Wet cleaning process and testing method thereof
By splitting the acid solution cleaning process and combining it with SC1 and SC2 cleaning processes, the problems of etching thickness and watermark defects in wet cleaning were solved, achieving stable etching and improving wafer surface quality.
Patent Information
- Application Number
- CN202411196220.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-28
- Publication Date
- 2026-03-13
AI Technical Summary
Existing wet cleaning processes cannot simultaneously address etching thickness and improve watermark defects on wafer surfaces, and the use of hydrofluoric acid treatment can affect device structure and performance.
The acid solution cleaning process is divided into two or more steps. The hydrofluoric acid solution has a mass fraction of 0.4% or greater. The hydrophilicity of the wafer surface is optimized by SC1 and SC2 cleaning processes, and the preset thickness is removed by etching step by step.
It effectively controls the amount of etching, avoids excessive etching, and significantly improves watermark defects, thereby enhancing the cleaning effect.
Smart Images
Figure CN121665931A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a wet cleaning process and its testing method. Background Technology
[0002] In the integrated circuit fabrication process, almost every step involves a cleaning process. Wet cleaning is the mainstream cleaning process currently in use, which involves spraying or immersing the wafer with chemical reagents to remove impurities adhering to the wafer surface. However, wet cleaning processes are prone to causing watermark defects on the wafer surface. For example... Figure 1 and Figure 2 As shown, the formation of watermark P is mainly due to incomplete drying of the wafer W surface, causing residual water on the silicon surface to react with oxygen to form SiO2. SiO2 then further reacts with water to form H2SiO3 or HSiO3. - The precipitate, and / or SiO2 also reacts with HF to form H2SiF6 precipitate, which ultimately adheres to the surface of wafer W, forming watermarks P. The specific reaction formula is as follows:
[0003] Si + O₂ = SiO₂
[0004] SiO2 + H2O = H2SiO3
[0005] H2SiO3=H + +HSiO3 -
[0006] SiO2 + 6HF = H2SiF6 + 2H2O
[0007] In short, watermarks (P) are formed by the oxidation of silicon in water and the subsequent decomposition of the resulting oxides. The water-repellent surface of the wafer (W) and hydrofluoric acid accelerate the formation of watermark P defects. Watermark P defects not only affect the inspection and evaluation of other defects on the wafer (W), but also hinder the formation of silicides, impacting device yield. Current processes generally employ hot phosphoric acid retreatment of the wafer (W) surface to reduce watermark P defects; alternatively, increasing the circulation flow rate of deionized water in the overflow tank enhances the cleaning ability of deionized water, thereby reducing the probability of watermark P defects; or, adding surfactants to hydrofluoric acid and deionized water reduces the water repellency of the wafer (W) surface, thus mitigating the watermark P defect problem.
[0008] However, increasing the SC1 cleaning time and using standard RCAM cleaning reprocessing in the above methods still cannot significantly improve the watermark P defects on the wafer W surface. Furthermore, the hydrofluoric acid reprocessing method alters the etching thickness at the current site, affecting the device structure and its performance.
[0009] Therefore, a new wet cleaning process is urgently needed to alleviate the above-mentioned technical problems. Summary of the Invention
[0010] The purpose of this invention is to provide a wet cleaning process and its testing method to solve the problem of how to balance the etching thickness of wet cleaning with the improvement of watermark defects on the wafer surface.
[0011] To solve the above technical problems, the present invention provides a wet cleaning process, comprising:
[0012] Provide one wafer;
[0013] Perform SC1 cleaning process and / or SC2 cleaning process on the wafer;
[0014] The wafer is subjected to at least two acid solution cleaning processes to remove the wafer of a predetermined thickness.
[0015] Optionally, in the wet cleaning process, during the process of performing at least two acid solution cleaning processes on the wafer to remove the wafer of a predetermined thickness, the wafer is subjected to two acid solution cleaning processes; wherein,
[0016] The first acid solution cleaning process removes the wafer of a first thickness, and the second acid solution cleaning process removes the wafer of a second thickness; wherein the second thickness accounts for more than or equal to 30% of the first thickness.
[0017] Optionally, in the wet cleaning process, the acid solution used in the acid solution cleaning process includes hydrofluoric acid solution, and the mass fraction of the hydrofluoric acid solution is greater than or equal to 0.4%.
[0018] Optionally, in the wet cleaning process, the process time for performing the at least two acid solution cleaning processes on the wafer is greater than or equal to 4 minutes.
