Wafer cleaning method

Abstract

The invention discloses a wafer cleaning method, comprising the following steps: performing chemical mechanical polishing on a wafer; performing a first pre-cleaning on the wafer; performing a second pre-cleaning on the wafer; taking out the wafer after the second pre-cleaning, and performing post-cleaning on the wafer. In the wafer cleaning method of the invention, after the CMP process, the grinding head and the grinding pad continue to rotate, and the first alkaline cleaning solution and the second alkaline cleaning solution are sequentially used to clean the wafer. Since the pH of the first alkaline cleaning solution is similar to the pH of the alkaline grinding solution, it is possible to avoid a significant change in the pH value of the wafer surface, and avoid affecting the dynamic balance of silicate, so that most of the pollutants can be washed away, reducing the probability of pollutants adhering to the wafer surface with higher activity after CMP, and the second alkaline cleaning solution with a higher pH cleans the wafer again, so that the removal of pollutants on the wafer surface can be achieved better.

Description

Technical Field

[0001] The invention relates to the field of semiconductor manufacturing and is a wafer cleaning method. Background Art

[0002] Chemical Mechanical Polishing (CMP), also known as chemical mechanical grinding, is one of the key technologies in wafer manufacturing and processing. It is widely used in surface flattening processing at various stages of wafer manufacturing and processing. As electronic products develop towards lightweight, miniaturization, and high speed, the chip manufacturing process precision is also getting higher and higher, which puts higher requirements on chip manufacturing. Cleaning the wafer surface after CMP is a very important step in the manufacturing process. Whether the cleaning is clean directly affects the performance, reliability and stability of electronic devices.

[0003] The principle of CMP is that in the alkaline polishing liquid, the Si on the surface of the wafer is oxidized by hydroxide ions (OH - ) after corrosion to generate silicate ions (SiO3 2- ), SiO3 2- The dynamic equilibrium formed during the hydrolysis process enables the product silicic acid (H2SiO3) to partially polymerize into polysilicic acid particles to form a colloid. This dynamic equilibrium process is significantly affected by the pH value.

[0004] The traditional cleaning method is generally to rinse the wafer with deionized water after the CMP process, and then immerse it in an ammonia cleaning tank and a hydrofluoric acid cleaning tank for cleaning. Since the surface activity of the wafer is high after CMP, the wafer surface is easy to absorb abrasive micropowder particles, organic matter, metal ions and other pollutants in the alkaline polishing liquid. In the process of rinsing the wafer with deionized water, the pH value changes significantly. Since there are still a lot of pollutants at this time, some pollutants are firmly adhered to the wafer, forming defects that are difficult to remove. Summary of the invention

[0005] Based on this, it is necessary to provide a wafer cleaning method that can solve the above problems.

[0006] A wafer cleaning method comprises the following steps:

[0007] A CMP device and a wafer are provided, wherein the CMP device comprises a polishing pad, a polishing head, an alkaline polishing liquid component, a first cleaning component and a second cleaning component;

[0008] The grinding head fixes the wafer and presses the wafer down to the peripheral area of ​​the grinding pad, the alkaline grinding liquid assembly adds alkaline grinding liquid to the peripheral area of ​​the grinding pad, and the grinding head and the grinding pad rotate respectively to perform chemical mechanical polishing on the wafer;

[0009] After the wafer completes the chemical mechanical polishing, the alkaline polishing liquid component stops adding alkaline polishing liquid to the peripheral area of ​​the polishing pad, the polishing head and the polishing pad continue to rotate, and at the same time, the first cleaning component adds a first alkaline cleaning liquid to the peripheral area of ​​the polishing pad to perform a first pre-cleaning on the wafer, wherein the difference between the pH of the first alkaline cleaning liquid and the pH of the alkaline polishing liquid is -1 to 1;

[0010] After the wafer completes the first pre-cleaning, the first cleaning component stops adding the first alkaline cleaning solution to the peripheral area of ​​the polishing pad, the polishing head and the polishing pad continue to rotate, and the second cleaning component adds a second alkaline cleaning solution to the peripheral area of ​​the polishing pad to perform a second pre-cleaning on the wafer, wherein the pH of the second alkaline cleaning solution is greater than the pH of the first alkaline cleaning solution; and

[0011] The wafer after the second pre-cleaning is taken out, and the wafer is post-cleaned.

