Metal gate device structure and method of making the same
By nitriding and oxidizing the inner work function material layer of the high dielectric constant metal gate device structure, combined with the use of a TiAlC layer, the problems of surface roughness and work function material variation were solved, thereby improving voltage stability and long-term reliability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI BANGXIN SEMI TECHNOLOGY CO LTD
- Filing Date
- 2026-04-03
- Publication Date
- 2026-07-03
Smart Images
Figure CN121968624B_ABST
Abstract
Description
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-dielectric-constant 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. These work function layers require multiple thin-film depositions. At advanced nodes, due to the extremely thin thickness of each work function material layer (approximately 0.5nm to 2nm), poor surface roughness (uneven surface) often results in the deposited material. Poor surface roughness of the preceding layer not only directly affects the growth quality of the subsequent layer but also, the superposition of multiple work function materials with certain roughness 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. Furthermore, how to precisely control the work function and prevent changes in the work function during subsequent processes is also a crucial consideration for enhancing the long-term stability of the threshold voltage. Therefore, it is necessary to investigate a process method that can effectively solve the above 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 metal gate device structure and its fabrication method.
[0004] To achieve the above objectives, the technical solution of this application is as follows:
[0005] According to a first aspect of this application, embodiments of this application provide a method for fabricating a metal gate device structure, including:
[0006] Provide substrate;
[0007] Fins are formed on the substrate;
[0008] A work function layer is formed on the surface of the fin, the work function layer comprising multiple layers of work function material stacked sequentially from the inside out;
[0009] Specifically, the surfaces of one or more inner work function material layers formed before the outermost work function material layer are first nitrided using nitrogen free radicals excited by metastable particles to regulate the surface nitrogen content of the inner work function material layers. After the nitriding treatment, oxygen free radicals excited by metastable particles are used for oxidation treatment to reduce the surface roughness of the inner work function material layers and prevent nitrogen loss.
[0010] The outermost work function material layer includes a TiAlC layer.
[0011] In some embodiments, by performing the nitriding treatment, a nitrogen-rich surface layer is formed on the surface of the inner work function material layer, so as to regulate the surface nitrogen content of the inner work function material layer by changing the surface stoichiometry, thereby achieving fine-tuning of the work function.
[0012] In some embodiments, the oxidation treatment is performed to preferentially oxidize the protrusions on the rough surface of the inner work function material layer, and to fill and smooth the micro-undulations on the surface, thereby achieving atomic-level chemical mechanical smoothing of the surface.
[0013] In some embodiments, the oxidation treatment forms a dense oxide layer on the surface of the inner work function material layer to suppress element diffusion between interfaces, stabilize the interfacial stoichiometry, and prevent nitrogen loss.
[0014] In some embodiments, the nitrogen free radical is obtained by exciting nitrogen gas with helium metastable particles and filtering out charged particles therein; the oxygen free radical is obtained by exciting oxygen gas with helium metastable particles and filtering out charged particles therein; and the helium metastable particles are obtained by exciting helium gas and filtering out charged particles therein.
[0015] In some embodiments, during the nitriding treatment, the helium flow rate is 1000 sccm to 9000 sccm, the nitrogen flow rate: helium flow rate = 1:1 to 10:1, the temperature is 50℃ to 200℃, the source power is 1W to 100W, the pressure is 10mTorr to 1000mTorr, and the time is 5s to 300s.
[0016] In some embodiments, during the oxidation process, 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, and the time is 30s to 300s.
[0017] In some embodiments, TiCl4 and trimethylaluminum are used as precursors, and the TiAlC layer is deposited using a self-limiting surface reaction at a temperature of 250°C to 450°C and a pressure of 900 mTorr to 1100 mTorr.
[0018] In some embodiments, the thickness of the TiAlC layer is 20 Å to 100 Å.
[0019] In some embodiments, after the TiAlC layer is formed, the surface of the TiAlC layer is cleaned and activated using hydrogen radicals and argon radicals excited by metastable particles at a temperature of 100°C to 200°C, a pressure of 50 mTorr to 500 mTorr, and a time of 5 s to 300 s.
[0020] In some embodiments, the one or more inner work function material layers include a first work function material layer and n second work function material layers sequentially formed outside the first work function material layer, where n is a natural number including zero.
[0021] In some embodiments, the first work function material layer includes a TaN layer.
[0022] In some embodiments, the second work function material layer includes a TiN layer.
[0023] In some embodiments, the thickness of the first work function material layer is 8 Å to 15 Å.
[0024] In some embodiments, the thickness of the second work function material layer is 5 Å to 15 Å.
[0025] 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.
