Method for forming process chamber coating of silicon nitride processing machine

Abstract

This invention discloses a method for forming a process cavity coating on a silicon nitride process equipment, comprising: Step 1, forming a silicon oxide undercoat and adjusting a first deposition rate of the silicon oxide undercoat to adjust a first adhesion so that a first upper limit value of the cumulative thickness of the process cavity coating meets requirements. Step 2, forming a silicon nitride precoat, comprising: Step 21, forming a first silicon nitride precoat to achieve rapid warm-up. Step 22, forming a second silicon nitride precoat and setting process parameters according to the density requirements of the second silicon nitride precoat, with a process window for the cumulative thickness of the coating and ensuring that the first upper limit value is within the process window for the cumulative thickness of the coating. This invention can extend the time interval between two process cavity cleanings, thereby improving equipment efficiency.

Description

Technical Field

[0001] This invention relates to a semiconductor integrated circuit manufacturing method, and more particularly to a method for forming a process cavity coating on a silicon nitride process equipment. Background Technology

[0002] Silicon nitride (SiN) thin film deposition is widely used in the top metal and passivation layer of chip manufacturing processes. High-stress SiN thin films are used to correct the overall warpage of the wafer and improve hillock defects.

[0003] High-stress SiN process tools typically employ PECVD equipment and use a cumulative film thickness cleaning method. That is, when the film thickness on the inner surface of the process chamber of the PECVD machine reaches a certain thickness, cleaning is required to remove the accumulated film on the inner surface of the process chamber.

[0004] High cumulative film thickness reduces the adhesion of the coating film between high-stress SiN and the showerhead, making it prone to peeling defects.

[0005] like Figure 1A The image shown is a scan of the peeling defect that occurs when the cumulative coating thickness of the process cavity coating of the existing silicon nitride process equipment is greater than 8.5 micrometers. It can be seen that there are many defects 102, i.e. peeling defects, on the scan image 101 corresponding to the wafer.

[0006] like Figure 1B As shown, is Figure 1A SEM images of peeling defects in the middle. Figure 1B The image shows photos of multiple defects 102a.

[0007] In the current process, the current upper limit for cumulative film thickness is set at 8.5 micrometers, and the cumulative film thickness that can be processed is only 2.3 micrometers. That is, when the cumulative coating thickness on the inner surface of the process chamber is 2.3 micrometers, cleaning is required. This increases the number of cleaning operations, and excessive cleaning operations lead to low machine efficiency, approximately 60%. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for forming a coating in the process cavity of a silicon nitride process equipment, which can extend the time interval between two process cavity cleanings, thereby improving the efficiency of the equipment.

[0009] To solve the above-mentioned technical problems, the method for forming a process cavity coating of a silicon nitride process equipment provided by the present invention includes the following steps:

[0010] Step 1: Forming the silicon oxide undercoating (UCT). During the formation of the silicon oxide undercoating (UCT), the first deposition rate of the silicon oxide undercoating is adjusted to adjust the first adhesion between the silicon oxide undercoating and the inner surface of the process cavity. The lower the first deposition rate, the higher the first adhesion. The higher the first adhesion, the larger the first upper limit of the cumulative coating thickness of the process cavity coating. The first deposition rate is set according to the requirement of the first upper limit, thereby setting the process parameters for forming the silicon oxide undercoating.

[0011] When the cumulative thickness of the coating is less than or equal to the first upper limit value, the particulate contamination in the process cavity during the silicon nitride process meets the requirements.

[0012] Step 2: Forming a silicon nitride pre-coating (PCT), which includes the following sub-steps:

[0013] Step 21: Form a first silicon nitride pre-coating. The formation process of the first silicon nitride pre-coating is used to achieve rapid warm-up of the process cavity. The process parameters for forming the first silicon nitride pre-coating are set according to the first time required for rapid warm-up. The first time must ensure that the first wafer effect can be eliminated.

