A method of filling tungsten

Abstract

The application discloses a tungsten filling method. The method comprises the following steps: providing a substrate in a reaction cavity, the substrate comprising a medium layer, and the medium layer having a plurality of recess structures extending in a horizontal direction; introducing a first reaction gas into the reaction cavity, the first reaction gas comprising a hydrogen-containing gas, which is adsorbed on the inner wall surface of the recess structures; introducing a second reaction gas and an auxiliary gas into the reaction cavity, the second reaction gas comprising a tungsten-containing precursor, and the auxiliary gas at least comprising nitrogen, the tungsten-containing precursor reacting with the hydrogen-containing gas adsorbed on the inner wall surface of the recess structures to grow tungsten; and wherein the first reaction gas, the second reaction gas and the auxiliary gas are pumped into the reaction cavity in a pressure-retaining mode. After introducing nitrogen into the auxiliary gas, the application can significantly reduce the fluorine content and the resistivity of the deposited tungsten layer, and improve the device performance and reliability.

Description

Technical Field

[0001] This invention relates to the field of semiconductors, and more specifically to a method for filling tungsten. Background Technology

[0002] In memory devices, tungsten is primarily used in the word lines (WL) and contacts of 3D NAND flash memory. Currently, as the size of 3D NAND devices continues to shrink, the tungsten filling size within the word lines is also decreasing. However, compared to larger feature areas, the tungsten filling effect in smaller feature areas more readily impacts memory device performance. The smaller the feature area, the thinner the tungsten layer, making it more likely that fluorine in the tungsten layer will diffuse into the device through the thinner film, potentially leading to device failure. Furthermore, a thinner tungsten layer results in a smaller grain size, which increases electron scattering at grain boundaries, leading to increased tungsten layer resistance and ultimately reducing device response speed.

[0003] Therefore, how to reduce the fluorine content and resistivity of the tungsten layer filling the word lines is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a tungsten filling method to reduce the fluorine content and resistivity in the filled tungsten layer.

[0005] To achieve the above objectives, the present invention provides a tungsten filling method, comprising:

[0006] A substrate is provided and placed in a reaction chamber. The substrate includes a dielectric layer having a plurality of recessed structures extending in a horizontal direction.

[0007] A first reaction gas, including a hydrogen-containing gas, is introduced into the reaction chamber and adsorbed onto the inner wall surface of the recessed structure.

[0008] A second reaction gas and an auxiliary gas are introduced into the reaction chamber. The second reaction gas includes a tungsten-containing precursor, and the auxiliary gas includes at least nitrogen. The tungsten-containing precursor reacts with a hydrogen-containing gas adsorbed on the inner wall surface of the recessed structure to grow tungsten.

[0009] The first reaction gas, the second reaction gas, and the auxiliary gas are all pumped into the reaction chamber by a pressure-boosting method.

[0010] Optionally, the auxiliary gas further includes an inert gas, wherein nitrogen accounts for 1%-60% by volume in the auxiliary gas.

[0011] Optionally, nitrogen accounts for 10%-40% of the auxiliary gas by volume.

[0012] Optionally, nitrogen accounts for 15%-25% of the auxiliary gas by volume.

[0013] Optionally, the inert gas includes either argon or helium.

[0014] Optionally, the hydrogen-containing gas includes hydrogen gas.

[0015] Optionally, the tungsten-containing precursor includes tungsten hexafluoride.

[0016] Optionally, the pressure of the first reactant gas is 300 Torr-400 Torr.

[0017] Optionally, the pressure of the second reactant gas is 300 Torr-400 Torr.

[0018] Optionally, the first reactant gas, the second reactant gas, and the auxiliary gas are cyclically and alternately introduced until the grown tungsten fills the recessed structure.

[0019] Optionally, during the alternating introduction of the first reaction gas, the second reaction gas, and the auxiliary gas, the reaction chamber is purged with a purge gas between the two processes.

[0020] Optionally, the purging gas is pumped into the reaction chamber in a pressurized manner.

[0021] Optionally, the purge gas pressure is 500 Torr-600 Torr.

[0022] Optionally, the purging gas includes either argon or helium.

[0023] Optionally, the time for introducing the first reaction gas once is 0.1s-0.2s, the time for introducing the second reaction gas once is 0.1s-0.2s, and the time for introducing the purge gas once is 0.2s-0.4s.

