Metal gate device structure manufacturing method and metal gate device structure

Abstract

The invention discloses a metal gate device structure manufacturing method and a metal gate device structure, and the method comprises the steps: selectively removing second work function layers on first to fourth fin parts and third work function layers on first to third fin parts when first to fifth work function layers are formed on first to sixth fin parts, and a fourth work function layer on the first fin portion to the second fin portion, and oxygen free radicals are used for forming the first work function layer on each fin portion before the second work function layer is formed, the exposed first work function layer before the third work function layer is formed, and the reserved second work function layer. The exposed first work function layer and the reserved third work function layer before the formation of the fourth work function layer and the exposed first work function layer and the reserved fourth work function layer before the formation of the fifth work function layer are respectively subjected to first processing, so that the roughness of the processed surface is reduced, the fluctuation of threshold voltage can be reduced, and the processing efficiency is improved. And the stability of turn-on voltage regulation and control is improved.

Description

Fabrication method and structure of metal gate device Technical Field

[0001] This application relates to the field of semiconductor processing technology, and in particular to a method for fabricating a metal gate device structure and a metal gate device structure fabricated using this method. Background Technology

[0002] In the gate-on voltage regulation steps of different device regions using high-k dielectric metal gate (HKMG) technology, different voltage controls (customized threshold voltages) are achieved by depositing metal work function materials of varying thicknesses (such as TaN, TiN, TiAl, etc.). Therefore, work function layers of different thicknesses exist in different device regions, requiring multiple thin-film depositions to form these layers. At advanced nodes, due to the extremely thin thickness of each work function layer (approximately 0.5 nm to 2 nm), poor surface roughness is often a problem after deposition. Furthermore, the poor surface roughness of the preceding work function layer not only directly affects the growth quality of the subsequent work function layer, but the superposition of multiple work function materials with certain roughness also affects the final threshold voltage value of the metal gate device, leading to uncontrollable threshold voltage fluctuations and insufficient gate-on voltage stability in different device regions. Therefore, it is necessary to investigate a process method that can significantly improve these problems. Summary of the Invention

[0003] The purpose of this application is to overcome the above-mentioned problems existing in the prior art and to provide a method for fabricating a metal gate device structure and a metal gate device structure.

[0004] To achieve the above objectives, the technical solution of this application is as follows: According to a first aspect of this application, an embodiment of this application provides a method for fabricating a metal gate device structure, comprising: forming a plurality of fins including a first fin, a second fin, a third fin, a fourth fin, a fifth fin, and a sixth fin on a substrate; sequentially forming a first work function layer and a second work function layer on the surface of each of the fins; selectively removing the second work function layer on the first to fourth fins, and forming a third work function layer on the exposed surface of the first work function layer and on the surface of the second work function layer retained on the fifth to sixth fins; selectively removing the third work function layer on the first to third fins, and forming a third work function layer on the exposed surface of the first work function layer and on the surface of the third work function layer retained on the fourth to sixth fins. A fourth work function layer; selectively removing the fourth work function layer on the first fin to the second fin, and forming a fifth work function layer on the surface of the exposed first work function layer and the surface of the retained fourth work function layer on the third fin to the sixth fin; wherein, using oxygen free radicals excited by metastable particles, a first treatment is performed on the surface of the first work function layer on each of the fins before the formation of the second work function layer, the surface of the exposed first work function layer and the surface of the retained second work function layer before the formation of the third work function layer, the surface of the exposed first work function layer and the surface of the retained third work function layer before the formation of the fourth work function layer, and the surface of the exposed first work function layer and the surface of the retained fourth work function layer before the formation of the fifth work function layer, respectively, to reduce the roughness of the treated surfaces.

[0005] In some embodiments, the first treatment is performed using the oxygen free radicals to oxidize the surface to be treated, thereby generating an oxide layer on the surface to be treated. The oxide layer fills and smooths the microscopic undulations on the surface to be treated, thereby achieving atomic-level chemical mechanical smoothing of the surface to be treated.

[0006] In some embodiments, the oxide layer also serves as a diffusion barrier layer to suppress element diffusion in order to stabilize the interfacial stoichiometry.

[0007] In some embodiments, the first work function layer includes a TaN layer, the second work function layer, the third work function layer and the fourth work function layer include a TiN layer, the fifth work function layer includes a TiAl layer, and the oxide layer includes a TaON layer formed on the surface of the TaN layer and a TiON layer formed on the surface of the TiN layer.

[0008] In some embodiments, the oxygen free radicals are obtained by exciting oxygen with helium metastable particles and filtering out charged particles therein. The helium metastable particles are obtained by exciting helium gas and filtering out charged particles therein. During the first treatment, the helium flow rate is 1000 sccm to 9000 sccm, the oxygen flow rate: helium flow rate = 1:1 to 10:1, the temperature is 50℃ to 180℃, the source power is 100W to 1000W, the pressure is 100mTorr to 1000mTorr, the time is 30s to 300s, and the ion filter is turned on while the bias power is turned off.

[0009] In some embodiments, the thickness of the first work function layer is 8 Å to 15 Å.

[0010] In some embodiments, the thickness of the second work function layer is 5 Å to 10 Å.

[0011] In some embodiments, the thickness of the third work function layer is 5 Å to 10 Å.

[0012] In some embodiments, the thickness of the fourth work function layer is 5 Å to 15 Å.

[0013] In some embodiments, the thickness of the fifth work function layer is 20 Å to 60 Å.

[0014] In some embodiments, the method further includes performing a second process on the surfaces of the first work function layer on each of the fins before the formation of the second work function layer, the exposed surface of the first work function layer and the retained surface of the second work function layer before the formation of the third work function layer, the exposed surface of the first work function layer and the retained surface of the third work function layer before the formation of the fourth work function layer, and the exposed surface of the first work function layer and the retained surface of the fourth work function layer before the formation of the fifth work function layer, respectively, to clean and activate the surfaces to be processed.

[0015] In some embodiments, the second treatment is performed using NH4OH and isopropanol in sequence.

[0016] In some embodiments, the isopropanol is used at a temperature of 50°C to 80°C.

[0017] According to a second aspect of this application, embodiments of this application also provide a metal gate device structure, which is obtained using the metal gate device structure fabrication method provided in any of the embodiments of the first aspect above.

