′. 
       FIG.  2    is a cross-sectional view of the semiconductor structure of  FIG.  1    where sacrificial layers of the multiple nanosheet stacks are removed, in accordance with an embodiment of the present invention. 
     In various example embodiments, the nanosheet stacks  20 ,  20 ′ are etched. The etching can include a dry etching process such as, for example, reactive ion etching, plasma etching, ion etching or laser ablation. The etching can further include a wet chemical etching process in which one or more chemical etchants are used to remove portions of the blanket layers that are not protected by the patterned photoresist. 
     In some examples, the selective wet etch or the selective dry etch can selectively remove the entire first semiconductor layers  22 ,  22 ′ and leave the entirety or portions of the second semiconductor layers  24 ,  24 ′. The removal creates gaps or openings  30  between the second semiconductor layers  24  of the FET devices in structure  5  (left-hand side) and gaps or openings  30 ′ between the second semiconductor layers  24 ′ of the FET devices in structure  5 ′ (right-hand side). 
     The dry and wet etching processes can have etching parameters that can be tuned, such as etchants used, etching temperature, etching solution concentration, etching pressure, source power, RF bias voltage, RF bias power, etchant flow rate, and other suitable parameters. Dry etching processes can include a biased plasma etching process that uses a chlorine-based chemistry. Other dry etchant gasses can include Tetrafluoromethane (CF 4 ), nitrogen trifluoride (NF 3 ), sulfur hexafluoride (SF 6 ), and helium (He), and Chlorine trifluoride (ClF 3 ). Dry etching can also be performed anisotropically using such mechanisms as DRIE (deep reactive-ion etching). Chemical vapor etching can be used as a selective etching method, and the etching gas can include hydrogen chloride (HCl), Tetrafluoromethane (CF 4 ), and gas mixture with hydrogen (H 2 ). Chemical vapor etching can be performed by CVD with suitable pressure and temperature. 
     The etching also exposes a top surface of the STI regions  12 . 
       FIG.  3    is a cross-sectional view of the semiconductor structure of  FIG.  2    where an interfacial layer/high-k dielectric (IL/HK) is formed adjacent remaining layers of the multiple nanosheet stacks, in accordance with an embodiment of the present invention. 
     In various example embodiments, interfacial layer/high-k dielectric (IL/HK)  32 / 34  is formed around each of the semiconductor layers  24 ,  24 ′ of FET devices in structures  5 ,  5 ′, respectively. The HK  34  can also be formed over the STI regions  12  and over the isolation layers  14 . 
     In some embodiments, the interfacial layer (IL)  32  can be formed to wrap around second semiconductor layers  24 ,  24 ′. IL  32  can be deposited by any appropriate method, such as ALD, CVD, and ozone oxidation. IL  32  can include, e.g., oxide, HfSiO and oxynitride. 
     HK dielectric layer  34  can be deposited over and wrapped around the IL  32  by any suitable techniques, such as ALD, CVD, metal-organic CVD (MOCVD), physical vapor deposition (PVD), thermal oxidation, combinations thereof, or other suitable techniques. HK dielectric layer  34  can include, e.g., LaO, AlO, ZrO, TiO, Ta 2 O 5 , Y 2 O 3 , SrTiO 3 (STO), BaTiO 3  (BTO), BaZrO, HfZrO, HfLaO, HfSiO, LaSiO, AlSiO, HfTaO, HfTiO, (Ba,Sr)TiO 3  (BST), Al 2 O 3 , Si 3 N 4 , oxynitrides (SiON), or other suitable materials. 
     HK dielectric layer  34  can include a single layer or multiple layers, such as metal layer, liner layer, wetting layer, and adhesion layer. HK dielectric layer  34  can include, e.g., Ti, Ag, Al, TiAlN, TaC, TaCN, TaSiN, Mn, Zr, TiN, TaN, Ru, Mo, Al, WN, Cu, W, or any suitable materials. HK dielectric layer  34  can be formed by ALD, PVD, CVD, or other suitable process. A CMP process can be performed to remove excessive HK dielectric layer  34 . 