[0012] In one embodiment, the grinding head and the grinding pad continue to rotate, and at the same time the first cleaning component adds a first alkaline cleaning solution to the peripheral area of ​​the grinding pad. During the pre-cleaning operation of the wafer, the rotation speed of the grinding head is 80rpm~150rpm, the rotation speed of the grinding pad is 50rpm~100rpm, and the time of the first pre-cleaning is 20s~40s.

[0013] In one embodiment, the grinding head and the grinding pad continue to rotate, and at the same time the second cleaning component adds the second alkaline cleaning solution to the peripheral area of ​​the grinding pad. During the second pre-cleaning operation of the wafer, the rotation speed of the grinding head is 80rpm~150rpm, the rotation speed of the grinding pad is 50rpm~100rpm, the time of the second pre-cleaning is 20s~40s, and the sum of the first pre-cleaning time and the second pre-cleaning time does not exceed 70s.

[0014] In one embodiment, the CMP apparatus further comprises a third cleaning assembly;

[0015] The wafer cleaning method further includes performing the following operations after performing a second pre-cleaning operation on the wafer and before taking out the wafer after the second pre-cleaning operation:

[0016] After the wafer completes the second pre-cleaning, the second cleaning component stops adding the second alkaline cleaning solution to the peripheral area of ​​the grinding pad, the grinding head and the grinding pad continue to rotate, and at the same time the third cleaning component adds deionized water to the peripheral area of ​​the grinding pad to perform a third pre-cleaning on the wafer, wherein the rotation speed of the grinding head is 80rpm~150rpm, the rotation speed of the grinding pad is 50rpm~100rpm, and the time of the third pre-cleaning is 20s~40s.

[0017] In one embodiment, the operation of cleaning the wafer is: post-cleaning the wafer using an acidic cleaning solution and deionized water in sequence.

[0018] In one embodiment, the operation of post-cleaning the wafer with an acidic cleaning solution and deionized water in sequence is: after rinsing the wafer with the acidic cleaning solution, rinsing the wafer with the deionized water, the time for rinsing the wafer with the acidic cleaning solution is 40s to 70s, and the time for rinsing the wafer with the deionized water is 30s to 60s, and the acidic cleaning solution is an HF solution with a concentration of 0.25wt% to 1wt%.

[0019] In one embodiment, the pH of the alkaline polishing liquid is 8-10, and the pH of the first alkaline cleaning liquid is 7.5-10.5.

[0020] In one embodiment, the solute of the first alkaline cleaning solution includes NH3·H2O and NH4Cl, and the concentration of NH3·H2O in the first alkaline cleaning solution is 0.04 wt% to 0.1 wt%.

[0021] In one embodiment, the solute of the second alkaline cleaning solution includes NH 3 ·H 2 O, and the concentration of NH 3 ·H 2 O in the second alkaline cleaning solution is 0.08 wt % to 0.12 wt %.

[0022] In one embodiment, the solute of the first alkaline cleaning solution further includes an anionic surfactant, and the concentration of the anionic surfactant is 0.2wt% to 1wt%;

[0023] The solute of the second alkaline cleaning solution further includes a metal ion chelating agent, and the concentration of the metal ion chelating agent is 0.1 wt % to 0.6 wt %.