[0024] Optionally, the chamber temperature of the reaction chamber is 400℃-450℃, and the chamber pressure is 5 Torr-30 Torr.

[0025] Optionally, the height of the recessed structure is 5nm-50nm and the length is ≤2μm.

[0026] Optionally, the dielectric layer comprises alternating stacked silicon nitride and silicon oxide layers, wherein the recessed structure is formed after the silicon nitride layer in the dielectric layer is removed.

[0027] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0028] (1) Compared with the existing ALD process for growing tungsten, the present invention introduces a portion of nitrogen into the auxiliary gas that is introduced simultaneously with the second reaction gas (including tungsten-containing precursor). After the nitrogen is introduced, the fluorine content and resistivity in the deposited tungsten layer can be significantly reduced, thereby improving the device performance and reliability.

[0029] (2) The increase in nitrogen content in the auxiliary gas introduced simultaneously with the second reaction gas (including tungsten precursor) is beneficial to reducing the surface roughness of the deposited tungsten layer, which in turn helps to improve the surface smoothness of the subsequently deposited tungsten layer, thereby improving the filling quality and avoiding the generation of filling defects in the recessed structure. Attached Figure Description

[0030] Figure 1 A flowchart of the tungsten filling method provided by the present invention.

[0031] Figures 2A-2D This is a cross-sectional structural diagram illustrating the formation of the recessed structure and the tungsten filling process according to an embodiment of the present invention.

[0032] Figure 3 This is a graph showing the relationship between the resistivity of the tungsten layer and the volume percentage of nitrogen in the inert gas in an embodiment of the present invention.

[0033] Figure 4 This is a graph showing the relationship between the surface roughness of the tungsten layer and the volume ratio of nitrogen in the inert gas in an embodiment of the present invention.

[0034] Figure 5 This is a comparison chart of the fluorine content at different depths of tungsten layers grown using the processes of Example 4 and the comparative example of the present invention. The upper curve in the chart represents the results of the comparative example, and the lower curve represents the results of the embodiments of the present invention.

[0035] Figure 6 This is a graph showing the relationship between the tungsten growth rate and the volume percentage of nitrogen in the inert gas in an embodiment of the present invention.

[0036] Attached Figure Labels

[0037] Substrate 100, substrate 10, dielectric layer 20, silicon oxide layer 201, silicon nitride layer 202, recessed structure 30, storage area 40, opening 50, tungsten layer 60. Detailed Implementation

[0038] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0040] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0041] In the manufacturing process of 3D NAND memory, a stacked 3D NAND memory structure is achieved by vertically stacking multiple layers of data storage cells. When filling to form word lines, the silicon nitride layer in the stacked layers is removed, leaving a silicon oxide layer. Gaps (i.e., horizontally extending recessed structures) exist between the silicon oxide layers, and tungsten metal is filled into these gaps to form word lines. To fill the word lines with a tungsten layer on the substrate, conventional methods typically introduce a tungsten-containing precursor, a reducing gas, and an auxiliary gas into the word line feature area. The auxiliary gas is generally an inert gas such as argon, used as a carrier gas. Through atomic layer deposition (ALD), pulse deposition, or a combination of ALD / pulse deposition and chemical vapor deposition, the reducing gas and tungsten-containing precursor are deposited within the word line feature area to form a tungsten layer.

[0042] However, as described in the background section, as the size of 3D NAND devices continues to shrink, the tungsten filling size inside the word lines also decreases, resulting in a thinner tungsten layer. This not only increases the tungsten layer resistance and reduces the device response speed, but also allows fluorine in the tungsten layer to diffuse into the device through the thinner film, ultimately leading to device failure. Reducing the fluorine content and resistivity of the tungsten layer inside the word lines is a major technical challenge that urgently needs to be overcome in this field.

[0043] To address the aforementioned technical problems, this invention provides a tungsten-filling method for filling a tungsten layer within a horizontally extending recessed structure in a substrate dielectric layer. Specifically, atomic layer deposition (ALD) is employed, with tungsten growth achieved by alternately introducing a first reactive gas (including a hydrogen-containing gas), a second reactive gas (including a tungsten-containing precursor), and an auxiliary gas (at least nitrogen). It is important to emphasize that, unlike conventional ALD tungsten growth processes where the auxiliary gas is an inert gas such as argon (as a carrier gas), this invention discovers that introducing a portion of nitrogen into the auxiliary gas introduced simultaneously with the second reactive gas (including the tungsten-containing precursor) can significantly reduce the fluorine content and resistivity of the deposited tungsten layer, thereby improving device performance and reliability.

