Silicon wafer surface grinding method and device

Abstract

The invention provides a silicon wafer surface grinding method and device. The method comprises the steps that a first supply unit is controlled to supply a first grinding material to a grinding area; receiving and responding to the switching signal; controlling a second supply unit to supply a second grinding material to the grinding area; wherein the first grinding material and the second grinding material are different in particle size. An automatic switching double-mortar-barrel liquid supply mode is adopted in a single process of the same equipment, large-particle-size grinding materials are adopted in the coarse grinding stage so that the material removal efficiency can be improved, small-particle-size grinding materials are automatically switched in the fine grinding stage so that surface damage generated in the coarse grinding stage can be removed, the product yield and quality are improved, and the product quality is improved. And the cost and the risk caused by multi-equipment processing are avoided, and the silicon wafer with high surface quality is efficiently obtained.

Description

Technical Field

[0001] This application belongs to the field of semiconductor manufacturing technology, and in particular relates to a method for grinding the surface of silicon wafers. Specifically, it relates to a grinding method and equipment that achieves efficient grinding and low surface roughness of silicon wafers through a dual feeding mode of abrasives with different particle sizes. Background Technology

[0002] In the semiconductor industry chain, silicon wafers, as the basic substrate material, directly affect the quality of subsequent processes such as photolithography and thin film deposition, as well as the performance of the final chip, due to the flatness and roughness of their surface. Polishing is one of the key steps in silicon wafer manufacturing, and its purpose is to remove the processing damage layer on the silicon wafer surface and reduce surface roughness to obtain a high degree of flatness.

[0003] Currently, most mainstream silicon wafer grinding equipment uses a single slurry tank supply system. This system typically includes a slurry tank, a circulating pump, a flow controller, and a stirring pump. During processing, the grinding disc applies pressure to the silicon wafer, and the slurry is transported between the disc and the wafer as a medium. The abrasive particles in the slurry (usually silicon carbide or alumina) grind the surface of the silicon wafer with their sharp edges and high hardness, thereby removing the material.

[0004] However, this single-mortar tank system has an inherent technical contradiction: grinding efficiency and surface quality are difficult to balance. Current technology often forces manufacturers to compromise when faced with the demands of high efficiency and high surface quality—either sacrificing efficiency to ensure quality, or sacrificing quality to pursue efficiency. To achieve efficient coarse grinding followed by fine grinding on the same silicon wafer, it is necessary to perform this process on different equipment or at different workstations. This not only increases equipment investment costs but also introduces additional error and contamination risks due to multiple loading, unloading, and positioning operations, thus hindering further improvements in semiconductor manufacturing processes. Summary of the Invention

[0005] This application provides a silicon wafer surface grinding method and equipment, which overcomes the above-mentioned defects of the existing single slurry bucket grinding system and solves the technical problem that it is impossible to achieve both high grinding efficiency and low surface roughness on the same grinding equipment.

[0006] To solve at least one of the above-mentioned technical problems, the technical solution adopted in this application is:

[0007] A method for polishing the surface of a silicon wafer, comprising the following steps:

[0008] Control the first supply unit to supply the first abrasive to the grinding area;

[0009] Receive and respond to switching signals;

[0010] Control the second supply unit to supply the second abrasive to the grinding area;

[0011] The first abrasive and the second abrasive have different particle sizes.

[0012] Furthermore, the switching signal is one of the following: a timing signal based on grinding time, a preset timing signal based on grinding process steps, or a thickness signal based on the real-time thickness of the silicon wafer reaching a preset threshold.

[0013] Furthermore, the first abrasive and the second abrasive are grinding sands of the same composition, and the average particle size of the second abrasive is smaller than the average particle size of the first abrasive.

[0014] Furthermore, the average particle size range of the first abrasive is 10-11 μm, and the average particle size range of the second abrasive is 8-9 μm.

[0015] Furthermore, when controlling the second supply unit to supply the second abrasive to the grinding area, the first supply unit is first controlled to stop supplying liquid, and then the second supply unit is started to supply liquid after a preset time delay.