       FIG.  4    is a cross-sectional view of the semiconductor structure of  FIG.  3    where a material stack is deposited, in accordance with an embodiment of the present invention. 
     In various example embodiments, a material stack can be formed to wrap around IL/HK 32/34. The material stack can include three layers. The first layer can be, e.g., a titanium nitride (TiN) layer  43 , the second layer can be, e.g., a zirconium oxide (ZrO) layer  42 , and the third layer can be, e.g., a TiN layer  40 . 
     In structure  7 , the ZrO layer  42  wraps around each Si layer  24 , individually, such that a TiN region  43  remains between the ZrO layer  42 . In other words, the ZrO layer  42  is selectively driven into the middle regions including the HK dielectric layer  34 . With a rapid thermal anneal (RTA) of about 950° C. and with a thickness of about 2 nm for the TiN region  43 , the ZrO layer  42  can diffuse through the 2 nm TiN region  43  into the HK dielectric layer  34 . Thus, the ZrO layer  42  is shown encompassing or enclosing each of the Si layers  24 . 
     In contrast, in structure  7 ′, the ZrO layer  42 ′ wraps around all Si layer  24 , collectively, such that a TiN region  44  remains between the HK dielectric layer  34 . In other words, the TiN region  44  is pinched off such that the ZrO layer  42 ′ does not diffuse into the HK dielectric layer  34 . 
       FIG.  5    is a cross-sectional view of the semiconductor structure of  FIG.  4    where a portion of the material stack is selectively removed and an anneal takes place, in accordance with an embodiment of the present invention. 
     In various example embodiments, the material stack is selectively removed from the nanosheet stack  20  in structure  7  and from the nanosheet stack  20 ′ in structure  7 ′. Selective removal of the material stack can be achieved by etching, such as an RIE etch. 
     The removal of the material stack results in the formation of a crystallized HK layer  50  with blanket PDA in structure  7  (left-hand side). The PDA can be applied at a temperature of about 500-700° C. without covering, which crystallizes the HK layer in structure  7  only (because Zr doped HK has a lower crystallization temperature than pure HK). In contrast, in structure  7 ′ (right-hand side), the Si doped HK layer  34  has a higher crystallization temperature than pure HK. Thus, in structure  7 ′, the HK layer  34  remains in an amorphous state, whereas in structure  7  the HK layer  34  is converted into a crystalline state designated as  50 . 
     It is noted that the IL  32  remains intact in both structures  7  and  7 ′. 
     Therefore, the exemplary embodiments of the present invention employ different intersheet spacing (T sus ) to selectively dope HK in a large T sus  region (structure  7 ) with a dopant, e.g., Zr, which decreases crystallization temperature. In other words, the intentional doping of HK is employed to selectively decrease crystallization temperature for certain regions only. Thus, the HK in structure  7 ′ remains in an amorphous state. 
       FIG.  6    is a cross-sectional view of the semiconductor structure of  FIG.  5    where a dipole material is deposited, in accordance with an embodiment of the present invention. 
     In various example embodiments, a dipole material  55  is deposited. 
     The dipole material  55  wraps around the amorphous HK layer  34  in structure  7 ′ and wraps around the crystallized HK layer  50  in structure  7 . In one example, the dipole material  55  can be, e.g., lanthanum oxide (LaO). One skilled in the art can contemplate other earth elements employed to be diffused into HK layers, such, but not limited to, as dysprosium (Dy). 
     Therefore, the exemplary embodiments of the present invention employ dipole deposition and anneal such that the dipole only diffuses through the no dipole device. Thus, different threshold voltages (Vt) can be provided. In other words, a dipole material and crystallization are employed to modulate Vt by constructing a crystallized HK on a large T sus  region and an amorphous HK on a small T sus  region. This results in a gate-all-around device that can be constructed with different intersheet spacings and selective dipole diffusion to modulate Vt. 
