Wafer cleaning method

Abstract

The present application relates to a wafer cleaning method, used for cleaning a polished wafer surface. The wafer cleaning method comprises: spraying hydrofluoric acid of a first preset concentration on a wafer surface for a first preset time period; brushing in a brushing cavity the wafer surface after spraying; and cleaning in a cleaning cavity the wafer surface having undergone brushing. The present application solves the problem in the prior art of poor cleaning effect for residual grinding liquid on wafers, thereby improving the cleaning effect for residual grinding liquid on wafers.

Description

Wafer cleaning method Technical Field

[0001] The present application relates to the field of wafer cleaning, and in particular to a wafer cleaning method. Background Art

[0002] In the wafer manufacturing process, post-polishing cleaning plays a key role in ensuring wafer cleanliness. Wafer cleaning primarily removes residual polishing slurry and the natural oxide layer on the wafer surface after chemical mechanical polishing (CMP). The polishing slurry primarily consists of an alkaline solvent, a buffer, and abrasive particles.

[0003] In existing technologies, there are two common post-polishing cleaning methods: tank cleaning and single-wafer brush cleaning. Single-wafer brush cleaning offers advantages such as shorter process times, better cleaning results, and less fragmentation. It has become the primary post-polishing cleaning method, especially after the production of 300mm wafers.

[0004] The conventional process flow for single-wafer scrubbing includes: wafer wetting, SC1 (a mixture of ammonia, hydrogen peroxide, and water) scrubbing, DIW (deionized water) cleaning, and alternating cleaning with DHF (hydrofluoric acid) and DIO3 (ozone deionized water). The SC1 scrubbing step removes residual polishing fluid, while alternating DHF and DIO3 cleaning removes surface metal contamination and the natural oxide layer. However, the effectiveness of SC1 scrubbing is significantly affected by the preceding process. The surface properties of wafers of different batches and doping types vary greatly, and the difficulty of cleaning residual polishing fluid varies. The effect of cleaning particles after polishing often varies greatly, affecting the subsequent process and the yield of the final wafer product.

[0005] Summary of the Invention

[0006] The embodiments of the present application provide a wafer cleaning method to at least solve the problem of poor cleaning effect of residual polishing liquid on the wafer in the related art.

[0007] In a first aspect, an embodiment of the present application provides a wafer cleaning method for cleaning a polished wafer surface, comprising:

[0008] Spraying the surface of the wafer with hydrofluoric acid of a first preset concentration for a first preset time;

[0009] scrubbing the wafer surface after spraying in a scrubbing chamber;

[0010] The wafer surface after scrubbing is cleaned in a cleaning chamber.

[0011] In some embodiments, scrubbing the wafer surface after spraying in the scrubbing chamber includes:

[0012] Spraying the wafer surface after the spraying with DIW to form a protective water film on the wafer surface;

[0013] The wafer with the protective water film is placed into the scrubbing chamber for scrubbing.

[0014] In some embodiments, the first predetermined concentration is between 3000 ppm and 10000 ppm.

[0015] In some embodiments, the first preset time is between 5s and 30s.

[0016] In a second aspect, an embodiment of the present application further provides a wafer cleaning method for cleaning a polished wafer surface, comprising:

[0017] Alternately spraying the wafer surface with hydrofluoric acid of a first preset concentration and DIO3 of a second preset concentration;

[0018] scrubbing the wafer surface after spraying in a scrubbing chamber;

[0019] The wafer surface after scrubbing is cleaned in a cleaning chamber.

[0020] In some embodiments, scrubbing the wafer surface after spraying in the scrubbing chamber includes:

[0021] Spraying the wafer surface after the spraying with DIW to form a protective water film on the wafer surface;

[0022] The wafer with the protective water film is placed into the scrubbing chamber for scrubbing.

[0023] In some embodiments, the first predetermined concentration is between 3000 ppm and 10000 ppm.

[0024] In some embodiments, the spraying time of hydrofluoric acid of the first preset concentration is between 5 seconds and 30 seconds each time.

