A method for improving uniformity of a deposited film and a method for manufacturing a semiconductor device

Abstract

This invention discloses a method for improving the uniformity of deposited thin films and a method for manufacturing a semiconductor device. The method for improving the uniformity of deposited thin films includes: Step 1: providing a reaction chamber, in which a wafer to be processed is placed; Step 2: heating the reaction chamber to an initial deposition temperature; Step 3: introducing a reactive gas into the reaction chamber to deposit a thin film on the surface of the wafer to be processed. The deposition process occurs during the period when the temperature of the reaction chamber decreases from the initial deposition temperature to the termination deposition temperature at a constant cooling rate. The deposition method provided by this invention utilizes the characteristic that the temperature of the wafer to be processed gradually decreases from the center to the edge of the wafer during cooling, so that the thickness of the deposited thin film gradually increases from the edge to the center of the wafer, thereby creating good complementarity of the deposited film thickness in all radial directions and greatly improving the thickness uniformity of the deposited thin film.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing, and in particular to a method for improving the uniformity of deposited thin films and a method for manufacturing semiconductor devices. Background Technology

[0002] In low-pressure deposition processes, high film thickness inevitably leads to poor uniformity. During film deposition, the precursor diffuses and is gradually consumed from the wafer edge to the center, causing the precursor concentration to gradually decrease from the edge to the center, forming a concentration gradient. This gradient directly results in a decrease in film thickness from the edge to the center, affecting the uniformity of the entire wafer. To meet high yield requirements, it is essential to ensure that the film thickness is as consistent as possible across the wafer, i.e., minimizing the thickness difference between the center and the edge.

[0003] Currently, in the furnace tube deposition thin film growth process, the external heating method and the high outer gas concentration are generally adopted. Combined with the constant temperature growth conditions, this results in the thickness of the deposited film at the periphery of the wafer being much greater than that at the center, and the overall uniformity is poor. The percentage deviation of the uniformity of the deposited film is about 9.6%.

[0004] Therefore, there is an urgent need for a method to improve the uniformity of deposited thin films, so that when the deposited thin film is used as a protective layer, insulating layer, or etching mask, it has higher reliability during etching and removal processes due to its better uniformity, and avoids the failure of other functional areas caused by deposited film residue in the later stages of the process. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention provides a method for improving the uniformity of deposited thin films and a method for manufacturing semiconductor devices.

[0006] One technical solution adopted by the present invention is: providing a method for improving the uniformity of deposited thin films, comprising:

[0007] Step 1: Provide a reaction chamber, in which a wafer to be processed is placed;

[0008] Step 2: Heat the reaction chamber to the initial deposition temperature;

[0009] Step 3: Introduce reactive gas into the reaction chamber to deposit a thin film on the surface of the wafer to be processed. The deposition process occurs during the period when the temperature of the reaction chamber decreases from the initial deposition temperature to the termination deposition temperature at a constant cooling rate.

[0010] Existing thin film deposition methods typically operate under isothermal conditions. Due to the distribution of reactive gas concentrations within the reaction chamber, the concentration in the edge region is generally higher than that in the central region. This means that under isothermal conditions, the film thickness at the edge region will be greater than that in the central region, resulting in uneven film thickness. This invention provides a deposition method that performs a constant-rate cooling process on the reaction chamber. The entire deposition process occurs during this constant-rate cooling process. Utilizing the characteristic that the temperature of the wafer to be processed gradually decreases from the wafer center to the wafer edge during cooling, the thickness of the deposited film gradually increases from the wafer edge to the wafer center. This results in good complementarity of the deposited film thickness in all radial directions, thereby significantly improving the uniformity of the deposited film thickness.

[0011] The start of the deposition process corresponds to the initial deposition temperature, and the end of the deposition process corresponds to the cessation deposition temperature.

[0012] The initial deposition temperature range in step two is 820±10℃.

[0013] The termination deposition temperature range is 805±10℃.

[0014] The constant cooling rate ranges from 1 degree Celsius per minute to 2 degrees Celsius per minute.

[0015] The thickness of the film deposited in step three is 210 nm.

[0016] The material of the thin film includes silicon nitride, and the wafer to be processed is a silicon wafer.

[0017] In step three, the reaction gases include dichlorosilane and ammonia.

[0018] The process also includes, in step two, introducing a protective gas into the reaction chamber. This protective gas is used to reduce the likelihood of oxidation of the wafer being processed during the heating process.