       FIG.  7    is a cross-sectional view of the semiconductor structure of  FIG.  6    where a sacrificial layer is deposited, a capping layer is deposited, and an anneal takes place to affect diffusion or no diffusion of the dipole material, in accordance with an embodiment of the present invention. 
     In various example embodiments, a sacrificial layer  57  is deposited, a capping layer  59  is deposited, and an anneal takes place to affect diffusion or no diffusion of the dipole material  55 . The sacrificial layer  57  can be, e.g., TiN, whereas the capping layer  59  can be, e.g., amorphous silicon (a-Si). The anneal will cause the dipole material  55  to not diffuse in the crystallized HK layer  50  (left-hand side), whereas the anneal will cause the dipole material  55  to diffuse in the amorphous HK layer  34  (right-hand side). This results in effective modulation of the threshold voltage without patterning between nanosheet channels. 
       FIG.  8    is a cross-sectional view of the semiconductor structure of  FIG.  7    where the sacrificial layer and the capping layer are removed, and the un-diffused dipole material is also removed, in accordance with an embodiment of the present invention. 
     In various example embodiments, the sacrificial layer  57  and the capping layer  59  are removed. The dipole material  55  is not diffused in the crystallized HK layer  50 . Instead, the dipole material  55  is diffused only into the amorphous HK  34  (right-hand side) to form diffused dipole material  60 . The diffused dipole material  60  is illustrated within the amorphous HK layer  34 . In contrast, the dipole material  60  is completely removed from the crystallized HK layer  50  and the isolation layer  14 . The diffused dipole material  60  is only shown adjacent one surface of the dummy capping layer  26  in right-hand side structure. 
     As a result, the non-dipole device includes a crystalline HK material  50 , where the HK layer is doped with Zr, and no dipole material  55  is found in the crystalline HK material  50 . The dipole material  55  cannot diffuse into the crystalline HK material  50 . In contrast, in the dipole device, there is an amorphous HK material  34 , where the dipole material  55  can diffuse into the amorphous HK material  34 . 
       FIG.  9    is a cross-sectional view of the semiconductor structure of  FIG.  8    where a gate material is deposited, in accordance with an embodiment of the present invention. 
     In various example embodiments, a work function metal (WFM)  65  can be deposited. The WFM  65  encompasses the non-dipole device  70  and the dipole device  70 ′. 
     The WFM  65  can be a metal, such as, e.g., copper (Cu), cobalt (Co), aluminum (Al), platinum (Pt), gold (Au), tungsten (W), titanium (Ti), nitride (N) or any combination thereof. The metal can be deposited by a suitable deposition process, for example, chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD), plating, thermal or e-beam evaporation, or sputtering. In various exemplary embodiments, the height of the WFM  65  can be reduced by chemical-mechanical polishing (CMP) and/or etching. Therefore, the planarization process can be provided by CMP. Other planarization process can include grinding and polishing. 
     In some embodiments, the nanosheet stacks can include a thin layer of conducting channel material. For example, in some embodiments, one or more of the nanosheet stacks can include Si, SiGe, Ge, and/or a Group III-V semiconductor material, for example InGaAs, but the inventive concept is not limited thereto. The term “Si nanosheet FET” refers to nanosheet FETs with nanosheets including Si or including a large percentage of Si, for example Si x Ge 1-x , where x is greater than about 0.3. The term “non- Si nanosheet FET” refers to nanosheet FETs with nanosheets not including Si, for example indium gallium arsenide (InGaAs), or including a small percentage of Si, for example Si y Ge 1-y , where y is less than about 0.3. 