[0025] In some embodiments, the second predetermined concentration is between 20 ppm and 30 ppm.

[0026] In some embodiments, the spraying time of DIO3 with the second preset concentration is between 10 seconds and 15 seconds each time.

[0027] In some embodiments, before alternately spraying the wafer surface with hydrofluoric acid of a first preset concentration and DiO 3 of a second preset concentration, the method further includes:

[0028] The wafer surface is sprayed with SC1 for a second preset time.

[0029] In some embodiments, the second preset time is between 5s and 20s.

[0030] Compared with the prior art, the wafer cleaning method provided in the embodiment of the present application effectively removes large particles and metals on the wafer surface, alkaline polishing liquid matrix and thins the oxide layer on the wafer surface by alternately spraying hydrofluoric acid, hydrofluoric acid and DIO3, reduces the contamination of the brush by metal and polishing liquid, and facilitates the exposure and removal of micron-level polishing particles, so as to extend the service life of the brush, improve the brushing efficiency and improve the particle level, and improve the stability of the process results of the post-polishing wafer cleaning step for different products.

[0031] The details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent.

[0032] Summary of the Figures

[0033] The features and properties of the present invention are further described by the following examples and accompanying drawings.

[0034] FIG1 is a flow chart of a wafer cleaning method according to an embodiment of the present application;

[0035] FIG2 is a diagram showing the experimental effect of a wafer cleaning method according to an embodiment of the present application;

[0036] FIG3 is a flow chart of a wafer cleaning method according to another embodiment of the present application;

[0037] FIG4 is a diagram showing the experimental results of a wafer cleaning method according to another embodiment of the present application.

[0038] Preferred embodiments of the present invention

[0039] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is described and illustrated below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely used to explain this application and are not intended to limit this application. Based on the embodiments provided in this application, all other embodiments obtained by those of ordinary skill in the art without making any creative efforts are within the scope of protection of this application.

[0040] Unless otherwise defined, the technical terms or scientific terms involved in this application should be understood by people with ordinary skills in the technical field to which this application belongs. The words "one", "a", "the" and similar words involved in this application do not indicate quantitative limitations and can represent singular or plural. The terms "include", "comprise", "have" and any of their variations involved in this application are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units inherent to these processes, methods, products or devices. The "multiple" involved in this application means greater than or equal to two. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, "A and / or B" can mean: A exists alone, A and B exist at the same time, and B exists alone. The terms "first", "second", "third" and the like involved in this application are merely to distinguish similar objects and do not represent a specific ordering of objects.

[0041] An embodiment of the present application provides a wafer cleaning method for cleaning a polished wafer surface. FIG1 is a flow chart of the wafer cleaning method according to an embodiment of the present application. As shown in FIG1 , the method includes the following steps:

[0042] Step S101 : spraying hydrofluoric acid of a first preset concentration on the surface of a wafer for a first preset time.

[0043] As shown in Figure 2, the vertical axis in Figure 2 represents the number of LPD particles remaining on the wafer surface, with the unit being ea, and LPD stands for Light Point Defect. A1 in Figure 2 represents the number of particles on the surface of the nitrogen (N)-doped wafer after the single-wafer scrubbing or trough scrubbing in the prior art described in the background technology, A2 represents the number of particles on the surface of the phosphorus (P)-doped wafer after the single-wafer scrubbing or trough scrubbing in the prior art described in the background technology, and A3 represents the number of particles on the surface of the sulfur (S)-doped wafer after the single-wafer scrubbing or trough scrubbing in the prior art described in the background technology. B1 in Figure 2 represents the number of particles on the surface of the nitrogen (N)-doped wafer after cleaning using the wafer cleaning method in the embodiment of the present application, B2 represents the number of particles on the surface of the phosphorus (P)-doped wafer after cleaning using the wafer cleaning method in the embodiment of the present application, and B3 represents the number of particles on the surface of the sulfur (S)-doped wafer after cleaning using the wafer cleaning method in the embodiment of the present application. Phosphorus (P), sulfur (S), and nitrogen (N) in Figure 2 represent wafer products heavily doped with phosphorus (P), sulfur (S), and nitrogen (N).

