CN118315261B - Wafer cleaning method - Google Patents
Wafer cleaning method Download PDFInfo
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- CN118315261B CN118315261B CN202410338015.2A CN202410338015A CN118315261B CN 118315261 B CN118315261 B CN 118315261B CN 202410338015 A CN202410338015 A CN 202410338015A CN 118315261 B CN118315261 B CN 118315261B
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- 238000004140 cleaning Methods 0.000 title claims abstract description 240
- 238000000034 method Methods 0.000 title claims abstract description 46
- 238000005498 polishing Methods 0.000 claims abstract description 148
- 238000000227 grinding Methods 0.000 claims abstract description 69
- 239000000126 substance Substances 0.000 claims abstract description 8
- 239000007788 liquid Substances 0.000 claims description 59
- 230000002093 peripheral effect Effects 0.000 claims description 46
- 239000008367 deionised water Substances 0.000 claims description 27
- 229910021641 deionized water Inorganic materials 0.000 claims description 27
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 27
- 230000002378 acidificating effect Effects 0.000 claims description 18
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 9
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 9
- 239000003945 anionic surfactant Substances 0.000 claims description 8
- 229910021645 metal ion Inorganic materials 0.000 claims description 8
- 239000002738 chelating agent Substances 0.000 claims description 7
- 238000003825 pressing Methods 0.000 claims description 2
- 239000003344 environmental pollutant Substances 0.000 abstract description 12
- 231100000719 pollutant Toxicity 0.000 abstract description 12
- 230000000694 effects Effects 0.000 abstract description 6
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 abstract 1
- 235000012431 wafers Nutrition 0.000 description 130
- 239000000243 solution Substances 0.000 description 74
- 239000002253 acid Substances 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 8
- 238000004519 manufacturing process Methods 0.000 description 6
- 239000002002 slurry Substances 0.000 description 6
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 5
- 239000000356 contaminant Substances 0.000 description 5
- 238000011010 flushing procedure Methods 0.000 description 5
- 239000011259 mixed solution Substances 0.000 description 5
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 4
- 235000012239 silicon dioxide Nutrition 0.000 description 4
- 229910052581 Si3N4 Inorganic materials 0.000 description 3
- 235000010724 Wisteria floribunda Nutrition 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- -1 hydroxyl ions Chemical class 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 3
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 239000000084 colloidal system Substances 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000007689 inspection Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- WYMDDFRYORANCC-UHFFFAOYSA-N 2-[[3-[bis(carboxymethyl)amino]-2-hydroxypropyl]-(carboxymethyl)amino]acetic acid Chemical compound OC(=O)CN(CC(O)=O)CC(O)CN(CC(O)=O)CC(O)=O WYMDDFRYORANCC-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 229910020489 SiO3 Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- IJKVHSBPTUYDLN-UHFFFAOYSA-N dihydroxy(oxo)silane Chemical compound O[Si](O)=O IJKVHSBPTUYDLN-UHFFFAOYSA-N 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- DAJSVUQLFFJUSX-UHFFFAOYSA-M sodium;dodecane-1-sulfonate Chemical compound [Na+].CCCCCCCCCCCCS([O-])(=O)=O DAJSVUQLFFJUSX-UHFFFAOYSA-M 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02002—Preparing wafers
- H01L21/02005—Preparing bulk and homogeneous wafers
- H01L21/02008—Multistep processes
- H01L21/0201—Specific process step
- H01L21/02013—Grinding, lapping
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B37/00—Lapping machines or devices; Accessories
- B24B37/34—Accessories
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02041—Cleaning
- H01L21/02043—Cleaning before device manufacture, i.e. Begin-Of-Line process
- H01L21/02052—Wet cleaning only
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Mechanical Engineering (AREA)
- Mechanical Treatment Of Semiconductor (AREA)
- Cleaning Or Drying Semiconductors (AREA)
Abstract
本发明公开了一种晶圆清洗方法，包括如下步骤：对晶圆进行化学机械抛光；对晶圆进行第一次预清洗；对晶圆进行第二次预清洗；将第二次预清洗后的晶圆取出，并对晶圆进行后清洗。本发明的晶圆清洗方法在CMP工艺后，研磨头和研磨垫继续转动，并依次采用第一碱性清洗液和第二碱性清洗液对晶圆进行清洗，由于第一碱性清洗液的pH与碱性研磨液的pH相近，可以避免晶圆表面的pH值发生明显变化，避免对硅酸的动态平衡造成影响，从而可以从而实现将大部分污染物洗去，减少了污染物粘附在CMP后活性较高的晶圆表面的概率，pH更高的第二碱性清洗液再次对晶圆进行清洗，从而可以较好的实现晶圆表面污染物的去除。
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
The invention relates to the field of semiconductor manufacturing, in particular to a wafer cleaning method.