[0044] To better understand the technical solution and effects of the present invention, the following will describe them in detail with reference to specific embodiments.

[0045] like Figure 1 As shown in Figure 2, the present invention provides a tungsten filling method, comprising:

[0046] Step S1: A substrate 100 is placed in the reaction chamber. The substrate 100 includes a dielectric layer 20, which has a plurality of recessed structures 30 extending in the horizontal direction.

[0047] As a specific example, the substrate 100 described in this embodiment is ultimately used to form a 3D NAND memory. The structural composition of the substrate 100 and the method for forming the recessed structure 30 are roughly as follows:

[0048] like Figure 2A As shown, the substrate 100 includes a substrate 10 and a dielectric layer 20 located above the substrate 10. The substrate 10 can be a silicon substrate, a germanium substrate, a germanium-silicon substrate, etc. In other embodiments, the substrate 10 can also be a substrate including other elemental semiconductors or compound semiconductors, such as GaAs, InP, or SiC. In this example, the substrate 10 is a silicon substrate.

[0049] The dielectric layer 20 is formed by alternating stacked silicon oxide layers 201 and silicon nitride layers 202. It can be formed by sequentially and alternately depositing silicon oxide layers 201 and silicon nitride layers 202 over the substrate 10 using chemical vapor deposition, atomic layer deposition, or other suitable deposition methods. The silicon nitride layer 202 serves as a sacrificial layer, which will be selectively etched away and filled with tungsten metal in subsequent steps to form word lines for the memory device. The number of silicon nitride layers 202 determines the number of memory cells in the vertical direction; therefore, the more layers stacked, the higher the integration density of the memory device. For example, the number of silicon nitride layers 202 in the dielectric layer 20 can be 16, 32, 64, or 128 layers, etc.

[0050] like Figure 2B As shown, the silicon oxide layer 201 and silicon nitride layer 202 in the dielectric layer 20 are then vertically etched through an etching process until the surface of the substrate 10 is exposed, or a portion of the substrate 10 is over-etched, thereby forming a channel hole in the dielectric layer 20. The channel hole is then filled with a charge trapping layer, a channel layer, and oxides, etc., to complete the fabrication of the storage region 40 in the channel hole.

[0051] like Figure 2C As shown, an opening 50 is then formed by vertically etching the silicon oxide layer 201 and silicon nitride layer 202 in the dielectric layer 20 through an etching process, and the silicon nitride layer 202 in the dielectric layer 20 is removed through the opening 50. In some embodiments, an acid solution with a high selectivity for silicon nitride and silicon oxide, such as phosphoric acid (H3PO4), can be selected to achieve selective removal of the silicon nitride layer 202; in other embodiments, other etching methods can also be used to achieve selective removal of the silicon nitride layer 202.

[0052] After removing the silicon nitride layer 202, as Figure 2C As shown, the dielectric layer 30 has a plurality of recessed structures 30 (i.e., word line structures to be filled) extending in the horizontal direction. As the size of 3D NAND devices continues to shrink, the size of the filling within the word lines, i.e., the size of the recessed structures 30, continues to shrink. In some embodiments, the height of the recessed structures 30 is 5nm-50nm, and the length is ≤2μm.

[0053] The recessed structure 30 needs to be filled with tungsten metal, and the tungsten layer needs to have a lower fluorine content and resistivity to reduce the impact of fluorine diffusion and high resistivity on device performance. This invention achieves this objective through subsequent steps S2 and S3.

[0054] Step S2: A first reaction gas is introduced into the reaction chamber. The first reaction gas includes hydrogen-containing gas, which is adsorbed onto the inner wall surface of the recessed structure 30. The first reaction gas is pumped into the reaction chamber by a pressure-pressurization method.

[0055] It should be noted that after completing step S1 and before proceeding to step S2, a thin tungsten nucleation layer needs to be grown on the inner wall surface of the recessed structure 30 as the growth point for the main part of tungsten growth (i.e., the bulk tungsten layer) in the subsequent step S2.

