Method for improving stability of CMP grinding rate

Abstract

The invention provides a method for improving CMP (chemical mechanical polishing) rate stability, which comprises the following steps of: 1, finishing and cleaning a polishing pad in a high-pressure water washing manner at the initial stage of use of the polishing pad; secondly, in the middle use period of the grinding pad, the grinding pad is trimmed and cleaned in the mode that high-pressure water washing and a diamond grinding disc are combined; and thirdly, in the later use period of the grinding pad, the grinding pad is trimmed and cleaned in the mode that high-pressure water washing and the diamond grinding disc are combined, and the use frequency of the diamond grinding disc is larger than that of the diamond grinding disc in the second step. The high-pressure water flushing device is arranged on the swing arm for controlling the moving direction of the diamond grinding disc, and the grinding pad is trimmed and cleaned by using high-pressure water flushing and the diamond grinding disc in the grinding process, so that the probability of scratching the surface of a wafer is reduced while the service life of the diamond grinding disc and the grinding pad is greatly prolonged; the production cost is reduced; the product quality is improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a method for improving the stability of CMP polishing rate. Background Art

[0002] The chemical mechanical polishing (CMP) process is a method that combines chemical polishing with mechanical polishing to flatten the surface of a silicon wafer. Figure 1 As shown, during the grinding process, there is a large amount of grinding liquid containing abrasive particles on the grinding pad. The wafer surface adsorbed on the grinding head, especially the material with raised parts, reacts chemically with the grinding liquid to form a surface layer that is relatively easy to remove. This surface layer is mechanically worn away under the pressure of the abrasive particles and the relative movement with the grinding pad, making the wafer surface flat.

[0003] The roughness and porosity of the polishing pad surface have a direct relationship with the CMP polishing rate. The main function of the diamond polishing disk is to optimize the thickness distribution and surface morphology of the polishing pad, help the polishing liquid to be evenly distributed on the polishing pad, re-open the gaps closed by polishing, ensure the regeneration of the polishing force on the polishing pad surface, prevent the surface from vitrification, and take away the polishing by-products generated during the polishing process to reduce the scratch defects caused by the polishing by-products during the polishing process.

[0004] In the standard CMP process, as the working time on the surface of the grinding pad increases, the diamond grinding disc gradually passivates, resulting in a decrease in dressing ability, so that the grinding liquid cannot be evenly distributed on the surface of the grinding pad, affecting the stability of the CMP process. At the same time, the diamond particles on the surface of the diamond grinding disc will also have the probability of falling off, resulting in the risk of scratching the surface of the wafer. In order to ensure the stability of the CMP process, the existing process sets a fixed lifespan for the diamond grinding disc. When a certain value (this value is small) is reached, a new diamond grinding disc will be replaced to ensure a suitable grinding rate. This seriously affects production efficiency and increases production costs in actual mass production processes. Summary of the invention

[0005] In view of the shortcomings of the prior art described above, the purpose of the present application is to provide a method for improving the stability of the CMP grinding rate, so as to solve the problems in the prior art that the life of the diamond grinding disk is short, resulting in poor stability of the CMP grinding rate and the grinding process at the end of the life of the diamond grinding disk is prone to scratch defects on the wafer.

[0006] To achieve the above objectives and other related objectives, the present application provides a method for improving the stability of CMP polishing rate, comprising:

[0007] Step 1, in the initial stage of using the polishing pad, the polishing pad is trimmed and cleaned by high-pressure water flushing;

[0008] Step 2, in the middle stage of using the polishing pad, the polishing pad is trimmed and cleaned by combining high-pressure water flushing and a diamond polishing disk;

[0009] Step 3, in the later stage of using the polishing pad, the polishing pad is trimmed and cleaned by combining high-pressure water flushing and a diamond polishing disk, and the number of times the diamond polishing disk is used is more than that in Step 2.

[0010] Preferably, in the initial stage of using the polishing pad, the number of wafers polished is less than 100.

[0011] Preferably, in the middle stage of using the polishing pad, the number of wafers polished is greater than or equal to 100 and less than 300.

[0012] Preferably, in the later stage of using the polishing pad, the number of wafers polished is greater than or equal to 300.

[0013] Preferably, a high-pressure water flushing device is provided on the swing arm for controlling the moving direction of the diamond polishing disk, and high-pressure water flushing is implemented through this device.

[0014] Preferably, in Step 2 and Step 3, high-pressure water flushing and the diamond polishing disk work simultaneously.

[0015] Preferably, in Step 3, the polishing pad is trimmed once and the diamond polishing disk is reused twice.

[0016] As described above, the method for improving the stability of the CMP polishing rate provided by this application has the following beneficial effects: By providing a high-pressure water flushing device on the swing arm for controlling the moving direction of the diamond polishing disk, during the polishing process, high-pressure water flushing and the diamond polishing disk are used to trim and clean the polishing pad, which greatly improves the service life of the diamond polishing disk and the polishing pad while reducing the probability of scratches on the wafer surface, reducing production costs and improving product quality. Description of the Drawings

[0017] In order to more clearly illustrate the specific embodiments of this application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 Shown as a schematic cross-sectional structure diagram of a CMP device;

[0019] Figure 2It is a flowchart showing the method for improving the stability of CMP polishing rate provided by the embodiments of the present application;

[0020] Figure 3 It is a surface topography diagram of the polishing pad in the initial stage of use;

[0021] Figure 4 It is a device diagram of CMP;

[0022] Figure 5 It is a comparison diagram of the surface topography of the polishing pad after cleaning the polishing pad according to the prior art and the present application respectively at the end of the life of the diamond polishing disk. Detailed implementation manners

[0023] The following uses specific specific examples to illustrate the implementation manners of the present application. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. The present application can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0024] Next, the technical solutions in the present application will be described clearly and completely in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present application.