[0026] The embodiments of this application may have, or at least have, the following advantages:
[0027] (1) By forming a work function layer on the surface of the fin, the work function layer includes multiple layers of work function material stacked sequentially from the inside out. The surfaces of one or more inner work function material layers formed before the outermost work function material layer are subjected to nitriding and oxidation treatments respectively. Nitrogen atoms can be injected into the surface of the inner work function material layer by nitriding treatment, so as to precisely control the surface nitrogen content, repair nitrogen vacancies, change the Fermi level position, and form a nitrogen-rich surface layer, thereby achieving precise adjustment of stoichiometry and work function (work function is closely related to nitrogen content of work function material layer). Furthermore, based on the surface nitriding optimization, oxidation treatment can effectively passivate dangling bonds and active sites on the surface of inner work function material layer, reduce surface energy inhomogeneity, and achieve the desired adjustment of inner work function material. The protrusions on the rough surface of the material layer are preferentially oxidized. The oxidation process can drive slight atomic migration or promote the relaxation of unstable atoms at grain boundaries, effectively "filling" or "smoothing" the microscopic undulations of the original surface. This results in a smoother surface, achieving atomic-level chemical mechanical smoothing of the rough surface of the inner work function material layer, reducing the micro-roughness (RMS). This reduces threshold voltage fluctuations and improves the stability of threshold voltage regulation. Furthermore, the dense oxide layer formed on the surface of the inner work function material layer by oxidation inhibits the interdiffusion of oxygen and / or nitrogen between different work function material layers, stabilizing the interfacial stoichiometry. This suppresses interfacial diffusion and helps lock in the chemical state achieved in the previous nitriding adjustment, preventing nitrogen loss in subsequent processes. Therefore, by reducing the interfacial state density and stabilizing the metal work function, the electrical path to threshold voltage stability is ultimately improved, and the long-term stability of the threshold voltage is enhanced.
[0028] (2) By using helium metastable particles to generate low-energy nitrogen free radicals and oxygen free radicals, it is possible to achieve almost non-damaging surface nitriding and oxidation treatments with lower energy. This effectively avoids the problem of needing to increase the initial value of the film thickness and causing a large loss of the film layer when using surface treatments such as acid washing with excessive intensity. It can also simplify the manufacturing process.
[0029] (3) By using TiAlC layer as the outermost work function material layer, the added C element can form more complex chemical bonds with Ti and Al or fill the interstitial spaces, which can slightly change the electronic state density near the Fermi level of the material, thereby achieving precise fine-tuning of the work function value at the "decimal place" level. In addition, the addition of C also helps to stabilize the microstructure of TiAl and prevent it from undergoing phase transition or excessive grain growth in subsequent high-temperature processes (such as annealing). At the same time, C atoms can effectively suppress the diffusion of Al atoms into the gate dielectric layer (high K material), avoiding threshold voltage drift and reliability problems. Therefore, using TiAlC layer as the outermost work function material layer can optimize the lattice structure and electronic properties of the material, and achieve more precise and stable control of the work function and threshold voltage of the transistor, thereby greatly improving the stability and yield of the device.
[0030] (4) After the TiAlC layer is formed, hydrogen radicals and argon radicals excited by metastable particles are used to clean and activate the surface of the TiAlC layer. This can effectively remove carbon impurities adsorbed on the surface of the TiAlC layer, achieve a stable work function, optimize performance, and provide an active deposition surface for subsequent film deposition.
[0031] In summary, the embodiments of this application can effectively improve the voltage stability of the metal work function and the reliability of the device, and can enhance the long-term stability of the threshold voltage.
[0032] Other advantages of this application will be described in the following detailed description. Attached Figure Description
[0033] Figure 1 This is a flowchart illustrating a method for fabricating a metal gate device structure according to a preferred embodiment of this application.
[0034] Figure 2 This is a schematic diagram of a fin formed on a substrate, provided as a preferred embodiment of this application.
[0035] Figure 3 This is a schematic diagram of a preferred embodiment of the present application after a gate dielectric layer, a TiN cap layer and an amorphous silicon layer are sequentially formed on the fin.
[0036] Figure 4 This is a schematic diagram of a preferred embodiment of the present application after the amorphous silicon layer has been removed.
[0037] Figure 5 This is a schematic diagram of a preferred embodiment of the present application after a first work function material layer, a TiAlC layer, a top diffusion barrier layer and a gate electrode layer are sequentially formed on a TiN cap layer.
[0038] Figure 6This is a schematic diagram of a preferred embodiment of the present application after a first work function material layer, a second work function material layer, a TiAlC layer, a top diffusion barrier layer and a gate electrode layer are sequentially formed on a TiN cap layer.
[0039] Figure 7 This is a schematic diagram of a preferred embodiment of the present application after a first work function material layer, two second work function material layers, a TiAlC layer, a top diffusion barrier layer and a gate electrode layer are sequentially formed on a TiN cap layer.
[0040] Figure 8 This is a schematic diagram of a preferred embodiment of the present application after a first work function material layer, three second work function material layers, a TiAlC layer, a top diffusion barrier layer and a gate electrode layer are sequentially formed on a TiN cap layer.
[0041] In the figure: 10. Substrate; 11. Fin; 12. Isolation structure; 13. Gate dielectric layer; 14. TiN cap layer; 15. Amorphous silicon layer; 16. First work function material layer; 17. TiAlC layer; 18. Top diffusion barrier layer; 19. Gate electrode layer; 20. Fifth work function material layer; 21. Fourth work function material layer; 22. Third work function material layer. Detailed Implementation
[0042] At more advanced nodes, the threshold voltage regulation steps in different device regions require the formation of work function layers of varying thicknesses through multiple thin-film depositions in those regions. The surface roughness of the preceding work function material is crucial before each deposition, as poor surface roughness directly impacts the fluctuation of the threshold voltage. Furthermore, precisely controlling the work function and preventing its variation in subsequent processes are also critical considerations for enhancing the long-term stability of the threshold voltage.
