Failure evaluation and compensation method for CMP (Chemical Mechanical Polishing) solution

Abstract

The invention provides a CMP polishing solution failure evaluation and compensation method, and relates to the technical field of silicon carbide processing. The failure evaluation method comprises the steps that after the polishing solution is recycled for a period of time, the oxidability, the average grain diameter of abrasive particles and the pH value of the polishing solution are measured, and if the oxidability, the average grain diameter of the abrasive particles and the pH value are all larger than preset values, the polishing solution continues to be used for polishing the next batch of workpieces; and if the oxidability and / or the average grain size of the abrasive grains and / or the pH value are / is smaller than the preset value, the polishing solution is affirmed to be invalid and cannot be continuously used for polishing, and the invalid polishing solution is compensated. The compensation method comprises the following steps: if the measured oxidability and / or average grain diameter of abrasive grains and / or pH value are / is smaller than a preset value, correspondingly adding a potassium permanganate solution, an aluminum oxide suspension and a pH regulator into the polishing solution respectively to enable the three indexes to return to be higher than the preset value, so as to finish the compensation of the invalid polishing solution. The economic cost of frequently replacing the polishing solution can be reduced, and pollution to the environment during waste liquid treatment is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicon carbide processing, in particular, especially relates to a CMP polishing liquid failure evaluation and compensation method. BACKGROUND

[0002] With the rapid development of the semiconductor industry, silicon carbide (SiC) as a new type of wide bandgap semiconductor material, is gradually becoming an important development direction of the power semiconductor industry. Theoretical research and engineering practice show that silicon carbide has excellent properties such as high temperature resistance, high pressure resistance, high frequency, high power and low energy consumption, which expands its application scenarios in strategic emerging industries such as new energy vehicle power systems, photovoltaic grid-connected inverters, rail transit traction converters, and smart grid flexible power transmission devices, and has broad industrialization development prospects.

[0003] In the processing of silicon carbide, chemical mechanical polishing (CMP) is an extremely important link, but as the polishing process proceeds, some properties of the CMP polishing liquid will change, greatly affecting the efficiency of the processing and the surface roughness of the processed SiC wafer, resulting in the obtained processed SiC wafer not meeting the use requirements. If the polishing liquid is replaced after finding unqualified SiC wafers, the number of unqualified SiC wafers will increase. At the same time, in addition to the aluminum oxide abrasive particles in the polishing liquid used for CMP of the SiC wafer, there is also the oxidizing agent potassium permanganate. Since potassium permanganate has strong oxidizing properties, direct discharge will cause a lot of pollution, in addition, manganese as a harmful transition metal needs to use a large amount of acid in wastewater treatment, which undoubtedly brings another heavy harm to the environment.

[0004] Therefore, it is necessary to provide a way that can evaluate the failure of the polishing liquid and compensate for the recovery of the failed polishing liquid to achieve reutilization, effectively reduce the treatment cost of waste liquid and pollution to the environment, so as to achieve the goal of green chemistry. SUMMARY

[0005] According to the above technical problems, a CMP polishing liquid failure evaluation and compensation method is provided.

[0006] The technical means adopted by the present application are as follows: A CMP polishing liquid failure evaluation method, comprising the following steps: Step 1, after the polishing liquid polishes a batch of workpieces for a period of time, the oxidizing property, the average particle size of abrasive particles and the pH value of the polishing liquid are measured; Step 2, judging whether the oxidizing property, the average particle size of abrasive particles and the pH value of the polishing liquid are all greater than the preset value; Step 3, if the measured oxidation, average particle size of abrasive particles and pH value are all greater than the preset value, then continue to polish the next batch of workpieces with the polishing liquid; Step 4, if the measured oxidation and / or average particle size of abrasive particles and / or pH value are less than the preset value, then it is determined that the polishing liquid is invalid, which is the invalid polishing liquid, and the invalid polishing liquid cannot be used for polishing any more, and the invalid polishing liquid is compensated and then used for polishing workpieces again.

[0007] Further, in the step 1, the oxidation of the polishing liquid is measured by using a redox titration method or an electrochemical method.