[0025] In the description of the present application, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0026] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and can also be the communication inside two elements. It can be a wireless connection or a wired connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0027] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0028] Please refer to Figure 2 , which shows a flowchart of a method for improving the stability of CMP polishing rate provided by an embodiment of the present application.

[0029] As Figure 2 shown, the method for improving the stability of CMP polishing rate includes the following steps:

[0030] Step 1, in the initial stage of using the polishing pad, the polishing pad is trimmed and cleaned by means of high-pressure water flushing;

[0031] Step 2, in the middle stage of using the polishing pad, the polishing pad is trimmed and cleaned by combining high-pressure water flushing and a diamond polishing disk;

[0032] Step 3, in the later stage of using the polishing pad, the polishing pad is trimmed and cleaned by combining high-pressure water flushing and a diamond polishing disk, and the number of times the diamond polishing disk is used is more than that in Step 2.

[0033] In Step 1, in the initial stage of using the polishing pad, the porosity of the polishing pad is relatively high and the pore distribution is relatively uniform (as Figure 3 shown), and the polishing pad is trimmed and cleaned by means of high-pressure water flushing to wash open the pores slightly closed due to polishing and remove the by-products generated by polishing. As an example, when the number of wafers polished is less than 100, it is regarded as the initial stage of using the polishing pad.

[0034] In Step 2, in the middle stage of using the polishing pad, the polishing pad is trimmed and cleaned by combining high-pressure water flushing and a diamond polishing disk. The high-pressure water flushing and the diamond polishing disk work simultaneously, which can reduce the working time of the diamond polishing disk, reduce the loss of the diamond polishing disk and the loss caused by the diamond polishing disk to the trimming of the polishing pad, extend the life of the diamond polishing disk, and at the same time clean the diamond particles that may fall on the diamond polishing disk. Compared with only using the diamond polishing disk to trim and clean the polishing pad, by combining high-pressure water flushing and a diamond polishing disk, the working time of the diamond polishing disk can be halved. For example, when trimming the polishing pad once, the number of times of repeatedly using the diamond polishing disk can be reduced from twice to only once. As an example, when the number of wafers polished is greater than or equal to 100 and less than 300, it is regarded as the middle stage of using the polishing pad.

[0035] In Step 3, the polishing pad is trimmed and cleaned by combining high-pressure water flushing and a diamond grinding disk. The high-pressure water flushing and the diamond grinding disk work simultaneously. High-pressure water flushing can make up for the deficiency in trimming ability caused by the passivation of the diamond grinding disk, and can significantly reduce the scratching defects on the wafer surface caused by the insufficient cleaning ability at the end of the diamond grinding disk's service life, resulting in the retention of grinding by-products and possibly fallen diamond particles on the polishing pad surface. Compared with Step 2, the working duration of the diamond grinding disk needs to be increased by at least one time. For example, if the diamond grinding disk is only used once for trimming a polishing pad, it needs to be changed to using the diamond grinding disk twice repeatedly. As an example, when the number of polished wafers is greater than or equal to 300, it is regarded as the late stage of the polishing pad's use.

[0036] As Figure 4 shown, a high-pressure water flushing device is provided on the swing arm that controls the moving direction of the diamond grinding disk. As an example, high-pressure water is ejected through the nozzle of this device.

[0037] As Figure 5 shown, at the end of the diamond grinding disk's service life, compared with only using the diamond grinding disk to trim and clean the polishing pad, the method of combining high-pressure water flushing and the diamond grinding disk can significantly improve the surface topography of the polishing pad, thereby extending the service life of the diamond grinding disk.

[0038] It should be noted that the diagrams provided in this embodiment only illustrate the basic concept of the present application in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The types, quantities, and proportions of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0039] In summary, the method for improving the stability of the CMP polishing rate provided by the present application, by providing a high-pressure water flushing device on the swing arm that controls the moving direction of the diamond grinding disk, using high-pressure water flushing and the diamond grinding disk to trim and clean the polishing pad during the polishing process, can significantly increase the service life of the diamond grinding disk and the polishing pad while reducing the probability of scratching on the wafer surface, reducing production costs and improving product quality. Therefore, the present application effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0040] The above embodiments are only illustrative of the principles and effects of the present application, and are not used to limit the present application. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present application.

Claims

1. A method for improving the stability of CMP polishing rate, characterized in that: The method comprises: Step 1: In the early stage of using the polishing pad, the polishing pad is trimmed and cleaned by high-pressure water washing; Step 2: In the middle of the use of the grinding pad, the grinding pad is trimmed and cleaned by combining high-pressure water washing and diamond grinding disc; Step three, in the later stage of the use of the grinding pad, the grinding pad is trimmed and cleaned by combining high-pressure water washing and diamond grinding disc, and the number of times the diamond grinding disc is used is more than the number of times the diamond grinding disc is used in step two.

2. The method according to claim 1, characterized in that In the initial use of the polishing pad, the number of wafers polished is less than 100.

3. The method according to claim 1, characterized in that In the middle period of use of the polishing pad, the number of polished wafers is greater than or equal to 100 and less than 300.

4. The method according to claim 1, characterized in that: In the later stage of use of the grinding pad, the number of ground wafers is greater than or equal to 300.

5. The method according to claim 1, characterized in that A high-pressure water flushing device is arranged on the swing arm for controlling the moving direction of the diamond grinding disc, and the high-pressure water flushing is carried out by the device.

6. The method according to claim 1, characterized in that In step 2 and step 3, the high-pressure water jet and the diamond grinding disc work simultaneously.

7. The method according to claim 1, characterized in that In the step three, the grinding pad is trimmed once and the diamond grinding disc is reused twice.

Images