[0043] In view of this, embodiments of this application provide a method for fabricating a metal gate device structure, including:
[0044] Provide substrate;
[0045] Fins are formed on the substrate;
[0046] A work function layer is formed on the surface of the fin, the work function layer comprising multiple layers of work function material stacked sequentially from the inside out;
[0047] Specifically, the surfaces of one or more inner work function material layers formed before the outermost work function material layer are first nitrided using nitrogen free radicals excited by metastable particles to regulate the surface nitrogen content of the inner work function material layers. After the nitriding treatment, oxygen free radicals excited by metastable particles are used for oxidation treatment to reduce the surface roughness of the inner work function material layers and prevent nitrogen loss.
[0048] The outermost work function material layer includes a TiAlC layer.
[0049] This application embodiment involves sequentially performing nitriding and oxidation treatments on the surfaces of one or more inner work function material layers formed before the outermost work function material layer. The nitriding treatment allows for the control of the nitrogen content on the surface of the inner work function material layers, achieving precise adjustment of the stoichiometry and work function. The oxidation treatment achieves atomic-level chemical mechanical smoothing of the rough surface of the inner work function material layers, reducing the micro-roughness (RMS) and inhibiting interfacial diffusion. This helps to lock in the chemical state achieved by the previous nitriding adjustment, preventing nitrogen loss in subsequent processes, thereby improving the electrical path for threshold voltage stability and enhancing the long-term stability of the threshold voltage.
[0050] This application also provides a metal gate device structure, which is obtained using the metal gate device structure fabrication method described above.
[0051] The specific embodiments of this application will now be described in detail with reference to the accompanying drawings.
[0052] refer to Figure 1 In a first aspect, embodiments of this application provide a method for fabricating a metal gate device structure, which may sequentially include the following steps:
[0053] Step S11: Provide a substrate.
[0054] refer to Figure 2 In some embodiments, substrate 10 is used to fabricate a metal gate device structure on substrate 10. 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.
[0055] In some embodiments, substrate 10 may be a substrate wafer.
[0056] Step S12: Form fins on the substrate.
[0057] refer to Figure 2In some embodiments, a patterning process may be used to form protruding fins 11 on the surface of the substrate 10, for further forming a metal gate structure on the surface of the fins 11. An isolation structure 12 is formed on the substrate 10 surrounding the fins 11, the isolation structure 12 defining an active region on the substrate 10 and isolating the device region where the fins 11 are located.
[0058] Step S13: Form one or more inner work function material layers on the surface of the fin, and perform nitriding and oxidation treatments on the surface of each inner work function material layer in sequence.
[0059] In the turn-on voltage regulation steps of different device regions using high dielectric constant metal gate (HKMG) technology, different voltage controls (customized threshold voltages) are achieved by depositing metal work function materials of different thicknesses. Therefore, different work function layers of different thicknesses will be formed in different device regions, and work function layers of different thicknesses need to be formed through multiple thin film depositions.
[0060] In some embodiments, the work function layer includes multiple work function material layers. Specifically, the work function layer includes one or more inner work function material layers and a TiAlC layer (the outermost work function material layer) stacked sequentially from the inside out. The one or more inner work function material layers include a first work function material layer and n second work function material layers sequentially formed outside the first work function material layer, where n is a natural number including zero (e.g., n = 0, 1, 2, 3, etc.).
[0061] refer to Figure 5 In some embodiments, a deposition process may be used to form an inner work function material layer on the surface of the fin 11. In this embodiment, a first work function material layer 16 is formed on the surface of the fin 11 (i.e., the case where there is no second work function material layer (n=0)).
[0062] refer to Figure 6 In some embodiments, a deposition process can be used to form two inner work function material layers on the surface of the fin 11. In this embodiment, a first work function material layer 16 and a second work function material layer (i.e., when the number of second work function material layers is n=1) are formed sequentially from the inside to the outside on the surface of the fin 11. The second work function material layer in this embodiment is referred to as the fifth work function material layer 20. That is, the second work function material layer is composed of the fifth work function material layer 20.
[0063] refer to Figure 7In some embodiments, a deposition process can be used to form three inner work function material layers on the surface of the fin 11. In this embodiment, one first work function material layer 16 and two second work function material layers (i.e., when the number of second work function material layers is n=2) are formed sequentially from the inside to the outside on the surface of the fin 11. In this embodiment, the two second work function material layers are referred to as the fourth work function material layer 21 and the fifth work function material layer 20, respectively, from the inside to the outside. That is, the second work function material layers consist of the fourth work function material layer 21 and the fifth work function material layer 20.
[0064] refer to Figure 8 In some embodiments, a deposition process can be used to form four inner work function material layers on the surface of the fin 11. In this embodiment, one first work function material layer 16 and three second work function material layers (i.e., when the number of second work function material layers is n=3) are formed sequentially from the inside to the outside on the surface of the fin 11. In this embodiment, the three second work function material layers are designated as the third work function material layer 22, the fourth work function material layer 21, and the fifth work function material layer 20, from the inside to the outside. That is, the second work function material layers consist of the third work function material layer 22, the fourth work function material layer 21, and the fifth work function material layer 20.
[0065] In some embodiments, the first work function material layer 16 includes a TaN layer.