[0014] Step 22: Form a second silicon nitride pre-coating. The second silicon nitride pre-coating and the first silicon nitride pre-coating are superimposed to form the silicon nitride pre-coating. The silicon nitride pre-coating and the silicon oxide undercoating are superimposed to form a single-process cavity coating.

[0015] The process parameters for forming the second silicon nitride pre-coating are set according to the density requirements of the second silicon nitride pre-coating. The higher the density of the second silicon nitride pre-coating, the larger the process window for the cumulative thickness of the coating that generates particulate contamination. The density requirements of the second silicon nitride pre-coating ensure that the first upper limit value is within the process window for the cumulative thickness of the coating.

[0016] A further improvement is that, in step one, the process parameters for forming the silicon oxide undercoat include: HF radio frequency power, deposition time, cavity pressure, and process gas, wherein the process gas includes silicon source gas, nitrogen, and oxygen source gas.

[0017] The first deposition rate is reduced by decreasing the radio frequency power, cavity pressure, and process gas flow rate in the process parameters of the silicon oxide undercoating.

[0018] A further improvement is that the silicon source gas includes silane, and the oxygen source gas includes nitrous oxide.

[0019] A further improvement is that, in step 21, the process parameters for forming the first silicon nitride pre-coating include: HF radio frequency power, LF radio frequency power, deposition time, cavity pressure, and process gas, wherein the process gas includes silicon source gas, nitrogen, and nitrogen source gas.

[0020] The first time is reduced by increasing the flow rate of the process gas, the HF RF power, and the LF RF power in the process parameters of the first silicon nitride pre-coating.

[0021] A further improvement is that the silicon source gas includes silane, and the nitrogen source gas includes ammonia.

[0022] A further improvement is that, in step 22, the process parameters for forming the second silicon nitride pre-coating include: HF radio frequency power, LF radio frequency power, deposition time, cavity pressure, and process gas, wherein the process gas includes silicon source gas, nitrogen, and nitrogen source gas.

[0023] The density of the second silicon nitride pre-coating is increased by increasing the cavity pressure in the process parameters of the second silicon nitride pre-coating.

[0024] A further improvement is that the silicon source gas includes silane, and the nitrogen source gas includes ammonia.

[0025] A further improvement is that, in step one, the process parameters for forming the silicon oxide undercoat are set as follows:

[0026] The HF radio frequency power is 530W;

[0027] The deposition time was 120 seconds.

[0028] The cavity pressure is 1.3 torr;

[0029] The silane flow rate is 80 sccm;

[0030] The nitrogen flow rate is 4000 sccm;

[0031] The nitrous oxide flow rate was 9600 sccm.

[0032] A further improvement is that, in step 21, the process parameters for forming the first silicon nitride pre-coating are set as follows:

[0033] The HF radio frequency power is 2425W;

[0034] The LF radio frequency power is 785W;

[0035] The deposition time was 180 seconds.

[0036] The cavity pressure is 3.36 torr;

[0037] The silane flow rate is 1300 sccm;

[0038] The nitrogen flow rate is 18500 sccm;

[0039] The ammonia flow rate is 3500 sccm.

[0040] A further improvement is that, in step 22, the process parameters for forming the second silicon nitride pre-coating are set as follows:

[0041] The HF radio frequency power is 1530W;

[0042] The LF radio frequency power is 125W;

[0043] The deposition time was 600 s;

[0044] The cavity pressure is 2.4 torr;

[0045] The silane flow rate is 250 sccm;

[0046] The nitrogen flow rate is 23000 sccm;

[0047] The ammonia flow rate is 1300 sccm.

[0048] A further improvement is that the first upper limit is above 9 micrometers.

[0049] A further improvement is that the process chamber is used for product running before the cumulative coating thickness reaches the second control value.

[0050] As the quantity of goods processed increases, when the cumulative thickness of the coating reaches the second control value, the process cavity is cleaned to remove the coating.

[0051] The second control value is less than the first upper limit value.