[0056] The subsequent step S2 involves growing a bulk tungsten layer. The first reactant gas introduced is a reducing gas, which adsorbs onto the inner surface of the recessed structure 30 (essentially the surface of the tungsten nucleation layer in this embodiment) and reacts with the subsequently introduced second reactant gas (including a tungsten precursor) to grow tungsten within the recessed structure 30. The first reactant gas includes a hydrogen-containing gas, such as hydrogen (H2) or ammonia (NH3). In this embodiment, the hydrogen-containing gas includes hydrogen gas.

[0057] The first reactant gas is pumped into the reaction chamber using a pressurization process. After pressurization, the first reactant gas is pumped into the reaction chamber at a certain pressure, allowing it to penetrate the recessed structure 30 more quickly, in greater quantity, and deeper. This ensures that the inner wall surface of the recessed structure 30 is saturated with the first reactant gas, improving the filling quality of the tungsten layer. Otherwise, if the first reactant gas is not pressurized, its pressure entering the reaction chamber may be insufficient, leading to insufficient penetration into the recessed structure 30, especially deep within it. This results in unsaturated or uneven adsorption of the first reactant gas on the inner wall surface of the recessed structure 30, causing the subsequently grown tungsten layer to be loose and porous, leading to filling defects and reduced device performance or even failure. As a specific example, the pressurization pressure of the first reactant gas is 300 Torr-400 Torr. Pressures that are too high or too low may cause filling defects in the tungsten layer within the recessed structure 30.

[0058] In some embodiments, the chamber temperature of the reaction chamber is 400°C-450°C, and the chamber pressure is 5 Torr-30 Torr.

[0059] Step S3: A second reaction gas and an auxiliary gas are introduced into the reaction chamber. The second reaction gas includes a tungsten-containing precursor, and the auxiliary gas includes at least nitrogen. The tungsten-containing precursor reacts with hydrogen-containing gas adsorbed on the inner wall surface of the recessed structure 30 to grow tungsten. Both the second reaction gas and the auxiliary gas are pumped into the reaction chamber by pressure buildup.

[0060] The introduced second reactive gas includes a tungsten-containing precursor, which undergoes a redox reaction with a hydrogen-containing gas adsorbed on the inner wall surface of the recessed structure 30, thereby growing tungsten on the inner wall surface of the recessed structure 30. The tungsten-containing precursor includes any one or more of tungsten hexafluoride (WF6), tungsten hexacarbonyl (W(CO)6), and tungsten pentachloride (WCl5). In this embodiment, the tungsten-containing precursor includes WF6.

[0061] The tungsten-containing precursor (e.g., WF6) has a relatively low boiling point, typically requiring increased temperature to vaporize before being transported to the reaction chamber, resulting in a relatively low transport flow rate. During the ALD W process, these tungsten-containing precursors are prone to liquefaction under high pressure; therefore, an auxiliary gas is often used as a carrier gas. This serves two purposes: firstly, to dilute the tungsten-containing precursor and prevent liquefaction under high pressure; and secondly, to accelerate the pressurization process of the tungsten-containing precursor, reducing process time. Typically, the auxiliary gas is an inert gas such as argon or helium. However, this invention is the first to discover that introducing a portion of nitrogen into the auxiliary gas introduced simultaneously with the second reaction gas (including the tungsten-containing precursor) can significantly reduce the fluorine content and resistivity in the deposited tungsten layer, thereby improving device performance and reliability. Furthermore, introducing nitrogen into the auxiliary gas can also simultaneously reduce the surface roughness of the tungsten layer. Low surface roughness indicates high density of the tungsten layer, which helps improve the surface smoothness of subsequent tungsten layer deposition, thereby improving filling quality and preventing filling defects within the recessed structure 30.

[0062] It is worth mentioning that the present invention also attempted to introduce nitrogen gas into the first reaction gas at the same time, but the research results obtained were completely opposite: when nitrogen gas was introduced into the first reaction gas but not into the auxiliary gas introduced at the same time as the second reaction gas (including tungsten precursor), the resistivity of the deposited tungsten layer increased instead.

[0063] It should be further noted that although introducing nitrogen into the auxiliary gas in step S3 has advantages such as reducing the fluorine content, resistivity, and surface roughness of the tungsten layer, a higher nitrogen concentration is not necessarily better. This invention has found that as the nitrogen concentration in the auxiliary gas increases, although the resistivity and surface roughness of the tungsten layer show a continuous decreasing trend or a decreasing-then-stabilizing trend, the growth rate of the tungsten layer shows a trend of first increasing and then decreasing. Furthermore, when the nitrogen ratio in the auxiliary gas is too high, the tungsten layer growth rate is lower than the growth rate when the nitrogen ratio is 0, leading to reduced production capacity.