[0019] Based on the same inventive concept, the present invention also provides a testing method for a wet cleaning process, comprising:
[0020] Provide multiple first test pieces;
[0021] Perform SC1 cleaning process and / or SC2 cleaning process on each of the first test pieces;
[0022] Each of the first test pieces is subjected to at least two acid solution cleaning processes to remove the first test piece of a predetermined thickness; wherein, different first test pieces have different thicknesses of first test pieces removed in at least one of the at least two acid solution cleaning processes;
[0023] The number of watermarks on the surface of each first test piece is detected, and several first test pieces that meet the first preset standard are selected; and,
[0024] Obtain the wet cleaning process formula for several of the first test pieces that meet the first preset standard.
[0025] Optionally, in the testing method for the wet cleaning process, the wet cleaning process formulation corresponding to the test group that meets the first preset standard includes:
[0026] The first test piece is subjected to the acid solution cleaning process twice; wherein, the first acid solution cleaning process removes the first test piece of a first thickness, and the second acid solution cleaning process removes the first test piece of a second thickness; and the second thickness accounts for more than 30% of the first thickness.
[0027] Optionally, in the wet cleaning process testing method, after obtaining the wet cleaning process formula of several first test pieces that meet the first preset standard, the wet cleaning process testing method further includes:
[0028] Provide multiple second test pieces, and divide the multiple second test pieces into several test groups;
[0029] Each of the test groups corresponds to one of the wet cleaning process formulations;
[0030] The number of watermarks on the surface of the second test piece in each test group is detected, and test groups that meet the second preset standard are selected; and,
[0031] Obtain the wet cleaning process formula corresponding to the test group that meets the second preset standard.
[0032] Optionally, in the testing method for the wet cleaning process, during the execution of one wet cleaning process formula for each test group, some of the test groups execute the corresponding wet cleaning process formula on different wet cleaning machines.
[0033] Optionally, in the test method for the wet cleaning process, the process time for performing the acid solution cleaning process at least twice on the first test piece or the second test piece is greater than or equal to 4 minutes.
[0034] Optionally, in the test method for the wet cleaning process, the acid solution used in the acid solution cleaning process includes hydrofluoric acid solution, and the mass fraction of the hydrofluoric acid solution is greater than or equal to 0.4%.
[0035] In summary, this invention provides a wet cleaning process and its testing method. Compared to existing technologies, in this wet cleaning process, the acid solution cleaning process is divided into two or more steps for sequential etching and cleaning of the wafer surface. This not only effectively controls the total etching amount at the current site, avoiding over-etching, but also significantly improves the watermark defects on the wafer surface, enhancing the wet cleaning process effect. Furthermore, in the testing method of this wet cleaning process, by setting different thicknesses of the first test piece removed in at least one of the at least two acid solution cleaning processes, various wet cleaning process formulations are obtained. Based on the detection results of the corresponding watermark quantity for various wet cleaning process formulations, a wet cleaning process formulation that meets a first preset standard is selected. This formulation allows for a balance between controlling the total etching amount and improving the watermark defect problem, thereby improving the cleaning effect. Attached Figure Description
[0036] Those skilled in the art will understand that the accompanying drawings are provided to better understand the invention and do not constitute any limitation on the scope of the invention.
[0037] Figure 1 This is a schematic diagram of the distribution of watermark defects in existing technology.
[0038] Figure 2 This is a schematic diagram of the morphology of watermark defects in the prior art.
[0039] Figure 3 This is a flowchart of the first part of the testing method for the wet cleaning process in an embodiment of the present invention.
[0040] Figure 4 This is a schematic diagram of the structure of the first test piece in an embodiment of the present invention.
[0041] Figure 5 This is a schematic diagram of the contact angle in an embodiment of the present invention.
[0042] Figure 6 This is a schematic diagram of the structure of the first test piece after removing the first thickness in an embodiment of the present invention.
[0043] Figure 7 This is a schematic diagram of the structure of the first test piece after removing the second thickness in an embodiment of the present invention.
[0044] Figure 8 This is a comparison chart of test results corresponding to the wet cleaning process formulations in Table 2 of the embodiments of the present invention.
[0045] Figure 9 This is the second part of the flowchart of the testing method for the wet cleaning process in this embodiment of the invention.
[0046] Figure 10This is a schematic diagram of the structure of the second test piece in an embodiment of the present invention.