[0052] A further improvement is that the maximum value of the second control value is above 6 micrometers.

[0053] A further improvement is that the silicon nitride process equipment is a stress silicon nitride process equipment.

[0054] This invention features a special design for the formation process of the process cavity coating. Before the silicon nitride pre-coating is formed, a silicon oxide undercoating is formed. Taking advantage of the superior adhesion of silicon oxide compared to silicon nitride, especially stress silicon nitride, the silicon oxide undercoating is used as the adhesion layer for the silicon nitride pre-coating. The first adhesion is adjusted by regulating the first deposition rate of the silicon oxide undercoating, thereby improving the adhesion of the entire single-pass process cavity coating and further improving the adhesion of the process cavity coating formed by the accumulation of multiple single-pass process cavity coatings. Since this invention pre-sets the first adhesion based on the first upper limit value of the cumulative coating thickness of the process cavity coating, it can maintain or increase the cumulative coating thickness of the process cavity coating, thus extending the time interval between two process cavity cleanings and improving machine efficiency.

[0055] Typically, due to increased initial adhesion, the silicon oxide undercoat formation process can adversely affect the standard deviation (STD) of the thickness of the silicon nitride film formed within the process chamber, such as the silicon nitride film formed on the product wafer. To overcome this adverse effect, the present invention makes corresponding improvements to the silicon nitride precoat formation process, including:

[0056] The silicon nitride pre-coating process is divided into two stages. The first silicon nitride pre-coating process is used to achieve rapid seasoning and warm-up of the process chamber, thereby effectively eliminating the first-wafer effect. For example, the process parameters such as thickness of the silicon nitride grown on the first wafer, such as stress silicon nitride, meet the requirements. Seasoning refers to adjusting the environment of the process chamber to conditions suitable for thin film growth of the product.

[0057] The introduction of the first silicon nitride pre-coating increases the risk of coating peeling off in the process chamber, thus reducing the first upper limit value. To address this, the present invention further refines the formation process of the second silicon nitride pre-coating to increase its density, thereby reducing the risk of coating peeling off and causing particulate contamination in the process chamber and increasing the process window for coating accumulation thickness while ensuring that the first upper limit value is within the process window for coating accumulation thickness. In this way, the technical problems caused by the introduction of the first silicon nitride pre-coating are eliminated.

[0058] By superimposing the first silicon nitride pre-coating layer and the second silicon nitride pre-coating layer, the resulting silicon nitride pre-coating layer, after covering the silicon oxide undercoating layer, can ensure that the standard deviation of the thickness of the silicon nitride film formed in the process cavity meets the requirements.

[0059] Therefore, the present invention can extend the time interval between two process chamber cleanings, thereby improving machine efficiency. At the same time, the present invention can also eliminate the first-wafer effect and ensure that the standard deviation of the thickness of the silicon nitride film formed in the process chamber after the process chamber coating is formed meets the requirements. Attached Figure Description

[0060] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0061] Figure 1A This is a scan image of a peeling defect that occurs when the cumulative coating thickness of the process cavity coating of an existing silicon nitride process machine is greater than 8.5 micrometers.

[0062] Figure 1B yes Figure 1A SEM images of the peeling defect;

[0063] Figure 2 This is a flowchart of a method for forming a coating in the process cavity of a silicon nitride process equipment according to an embodiment of the present invention;

[0064] Figure 3 This is a comparative diagram showing the process flow of various variations in the formation method of the process cavity coating of the existing silicon nitride process equipment to the formation method of the process cavity coating of the silicon nitride process equipment in the embodiments of the present invention.

[0065] Figure 4A This is a comparative table showing the process parameters of the silicon oxide undercoat in the process cavity coating formation method of the silicon nitride process equipment in the embodiment of the present invention.

