A method for forming a tungsten film

Abstract

This invention discloses a method for forming a tungsten film. The method includes: placing a semiconductor substrate in a process chamber; introducing a boron-containing gas into the process chamber for immersion treatment; and repeatedly and alternately performing a nucleation layer deposition step and a gas pulse treatment step to form a nucleation layer on the semiconductor substrate. The nucleation layer deposition step includes: sequentially introducing a boron-containing gas and a tungsten-containing gas into the process chamber; the gas pulse treatment step includes: introducing a boron-containing gas into the process chamber; and after the nucleation layer is formed, introducing a tungsten-containing gas and hydrogen gas into the process chamber to form a tungsten film above the nucleation layer. This method can suppress the growth of a boron contaminant layer during the tungsten film formation process, effectively improve the surface morphology of the nucleation layer, and reduce the resistance of the final tungsten film.

Description

Technical Field

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

[0002] With the continuous development of science and technology, the size of semiconductor devices is becoming smaller and smaller, and the requirements for low resistance are becoming more stringent. For metal films, such as tungsten films, the resistance and reliability are usually determined by the nucleation layer. In the formation of a tungsten film, a nucleation layer is formed first, and then the tungsten film is formed on top of the nucleation layer using hydrogen and tungsten-containing gas. Without a stable nucleation layer, it is difficult to form a reliable tungsten film.

[0003] In existing tungsten film processes, when using boron-containing gas to form the nucleation layer, a boron contaminant layer appears, resulting in a poor surface morphology of the nucleation layer and ultimately leading to excessively high resistance in the formed tungsten film. Summary of the Invention

[0004] This application provides a method for forming a tungsten film, which solves the technical problem in the prior art where the resistance of the tungsten film is too high due to the poor surface morphology of the nucleation layer, and achieves the technical effect of improving the surface morphology of the nucleation layer.

[0005] This application provides a method for forming a tungsten film, the method comprising:

[0006] Place the semiconductor substrate in the process chamber;

[0007] Boron-containing gas is introduced into the process chamber for impregnation treatment;

[0008] The nucleation layer deposition step and the gas pulse processing step are repeatedly and alternately performed to form a nucleation layer on the semiconductor substrate, wherein the nucleation layer deposition step includes: sequentially introducing the boron-containing gas and the tungsten-containing gas into the process chamber; the gas pulse processing step includes: introducing the boron-containing gas into the process chamber;

[0009] A tungsten film is formed above the nucleation layer.

[0010] Optionally, the step of introducing boron-containing gas into the process chamber for impregnation includes:

[0011] The boron-containing gas is introduced into the process chamber at a flow rate of 100-500 sccm.

[0012] Optionally, the repeated alternating execution of the nucleation layer deposition step and the gas pulse processing step includes:

[0013] The nucleation layer deposition step and the gas pulse processing step are repeatedly and alternately executed according to the amount of boron-containing gas introduced in each gas pulse processing step. For two consecutive gas pulse processing steps, the amount of boron-containing gas introduced in the previous gas pulse processing step is greater than the amount of boron-containing gas introduced in the next gas pulse processing step.

[0014] Optionally, the amount of boron-containing gas introduced in the next gas pulse processing step is 70% to 90% of the amount of boron-containing gas introduced in the previous gas pulse processing step.

[0015] Optionally, during each nucleation layer deposition step, the pressure in the process chamber is less than or equal to 50 Torr, and the temperature is 250–450°C.

[0016] Optionally, the duration of each nucleation layer deposition step is 0.5 to 5 seconds.

[0017] Optionally, the repeated alternating execution of the nucleation layer deposition step and the gas pulse processing step includes:

[0018] The nucleation layer deposition step and the gas pulse processing step are repeatedly and alternately performed a preset number of times, wherein the preset number of times is 3 to 10.

[0019] Optionally, the thickness of the nucleation layer is 10 to 30 angstroms.