     A non-Si nanosheet FET can have a higher channel carrier mobility than an equivalent Si nanosheet FET. The higher channel carrier mobility can result in higher performance. However, the non-Si nanosheet FET can also have higher band-to-band tunneling (BTBT) leakage current than the equivalent Si nanosheet FET. In general, high BTBT leakage current can occur in the same device design range as high channel carrier mobility. Several factors can induce higher BTBT leakage current in a non-Si nanosheet FET. For example, a parasitic-bipolar-effect (PBE) can effectively multiply a BTBT leakage current by a large value for non-Si nanosheet FETs with nanosheets including Si y Ge 1-y , where y is less than about 0.3, to result in a net BTBT-induced leakage current that is significantly high. 
     In conclusion, the exemplary embodiments of the present invention introduce a dopant (e.g., ZrO) into the gate dielectric layer, which decreases its crystalline temperature. Furthermore, by selectively crystallizing the gate dielectric in a designed device region, the dipole material can selectively diffuse through the amorphous dielectric layer, but no diffusion occurs in the crystalline dielectric layer. This enables multi-Vt without patterning between nanosheet channels. The dipole forming element is present at the interfacial layer of the high Vt nFET and the low Vt pFET. Thus, a high Vt nFET and a low Vt pFET can include a crystallized HK layer with larger intersheet spacing (T sus ), whereas a low Vt nFET and a high Vt pFET can include an amorphous HK layer, with no dopant in the HK layer, and with smaller intersheet spacing (T sus ). The crystallized HK layer has a dopant, such as ZrO, due to its lower crystallization temperature than a pure HK material. 
     In conclusion, a method and/or structure is presented to achieve multi-Vt for nanosheet stacks in selected regions without patterning by introducing a dopant into amorphous gate dielectric layers on two types of nanosheet FET gate-all-around stacks, each type formed using a different sacrificial SiGe thickness between the silicon channels, such that the dopant diffuses into the gate dielectric layer of the stack formed using the larger SiGe thickness, but not into the gate dielectric of the stack formed with the smaller SiGe thickness and, thus, decreasing the crystalline temperature of the gate dielectric layer of the stack formed using the larger SiGe thickness, by using a blanket anneal to selectively crystallize gate dielectric in the doped gate dielectric layers in the stack formed using the greater sacrificial thickness between the silicon channels, and by introducing a dipole material, then using a spike anneal which causes the dipole material to selectively diffuse through the amorphous dielectric layer but not through the crystalline dielectric layer, thus creating a different threshold voltage (Vt) in each of the two nanosheet FET stacks. 
     Regarding  FIGS.  1 - 9   , deposition is any process that grows, coats, or otherwise transfers a material onto the wafer. Available technologies include, but are not limited to, thermal oxidation, physical vapor deposition (PVD), chemical vapor deposition (CVD), electrochemical deposition (ECD), molecular beam epitaxy (MBE) and more recently, atomic layer deposition (ALD) among others. As used herein, “depositing” can include any now known or later developed techniques appropriate for the material to be deposited including but not limited to, for example: chemical vapor deposition (CVD), low-pressure CVD (LPCVD), plasma-enhanced CVD (PECVD), semi-atmosphere CVD (SACVD) and high density plasma CVD (HDPCVD), rapid thermal CVD (RTCVD), ultra-high vacuum CVD (UHVCVD), limited reaction processing CVD (LRPCVD), metal-organic CVD (MOCVD), sputtering deposition, ion beam deposition, electron beam deposition, laser assisted deposition, thermal oxidation, thermal nitridation, spin-on methods, physical vapor deposition (PVD), atomic layer deposition (ALD), chemical oxidation, molecular beam epitaxy (MBE), plating, evaporation. 
     The term “processing” as used herein includes deposition of material or photoresist, patterning, exposure, development, etching, cleaning, stripping, implanting, doping, stressing, layering, and/or removal of the material or photoresist as needed in forming a described structure. 
     It is to be understood that the present invention will be described in terms of a given illustrative architecture; however, other architectures, structures, substrate materials and process features and steps/blocks can be varied within the scope of the present invention. 
     It will also be understood that when an element such as a layer, region or substrate is referred to as being “on” or “over” another element, it can be directly on the other element or intervening elements can also be present. In contrast, when an element is referred to as being “directly on” or “directly over” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements can be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. 