[0066] Figure 4B This is a comparative table showing the process parameters of the silicon nitride pre-coating in the process cavity coating formation method of the silicon nitride process equipment in the embodiments of the present invention. Detailed Implementation

[0067] like Figure 2 The diagram shows a flowchart of a method for forming a process cavity coating on a silicon nitride process equipment according to an embodiment of the present invention. The method for forming a process cavity coating on a silicon nitride process equipment according to an embodiment of the present invention includes the following steps:

[0068] Step 1: Forming a silicon oxide undercoat. During the formation of the silicon oxide undercoat, the first deposition rate of the silicon oxide undercoat is adjusted to adjust the first adhesion between the silicon oxide undercoat and the inner surface of the process cavity. The lower the first deposition rate, the higher the first adhesion. The higher the first adhesion, the larger the first upper limit of the cumulative coating thickness of the process cavity coating. The first deposition rate is set according to the requirement of the first upper limit, thereby setting the process parameters for forming the silicon oxide undercoat.

[0069] When the cumulative thickness of the coating is less than or equal to the first upper limit value, the particulate contamination in the process cavity during the silicon nitride process meets the requirements.

[0070] In this embodiment of the invention, the process parameters for forming the silicon oxide undercoat include: HF radio frequency power, deposition time, cavity pressure, and process gas, wherein the process gas includes silicon source gas, nitrogen gas, and oxygen source gas.

[0071] The first deposition rate is reduced by decreasing the radio frequency power, cavity pressure, and process gas flow rate in the process parameters of the silicon oxide undercoating.

[0072] The silicon source gas includes silane, and the oxygen source gas includes nitrous oxide.

[0073] Step 2: Forming a silicon nitride pre-coating, including the following sub-steps:

[0074] Step 21: Form a first silicon nitride pre-coating. The formation process of the first silicon nitride pre-coating is used to achieve rapid warm-up of the process cavity. The process parameters for forming the first silicon nitride pre-coating are set according to the first time required for rapid warm-up. The first time must be sufficient to eliminate the first-wafer effect.

[0075] In this embodiment of the invention, the process parameters for forming the first silicon nitride pre-coating include: HF radio frequency power, LF radio frequency power, deposition time, cavity pressure, and process gas, wherein the process gas includes silicon source gas, nitrogen, and nitrogen source gas.

[0076] The first time is reduced by increasing the flow rate of the process gas, the HF RF power, and the LF RF power in the process parameters of the first silicon nitride pre-coating.

[0077] The silicon source gas includes silane, and the nitrogen source gas includes ammonia.

[0078] Step 22: Form a second silicon nitride pre-coating. The second silicon nitride pre-coating and the first silicon nitride pre-coating are superimposed to form the silicon nitride pre-coating. The silicon nitride pre-coating and the silicon oxide undercoating are superimposed to form a single-process cavity coating.

[0079] The process parameters for forming the second silicon nitride pre-coating are set according to the density requirements of the second silicon nitride pre-coating. The higher the density of the second silicon nitride pre-coating, the larger the process window for the cumulative thickness of the coating that generates particulate contamination. The density requirements of the second silicon nitride pre-coating ensure that the first upper limit value is within the process window for the cumulative thickness of the coating.

[0080] In this embodiment of the invention, the process parameters for forming the second silicon nitride pre-coating include: HF radio frequency power, LF radio frequency power, deposition time, cavity pressure, and process gas, wherein the process gas includes silicon source gas, nitrogen, and nitrogen source gas.

[0081] The density of the second silicon nitride pre-coating is increased by increasing the cavity pressure in the process parameters of the second silicon nitride pre-coating.

[0082] The silicon source gas includes silane, and the nitrogen source gas includes ammonia.

[0083] Before the cumulative thickness of the coating reaches the second control value, the process chamber is used for product processing.

[0084] As the quantity of goods processed increases, when the cumulative thickness of the coating reaches the second control value, the process cavity is cleaned to remove the coating.

[0085] The second control value is less than the first upper limit value.