[0044] As shown in Figure 2, before the wafer is scrubbed, pre-treatment of the wafer with hydrofluoric acid can effectively remove the number of LPD particles on the wafer surface. At the same time, hydrofluoric acid can also effectively remove the metal and alkaline polishing liquid matrix on the wafer surface and thin the oxide layer on the wafer surface. To a certain extent, it can also reduce the subsequent contamination of the metal and polishing liquid on the brush for scrubbing the wafer, and facilitate the exposure and removal of micron-level polishing particles.

[0045] Step S102 , scrubbing the wafer surface after spraying in a scrubbing chamber.

[0046] In this step, after spraying the wafer surface with hydrofluoric acid, brushing is performed to reduce the contamination of the brush by metal and polishing fluid, making it easier to expose and remove micron-sized polishing particles.

[0047] Step S103 , cleaning the wafer surface after scrubbing in a cleaning chamber.

[0048] Through the above steps S101 to S103, before the wafer is brushed, hydrofluoric acid is used to spray the wafer surface, which can effectively remove large particles of metal and alkaline polishing liquid matrix on the wafer surface and thin the oxide layer on the wafer surface, reduce the contamination of the brush by metal and polishing liquid, and facilitate the exposure and removal of micron-level polishing particles, so as to extend the service life of the brush, improve the brushing efficiency and improve the particle level, and improve the stability of the process results of the post-polishing wafer cleaning step for different products, especially heavily doped products such as phosphorus, sulfur, and nitrogen.

[0049] In some embodiments, scrubbing the wafer surface after spraying in the scrubbing chamber includes: spraying the wafer surface after spraying with DIW to form a protective water film on the wafer surface; placing the wafer with the protective water film into the scrubbing chamber for scrubbing.

[0050] In this embodiment, after the hydrofluoric acid spray treatment, DIW cleaning is used to remove the grinding liquid and form a water film protection on the wafer surface so that the wafer is wet when entering the scrubbing chamber, thereby ensuring the stability of the wafer surface properties and achieving better particle removal effect during scrubbing.

[0051] In some embodiments, the first predetermined concentration is between 3000 ppm and 10000 ppm.

[0052] It should be noted that, in some embodiments, as the concentration increases, the particles on the wafer surface continue to decrease, and a better de-particle effect can be achieved.

[0053] In some embodiments, the first preset time is between 5 seconds and 30 seconds.

[0054] It should be noted that, in some embodiments, as time goes by, the particles on the wafer surface continue to decrease, which can achieve a better de-particle effect.

[0055] This embodiment also provides a wafer cleaning method for cleaning the polished wafer surface. FIG3 is a flow chart of the wafer cleaning method according to an embodiment of the present application. As shown in FIG3 , the method includes the following steps:

[0056] In step S301 , hydrofluoric acid of a first preset concentration and DIO 3 of a second preset concentration are alternately sprayed on the wafer surface.

[0057] As shown in Figure 4, the vertical axis in Figure 4 represents the number of LPD particles remaining on the wafer surface, with the unit being ea, and LPD stands for Light Point Defect. A1 in Figure 4 represents the number of particles on the surface of the nitrogen (N)-doped wafer after the single-wafer scrubbing or trough scrubbing in the prior art described in the background art, A2 represents the number of particles on the surface of the phosphorus (P)-doped wafer after the single-wafer scrubbing or trough scrubbing in the prior art described in the background art, and A3 represents the number of particles on the surface of the sulfur (S)-doped wafer after the single-wafer scrubbing or trough scrubbing in the prior art described in the background art. C1 in Figure 4 represents the number of particles on the surface of the nitrogen (N)-doped wafer after cleaning using the wafer cleaning method in the embodiment of the present application, C2 represents the number of particles on the surface of the phosphorus (P)-doped wafer after cleaning using the wafer cleaning method in the embodiment of the present application, and C3 represents the number of particles on the surface of the sulfur (S)-doped wafer after cleaning using the wafer cleaning method in the embodiment of the present application. Phosphorus (P), sulfur (S), and nitrogen (N) in Figure 2 represent wafer products heavily doped with phosphorus (P), sulfur (S), and nitrogen (N).