[0020] Optionally, the step of introducing the tungsten-containing gas and hydrogen into the process chamber and forming a tungsten film above the nucleation layer by chemical vapor deposition includes:

[0021] When the pressure in the process chamber is less than or equal to 50 Torr and the temperature is 250 to 450°C, the tungsten film is formed on the nucleation layer.

[0022] Optionally, the boron-containing gas is B2H6, and the tungsten-containing gas is WF6.

[0023] The technical solution provided in this application embodiment involves placing a semiconductor substrate in a process chamber; introducing a boron-containing gas into the process chamber for immersion treatment; and repeatedly alternating between a nucleation layer deposition step and a gas pulse treatment step to form a nucleation layer on the semiconductor substrate. The nucleation layer deposition step includes sequentially introducing a boron-containing gas and a tungsten-containing gas into the process chamber; the gas pulse treatment step includes introducing a boron-containing gas into the process chamber; and after the nucleation layer is formed, introducing a tungsten-containing gas and hydrogen into the process chamber to form a tungsten film above the nucleation layer. In the above solution, the use of a boron-containing gas for immersion treatment minimizes unnecessary contamination gases generated during the nucleation layer deposition process. Furthermore, the introduction of boron-containing gas through a gas pulse treatment step after each nucleation layer deposition step inhibits the growth of the boron contaminant layer, reduces its size, and thus effectively improves the surface morphology of the nucleation layer and reduces the resistance of the final tungsten film. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figures 1-3 This is a schematic cross-sectional view of a tungsten film formation provided in an embodiment of this specification;

[0026] Figure 4 This is a process timing diagram for the formation of a tungsten film provided in an embodiment of this specification. Detailed Implementation

[0027] Embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0028] The accompanying drawings illustrate various structural schematics according to embodiments of the present disclosure. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0029] In the context of this disclosure, when a layer / element is referred to as being "above" another layer / element, the layer / element may be directly above the other layer / element, or there may be an intermediate layer / element between them. Additionally, if a layer / element is "above" another layer / element in one orientation, then when the orientation is reversed, the layer / element may be "below" the other layer / element.

[0030] Example 1

[0031] This specification provides an embodiment of a method for forming a tungsten film, such as... Figures 1-3 The image shown is a cross-sectional schematic diagram of a tungsten film formation method provided in an embodiment of this specification. The method includes the following steps:

[0032] Place the semiconductor substrate in the process chamber;

[0033] Boron-containing gas is introduced into the process chamber for impregnation treatment;

[0034] The nucleation layer deposition step and the gas pulse processing step are repeatedly and alternately performed to form a nucleation layer on the semiconductor substrate, wherein the nucleation layer deposition step includes: sequentially introducing the boron-containing gas and the tungsten-containing gas into the process chamber; the gas pulse processing step includes: introducing the boron-containing gas into the process chamber;

[0035] A tungsten film is formed above the nucleation layer.

[0036] In the embodiments of this specification, the tungsten film formation process is completed in a process chamber. First, the tungsten film is placed in the process chamber, and then the tungsten film is formed on the semiconductor substrate using the tungsten film formation method provided in the embodiments of this specification. The tungsten film formation process mainly includes: forming a nucleation layer on the semiconductor substrate, and forming a tungsten film on the nucleation layer.

[0037] In the specific implementation process, to prevent the tungsten-containing gas used in forming the nucleation layer from reacting with the semiconductor substrate and causing etching, a barrier layer can be formed on the semiconductor substrate before forming the nucleation layer, such as... Figure 1 As shown. Specifically, the barrier layer can be a titanium nitride film, which can be formed by PVD (Physical Vapor Deposition) and / or CVD (Chemical Vapor Deposition).

[0038] Furthermore, a nucleation layer is formed above the barrier layer. In the specific implementation process, a boron-containing gas is first introduced into the process chamber for impregnation. The boron-containing gas can be diluted B₂H₆, for example, diluted with hydrogen or nitrogen. The tungsten-containing gas can also be WF₆ diluted with other gases. This impregnation process roughens the surface of the semiconductor substrate and prevents subsequent tungsten-containing gas from penetrating below the barrier layer. In the embodiments of this specification, B₂H₆ is used as the boron-containing gas. During the impregnation process, the boron-containing gas B₂H₆ is introduced into the process chamber at a flow rate of 100–500 sccm, allowing the B₂H₆ to react on the surface of the semiconductor substrate.