[0086] In this embodiment of the invention, the silicon nitride process equipment is a stress silicon nitride process equipment, specifically a high-stress silicon nitride process equipment. This is because as the stress of silicon nitride increases, the stress of the corresponding silicon nitride coating also increases, which shortens the first upper limit value and reduces the cleaning cycle. This embodiment of the invention solves the technical problem of short cleaning cycles and the resulting reduction in production efficiency in high-stress silicon nitride process equipment.

[0087] In some embodiments, in step one, the process parameters for forming the silicon oxide undercoat are set as follows:

[0088] The HF radio frequency power is 530W;

[0089] The deposition time was 120 seconds.

[0090] The chamber pressure is 1.3 torr;

[0091] The silane flow rate (SiH4flow) is 80 sccm;

[0092] The nitrogen flow rate (N2flow) is 4000 sccm;

[0093] The nitrous oxide flow rate (N2O flow) is 9600 sccm.

[0094] In step 21, the process parameters for forming the first silicon nitride pre-coating are set as follows:

[0095] The HF radio frequency power is 2425W;

[0096] The LF radio frequency power is 785W;

[0097] The deposition time was 180 seconds.

[0098] The cavity pressure is 3.36 torr;

[0099] The silane flow rate is 1300 sccm;

[0100] The nitrogen flow rate is 18500 sccm;

[0101] The ammonia flow rate (NH3flow) is 3500 sccm.

[0102] In step 22, the process parameters for forming the second silicon nitride pre-coating are set as follows:

[0103] The HF radio frequency power is 1530W;

[0104] The LF radio frequency power is 125W;

[0105] The deposition time was 600 s;

[0106] The cavity pressure is 2.4 torr;

[0107] The silane flow rate is 250 sccm;

[0108] The nitrogen flow rate is 23000 sccm;

[0109] The ammonia flow rate is 1300 sccm.

[0110] In some embodiments, the first upper limit is 9 micrometers or more.

[0111] The maximum value of the second control value is 6 micrometers or more.

[0112] This invention provides a special configuration for the formation process of the process cavity coating. Before the silicon nitride pre-coating is formed, a silicon oxide undercoating is formed. Taking advantage of the superior adhesion of silicon oxide compared to silicon nitride, especially stress silicon nitride, the silicon oxide undercoating is used as the adhesion layer for the silicon nitride pre-coating. The first adhesion is adjusted by regulating the first deposition rate of the silicon oxide undercoating, thereby improving the adhesion of the entire single-pass process cavity coating and further improving the adhesion of the process cavity coating formed by the accumulation of multiple single-pass process cavity coatings. Since this invention sets the first adhesion based on the first upper limit of the cumulative coating thickness of the process cavity coating, this invention can maintain or increase the cumulative coating thickness of the process cavity coating, thus extending the time interval between two process cavity cleanings and improving machine efficiency.

[0113] Typically, due to the increased adhesion of the first coating layer, the silicon oxide undercoat formation process can adversely affect the standard deviation (STD) of the thickness of the silicon nitride film formed within the process chamber, such as the silicon nitride film formed on the product wafer. To overcome this adverse effect, the embodiments of the present invention have made corresponding improvements to the silicon nitride precoat formation process, including:

[0114] The silicon nitride pre-coating formation process is divided into two stages. The first silicon nitride pre-coating formation process is used to achieve rapid season warm-up of the process cavity, thereby effectively eliminating the first wafer effect. For example, the process parameters such as thickness of the silicon nitride grown on the first wafer, such as stress silicon nitride, meet the requirements.

[0115] The introduction of the first silicon nitride pre-coating increases the risk of coating peeling off in the process chamber, thus reducing the first upper limit value. To address this, the present invention further refines the formation process of the second silicon nitride pre-coating to increase its density, thereby reducing the risk of coating peeling off and causing particulate contamination in the process chamber and increasing the process window for coating accumulation thickness while ensuring that the first upper limit value is within the process window for coating accumulation thickness. This eliminates the technical problems caused by the introduction of the first silicon nitride pre-coating.