[0066] In some embodiments, the second work function material layer (the third work function material layer 22, the fourth work function material layer 21, and the fifth work function material layer 20) includes a TiN layer.
[0067] In some embodiments, the thickness of the first work function material layer 16 is 8 Å to 15 Å. For example, the thickness of the first work function material layer 16 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.
[0068] In some embodiments, the thickness of the second work function material layer is 5 Å to 15 Å. For example, the thickness of the second work function material layer 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.
[0069] In some embodiments, the thickness of the third work function material layer 22 is 5 Å to 10 Å. For example, the thickness of the third work function material layer 22 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.
[0070] In some embodiments, the thickness of the fourth work function material layer 21 is 5 Å to 10 Å. For example, the thickness of the fourth work function material layer 21 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.
[0071] In some embodiments, the thickness of the fifth work function material layer 20 is 5 Å to 15 Å. For example, the thickness of the fifth work function material layer 20 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.
[0072] In some embodiments, the surface of each inner work function material layer (the surface of one or more inner work function material layers formed before the outermost work function material layer (TiAlC layer)) is sequentially subjected to nitriding and oxidation treatments. That is, for Figure 5 The surface of the first work function material layer 16 in the middle is sequentially subjected to nitriding and oxidation treatment, or to... Figure 6 The surfaces of the first work function material layer 16 and the fifth work function material layer 20 are respectively subjected to nitriding and oxidation treatments, or to... Figure 7 The surfaces of the first work function material layer 16, the fourth work function material layer 21, and the fifth work function material layer 20 are respectively subjected to nitriding and oxidation treatments, or to... Figure 8 The surfaces of the first work function material layer 16, the third work function material layer 22, the fourth work function material layer 21, and the fifth work function material layer 20 are subjected to nitriding and oxidation treatments, respectively.
[0073] Nitriding can be performed using nitrogen free radicals excited by metastable particles, and oxidation can be performed using oxygen free radicals excited by metastable particles. Nitrogen free radicals are obtained by exciting nitrogen gas with helium metastable particles and then filtering out charged particles. Oxygen free radicals are obtained by exciting oxygen gas with helium metastable particles and then filtering out charged particles. Helium metastable particles are obtained by exciting helium gas and then filtering out charged particles. By using helium metastable particles to generate low-energy oxygen free 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 film thickness and caused significant film loss, and also simplifies the manufacturing process.
[0074] By sequentially nitriding and oxidizing the surface of each inner work function material layer, the aim is to first regulate the nitrogen content of the treated surface through nitriding, thereby achieving precise adjustment of the stoichiometry and work function; and then, through oxidation, to smooth the surface and stabilize the interface. This allows for voltage regulation and fine-tuning of the work function by adjusting and changing the stoichiometry of the inner work function material layer. Furthermore, oxidation reduces surface roughness, minimizes threshold voltage fluctuations, prevents nitrogen loss, and enhances the long-term stability of the threshold voltage.
[0075] Among these methods, nitriding treatment using nitrogen free radicals allows for precise control of the stoichiometry and threshold voltage. During nitriding, the surface nitrogen content of the treated surface can be precisely controlled, nitrogen vacancies can be repaired, and a nitrogen-rich surface layer can be formed on the inner work function material layer (for the first work function material layer 16 of TaN material, a nitrogen-rich TaN layer can be formed). x On the surface, targeting the second work function layer of TiN material, nitrogen-rich TiN can be formed. x (Surface layer). The mechanism by which it affects the threshold voltage includes: the work function of the inner work function material layer is closely related to its nitrogen content. Through nitriding, nitrogen atoms can be injected into the surface layer of the inner work function material layer, changing the Fermi level position, thereby directly and actively "fine-tuning" the work function of the metal gate and achieving a shift in the threshold voltage. Specifically, by forming a nitrogen-rich surface layer on the inner work function material layer, the surface nitrogen content of the inner work function material layer can be controlled by changing the stoichiometry of the surface layer, thus achieving fine-tuning of the work function. This step aims to set a "baseline threshold voltage" that is closer to the design target.
[0076] Next, by using oxygen free radicals for oxidation treatment, the interface morphology and stability can be "optimized". Based on the surface nitriding optimization, the oxidation treatment further utilizes its ability to effectively passivate dangling bonds and active sites on the surface of the inner work function material layer, reducing surface energy inhomogeneity. This allows for selective preferential oxidation of protrusions on the rough surface of the inner work function material layer. At the nanoscale, the "peaks" (protrusions) of the treated surface 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 oxidation-induced slight atomic migration or the promotion of relaxation of unstable atoms at grain boundaries can "fill" or "smooth" the microscopic undulations of the original surface, making the surface smoother. This achieves atomic-level chemical mechanical smoothing of the rough surface of the inner work function material layer, reducing the micro-roughness (RMS), thereby reducing threshold voltage fluctuations and improving the stability of turn-on voltage regulation. Furthermore, the extremely high chemical reactivity of oxygen free radicals can be utilized to conduct a controlled oxidation reaction with the treated surface at relatively low temperatures, generating an extremely thin (typically a few atomic layers), uniform, and dense oxide layer (for the first work function material layer 16 of TaN material, TaO can be formed). x N y For TiN materials, the second work function layer can form TiO. x N y The transition layer (often a layer of nitrided inner work function material) serves as an interface passivation layer, allowing for further oxidation treatment to eliminate surface roughness, achieving surface smoothing and interface stabilization. Furthermore, the oxidation treatment targets the surface of the nitrided inner work function material layer, which helps lock in the chemical state achieved by the previous nitriding adjustment, inhibiting the interdiffusion of oxygen and / or nitrogen between different work function material layers, stabilizing the interfacial stoichiometry, and preventing nitrogen loss in subsequent processes. Therefore, by reducing the interfacial state density (the smooth, passivated interface significantly reduces charge traps at the interface) and stabilizing the metal work function (the uniform interfacial layer stabilizes the effective work function of each inner work function material layer, preventing it from drifting under electrothermal stress due to interfacial reactions or impurity diffusion), the electrical path for improving threshold voltage stability is ultimately improved, and the long-term stability of the threshold voltage is enhanced.