[0047] Figure 11 This is a schematic diagram of the structure of the second test piece after removing the preset thickness in an embodiment of the present invention.
[0048] Figure 12 This is a comparison chart of the test results corresponding to the wet cleaning process formulations in Tables 3 to 5 of the embodiments of the present invention.
[0049] Figure 13 This is a flowchart of the wet cleaning process in an embodiment of the present invention.
[0050] Figure 14 This is a distribution diagram of watermark defects on the wafer surface after ordinary cleaning in an embodiment of the present invention.
[0051] Figure 15 This is a distribution diagram of watermark defects on the wafer surface after wet cleaning process in an embodiment of the present invention.
[0052] And, in the attached image:
[0053] 10 - First test piece; 100 - First substrate; 101 - First oxide layer; 102 - First nitride layer;
[0054] 20 - Second test piece; 200 - Second substrate; 201 - Second oxide layer; 202 - Second nitride layer;
[0055] W - Wafer; P - Watermark; T - Trench; D - Preset thickness; d1 - First thickness; d2 - Second thickness. Detailed Implementation
[0056] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to facilitate and clearly illustrate the objectives of the embodiments of the present invention. Furthermore, the structures shown in the drawings are often part of the actual structures. In particular, different figures may emphasize different aspects and sometimes use different scales. It should also be understood that, unless specifically stated or indicated, the terms "first," "second," "third," etc., in the specification are only used to distinguish the various components, elements, steps, etc., in the specification, and are not used to indicate the logical or sequential relationships between the various components, elements, steps, etc.
[0057] As described above, existing wet cleaning process formulations cannot simultaneously address the etching thickness at the current site and mitigate watermark defects on the wafer surface. Therefore, this embodiment provides a testing method for a wet cleaning process to obtain a better wet cleaning process formulation. This method not only avoids excessive etching caused by wet cleaning but also effectively alleviates watermark defects on the wafer surface, thereby improving device performance.
[0058] For details, please refer to Figures 3 to 15 The testing method for the wet cleaning process provided in this embodiment includes:
[0059] Step 1 S100: Please refer to Figure 4 Multiple first test chips 10 are provided.
[0060] It should be noted that the first test wafer 10 is a special type of wafer used in the chip manufacturing process to test the process status of the production equipment or the quality of the wafer under a certain process. In this embodiment, multiple first test wafers 10 are used to test the process effects of different wet cleaning process formulations.
[0061] Preferably, the first test wafer 10 can be any substrate known to those skilled in the art for carrying semiconductor integrated circuit components; it can be a bare die, a wafer processed by epitaxial growth, or a circuit structure with devices already formed. For example... Figure 4 As shown, the first test piece 10 includes a first substrate 100 and a first oxide layer 101 and a first nitride layer 102 sequentially formed on the first substrate 100. The first test piece 10 also has a trench T, which sequentially penetrates the first nitride layer 102 and the first oxide layer 101 and extends into the substrate 100. The first nitride layer 102 has a certain degree of water repellency and is prone to watermark defects during wet cleaning after a push-back etching process on the first nitride layer 102.
[0062] Step 2 S101: Please refer to Figure 4 and Figure 5 SC1 cleaning process and / or SC2 cleaning process are performed on each of the first test pieces 10.
[0063] In step two, S101, each of the first test pieces 10 can undergo an SC1 cleaning process, an SC2 cleaning process, or both. The SC1 cleaning process uses a mixture of ammonia, hydrogen peroxide, and water to remove oxidative contaminant particles from the surface of the first test pieces 10. The SC2 cleaning process uses a mixture of hydrochloric acid, hydrogen peroxide, and water to primarily remove metallic contaminant particles from the surface of the first test pieces 10. After cleaning the first test pieces 10 using either the SC1 or SC2 process, a Quick Drain and Rinse (QDR) process is required to remove particulate impurities and improve the cleaning effect.
[0064] It should be noted that different types of cleaning solutions affect the hydrophilicity of the wafer surface. Wafer surfaces with lower hydrophilicity are more prone to forming water droplets upon contact with the cleaning solution, leading not only to poor cleaning results but also to increased watermark defects on the wafer surface after drying. Therefore, hydrophilicity is one of the influencing factors in wet cleaning processes. Furthermore, to quantify hydrophilicity, such as... Figure 5 As shown, this embodiment uses the contact angle θ to characterize the hydrophilicity of the solid surface. The contact angle θ refers to the surface tension of the liquid. With liquid-solid interfacial tension The larger the contact angle θ, the worse its hydrophilicity.