[0019] The present invention also provides a method for manufacturing a semiconductor device, comprising depositing a thin film on the surface of a wafer to be processed, wherein the thin film deposition process employs any one of the above-described technical solutions to improve the uniformity of the deposited thin film. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart of a method for improving the uniformity of deposited thin films provided by the present invention;

[0022] Figure 2 This is a schematic diagram of temperature changes during the deposition process of a method for improving the uniformity of deposited thin films provided in Example 1;

[0023] Figure 3 This is a schematic diagram of temperature changes during the deposition process of a thin film deposition method provided in Comparative Example 1;

[0024] Figure 4 This is a schematic diagram of temperature changes during the deposition process of a thin film deposition method provided in Comparative Example 2;

[0025] Figure label:

[0026] Load refers to the process of transferring the wafer to be processed from the transport system or loading box into the reaction chamber;

[0027] RU (heating / pressurization), in this invention, refers to the process of gradually increasing the temperature in the reaction chamber from an initial state to a set deposition condition;

[0028] STAB (Stable) means that after the set deposition conditions are reached, these conditions are maintained for a period of time to ensure that the entire system (including temperature, pressure, or gas flow rate) reaches a stable state.

[0029] DEPO (deposition) refers to the actual process of thin film deposition.

[0030] RD (cooling / depressurization), in this invention, refers to the process of gradually reducing the temperature in the reaction chamber from the deposition conditions to room temperature or atmospheric pressure after deposition is completed;

[0031] Unload refers to the process of removing the processed wafer from the reaction chamber and transferring it to the next process step or storage location. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the drawings. The embodiments of the present invention shown in and described with reference to the drawings are merely exemplary, and the present invention is not limited to these embodiments.

[0033] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0034] Example 1

[0035] Please see Figure 1 This embodiment provides a method for improving the uniformity of deposited thin films, including the following steps:

[0036] Step 1: Provide a reaction chamber, in which a wafer to be processed is placed.

[0037] Step 2: Heat the reaction chamber to the initial deposition temperature.

[0038] like Figure 2 As shown, specifically, the temperature of the reaction chamber is raised to 700 to 800 degrees Celsius as the initial deposition temperature for the thin film, and the system temperature is maintained at a stable state. This step also includes introducing a protective gas, namely nitrogen, into the reaction chamber to reduce the possibility of oxidation of the wafer to be processed during the heating process.

[0039] Step 3: Introduce reaction gas into the reaction chamber to perform thin film deposition on the surface of the wafer to be processed. During the deposition process, the temperature of the reaction chamber decreases from the initial deposition temperature to the termination deposition temperature at a constant cooling rate.

[0040] In this step, the temperature of the reaction chamber is constantly cooled, and a reactive gas is introduced into the chamber to deposit a thin film on the surface of the wafer to be processed. Specifically, the temperature of the reaction chamber is reduced from 820±10℃ at a constant rate of 1℃ to 2℃ per minute. Taking an initial deposition temperature of 820℃ as an example, the temperature of the reaction chamber is reduced to 805℃ at a constant rate of 1℃ / min. The reactive gas includes dichlorosilane and ammonia, and the deposited thin film material is silicon nitride, with a thickness of 210nm. During the thin film deposition process, the precursor gradually diffuses and is consumed from the wafer edge to the wafer center, resulting in a gradual decrease in the precursor concentration on the wafer surface from the wafer edge to the wafer center, ultimately leading to a gradual decrease in the thickness of the deposited thin film from the wafer edge to the wafer center. In the case of cooling deposition, the cooling device is generally located outside the reaction chamber. Therefore, the cooling process starts from the edge region of the wafer to be processed and gradually slows down from the edge to the center. Thus, during the cooling process, the temperature of the wafer to be processed gradually decreases from the center to the edge, causing the thickness of the deposited film to gradually increase from the edge to the center. Therefore, cooling deposition can make the thickness of the deposited film layer well complementary in each radial direction.

[0041] U% is used to evaluate the uniformity of thin film deposition. U% is a percentage deviation, representing the ratio of the difference between the maximum and minimum film thickness to the average thickness. A larger U% value indicates worse film deposition uniformity, and a smaller U% value indicates better film deposition uniformity. The method for improving the uniformity of deposited thin films provided in this embodiment yields a silicon nitride film with a uniformity percentage deviation of 2.5%. Stability tests and product verification of this technical solution yielded silicon nitride films with uniformity percentage deviations of 1.7%, 2.2%, 1.3%, and 1.9%, respectively. The silicon nitride film obtained under isothermal deposition conditions has a uniformity percentage deviation of approximately 9.6%, demonstrating that this technical solution significantly improves the film deposition uniformity compared to existing methods.