[0077] In some embodiments, during nitriding, the flow rate ratio of nitrogen to helium is 1 to 10 (nitrogen flow rate: helium flow rate = 1:1 to 10:1). For example, the flow rate ratio of nitrogen 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.
[0078] In some embodiments, the flow rate of helium gas during nitriding is 1000 sccm to 9000 sccm. For example, the flow rate of helium gas 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.
[0079] In some embodiments, the nitriding treatment is performed at a temperature of 50°C to 200°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, 180°C, 190°C, or 200°C, or any value between any two of the aforementioned temperature values.
[0080] In some embodiments, the source power during nitriding is 1W to 100W. For example, the source power can be 1W, 2W, 3W, 4W, 5W, 10W, 20W, 30W, 40W, 50W, 60W, 70W, 80W, 90W, or 100W, or any value between any two of the aforementioned power values.
[0081] In some embodiments, the pressure during nitriding is 10 mTorr to 1000 mTorr. For example, the pressure may be 10 mTorr, 20 mTorr, 30 mTorr, 40 mTorr, 50 mTorr, 100 mTorr, 200 mTorr, 500 mTorr, 700 mTorr, 900 mTorr, or 1000 mTorr, or any value between any two of the aforementioned pressure values.
[0082] In some embodiments, the nitriding treatment is performed for a time of 5s to 300s. For example, the time can be 5s, 6s, 8s, 10s, 20s, 50s, 100s, 150s, 200s, 250s, or 300s, or any value between any two of the aforementioned time values.
[0083] In some embodiments, during nitriding, ion filtering is turned on and bias power is turned off.
[0084] By synergistically controlling the flow ratio, temperature, source power, pressure, time, etc., lower energy nitrogen free radicals can be obtained, enabling shallow nitriding treatment of the surface of the inner work function material layer to form a nitrogen-rich surface layer on the surface of the inner work function material layer.
[0085] In some embodiments, during the oxidation process, 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.
[0086] In some embodiments, the flow rate of helium gas during oxidation treatment is 1000 sccm to 9000 sccm. For example, the flow rate of helium gas 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 rate values.
[0087] In some embodiments, the oxidation treatment is performed at a temperature of 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.
[0088] In some embodiments, the source power during oxidation treatment is 100W to 1000W. 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.
[0089] In some embodiments, the pressure during 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.
[0090] In some embodiments, the oxidation treatment is performed for a time of 30s to 300s. For example, the time can be 30s, 35s, 40s, 45s, 50s, 55s, 60s, 80s, 100s, 130s, 150s, 180s, 200s, 220s, 250s, 290s, or 300s, or any value between any two of the aforementioned time values.
[0091] In some embodiments, during oxidation, ion filtering is turned on and bias power is turned off.
[0092] 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.
[0093] refer to Figure 5 , Figure 6 , Figure 7 or Figure 8 In some embodiments, before forming the first work function material layer 16, a gate dielectric layer 13 (e.g., HfO2) and a TiN cap layer 14 may be formed sequentially on the surface of the fin 11, and then the first work function material layer 16 may be formed on the surface of the TiN cap layer 14.
[0094] In some embodiments, since the deposition thickness of the TiN cap layer 14 is also extremely thin (e.g., 10 Å to 20 Å), poor surface roughness may also exist after deposition. Therefore, before forming the first work function material layer 16, the above-described oxidation process can be used to oxidize the surface of the TiN cap layer 14 to make the surface of the treated TiN cap layer 14 smoother. In particular, a uniform and dense oxide layer (TiO2) is formed on the surface of the TiN cap layer 14 by oxidation treatment. x N y ( ), which can be used as an auxiliary diffusion barrier layer, thereby significantly improving the diffusion barrier capability of the TiN cap layer 14.