[0018] The embodiments of this application may / at least have the following advantages: (1) By using oxygen free radicals excited by metastable particles, the surfaces of the first to fourth work function layers, which are the surfaces to be treated, are respectively subjected to a first treatment. The oxidation reaction that occurs on the surface to be treated can effectively passivate the dangling bonds and active sites of the surface to be treated at the nanoscale, reducing the non-uniformity of surface energy. The protrusions on the surface to be treated are preferentially oxidized (the protrusions have higher surface energy and more dangling bonds than the depressions, and are therefore more sensitive to oxidation). The oxidation can drive the slight migration of atoms or promote the "relaxation" of unstable atoms at the grain boundary, thus playing the role of "filling" or "smoothing" the micro-undulations of the original surface. That is, by selectively oxidizing the surface to be treated, these protrusions are preferentially oxidized and consumed, making the surface smoother. Atomic-level chemical mechanical smoothing of the rough surface to be treated is achieved, reducing the micro-roughness (RMS), thereby reducing the fluctuation of the threshold voltage and improving the stability of the turn-on voltage regulation. Furthermore, at relatively low temperatures (50℃~180℃), highly chemically active oxygen free radicals can undergo controlled oxidation reactions with the treated surface, generating an extremely thin (typically a few atomic layers) and dense oxide layer. This layer suppresses the interdiffusion of oxygen and / or nitrogen elements between different work function layers during subsequent processes, stabilizing the interfacial stoichiometry and thus the metal work function. Ultimately, this improves the electrical pathway for threshold voltage stability.

[0019] (2) By using helium metastable particles to generate low-energy oxygen free radicals, a surface oxidation treatment with lower energy and almost no damage can be achieved. This effectively avoids the problem of needing to increase the initial value of the film thickness and causing a large loss of the film by using surface treatments such as acid washing with excessive intensity. It can also simplify the manufacturing process.

[0020] (3) By performing a second treatment with NH4OH and hot isopropanol in sequence before the first treatment, a clean and activated surface can be provided for the subsequent oxidation reaction, so as to give full play to the effect of atomic-level chemical mechanical smoothing on the surface.

[0021] Other advantages of this application will be described in the following detailed description. Attached Figure Description

[0022] Figure 1 is a flowchart of a method for fabricating a metal gate device structure according to a preferred embodiment of this application.

[0023] Figure 2 is a schematic diagram of a preferred embodiment of this application after a first work function layer has been formed on the surface of the first to sixth fins.

[0024] Figure 3 is a schematic diagram of a preferred embodiment of this application after a second work function layer is formed on the surface of the first work function layer of the first fin to the sixth fin.

[0025] Figure 4 is a schematic diagram of a preferred embodiment of this application, showing a dielectric layer covering the first to sixth fins formed on the surface of a substrate.

[0026] Figure 5 is a schematic diagram of a preferred embodiment of this application after removing the dielectric layer on the first fin to the fourth fin and removing the second work function layer on the first fin to the fourth fin.

[0027] Figure 6 is a schematic diagram of a preferred embodiment of this application after removing the remaining medium layer on the fifth to sixth fins.

[0028] Figure 7 is a schematic diagram of a preferred embodiment of this application after a third work function layer is formed on the fourth to sixth fins.

[0029] Figure 8 is a schematic diagram of a preferred embodiment of this application after a fourth work function layer is formed on the third to sixth fins.

[0030] Figure 9 is a schematic diagram of a preferred embodiment of this application after a fifth work function layer is formed on the first to sixth fins.

[0031] In the figure: 10. Substrate; 11. Fin; 111. First fin; 112. Second fin; 113. Third fin; 114. Fourth fin; 115. Fifth fin; 116. Sixth fin; 12. First work function layer; 13. Isolation structure; 14. Second work function layer; 15. Dielectric layer; 16. Third work function layer; 17. Fourth work function layer; 18. Fifth work function layer. Detailed Implementation

[0032] In the evolution of gate technology, as the critical linewidth size continues to shrink, a combination of high-k dielectric and metallic materials (HKMG) has been adopted to replace the traditional SiO2 / Si gate structure, thereby overcoming problems such as excessive gate leakage current and difficulty in precisely controlling the threshold voltage. HKMG technology uses high-k materials to replace traditional silicon dioxide as the gate dielectric layer and metallic materials to replace polysilicon as the gate electrode. High-k materials have a higher dielectric constant, allowing for a thicker physical thickness while maintaining the same capacitance, thus significantly reducing gate leakage current and static power consumption. Simultaneously, metallic gate materials have better work function matching, reducing carrier scattering at the interface, improving carrier mobility, increasing on-state current (Ion), and accelerating switching speed.

[0033] At more advanced nodes (7nm and below), in the turn-on voltage regulation steps in different device regions, it is necessary to form work function layers of different thicknesses through multiple thin film depositions in different device regions. Before each deposition, the surface roughness of the preceding work function material is extremely important. Poor surface roughness directly affects the fluctuation of the threshold voltage.

[0034] In view of this, embodiments of this application provide a method for fabricating a metal gate device structure, comprising: forming a plurality of fins including a first fin, a second fin, a third fin, a fourth fin, a fifth fin, and a sixth fin on a substrate; sequentially forming a first work function layer and a second work function layer on the surface of each of the fins; selectively removing the second work function layer on the first to fourth fins, and forming a third work function layer on the exposed surface of the first work function layer and on the surface of the second work function layer retained on the fifth to sixth fins; selectively removing the third work function layer on the first to third fins, and forming a fourth work function layer on the exposed surface of the first work function layer and on the surface of the third work function layer retained on the fourth to sixth fins; selectively removing the second work function layer on the first to third fins. The fourth work function layer is described on the first fin to the second fin, and a fifth work function layer is formed on the exposed surface of the first work function layer and on the surface of the retained fourth work function layer on the third fin to the sixth fin; wherein, oxygen free radicals excited by metastable particles are used to perform a first treatment on the surface of the first work function layer on each of the fins before the formation of the second work function layer, the exposed surface of the first work function layer and the surface of the retained second work function layer before the formation of the third work function layer, the exposed surface of the first work function layer and the surface of the retained third work function layer before the formation of the fourth work function layer, and the exposed surface of the first work function layer and the surface of the retained fourth work function layer before the formation of the fifth work function layer, respectively, to reduce the roughness of the treated surfaces.

[0035] This application embodiment uses oxygen free radicals excited by metastable particles to perform a first treatment on the surfaces of the first to fourth work function layers, which are the surfaces to be treated. This can achieve atomic-level chemical mechanical smoothing of the rough surfaces being treated, reduce micro-roughness (RMS), thereby reducing the fluctuation of the threshold voltage and improving the stability of the turn-on voltage regulation.

[0036] This application also provides a metal gate device structure, which is obtained using the metal gate device structure fabrication method described above.

[0037] The specific embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0038] Referring to Figure 1. According to a first aspect of this application, an embodiment of this application provides a method for fabricating a metal gate device structure, which may include the following steps in sequence: Step S11: forming a first fin, a second fin, a third fin, a fourth fin, a fifth fin and a sixth fin on a substrate.

[0039] Referring to Figure 2. In some embodiments, substrate 10 may include any suitable type of semiconductor substrate and material. For example, substrate 10 may include a silicon (Si) substrate, a germanium (Ge) substrate, or a germanium-silicon (SiGe) substrate, or a III / V compound semiconductor substrate, such as a gallium arsenide (GaAs) substrate, an indium gallium arsenide (InGaAs) substrate, or similar materials.

