Method for improving defects of atomic layer deposition silicon nitride film
By optimizing the cleaning process, including high-temperature cleaning and purging cycles, the problem of silicon nitride film defects in the reaction chamber was solved, significantly improving film quality and product yield, especially enhancing device performance in the fabrication of three-dimensional field-effect transistors.
Patent Information
- Application Number
- CN202511002281.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-18
- Publication Date
- 2025-11-04
AI Technical Summary
In the prior art, atomic layer deposition of silicon nitride thin films suffers from incomplete cleaning in the reaction chamber, leading to film defects that affect product yield and reliability.
An optimized cleaning process is employed, including high-temperature cleaning, cooling and heating purging cycles, combined with nitrogen flow rate adjustment, to enhance thermal stress and mechanical peeling effects. Multiple cleaning steps are used to maintain the cleanliness of the reaction chamber.
It significantly reduces the number of defects in silicon nitride films, improves film quality and product yield, and particularly enhances finished product yield and performance in the manufacture of three-dimensional field-effect transistors.
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Figure CN120888896A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to a method for improving defects in atomic layer deposited silicon nitride thin films. Background Technology
[0002] In advanced semiconductor manufacturing processes, such as the fabrication of three-dimensional field-effect transistors, silicon nitride thin films are widely used due to their excellent dielectric properties and functions as etch stop layers, hard masks, or isolation layers. Furnace tube atomic layer deposition is one of the commonly used techniques for preparing silicon nitride thin films.
[0003] In the fabrication process of 3D field-effect transistors (FETs), many critical steps require silicon nitride (SiN) deposition via a furnace tube atomic layer deposition (FLD). However, during this process, unstable byproducts or thin films can easily form on the inner wall of the reaction chamber or the wafer surface. These byproducts may detach during subsequent film deposition processes, forming microparticles that are introduced into the grown SiN film, creating defects. These film defects not only affect the yield of the current process but also negatively impact the processing quality of subsequent patterning, etching, and other process stations, ultimately reducing the overall performance and reliability of the chip.
[0004] To control and reduce such defects, existing technologies typically add an in-situ cleaning step after each major silicon nitride deposition process, often referred to as a "shutter purge." This shutter purge cleans the reaction chamber by using thermal stress to peel off the unstable film adhering to the reaction chamber walls through a cycle between high and low temperatures, which is then carried away by purge gas. Furthermore, to clean the gas jets in the gas delivery path, existing processes also perform an additional "cyclic purge" every few deposition processes (e.g., every five deposition processes).
[0005] Despite the aforementioned cleaning strategies employed in existing technologies, their efficiency in removing minute defects still needs improvement in actual production. After film deposition, a certain number of silicon nitride film defects are still detected on the wafer surface, indicating that existing cleaning process parameters and procedures have not been able to completely and effectively clean the reaction environment. Therefore, defect issues remain a challenge affecting product yield and stability.
[0006] Therefore, the industry urgently needs a more effective method to improve defects in atomic layer deposition silicon nitride thin films to meet the requirements of increasingly sophisticated semiconductor device manufacturing. Summary of the Invention
[0007] The technical problem to be solved by the present invention is to provide a method for improving defects in atomic layer deposition silicon nitride thin films, so as to solve the technical problem mentioned in the background art that the existing cleaning process does not thoroughly clean the reaction chamber, resulting in defects in the atomic layer deposition silicon nitride thin film, affecting product yield and reliability.
[0008] To achieve the above and other related objectives, the present invention provides a method for improving defects in atomic layer deposition (ALD) silicon nitride thin films. The method includes a cleaning step following an ALD silicon nitride thin film deposition step, the cleaning step comprising:
[0009] Step 1: Perform high-temperature cleaning on the reaction chamber at a first temperature within the reaction chamber;
[0010] Step 2: During the process of reducing the temperature of the reaction chamber from the first temperature to the second temperature, at least two cooling and purging cycles are performed;
[0011] Step 3: Perform cryogenic cleaning on the reaction chamber at the second temperature; and
[0012] Step 4: During the process of raising the temperature of the reaction chamber from the first temperature to the second temperature, at least two temperature-raising purge cycles are performed.
[0013] Preferably, in step one, the first temperature is 800°C to 850°C.