[0065] Furthermore, as shown in Table 1, when the wafer surface is not treated with other chemical solutions, the contact angle θ between the wafer and water is as high as 78°, indicating poor hydrophilicity. However, after treatment with SC1 or SC2 cleaning processes, the contact angle θ between the wafer surface and the cleaning solution is significantly reduced, effectively improving the hydrophilicity of the wafer surface, which is beneficial for improving the cleaning effect and reducing the formation of watermark defects. However, since the cleaning effect of SC1 and SC2 cleaning processes is limited, acid solutions are generally added to the wet cleaning process formulation to obtain a high degree of cleanliness. For example, hydrofluoric acid (DHF) solution is used to clean the wafer surface. As shown in Table 1, directly treating the wafer with DHF will increase the contact angle θ between the wafer and the cleaning solution, which will actually reduce the hydrophilicity of the wafer surface. This not only increases the cleaning difficulty and affects the cleaning effect, but also easily increases the degree of watermark defects. Therefore, the testing method provided in this embodiment first uses the SC1 cleaning process and / or the SC2 cleaning process to optimize the hydrophilicity of the surface of the first test piece 10, and then uses the acid solution cleaning process to further clean the first test piece 10 (see step three S102 below). This can at least reduce the cleaning difficulty and ensure a better cleaning effect.
[0066] Table 1. Contact angles of wafer surfaces after treatment with different cleaning solutions
[0067] Types of cleaning fluids / SC1 SC2 DHF Contact angle θ 78° 5° 30° 80°
[0068] Step 3 S102: Please refer to Figure 6 and Figure 7 Each of the first test pieces 10 is subjected to at least two acid solution cleaning processes to remove the first test piece 10 of a preset thickness D; wherein, different first test pieces 10 have different thicknesses of the first test piece 10 removed at least once in the at least two acid solution cleaning processes.
[0069] It is understood that cleaning the first test piece 10 with acid solution utilizes the wet etching principle to remove a portion of the thickness of the first test piece 10, thereby further improving the cleaning effect. Furthermore, the applicant's experiments have shown that performing multiple acid solution cleanings not only improves the cleaning effect but also helps remove watermark defects. Therefore, while avoiding excessive etching of the first test piece 10, the testing method provided in this embodiment breaks down the single acid solution cleaning process into two or more acid solution cleaning processes to balance stable etching amount and alleviate watermark defects. That is, after step three S102, only a preset thickness D of the first test piece 10 is removed, while simultaneously effectively improving the watermark defect problem.
[0070] Therefore, to achieve better improvement in watermark defects, in step three S102, different acid solution cleaning process formulations are used for different first test pieces 10. That is, when performing the acid solution cleaning process on multiple first test pieces 10, at least once in all the acid solution cleaning processes performed on different first test pieces 10, the thickness of the portion of the first test piece 10 removed by the acid solution cleaning process is different.
[0071] For example, with the same preceding processes, each of the first test pieces 10 undergoes two acid solution cleaning processes. Since the top surface of the first test piece 10 is a first nitride layer 102, the acid solution is preferably a hydrofluoric acid solution. Furthermore, to ensure the etching and cleaning effect of the hydrofluoric acid solution, the mass fraction of the hydrofluoric acid solution is greater than or equal to 0.4%. Please refer to... Figure 6 and Figure 7 Assuming that after step three S102, each of the first test pieces 10 has a preset thickness D = 120 angstroms removed, after the first acid solution cleaning process, the first test piece 10 removes the membrane structure of the first thickness d1; after the second acid solution cleaning process, the first test piece 10 removes the membrane structure of the second thickness d2, and D = d1 + d2.