[0024] According to the wafer cleaning method of the present invention, after the CMP process, the grinding head and the grinding pad continue to rotate, and the first alkaline cleaning solution and the second alkaline cleaning solution are used in sequence to clean the wafer. Since the pH of the first alkaline cleaning solution is similar to that of the alkaline grinding solution, it is possible to avoid a significant change in the pH value of the wafer surface, and avoid affecting the dynamic balance of silicate, so that most of the pollutants can be washed away, and the probability of the pollutants adhering to the wafer surface with higher activity after CMP is reduced. After most of the pollutants are washed away, the second alkaline cleaning solution with a higher pH is used to clean the wafer again, so that the pollutants on the wafer surface can be better removed. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] in:

[0027] Figure 1 The present invention is a flow chart of a wafer cleaning method according to one embodiment.

[0028] Figure 2 It is a schematic side view of the structure of a CMP device according to one embodiment.

[0029] Figure 3 For Figure 1 The schematic diagram of the top view of the CMP equipment is shown. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Combination Figure 1 The present invention discloses a wafer cleaning method according to an embodiment of the present invention, comprising the following steps:

[0032] S10 . Provide CMP equipment and wafer 200 .

[0033] Combination Figure 2 and Figure 3 In this embodiment, the CMP device includes a polishing pad 10, a polishing head 20, an alkaline polishing liquid component 30, a first cleaning component 40 and a second cleaning component 50.

[0034] In this embodiment, the wafer 200 is a silicon wafer.

[0035] The wafer 200 may be 4 inches, 6 inches, 8 inches, 12 inches, etc.

[0036] It should be noted that, in this embodiment, only one grinding head 20 is provided. In other embodiments, the number of the grinding heads 20 may also be 2, 3, 4, etc.

[0037] The first cleaning assembly 40 and the second cleaning assembly 50 have substantially the same structure, and both include a liquid storage tank, a pressure pump, a pipe, and a nozzle.

[0038] S20, the grinding head 20 fixes the wafer 200 and presses the wafer 200 down to the outer area of ​​the grinding pad 10, the alkaline grinding liquid assembly 30 adds alkaline grinding liquid to the outer area of ​​the grinding pad 10, and the grinding head 20 and the grinding pad 10 rotate respectively to perform chemical mechanical polishing on the wafer 200.

[0039] In this embodiment, the wafer 200 is subjected to chemical mechanical polishing using a conventional process, and different types of alkaline polishing fluids are selected according to the actual process. The rotation speeds of the polishing head 20 and the polishing pad 10 are also set according to the actual process.

[0040] Specifically, in S20 , the grinding head 20 and the grinding pad 10 both rotate clockwise, and their rotation speeds are different.

[0041] S30, after the wafer 200 completes chemical mechanical polishing, the alkaline polishing liquid component 30 stops adding alkaline polishing liquid to the peripheral area of ​​the polishing pad 10, the polishing head 20 and the polishing pad 10 continue to rotate, and at the same time the first cleaning component 40 adds the first alkaline cleaning liquid to the peripheral area of ​​the polishing pad 10 to perform the first pre-cleaning of the wafer 200.

[0042] The difference between the pH of the first alkaline cleaning solution and the pH of the alkaline polishing solution is -1 to 1.

[0043] Preferably, the pH of the alkaline polishing liquid is 8-10, and the pH of the first alkaline cleaning liquid is 7.5-10.5.

[0044] More preferably, the difference between the pH of the first alkaline cleaning solution and the pH of the alkaline polishing solution is 0 to 0.5.

[0045] Since the pH of the first alkaline cleaning solution is similar to that of the alkaline polishing solution, significant changes in the pH value on the surface of the wafer 200 can be avoided, thereby avoiding affecting the dynamic balance of silicate, thereby washing away most of the contaminants and reducing the probability of contaminants adhering to the surface of the wafer 200 which is more active after CMP.

[0046] Particularly preferably, in this embodiment, the solutes of the first alkaline cleaning solution are NH3·H2O and NH4Cl, and the concentration of NH3·H2O in the first alkaline cleaning solution is 0.04wt% to 0.1wt%.