Background
Chemical Mechanical Polishing (CMP) is also called Chemical Mechanical Polishing (CMP), one of the key technologies for wafer fabrication, and is widely used in surface planarization at various stages in the wafer fabrication process. With the development of light weight, miniaturization and high speed of electronic products, the precision of chip manufacturing process is also higher and higher, which puts higher demands on chip manufacturing. The cleaning of the wafer surface after CMP is a very important step in the manufacturing process, and whether the cleaning is clean directly affects the performance, reliability and stability of the electronic device.
The principle of CMP is that in alkaline grinding fluid, si on the surface of a wafer is corroded by hydroxyl ions (OH -) to generate silicate ions (dynamic balance formed in the hydrolysis process of SiO 3 2-),SiO3 2- realizes that silicic acid (H 2SiO3) can be partially polymerized into polysilicic acid particles to form colloid, and the dynamic balance process is obviously influenced by pH value.
The conventional cleaning method is to rinse the wafer with deionized water after the CMP process, and then sequentially dip the wafer into an ammonia rinse tank and a hydrofluoric acid rinse tank for cleaning. Because the surface activity of the wafer after CMP is higher, the surface of the wafer is easy to adsorb pollutants such as abrasive micro powder particles, organic matters, metal ions and the like in alkaline grinding fluid, and the pH value is obviously changed in the process of flushing the wafer by deionized water.
Disclosure of Invention
Based on this, it is necessary to provide a wafer cleaning method that can solve the above-described problems.
A wafer cleaning method comprises the following steps:
Providing a CMP apparatus and a wafer, the CMP apparatus comprising a polishing pad, a polishing head, an alkaline polishing liquid component, a first cleaning component, and a second cleaning component;
The grinding head is used for fixing the wafer and pressing the wafer down to the peripheral area of the grinding pad, the alkaline grinding liquid component is used for adding 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 is polished chemically and mechanically, 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 meanwhile, the first cleaning component adds first alkaline cleaning liquid to the peripheral area of the polishing pad to perform first pre-cleaning on the wafer, wherein the difference between the pH value of the first alkaline cleaning liquid and the pH value of the alkaline polishing liquid is-1;
After the wafer is subjected to the first pre-cleaning, the first cleaning component stops adding the first alkaline cleaning solution to the peripheral area of the grinding pad, the grinding head and the grinding pad continue to rotate, and simultaneously the second cleaning component adds a second alkaline cleaning solution to the peripheral area of the grinding pad to perform the second pre-cleaning on the wafer, wherein the pH value of the second alkaline cleaning solution is greater than that of the first alkaline cleaning solution, and
And taking out the wafer after the second pre-cleaning, and carrying out post-cleaning on the wafer.
In one embodiment, the polishing head and the polishing pad continue to rotate, and the first cleaning component adds a first alkaline cleaning solution to the peripheral area of the polishing pad, so that the rotation speed of the polishing head is 80 rpm-150 rpm, the rotation speed of the polishing pad is 50 rpm-100 rpm, and the time for the first pre-cleaning is 20 s-40 s.