[0116] By superimposing the first silicon nitride pre-coating layer and the second silicon nitride pre-coating layer, the resulting silicon nitride pre-coating layer, after covering the silicon oxide undercoating layer, can ensure that the standard deviation of the thickness of the silicon nitride film formed in the process cavity meets the requirements.

[0117] Therefore, the embodiments of the present invention can extend the time interval between two process chamber cleanings, thereby improving machine efficiency. At the same time, the embodiments of the present invention can also eliminate the first wafer effect and ensure that the standard deviation of the thickness of the silicon nitride film formed in the process chamber where the process chamber coating is formed meets the requirements.

[0118] In this embodiment of the invention, the efficiency of the high-stress silicon nitride (UCT) process equipment is improved. By optimizing the UCT process, the adhesion of the UCT film is improved, thereby increasing the peeling defect window.

[0119] By adjusting the PCT structure and introducing the new PCT1 process, the cavity was fully seasoned, solving the STD worsening problem. By optimizing the PCT2 process, the compactness of the PCT film was improved, thus improving the particle defect (PA) performance at high cumulative film thickness.

[0120] The cumulative film thickness that can be processed within a single clean cycle increases significantly, thereby improving machine efficiency.

[0121] In one specific embodiment of the method of the present invention, the cumulative film thickness that can be processed in one clean cycle of the high-stress SIN process can be increased from 2.3 micrometers to 6 micrometers, the machine processing efficiency can be increased from 60% to 80%, the overall wafer per hour (WPH) can be increased by 25%, and the SIN film thickness standard deviation (STD) can be maintained at the original baseline level.

[0122] The differences between the embodiments of the present invention and existing methods will be further explained below with reference to the accompanying drawings:

[0123] like Figure 3 The diagram shown is a comparison of the formation process of various variations in the existing silicon nitride process equipment's process cavity coating formation method to the silicon nitride process equipment's process cavity coating formation method of the present invention.

[0124] The SIN process coating film includes UCT and PCT; UCT is an oxide film with good adhesion; PCT is a SIN film, which plays a role in fully seasoning and warming up the machine and regulating the cavity atmosphere, thus eliminating the first wafer effect.

[0125] The following is based on Figure 3 The following comparison is provided:

[0126] Figure 3 Box 201 shows flowcharts corresponding to four methods, where dashed box 202 represents a flowchart of the process cavity coating formation method of existing silicon nitride process equipment. The existing method consists of the UCT formation step corresponding to mark 301 and the PCT formation step corresponding to mark 302. The following comparisons are all based on the existing method as a baseline.

[0127] In high-stress silicon nitride processes, the existing method (dashed box 202) requires cleaning when the cumulative film thickness in the process cavity reaches 2.3 micrometers, which has the disadvantage of low efficiency.

[0128] The method corresponding to dashed box 203, namely CIP1, is an improved version of the existing method. The modification is to replace the UCT step with low deposition rate (LDR) UCT corresponding to mark 301a. LDR UCT increases the adhesion of the coating, making it less likely to fall off as the coating thickness increases. Therefore, it is less likely to produce peeling defects, and particle detection is normal (OK) when the cumulative film thickness reaches 9 micrometers. However, the initial film thickness STD is worse.

[0129] The method corresponding to dashed box 204, namely CIP2, is an improvement on CIP1. It changes the PCT from one layer to two layers: PCT1 (marked 3021) and PCT2 (marked 302). PCT1 has higher gas flow and RF power, allowing for sufficient warm-up in a shorter time and effectively eliminating the first wafer effect. PCT2 is identical to the original PCT, hence it is also marked 302. CIP2 exhibits particle worsening at a cumulative film thickness of 6.3 micrometers, requiring an upper limit of 6 micrometers for cumulative film thickness, which still results in relatively low efficiency.

