A monitoring method for SiO2 grinding liquid residue

Abstract

The present invention discloses a method for monitoring SiO2 grinding liquid residues, which belongs to the field of semiconductor manufacturing processes. First, a silicon wafer with a PETEOS film layer of a specific thickness deposited thereon is ground for a certain period of time, and a cleaning process is completed, and then defects are scanned. After the initial scan, a PETEOS film layer of a certain thickness is deposited on the surface of the silicon wafer as an amplification layer. The size of the grinding liquid residue will be magnified and can be accurately detected by the defect scanner. By calculating the difference between the results of the two defect scans, the grinding liquid residue situation is accurately judged. The cleaning method uses a PVA brush, passes ammonia water of a specific concentration, brushes the silicon wafer, and then megasonic cleaning is performed. After that, heated deionized water is used for rinsing, and finally high-speed rotation and drying are performed to complete the cleaning process. Compared with the existing technology, the cleaning ability is improved, and the cleaning requirements of multiple different types of SiO2 grinding liquids can be met at the same time.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor manufacturing technology and relates to a monitoring method for SiO2 grinding liquid residue. Background Art

[0002] With the advancement of semiconductor manufacturing processes, photolithography has placed increasing demands on the flatness of silicon wafer surfaces, giving rise to the chemical mechanical polishing (CMP) process. Under the action of a polishing pad and slurry, a thin layer of the material surface is first partially softened by the chemical action of the slurry. The mechanical action of the pad and slurry then removes this layer, achieving planarization. Finally, the surface is cleaned and dried.

[0003] During the CMP process, silicon wafers undergo a post-CMP clean step, where cleaning equipment and chemicals are used to achieve a clean silicon wafer. In existing 0.5 / 0.35μm oxide CMP processes, it has been found that existing cleaning methods are ineffective in removing polishing slurry residue from the silicon wafer surface. Existing monitoring methods cannot fully reflect the presence of SiO2 polishing slurry residue on the silicon wafer surface. Summary of the Invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a monitoring method for SiO2 polishing liquid residue to solve the problem that the existing monitoring method cannot fully reflect the situation of SiO2 polishing liquid residue on the silicon wafer surface in the existing 0.5 / 0.35μm process Oxide CMP process practice.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention discloses a method for monitoring SiO2 grinding liquid residue, comprising:

[0007] S1: Deposit the first layer of PETEOS SiO2 film on the surface of the bare silicon wafer and grind it;

[0008] S2: Cleaning the polished silicon wafer;

[0009] S3: Scan the cleaned silicon wafer for defects and obtain the defect count A;

[0010] S4: depositing a second layer of PETEOS SiO2 film on the scanned silicon wafer surface;

[0011] S5: The silicon wafer on which the second PETEOS SiO2 film layer is deposited is subjected to a second defect scan to obtain the defect number B. If the difference between B and A is not greater than the set value, it is considered to have passed the monitoring; otherwise, it is considered to have failed the monitoring.

[0012] Preferably, the first PETEOS SiO2 film layer in S1 is

[0013] Preferably, in S1, a grinding process is used to grind the silicon wafer after the PETEOS SiO2 film layer is deposited, and the main process time of the grinding process is 60s to 120s.

[0014] Preferably, the defect in S3 is a defect with a particle size greater than or equal to 0.2 μm.

[0015] Preferably, the second PETEOS SiO2 film layer in S4 is

[0016] Preferably, a method for cleaning SiO2 polishing liquid residue comprises:

[0017] S6: scrubbing the polished silicon wafer;

[0018] S7: performing megasonic cleaning on the scrubbed silicon wafer;

[0019] S8: Rinse the silicon wafer after megasonic cleaning;

[0020] S9: Drying the rinsed silicon wafer.

[0021] Preferably, in S6, a PVA brush is used with 2-5% (mass fraction) ammonia water to scrub the surface of the silicon wafer for 0.5-3 minutes.

[0022] Preferably, in S7, the megasonic cleaning frequency is 800 to 2000 kHz, and the cleaning time is 0.5 to 3 minutes.