In one embodiment, the polishing head and the polishing pad continue to rotate, while the second cleaning component adds the second alkaline cleaning solution to the peripheral area of the polishing pad, and in the operation of performing the second pre-cleaning on the wafer, the rotation speed of the polishing head is 80rpm to 150rpm, the rotation speed of the polishing pad is 50rpm to 100rpm, the time of the second pre-cleaning is 20s to 40s, and the sum of the time of the first pre-cleaning and the time of the second pre-cleaning is not more than 70s.
In one embodiment, the CMP apparatus further comprises a third cleaning assembly;
the wafer cleaning method further comprises the following steps of after the operation of carrying out second pre-cleaning on the wafer, and before the operation of taking out the wafer after the second pre-cleaning:
After the wafer is subjected to the second pre-cleaning, the second cleaning component stops adding the second alkaline cleaning liquid to the peripheral area of the grinding pad, the grinding head and the grinding pad continue to rotate, meanwhile, the third cleaning component adds deionized water to the peripheral area of the grinding pad, and the wafer is subjected to the third pre-cleaning, wherein the rotating speed of the grinding head is 80-150 rpm, the rotating speed of the grinding pad is 50-100 rpm, and the time of the third pre-cleaning is 20-40 s.
In one embodiment, the wafer is cleaned by post-cleaning the wafer with an acidic cleaning solution and deionized water in sequence.
In one embodiment, the operation of sequentially adopting an acidic cleaning solution and deionized water to perform post-cleaning on the wafer comprises the steps of flushing the wafer with the acidic cleaning solution, flushing the wafer with the deionized water, wherein the time for flushing the wafer with the acidic cleaning solution is 40-70 s, the time for flushing the wafer with the deionized water is 30-60 s, and the acidic cleaning solution is an HF solution with the concentration of 0.25-1 wt%.
In one embodiment, the pH of the alkaline polishing solution is 8 to 10, and the pH of the first alkaline cleaning solution is 7.5 to 10.5.
In one embodiment, the solute of the first alkaline cleaning solution comprises NH 3·H2 O and NH 4 Cl, and the concentration of NH 3·H2 O in the first alkaline cleaning solution is 0.04wt% to 0.1wt%.
In one embodiment, the solute of the second alkaline cleaning solution comprises NH 3·H2 O, and the concentration of NH 3·H2 O in the second alkaline cleaning solution is 0.08wt% to 0.12wt%.
In one embodiment, the solute of the first alkaline cleaning solution further comprises an anionic surfactant, wherein the concentration of the anionic surfactant is 0.2wt% to 1wt%;
The solute of the second alkaline cleaning liquid further comprises a metal ion chelating agent, and the concentration of the metal ion chelating agent is 0.1-0.6 wt%.
According to the wafer cleaning method disclosed by the invention, after the CMP process, the grinding head and the grinding pad continue to rotate, and the first alkaline cleaning liquid and the second alkaline cleaning liquid are sequentially adopted to clean the wafer, as the pH value of the first alkaline cleaning liquid is similar to that of the alkaline grinding liquid, the obvious change of the pH value of the surface of the wafer can be avoided, and the influence on the dynamic balance of silicic acid is avoided, so that most pollutants can be washed off, the probability that the pollutants adhere to the surface of the wafer with higher activity after CMP is reduced, and after most pollutants are washed off, the second alkaline cleaning liquid with higher pH value cleans the wafer again, so that the removal of the pollutants on the surface of the wafer can be better realized.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Wherein:
FIG. 1 is a flow chart of a wafer cleaning method according to an embodiment.
Fig. 2 is a schematic side view of a CMP apparatus according to an embodiment.
Fig. 3 is a schematic top view of the CMP apparatus shown in fig. 1.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, the invention discloses a wafer cleaning method according to an embodiment, which includes the following steps:
s10, providing a CMP device and a wafer 200.
Referring to fig. 2 and 3, in the present embodiment, the CMP apparatus includes a polishing pad 10, a polishing head 20, an alkaline polishing liquid assembly 30, a first cleaning assembly 40, and a second cleaning assembly 50.
In this embodiment, the wafer 200 is a silicon wafer.