[0014] Preferably, in step three, the second temperature is 240–260°C.
[0015] Preferably, in steps two and four, the purging gas used in the cooling purging cycle and the heating purging cycle is nitrogen.
[0016] Preferably, the flow rate of the nitrogen gas is 14 to 18 slm.
[0017] Preferably, in step two, the number of the at least two cooling purging cycles is two.
[0018] Preferably, in step four, the number of the at least two heating and purging cycles is two.
[0019] Preferably, the method is applied to the manufacturing process of three-dimensional field-effect transistors.
[0020] Preferably, the method includes repeating the cleaning step between deposition steps of the plurality of atomic layer deposition silicon nitride films.
[0021] Preferably, after every 5 executions of the deposition step, a step of cleaning the gas jet head used in the deposition step is further included.
[0022] As described above, the method for improving defects in atomic layer deposited silicon nitride thin films of the present invention has the following beneficial effects:
[0023] This invention optimizes the combination of process parameters such as temperature, purging flow rate, and purging cycle number in the cleaning process, thereby synergistically enhancing both thermal stress ablation and mechanical purging cleaning mechanisms. This significantly improves the cleaning efficiency of the reaction chamber, thereby substantially reducing the number of defects in atomic layer deposited silicon nitride films (defect improvement rate can reach approximately 60%) and improving the quality of the film. Attached Figure Description
[0024] Figure 1 The diagram shown is a schematic representation of the process flow of the present invention.
[0025] Figure 2 The diagram shown illustrates the addition of a purging cycle in this invention.
[0026] Figure 3 The diagram shows the temperature and gas flow rate settings in the purging cycle of this invention. Detailed Implementation
[0027] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.
[0028] This invention provides a method for improving defects in atomic layer deposition (ALD) silicon nitride thin films. The method involves performing an optimized cleaning step (i.e., an improved shutter purging step) after the deposition step of an ALD silicon nitride thin film to effectively remove byproducts or unstable films that may form defects in the reaction chamber. This cleaning step includes:
[0029] Step 1: Perform high-temperature cleaning on the reaction chamber at the first temperature.
[0030] In some embodiments, in step one, the first temperature is 800°C to 850°C, for example, 830°C. This high temperature helps to efficiently decompose and peel off highly stable impurities and byproducts adhering to the inner wall of the reaction chamber, ensuring the thoroughness of high-temperature cleaning.
[0031] Step 2: During the process of reducing the temperature of the reaction chamber from the first temperature to the second temperature, at least two cooling purging cycles are performed.
[0032] In some embodiments, please refer to Figure 2In step two, at least two cooling purging cycles are required.
[0033] In some embodiments, please refer to Figure 3 In step two, the purge gas used in the cooling purge cycle is nitrogen, and the nitrogen flow rate is 14 to 18 slm, for example, 15 slm. Compared to the traditional single cooling purge, increasing the number of cooling purge cycles allows for more thorough agitation and purging of the reaction chamber during the cooling process. Furthermore, increasing the purge gas flow rate from the traditional 10 slm to 15 slm enhances the mechanical stripping ability of the gas flow. This combination effectively removes unstable films and particles that have become loose and peeled off due to temperature stress from the chamber, preventing their redeposition in subsequent low-temperature stages, thus significantly improving particle removal efficiency.
[0034] Step 3: Perform low-temperature cleaning on the reaction chamber at the second temperature.
[0035] In some embodiments, in step three, the second temperature is 240–260°C, for example, 250°C. Lowering the low-temperature cleaning temperature from the conventional 300°C to 250°C increases the temperature difference between high-temperature and low-temperature cleaning. This larger temperature difference generates stronger thermal stress, causing stubborn residues adhering to the cavity wall to crack and peel off, thereby significantly improving the removal effect on unstable films and preparing the site for subsequent heated cleaning steps.
[0036] Step 4: During the process of raising the temperature of the reaction chamber from the second temperature to the first temperature, at least two temperature-raising purge cycles are performed.
[0037] In some embodiments, please refer to Figure 2 In step four, at least two heating and purging cycles are required.