[0072] Preferably, to obtain a better wet cleaning process formulation, the testing method provided in this embodiment forms various acid solution cleaning process formulations as shown in Table 2 below, according to a gradient variation. Specifically, six of the first test pieces 10 are selected, and the combinations of the first thickness d1 and the second thickness d2 removed in their respective first and second acid solution cleaning processes are (110, 10), (100, 20), (95, 25), (90, 30), (85, 35), and (80, 40), respectively; unit: angstroms. Furthermore, to more intuitively compare the impact of performing two acid solution cleaning processes versus performing one acid solution cleaning process on watermark formation, the applicant also selected the first test piece 10 numbered 1 to perform one hydrofluoric acid solution cleaning process, removing a preset thickness D in one go. Subsequently, after drying, the testing machine picks up defect samples from the surface of the first test piece 10 numbered 1, and a total of 200 defects are found in the defect samples, all of which are watermark defects. Therefore, the watermark occurrence rate of the first test piece 10 numbered 1 is 100%. Furthermore, the testing machine picks up a defect sample from the surface of the first test piece 10, number 2, and finds a total of 100 defects in the sample, of which 92 are watermark defects. Therefore, the watermark incidence rate of the first test piece 10, number 2, is 92%. Similarly, the remaining first test pieces 10 are inspected by picking up defect samples from the testing machine to obtain the watermark incidence rates of the first test piece 10, number 3, number 4, number 5, number 6, number 7, and number 88.50%.
[0073] Table 2 Relationship between acid solution cleaning process formulation and watermark removal effect
[0074] First test piece number First thickness d1 (angstroms) Second thickness d2 (angstroms) Number of watermarks (pieces) Watermark incidence rate (%) 1 120 0 200 100.00 2 110 10 92 92.00 3 100 20 154 77.00 4 95 25 142 71.00 5 90 30 75 37.50 6 85 35 21 11.17 7 80 40 177 88.50
[0075] It should be further noted that, to ensure the feasibility of performing at least two acid solution cleaning processes, the process time for performing at least two acid solution cleaning processes on each of the first test pieces 10 needs to be greater than or equal to 4 minutes. If the process time is too short, the process of performing acid solution cleaning in stages will be too difficult, making it difficult to meet the requirements of actual engineering applications and thus not feasible.
[0076] Step 4 S103: Please refer to Figure 7 and Figure 8 The number of watermarks on the surface of each of the first test pieces 10 is detected, and a number of the first test pieces 10 that meet the first preset standard are selected; and,
[0077] Step 5 S104: Please refer to Figure 7 and Figure 8 Obtain several wet cleaning process formulas for the first test piece 10 that meet the first preset standard.
[0078] After performing step three S102, each of the first test pieces 10 undergoes an overflow rinsing and drying process. Then, the number of watermarks on the surface of each first test piece 10 is detected by a machine, and the results are used to generate Table 2 above. Figure 8 .
[0079] Please continue reading. Figure 8 As shown in Table 2 above, compared to the first test piece 10 numbered 1, the number and incidence of watermarks on the first test pieces 10 numbered 2 to 7 are significantly reduced, thus verifying the conclusion that performing acid solution cleaning processes two or more times is beneficial to improving watermark defects. Furthermore, the watermark incidence rates corresponding to the first test pieces 10 numbered 5 and 6 are relatively low; that is, using… as well as, These two acid solution cleaning process formulations show good improvement in watermark defects. Assuming the first preset standard is a watermark incidence rate of less than 45%, acid solution cleaning process formulations for the first test piece 10, numbered 5 and 6, can be selected as the superior wet cleaning process formulations selected through testing. The wet cleaning process formulation includes, but is not limited to, the specific process steps and related parameters for the corresponding first test piece 10 in steps two (S101) and three (102), particularly including the portion of the thickness of the first test piece 10 removed by each execution of the acid solution cleaning process.
[0080] It should be noted that this embodiment does not limit the specific form of the first preset standard. It can be a watermark occurrence rate of less than 45%, less than 40%, or less than 50%, etc., which can be determined according to specific process requirements. Furthermore, as verified by the applicant, when the first test piece 10 is subjected to the acid solution cleaning process twice, preferably, the wet cleaning process formulation corresponding to the test group that meets the first preset standard includes: a first acid solution cleaning process removing the first test piece 10 of a first thickness d1, and a second acid solution cleaning process removing the first test piece 10 of a second thickness d2; and the proportion of the second thickness d2 relative to the first thickness d1 is greater than or equal to 30%. That is, d2 ≥ 30%d1. In actual processes, the first test piece 10 can be replaced with a wafer.
[0081] As described above, through the testing process from step one (S100) to step five (S104), a better wet cleaning formula can be selected to effectively alleviate watermark defects while avoiding excessive wet etching. Furthermore, to ensure the obtained wet cleaning formula has good repeatability, the testing method provided in this embodiment also includes the following steps (e.g. Figure 9 As shown):
[0082] Step 6 S105: Please refer to Figure 10 Provide multiple second test pieces 20 and divide the multiple second test pieces 20 into several test groups.