Wafer 200 may be 4 inches, 6 inches, 8 inches, 12 inches, etc.
Note that, in the present embodiment, only 1 polishing head 20 is provided. In other embodiments, the number of polishing heads 20 may be 2,3, 4, etc.
The first cleaning assembly 40 and the second cleaning assembly 50 are substantially identical in construction and each include a liquid reservoir, a pressure pump, a tube, and a nozzle.
S20, the polishing head 20 holds the wafer 200 and presses the wafer 200 down to the peripheral area of the polishing pad 10, the alkaline polishing liquid assembly 30 adds alkaline polishing liquid to the peripheral area of the polishing pad 10, and the polishing head 20 and the polishing pad 10 rotate respectively to perform chemical mechanical polishing on the wafer 200.
In this embodiment, the wafer 200 is chemically and mechanically polished by a conventional process, and different kinds of alkaline polishing solutions are selected according to the actual process, and the rotational speeds of the polishing head 20 and the polishing pad 10 are also set according to the actual process.
Specifically, in S20, the polishing head 20 and the polishing pad 10 are rotated clockwise, and the rotational speeds of the two are different.
S30, after the chemical mechanical polishing of the wafer 200 is completed, 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 meanwhile, the first cleaning component 40 adds first alkaline cleaning liquid to the peripheral area of the polishing pad 10 to perform first pre-cleaning on the wafer 200.
Wherein the difference between the pH of the first alkaline cleaning solution and the pH of the alkaline polishing solution is-1 to 1.
Preferably, the pH of the alkaline polishing solution is 8-10, and the pH of the first alkaline cleaning solution is 7.5-10.5.
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.
Because the pH of the first alkaline cleaning solution is similar to that of the alkaline grinding fluid, the pH value of the surface of the wafer 200 can be prevented from being obviously changed, and the influence on the dynamic balance of silicic acid is avoided, so that most pollutants can be washed away, and the probability that the pollutants are adhered to the surface of the wafer 200 with higher activity after CMP is reduced.
Particularly preferably, in the present embodiment, the solute of the first alkaline cleaning solution is NH 3·H2 O and NH 4 Cl, and the concentration of NH 3·H2 O in the first alkaline cleaning solution is 0.04wt% to 0.1wt%.
NH 4 Cl not only can play a role in regulating pH, but also can provide Cl ions, so that the conversion speed of silicic acid to polysilicic acid colloid particles is accelerated, and the cleaning effect is better.
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 0.2wt% to 1wt%.
The anionic surfactant may be selected according to practical requirements, and may be, for example, sodium alkylbenzenesulfonate, sodium alkylsulfonate, or the like.
Specifically, in the embodiment, the first alkaline cleaning solution is prepared by preparing a mixed solution of ammonia water (diluted by concentrated ammonia water) with a concentration of 0.04-0.1 wt% and an anionic surfactant with a concentration of 0.2-1 wt%, and then adding an NH 4 Cl solution (the concentration may be 1-5 mol/L) to the mixed solution until the pH is 7.5-10.5.
Specifically, in S30, the rotation speed of the polishing head 20 is 80rpm to 150rpm, the rotation speed of the polishing pad 10 is 50rpm to 100rpm, and the time for the first pre-cleaning is 20S to 40S.
Specifically, in S30, the polishing head 20 and the polishing pad 10 are rotated clockwise, and the rotational speeds of the two are different.
S40, after the wafer 200 is pre-cleaned for the first time, the first cleaning assembly 40 stops adding the first 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 simultaneously the second cleaning assembly 50 adds the second alkaline cleaning solution to the peripheral area of the polishing pad 10, so as to pre-clean the wafer 200 for the second time.
Wherein the pH of the second alkaline cleaning solution is greater than the pH of the first alkaline cleaning solution.
Preferably, the second alkaline cleaning solution is ammonia water with the concentration of 0.08-0.12 wt%.
The second alkaline cleaning liquid with higher pH is used for cleaning the wafer again, so that the removal of pollutants on the surface of the wafer can be better realized.