[0064] Therefore, in some embodiments, considering device production capacity, the auxiliary gas also includes an inert gas, such as argon or helium. In these embodiments, nitrogen accounts for 1%-60% by volume. In other embodiments, nitrogen accounts for 10%-40% by volume. In still other embodiments, nitrogen accounts for 15%-25% by volume. In other embodiments, if production capacity is not considered, and to achieve lower tungsten layer surface roughness and resistivity, the nitrogen concentration in the auxiliary gas can be higher, with nitrogen accounting for 60%-100% by volume. In specific applications, the volume ratio of nitrogen in the auxiliary gas is adjusted according to actual process requirements, device performance requirements, and production capacity needs.

[0065] The second reactant gas is pumped into the reaction chamber using a pressurization method, which helps to improve the filling quality of the tungsten layer within the recessed structure 30. In some embodiments, the pressurization pressure of the second reactant gas is 300 Torr-400 Torr.

[0066] In some embodiments, the first reactant gas, the second reactant gas, and the auxiliary gas are cyclically and alternately introduced until the thickness of the tungsten layer grown within the recessed structure 30 reaches the required process thickness. In other embodiments, the first reactant gas, the second reactant gas, and the auxiliary gas are cyclically and alternately introduced until the grown tungsten completely fills the recessed structure 30, forming a tungsten layer 60. (See attached diagram for the structure.) Figure 2D As shown.

[0067] Furthermore, during the alternating circulation of the first reactant gas, the second reactant gas, and the inert gas, the reaction chamber is purged with a purge gas between them to remove any unreacted first or second reactant gas from the previous step, while avoiding cross-contamination between the first and second reactant gases and improving the quality of the deposited film.

[0068] In some embodiments, the purge gas includes either argon or helium, and the purge gas is pumped into the reaction chamber in a pressurized manner with a pressurization pressure of 500 Torr-600 Torr.

[0069] As a specific example, the time for a single introduction of the first reactant gas is 0.1s-0.2s, the time for a single introduction of the second reactant gas and the auxiliary gas is 0.1s-0.2s, the time for a single introduction of the purge gas is 0.2s-0.4s, and the number of times the gas is introduced alternately in cycles is not limited.

[0070] It should be noted that in some embodiments, the first reactant gas may be introduced first, followed by the second reactant gas and the auxiliary gas, and then introduced alternately; in other embodiments, the second reactant gas and the auxiliary gas may be introduced first, followed by the first reactant gas, and then introduced alternately. This invention does not limit the order in which the first reactant gas, the second reactant gas, and the auxiliary gas are introduced, but it does limit the specific step of nitrogen introduction. Nitrogen must be introduced into the auxiliary gas introduced simultaneously with the second reactant gas; it cannot be introduced into the first reactant gas simultaneously.

[0071] Example 1

[0072] This embodiment provides a tungsten filling method, including:

[0073] Step 101: Provide a substrate placed in the reaction chamber, the substrate comprising a dielectric layer having a plurality of recessed structures extending in a horizontal direction.

[0074] The dielectric layer is a stacked layer composed of alternating stacked silicon oxide and silicon nitride layers. The recessed structure is formed after the silicon nitride layer in the stacked layer is removed. The height of the recessed structure is 25 nm and the length is 1.5 μm.

[0075] The chamber temperature of the reaction chamber is 445°C and the chamber pressure is 10 Torr.

[0076] Step 102: Introduce a first reaction gas into the reaction chamber. The first reaction gas includes H2, which is adsorbed onto the inner wall surface of the recessed structure.

[0077] The first reaction gas is pumped into the reaction chamber by a pressurization method, with a pressurization pressure of 350 Torr.

[0078] Step 103: Purge the reaction chamber with purge gas to remove the residual first reaction gas in the reaction chamber.

[0079] The purge gas includes either argon or helium, and the purge gas is pumped into the reaction chamber by a pressure build-up method, with a pressure build-up pressure of 550 Torr.

[0080] Step 104: Introduce a second reaction gas and an auxiliary gas into the reaction chamber. The second reaction gas includes WF6, and the auxiliary gas is nitrogen and argon (the proportion of nitrogen in the auxiliary gas is 3% by volume). The WF6 reacts with H2 adsorbed on the inner wall surface of the recessed structure to grow tungsten.