[0047] NH4Cl can not only adjust the pH, but also provide Cl ions to accelerate the transformation of silicic acid into polysilicate colloidal particles, thus achieving better cleaning effects.

[0048] Specifically, in this embodiment, the solute of the first alkaline cleaning solution further includes an anionic surfactant, and the concentration of the anionic surfactant is 0.2 wt % to 1 wt %.

[0049] The anionic surfactant can be selected according to actual needs, for example, it can be sodium alkylbenzene sulfonate, sodium alkyl sulfonate, etc.

[0050] Specifically, in this embodiment, the preparation process of the first alkaline cleaning solution is as follows: prepare a mixed solution of 0.04wt% to 0.1wt% ammonia water (obtained by diluting concentrated ammonia water) and 0.2wt% to 1wt% anionic surfactant, and then add NH4Cl solution (the concentration can be 1mol / L to 5mol / L) to the mixed solution until the pH is 7.5 to 10.5.

[0051] Specifically, in S30 , the rotation speed of the polishing head 20 is 80 rpm to 150 rpm, the rotation speed of the polishing pad 10 is 50 rpm to 100 rpm, and the time of the first pre-cleaning is 20 s to 40 s.

[0052] Specifically, in S30 , the polishing head 20 and the polishing pad 10 both rotate clockwise, and their rotation speeds are different.

[0053] S40, after the wafer 200 completes the first pre-cleaning, the first cleaning component 40 stops adding the first alkaline cleaning liquid to the peripheral area of ​​the grinding pad 10, the grinding head 20 and the grinding pad 10 continue to rotate, and at the same time the second cleaning component 50 adds the second alkaline cleaning liquid to the peripheral area of ​​the grinding pad 10 to perform a second pre-cleaning on the wafer 200.

[0054] The pH of the second alkaline cleaning solution is greater than the pH of the first alkaline cleaning solution.

[0055] Preferably, the second alkaline cleaning solution is aqueous ammonia with a concentration of 0.08 wt % to 0.12 wt %.

[0056] The second alkaline cleaning solution with a higher pH value is used to clean the wafer again, thereby better removing pollutants on the wafer surface.

[0057] In addition, the second alkaline cleaning solution is ammonia water with a concentration of 0.08wt% to 0.12wt%, so that the composition of the second alkaline cleaning solution is similar to that of the first alkaline cleaning solution, thereby preventing contaminants from attaching to the wafer surface due to a significant change in ions.

[0058] More preferably, the solute of the second alkaline cleaning solution further includes a metal ion chelating agent, and the concentration of the metal ion chelating agent is 0.1 wt % to 0.6 wt %.

[0059] The metal ion chelating agent can be selected according to actual needs, for example, it can be EDTA, NTA, DPTA, etc.

[0060] Preferably, in S40, the rotation speed of the grinding head 20 is 80 rpm to 150 rpm, the rotation speed of the grinding pad 10 is 50 rpm to 100 rpm, the second pre-cleaning time is 20 s to 40 s, and the sum of the first pre-cleaning time and the second pre-cleaning time does not exceed 70 s.

[0061] In conjunction with the drawings, the CMP apparatus further includes a third cleaning component 60 .

[0062] The wafer 200 cleaning method of this embodiment further includes the following operations after S40 and before S50: after the wafer 200 completes the second pre-cleaning, the second cleaning component 50 stops adding the second alkaline cleaning solution to the peripheral area of ​​the polishing pad 10, the polishing head 20 and the polishing pad 10 continue to rotate, and the third cleaning component 60 adds deionized water to the peripheral area of ​​the polishing pad 10 to perform a third pre-cleaning on the wafer 200. The rotation speed of the polishing head 20 is 80 rpm to 150 rpm, the rotation speed of the polishing pad 10 is 50 rpm to 100 rpm, and the time of the third pre-cleaning is 20s to 40s.

[0063] Specifically, in S40 , the polishing head 20 and the polishing pad 10 both rotate clockwise, and their rotation speeds are different.