[0039] After the infiltration treatment, the nucleation layer formation step is carried out, such as... Figure 2 As shown, the nucleation layer is formed by repeatedly and alternately performing a nucleation layer deposition step and a gas pulse treatment step. The nucleation layer deposition step involves sequentially introducing a boron-containing gas and a tungsten-containing gas into the process chamber, causing the gases to react on the semiconductor substrate surface to form tungsten nuclei. For example, using B₂H₆ as the boron-containing gas and WF₆ as the tungsten-containing gas, in one nucleation layer deposition step, the steps of sequentially introducing B₂H₆ into the process chamber for a first purge and then introducing WF₆ into the process chamber for a second purge can be performed. During the nucleation layer deposition step, the pressure in the process chamber is less than or equal to 50 Torr, the temperature is 250–450°C, and the duration of each nucleation layer deposition step is 0.5–5 seconds.

[0040] It should be noted that if the nucleation layer is formed solely by repeatedly performing the above-described nucleation layer deposition steps, the boron-containing and tungsten-containing gases that cannot fully react during each cycle will form a boron contamination layer, resulting in a poor morphology of the final nucleation layer. In this embodiment, to avoid the above problem, a gas pulse treatment step is performed after each nucleation layer deposition step. Specifically, the gas pulse treatment step involves introducing boron-containing gas into the process chamber. By alternating between the nucleation layer deposition step and the gas pulse treatment step for a preset number of times, the final nucleation layer is formed, with a thickness of 10–30 angstroms. The preset number of alternating steps is 3–10. In this embodiment, B2H6 diluted with H2 can be used in the gas pulse treatment step; for example, the H2 content is 95% and the B2H6 content is 5%.

[0041] like Figure 3 As shown, after the nucleation layer is formed, tungsten-containing gas and hydrogen are introduced into the process chamber to form a tungsten film above the nucleation layer. The formation of the tungsten film can be achieved by CVD, or by PVD, or a combination of CVD and PVD; no specific method is specified here. When forming the tungsten film by CVD, the pressure in the process chamber is less than or equal to 50 Torr, and the temperature is 250–450 °C.

[0042] In the embodiments of this specification, when forming the nucleation layer, the amount of boron-containing gas introduced in each gas pulse processing step can be determined first. For two consecutive gas pulse processing steps, the amount of boron-containing gas introduced in the previous gas pulse processing step is greater than the amount of boron-containing gas introduced in the next gas pulse processing step. Specifically, the amount of boron-containing gas introduced in the next gas pulse processing step is 70% to 90% of the amount of boron-containing gas introduced in the previous gas pulse processing step.

[0043] Specifically, the amount of boron-containing gas in the gas pulse treatment step is gradually reduced. The specific value of the reduction in the amount of boron-containing gas in each gas pulse treatment step can vary depending on the process temperature, and is not limited here.

[0044] By performing a gas pulse treatment step after each nucleation layer deposition step, the boron contamination layer can be reduced or eliminated. Gradually reducing the amount of boron-containing gas in each pulse treatment step decreases the amount of newly generated boron. Furthermore, when the boron-containing gas is B₂H₆ and the tungsten-containing gas is WF₆, fluorine contamination occurs during nucleation layer formation. Fluorine contamination affects the final tungsten film quality. The gas pulse treatment step is effective in removing the remaining WF₆ from the reaction, thereby reducing fluorine contamination and ensuring the quality of the final tungsten film.

[0045] To better understand the tungsten film formation method provided in the embodiments of this specification, such as Figure 4 The diagram shown is a process timing diagram for tungsten film formation according to an embodiment of this specification. In this embodiment, the boron-containing gas is B2H6, and the tungsten-containing gas is WF6. Figure 4 The horizontal axis represents time, and the vertical axis represents the amount of gas.