[0023] Preferably, in S8, deionized water with a temperature of 40 to 50° C. is used, and the rinsing time is 0.5 to 2 minutes.

[0024] Preferably, in S9 , the silicon wafer is dried by rotating at a speed of 1000 to 1500 rpm for 15 to 60 seconds.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention discloses a method for monitoring SiO2 grinding liquid residues. First, a silicon wafer with a PETEOS film layer of a specific thickness is deposited, ground for a certain period of time, and a cleaning process is completed, and then the defects are scanned. However, the size of most SiO2 grinding liquid residues is between 0.1μm and 0.2μm, and the existing defect scanner is unable to fully detect them. After the initial scan, a PETEOS film layer of a certain thickness needs to be deposited on the surface of the silicon wafer as an amplification layer. The size of the grinding liquid residue will be magnified to 0.3μm to 0.5μm, which can be accurately detected by the defect scanner. By calculating the difference between the two defect scan results, the grinding liquid residue situation can be accurately judged.

[0027] Furthermore, the method for cleaning SiO2 polishing slurry residues first involves scrubbing the silicon wafer with a PVA brush, passing ammonia water of a specific concentration. Adjusting the ammonia concentration changes the pH of the solution, which in turn affects the zeta potential. Lowering the zeta potential causes the polishing slurry residue on the silicon wafer surface, the silicon wafer surface, and the brush to all have a negative potential, generating mutual electrostatic repulsion between them. This facilitates the removal of residue from the wafer and brush surfaces, ultimately removing the polishing slurry residue.

[0028] Then, megasonic cleaning is performed for a certain period of time. Megasonic cleaning is a high-frequency oscillation signal emitted by a generator, which is converted into high-frequency mechanical oscillation by a converter and transmitted to the medium. The cleaning liquid is sprayed onto the surface of the silicon wafer. The fast-flowing liquid can generate a peeling force on the particles attached to the surface of the wafer. When the peeling force is greater than the van der Waals force and electrostatic force acting on the particles at the same time, the particles are peeled off the wafer surface and carried away by the fast-flowing liquid. Compared with ultrasonic cleaning, megasonic cleaning has a gentler effect. Therefore, the appropriate vibration frequency should be selected based on the size of the particles to be removed and the impact force that the devices on the wafer surface can withstand. Generally, the particle size suitable for megasonic cleaning is 0.1 to 0.3 μm, and the particle size suitable for ultrasonic cleaning is above 0.4 μm.

[0029] Afterwards, heated deionized water is used to rinse the silicon wafer for a certain period of time. Compared with deionized water at room temperature, the effect of removing surface particles is improved to a certain extent. Finally, the centrifugal force generated by high-speed rotation is used to dry the water traces on the surface of the silicon wafer to complete the cleaning process. The existing cleaning technology has a good cleaning effect on the residues of a certain imported model of grinding fluid. The number of defects after cleaning can be controlled between 1 and 50. However, the cleaning effect of the residues of a certain domestic model of grinding fluid is poor. The number of defects is basically between 80 and 200, which cannot meet the process requirements. The improved cleaning technology has improved the cleaning ability of the residues of the domestic grinding fluid of this model. The number of defects after cleaning can also meet the process requirement of less than 50, which is consistent with the imported grinding fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1It is a schematic diagram of the cleaning process of the present invention;

[0031] Figure 2 Schematic diagram of the membrane structure of the monitoring film.

[0032] Wherein: 1-second layer of PETEOS (plasma enhanced tetraethyl orthosilicate) SiO2; 2-oxide CMP (oxide chemical mechanical polishing) interface; 3-first layer of PETEOS (plasma enhanced tetraethyl orthosilicate) SiO2; 4-bare silicon wafer. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described 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 making creative efforts should fall within the scope of protection of the present invention.