[0040] In some embodiments, multiple device regions may be defined on the substrate 10, including a first device region A, a second device region B, a third device region C, a fourth device region D, a fifth device region E, and a sixth device region F. The first device region A may be an N-type low threshold voltage (NLVT) region, the second device region B may be an N-type ultra-low threshold voltage (NULVT) region, the third device region C may be an N-type standard threshold voltage (NSVT) region, the fourth device region D may be a P-type standard threshold voltage (PSVT) region, the fifth device region E may be a P-type low threshold voltage (PLVT) region, and the sixth device region F may be a P-type ultra-low threshold voltage (PULVT) region.

[0041] Multiple protruding fins 11 can be formed on the surface of the substrate 10 using a patterning process. These include a first fin 111 located in a first device region A (NLVT region), a second fin 112 located in a second device region B (NULVT region), a third fin 113 located in a third device region C (NSVT region), a fourth fin 114 located in a fourth device region D (PSVT region), a fifth fin 115 located in a fifth device region E (PLVT region), and a sixth fin 116 located in a sixth device region F (PULVT region). Each fin 11 is used to further form a metal gate structure on its surface, enabling the modulation of the turn-on voltage for different device regions. An isolation structure 13 for isolating each device region is formed on the substrate 10 surrounding each fin 11.

[0042] It should be noted that, since the aforementioned device regions are not arranged sequentially adjacently on the substrate 10, they are isolated by vertical dashed lines in Figure 2 (the same below). Furthermore, for the sake of simplification, the first device region A and the second device region B are represented by the same graphic region on the left, and the first fin 111 and the second fin 112 are represented by the same fin 11 graphic (the gate stacking structures on the first fin 111 and the second fin 112 are the same), and the fifth device region E and the sixth device region F are represented by the same graphic region on the right, and the fifth fin 115 and the sixth fin 116 are represented by the same fin 11 graphic (the gate stacking structures on the fifth fin 115 and the sixth fin 116 are the same).

[0043] Step S12: Form a first work function layer on the surface of each fin, and perform a first oxidation treatment on the surface of the first work function layer.

[0044] Referring to Figure 2. In some embodiments, a first work function layer 12 is formed on the surface of the first fin 111, the second fin 112, the third fin 113, the fourth fin 114, the fifth fin 115 and the sixth fin 116 using a deposition process.

[0045] In some embodiments, the first work function layer 12 includes a TaN layer.

[0046] In some embodiments, the thickness of the first work function layer 12 (TaN layer) is 8 Å to 15 Å. For example, the thickness of the first work function layer 12 may be 8 Å, 9 Å, 10 Å, 11 Å, 12 Å, 13 Å, 14 Å or 15 Å, or any value between any two of the aforementioned thickness values.

[0047] Since the first work function layer 12 is extremely thin, it often has poor surface roughness after deposition. Therefore, the surface roughness of the first work function layer 12 (the treated surface) can be reduced by performing a first treatment on the surface of the first work function layer 12.

[0048] In some embodiments, oxygen free radicals excited by metastable particles are used to perform a first oxidation treatment (first treatment) on the surface of the first work function layer 12 on each fin 11 to reduce the surface roughness of the treated first work function layer 12.

[0049] In some embodiments, the surface to be treated is oxidized by using oxygen free radicals to generate an oxide layer (first oxide layer) on the surface. The oxide layer fills in and smooths the microscopic undulations on the surface to be treated, thereby achieving atomic-level chemical mechanical smoothing of the surface.

[0050] Furthermore, the oxide layer can also serve as an auxiliary diffusion barrier layer to suppress element diffusion and stabilize the interfacial stoichiometry.

[0051] In some embodiments, the oxide layer (first oxide layer) comprises a dense TaON layer (TaO) formed on the surface of the first work function layer 12 of the TaN material. x N y layer).

[0052] By oxidizing the surface of the first work function layer 12 using oxygen free radicals (first oxidation treatment), the extremely high chemical reactivity of oxygen free radicals allows for a controlled oxidation reaction with the surface of the first work function layer 12 at a relatively low temperature, generating a transition layer of extremely thin (typically a few atomic layers), uniform, and dense oxide layer, which serves as an interface passivation layer. The oxidation treatment effectively passivates dangling bonds and active sites on the surface of the first work function layer 12, reduces surface energy inhomogeneity, and selectively oxidizes the rough surface of the first work function layer 12. At the nanoscale, the "peaks" (protrusions) on the surface of the first work function layer 12 film have higher surface energy and more dangling bonds than the "valleys" (recesses), making them more sensitive to oxidation. Oxygen free radicals preferentially oxidize and consume these "peaks," and the oxide layer can "fill" or "smooth" the micro-undulations of the original surface. The oxidation process may drive slight migration of metal atoms (Ta atoms) or promote the "relaxation" of unstable atoms at grain boundaries, making the surface smoother, thereby achieving atomic-level chemical mechanical smoothing of the surface and reducing micro-roughness (RMS). At the same time, this dense oxide layer can also act as an auxiliary diffusion barrier layer, inhibiting the interdiffusion of elements such as oxygen and nitrogen between different work function layers in subsequent processes and stabilizing the interfacial stoichiometry. Therefore, by reducing the interface state density (the flat, passivated interface significantly reduces charge traps at the interface) and stabilizing the metal work function (the uniform interface layer stabilizes the effective work function of the first work function layer 12, preventing it from drifting under electrothermal stress due to interface reaction or impurity diffusion), the electrical path of improving threshold voltage stability is ultimately improved (the above effects also apply when subsequent oxidation treatments (second oxidation treatment, third oxidation treatment, and fourth oxidation treatment) are performed on the second, third, and fourth work function layers respectively).

[0053] In some embodiments, oxygen radicals are obtained by exciting oxygen gas with helium metastable particles and filtering out charged particles. The helium metastable particles are obtained by exciting helium gas and filtering out charged particles. By using helium metastable particles to generate low-energy oxygen radicals, a lower-energy, almost damage-free surface oxidation process can be achieved. This effectively avoids the problems of previous surface treatments such as acid pickling, which required an additional initial value for the film thickness and caused significant film loss, and also simplifies the manufacturing process.

[0054] In some embodiments, during the first oxidation treatment (first treatment), the flow rate ratio of oxygen to helium is 1 to 10 (oxygen flow rate: helium flow rate = 1:1 to 10:1). For example, the flow rate ratio of oxygen to helium can be 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, or any value between any two of the aforementioned flow rate ratios.

[0055] In some embodiments, during the first oxidation treatment, the helium flow rate is 1000 sccm to 9000 sccm. For example, the helium flow rate can be 1000 sccm, 2000 sccm, 3000 sccm, 4000 sccm, 5000 sccm, 6000 sccm, 7000 sccm, 8000 sccm, or 9000 sccm, or any value between any two of the aforementioned flow rates.

[0056] In some embodiments, the temperature during the first oxidation treatment is 50°C to 180°C. For example, the temperature may be 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, or 180°C, or any value between any two of the aforementioned temperature values.