[0095] refer to Figure 3 In some embodiments, before forming the first work function material layer 16, an amorphous silicon layer 15 may be deposited on the surface of the TiN cap layer 14 and subjected to peak annealing. After peak annealing, the amorphous silicon layer 15 is then removed, such as... Figure 4 As shown, a first work function material layer 16 is then deposited on the surface of the TiN cap layer 14 after the amorphous silicon layer 15 has been removed, as follows. Figure 5 , Figure 6 , Figure 7 or Figure 8 As shown. The amorphous silicon layer 15 can serve as a sacrificial layer and morphology buffer layer during peak annealing. During subsequent peak annealing, the amorphous silicon layer 15 acts as an oxygen "getter layer," preferentially reacting with diffused oxygen to form SiO. xTo prevent oxygen atoms from diffusing into the channel and thus avoid performance degradation, the amorphous silicon layer 15 can be used to fill any microscopic irregularities on the surface of the TiN cap layer 14, forming a more uniform interface that helps to form a consistent interface reaction during subsequent peak annealing. Peak annealing allows the amorphous silicon layer 15 to react with the TiN cap layer 14 at high temperatures (around 900℃), causing silicon atoms to diffuse into the interlattice 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 14. 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 key to improving the instability of positive and negative bias temperatures and stabilizing the interface stoichiometry.
[0096] Step S14: Form a TiAlC layer on the surface of the outermost inner work function material layer.
[0097] refer to Figure 5 , Figure 6 , Figure 7 or Figure 8 In some embodiments, after sequentially performing nitriding and oxidation treatments on the surface of the outermost inner work function material layer, a deposition process can be used to form a TiAlC layer 17, serving as the outermost work function material layer, on the surface of the outermost inner work function material layer. That is, in... Figure 5 A TiAlC layer 17 is formed on the surface of the first work function material layer 16, or... Figure 6 , Figure 7 or Figure 8 A TiAlC layer 17 is formed on the surface of the fifth work function material layer 20.
[0098] By using TiAlC layer 17 (a titanium aluminum compound layer containing carbon (C)) as the outermost work function material 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 work function and threshold voltage (Vth) of the transistor.
[0099] The core principles and functions of introducing carbon (C) include:
[0100] (1) Work function fine-tuning mechanism. The work function of TiAl itself (usually used in NMOS) is already quite ideal, but after introducing carbon atoms, carbon can form more complex chemical bonds with Ti and Al or fill the interstitial spaces in the lattice. This slightly changes the electronic density of states near the Fermi level of the material, thereby 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.
[0101] (2) Thermal stability and diffusion barrier. 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 13 (a high-K material), as aluminum diffusion contaminates the gate dielectric layer 13, leading to threshold voltage drift and reliability issues. Therefore, using the TiAlC layer 17 as the outermost work function material layer significantly improves the device's stability and yield.
[0102] (3) Interface property optimization. In the process of forming TiAlC layer 17 using atomic layer deposition (ALD), carbon-containing precursors can sometimes bring better film formation properties and interface quality, making the contact with the upper and lower layer materials more ideal and reducing interface defects.
[0103] In summary, introducing TiAlC layer 17 as the outermost work function material layer can meet the challenges of ultra-advanced processes such as 5nm and 3nm, representing an upgrade to conventional TiAl materials. By introducing carbon, the "performance" and "reliability" of the outermost work function material layer are optimized at the atomic scale.
[0104] In some embodiments, an atomic layer deposition process is employed, using TiCl4 and trimethylaluminum (TMA) as precursors (TiCl4 provides Ti, TMA provides Al and C), and a TiAlC layer 17 is deposited on the surface of the outermost inner work function material layer using a self-limiting surface reaction.
[0105] In some embodiments, the temperature for forming the TiAlC layer 17 is 250°C to 450°C. For example, the temperature can be 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 350°C, 380°C, 400°C, 440°C, or 450°C, or any value between any two of the aforementioned temperature values.
[0106] In some embodiments, the pressure during the formation of the TiAlC layer 17 is 900 mTorr to 1100 mTorr. For example, the pressure can be 900 mTorr, 910 mTorr, 930 mTorr, 950 mTorr, 980 mTorr, 1000 mTorr, 1010 mTorr, 1020 mTorr, 1050 mTorr, 1090 mTorr, or 1100 mTorr, or any value between any two of the aforementioned pressure values.
[0107] In some embodiments, the thickness of the TiAlC layer 17 is 20 Å to 100 Å. For example, the thickness of the TiAlC layer 17 can be 20 Å, 21 Å, 24 Å, 25 Å, 27 Å, 30 Å, 35 Å, 40 Å, 45 Å, 50 Å, 55 Å, 60 Å, 65 Å, 70 Å, 75 Å, 80 Å, 85 Å, 90 Å, 95 Å, or 100 Å, or any value between any two of the aforementioned thickness values.
[0108] By using TiCl4 and trimethylaluminum as precursors to deposit TiAlC layers17, atomic-level thickness control, excellent conformability, and uniformity can be achieved through self-limiting surface reactions. Furthermore, the Al content in the film can be precisely controlled by adjusting the dosage of trimethylaluminum, thereby allowing for precise regulation of the work function.
[0109] In some embodiments, after forming the TiAlC layer 17, the surface of the TiAlC layer 17 is cleaned and activated using hydrogen and argon radicals excited by metastable particles. This effectively removes adsorbed carbon impurities from the surface of the TiAlC layer 17, stabilizes the work function, optimizes performance, and provides an active deposition surface for subsequent film deposition. Hydrogen and argon radicals can be obtained by exciting hydrogen and argon gases with helium metastable particles and filtering out charged particles. The helium metastable particles are obtained by exciting helium gas and filtering out charged particles.