[0016] Furthermore, the first supply unit and the second supply unit supply liquid to the grinding area via the same distribution unit.

[0017] Furthermore, the liquid supply of the first supply unit and the second supply unit is regulated by independent flow controllers; and both the first supply unit and the second supply unit are equipped with a stirring pump and a circulation pump.

[0018] A silicon wafer surface polishing apparatus for implementing the method described above, the apparatus comprising:

[0019] The grinding machine body includes an upper plate for applying pressure and a grinding disc for carrying and rotating silicon wafers;

[0020] The first supply unit is used to store and supply the first abrasive.

[0021] The second supply unit is used to store and supply the second abrasive.

[0022] A distribution unit is used to guide abrasive to the grinding area. It is provided with at least two liquid inlets and one liquid outlet, and is connected to the first supply unit and the second supply unit through the liquid inlets respectively.

[0023] The control unit is used to control the switching between the first supply unit and the second supply unit.

[0024] Furthermore, the distribution unit is a sand pot for carrying the liquid supply, which has a frustum-shaped liquid collection tank and a dispersion surface located below the liquid collection tank. The dispersion surface is constructed as a frustum, and the minor diameter surfaces of the liquid collection tank and the dispersion surface are opposite each other, and the included angle between their generatrices is an obtuse angle.

[0025] Furthermore, both the first supply unit and the second supply unit include: a mortar tank, a circulating pump for providing driving force to the abrasive, a stirring pump for stirring the abrasive in the mortar tank, and a flow controller for regulating the abrasive flow rate.

[0026] The silicon wafer surface grinding method and equipment designed in this application adopts an automatically switching dual slurry tank liquid supply mode in a single process of the same equipment. In the coarse grinding stage, large-particle abrasive is used to improve material removal efficiency, and in the fine grinding stage, it automatically switches to small-particle abrasive to remove the surface damage generated in the coarse grinding stage. This not only improves product yield and quality, but also avoids the cost and risk brought about by multi-equipment processing, and efficiently obtains silicon wafers with high surface quality. Attached Figure Description

[0027] Figure 1 This is a flowchart of the silicon wafer surface polishing method in this application;

[0028] Figure 2 This is a perspective view of the grinding equipment in this application;

[0029] Figure 3 This is a cross-sectional view of the sand-flowing teapot in this application.

[0030] In the diagram: 10, First supply unit; 20, Second supply unit; 30, Grinding disc; 40, Upper plate; 50, Flowing sand pot; 51, Liquid inlet; 52, Liquid outlet; 53, Overflow port; 54, Liquid collection tank; 55, Dispersion surface; 60, Mortar bucket; 70, Agitator pump; 80, Circulation pump; 90, Flow controller. Detailed Implementation

[0031] The present application will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0032] This embodiment proposes a method for polishing the surface of a silicon wafer, such as... Figure 1 As shown, this method is applied to, for example Figure 2 The grinding equipment shown, which has a dual mortar supply system, includes the following steps:

[0033] When grinding begins, the first supply unit is controlled to supply the first abrasive to the grinding area.

[0034] Specifically, upon starting the grinding equipment and receiving the instruction, the control unit retrieves the preset parameters for the first stage from the stored process formula. These parameters include at least the first abrasive, the liquid supply flow rate, the upper platen pressure, and the grinding disc rotation speed.

[0035] The control unit then sends these instructions to the first supply unit 10, the distribution unit, and the grinding machine body via communication lines. The distribution unit is a sand-flowing jug 50; the grinding machine body includes a grinding disc 30 for holding silicon wafers and an upper plate 40 located above the grinding disc 30. The stirring pump 70 in the first supply unit 10 is started to operate, continuously agitating the first abrasive material in the slurry tank 60; simultaneously, the circulation pump 80 starts operating, providing driving force for the abrasive material to move from the slurry tank 60 to the grinding area, while simultaneously controlling the upper plate 40 to apply pressure to the silicon wafer, and the grinding disc 30 begins to rotate.