[0057] In some embodiments, the source power is 100W to 1000W during the first oxidation treatment. For example, the source power may be 100W, 200W, 300W, 400W, 500W, 600W, 700W, 800W, 900W or 1000W, or any value between any two of the aforementioned power values.

[0058] In some embodiments, the pressure during the first oxidation treatment is 100 mTorr to 1000 mTorr. For example, the pressure may be 100 mTorr, 200 mTorr, 300 mTorr, 400 mTorr, 500 mTorr, 600 mTorr, 700 mTorr, 800 mTorr, 900 mTorr, or 1000 mTorr, or any value between any two of the aforementioned pressure values.

[0059] In some embodiments, the time for the first oxidation treatment is 30s to 300s. For example, the time can be 30s, 35s, 40s, 50s, 55s, 80s, 100s, 120s, 150s, 170s, 200s, 220s, 250s, 280s, or 300s, or any value between any two of the aforementioned time values.

[0060] In some embodiments, during the first oxidation process, ion filtering is turned on and bias power is turned off.

[0061] By synergistically controlling the flow ratio, temperature, source power, pressure, time, etc., lower energy oxygen free radicals can be obtained, achieving ultra-low damage surface oxidation treatment.

[0062] In some embodiments, before forming the first work function layer 12, a gate dielectric layer (e.g., HfO2) and a bottom diffusion barrier layer (e.g., TiN cap layer) may be formed sequentially on the surface of each fin 11, and then the first work function layer 12 may be formed on the surface of the bottom diffusion barrier layer.

[0063] In some embodiments, before performing a first oxidation treatment (first treatment) on the surface of the first work function layer 12, a first cleaning treatment (second treatment) may be performed on the surface of the first work function layer 12 to clean and activate the surface of the first work function layer 12 (the surface to be treated), and then the first oxidation treatment may be performed on the surface of the first work function layer 12.

[0064] In some embodiments, the surface of the first work function layer 12 is subjected to a first cleaning treatment using NH4OH and hot isopropanol (IPA) sequentially. When cleaning the surface of the first work function layer 12 with NH4OH, NH4OH can form soluble complexes with many metal ions, thereby removing residual metal contaminants adsorbed in the chambers on the surface of the first work function layer 12. Subsequently, the surface of the first work function layer 12 is cleaned and dried using hot isopropanol, which removes organic residues and particulate adsorption, achieving perfect dehydration and drying.

[0065] In some embodiments, isopropanol is used at a temperature of 50°C to 80°C. Heating significantly enhances the chemical activity of isopropanol, enabling more effective dissolution and stripping of trace organic matter remaining on the surface of the first work function layer 12, thus enhancing dissolution and stripping. Isopropanol has extremely low surface tension and is miscible with water. After cleaning in hot isopropanol, as the substrate 10 (wafer) is vertically lifted from the liquid surface, the isopropanol rapidly and uniformly evaporates from the surface of the substrate 10, carrying away residual moisture. This perfectly prevents the appearance of "watermarks" or "drying defects" in nanoscale patterned structures, which is crucial for high aspect ratio structures. The high fluidity of hot isopropanol also helps to wash away tiny particles.

[0066] By performing a first cleaning treatment (second treatment) with NH4OH and hot isopropanol sequentially before the first oxidation treatment (first treatment), a cleaned and activated first work function layer 12 can be provided for the subsequent oxidation reaction, so as to give full play to the effect of atomic-level chemimechanical smoothing on the treated surface.

[0067] In some embodiments, when a high-dielectric-constant gate dielectric layer (e.g., HfO2) and a TiN cap layer serving as a bottom diffusion barrier layer are sequentially formed on the surface of each fin 11, the deposition thickness of the TiN cap layer is also extremely thin (e.g., 10 Å to 20 Å), and the surface roughness may be poor after deposition. Therefore, the second and first processing techniques described above can also be used to sequentially clean and oxidize the surface of the TiN cap layer to make the surface of the treated TiN cap layer smoother. In particular, a uniform and dense TiON layer (TiO2) is formed on the surface of the TiN cap layer by oxidation. x N y The oxide layer can serve as an auxiliary diffusion barrier layer, thereby significantly improving the diffusion barrier capability of the TiN cap layer.

[0068] In some embodiments, when a high-dielectric-constant gate dielectric layer (e.g., HfO2) and a TiN cap layer serving as a bottom diffusion barrier layer are sequentially formed on the surface of each fin 11, an amorphous silicon layer can be deposited on the surface of the TiN cap layer before forming the first work function layer 12, followed by peak annealing, removal of the amorphous silicon layer, and then deposition of the first work function layer 12. The amorphous silicon layer can serve as a sacrificial layer and a morphology buffer layer. During subsequent peak annealing, the amorphous silicon layer acts as an oxygen "getter layer," preferentially reacting with diffused oxygen to generate SiO. x To prevent oxygen atoms from diffusing into the channel and thus avoid performance degradation, an amorphous silicon layer can be used to fill any microscopic irregularities on the TiN layer surface, forming a more uniform interface that facilitates a consistent interface reaction during subsequent peak annealing. Peak annealing promotes a reaction between the amorphous silicon layer and the TiN cap layer at high temperatures (around 900℃). Silicon atoms diffuse into the interstitial spaces or grain boundaries of TiN, physically blocking the rapid diffusion of impurities such as oxygen and hydrogen along the grain boundaries, significantly improving the diffusion barrier capability of the TiN cap layer. In some areas, stable silicon-rich TiSiN compounds or more stable nitride phases may also form, which themselves possess excellent barrier properties. Simultaneously, peak annealing can passivate interface traps, which is crucial for improving positive and negative bias temperature instability and stabilizing the interface stoichiometry.

[0069] Step S13: A second work function layer is formed on the surface of the first work function layer on the fifth to sixth fins, and a second oxidation treatment is performed on the surface of the second work function layer and the surface of the first work function layer exposed on the first to fourth fins.

[0070] Referring to Figure 3. In some embodiments, a deposition process is used to form a second work function layer 14 on the surface of the first work function layer 12, which has undergone a first oxidation treatment and has been smoothed.

[0071] In some embodiments, the second work function layer 14 includes a TiN layer.

[0072] In some embodiments, the thickness of the second work function layer 14 (TiN layer) is 5 Å to 10 Å. For example, the thickness of the second work function layer 14 may be 5 Å, 6 Å, 7 Å, 8 Å, 9 Å or 10 Å, or any value between any two of the aforementioned thickness values.

[0073] Since the thickness of the work function layer in the gate stack structure of the first device region A (NLVT region), the second device region B (NULVT region), the third device region C (NSVT region), and the fourth device region D (PSVT region) is generally smaller than the thickness of the work function layer in the gate stack structure of the fifth device region E (PLVT region) and the sixth device region F (PULVT region), it can be achieved by selectively removing the second work function layer 14 on the first fin 111, the second fin 112, the third fin 113, and the fourth fin 114, while retaining the second work function layer 14 on the fifth fin 115 and the sixth fin 116.