[0064] The third cleaning assembly 60 and the first cleaning assembly 40 have substantially the same structure, both including a liquid storage tank, a pressure pump, a pipe and a nozzle.

[0065] S50 , taking out the wafer 200 after the second pre-cleaning, and performing post-cleaning on the wafer 200 .

[0066] Specifically, in S50 , the operation of cleaning the wafer 200 is: using an acid cleaning solution and deionized water to post-clean the wafer 200 in sequence.

[0067] Preferably, the acid cleaning solution is an HF solution with a concentration of 0.25 wt % to 1 wt %.

[0068] HF solution can effectively remove metal contaminants generated during the CMP process.

[0069] In this embodiment, the operation of post-cleaning the wafer 200 with an acidic cleaning solution and deionized water in sequence is as follows: after rinsing the wafer 200 with the acidic cleaning solution, the wafer 200 is then rinsed with deionized water. The acidic cleaning solution rinses the wafer 200 for 40s to 70s, and the deionized water rinses the wafer 200 for 30s to 60s.

[0070] Specifically, when the wafer 200 is rinsed with an acidic cleaning liquid (or deionized water), the wafer 200 can be placed on a rotating platform. While the wafer 200 rotates, the nozzle of the acidic cleaning liquid (or deionized water) moves along the diameter direction of the wafer 200 and sprays the acidic cleaning liquid (or deionized water).

[0071] Preferably, the wafer 200 cleaning method of the present embodiment further includes, after performing a post-cleaning operation on the wafer 200 , performing the following operation: drying the wafer 200 .

[0072] The wafer 200 may be dried using conventional methods in the art.

[0073] Specifically, in this embodiment, the wafer 200 placed on the rotating platform can be driven by the rotating platform to rotate at a high speed to achieve drying.

[0074] In the wafer cleaning method of this embodiment, after the CMP process, the grinding head 20 and the grinding pad 10 continue to rotate, and the first alkaline cleaning solution and the second alkaline cleaning solution are used to clean the wafer 200 in turn. Since the pH of the first alkaline cleaning solution is similar to the pH of the alkaline grinding solution, the pH value on the surface of the wafer 200 can be avoided from changing significantly, and the dynamic balance of silicate can be avoided from being affected, so that most of the contaminants can be washed away, and the probability of contaminants adhering to the surface of the wafer 200 with higher activity after CMP is reduced. After most of the contaminants are washed away, the second alkaline cleaning solution with a higher pH is used to clean the wafer 200 again, so that the contaminants on the wafer surface can be better removed.

[0075] In addition, the CMP equipment used in the wafer cleaning method of this embodiment can be simply modified on the basis of the traditional CMP equipment by adding several cleaning components. It is simple and easy to operate and has high practicality.

[0076] The following are specific embodiments.

[0077] Example 1

[0078] A CMP device is provided, which includes a grinding pad, a grinding head, an alkaline grinding liquid component, a first cleaning component, a second cleaning component and a third cleaning component. A mixed solution of 0.08wt% ammonia water and 0.25wt% sodium dodecyl sulfate is prepared, and then a 2.5mol / L NH4Cl solution is added to the mixed solution until the pH is 9 to obtain a first alkaline cleaning solution. A mixed solution of 0.1wt% ammonia water and 0.15wt% EDTA is prepared as a second alkaline cleaning solution. A 0.5wt% HF solution is prepared as an acidic cleaning solution. As required, the grinding slurry (purchased from Fujifilm, model FSL1531C) is diluted to obtain an alkaline grinding liquid with a pH of 9.

[0079] The grinding head fixes a 6-inch wafer with a silicon nitride layer and presses the wafer down to the peripheral area of ​​the grinding pad. According to the set program, the alkaline grinding liquid assembly adds alkaline grinding liquid to the peripheral area of ​​the grinding pad. The grinding head and the grinding pad rotate separately to perform chemical mechanical polishing on the wafer.