[0008] Further, in the step 1, the average particle size of abrasive particles of the polishing liquid is measured by using a laser particle size analysis method or a scanning electron microscope method.

[0009] Further, in the step 1, the pH value of the polishing liquid is measured by using a pH meter or a pH indicator.

[0010] Further, in the step 2, the method for determining the preset value comprises: determining the preset value according to the corresponding relationship between the material removal rate and the surface roughness of each batch of workpieces polished by the polishing liquid and the oxidation, the average particle size of abrasive particles and the pH value; continuously polishing multiple batches of workpieces using the polishing liquid prepared in the same batch, the polishing liquid prepared in the same batch is a continuous circulation system, after polishing each batch of workpieces, the material removal rate and the surface roughness are measured, then the polishing liquid is continuously used for polishing the next batch of workpieces, and the circulation is repeated, so that the corresponding relationship between the oxidation, the average particle size of abrasive particles and the pH value of the polishing liquid and the material removal rate and the surface roughness of the workpieces is obtained. When the material removal rate does not meet the requirement or the surface roughness of the workpiece does not meet the requirement after a certain processing, it is considered that the oxidation, the average particle size of abrasive particles and the pH value of the polishing liquid corresponding to the previous processing are the required preset values.

[0011] The application also provides a compensation method for compensating the invalid polishing liquid in the invalid evaluation method of the CMP polishing liquid. S1, filtering the invalid polishing liquid to obtain a first polishing liquid; S2, adding a certain mass of potassium permanganate solution and / or alumina suspension and / or acid-base regulator into the first polishing liquid to obtain a second polishing liquid; S21, when the oxidation of the invalid polishing liquid is lower than the preset value, supplementing a certain mass of potassium permanganate solution into the first polishing liquid; S22, when the average particle size of abrasive particles of the invalid polishing liquid is lower than the preset value, supplementing a certain mass of alumina suspension into the first polishing liquid; S23, when the pH value of the invalid polishing liquid is lower than the preset value, supplementing a certain mass of acid-base regulator into the first polishing liquid; S3, measuring the oxidizability, the average particle size of abrasive grains and the pH value of the second polishing liquid; if the measured oxidizability, the average particle size of abrasive grains and the pH value are all greater than the preset values, the second polishing liquid can continue to be used for polishing workpieces; if the measured oxidizability and / or the average particle size of abrasive grains and / or the pH value are less than the preset values, repeating S1-S3 until the oxidizability, the average particle size of abrasive grains and the pH value are all greater than the preset values.

[0012] Further, in S2, the mass of the added potassium permanganate solution and the alumina suspension is 1 / 5-1 / 3 of the mass of the original invalid polishing liquid, and the mass of the added acid-base regulator is 1%-5% of the mass of the original invalid polishing liquid.

[0013] Compared with the prior art, the present application has the following advantages: 1. The CMP polishing liquid failure evaluation and compensation method provided by the present application, after the polishing liquid is used for a period of time, the oxidizability, the average particle size of abrasive grains and the pH value of the polishing liquid are measured to determine whether the oxidizability, the average particle size of abrasive grains and the pH value are all greater than the preset values, to determine whether the polishing liquid is used for polishing the next batch of workpieces or the polishing liquid is invalid and the invalid polishing liquid is compensated. If the measured oxidizability, the average particle size of abrasive grains and the pH value are all greater than the preset values, the polishing liquid is used for polishing the next batch of workpieces; if the measured oxidizability and / or the average particle size of abrasive grains and / or the pH value are less than the preset values, the polishing liquid is determined to be invalid and cannot be used for polishing, and the invalid polishing liquid needs to be compensated.

[0014] 2. The CMP polishing liquid failure evaluation and compensation method provided by the present application, after the polishing liquid is used for a period of time, if the measured oxidizability and / or the average particle size of abrasive grains and / or the pH value of the polishing liquid are less than the preset values, the corresponding potassium permanganate solution, alumina suspension and pH regulator are added into the polishing liquid to make the three indexes return to above the preset values, to complete the compensation of the invalid polishing liquid, which can reduce the economic cost of frequent replacement of the polishing liquid and reduce the pollution to the environment caused by the treatment of waste liquid.