[0046] like Figure 4 As shown, after the semiconductor substrate is placed in the process chamber, B2H6 is introduced into the process chamber for immersion treatment (i.e., Pre-Treatment in the figure). Then, one cycle is performed, i.e., one nucleation layer deposition step: B2H6 is introduced into the process chamber for the first purging, and WF6 is introduced for the second purging. Next, Post-Treatment is performed, i.e., one gas pulse treatment step: B2H6 is introduced into the process chamber for purging. The above immersion treatment steps are repeated three times, wherein the amount of B2H6 introduced is gradually reduced each time Post-Treatment, such as by 10% to 30%. Finally, WF6 and H2 are introduced into the process chamber to form a tungsten film by CVD.

[0047] The tungsten film formation method provided in the embodiments of this specification introduces boron-containing gas through a gas pulse treatment step after each completion of the nucleation layer deposition step. This can inhibit the growth of the boron contaminant layer, reduce the size of the boron contaminant layer, effectively reduce fluorine contamination, improve the surface morphology of the nucleation layer, and reduce the resistance of the final tungsten film.

[0048] The above description does not provide detailed explanations of the technical aspects of each layer's patterning, etching, etc. However, those skilled in the art should understand that various technical means can be used to form layers and regions of the desired shape. Furthermore, to form the same structure, those skilled in the art can also design methods that are not entirely identical to those described above. Additionally, although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination.

[0049] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0050] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for forming a tungsten film, characterized in that, The method includes: Place the semiconductor substrate in the process chamber; Boron-containing gas is introduced into the process chamber for impregnation treatment; The nucleation layer deposition step and the gas pulse processing step are repeatedly and alternately performed to form a nucleation layer on the semiconductor substrate, wherein the nucleation layer deposition step includes: sequentially introducing the boron-containing gas and the tungsten-containing gas into the process chamber; the gas pulse processing step includes: introducing the boron-containing gas into the process chamber; A tungsten film is formed above the nucleation layer; The repeated alternating execution of the nucleation layer deposition step and the gas pulse processing step includes: repeatedly alternating the nucleation layer deposition step and the gas pulse processing step according to the amount of boron-containing gas introduced in each gas pulse processing step, wherein, for two consecutive gas pulse processing steps, the amount of boron-containing gas introduced in the previous gas pulse processing step is greater than the amount of boron-containing gas introduced in the next gas pulse processing step.

2. The method according to claim 1, characterized in that, The step of introducing boron-containing gas into the process chamber for impregnation includes: The boron-containing gas is introduced into the process chamber at a flow rate of 100-500 sccm.

3. The method according to claim 1, characterized in that, The amount of boron-containing gas introduced in the next gas pulse processing step is 70% to 90% of the amount of boron-containing gas introduced in the previous gas pulse processing step.

4. The method according to claim 1, characterized in that, During each nucleation layer deposition step, the pressure in the process chamber is less than or equal to 50 Torr, and the temperature is 250~450°C.

5. The method according to claim 1, characterized in that, The duration of each nucleation layer deposition step is 0.5~5s.

6. The method according to claim 1, characterized in that, The repeated alternation of the nucleation layer deposition step and the gas pulse processing step includes: The nucleation layer deposition step and the gas pulse processing step are repeatedly and alternately executed a preset number of times, wherein the preset number of times is 3 to 10.

7. The method according to claim 1, characterized in that, The thickness of the nucleation layer is 10 to 30 angstroms.

8. The method according to claim 1, characterized in that, The process involves introducing the tungsten-containing gas and hydrogen into the process chamber, and forming a tungsten film above the nucleation layer using a chemical vapor deposition process, including: When the pressure in the process chamber is less than or equal to 50 Torr and the temperature is 250~450°C, the tungsten film is formed on the nucleation layer.

9. The method according to any one of claims 1 to 8, wherein the boron-containing gas is B2H6 and the tungsten-containing gas is WF6.

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