[0038] In some embodiments, see also Figure 3 In step four, the purge gas used in the heating and purging cycle can also be nitrogen, and the nitrogen flow rate is also 14 to 18 slm, for example, 15 slm. Similar to the cooling process, adding a purging cycle during the heating process ensures that residual particles stripped from the low-temperature step are thoroughly and cleanly removed from the reaction chamber during the temperature recovery period, preventing secondary contamination of the wafer before the next deposition step begins. This bidirectional enhanced purging strategy results in fewer dead zones and better cleaning performance throughout the entire cleaning process.
[0039] This method may include repeatedly performing a cleaning step between deposition steps that deposit silicon nitride films at multiple atomic layers. By performing this optimized cleaning step after each deposition, a high level of cleanliness in the reaction chamber can be maintained, thereby cumulatively reducing defect density and ensuring stability and consistency across multiple batches of production.
[0040] In some embodiments, after every five deposition steps, a cleaning step is also included for the gas jet head used in the deposition step. This ensures that not only the reaction chamber environment is clean, but also the source of the reaction gas (gas jet head) for deposition is clean, thereby preventing defects introduced by jet head blockage or contamination from the source, achieving comprehensive control over defects, and further improving film quality.
[0041] The method provided in this invention is particularly applicable to the manufacturing process of three-dimensional field-effect transistors (FETs). In devices like three-dimensional field-effect transistors, which have complex structures and extremely high requirements for thin film quality, defects in the silicon nitride (SiN) thin film can severely affect the electrical performance and reliability of the device. This method can significantly reduce the defect rate of the SiN thin film (according to experimental data, the defect improvement rate can reach approximately 60%), thereby effectively improving the yield and performance of the three-dimensional field-effect transistor. Furthermore, this method can also be applied to other semiconductor processes requiring high-quality atomic layer deposition of SiN thin films, such as process nodes of 28 nm and below, and advanced processes involving dual patterning techniques, high-k dielectric gates, embedded SiGe, ultra-low-k thin films, and high aspect ratio fill techniques.
[0042] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.
[0043] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.
Claims
1. A method for improving defects in atomic layer deposited silicon nitride thin films, characterized in that, The method performs a cleaning step after the deposition step of depositing a silicon nitride thin film at one atomic layer, the cleaning step including: Step 1: Perform high-temperature cleaning on the reaction chamber at a first temperature within the reaction chamber; Step 2: During the process of reducing the temperature of the reaction chamber from the first temperature to the second temperature, at least two cooling and purging cycles are performed; Step 3: Perform cryogenic cleaning on the reaction chamber at the second temperature; and Step 4: During the process of raising the temperature of the reaction chamber from the first temperature to the second temperature, at least two temperature-raising purge cycles are performed.
2. The method for improving defects in atomic layer deposited silicon nitride thin films according to claim 1, characterized in that: In step one, the first temperature is 800°C to 850°C.
3. The method for improving defects in atomic layer deposited silicon nitride thin films according to claim 1 or 2, characterized in that: In step three, the second temperature is 240–260°C.
4. The method for improving defects in atomic layer deposited silicon nitride thin films according to claim 1, characterized in that: In steps two and four, the purging gas used in the cooling purging cycle and the heating purging cycle is nitrogen.
5. The method for improving defects in atomic layer deposited silicon nitride thin films according to claim 4, characterized in that: The flow rate of the nitrogen gas is 14 to 18 slm.
6. The method for improving defects in atomic layer deposited silicon nitride thin films according to claim 1, characterized in that: In step two, the number of the at least two cooling purging cycles is two.
7. The method for improving defects in atomic layer deposited silicon nitride thin films according to claim 1, characterized in that: In step four, the number of the at least two heating and purging cycles is two.
8. The method for improving defects in atomic layer deposited silicon nitride thin films according to claim 1, characterized in that: The method is applied to the manufacturing process of three-dimensional field-effect transistors.
9. The method for improving defects in atomic layer deposited silicon nitride thin films according to claim 1, characterized in that: The method includes repeatedly performing the cleaning step between multiple deposition steps of the atomic layer deposition of silicon nitride thin films.
10. The method for improving defects in atomic layer deposited silicon nitride thin films according to claim 1, characterized in that: After every 5 executions of the deposition step, a step of cleaning the gas jet head used for the deposition step is also included.