[0015] Based on the above reasons, the present application can be widely popularized in the field of silicon carbide processing and the like. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative labor.

[0017] Figure 1 Flow chart for the method of the present invention for evaluating the effectiveness of a polishing liquid.

[0018] Figure 2 Flow chart for the method of the present invention for compensating for an ineffective polishing liquid.

[0019] Figure 3 Bar chart of material removal rate for each example and comparative example.

[0020] Figure 4 Bar chart of surface roughness for each example and comparative example. DETAILED DESCRIPTION

[0021] It should be noted that the embodiments and features of the embodiments in the present application can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0022] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0023] It should be noted that the terms used herein are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and it should also be understood that when the terms "comprise" and / or "include" are used in the specification, there is a presence of a feature, step, operation, device, component and / or combinations thereof.

[0024] The foregoing is considered as illustrative only of the principles of the application. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the application to the exact construction and practice described. Accordingly, all such variations are intended to be included within the scope of the present application as defined in the following claims, along with full equivalents thereof. It is to be understood that the phraseology and terminology employed herein are for the purpose of description and not of limitation. Any use of section headings is intended to aid reading the application and is not to be interpreted as limiting. Further, unless otherwise specifically indicated, it is intended that all of the units, prefixes, symbols and numerical notations are preferred embodiments of the present application. Nonetheless, except where otherwise indicated, the same are intended to be permissive of equivalents and alternatives on all subjects matter for which they are invoked. Numerous specific embodiments of the application have been set forth herein. The skilled artisan will understand, however, that various modifications can be made to the specific embodiments described without departing from the scope of the present application, which is defined by the appended claims. Accordingly, the particular embodiments described are shown by way of example and not limitations. It is intended to cover all alternatives, modifications and equivalents. In addition, while a particular feature of the application can have been disclosed with respect to only one of several embodiments, such feature can be combined with one or more other features of the same or different embodiments. Furthermore, to the extent that any reference is made herein to a method comprising two or more defined steps, it is contemplated that such a method can be performed in any order, unless otherwise specified. It should also be understood that any numerical range recited herein includes all values from the lower and upper limits of that range. It is intended that every maximum numerical limitation recited herein includes every minimum numerical limitation between the recited maximum and the maximum itself. It is intended that every minimum numerical limitation recited herein includes every maximum numerical limitation between the recited minimum and the minimum itself. Any numerical range recited herein includes all sub-ranges subsumed therein. For example, a range of "1 to 10" includes all sub-ranges between (and including) the minimum of 1 and the maximum of 10, that is, all sub-ranges beginning with a minimum of 1 or more and ending with a maximum of 10 or less, e.g., 5.0 to 9.3. Further, any numerical value contained herein can be expressed as approximately or alternatively, as simply followed by "or more" or "or less" to indicate any range encompassed therein. Also, the terms in the claims have their plain, ordinary meaning. No special meaning is to be given to substantive names of process steps or material or component parts, unless expressly so defined by the patentee. No disclaimer of any claim limitation is intended, except as expressly set forth in the following claims.

[0025] In order to reduce the high cost of polishing liquid loss when SiC wafer is subjected to CMP, and reduce the pollution to the environment when the waste liquid is treated, the present application provides a CMP polishing liquid failure evaluation and compensation method, which is a failure evaluation method for the polishing liquid used for CMP of SiC wafer, and a compensation method for the failure polishing liquid.

[0026] In the first aspect, the present application provides a CMP polishing liquid failure evaluation method, as shown in the formula (I), specifically comprising: Figure 1 Step 1, after the polishing liquid is used to polish a batch of SiC wafers for a period of time, the oxidation, average particle size of abrasive particles and pH value of the polishing liquid are measured; Step 2, judging whether the oxidation, average particle size of abrasive particles and pH value of the polishing liquid are all greater than the preset value; Step 3, if the measured oxidation, average particle size of abrasive particles and pH value are all greater than the preset value, the polishing liquid is continued to be used to polish the next batch of workpieces.