In addition, the second alkaline cleaning solution is ammonia water with the concentration of 0.08-0.12 wt%, so that the components of the second alkaline cleaning solution are similar to those of the first alkaline cleaning solution, and the phenomenon that pollutants adhere to the surface of the wafer due to the large change of ions is avoided.
More preferably, the solute of the second alkaline cleaning solution further comprises a metal ion chelating agent, and the concentration of the metal ion chelating agent is 0.1wt% to 0.6wt%.
The metal ion chelating agent can be selected according to practical requirements, for example, EDTA, NTA, DPTA, etc.
Preferably, in S40, the rotation speed of the polishing head 20 is 80rpm to 150rpm, the rotation speed of the polishing pad 10 is 50rpm to 100rpm, the time for the second pre-cleaning is 20S to 40S, and the sum of the time for the first pre-cleaning and the time for the second pre-cleaning is not more than 70S.
With reference to the figures, the CMP apparatus further comprises a third cleaning assembly 60.
The wafer 200 cleaning method according to the present embodiment further includes, after S40, performing an operation in which the second cleaning module 50 stops adding the second alkaline cleaning solution to the peripheral area of the polishing pad 10 after the wafer 200 is completely pre-cleaned for the second time, the polishing head 20 and the polishing pad 10 continue to rotate, and simultaneously the third cleaning module 60 adds deionized water to the peripheral area of the polishing pad 10, and performs a third pre-cleaning of the wafer 200 before S50. Wherein the rotation speed of the polishing head 20 is 80 rpm-150 rpm, the rotation speed of the polishing pad 10 is 50 rpm-100 rpm, and the time for the third pre-cleaning is 20 s-40 s.
Specifically, in S40, the polishing head 20 and the polishing pad 10 are rotated clockwise, and the rotational speeds of the two are different.
The third cleaning assembly 60 is substantially identical in construction to the first cleaning assembly 40 and includes a liquid reservoir, a pressure pump, a tube and a nozzle.
And S50, taking out the wafer 200 after the second pre-cleaning, and performing post-cleaning on the wafer 200.
Specifically, in S50, the wafer 200 is cleaned by post-cleaning the wafer 200 with an acidic cleaning solution and deionized water in sequence.
Preferably, the acidic cleaning solution is an HF solution with a concentration of 0.25wt% to 1 wt%.
The HF solution may be effective in removing metallic contaminants generated in the CMP process.
In the embodiment, the operation of sequentially adopting the acid cleaning solution and the deionized water to perform post-cleaning on the wafer 200 is that after the wafer 200 is washed by the acid cleaning solution, the wafer 200 is washed by the deionized water, the time for washing the wafer 200 by the acid cleaning solution is 40 s-70 s, and the time for washing the wafer 200 by the deionized water is 30 s-60 s.
Specifically, when the wafer 200 is rinsed with the acidic cleaning solution (or deionized water), the wafer 200 may be placed on a rotating platform, and while the wafer 200 is rotated, a shower head of the acidic cleaning solution (or deionized water) moves along the diameter direction of the wafer 200 and sprays the acidic cleaning solution (or deionized water).
Preferably, the wafer 200 cleaning method of the present embodiment further includes, after the post-cleaning operation of the wafer 200, drying the wafer 200.
Wafer 200 may be dried using methods conventional in the art.
Specifically, in the present embodiment, the wafer 200 placed on the rotating platform may be rotated at a high speed under the driving of the rotating platform to achieve drying.
In the wafer cleaning method of this embodiment, after the CMP process, the polishing head 20 and the polishing pad 10 continue to rotate, and the wafer 200 is cleaned by sequentially adopting the first alkaline cleaning solution and the second alkaline cleaning solution, because the pH of the first alkaline cleaning solution is similar to that of the alkaline cleaning solution, the pH value of the surface of the wafer 200 can be prevented from being obviously changed, and the influence on the dynamic balance of silicic acid is avoided, so that most of the contaminants can be washed off, the probability that the contaminants adhere to the surface of the wafer 200 with higher activity after CMP is reduced, and after most of the contaminants are washed off, the wafer 200 is cleaned again by the second alkaline cleaning solution with higher pH, thereby better removing the contaminants on the surface of the wafer.