[0081] The second reaction gas and the auxiliary gas are both pumped into the reaction chamber by a pressurization method, with a pressurization pressure of 350 Torr.

[0082] Step 105: Purge the reaction chamber with purge gas to remove the residual first reaction gas in the reaction chamber. The specific operation is the same as in step 103.

[0083] Step 106: Repeat steps 102-105, cyclically and alternately introducing the first reactant gas, the second reactant gas, and the auxiliary gas until the grown tungsten fills the recessed structure.

[0084] The time for introducing the first reaction gas in a single run is 0.15s, the time for introducing the second reaction gas and the auxiliary gas in a single run is 0.15s, and the time for introducing the purge gas in a single run is 0.3s.

[0085] Example 2

[0086] Unlike Example 1, in step 104 of Example 2, the auxiliary gas is nitrogen and argon (the proportion of nitrogen in the auxiliary gas is 6% by volume), and the remaining steps and parameters are the same as in Example 1.

[0087] Example 3

[0088] Unlike Example 1, in step 104 of Example 3, the auxiliary gas is nitrogen and argon (the proportion of nitrogen in the auxiliary gas is 16% by volume), and the remaining steps and parameters are the same as in Example 1.

[0089] Example 4

[0090] Unlike Example 1, in step 104 of Example 4, the auxiliary gas is nitrogen (the proportion of nitrogen in the auxiliary gas is 100% by volume), and the remaining steps and parameters are the same as in Example 1.

[0091] Comparative Example

[0092] Unlike Example 1, in step 104 of the comparative example, the auxiliary gas is argon (in the auxiliary gas, the proportion of nitrogen by volume is 0%), and the remaining steps and parameters are the same as in Example 1.

[0093] Some characterization and detection were performed on the tungsten layers deposited in Examples 1-4 and the comparative examples.

[0094] like Figure 3As shown, the resistivity of the tungsten layers deposited in Examples 1-4 and the comparative example was measured. A graph was plotted with the volume percentage of nitrogen in the inert gas as the x-axis and the resistivity of the tungsten layer as the y-axis to show the relationship between the tungsten layer resistivity and the volume percentage of nitrogen in the inert gas. The results show that, under the same conditions, introducing nitrogen into the inert gas reduces the tungsten layer resistivity. Furthermore, as the volume percentage of nitrogen increases, the tungsten layer resistivity initially decreases rapidly (nitrogen volume percentage < 20%) and then gradually stabilizes (nitrogen volume percentage > 20%). This reduction in resistivity helps ensure the device's response speed.

[0095] like Figure 4 As shown, the surface roughness of the tungsten layers deposited in Examples 1-4 and the comparative example was measured. A graph was plotted with the volume percentage of nitrogen in the inert gas as the abscissa and the surface roughness of the tungsten layer as the ordinate, showing the relationship between the surface roughness of the tungsten layer and the volume percentage of nitrogen in the inert gas. The results show that, under the same conditions, introducing nitrogen into the inert gas can reduce the surface roughness of the deposited tungsten layer, and the surface roughness shows a continuous decreasing trend with the increase of the nitrogen volume percentage. The reduction in surface roughness helps to improve the filling quality of the tungsten layer.

[0096] This invention also employs the tungsten growth process of Example 4 and the comparative tungsten growth process to grow tungsten on a flat plate (e.g., TiN), and compares the fluorine content of tungsten layers with different tungsten layer depths obtained by the two processes. The "tungsten layer depth" refers to the vertical distance from top to bottom of the bulk tungsten layer grown on the flat plate. The results are as follows... Figure 5 As shown, under the same conditions, replacing the inert gas with nitrogen can reduce the fluorine content of the tungsten layer. Furthermore, compared to the tungsten layer grown using the comparative process (which does not use nitrogen in the inert gas), the fluorine content of the tungsten layer deposited using the process in Example 4 is consistently lower at different depths than the corresponding depth of the comparative tungsten layer. This reduction in fluorine content helps improve device performance and reliability.