[0027] Step 4, if the measured oxidation and / or average particle size of abrasive particles and / or pH value is less than the preset value, the polishing liquid is considered to be failure, which is failure polishing liquid, and the polishing liquid cannot be used for polishing, and the polishing liquid needs to be compensated.

[0028] The evaluation method comprises measuring three indexes of the polishing liquid, and if any one or more indexes is less than the preset value, the polishing liquid is considered to be failure.

[0029] The evaluation method further comprises a method for determining the preset value of the oxidation, average particle size of abrasive particles and pH value, specifically comprising: ​Multiple batches of SiC wafers were polished continuously using the same batch of polishing slurry. The oxidizing property, average abrasive particle size, and pH value of the polishing slurry were measured after each polishing. The surface roughness of each batch of SiC wafers was also measured, and the material removal rate of each polishing was calculated.

[0030] Based on the measurement data, the corresponding relationships among the oxidizability of the polishing liquid, the average particle size of the abrasive particles, the pH value, the material removal rate, and the surface roughness of the SiC wafer can be obtained.

[0031] The preset value can be determined according to the corresponding relationship.

[0032] When the material removal rate does not meet the requirements or the surface roughness of the SiC wafer does not meet the requirements after a certain processing, it can be considered that the oxidizing property, average particle size of the abrasive particles and pH value of the polishing liquid corresponding to the processing before this processing are the required preset values.

[0033] In step 1, the oxidizing property of the polishing liquid can be measured by a redox titration method or an electrochemical method. The present invention does not limit the measuring method, as long as the oxidizing property can be accurately measured.

[0034] In step 1, the average particle size of the abrasive particles in the polishing liquid is measured by laser particle size analysis or scanning electron microscopy (SEM). The present invention is not limited to the measurement method, as long as the average particle size of the abrasive particles can be accurately measured.

[0035] In step 1, the pH value of the polishing liquid is measured. A pH meter or a pH indicator can be used for measurement. The present invention does not limit the measurement method, as long as the pH value can be accurately measured.

[0036] In a second aspect, the present invention provides a method for compensating for a spent polishing liquid, such as Figure 2 As shown, including: S1. If the measured oxidizability and / or average abrasive particle size and / or pH value are less than the preset values, the polishing liquid is deemed to be invalid and needs to be compensated; S2. Correspondingly, a certain amount of potassium permanganate solution and / or aluminum oxide suspension and / or pH regulator (acid-base regulator) is added to the spent polishing slurry, and then the oxidizability, average abrasive particle size, and pH value of the polishing slurry are re-measured; S3. If the measured oxidizability, average abrasive particle size, and pH value are all greater than the preset values, the compensated polishing liquid can continue to be used to polish the silicon carbide wafer; S4. If the measured oxidizability and / or average abrasive particle size and / or pH value are less than the preset values, repeat the above steps until the oxidizability, average abrasive particle size and pH value are all greater than the preset values.

[0037] Specifically: If the oxidizability of the spent polishing liquid is lower than the preset value, the method comprises: 1) filtering the spent polishing liquid to obtain a first polishing liquid; the agglomerates of abrasive grains generated in the polishing process and other impurities in the spent polishing liquid are removed by filtering, so as to avoid interfering with the subsequent compensation operation and preventing the influence on the dispersion uniformity and effect of the replenishing substances such as potassium permanganate solution and alumina suspension.

[0038] 2) supplementing 1 / 5-1 / 3 of the mass of the first polishing liquid with potassium permanganate solution to obtain a second polishing liquid.

[0039] 3) measuring the oxidizability of the second polishing liquid; if the measured oxidizability is greater than the preset value, the second polishing liquid can continue to be used for polishing SiC wafers; if the measured oxidizability is less than the preset value, the above steps are repeated until the oxidizability is greater than the preset value; wherein when the above steps are repeated, if the potassium permanganate solution needs to be supplemented for multiple times, the amount of the potassium permanganate solution supplemented each time is consistent with the amount of the potassium permanganate solution supplemented for the first time.