[0034] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0035] The present invention is described in further detail below with reference to the accompanying drawings:

[0036] See also Figure 1 、 Figure 2 The present invention is based on the existing oxide CMP process and uses an independent grinder and an independent cleaning machine to implement the grinding and cleaning processes of silicon wafers. The present invention discloses a method for monitoring SiO2 polishing liquid residue, comprising:

[0037] S1: depositing the first layer of PETEOS SiO2 3 film on the surface of the bare silicon wafer 4 and grinding it;

[0038] S2: Cleaning the polished silicon wafer;

[0039] S3: Scan the cleaned silicon wafer for defects and obtain the defect count A;

[0040] S4: depositing a second layer of PETEOS SiO21 film on the scanned silicon wafer surface;

[0041] S5: The silicon wafer on which the PETEOS SiO2 film layer is deposited again is subjected to a second defect scan to obtain the defect number B. If the difference between B and A is not greater than 50, the monitoring is considered qualified; otherwise, the monitoring is considered unqualified.

[0042] The present invention discloses a method for monitoring SiO2 grinding liquid residues. First, a silicon wafer with a first layer of PETEOS SiO23 film deposited with a specific thickness is ground for a certain period of time, and a cleaning process is completed, and then the defects are scanned. However, the size of most SiO2 grinding liquid residues is between 0.1μm and 0.2μm, and the existing defect scanner is not capable of fully detecting them. After the initial scan, a second layer of PETEOS SiO21 film of a certain thickness needs to be deposited on the surface of the silicon wafer as an amplification layer. The size of the grinding liquid residue will be magnified to 0.3μm to 0.5μm, which can be accurately detected by the defect scanner. By calculating the difference between the two defect scan results, the grinding liquid residue situation can be accurately judged.

[0043] Preferably, the method for cleaning SiO2 grinding liquid residue from the ground silicon wafer in S2 comprises:

[0044] S6: Use a PVA brush with 2-5% ammonia water to scrub the surface of the silicon wafer for 0.5-3 minutes;

[0045] S7: Perform megasonic cleaning on the scrubbed silicon wafer, with a megasonic cleaning frequency of 800 to 2000 kHz and a cleaning time of 0.5 to 3 minutes;

[0046] S8: Rinse the silicon wafer after megasonic cleaning with deionized water at a temperature of 40 to 50° C. for 0.5 to 2 minutes;

[0047] S9: The rinsed silicon wafer is rotated at a speed of 1000 to 1500 rpm for 15 to 60 seconds to dry.

[0048] First, use a PVA brush to scrub the silicon wafer with ammonia water of a specific concentration. Adjusting the ammonia concentration changes the pH of the solution, which in turn affects the zeta potential. Lowering the zeta potential shifts the polishing slurry residue on the wafer surface, the wafer surface, and the brush to a negative potential. This creates electrostatic repulsion between the three, facilitating the removal of residue from the wafer and brush surfaces, ultimately removing the polishing slurry residue. Then megasonic cleaning is performed for a certain period of time. Megasonic cleaning is a high-frequency (800kHz~2000kHz oscillation signal) emitted by a generator, which is converted into a high-frequency mechanical oscillation by a converter and propagated to the medium. The cleaning liquid is sprayed onto the surface of the silicon wafer. The fast-flowing liquid can produce a peeling force on the particles attached to the surface of the wafer. When the peeling force is greater than the van der Waals force and the electrostatic force acting on the particles at the same time, the particles are peeled off the wafer surface and carried away by the fast-flowing liquid. Compared with ultrasonic cleaning, megasonic cleaning is more gentle. Therefore, the appropriate vibration frequency should be selected according to the size of the particles to be removed and the impact force that the wafer surface device can withstand. Generally, megasonic cleaning is suitable for removing particles with a size of 0.1~0.3μm, and ultrasonic cleaning is suitable for The size of the particles to be removed is above 0.4μm. After that, heated deionized water is used to rinse the silicon wafer for a certain period of time. Compared with deionized water at room temperature, the effect of removing surface particles is improved to a certain extent. Finally, the centrifugal force generated by high-speed rotation is used to dry the water traces on the surface of the silicon wafer to complete the cleaning process. The existing cleaning technology has a good cleaning effect on the residues of a certain imported model of grinding fluid, and the number of defects after cleaning can be controlled between 1 and 50. However, the cleaning effect of the residues of a certain domestic model of grinding fluid is poor, and the number of defects is basically between 80 and 200, which cannot meet the process requirements. The improved cleaning technology has improved the cleaning ability of the residues of the domestic grinding fluid of this model, and the number of defects after cleaning can also meet the process requirement of less than 50, which is consistent with the imported grinding fluid.