[0097] Although introducing nitrogen into the auxiliary gas is beneficial for reducing the fluorine content and resistivity of the tungsten layer and improving the filling quality, an excessively high nitrogen volume ratio can reduce the tungsten growth rate. See details... Figure 6 The graph shows the relationship between the tungsten growth rate and the volume percentage of nitrogen in the inert gas. As the volume percentage of nitrogen in the inert gas increases, the tungsten growth rate initially rises and then falls. When the nitrogen volume percentage exceeds 65%, the tungsten growth rate is lower than when the nitrogen content in the inert gas is zero, leading to reduced production capacity. Therefore, in practical processes, the appropriate nitrogen volume percentage must be selected based on the device's performance requirements and production capacity needs.

[0098] In summary, this invention provides a tungsten filling method that uses atomic layer deposition (ALD) to fill a tungsten layer into a horizontally extending recessed structure in a substrate dielectric layer. Unlike conventional ALD tungsten growth processes that use inert gases such as argon as carrier gases as auxiliary gases, this invention introduces a portion of nitrogen into the auxiliary gas introduced simultaneously with the second reactive gas (including a tungsten-containing precursor). This significantly reduces the fluorine content and resistivity of the deposited tungsten layer, thereby improving device performance and reliability.

[0099] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for filling tungsten, characterized in that, include: A substrate is provided and placed in a reaction chamber. The substrate includes a dielectric layer having a plurality of recessed structures extending in a horizontal direction. A first reaction gas, including a hydrogen-containing gas, is introduced into the reaction chamber and adsorbed onto the inner wall surface of the recessed structure. A second reaction gas and an auxiliary gas are introduced into the reaction chamber. The second reaction gas includes a tungsten-containing precursor, and the auxiliary gas includes at least nitrogen. The tungsten-containing precursor reacts with a hydrogen-containing gas adsorbed on the inner wall surface of the recessed structure to grow tungsten. The first reaction gas, the second reaction gas, and the auxiliary gas are all pumped into the reaction chamber by a pressure-boosting method.

2. The tungsten filling method as described in claim 1, characterized in that, The auxiliary gas also includes an inert gas, wherein nitrogen accounts for 1%-60% by volume in the auxiliary gas.

3. The tungsten filling method as described in claim 2, characterized in that, In the auxiliary gas, nitrogen accounts for 10%-40% by volume.

4. The tungsten filling method as described in claim 3, characterized in that, In the auxiliary gas, nitrogen accounts for 15%-25% by volume.

5. The tungsten filling method as described in claim 2, characterized in that, The inert gas includes either argon or helium.

6. The tungsten filling method as described in claim 1, characterized in that, The hydrogen-containing gas includes: hydrogen gas.

7. The tungsten filling method as described in claim 1, characterized in that, The tungsten-containing precursor includes tungsten hexafluoride.

8. The tungsten filling method as described in claim 1, characterized in that, The first reaction gas has a pressure of 300 Torr-400 Torr.

9. The tungsten filling method as described in claim 1, characterized in that, The pressure of the second reactant gas is 300 Torr-400 Torr.

10. The tungsten filling method according to any one of claims 1-9, characterized in that, The first reactant gas, the second reactant gas, and the auxiliary gas are alternately introduced in a cycle until the grown tungsten fills the recessed structure.

11. The tungsten filling method as described in claim 10, characterized in that, During the alternating introduction of the first reaction gas, the second reaction gas, and the auxiliary gas, the reaction chamber is purged with a purge gas between the two processes.

12. The tungsten filling method as described in claim 11, characterized in that, The purging gas is pumped into the reaction chamber using a pressurization method.

13. The tungsten filling method as described in claim 12, characterized in that, The purging gas pressure is 500 Torr-600 Torr.

14. The tungsten filling method as described in claim 11, characterized in that, The purging gas includes either argon or helium.

15. The tungsten filling method as described in claim 11, characterized in that, The time for introducing the first reactant gas in a single run is 0.1s-0.2s, the time for introducing the second reactant gas in a single run is 0.1s-0.2s, and the time for introducing the purge gas in a single run is 0.2s-0.4s.

16. The tungsten filling method as described in claim 1, characterized in that, The chamber temperature of the reaction chamber is 400℃-450℃, and the chamber pressure is 5 Torr-30 Torr.

17. The tungsten filling method as described in claim 1, characterized in that, The height of the recessed structure is 5nm-50nm, and the length is ≤2μm.

18. The tungsten filling method as described in claim 1, characterized in that, The dielectric layer comprises alternating stacked silicon nitride and silicon oxide layers, and the recessed structure is formed after the silicon nitride layer in the dielectric layer is removed.

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