[0040] If the average particle size of abrasive grains in the spent polishing liquid is lower than the preset value, the method comprises: 1) filtering the spent polishing liquid to remove the agglomerates of abrasive grains generated in the polishing process and other impurities in the spent polishing liquid to obtain a first polishing liquid.

[0041] 2) supplementing 1 / 5-1 / 3 of the mass of the first polishing liquid with alumina suspension to obtain a second polishing liquid.

[0042] 3) measuring the average particle size of abrasive grains in the second polishing liquid; if the measured average particle size of abrasive grains is greater than the preset value, the second polishing liquid can continue to be used for polishing SiC wafers; if the measured average particle size of abrasive grains is less than the preset value, the above steps are repeated until the average particle size of abrasive grains is greater than the preset value; wherein when the above steps are repeated, if the alumina suspension needs to be supplemented for multiple times, the amount of the alumina suspension supplemented each time is consistent with the amount of the alumina suspension supplemented for the first time.

[0043] If the pH value of the spent polishing liquid is lower than the preset value, the method comprises: 1) filtering the spent polishing liquid to remove the agglomerates of abrasive grains generated in the polishing process and other impurities in the spent polishing liquid to obtain a first polishing liquid.

[0044] 2) adding 1%-5% of the mass of the first polishing liquid with an acid-base regulator to obtain a second polishing liquid.

[0045] 3) measuring the pH value of the second polishing liquid; if the measured pH value is greater than the preset value, the second polishing liquid can continue to be used for polishing SiC wafers; if the measured pH value is less than the preset value, the above steps are repeated until the pH value is greater than the preset value; wherein when the above steps are repeated, if the acid-base regulator needs to be supplemented for multiple times, the amount of the acid-base regulator supplemented each time is consistent with the amount of the acid-base regulator supplemented for the first time.

[0046] The compensation method is described for the case that the oxidation, the average particle size of abrasive grains and the pH value of the invalid polishing liquid are lower than the preset values. If the actual situation is that two or more indexes of the polishing liquid are lower than the preset values, the compensation can be performed on all invalid indexes after filtration.

[0047] In the embodiment of the present application, the oxidation of the polishing liquid is measured by an electrochemical method, the average particle size of abrasive grains is measured by a scanning electron microscope (SEM) method, the pH value is measured by a pH meter, and the preset values of the oxidation, the average particle size of abrasive grains and the pH value of the polishing liquid are measured by a preset value measurement method, which are 351.1 nA, 211 nm and 7.5 respectively. At this time, the corresponding material removal rate and the surface roughness of the silicon carbide wafer are 1263 nm / h and 0.13 nm respectively.

[0048] Example 1 The newly prepared polishing liquid is used to polish multiple batches of SiC wafers. When the polishing reaches the third batch of workpieces, the three indexes of the polishing liquid are measured, which are 389.6 nA, 194 nm and 8.1 respectively. At this time, the corresponding material removal rate and the surface roughness of the SiC wafer are 1157 nm / h and 0.13 nm respectively.

[0049] The average particle size of abrasive grains of the polishing liquid is lower than the preset value, and the polishing liquid is determined to be invalid. The polishing liquid is compensated.

[0050] After step C (filtering the invalid polishing liquid to obtain a first polishing liquid), 1 / 5 of the mass of alumina suspension is added to the first polishing liquid in step D (to obtain a second polishing liquid), and the oxidation, the average particle size of abrasive grains and the pH value of the second polishing liquid are measured again, which are 387.5 nA, 237 nm and 8.2 respectively. All of them are greater than the preset values, and the SiC wafers can continue to be polished.

[0051] Polishing test: a new batch of SiC wafers (the fourth batch of workpieces polished by the second polishing liquid) is polished under the same conditions using the second polishing liquid. After polishing, the material removal rate and the surface roughness of the SiC wafer are 1394 nm / h and 0.12 nm respectively.