In addition, the CMP equipment adopted by the wafer cleaning method of the embodiment can be simply modified on the basis of the traditional CMP equipment, a plurality of cleaning components are added, and the method is simple and feasible to operate and has higher practicability.
The following are specific examples.
Example 1
A CMP apparatus is provided, the CMP apparatus including a polishing pad, a polishing head, an alkaline polishing liquid assembly, a first cleaning assembly, a second cleaning assembly, and a third cleaning assembly. Preparing a mixed solution of ammonia water with the concentration of 0.08 weight percent and sodium dodecyl sulfonate with the concentration of 0.25 weight percent, and then adding an NH 4 Cl solution with the concentration of 2.5mol/L to the mixed solution until the pH value is 9 to obtain the first alkaline cleaning solution. A mixed solution of aqueous ammonia having a concentration of 0.1wt% and EDTA having a concentration of 0.15wt% was prepared as a second alkaline cleaning solution. An HF solution having a concentration of 0.5wt% was prepared as an acidic cleaning solution. The polishing slurry (from Fuji film, model FSL 1531C) was diluted as required to give an alkaline polishing slurry with pH 9.
The polishing head fixes a 6-inch wafer on which a silicon nitride layer is formed and presses the wafer down to the peripheral area of the polishing pad, and according to a set procedure, the alkaline polishing liquid assembly adds alkaline polishing liquid to the peripheral area of the polishing pad, and the polishing head and the polishing pad rotate respectively to chemically and mechanically polish the wafer.
After the wafer is polished chemically and mechanically, the alkaline grinding liquid component stops adding alkaline grinding liquid to the peripheral area of the grinding pad, the grinding head and the grinding pad continue to rotate, and meanwhile, the first cleaning component adds first alkaline cleaning liquid to the peripheral area of the grinding pad, so that the 6-inch wafer is pre-cleaned for the first time. In the first pre-cleaning process, the rotation speed of the grinding head is 120rpm, the rotation speed of the grinding pad is 80rpm, and the time of the first pre-cleaning is 30s.
After the 6-inch wafer is pre-cleaned for the first time, the first cleaning assembly stops adding the first alkaline cleaning solution to the peripheral area of the polishing pad, the polishing head and the polishing pad 10 continue to rotate, and the second cleaning assembly 50 adds the second alkaline cleaning solution to the peripheral area of the polishing pad 10, so as to pre-clean the 6-inch wafer for the second time. In the second pre-cleaning process, the rotation speed of the grinding head is 120rpm, the rotation speed of the grinding pad is 80rpm, and the time of the second pre-cleaning is 30s.
After the 6-inch wafer is subjected to the second pre-cleaning, the second cleaning component stops adding the second alkaline cleaning liquid to the peripheral area of the polishing pad, the polishing head and the polishing pad continue to rotate, and meanwhile, 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. In the third pre-cleaning process, the rotation speed of the grinding head is 120rpm, the rotation speed of the grinding pad is 80rpm, and the time of the third pre-cleaning is 30s.
After the third pre-cleaning of the 6-inch wafer, the 6-inch wafer is placed on a rotary table, the rotary table is controlled to rotate at 100rpm, the 6-inch wafer is washed with acid cleaning liquid for 60s, then the 6-inch wafer is washed with deionized water for 45s, and finally the rotary table is controlled to rotate at 2000rpm, so that the 6-inch wafer is spin-dried.
Comparative example 1
A CMP apparatus is provided, the CMP apparatus including a polishing pad, a polishing head, an alkaline polishing liquid assembly, a first cleaning assembly, a second cleaning assembly, and a third cleaning assembly. Aqueous ammonia having a concentration of 0.1wt% was prepared as the second alkaline cleaning solution. An HF solution having a concentration of 0.5wt% was prepared as an acidic cleaning solution. The polishing slurry (from Fuji film, model FSL 1531C) was diluted as required to give an alkaline polishing slurry with pH 9.