[0074] Referring to Figure 4. In some embodiments, a deposition process may be used to form a dielectric layer 15 on the surface of the substrate 10 and cover the top of each fin 11.

[0075] Then, photolithography and dry etching processes can be used to selectively remove the dielectric layer 15 located on the first fin 111 to the fourth fin 114, while retaining the dielectric layer 15 located on the fifth fin 115 to the sixth fin 116, so that the second work function layer 14 located on the first fin 111 to the fourth fin 114 is exposed.

[0076] Next, a wet etching process can be used to remove the second work function layer 14 located on the first fin 111 to the fourth fin 114, so that the first work function layer 12 located on the first fin 111 to the fourth fin 114 is exposed, as shown in Figure 5.

[0077] Subsequently, an asher process can be used to remove the remaining dielectric layer 15 on the fifth fin 115 to the sixth fin 116, exposing the second work function layer 14 on the fifth fin 115 to the sixth fin 116, as shown in Figure 6. Thus, the second work function layer 14 is selectively formed on the surface of the first work function layer 12 on the fifth fin 115 to the sixth fin 116.

[0078] In some embodiments, the dielectric layer 15 material may include a bottom anti-reflective coating (BARC).

[0079] In some embodiments, a mixture of O2, N2 and H2 and CH4 can be used as process gases for dry etching of the dielectric layer 15.

[0080] In some embodiments, the temperature during the dry etching process is 10°C to 60°C. For example, the temperature can be 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C, or any value between any two of the aforementioned temperature values.

[0081] In some embodiments, the source power is 100W to 2000W when performing a dry etching process. For example, the source power can be 100W, 200W, 500W, 800W, 1000W, 1100W, 1500W, 1800W, 1900W or 2000W, or any value between any two of the aforementioned power values.

[0082] In some embodiments, the pressure during the dry etching process is 5 mTorr to 100 mTorr. For example, the pressure can be 5 mTorr, 6 mTorr, 10 mTorr, 20 mTorr, 30 mTorr, 40 mTorr, 50 mTorr, 80 mTorr, 90 mTorr, or 100 mTorr, or any value between any two of the aforementioned pressure values.

[0083] In some embodiments, DHF (diluted hydrofluoric acid) and SC2 (an acidic cleaning solution containing hydrochloric acid, hydrogen peroxide, and deionized water) may be used sequentially as the solutions for wet etching processes.

[0084] In some embodiments, the time for performing the wet etching process is 50s to 100s. For example, the time can be 50s, 55s, 60s, 65s, 70s, 75s, 80s, 85s, 90s, 95s, or 100s, or any value between any two of the aforementioned time values.

[0085] In some embodiments, when performing a wet etching process, a hot IPA (50°C to 80°C) is used for drying after wet etching.

[0086] In some embodiments, a mixture of N2 and H2 gas can be used as the process gas for ashing the remaining dielectric layer 15.

[0087] In some embodiments, an inductively coupled plasma excitation mode is used during the ashing process.

[0088] In some embodiments, the temperature during the ashing process is 100°C to 200°C. For example, the temperature may be 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, or 200°C, or any value between any two of the aforementioned temperature values.

[0089] In some embodiments, the source power during the ashing process is 1000W to 5000W. For example, the source power can be 1000W, 1200W, 1500W, 1800W, 2000W, 2500W, 3000W, 3500W, 4000W, 4500W, or 5000W, or any value between any two of the aforementioned power values.

[0090] In some embodiments, the pressure during the ashing process is 100 mTorr to 2000 mTorr. For example, the pressure can be 100 mTorr, 200 mTorr, 500 mTorr, 800 mTorr, 1000 mTorr, 1300 mTorr, 1500 mTorr, 1800 mTorr, 1900 mTorr, or 2000 mTorr, or any value between any two of the aforementioned pressure values.

[0091] In some embodiments, a second oxidation treatment (first treatment) is performed on the surface of the second work function layer 14 and the surface of the first work function layer 12 exposed on the first fin 111 to the fourth fin 114.

[0092] In some embodiments, the surface of the second work function layer 14 and the surface of the first work function layer 12 exposed on the first fin 111 to the fourth fin 114 are subjected to a second cleaning treatment (second treatment) and a second oxidation treatment (first treatment) in sequence.

[0093] Since the second work function layer 14 deposited on the fifth fin 115 to the sixth fin 116 is also extremely thin, poor surface roughness may still exist after deposition. Simultaneously, the surface of the first work function layer 12 located on the first fin 111 to the fourth fin 114 may also be damaged during the aforementioned dry etching, wet etching, and ashing processes, affecting its roughness. Therefore, a first oxidation treatment (first treatment) can be performed on the surface of the first work function layer 12 on the first fin 111 to the sixth fin 116 (or sequentially) as described above. The second oxidation treatment (first treatment) is performed on the surface of the second work function layer 14 located on the fifth fin 115 to the sixth fin 116 and the surface of the first work function layer 12 located on the first fin 111 to the fourth fin 114 in the same manner as the first cleaning treatment (second treatment) and the second oxidation treatment (first treatment) are performed sequentially to reduce the surface roughness of the treated second work function layer 14 and the surface roughness of the re-treated first work function layer 12. Please refer to the above description of the first cleaning treatment (second treatment) and the first oxidation treatment (first treatment) for understanding, and will not be repeated hereafter (the same applies below).

[0094] It should be noted that the mechanism of action for the second oxidation treatment of the second work function layer 14 of TiN material and the first work function layer 12 of TaN material is similar to that of the first oxidation treatment of the first work function layer 12 of TaN material. The difference is that, during the second oxidation treatment, the oxide layer (second oxide layer) formed on the surface of the second work function layer 14 of the treated TiN material is a TiON layer (TiO2). x N y The oxide layer (second oxide layer) formed on the surface of the first work function layer 12 of the reprocessed TaN material is still a TaON layer (TaO). x N y layer).

[0095] Step S14: A third work function layer is formed on the surface of the second work function layer and on the surface of the first work function layer exposed on the fourth fin, and a third oxidation treatment is performed on the surface of the third work function layer and the surface of the first work function layer exposed on the first to third fins.

[0096] Referring to Figure 7. In some embodiments, a deposition process may be used to form a third work function layer 16 on the surfaces of the first work function layer 12 (which has undergone a second oxidation treatment and is now planarized) on the first fin 111 to the fourth fin 114, and on the surfaces of the second work function layer 14 (which has undergone a second oxidation treatment and is now planarized) on the fifth fin 115 to the sixth fin 116. Then, the third work function layer 16 on the first fin 111 to the third fin 113 is selectively removed, exposing the first work function layer 12 on the first fin 111 to the third fin 113, while retaining the third work function layer 16 on the fourth fin 114 to the sixth fin 116.

[0097] In some embodiments, the third work function layer 16 includes a TiN layer.