[0052] Example 2 The newly prepared polishing liquid is used to polish multiple batches of SiC wafers. When the polishing reaches the third batch of workpieces, the three indexes of the polishing liquid are measured, which are 389.6 nA, 194 nm and 8.1 respectively. At this time, the corresponding material removal rate and the surface roughness of the SiC wafer are 1157 nm / h and 0.13 nm respectively.

[0053] The polishing liquid is identified as failure when the average particle size of the polishing liquid is lower than the preset value, and the polishing liquid is compensated.

[0054] After step C (filtering the failure polishing liquid to obtain the first polishing liquid), 1 / 3 of the mass of the potassium permanganate solution is added to the first polishing liquid in step B (adding the potassium permanganate solution to the failure polishing liquid after step A), and then step C (filtering the failure polishing liquid after the addition of the potassium permanganate solution) is performed. Finally, step D (adding the alumina suspension to the failure polishing liquid after step C) is performed, and 1 / 5 of the mass of the alumina suspension is added in step D. The oxidation, average particle size of abrasive particles, and pH value of the second polishing liquid are measured again, and the three values are 395.4 nA, 212 nm, and 7.9, respectively. All three values are greater than the preset values, and the SiC wafer can continue to be polished.

[0055] Polishing test: a new batch of SiC wafers (the 5th batch of workpieces polished by the second polishing liquid) is polished under the same conditions using the second polishing liquid. After polishing, the material removal rate and the surface roughness of the SiC wafer are measured to be 1306 nm / h and 0.12 nm, respectively.

[0056] Example 3 The newly prepared polishing liquid is used to polish multiple batches of SiC wafers. When the 4th batch of workpieces is polished, the three indicators of the polishing liquid are measured, and the three values are 336.8 nA, 181 nm, and 7.8, respectively. At this time, the material removal rate and the surface roughness of the SiC wafer are 1048 nm / h and 0.14 nm, respectively.

[0057] The oxidation and the average particle size of abrasive particles of the polishing liquid are lower than the preset values, and the polishing liquid is identified as failure, and the polishing liquid is compensated.

[0058] After step A (filtering the failure polishing liquid), 1 / 5 of the mass of the potassium permanganate solution is added to the failure polishing liquid after step A in step B (adding the potassium permanganate solution to the failure polishing liquid after step A), and then step C (filtering the failure polishing liquid after the addition of the potassium permanganate solution) is performed. Finally, step D (adding the alumina suspension to the failure polishing liquid after step C) is performed, and 1 / 5 of the mass of the alumina suspension is added in step D. The oxidation, average particle size of abrasive particles, and pH value of the second polishing liquid are measured again, and the three values are 395.4 nA, 212 nm, and 7.9, respectively. All three values are greater than the preset values, and the SiC wafer can continue to be polished.

[0059] It should be noted that when the oxidation and the average particle size of abrasive particles are both less than the preset values, the potassium permanganate solution should be added first because it can be easily mixed uniformly with the filtered first polishing liquid, avoiding the influence of the subsequent addition of the alumina suspension on the oxidation adjustment effect due to the uneven system.

[0060] Polishing test: a new batch of SiC wafers (the 5th batch of workpieces polished by the second polishing liquid) is polished under the same conditions using the second polishing liquid. After polishing, the material removal rate and the surface roughness of the SiC wafer are measured to be 1306 nm / h and 0.12 nm, respectively.

[0061] Example 4 The newly prepared polishing liquid was used to polish multiple batches of SiC wafers. When the fourth batch of workpieces was polished, the three indicators of the polishing liquid were measured, and the three indicators were 336.8 nA, 181 nm, and 7.8, respectively. At this time, the corresponding material removal rate and the surface roughness of the SiC wafer were 1048 nm / h and 0.14 nm, respectively.

[0062] The oxidation of the polishing liquid and the average particle size of the abrasive particles were both lower than the preset values, and it was determined that the polishing liquid was invalid. The polishing liquid was compensated.