[0080] After the wafer completes chemical mechanical polishing, the alkaline polishing liquid component stops adding alkaline polishing liquid to the peripheral area of ​​the polishing pad, the polishing head and the polishing pad continue to rotate, and the first cleaning component adds the first alkaline cleaning liquid to the peripheral area of ​​the polishing pad to perform the first pre-cleaning on the 6-inch wafer. During the first pre-cleaning process, the rotation speed of the polishing head is 120rpm, the rotation speed of the polishing pad is 80rpm, and the time of the first pre-cleaning is 30s.

[0081] After the 6-inch wafer completes the first pre-cleaning, the first cleaning component stops adding the first alkaline cleaning liquid to the peripheral area of ​​the grinding pad, the grinding head and the grinding pad 10 continue to rotate, and the second cleaning component 50 adds the second alkaline cleaning liquid to the peripheral area of ​​the grinding pad 10 to perform a second pre-cleaning on the 6-inch wafer. During the second pre-cleaning process, the rotation speed of the grinding head is 120 rpm, the rotation speed of the grinding pad is 80 rpm, and the time of the second pre-cleaning is 30 seconds.

[0082] After the 6-inch wafer completes the second pre-cleaning, the second cleaning component stops adding the second alkaline cleaning solution to the peripheral area of ​​the polishing pad, the polishing head and the polishing pad continue to rotate, and the third cleaning component adds deionized water to the peripheral area of ​​the polishing pad to perform the third pre-cleaning on the 6-inch wafer. During the third pre-cleaning process, the rotation speed of the polishing head is 120rpm, the rotation speed of the polishing pad is 80rpm, and the time of the third pre-cleaning is 30s.

[0083] After the 6-inch wafer completes the third pre-cleaning, the 6-inch wafer is placed on a turntable, the turntable speed is controlled to 100 rpm, the 6-inch wafer is rinsed with an acid cleaning solution for 60 seconds, and then rinsed with deionized water for 45 seconds. Finally, the turntable speed is controlled to 2000 rpm to spin dry the 6-inch wafer.

[0084] Comparative Example 1

[0085] A CMP device is provided, the CMP device includes a grinding pad, a grinding head, an alkaline grinding liquid component, a first cleaning component, a second cleaning component and a third cleaning component. Ammonia water with a concentration of 0.1wt% is prepared as the second alkaline cleaning liquid. An HF solution with a concentration of 0.5wt% is prepared as the acidic cleaning liquid. According to the requirements, the grinding slurry (purchased from Fujifilm, model FSL1531C) is diluted to obtain an alkaline grinding liquid with a pH of 9.

[0086] The grinding head fixes a 6-inch wafer with a silicon nitride layer and presses the wafer down to the peripheral area of ​​the grinding pad. According to the set program, the alkaline grinding liquid assembly adds alkaline grinding liquid to the peripheral area of ​​the grinding pad. The grinding head and the grinding pad rotate separately to perform chemical mechanical polishing on the wafer.

[0087] After the wafer completes chemical mechanical polishing, the alkaline polishing liquid assembly stops adding alkaline polishing liquid to the peripheral area of ​​the polishing pad, the polishing head and the polishing pad continue to rotate, and at the same time, the second cleaning assembly 50 adds the second alkaline cleaning liquid to the peripheral area of ​​the polishing pad 10 to pre-clean the 6-inch wafer. The rotation speed of the polishing head is 120 rpm, the rotation speed of the polishing pad is 80 rpm, and the pre-cleaning time is 30 seconds.

[0088] After the 6-inch wafer is pre-cleaned, the second cleaning component stops adding the second alkaline cleaning solution to the peripheral area of ​​the polishing pad, the polishing head and the polishing pad continue to rotate, and the third cleaning component adds deionized water to the peripheral area of ​​the polishing pad to pre-clean the 6-inch wafer again. The rotation speed of the polishing head is 120 rpm, the rotation speed of the polishing pad is 80 rpm, and the pre-cleaning time is 30 seconds.