The polishing head fixes a 6-inch wafer on which a silicon nitride layer is formed and presses the wafer down to the peripheral area of the polishing pad, and according to a set procedure, the alkaline polishing liquid assembly adds alkaline polishing liquid to the peripheral area of the polishing pad, and the polishing head and the polishing pad rotate respectively to chemically and mechanically polish the wafer.
After the chemical mechanical polishing of the wafer is completed, 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 simultaneously the second cleaning component 50 adds second alkaline cleaning liquid to the peripheral area of the polishing pad 10 to pre-clean the 6-inch wafer. Wherein, the rotation speed of the grinding head is 120rpm, the rotation speed of the grinding pad is 80rpm, and the pre-cleaning time is 30s.
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 grinding pad, the grinding head and the grinding pad continue to rotate, and meanwhile, the third cleaning component adds deionized water to the peripheral area of the grinding pad, and pre-cleaning is performed on the 6-inch wafer again. Wherein, the rotation speed of the polishing head is 120rpm, the rotation speed of the polishing pad is 80rpm, and the time for pre-cleaning again is 30s.
After the 6-inch wafer is pre-cleaned again, the 6-inch wafer is placed on a rotary table, the rotary table is controlled to rotate at 100rpm, the 6-inch wafer is washed for 60s by using the acid cleaning liquid, then the 6-inch wafer is washed for 45s by using deionized water, and finally the rotary table is controlled to rotate at 2000rpm, so that the 6-inch wafer is spin-dried.
Comparative example 2
A CMP apparatus is provided, the CMP apparatus including a polishing pad, a polishing head, an alkaline polishing liquid assembly, a first cleaning assembly, a second cleaning assembly, and a third cleaning assembly. Aqueous ammonia having a concentration of 0.1wt% was prepared as the second alkaline cleaning solution. An HF solution having a concentration of 0.5wt% was prepared as an acidic cleaning solution. The polishing slurry (from Fuji film, model FSL 1531C) was diluted as required to give an alkaline polishing slurry with pH 9.
The polishing head fixes a 6-inch wafer on which a silicon nitride layer is formed and presses the wafer down to the peripheral area of the polishing pad, and according to a set procedure, the alkaline polishing liquid assembly adds alkaline polishing liquid to the peripheral area of the polishing pad, and the polishing head and the polishing pad rotate respectively to chemically and mechanically polish the wafer.
After the wafer is polished chemically and mechanically, the alkaline grinding liquid component stops adding alkaline grinding liquid to the peripheral area of the grinding pad, the grinding head and the grinding pad continue to rotate, and meanwhile, the third cleaning component adds deionized water to the peripheral area of the grinding pad to pre-clean the 6-inch wafer. Wherein, the rotation speed of the grinding head is 120rpm, the rotation speed of the grinding pad is 80rpm, and the pre-cleaning time is 60s.
After the 6-inch wafer is pre-cleaned, the 6-inch wafer is placed on a rotary table, the rotary table is controlled to rotate at 100rpm, after the 6-inch wafer is washed by a second alkaline cleaning solution for 60s, the 6-inch wafer is washed by deionized water for 30s, then the 6-inch wafer is washed by an acid cleaning solution for 60s, then the 6-inch wafer is washed by deionized water for 45s, finally the rotary table is controlled to rotate at 2000rpm, and the 6-inch wafer is spin-dried.
Test case
100 6-Inch wafers were cleaned by the methods of example 1, comparative example 1 and comparative example 2, and after the cleaning, the cleaned 6-inch wafers obtained in example 1, comparative example 1 and comparative example 2 were inspected by an automated optical inspection system, respectively, and the inspection results were averaged to obtain the following table 1.