[0063] After step A (filtering the invalid polishing liquid), 1 / 3 of the mass of potassium permanganate solution was added to the invalid polishing liquid filtered in step A in step B (adding potassium permanganate solution to the invalid polishing liquid filtered in step A), and then step C (filtering the invalid polishing liquid after adding the potassium permanganate solution) was performed. Finally, step D (adding alumina suspension to the invalid polishing liquid filtered in step C) was performed, and 1 / 3 of the mass of alumina suspension was added in step D. The oxidation of the second polishing liquid, the average particle size of the abrasive particles, and the pH value were measured again, and the three indicators were 431.7 nA, 241 nm, and 7.9, respectively. All of them are greater than the preset values, and the SiC wafers can continue to be polished.

[0064] Polishing test: a new batch of SiC wafers (the fifth batch of workpieces polished by the second polishing liquid) was polished under the same conditions using the second polishing liquid. After polishing, the material removal rate and the surface roughness of the SiC wafer were 1563 nm / h and 0.1 nm, respectively.

[0065] Example 5 The newly prepared polishing liquid was used to polish multiple batches of SiC wafers. When the fifth batch of workpieces was polished, the three indicators of the polishing liquid were measured, and the three indicators were 301.6 nA, 168 nm, and 7.3, respectively. At this time, the corresponding material removal rate and the surface roughness of the SiC wafer were 942 nm / h and 0.15 nm, respectively.

[0066] The oxidation of the polishing liquid, the average particle size of the abrasive particles, and the pH value were all lower than the preset values, and it was determined that the polishing liquid was invalid. The polishing liquid was compensated.

[0067] After Step A (filtering the spent polishing liquid), Step B (adding potassium permanganate solution to the filtered spent polishing liquid of Step A) is performed, in which 1 / 3 of the mass of the potassium permanganate solution is added, followed by Step C (filtering the spent polishing liquid after the addition of the potassium permanganate solution), followed by Step D (adding alumina suspension to the filtered spent polishing liquid of Step C), in which 1 / 3 of the mass of the alumina suspension is added, followed by Step E (filtering the spent polishing liquid after the addition of the potassium permanganate solution and the alumina suspension), and finally Step F (adding acid-base regulator to the filtered spent polishing liquid of Step E), in which 5% of the mass of the acid-base regulator is added. The oxidation, the average abrasive particle size, and the pH value of the second polishing liquid are measured again to be 399.7 nA, 227 nm, and 7.7, respectively. All of them are greater than the preset values, and the SiC wafer can be polished continuously.

[0068] It should be noted that when the oxidation and the pH value are less than the preset values, or the average abrasive particle size and the pH value are less than the preset values, or the oxidation, the average abrasive particle size, and the pH value are less than the preset values, the acid-base regulator is added last in the compensation process.

[0069] Polishing test: A new batch of SiC wafers (the 6th batch of workpieces polished by the polishing liquid) is polished by the second polishing liquid under the same conditions. After polishing, the material removal rate and the surface roughness of the SiC wafer are measured to be 1341 nm / h and 0.12 nm, respectively.

[0070] Comparative Example 1 A newly prepared polishing liquid is used to polish multiple batches of SiC wafers. After polishing the 4th batch of workpieces, the material removal rate and the surface roughness of the SiC wafer corresponding to this polishing are measured to be 1048 nm / h and 0.14 nm, respectively.

[0071] Comparative Example 2 A newly prepared polishing liquid is used to polish multiple batches of SiC wafers. After polishing the 5th batch of workpieces, the material removal rate and the surface roughness of the SiC wafer corresponding to this polishing are measured to be 942 nm / h and 0.15 nm, respectively.

[0072] Comparative Example 3 A newly prepared polishing liquid is used to polish multiple batches of SiC wafers. After polishing the 6th batch of workpieces, the material removal rate and the surface roughness of the SiC wafer corresponding to this polishing are measured to be 836 nm / h and 0.17 nm, respectively.

[0073] The material removal rates and the surface roughnesses of the SiC wafers obtained in Examples 1, 2, 3, 4, and 5 are made into Table 1.

[0074] The material removal rate and SiC wafer surface roughness of the materials obtained in Comparative Examples 1, 2 and 3 are shown in Table 2.