[0089] After the 6-inch wafer is pre-cleaned again, the 6-inch wafer is placed on a turntable, the turntable speed is controlled to 100 rpm, the 6-inch wafer is rinsed with an acid cleaning solution for 60 seconds, and then rinsed with deionized water for 45 seconds. Finally, the turntable speed is controlled to 2000 rpm to spin dry the 6-inch wafer.

[0090] Comparative Example 2

[0091] A CMP device is provided, the CMP device includes a grinding pad, a grinding head, an alkaline grinding liquid component, a first cleaning component, a second cleaning component and a third cleaning component. Ammonia water with a concentration of 0.1wt% is prepared as the second alkaline cleaning liquid. An HF solution with a concentration of 0.5wt% is prepared as the acidic cleaning liquid. According to the requirements, the grinding slurry (purchased from Fujifilm, model FSL1531C) is diluted to obtain an alkaline grinding liquid with a pH of 9.

[0092] The grinding head fixes a 6-inch wafer with a silicon nitride layer and presses the wafer down to the peripheral area of ​​the grinding pad. According to the set program, the alkaline grinding liquid assembly adds alkaline grinding liquid to the peripheral area of ​​the grinding pad. The grinding head and the grinding pad rotate separately to perform chemical mechanical polishing on the wafer.

[0093] After the wafer completes chemical mechanical polishing, the alkaline polishing liquid component stops adding alkaline polishing liquid to the peripheral area of ​​the polishing pad, the polishing head and the polishing pad continue to rotate, and the third cleaning component adds deionized water to the peripheral area of ​​the polishing pad to pre-clean the 6-inch wafer. The rotation speed of the polishing head is 120rpm, the rotation speed of the polishing pad is 80rpm, and the pre-cleaning time is 60s.

[0094] After the 6-inch wafer is pre-cleaned, the 6-inch wafer is placed on a turntable, the turntable speed is controlled to 100 rpm, the 6-inch wafer is rinsed with the second alkaline cleaning solution for 60 seconds, the 6-inch wafer is rinsed with deionized water for 30 seconds, then the 6-inch wafer is rinsed with an acidic cleaning solution for 60 seconds, then the 6-inch wafer is rinsed with deionized water for 45 seconds, and finally the turntable speed is controlled to 2000 rpm to spin dry the 6-inch wafer.

[0095] Test Case

[0096] 100 6-inch wafers were cleaned using the methods in Example 1, Comparative Example 1 and Comparative Example 2, respectively. After cleaning, the cleaned 6-inch wafers obtained in Example 1, Comparative Example 1 and Comparative Example 2 were inspected using an automatic optical inspection system, and the inspection results were averaged to obtain the following Table 1.

[0097] Table 1

[0098] Example 1 Comparative Example 1 Comparative Example 2 Number of defects at 1μm 8.12 13.53 32.44

[0099] It can be seen from Table 1 that the 6-inch wafer surface has fewer defects after cleaning by the method in Example 1.