[0098] In some embodiments, the thickness of the third work function layer 16 (TiN layer) is 5 Å to 10 Å. For example, the thickness of the third work function layer 16 may be 5 Å, 6 Å, 7 Å, 8 Å, 9 Å or 10 Å, or any value between any two of the aforementioned thickness values.

[0099] Similarly, since the thickness of the work function layer in the gate stack structure of the first device region A (NLVT region), the second device region B (NULVT region), and the third device region C (NSVT region) is smaller than the thickness of the work function layer in the gate stack structure of the fourth device region D (PSVT region), the fifth device region E (PLVT region), and the sixth device region F (PULVT region), it can be achieved by selectively removing the third work function layer 16 on the first fin 111, the second fin 112, and the third fin 113, while retaining the third work function layer 16 on the fourth fin 114, the fifth fin 115, and the sixth fin 116.

[0100] In some embodiments, a similar method can be used to selectively remove the second work function layer 14 on the first fin 111, second fin 112, third fin 113, and fourth fin 114, while retaining the second work function layer 14 on the fifth fin 115 and sixth fin 116, to selectively remove the third work function layer 16 on the first fin 111, second fin 112, and third fin 113, while retaining the third work function layer 16 on the fourth fin 114, fifth fin 115, and sixth fin 116. That is, a dielectric layer is first formed again on the surface of the substrate 10, covering the top of each fin 11. Then, the dielectric layer on the first fin 111 to the third fin 113 is selectively removed, while the dielectric layer on the fourth fin 114 to the sixth fin 116 is retained, exposing the third work function layer 16 on the first fin 111 to the third fin 113. Next, the third work function layer 16 located on the first fin 111 to the third fin 113 is removed, and then the remaining dielectric layer on the fourth fin 114 to the sixth fin 116 is removed to obtain the structure shown in FIG7.

[0101] In some embodiments, a third oxidation treatment (first treatment) is performed on the surface of the third work function layer 16 located on the fourth fin 114 to the sixth fin 116 and the surface of the first work function layer 12 located on the first fin 111 to the third fin 113.

[0102] In some embodiments, the surfaces of the third work function layer 16 located on the fourth fin 114 to the sixth fin 116 and the surfaces of the first work function layer 12 located on the first fin 111 to the third fin 113 are subjected to a third cleaning treatment (second treatment) and a third oxidation treatment (first treatment) in sequence.

[0103] In some embodiments, similarly, the same method as described above for performing a second oxidation treatment (first treatment) (or sequentially performing a second cleaning treatment (second treatment) and a second oxidation treatment (first treatment)) on the surfaces of the first work function layer 12 on the first fins 111 to the fourth fins 114 and the second work function layer 14 on the fifth fins 115 to the sixth fins 116, can be used to perform a third oxidation treatment (first treatment) (or sequentially performing a third cleaning treatment (second treatment) and a third oxidation treatment (first treatment)) on the surfaces of the third work function layer 16 on the fourth fins 114 to the sixth fins 116 and the first work function layer 12 on the first fins 111 to the third fins 113, in order to reduce the surface roughness of the treated third work function layer 16 and the surface roughness of the first work function layer 12 on the first fins 111 to the third fins 113, which are then treated again. Furthermore, during the third oxidation treatment, the oxide layer (third oxide layer) formed on the surface of the treated TiN material's third work function layer 16 is a TiON layer (TiO2).x N y The oxide layer (third oxide layer) formed on the surface of the first work function layer 12 of the TaN material after it has been treated again is still a TaON layer (TaO). x N y layer).

[0104] Step S15: A fourth work function layer is formed on the surface of the third work function layer and on the surface of the first work function layer exposed on the third fin, and a fourth oxidation treatment is performed on the surface of the fourth work function layer and the surface of the first work function layer exposed on the first fin to the second fin.

[0105] Referring to Figure 8. In some embodiments, a deposition process may be used to form a fourth work function layer 17 on the surfaces of the first work function layer 12 (which has undergone a third oxidation treatment and is now smoothed) on the first fin 111 to the third fin 113, and on the surfaces of the third work function layer 16 (which has undergone a third oxidation treatment and is now smoothed). Then, the fourth work function layer 17 on the first fin 111 to the second fin 112 is selectively removed, exposing the first work function layer 12 on the first fin 111 to the second fin 112, while retaining the fourth work function layer 17 on the third fin 113 to the sixth fin 116.

[0106] In some embodiments, the fourth work function layer 17 includes a TiN layer.

[0107] In some embodiments, the thickness of the fourth work function layer 17 (TiN layer) is 5 Å to 15 Å. For example, the thickness of the fourth work function layer 17 may be 5 Å, 6 Å, 7 Å, 8 Å, 9 Å, 10 Å, 11 Å, 12 Å, 13 Å, 14 Å or 15 Å, or any value between any two of the aforementioned thickness values.

[0108] Similarly, since the thickness of the work function layer in the gate stack structure of the first device region A (NLVT region) and the second device region B (NULVT region) is smaller than the thickness of the work function layer in the gate stack structure of the third device region C (NSVT region), the fourth device region D (PSVT region), the fifth device region E (PLVT region), and the sixth device region F (PULVT region), it can be achieved by selectively removing the fourth work function layer 17 on the first fin 111 and the second fin 112, while retaining the fourth work function layer 17 on the third fin 113, the fourth fin 114, the fifth fin 115, and the sixth fin 116.

[0109] In some embodiments, a similar method can be used to selectively remove the third work function layer 16 on the first fin 111, second fin 112, and third fin 113, while retaining the third work function layer 16 on the fourth fin 114, fifth fin 115, and sixth fin 116, to selectively remove the fourth work function layer 17 on the first fin 111 and second fin 112, while retaining the fourth work function layer 17 on the third fin 113, fourth fin 114, fifth fin 115, and sixth fin 116. That is, a dielectric layer is first formed again on the surface of the substrate 10, covering the top of each fin 11. Then, the dielectric layer on the first fin 111 to the second fin 112 is selectively removed, while the dielectric layer on the third fin 113 to the sixth fin 116 is retained, exposing the fourth work function layer 17 on the first fin 111 to the second fin 112. Next, the fourth work function layer 17 located on the first fin 111 to the second fin 112 is removed, and then the remaining dielectric layers on the third fin 113 to the sixth fin 116 are removed to obtain the structure shown in FIG8.

[0110] In some embodiments, a fourth oxidation treatment (first treatment) is performed on the surface of the fourth work function layer 17 located on the third fin 113 to the sixth fin 116 and the surface of the first work function layer 12 located on the first fin 111 to the second fin 112.

[0111] In some embodiments, the surface of the fourth work function layer 17 located on the third fin 113 to the sixth fin 116 and the surface of the first work function layer 12 located on the first fin 111 to the second fin 112 are subjected to a fourth cleaning treatment (second treatment) and a fourth oxidation treatment (first treatment) in sequence.