[0058] As shown in Figure 4, before the wafer is scrubbed, pre-treatment of the wafer with hydrofluoric acid can effectively remove large particles and metal and alkaline polishing liquid matrices on the wafer surface and thin the oxide layer on the wafer surface. At the same time, it can also reduce the subsequent contamination of the brush for scrubbing the wafer by metal and polishing liquid to a certain extent, and facilitate the exposure and removal of micron-level polishing particles.

[0059] Step S302 , scrubbing the wafer surface after spraying in a scrubbing chamber.

[0060] In this step, after spraying the wafer surface with hydrofluoric acid, brushing is performed to reduce the contamination of the brush by metal and polishing fluid, making it easier to expose and remove micron-sized polishing particles.

[0061] Step S303 , cleaning the wafer surface after scrubbing in a cleaning chamber.

[0062] Through the above steps S301 to S303, before the wafer is brushed, hydrofluoric acid is used to spray the wafer surface, which can effectively remove the number of LPD particles on the wafer surface. At the same time, hydrofluoric acid can also effectively remove the metal and alkaline polishing liquid matrix on the wafer surface and thin the oxide layer on the wafer surface, reducing the contamination of the brush by metal and polishing liquid, facilitating the exposure and removal of micron-level polishing particles, so as to extend the service life of the brush, improve the brushing efficiency and improve the particle level, and improve the stability of the process results of the post-polishing wafer cleaning step for different products, especially heavily doped products such as phosphorus, sulfur, and nitrogen.

[0063] In this embodiment, based on the wafer cleaning method of Figure 1, a DIO3 treatment is added, utilizing alternating sprays of DHF and DIO3 for more effective pre-brushing. Under the same process conditions and time, referring to Figures 2 and 4, alternating sprays of DHF and DIO3 significantly improve the final particle count. Furthermore, this pre-treatment method of alternating sprays of DHF and DIO3 weakens the adhesion between the polishing slurry and the wafer surface, thereby enhancing the subsequent brush cleaning effect and improving the particle count on the surface of wafer products with different doping types, such as N, P, and S.

[0064] In some embodiments, scrubbing the wafer surface after spraying in the scrubbing chamber includes: spraying the wafer surface after spraying with DIW to form a protective water film on the wafer surface; placing the wafer with the protective water film into the scrubbing chamber for scrubbing.

[0065] In this embodiment, after the hydrofluoric acid and DIO3 are sprayed alternately, DIW is used for cleaning to remove the liquid and form a water film protection on the surface of the wafer so that the wafer is wet when entering the scrubbing chamber, thereby ensuring the stability of the wafer surface properties and achieving better particle removal effect during scrubbing.

[0066] In some embodiments, the first preset concentration is between 3000 ppm and 10000 ppm. It should be noted that, in some embodiments, as the concentration increases, the particles on the wafer surface continue to decrease, thereby achieving a better de-particle effect.

[0067] In some embodiments, during the alternating spraying of hydrofluoric acid and DIO3, the duration of each hydrofluoric acid spraying is between 5s and 30s. It should be noted that in some embodiments, as time increases, the particles on the wafer surface continue to decrease, which can achieve a better particle removal effect.

[0068] In some embodiments, the second predetermined concentration is between 20 ppm and 30 ppm. In this embodiment, as the concentration increases, the particles on the wafer surface continue to decrease, thereby achieving a better de-particle effect.

[0069] In some embodiments, each spray time of the second preset concentration of DIO3 is between 10 seconds and 15 seconds. In this embodiment, particles on the wafer surface continue to decrease over time, achieving a better particle removal effect. It should be noted that the oxidizing ability of different DIO3 concentrations varies. When the DIO3 concentration is 20 ppm, the spray time can be set to 15 seconds; when the DIO3 concentration is 30 ppm, the spray time can be set to 10 seconds.