[0100] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A wafer cleaning method, characterized in that: The steps include: A CMP device and a wafer are provided, wherein the CMP device comprises a polishing pad, a polishing head, an alkaline polishing liquid component, a first cleaning component and a second cleaning component; The grinding head fixes the wafer and presses the wafer down to the peripheral area of ​​the grinding pad, the alkaline grinding liquid assembly adds alkaline grinding liquid to the peripheral area of ​​the grinding pad, and the grinding head and the grinding pad rotate respectively to perform chemical mechanical polishing on the wafer; After the wafer completes the chemical mechanical polishing, the alkaline polishing liquid component stops adding alkaline polishing liquid to the peripheral area of ​​the polishing pad, the polishing head and the polishing pad continue to rotate, and at the same time the first cleaning component adds a first alkaline cleaning liquid to the peripheral area of ​​the polishing pad to perform a first pre-cleaning on the wafer, wherein the pH of the alkaline polishing liquid is 8-10, the pH of the first alkaline cleaning liquid is 7.5-10.5, the difference between the pH of the first alkaline cleaning liquid and the pH of the alkaline polishing liquid is 0-0.5, the solutes of the first alkaline cleaning liquid are NH3·H2O and NH4Cl, and the concentration of NH3·H2O in the first alkaline cleaning liquid is 0.04wt%-0.1wt%; After the wafer completes the first pre-cleaning, the first cleaning component stops adding the first alkaline cleaning solution to the peripheral area of ​​the polishing pad, the polishing head and the polishing pad continue to rotate, and the second cleaning component adds a second alkaline cleaning solution to the peripheral area of ​​the polishing pad to perform a second pre-cleaning on the wafer, wherein the pH of the second alkaline cleaning solution is greater than the pH of the first alkaline cleaning solution, and the second alkaline cleaning solution is ammonia water with a concentration of 0.08wt% to 0.12wt%; and The wafer after the second pre-cleaning is taken out, and the wafer is post-cleaned.

2. The wafer cleaning method according to claim 1, characterized in that: The grinding head and the grinding pad continue to rotate, and at the same time the first cleaning component adds a first alkaline cleaning solution to the peripheral area of ​​the grinding pad. During the pre-cleaning operation of the wafer, the rotation speed of the grinding head is 80rpm~150rpm, the rotation speed of the grinding pad is 50rpm~100rpm, and the time of the first pre-cleaning is 20s~40s.

3. The wafer cleaning method according to claim 1, characterized in that: The grinding head and the grinding pad continue to rotate, and at the same time, the second cleaning component adds the second alkaline cleaning solution to the peripheral area of ​​the grinding pad. During the second pre-cleaning operation of the wafer, the rotation speed of the grinding head is 80rpm~150rpm, the rotation speed of the grinding pad is 50rpm~100rpm, the time of the second pre-cleaning is 20s~40s, and the sum of the first pre-cleaning time and the second pre-cleaning time does not exceed 70s.

4. The wafer cleaning method according to claim 1, characterized in that: The CMP apparatus further includes a third cleaning assembly; The wafer cleaning method further includes performing the following operations after performing a second pre-cleaning operation on the wafer and before taking out the wafer after the second pre-cleaning operation: After the wafer completes the second pre-cleaning, the second cleaning component stops adding the second alkaline cleaning solution to the peripheral area of ​​the grinding pad, the grinding head and the grinding pad continue to rotate, and at the same time the third cleaning component adds deionized water to the peripheral area of ​​the grinding pad to perform a third pre-cleaning on the wafer, wherein the rotation speed of the grinding head is 80rpm~150rpm, the rotation speed of the grinding pad is 50rpm~100rpm, and the time of the third pre-cleaning is 20s~40s.

5. The wafer cleaning method according to claim 1, characterized in that: The operation of cleaning the wafer is: using an acid cleaning solution and deionized water to post-clean the wafer in sequence.

6. The wafer cleaning method according to claim 5, characterized in that: The operation of post-cleaning the wafer using an acidic cleaning solution and deionized water in sequence is as follows: after rinsing the wafer with the acidic cleaning solution, the wafer is then rinsed with the deionized water, the time for rinsing the wafer with the acidic cleaning solution is 40s to 70s, the time for rinsing the wafer with the deionized water is 30s to 60s, and the acidic cleaning solution is an HF solution with a concentration of 0.25wt% to 1wt%.

7. The wafer cleaning method according to claim 1, characterized in that: The solute of the first alkaline cleaning solution also includes an anionic surfactant, and the concentration of the anionic surfactant is 0.2wt% to 1wt%; The solute of the second alkaline cleaning solution further includes a metal ion chelating agent, and the concentration of the metal ion chelating agent is 0.1 wt % to 0.6 wt %.

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