     The present embodiments can include a design for an integrated circuit chip, which can be created in a graphical computer programming language, and stored in a computer storage medium (such as a disk, tape, physical hard drive, or virtual hard drive such as in a storage access network). If the designer does not fabricate chips or the photolithographic masks used to fabricate chips, the designer can transmit the resulting design by physical mechanisms (e.g., by providing a copy of the storage medium storing the design) or electronically (e.g., through the Internet) to such entities, directly or indirectly. The stored design is then converted into the appropriate format (e.g., GDSII) for the fabrication of photolithographic masks, which usually include multiple copies of the chip design in question that are to be formed on a wafer. The photolithographic masks are utilized to define areas of the wafer (and/or the layers thereon) to be etched or otherwise processed. 
     Methods as described herein can be used in the fabrication of integrated circuit chips. The resulting integrated circuit chips can be distributed by the fabricator in raw wafer form (that is, as a single wafer that has multiple unpackaged chips), as a bare die, or in a packaged form. In the latter case, the chip is mounted in a single chip package (such as a plastic carrier, with leads that are affixed to a motherboard or other higher level carrier) or in a multichip package (such as a ceramic carrier that has either or both surface interconnections or buried interconnections). In any case, the chip is then integrated with other chips, discrete circuit elements, and/or other signal processing devices as part of either (a) an intermediate product, such as a motherboard, or (b) an end product. The end product can be any product that includes integrated circuit chips, ranging from toys and other low-end applications to advanced computer products having a display, a keyboard or other input device, and a central processor. 
     It should also be understood that material compounds will be described in terms of listed elements, e.g., SiGe. These compounds include different proportions of the elements within the compound, e.g., SiGe includes Si x Ge 1-x  where x is less than or equal to 1, etc. In addition, other elements can be included in the compound and still function in accordance with the present embodiments. The compounds with additional elements will be referred to herein as alloys. 
     Reference in the specification to “one embodiment” or “an embodiment” of the present invention, as well as other variations thereof, means that a particular feature, structure, characteristic, and so forth described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrase “in one embodiment” or “in an embodiment”, as well any other variations, appearing in various places throughout the specification are not necessarily all referring to the same embodiment. 
     It is to be appreciated that the use of any of the following “/”, “and/or”, and “at least one of′, for example, in the cases of “A/B”, “A and/or B” and “at least one of A and B”, is intended to encompass the selection of the first listed option (A) only, or the selection of the second listed option (B) only, or the selection of both options (A and B). As a further example, in the cases of “A, B, and/or C” and “at least one of A, B, and C”, such phrasing is intended to encompass the selection of the first listed option (A) only, or the selection of the second listed option (B) only, or the selection of the third listed option (C) only, or the selection of the first and the second listed options (A and B) only, or the selection of the first and third listed options (A and C) only, or the selection of the second and third listed options (B and C) only, or the selection of all three options (A and B and C). This can be extended, as readily apparent by one of ordinary skill in this and related arts, for as many items listed. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof. 
     Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” and the like, can be used herein for ease of description to describe one element’s or feature’s relationship to another element(s) or feature(s) as illustrated in the FIGS. It will be understood that 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 FIGS. For example, if the device in the FIGS. is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein can be interpreted accordingly. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers can also be present. 
     It will be understood that, although the terms first, second, etc. can be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Thus, a first element discussed below could be termed a second element without departing from the scope of the present concept. 
     Having described preferred embodiments of a method for attaining different gate threshold voltages across a plurality of field effect transistor (FET) devices without patterning between nanosheet channels (which are intended to be illustrative and not limiting), it is noted that modifications and variations can be made by persons skilled in the art in light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments described which are within the scope of the invention as outlined by the appended claims. Having thus described aspects of the invention, with the details and particularity required by the patent laws, what is claimed and desired protected by Letters Patent is set forth in the appended claims.