[0083] The second test piece 20 and Figure 4 The first test piece 10 shown has the same material and structure. For example, the second test piece 20 includes a second substrate 200 and a second oxide layer 201 and a second nitride layer 202 sequentially formed on the second substrate 200. The second test piece 20 also has a trench T, which sequentially penetrates the second nitride layer 202 and the second oxide layer 201 and extends into the second substrate 200.
[0084] Furthermore, to verify the reliability of the wet cleaning process formula obtained in step five S104, the number of test groups can be determined according to the type of wet cleaning process formula. For example, if two wet cleaning process formulas are obtained in step five S104, two test groups are set up, and each test group includes multiple second test pieces 20. Also, to verify the process effect of the wet cleaning process formula on different machines, the number of test groups can be determined in conjunction with the number of test machines. For example, the testing method uses two machines; two test groups are configured for the first machine to execute two different wet cleaning process formulas respectively; two test groups can also be configured for the second machine to execute two different wet cleaning process formulas respectively; or only one test group can be configured for the second machine to execute one of the wet cleaning process formulas. The number of second test pieces 20 included in each test group is not specifically limited in this embodiment and can be two, three, four, or five pieces, etc.
[0085] Step 7 S106: Each of the test groups corresponds to one of the wet cleaning process formulations;
[0086] Step 8 S107: Detect the number of watermarks on the surface of the second test piece 20 in each test group, and select the test groups that meet the second preset standard; and,
[0087] Step 9 S108: Obtain the wet cleaning process formula corresponding to the test group that meets the second preset standard.
[0088] It is understood that when the number of test groups corresponds one-to-one with the number of types of wet cleaning process formulations, the second test piece 20 in each test group executes one corresponding wet cleaning process formulation, and all second test pieces 20 in the same group execute the same type of wet cleaning process formulation. For example, if step five S104 obtains two wet cleaning process formulations, and step six S105 sets up two test groups, with three second test pieces 20 in each test group, then the three second test pieces 20 in the first group execute the first wet cleaning process formulation, and the three second test pieces 20 in the second group execute the second wet cleaning process formulation. When there are two or more machines, one or more test groups can be set up to execute various wet cleaning process formulations on different machines. For example, in step five (S104), two wet cleaning process formulations are obtained, and experimental testing needs to be conducted on two machines. On the first machine, two test groups are selected to execute the two wet cleaning process formulations respectively. On the second machine, one test group is selected to execute the first wet cleaning process formulation, so that the execution effect of the same wet cleaning process on the first and second machines can be compared. Of course, depending on the required testing accuracy, multiple test groups and multiple machines can be set to execute various wet cleaning process formulations; this embodiment does not specifically limit this.
[0089] For example, such as Figure 10 and Figure 11 As shown, in step six S105, three test groups are set up: the first test group includes ten pieces of the second test piece 20, the second test group includes six pieces of the second test piece 20, and the third test group includes two pieces of the second test piece 20. Furthermore, in step five S104, two wet cleaning process formulations are screened. The first wet cleaning process formulation includes performing two acid solution cleaning processes: the first acid solution cleaning process removes a first thickness d1 = 90 angstroms, and the second acid solution cleaning process removes a second thickness d2 = 30 angstroms. The second wet cleaning process formulation also includes performing two acid solution cleaning processes: the first acid solution cleaning process removes a first thickness d1 = 85 angstroms, and the second acid solution cleaning process removes a second thickness d2 = 35 angstroms. Preferably, the acid solution is DHF. Based on this, the ten second test pieces 20 in the first test group were subjected to the first wet cleaning process formula using the first machine; the six second test pieces 20 in the second test group were subjected to the second wet cleaning process formula using the first machine; and the two second test pieces 20 in the third test group were subjected to the first wet cleaning process formula using the second machine. After each wet cleaning process formula was completed, each second test piece 20 was dried, and watermark defects on the surface of each second test piece 20 were detected, resulting in Tables 3 to 5 below. Figure 12 .
[0090] As shown in Tables 3 and 5, under the first wet cleaning process formulation, the watermark defects on the surface of the second test piece 20 are well suppressed regardless of whether the first or second machine is used, indicating that the formulation has strong repeatability and good reliability. As shown in Table 4, the improvement of the watermark defects on the surface of the second test piece 20 by the second wet cleaning process formulation has a certain degree of randomness. That is, only one second test piece 20 shows a good improvement effect, while the others show little effect. Therefore, the repeatability of the second wet cleaning process formulation is poor, and its reliability is low.