[0049] [Example 1]

[0050] The present invention discloses a method for monitoring SiO2 polishing liquid residue, comprising the following steps:

[0051] S1: Deposition on the surface of bare silicon wafer 4 The first layer of PETEOS SiO23 film with a thickness of 1000 nm is subjected to a grinding process, and the main process time of the grinding process is 60 seconds;

[0052] S2: The silicon wafers obtained in S1 are cleaned according to steps S6 to S9;

[0053] S3: The silicon wafer completed in S2 is scanned for defects using a KLA2139 defect scanner, and the number of defects obtained is 23.

[0054] S4: After completing S3, deposit The second layer of PETEOS SiO21 film has a thickness of 1.5-2.5mm.

[0055] S5: The above silicon wafer is re-scanned for defects, and the defect count is 57. The difference between the two defect counts is 34, which is less than or equal to 50, and is considered to have passed the monitoring.

[0056] A method for cleaning SiO2 polishing liquid residues comprises the following steps:

[0057] S6. After the polishing process, use a PVA (polyvinyl alcohol) brush with 3% ammonia solution to scrub the surface of the silicon wafer for 100 seconds.

[0058] S7. Clean the silicon wafer surface using a 1 MHz megasonic cleaning process for 40 seconds.

[0059] S8. Rinse the silicon wafer surface with 45°C deionized water for 40 seconds.

[0060] S9. Spin the silicon wafer at a high speed of 1300 rpm for 30 seconds to dry the silicon wafer and complete the silicon wafer cleaning process.

[0061] [Example 2]

[0062] The present invention discloses a method for monitoring SiO2 polishing liquid residue, comprising the following steps:

[0063] S1: Deposition on the surface of bare silicon wafer 4 The first layer of PETEOS SiO23 film with a thickness of 1000 nm is subjected to a grinding process, and the main process time of the grinding process is 120 seconds;

[0064] S2: The silicon wafers obtained in S1 are cleaned according to steps S6 to S9;

[0065] S3: The silicon wafer completed in S2 is scanned for defects using a KLA2139 defect scanner, and the number of defects obtained is 39.

[0066] S4: After completing S3, deposit The second layer of PETEOS SiO21 film has a thickness of 1.5-2.5mm.

[0067] S5: The above silicon wafer is re-scanned for defects, and the defect number is 82. The difference between the two defect numbers is 43, which is less than or equal to 50, and the wafer passes the monitoring.

[0068] A method for cleaning SiO2 polishing liquid residues comprises the following steps:

[0069] S6. After the polishing process, scrub the surface of the silicon wafer using a PVA (polyvinyl alcohol) brush with 2% ammonia solution for 120 seconds.

[0070] S7. Clean the silicon wafer surface using 800 kHz megasonic cleaning for 120 seconds.

[0071] S8. Rinse the silicon wafer surface with 40°C deionized water for 120 seconds.

[0072] S9. Spin the silicon wafer at a high speed of 1000 rpm for 60 seconds to dry the silicon wafer and complete the silicon wafer cleaning process.

[0073] [Example 3]

[0074] The present invention discloses a method for monitoring SiO2 polishing liquid residue, comprising the following steps:

[0075] S1: Deposition on the surface of bare silicon wafer 4 The first layer of PETEOS SiO23 film with a thickness of 1000 nm is subjected to a grinding process, and the main process time of the grinding process is 90 seconds;

[0076] S2: The silicon wafers obtained in S1 are cleaned according to steps S6 to S9;

[0077] S3: The silicon wafer completed in S2 is scanned for defects using a KLA2139 defect scanner, and the number of defects obtained is 15.

[0078] S4: After completing S3, deposit The second layer of PETEOS SiO21 film has a thickness of 1.5-2.5mm.

[0079] S5: The above silicon wafer is re-scanned for defects, and the defect number is 36. The difference between the two defect numbers is 21, which is less than or equal to 50, and the wafer passes the monitoring.