[0070] Through the above method, the alternating spraying of DHF and DIO3 can remove some particles in advance, as shown in Table 1 below, thereby reducing the pollution to the brush, extending the service life of the brush, and improving the cleaning effect.

[0071] It should be noted that A represents the single-wafer scrubbing or trough scrubbing method in the prior art described in the background art, and C represents the wafer cleaning method in FIG. 3 of the present application.

[0072] In some embodiments, before alternately spraying the wafer surface with hydrofluoric acid of a first preset concentration and DIO3 of a second preset concentration, the wafer surface may be sprayed with SC1 for a second preset time.

[0073] After the wafer is polished, not only will a large amount of polishing liquid containing micron and nano-scale particles remain on the front of the wafer, but the resin wax required for patching will also remain on the back of the wafer, which is difficult to clean. When there is residual wax on the back of the wafer, the oxide layer on the back of the wafer will be covered by the residual wax, resulting in uneven etching on the back of the wafer.

[0074] Therefore, in this embodiment, by spraying the wafer surface with SC1 for the second preset time, residual wax on the wafer surface can be removed, thereby preventing uneven etching on the back side of the wafer.

[0075] In some embodiments, the second preset time is between 5s and 20s.

[0076] In this embodiment, as time goes by, the particles on the wafer surface continue to decrease, thereby achieving a better particle removal effect.

[0077] Those skilled in the art should understand that the various technical features of the above-described embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0078] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A wafer cleaning method for cleaning a polished wafer surface, characterized in that: include: Spraying the surface of the wafer with hydrofluoric acid of a first preset concentration for a first preset time; brushing the surface of the wafer after spraying in the brushing chamber; The wafer surface after scrubbing is cleaned in a cleaning chamber.

2. The wafer cleaning method according to claim 1, characterized in that: Brushing the surface of the wafer after spraying in the brushing chamber includes: Using DIW to spray the surface of the wafer after the spraying to form a protective water film on the surface of the wafer; The wafer with the protective water film is placed into the scrubbing chamber for scrubbing.

3. The wafer cleaning method according to claim 1, characterized in that: The first preset concentration is between 3000 ppm and 10000 ppm.

4. The wafer cleaning method according to claim 1, characterized in that: The first preset time is between 5s and 30s.

5. A wafer cleaning method for cleaning a polished wafer surface, characterized in that: include: Alternately spraying the surface of the wafer with hydrofluoric acid of a first preset concentration and DIO3 of a second preset concentration; brushing the surface of the wafer after spraying in the brushing chamber; The wafer surface after scrubbing is cleaned in a cleaning chamber.

6. The wafer cleaning method according to claim 5, characterized in that: Brushing the surface of the wafer after spraying in the brushing chamber includes: Using DIW to spray the surface of the wafer after the spraying to form a protective water film on the surface of the wafer; The wafer with the protective water film is placed into the scrubbing chamber for scrubbing.

7. The wafer cleaning method according to claim 5, characterized in that: The first preset concentration is between 3000 ppm and 10000 ppm.

8. The wafer cleaning method according to claim 5, characterized in that: The spraying time of the hydrofluoric acid with the first preset concentration is between 5s and 30s each time.

9. The wafer cleaning method according to claim 5, characterized in that: The second preset concentration is between 20 ppm and 30 ppm.

10. The wafer cleaning method according to claim 5, characterized in that: The spraying time of DIO3 of the second preset concentration is between 10s and 15s each time.

11. The wafer cleaning method according to claim 5, characterized in that: Before alternately spraying the wafer surface with hydrofluoric acid of a first preset concentration and DIO3 of a second preset concentration, the method further includes: The wafer surface is sprayed with SC1 for a second preset time.

12. The wafer cleaning method according to claim 11, characterized in that: The second preset time is between 5s and 20s.

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