[0091] Table 3. Statistics of watermark defects after applying the first wet cleaning process formula using the first machine.
[0092] Second test piece number Number of watermarks (pieces) Watermark incidence rate (%) 1-1 75 37.50 1-2 69 34.50 1-3 69 34.50 1-4 53 26.50 1-5 53 26.50 1-6 53 26.50 1-7 50 25.00 1-8 50 25.00 1-9 50 25.00 1-10 50 25.00
[0093] Table 4. Statistics of watermark defects after applying the second wet cleaning process formula using the first machine.
[0094] Second test piece number Number of watermarks (pieces) Watermark incidence rate (%) 2-1 21 11.17 2-2 131 65.50 2-3 131 65.50 2-4 130 65.00 2-5 130 65.00 2-6 130 65.00
[0095] Table 5. Statistics of watermark defects after applying the first wet cleaning process formula using the second machine.
[0096] Second test piece number Number of watermarks (pieces) Watermark incidence rate (%) 3-1 85 42.50 3-2 85 42.50
[0097] Therefore, based on the above test data, the wet cleaning process formulation that meets the reliability requirements can be further screened as the target wet cleaning process formulation finally selected by the test method. For example, the first wet cleaning process formulation is selected as the target wet cleaning process formulation to address both the etching thickness at the current site and the improvement of watermark defects on the wafer surface.
[0098] In summary, the above-described wet cleaning process can identify a superior wet cleaning process formulation to effectively improve watermark defects on the wafer surface while avoiding excessive etching. Therefore, this embodiment also provides a wet cleaning process for applying the wet cleaning process formulation selected through testing methods.
[0099] Please see Figure 13 The wet cleaning process includes:
[0100] Step 1 S200: Provide a wafer;
[0101] The wafer can be any substrate known to those skilled in the art for carrying semiconductor integrated circuit components. It can be a bare die, a substrate structure processed by epitaxial growth, or a semiconductor structure with a device layer already formed.
[0102] Step 2 S201: Perform SC1 cleaning process and / or SC2 cleaning process on the wafer.
[0103] Optionally, the wafer may be subjected to an SC1 cleaning process, an SC2 cleaning process, or both SC1 and SC2 cleaning processes. After completing the SC1 or SC2 cleaning process, a rapid flushing process is required to clean the wafer. The treated wafer has better hydrophilicity, which not only reduces the cleaning difficulty of subsequent acid solution cleaning processes and improves the cleaning effect, but also alleviates the degree of watermark defects.
[0104] Step 3 S202: Perform at least two acid solution cleaning processes on the wafer to remove the wafer of a predetermined thickness.
[0105] That is, in step three S202, the etching amount of the one-time acid solution cleaning process is divided into multiple acid solution cleanings, to be etched sequentially until the preset thickness is reached. Preferably, the wafer is subjected to two acid solution cleaning processes; wherein the first acid solution cleaning process removes a first thickness of the wafer, and the second acid solution cleaning process removes a second thickness of the wafer; and the second thickness accounts for more than or equal to 30% of the first thickness. For example, in the two acid solution cleaning processes performed on the wafer, the first acid solution cleaning process removes a first thickness of 90 angstroms from the wafer's film structure, and the second acid solution cleaning process removes a second thickness of 30 angstroms from the wafer's film structure.
[0106] Furthermore, to verify the effectiveness of the wet cleaning process provided in this embodiment, the applicant experimentally compared the cleaning effects of existing cleaning processes with those of the wet cleaning process provided in this embodiment. Figure 14 and Figure 15 As shown, the number of watermarks P on the wafer surface is significantly reduced after cleaning by the wet cleaning process provided in this embodiment, effectively improving the cleaning effect.
[0107] It should be noted that this embodiment does not limit the specific type of acid solution used in the acid solution cleaning process, and can be determined according to the film structure on the wafer surface. For example, if a nitride layer is formed on the wafer surface, hydrofluoric acid solution is used as the cleaning agent, and the wafer is subjected to at least two acid solution cleaning processes. To ensure cleaning effectiveness, the mass fraction of the hydrofluoric acid solution is greater than or equal to 0.4%. Furthermore, to improve the feasibility of the wet cleaning process, the process time for performing the at least two acid solution cleaning processes on the wafer is greater than or equal to 4 minutes. For example, performing the acid solution cleaning process on the wafer a total of two times, with a total process time greater than or equal to 4 minutes, can be 4 minutes, 5 minutes, or 6 minutes, etc.