[0080] A method for cleaning SiO2 polishing liquid residues comprises the following steps:

[0081] S6. After the polishing process, use a PVA (polyvinyl alcohol) brush with 5% ammonia solution to scrub the surface of the silicon wafer for 30 seconds.

[0082] S7. Clean the silicon wafer surface using 2000kHz megasonic cleaning for 30 seconds.

[0083] S8. Rinse the silicon wafer surface with 50°C deionized water for 30 seconds.

[0084] S9. Spin the silicon wafer at a high speed of 1500 rpm for 15 seconds to dry the silicon wafer and complete the silicon wafer cleaning process.

[0085] In summary, the present invention discloses a cleaning method in a method for monitoring SiO2 grinding liquid residues, first using a PVA brush, passing ammonia water of a specific concentration, scrubbing the silicon wafer, then megasonic cleaning for a certain time, after which it is rinsed with heated deionized water for a certain time, and finally spinning at high speed to complete the cleaning process. Compared with the prior art, the cleaning ability is improved, and the cleaning requirements of various types of SiO2 grinding liquids can be met at the same time. A method for monitoring SiO2 grinding liquid residues disclosed by the present invention, first grinding a silicon wafer with a PETEOS film layer of a specific thickness for a certain time, and completing the cleaning process. Then, the defects are scanned, and a PETEOS film layer of a certain thickness is deposited again as an amplification layer, and the defects are scanned again. By calculating the difference between the two defect scanning results, the grinding liquid residue situation can be determined. Compared with the prior art, the SiO2 grinding liquid residue can be monitored more accurately.

[0086] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for monitoring SiO2 polishing liquid residue, characterized in that: include: S1: depositing a first layer of PETEOS SiO2 (3) film on the surface of a bare silicon wafer (4) and grinding it; S2: Cleaning the polished silicon wafer; S3: Scan the cleaned silicon wafer for defects and obtain the defect count A; S4: depositing a second layer of PETEOS SiO2(1) film on the scanned silicon wafer surface; S5: The silicon wafer on which the second PETEOS SiO2(1) film layer is deposited is subjected to a second defect scan to obtain the defect number B. If the difference between B and A is not greater than the set value, it is considered to be qualified for monitoring; otherwise, it is considered to be unqualified for monitoring.

2. The method for monitoring SiO2 polishing liquid residue according to claim 1, wherein: The first PETEOS SiO2(3) film layer in S1 is 3. The method for monitoring SiO2 polishing liquid residue according to claim 1, wherein: In S1, a grinding process is used to grind the silicon wafer after the PETEOS SiO2 film layer is deposited. The main process time of the grinding process is 60s to 120s.

4. The method for monitoring SiO2 polishing liquid residue according to claim 1, wherein: The defect in S3 is a defect having a particle size greater than or equal to 0.2 μm.

5. The method for monitoring SiO2 polishing liquid residue according to claim 1, wherein: The second PETEOS SiO2(1) film layer in S4 is 6. The method for monitoring SiO2 polishing liquid residue according to claim 1, wherein: The cleaning described in S2 includes: S6: scrubbing the polished silicon wafer; S7: performing megasonic cleaning on the scrubbed silicon wafer; S8: rinsing the silicon wafer after megasonic cleaning; S9: Drying the rinsed silicon wafer.

7. The method for monitoring SiO2 polishing liquid residue according to claim 6, wherein: In S6, a PVA brush is used with ammonia water having a concentration of 2 to 5% by mass to scrub the surface of the silicon wafer for 0.5 to 3 minutes.

8. The method for monitoring SiO2 polishing liquid residue according to claim 6, wherein: In S7, the megasonic cleaning frequency is 800 to 2000 kHz, and the cleaning time is 0.5 to 3 minutes.

9. The method for monitoring SiO2 polishing liquid residue according to claim 6, wherein: In S8, deionized water with a temperature of 40 to 50° C. is used, and the rinsing time is 0.5 to 2 minutes.

10. The method for monitoring SiO2 polishing liquid residue according to claim 6, characterized in that: In S9 , the silicon wafer is dried by rotating at a rotation speed of 1000 to 1500 rpm for 15 to 60 seconds.

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