[0112] In some embodiments, similarly, the same method as described above for performing a third oxidation treatment (first treatment) (or sequentially performing a third cleaning treatment (second treatment) and a third oxidation treatment (first treatment)) on the surfaces of the first work function layer 12 on the first fins 111 to the third fins 113 and the third work function layer 16 on the fourth fins 114 to the sixth fins 116, can be used to perform a fourth oxidation treatment (first treatment) (or sequentially performing a fourth cleaning treatment (second treatment) and a fourth oxidation treatment (first treatment)) on the surfaces of the fourth work function layer 17 on the third fins 113 to the sixth fins 116 and the first work function layer 12 on the first fins 111 to the second fins 112, in order to reduce the surface roughness of the treated fourth work function layer 17 and the surface roughness of the first work function layer 12 on the first fins 111 to the second fins 112, which are then treated again. Furthermore, during the fourth oxidation treatment, the oxide layer (fourth oxide layer) formed on the surface of the treated TiN material's fourth work function layer 17 is a TiON layer (TiO2).x N y The oxide layer (fourth oxide layer) formed on the surface of the first work function layer 12 of the TaN material, which has been treated again, is still a TaON layer (TaO). x N y layer).

[0113] In some embodiments, after the second processing and before the first processing, a third processing is performed on the surfaces of the first work function layer 12 on each fin 11 before the formation of the second work function layer 14, the exposed surfaces of the first work function layer 12 and the retained surfaces of the second work function layer 14 before the formation of the third work function layer 16, the exposed surfaces of the first work function layer 12 and the retained surfaces of the third work function layer 16 before the formation of the fourth work function layer 17, and the exposed surfaces of the first work function layer 12 and the retained surfaces of the fourth work function layer 17 before the formation of the fifth work function layer. Nitrogen free radicals can be obtained by exciting nitrogen gas with helium metastable particles and filtering out charged particles therein. Helium metastable particles can be obtained by exciting helium gas and filtering out charged particles therein.

[0114] By using nitrogen free radicals for nitriding treatment (the third treatment), nitrogen atoms are injected into the treated surface, allowing for precise control of the surface nitrogen content, repair of nitrogen vacancies, alteration of the Fermi level position, and the formation of a nitrogen-rich surface layer (TaN) on the treated surface. x / TiN x This allows for precise adjustment of the stoichiometry and work function (the work function is closely related to the nitrogen content of the material layer). Furthermore, based on the already optimized nitrided surface, further oxidation treatment (the first treatment) can be used to eliminate surface roughness, achieving surface smoothing and interface stabilization. This also helps to lock in the chemical state achieved in the previous nitriding adjustment, preventing nitrogen loss in subsequent processes, thereby enhancing the long-term stability of the threshold voltage.

[0115] Step S16: Form a fifth work function layer on the surface of the fourth work function layer and on the surface of the first work function layer exposed on the first fin to the second fin.

[0116] Referring to Figure 9. In some embodiments, a deposition process may be used to form a fifth work function layer 18 on the surface of the first work function layer 12, which has undergone a fourth oxidation treatment and is now smoothed, and on the surface of the fourth work function layer 17, which has undergone a fourth oxidation treatment and is now smoothed.

[0117] In some embodiments, the fifth work function layer 18 includes a TiAl layer.

[0118] In some embodiments, the thickness of the fifth work function layer 18 is 20 Å to 60 Å. For example, the thickness of the fifth work function layer 18 may be 20 Å, 21 Å, 22 Å, 25 Å, 28 Å, 30 Å, 35 Å, 40 Å, 45 Å, 50 Å, 55 Å or 60 Å, or any value between any two of the aforementioned thickness values.

[0119] In some embodiments, the fifth work function layer 18 includes a TiAlC layer (a titanium-aluminum compound layer containing carbon (C)). By employing a TiAlC layer as the outermost work function layer, the lattice structure and electronic properties of the material can be optimized by introducing carbon elements, thereby enabling more precise and stable control of the transistor's work function and threshold voltage (Vth). Specifically, the added C elements form more complex chemical bonds with Ti and Al or fill the lattice interstices, slightly altering the electronic density of states near the Fermi level of the material, thus achieving precise fine-tuning of the work function value to several decimal places. This is crucial for differentiating transistors of different specifications, such as ultra-low power (ULP), standard performance (SVt), and high performance (HVt), at advanced nodes. Furthermore, the addition of C helps stabilize the microstructure of TiAl, preventing phase transitions or excessive grain growth during subsequent high-temperature processes (such as annealing). Simultaneously, C atoms effectively suppress the diffusion of Al atoms into the gate dielectric layer (high-K material), avoiding threshold voltage drift and reliability issues. Therefore, using a TiAlC layer as the outermost work function layer can optimize the lattice structure and electronic properties of the material, enabling more precise and stable control of the work function and threshold voltage of the transistor, thereby significantly improving the stability and yield of the device.

[0120] In some embodiments, after depositing the TiAlC layer, the surface of the TiAlC layer is subjected to a fourth treatment to remove carbon impurities adsorbed on the surface of the TiAlC layer, thereby stabilizing the work function, optimizing performance, and providing an active deposition surface for subsequent film deposition.

[0121] In some embodiments, H2 can be used to perform a fourth treatment on the surface of the deposited TiAlC layer.

[0122] In some embodiments, after depositing the fifth work function layer 18, a top diffusion barrier layer may be formed on the surface of the fifth work function layer 18, and a gate electrode layer may be formed on the surface of the top diffusion barrier layer. This completes the fabrication of the entire metal gate stack structure.

[0123] In some embodiments, the top diffusion barrier layer comprises a TiN layer.

[0124] In some embodiments, the gate electrode layer includes a tungsten (W) layer.

[0125] According to a second aspect of this application, embodiments of this application also provide a metal gate device structure, which is obtained using the metal gate device structure fabrication method provided in any of the embodiments of the first aspect above.

[0126] Referring to FIG9. In some embodiments, a metal gate device structure is disposed on a substrate 10, including a first fin 111 of a first device region A (NLVT region), a second fin 112 of a second device region B (NULVT region), a third fin 113 of a third device region C (NSVT region), a fourth fin 114 of a fourth device region D (PSVT region), a fifth fin 115 of a fifth device region E (PLVT region), and a sixth fin 116 of a sixth device region F (PULVT region) disposed on the substrate 10. An isolation structure 13 for isolating each device region is provided on the substrate 10 surrounding each fin 11. The surface of the first fin 111 is provided with a first work function layer 12 and a fifth work function layer 18 in sequence. The surface of the second fin 112 is provided with a first work function layer 12 and a fifth work function layer 18 in sequence. The surface of the third fin 113 is provided with a first work function layer 12, a fourth work function layer 17 and a fifth work function layer 18 in sequence. The surface of the fourth fin 114 is provided with a first work function layer 12, a third work function layer 16, a fourth work function layer 17 and a fifth work function layer 18 in sequence. The surface of the fifth fin 115 is provided with a first work function layer 12, a second work function layer 14, a third work function layer 16, a fourth work function layer 17 and a fifth work function layer 18 in sequence. The surface of the sixth fin 116 is provided with a first work function layer 12, a second work function layer 14, a third work function layer 16, a fourth work function layer 17 and a fifth work function layer 18 in sequence. By utilizing the metal gate stacked structure of the first device region A (NLVT region), the second device region B (NULVT region), the third device region C (NSVT region), the fourth device region D (PSVT region), the fifth device region E (PLVT region), and the sixth device region F (PULVT region), work function layers with different thicknesses (number of layers) are formed, thereby enabling the control of the turn-on voltage of different device regions, i.e., realizing customized threshold voltage.