[0042] Comparative Example 1

[0043] This comparative example provides a thin film deposition method, which differs from the deposition method provided in Example 1 in that the thin film is deposited during a cooling-isothermal-cooling process, such as... Figure 3 As shown, the reaction chamber temperature is first raised from the initial temperature to the first deposition temperature, which is within the range of 820±10℃. After the system temperature reaches a stable state, dichlorosilane and ammonia are introduced into the reaction chamber to start the thin film deposition process. The reaction chamber is then cooled down, taking 820℃ as an example. The temperature of the reaction chamber is reduced from 820℃ to the second deposition temperature of 810℃ at a constant rate of 0.4℃ / min. The second deposition temperature is maintained for 5 minutes. The reaction chamber is then cooled down again, with the reaction temperature reduced from the second deposition temperature to the initial temperature at a constant rate of 0.4℃ / min. The thin film deposition process ends at this point. The percentage deviation of the thin film deposition uniformity obtained using this deposition method is 12.3%.

[0044] Comparative Example 2

[0045] This comparative example provides a thin film deposition method, which differs from the deposition method provided in the embodiments in that the thin film is deposited during a cooling-isothermal process, such as... Figure 4 As shown, the reaction chamber is first raised from the initial temperature to the first deposition temperature, which is within the range of 820±15℃. Reaction gases dichlorosilane and ammonia are then introduced into the reaction chamber, initiating the thin film deposition process. The reaction chamber is then cooled by decreasing the temperature from the first deposition temperature to the initial temperature at a constant rate of 0.2℃ / min to 0.4℃ / min, and maintaining the initial temperature for 5 minutes. Taking 820℃ as an example, the reaction chamber temperature is then decreased from 820℃ to the initial temperature at a constant cooling rate of 0.2℃ / min. The thin film is deposited during the aforementioned cooling and isothermal processes. The percentage deviation of the film deposition uniformity obtained using this deposition method is 9.6%.

[0046] Table 1 compares the percentage deviation values ​​of film uniformity obtained under existing isothermal deposition schemes, Example 1, Comparative Example 1, and Comparative Example 2. As shown in Table 1, the deposition film obtained by the deposition method provided by Comparative Example 1 has a poor improvement effect on uniformity compared to existing isothermal deposition schemes. The deposition film obtained by the deposition method provided by Comparative Example 2 has no significant change in uniformity compared to existing isothermal deposition schemes. The percentage deviation value of film uniformity obtained by the deposition method provided in Example 1 is much lower than that of existing isothermal deposition schemes and Comparative Examples 1 and 2, and the effect of improving the uniformity of the deposition film is significant.

[0047] Table 1

[0048]

[0049] The present invention also provides a method for manufacturing a semiconductor device, including the method for improving the uniformity of the deposited thin film as described in any of the above technical solutions.

[0050] Furthermore, it should be noted that in this specification, "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0051] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method of improving the uniformity of a deposited film, characterized by, include: Step 1: Provide a reaction chamber, in which a wafer to be processed is placed; Step 2: Heat the reaction chamber to the initial deposition temperature; Step 3: Introduce reactive gas into the reaction chamber to deposit a thin film on the surface of the wafer to be processed. The deposition process occurs during the period when the temperature of the reaction chamber decreases from the initial deposition temperature to the termination deposition temperature at a constant cooling rate.

2. The method of claim 1 wherein: The start of the deposition process corresponds to the initial deposition temperature, and the end of the deposition process corresponds to the cessation deposition temperature.

3. The method of claim 1 wherein: The initial deposition temperature range in step two is 820±10℃.

4. The method of claim 1 wherein: The termination deposition temperature range is 805±10℃.

5. The method of claim 1 wherein: The constant cooling rate ranges from 1 degree Celsius per minute to 2 degrees Celsius per minute.

6. The method of claim 1 wherein: The thickness of the film deposited in step three is 210 nm.

7. The method of claim 1 wherein: The material of the thin film includes silicon nitride, and the wafer to be processed is a silicon wafer.

8. The method of claim 1 wherein: In step three, the reaction gases include dichlorosilane and ammonia.

9. The method of claim 1 wherein: It also includes introducing a protective gas into the reaction chamber in step two.

10. A method of manufacturing a semiconductor device, characterized by The method includes performing thin film deposition on the surface of the wafer to be processed, wherein the thin film deposition process employs the method for improving the uniformity of the deposited thin film as described in any one of claims 1 to 9 to improve the uniformity of the deposited thin film.

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