TABLE 1
| Example 1 | Comparative example 1 | Comparative example 2 | |
| Number of defects of 1 μm | 8.12 | 13.53 | 32.44 |
As can be seen from table 1, the 6 inch wafer surface cleaned by the method of example 1 has fewer defects.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the claims. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (7)
1. The wafer cleaning method is characterized by comprising the following steps of:
Providing a CMP apparatus and a wafer, the CMP apparatus comprising a polishing pad, a polishing head, an alkaline polishing liquid component, a first cleaning component, and a second cleaning component;
The grinding head is used for fixing the wafer and pressing the wafer down to the peripheral area of the grinding pad, the alkaline grinding liquid component is used for adding 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 is polished chemically and mechanically, 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, meanwhile, the first cleaning component adds first alkaline cleaning liquid to the peripheral area of the polishing pad to perform primary 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, solutes of the first alkaline cleaning liquid are NH 3·H2 O and NH 4 Cl, and the concentration of NH 3·H2 O in the first alkaline cleaning liquid is 0.04-0.1 wt%;
After the wafer is subjected to the first pre-cleaning, the first cleaning component stops adding the first alkaline cleaning solution to the peripheral area of the grinding pad, the grinding head and the grinding pad continue to rotate, and the second cleaning component adds a second alkaline cleaning solution to the peripheral area of the grinding pad to perform the second pre-cleaning on the wafer, wherein the pH value of the second alkaline cleaning solution is greater than that of the first alkaline cleaning solution, the second alkaline cleaning solution is ammonia water with the concentration of 0.08-0.12 wt%, and
And taking out the wafer after the second pre-cleaning, and carrying out post-cleaning on the wafer.
2. The method according to claim 1, wherein the polishing head and the polishing pad continue to rotate, and the first cleaning unit adds a first alkaline cleaning solution to the peripheral area of the polishing pad, and the polishing head rotates at 80rpm to 150rpm, the polishing pad rotates at 50rpm to 100rpm, and the first pre-cleaning time is 20s to 40s.
3. The method according to claim 1, wherein the polishing head and the polishing pad continue to rotate, while the second cleaning unit adds the second alkaline cleaning liquid to the peripheral region of the polishing pad, the polishing head rotates at 80rpm to 150rpm, the polishing pad rotates at 50rpm to 100rpm, the second pre-cleaning time is 20s to 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 of claim 1, wherein the CMP apparatus further comprises a third cleaning assembly;
the wafer cleaning method further comprises the following steps of after the operation of carrying out second pre-cleaning on the wafer, and before the operation of taking out the wafer after the second pre-cleaning:
After the wafer is subjected to the second pre-cleaning, the second cleaning component stops adding the second alkaline cleaning liquid to the peripheral area of the grinding pad, the grinding head and the grinding pad continue to rotate, meanwhile, the third cleaning component adds deionized water to the peripheral area of the grinding pad, and the wafer is subjected to the third pre-cleaning, wherein the rotating speed of the grinding head is 80-150 rpm, the rotating speed of the grinding pad is 50-100 rpm, and the time of the third pre-cleaning is 20-40 s.
5. The method of claim 1, wherein the step of cleaning the wafer comprises post-cleaning the wafer with an acidic cleaning solution and deionized water.
6. The method for cleaning a wafer according to claim 5, wherein the step of sequentially performing post-cleaning on the wafer by using an acidic cleaning solution and deionized water is performed by using the deionized water to rinse the wafer after the acidic cleaning solution is used for rinsing the wafer, wherein the time for rinsing the wafer by using the acidic cleaning solution is 40 s-70 s, the time for rinsing the wafer by using the deionized water is 30 s-60 s, and the acidic cleaning solution is an HF solution with a concentration of 0.25wt% to 1 wt%.
7. The wafer cleaning method of claim 1, wherein the solute of the first alkaline cleaning solution further comprises an anionic surfactant, the concentration of the anionic surfactant being 0.2wt% to 1wt%;
The solute of the second alkaline cleaning liquid further comprises a metal ion chelating agent, and the concentration of the metal ion chelating agent is 0.1-0.6 wt%.
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