[0127] Furthermore, by using oxygen free radicals excited by metastable particles, the surfaces of the first work function layer 12 on each fin 11 before the formation of the second work function layer 14, the exposed surfaces of the first work function layer 12 and the retained surfaces of the second work function layer 14 before the formation of the third work function layer 16, the exposed surfaces of the first work function layer 12 and the retained surfaces of the third work function layer 16 before the formation of the fourth work function layer 17, and the exposed surfaces of the first work function layer 12 and the retained surfaces of the fourth work function layer 17 before the formation of the fifth work function layer 18 are respectively subjected to a first treatment, which reduces the roughness of the treated surfaces and stabilizes the interfacial stoichiometry, thereby stabilizing the metal work function, reducing the fluctuation of the threshold voltage, and improving the stability of the turn-on voltage regulation.

[0128] In a third aspect, embodiments of this application also provide a plasma processing apparatus for performing the metal gate device structure fabrication method corresponding to the above embodiments to form the metal gate device structure corresponding to the above embodiments. The plasma processing apparatus includes inductively coupled plasma (ICP) etching equipment or capacitively coupled plasma (CCP) etching equipment, etc.

[0129] In other aspects, embodiments of this application also provide an electronic device, including a metal gate device structure obtained using the metal gate device structure fabrication method of the above embodiments. The electronic device can be a storage device, mobile phone, computer, tablet computer, electronic instrument, television, artificial intelligence device, etc.

[0130] In summary, the embodiments of this application utilize oxygen free radicals excited by metastable particles to perform a first treatment on the surfaces of the first work function layer 12 to the fourth work function layer 17, which are the surfaces to be treated. This enables a near-damage-free surface oxidation treatment with lower energy and achieves atomic-level chemical mechanical smoothing of the treated rough surfaces, reducing micro-roughness (RMS). This reduces the fluctuation of the threshold voltage, improves the stability of the turn-on voltage regulation, and ultimately enhances the stability (Vth stability) and yield of devices at advanced nodes.

[0131] The above are merely preferred embodiments of this application. These embodiments are not intended to limit the scope of protection of this application. Therefore, any equivalent changes made based on the description and drawings of this application should also be included within the scope of protection of this application.

Claims

1. A method for fabricating a metal gate device structure, characterized in that, include: Multiple fins, including a first fin, a second fin, a third fin, a fourth fin, a fifth fin, and a sixth fin, are formed on a substrate; A first work function layer and a second work function layer are sequentially formed on the surface of each of the fins; the second work function layer on the first to fourth fins is selectively removed, and a third work function layer is formed on the exposed surface of the first work function layer and on the surface of the second work function layer retained on the fifth to sixth fins; the third work function layer on the first to third fins is selectively removed, and a fourth work function layer is formed on the exposed surface of the first work function layer and on the surface of the third work function layer retained on the fourth to sixth fins; the fourth work function layer on the first to second fins is selectively removed, and a fourth work function layer is formed on the exposed surface of the first work function layer. On the surface, a fifth work function layer is formed on the surface of the fourth work function layer retained on the third to sixth fins; wherein, using oxygen free radicals excited by metastable particles, a first treatment is performed on the surface of the first work function layer on each of the fins before the formation of the second work function layer, the surface of the exposed first work function layer and the surface of the retained second work function layer before the formation of the third work function layer, the surface of the exposed first work function layer and the surface of the retained third work function layer before the formation of the fourth work function layer, and the surface of the exposed first work function layer and the surface of the retained fourth work function layer before the formation of the fifth work function layer, respectively, to reduce the roughness of the treated surfaces.

2. The method for fabricating a metal gate device structure according to claim 1, characterized in that, The first treatment is performed using oxygen free radicals to oxidize the surface being treated, thereby generating an oxide layer on the surface. The oxide layer fills in and smooths the microscopic undulations on the surface being treated, achieving atomic-level chemical mechanical smoothing of the surface being treated.

3. The method for fabricating a metal gate device structure according to claim 2, characterized in that, The oxide layer also serves as a diffusion barrier layer to suppress element diffusion and stabilize the interfacial stoichiometry.

4. The method for fabricating a metal gate device structure according to claim 2, characterized in that, The first work function layer includes a TaN layer, the second work function layer, the third work function layer and the fourth work function layer include a TiN layer, the fifth work function layer includes a TiAl layer, and the oxide layer includes a TaON layer formed on the surface of the TaN layer and a TiON layer formed on the surface of the TiN layer.

5. The method for fabricating a metal gate device structure according to claim 1, characterized in that, The oxygen free radicals are obtained by exciting oxygen with helium metastable particles and filtering out charged particles. The helium metastable particles are obtained by exciting helium gas and filtering out charged particles. During the first treatment, the helium flow rate is 1000 sccm to 9000 sccm, the oxygen flow rate: helium flow rate = 1:1 to 10:1, the temperature is 50℃ to 180℃, the source power is 100W to 1000W, the pressure is 100mTorr to 1000mTorr, the time is 30s to 300s, and the ion filter is turned on while the bias power is turned off.

6. The method for fabricating a metal gate device structure according to claim 1, characterized in that, The thickness of the first work function layer is 8 Å to 15 Å; and / or, the thickness of the second work function layer is 5 Å to 10 Å; and / or, the thickness of the third work function layer is 5 Å to 10 Å; and / or, the thickness of the fourth work function layer is 5 Å to 15 Å; and / or, the thickness of the fifth work function layer is 20 Å to 60 Å.

7. The method for fabricating a metal gate device structure according to claim 1, characterized in that, Also includes: The surfaces of the first work function layer on each of the fins before the formation of the second work function layer, the exposed surface of the first work function layer and the retained surface of the second work function layer before the formation of the third work function layer, the exposed surface of the first work function layer and the retained surface of the third work function layer before the formation of the fourth work function layer, and the exposed surface of the first work function layer and the retained surface of the fourth work function layer before the formation of the fifth work function layer are respectively subjected to a second treatment to clean and activate the treated surfaces.

8. The method for fabricating a metal gate device structure according to claim 7, characterized in that, The second treatment was performed using NH4OH and isopropanol in sequence.

9. The method for fabricating a metal gate device structure according to claim 8, characterized in that, The isopropanol is used at a temperature of 50℃ to 80℃.

10. A metal gate device structure, characterized in that, It is obtained using the metal gate device structure fabrication method as described in any one of claims 1-9.

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