[0108] Furthermore, after performing step three (S202), the wafer needs to undergo overflow rinsing or rapid flushing cleaning processes to ensure optimal cleaning results. After cleaning, the wafer also needs to be dried. This drying process is not limited to IPA drying or Marangoni drying.
[0109] In summary, the wet cleaning process and testing method provided in this embodiment, by dividing the acid solution cleaning process into two or more steps during the wet cleaning of wafers, can perform successive etching and cleaning of the wafer surface. This not only effectively controls the total etching amount at the current site and avoids excessive etching, but also significantly improves the watermark defects on the wafer surface and enhances the process effect of wet cleaning.
[0110] Furthermore, it should be understood that although the present invention has been disclosed above with reference to preferred embodiments, these embodiments are not intended to limit the present invention. For any person skilled in the art, many possible variations and modifications can be made to the technical solutions of the present invention based on the disclosed technical content, or equivalent embodiments can be modified accordingly, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the scope of protection of the present invention.
Claims
1. A wet cleaning process, characterized in that, include: Provide one wafer; Perform SC1 cleaning process and / or SC2 cleaning process on the wafer; The wafer is subjected to at least two acid solution cleaning processes to remove the wafer of a predetermined thickness.
2. The wet cleaning process according to claim 1, characterized in that, In the process of performing at least two acid solution cleaning processes on the wafer to remove wafers of a predetermined thickness, the acid solution cleaning process is performed twice on the wafer; wherein... The first acid solution cleaning process removes the wafer of a first thickness, and the second acid solution cleaning process removes the wafer of a second thickness; wherein the second thickness accounts for more than or equal to 30% of the first thickness.
3. The wet cleaning process according to claim 1, characterized in that, The acid solution used in the acid solution cleaning process includes hydrofluoric acid solution, and the mass fraction of the hydrofluoric acid solution is greater than or equal to 0.4%.
4. The wet cleaning process according to claim 1, characterized in that, The process time for performing the at least two acid solution cleaning processes on the wafer is greater than or equal to 4 minutes.
5. A test method for a wet cleaning process, characterized in that, include: Provide multiple first test pieces; Perform SC1 cleaning process and / or SC2 cleaning process on each of the first test pieces; Each of the first test pieces is subjected to at least two acid solution cleaning processes to remove the first test piece of a predetermined thickness; wherein, different first test pieces have different thicknesses of first test pieces removed in at least one of the at least two acid solution cleaning processes; The number of watermarks on the surface of each first test piece is detected, and several first test pieces that meet the first preset standard are selected. as well as, Obtain the wet cleaning process formula for several of the first test pieces that meet the first preset standard.
6. The test method for the wet cleaning process according to claim 5, characterized in that, The wet cleaning process formulation corresponding to the test group that meets the first preset standard includes: The first test piece is subjected to the acid solution cleaning process twice; wherein, the first acid solution cleaning process removes the first test piece of a first thickness, and the second acid solution cleaning process removes the first test piece of a second thickness; and the second thickness accounts for more than 30% of the first thickness.
7. The test method for the wet cleaning process according to claim 5, characterized in that, After obtaining the wet cleaning process formulas for several first test pieces that meet the first preset standard, the testing method for the wet cleaning process further includes: Provide multiple second test pieces, and divide the multiple second test pieces into several test groups; Each of the test groups corresponds to one of the wet cleaning process formulations; The number of watermarks on the surface of the second test piece in each test group is detected, and test groups that meet the second preset standard are selected; and, Obtain the wet cleaning process formula corresponding to the test group that meets the second preset standard.
8. The test method for the wet cleaning process according to claim 7, characterized in that, During the execution of one wet cleaning process formulation for each of the test groups, some of the test groups execute the corresponding wet cleaning process formulation on different wet cleaning machines.
9. The test method for the wet cleaning process according to claim 7, characterized in that, The process time for performing the acid solution cleaning process at least twice on the first test piece or the second test piece is greater than or equal to 4 minutes.
10. The test method for the wet cleaning process according to any one of claims 5 to 9, characterized in that, The acid solution used in the acid solution cleaning process includes hydrofluoric acid solution, and the mass fraction of the hydrofluoric acid solution is greater than or equal to 0.4%.