[0130] The method corresponding to dashed box 204, namely CIP3, is the method of this embodiment of the invention. It is an improvement on CIP2, specifically by increasing the process pressure (cavity pressure) of the PCT2 process (marked 3022) to improve the coating film density and increase the particle process window. CIP3 achieves both the STD of film thickness and particle performance as per the original baseline, meeting the process requirements.

[0131] Ultimately, under CIP3 conditions, the cumulative film thickness that can be processed within one clean cycle increased from 2.3 micrometers to 6 micrometers, the machine processing efficiency increased from 60% to 80%, and the overall WPH increased by 25%.

[0132] like Figure 4A The table shown is a comparison table of process parameters for the silicon oxide undercoat in the process cavity coating formation method of the existing silicon nitride process equipment to that in the silicon nitride process equipment formation method of the present invention.

[0133] Figure 4A The dashed box 301 corresponds to Figure 3 The process parameters in the UCT step corresponding to mark 301; the dashed box 301a corresponds to... Figure 3 The process parameters in the LDR UCT step corresponding to mark 301a. Please read the details directly. Figure 4A The contents recorded in it.

[0134] like Figure 4B The table shown is a comparison table of process parameters for the silicon nitride pre-coating in the process cavity coating formation method of the existing silicon nitride process equipment to the process cavity coating formation method of the silicon nitride process equipment in the embodiments of the present invention. Figure 4A The dashed box 302 corresponds to Figure 3 The process parameters in the PCT step corresponding to mark 302 in the middle; the dashed box 3021 corresponds to... Figure 3The process parameters in step PCT1 corresponding to mark 3021; ​​the dashed box 3022 corresponds to... Figure 3 The process parameters in step PCT2 corresponding to mark 3022. Please read the details directly. Figure 4B The contents recorded in it.

[0135] The present invention has been described in detail above through specific embodiments, but these are not intended to limit the invention. Many modifications and improvements can be made by those skilled in the art without departing from the principles of the invention, and these should also be considered within the scope of protection of the present invention.

Claims

1. A method for forming a process cavity coating on a silicon nitride manufacturing machine, characterized in that, Includes the following steps: Step 1: Forming a silicon oxide undercoat. During the formation of the silicon oxide undercoat, the first deposition rate of the silicon oxide undercoat is adjusted to adjust the first adhesion between the silicon oxide undercoat and the inner surface of the process cavity. The lower the first deposition rate, the higher the first adhesion. The higher the first adhesion, the greater the first upper limit of the cumulative coating thickness of the process chamber coating. The first deposition rate is set according to the requirement of the first upper limit, and thus the process parameters for forming the silicon oxide undercoat are set. When the cumulative thickness of the coating is less than or equal to the first upper limit value, the particulate contamination of the process cavity in the silicon nitride process meets the requirements. Step 2: Forming a silicon nitride pre-coating, including the following sub-steps: Step 21: Form a first silicon nitride pre-coating. The formation process of the first silicon nitride pre-coating is used to achieve rapid warm-up of the process cavity. The process parameters for forming the first silicon nitride pre-coating are set according to the first time required for rapid warm-up. The first time must be sufficient to eliminate the first-wafer effect. Step 22: Form a second silicon nitride pre-coating. The second silicon nitride pre-coating and the first silicon nitride pre-coating are superimposed to form the silicon nitride pre-coating. The silicon nitride pre-coating and the silicon oxide undercoating are superimposed to form a single-process cavity coating. The process parameters for forming the second silicon nitride pre-coating are set according to the density requirements of the second silicon nitride pre-coating. The higher the density of the second silicon nitride pre-coating, the larger the process window for the cumulative thickness of the coating that generates particulate contamination. The density requirements of the second silicon nitride pre-coating ensure that the first upper limit value is within the process window for the cumulative thickness of the coating.