[0075] Table 1 Material removal rate and SiC wafer surface roughness obtained in each example

[0076] Table 2 Material removal rate and SiC wafer surface roughness obtained in each comparative example

[0077] In summary, the failure evaluation method and compensation method of the polishing liquid proposed in the present application can restore the polishing performance of the failed polishing liquid to a level that can continue to be used. This method can effectively reduce the replacement frequency of the polishing liquid, reduce the economic consumption of the CMP of the SiC wafer, and effectively reduce the generation of waste liquid, thereby effectively promoting the landing of the circular economy and green chemistry goals.

[0078] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for evaluating failure of a CMP polishing liquid, characterized in that: The steps include: Step 1: After polishing a batch of workpieces with the polishing liquid for a period of time, the oxidizing property, average abrasive particle size, and pH value of the polishing liquid are measured; Step 2: Determine whether the oxidizability, average abrasive particle size, and pH value of the polishing liquid are all greater than preset values; Step 3: If the measured oxidizability, average abrasive particle size, and pH value are all greater than the preset values, continue polishing the next batch of workpieces using the polishing liquid; Step 4: If the measured oxidizability and / or average abrasive particle size and / or pH value are less than the preset value, the polishing liquid is deemed to be invalid and cannot be used for polishing. The invalid polishing liquid can be compensated before it can be used to polish the workpiece.

2. The failure evaluation method of CMP polishing liquid according to claim 1, characterized in that: In the step 1, the oxidizing property of the polishing liquid is measured by a redox titration method or an electrochemical method.

3. The failure evaluation method of CMP polishing liquid according to claim 1, characterized in that: In the step 1, the average particle size of the abrasive particles in the polishing liquid is measured by laser particle size analysis or scanning electron microscopy.

4. The failure evaluation method of CMP polishing liquid according to claim 1, characterized in that: In step 1, a pH meter or a pH indicator is used to measure the pH value of the polishing liquid.

5. The failure evaluation method of CMP polishing liquid according to claim 1, characterized in that: In step 2, the method for determining the preset value includes: determining the preset value based on the corresponding relationship between the material removal rate and surface roughness of each batch of workpieces processed by the polishing liquid and the oxidizability, average particle size of the abrasive particles and the pH value; Among them, when the material removal rate does not meet the requirements or the surface roughness of the workpiece does not meet the requirements after a certain processing, it can be considered that the oxidizing property, average particle size of the abrasive and pH value of the polishing liquid corresponding to the processing before this processing are the required preset values.

6. A compensation method for compensating for the spent polishing liquid in the failure evaluation method for CMP polishing liquid according to claim 1, characterized in that: The steps include: S1, filtering the spent polishing liquid to obtain a first polishing liquid; S2. Adding a certain amount of potassium permanganate solution and / or aluminum oxide suspension and / or acid-base regulator to the first polishing liquid to obtain a second polishing liquid; S21. When the oxidizing property of the spent polishing liquid is lower than a preset value, adding a certain mass of potassium permanganate solution to the first polishing liquid; S22, when the average particle size of the abrasive particles of the spent polishing slurry is lower than a preset value, adding a certain mass of aluminum oxide suspension to the first polishing slurry; S23, when the pH value of the spent polishing liquid is lower than a preset value, adding a certain mass of acid-base regulator to the first polishing liquid; S3, measuring the oxidizability, average abrasive particle size and pH value of the second polishing liquid; if the measured oxidizability, average abrasive particle size and pH value are all greater than the preset values, the second polishing liquid can continue to be used for polishing the workpiece; if the measured oxidizability and / or average abrasive particle size and / or pH value are less than the preset values, repeat S1 to S3 until the oxidizability, average abrasive particle size and pH value are all greater than the preset values.

7. The compensation method according to claim 6, characterized in that: In the S2, the mass of the added potassium permanganate solution and the aluminum oxide suspension is 1 / 5-1 / 3 of the mass of the original invalid polishing liquid, and the mass of the added acid-base regulator is 1%-5% of the mass of the original invalid polishing liquid.

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