[0110] In some embodiments, when cleaning and activating the surface of the TiAlC layer 17, the flow rate ratio of the mixed hydrogen and argon gas to helium is 0.5 to 1 (flow rate of the mixed hydrogen and argon gas: flow rate of helium = 0.5:1 to 1:1). For example, the flow rate ratio of the mixed hydrogen and argon gas to helium can be 0.5, 0.6, 0.7, 0.8, 0.9, or 1, or any value between any two of the aforementioned flow rate ratios.
[0111] In some embodiments, when cleaning and activating the surface of the TiAlC layer 17, the helium flow rate is 1000 sccm to 3000 sccm. For example, the helium flow rate can be 1000 sccm, 1100 sccm, 1300 sccm, 1600 sccm, 1900 sccm, 2000 sccm, 2100 sccm, 2400 sccm, 2800 sccm, or 3000 sccm, or any value between any two of the aforementioned flow rates.
[0112] In some embodiments, the temperature for cleaning and activating the surface of the TiAlC layer 17 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.
[0113] In some embodiments, the pressure is 50 mTorr to 500 mTorr when cleaning and activating the surface of the TiAlC layer 17. For example, the pressure can be 50 mTorr, 60 mTorr, 90 mTorr, 100 mTorr, 150 mTorr, 200 mTorr, 250 mTorr, 300 mTorr, 350 mTorr, 400 mTorr, 450 mTorr, or 500 mTorr, or any value between any two of the aforementioned pressure values.
[0114] In some embodiments, the cleaning and activation treatment of the surface of TiAlC layer 17 takes place over a period of 5 to 300 seconds. For example, the time can be 5 seconds, 7 seconds, 9 seconds, 10 seconds, 15 seconds, 30 seconds, 80 seconds, 100 seconds, 150 seconds, 200 seconds, 250 seconds, or 300 seconds, or any value between any two of the aforementioned time values.
[0115] In some embodiments, after forming the TiAlC layer 17, a gate electrode layer may be formed on the surface of the TiAlC layer 17.
[0116] refer to Figure 5 , Figure 6 , Figure 7 or Figure 8 In some embodiments, a deposition process may be used to first form a top diffusion barrier layer 18 on the surface of the TiAlC layer 17, and then form a gate electrode layer 19 on the surface of the top diffusion barrier layer 18.
[0117] In some embodiments, the top diffusion barrier layer 18 includes a TiN layer.
[0118] In some embodiments, the gate electrode layer 19 includes a tungsten (W) layer.
[0119] This completes the fabrication of the entire metal gate stack structure.
[0120] Secondly, 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.
[0121] refer to Figure 5 , Figure 6 , Figure 7 or Figure 8 In some embodiments, the metal gate device structure is disposed on a substrate 10, including a fin 11 disposed on the substrate 10, and an isolation structure 12 for isolating the active region is disposed on the substrate 10 surrounding the fin 11. A gate dielectric layer 13, a TiN cap layer 14, a work function layer, a top diffusion barrier layer 18, and a gate electrode layer 19 are sequentially disposed on the surface of the fin 11. The work function layer includes multiple work function material layers stacked sequentially from the inside out. Specifically, the work function layer includes one or more inner work function material layers stacked sequentially from the inside out and a TiAlC layer 17 as the outermost work function material layer. The one or more inner work function material layers include a first work function material layer 16 and n second work function material layers sequentially formed outside the first work function material layer 16, where n is a natural number including zero (e.g., n = 0, 1, 2, 3, etc.).
[0122] For example, the work function layer may include a first work function material layer 16 and a TiAlC layer 17 arranged sequentially from the inside out, such as Figure 5 As shown.
[0123] Alternatively, the work function layer may include, from the inside out, a first work function material layer 16, a second work function material layer (a fifth work function material layer 20), and a TiAlC layer 17, as follows: Figure 6 As shown.
[0124] Alternatively, the work function layer may include, from the inside out, a first work function material layer 16, two second work function material layers (a fourth work function material layer 21 and a fifth work function material layer 20), and a TiAlC layer 17, as follows: Figure 7 As shown.
[0125] Alternatively, the work function layer may include, from the inside out, a first work function material layer 16, three second work function material layers (a third work function material layer 22, a fourth work function material layer 21, and a fifth work function material layer 20), and a TiAlC layer 17, as follows: Figure 8 As shown.
[0126] Among them, such as Figure 5 The region where the metal gate device structure is located can be an NLVT (N-type low threshold voltage) region or a NULVT (N-type ultra-low threshold voltage) region. For example... Figure 6 The region where the metal gate device structure is shown can be the NSVT (N-type standard threshold voltage) region. For example... Figure 7 The region where the metal gate device structure is shown can be the PSVT (P-type standard threshold voltage) region. For example... Figure 8The region where the metal gate device structure is located can be a PLVT (P-type low threshold voltage) region or a PULVT (P-type ultra-low threshold voltage) region. By utilizing work function layers of different thicknesses (number of layers) in the metal gate stack structure respectively located in the NLVT, NULVT, NSVT, PSVT, PLVT, and PULVT regions, the turn-on voltage of different device regions can be controlled, i.e., a customized threshold voltage can be achieved.