2. The method for forming the process cavity coating of the silicon nitride process equipment as described in claim 1, characterized in that: In step one, the process parameters for forming the silicon oxide undercoat include: HF radio frequency power, deposition time, cavity pressure, and process gas, wherein the process gas includes silicon source gas, nitrogen, and oxygen source gas; The first deposition rate is reduced by decreasing the radio frequency power, cavity pressure, and process gas flow rate in the process parameters of the silicon oxide undercoating.

3. The method for forming the process cavity coating of the silicon nitride process equipment as described in claim 2, characterized in that: The silicon source gas includes silane, and the oxygen source gas includes nitrous oxide.

4. The method for forming the process cavity coating of the silicon nitride process equipment as described in claim 1, characterized in that: In step 21, the process parameters for forming the first silicon nitride pre-coating include: HF radio frequency power, LF radio frequency power, deposition time, cavity pressure, and process gas, wherein the process gas includes silicon source gas, nitrogen, and nitrogen source gas; The first time is reduced by increasing the flow rate of the process gas, the HF RF power, and the LF RF power in the process parameters of the first silicon nitride pre-coating.

5. The method for forming the process cavity coating of the silicon nitride process equipment as described in claim 4, characterized in that: The silicon source gas includes silane, and the nitrogen source gas includes ammonia.

6. The method for forming the process cavity coating of the silicon nitride process equipment as described in claim 1, characterized in that: In step 22, the process parameters for forming the second silicon nitride pre-coating include: HF radio frequency power, LF radio frequency power, deposition time, cavity pressure, and process gas, wherein the process gas includes silicon source gas, nitrogen, and nitrogen source gas; The density of the second silicon nitride pre-coating is increased by increasing the cavity pressure in the process parameters of the second silicon nitride pre-coating.

7. The method for forming the process cavity coating of the silicon nitride process equipment as described in claim 6, characterized in that: The silicon source gas includes silane, and the nitrogen source gas includes ammonia.

8. The method for forming the process cavity coating of the silicon nitride process equipment as described in claim 3, characterized in that, In step one, the process parameters for forming the silicon oxide undercoat are set as follows: The HF radio frequency power is 530W; The deposition time was 120 seconds. The cavity pressure is 1.3 torr; The silane flow rate is 80 sccm; The nitrogen flow rate is 4000 sccm; The nitrous oxide flow rate was 9600 sccm.

9. The method for forming the process cavity coating of the silicon nitride process equipment as described in claim 5, characterized in that, In step 21, the process parameters for forming the first silicon nitride pre-coating are set as follows: The HF radio frequency power is 2425W; The LF radio frequency power is 785W; The deposition time was 180 seconds. The cavity pressure is 3.36 torr; The silane flow rate is 1300 sccm; The nitrogen flow rate is 18500 sccm; The ammonia flow rate is 3500 sccm.

10. The method for forming the process cavity coating of the silicon nitride process equipment as described in claim 7, characterized in that, In step 22, the process parameters for forming the second silicon nitride pre-coating are set as follows: The HF radio frequency power is 1530W; The LF radio frequency power is 125W; The deposition time was 600 s; The cavity pressure is 2.4 torr; The silane flow rate is 250 sccm; The nitrogen flow rate is 23000 sccm; The ammonia flow rate is 1300 sccm.

11. The method for forming the process cavity coating of the silicon nitride process equipment as described in claim 1, characterized in that: The first upper limit is 9 micrometers.

12. The method for forming the process cavity coating of the silicon nitride process equipment as described in claim 11, characterized in that: Before the cumulative thickness of the coating reaches the second control value, the process chamber is used for product processing. As the quantity of goods processed increases, when the cumulative thickness of the coating reaches the second control value, the process cavity is cleaned to remove the coating from the process cavity. The second control value is less than the first upper limit value.

13. The method for forming the process cavity coating of the silicon nitride process equipment as described in claim 12, characterized in that: The maximum value of the second control value is 6 micrometers.

14. The method for forming the process cavity coating of the silicon nitride process equipment as described in claim 1, characterized in that: The silicon nitride process machine is a stress silicon nitride process machine.

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