[0127] Furthermore, by sequentially performing nitriding and oxidation treatments on the surfaces of one or more inner work function material layers formed before the TiAlC layer 17, precise adjustment of the stoichiometry and work function is achieved, along with atomic-level chemical mechanical smoothing of the rough surfaces of the inner work function material layers. This reduces threshold voltage fluctuations, improves the stability of turn-on voltage regulation, stabilizes the interfacial stoichiometry, prevents nitrogen loss in subsequent processes, and ultimately improves the electrical path for threshold voltage stability, enhancing its long-term stability. By using TiAlC layer 17 as the outermost work function material layer, the lattice structure and electronic properties of the material can be optimized, enabling more precise and stable regulation of the transistor's work function and threshold voltage, thereby significantly improving device stability and yield.
[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, this application embodiment utilizes nitrogen and oxygen free radicals excited by metastable particles to sequentially nitrid and oxidize the surfaces of one or more inner work function material layers formed before the outermost work function material layer (TiAlC layer 17). This avoids damage to the treated surfaces. Nitriding can be used to regulate the surface nitrogen content of the inner work function material layers, achieving precise adjustment of the stoichiometry and work function. Furthermore, based on the optimized nitriding, oxidation can be used to achieve atomic-level chemical mechanical smoothing of the rough surface of the inner work function material layers, reducing micro-roughness (RMS) and inhibiting interfacial diffusion. This helps to lock in the chemical state achieved by the previous nitriding adjustment, preventing nitrogen loss in subsequent processes. Consequently, it reduces threshold voltage fluctuations, improves the stability of turn-on voltage regulation, ultimately improves the electrical path of threshold voltage stability, and enhances the long-term stability of the threshold voltage. Furthermore, by using TiAlC layer 17 as the outermost work function material layer, the lattice structure and electronic properties of the material can be optimized, enabling more precise and stable control of the transistor's work function and threshold voltage, thereby significantly improving the device's stability and yield.
[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 of fabricating a metal gate device structure, the method comprising: include: Provide substrate; Fins are formed on the substrate; A work function layer is formed on the surface of the fin, the work function layer comprising multiple layers of work function material stacked sequentially from the inside out; Specifically, the surfaces of one or more inner work function material layers formed before the outermost work function material layer are first nitrided using nitrogen free radicals excited by metastable particles to regulate the surface nitrogen content of the inner work function material layers. After the nitriding treatment, oxygen free radicals excited by metastable particles are used for oxidation treatment to reduce the surface roughness of the inner work function material layers and prevent nitrogen loss. The outermost work function material layer includes a TiAlC layer; The nitrogen free radical is obtained by exciting nitrogen gas with helium metastable particles and filtering out charged particles. The oxygen free radical is 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 performing the nitriding treatment, a nitrogen-rich surface layer is formed on the surface of the inner work function material layer. By changing the stoichiometry of the surface layer of the inner work function material layer, the surface nitrogen content of the inner work function material layer can be controlled, thereby achieving fine-tuning of the work function. By performing the oxidation treatment, the protrusions on the rough surface of the inner work function material layer are preferentially oxidized, and the micro-undulations on the surface are filled and smoothed, achieving atomic-level chemical mechanical smoothing of the surface, reducing micro-roughness, thereby reducing the fluctuation of the threshold voltage and improving the stability of the turn-on voltage regulation. By performing the oxidation treatment and undergoing a controlled oxidation reaction, a dense oxide layer transition layer is formed on the surface of the inner work function material layer, serving as an interface passivation layer, achieving surface smoothing and interface stabilization, suppressing element diffusion between interfaces, stabilizing the interface stoichiometry, and preventing nitrogen loss.
2. The method of claim 1, wherein During the nitriding treatment, the helium flow rate is 1000 sccm to 9000 sccm, the nitrogen flow rate:helium flow rate ratio is 1:1 to 10:1, the temperature is 50℃ to 200℃, the source power is 1W to 100W, the pressure is 10mTorr to 1000mTorr, and the time is 5s to 300s; and / or, during the oxidation treatment, the helium flow rate is 1000 sccm to 9000 sccm, the oxygen flow rate:helium flow rate ratio is 1:1 to 10:1, the temperature is 50℃ to 180℃, the source power is 100W to 1000W, the pressure is 100mTorr to 1000mTorr, and the time is 30s to 300s.
3. The method of claim 1, wherein The TiAlC layer is formed by depositing TiCl4 and trimethylaluminum as precursors using a self-limiting surface reaction at a temperature of 250°C to 450°C and a pressure of 900 mTorr to 1100 mTorr; and / or the thickness of the TiAlC layer is 20 Å to 100 Å.
4. The method of claim 1, wherein After the TiAlC layer is formed, the surface of the TiAlC layer is cleaned and activated using hydrogen radicals and argon radicals excited by metastable particles at a temperature of 100℃~200℃, a pressure of 50mTorr~500mTorr, and a time of 5s~300s.
5. The method of claim 1, wherein The one or more inner work function material layers include a first work function material layer and n second work function material layers formed sequentially outside the first work function material layer, where n is a natural number including zero.
6. The method of claim 5, wherein The first work function material layer includes a TaN layer; and / or, the second work function material layer includes a TiN layer; and / or, the thickness of the first work function material layer is 8 Å to 15 Å; and / or, the thickness of the second work function material layer is 5 Å to 15 Å.
7. A metal gate device structure, characterized by, It is obtained using the metal gate device structure fabrication method as described in any one of claims 1-6.