[0036] In this embodiment, the first supply unit 10 is mainly used to store and supply the first abrasive, and the second supply unit 20 is mainly used to store and supply the second abrasive. Both units are equipped with a slurry tank 60 for storing the abrasive, a stirring pump 70 for stirring the abrasive, and a circulation pump 80 for supplying the abrasive. The first supply unit 10 and the second supply unit 20 supply liquid to the grinding area through the same distribution unit. Each slurry tank is equipped with an independent circulation pump 80, a flow controller 90, and a stirring pump 70, thereby ensuring that the two grinding supply systems can flow in independently and steadily, ultimately achieving precise control of the liquid supply and uniform and stable abrasive.

[0037] The first and second abrasives are grinding sands of the same composition but different particle sizes, and the average particle size D50 of the second abrasive is smaller than that of the first abrasive. Both the first and second abrasives are grinding sands of the same composition, but the average particle size D50 of the first abrasive ranges from 10 to 11 μm, and its value includes but is not limited to 10 μm and 11 μm; the average particle size D50 of the second abrasive ranges from 8 to 9 μm, and its value includes but is not limited to 8 μm and 9 μm.

[0038] The first stage is the coarse grinding stage. Driven by the circulating pump 80, the abrasive flows from the first slurry tank, through the delivery pipe, and to the flow controller 90. The flow controller 90 then controls and adjusts the flow rate in the first liquid supply unit 10. The adjusted first abrasive is connected to the inlet 51 of the sand-flowing jug 50 through a pipe, enters the collection tank 54 of the sand-flowing jug 50, and then flows out through the outlet 52 after being diffused by the dispersion surface 55 in the sand-flowing jug 50. The first abrasive is dripped or sprayed onto the center of the rotating grinding disc. Under the action of centrifugal force, the abrasive is evenly distributed on the entire surface of the grinding disc and enters the grinding area composed of the upper disc 40, the silicon wafer, and the grinding disc 30. At this point, the first abrasive officially begins to perform coarse grinding on the surface of the silicon wafer with high efficiency.

[0039] Then, it receives and responds to a switching signal, which is intended to switch from the first stage of coarse grinding to the second stage of fine grinding. The system first determines whether it has received a switching signal; if not, it continues with the first stage of coarse grinding.

[0040] If a switching signal is received, it could be a timed signal triggered by the grinding time, meaning the timer starts counting from the rough grinding stage and automatically generates a switching signal when the preset rough grinding time is reached. Alternatively, it could be a preset timing signal triggered by the grinding process steps, meaning that rough grinding and fine grinding are set as two consecutive, fixed process steps throughout the grinding program; after all preset actions in the rough grinding step are completed, the program itself generates an internal instruction as a signal to switch to the fine grinding step. Or, it could be a thickness signal triggered by the silicon wafer's real-time thickness reaching a preset threshold, meaning that during the grinding process, a thickness measuring instrument integrated into the equipment, such as an infrared or capacitive thickness gauge, monitors the real-time thickness of the silicon wafer online; when the monitored thickness value reaches a preset target thickness threshold, the thickness gauge sends a switching signal to the control unit.

[0041] Upon receiving any of the aforementioned switching signals, the control unit triggers a switching action, thereby switching from the first supply unit 10 to the second supply unit 20.

[0042] The second supply unit is controlled to supply the second abrasive to the grinding area. This step aims to effectively reduce the surface roughness of the silicon wafer and improve its surface quality.

[0043] Specifically, the control unit sends a stop command to the circulation pump 80 and flow controller 90 of the first supply unit 10, causing the circulation pump 80 to stop operating, cutting off the delivery of the first abrasive, and the flow controller 90 of the first supply unit 10 to shut down. After stopping the first supply unit 10, the control system waits for a preset delay time to allow sufficient time for the first abrasive remaining in the pipeline and the sand-dispensing jug 50 to be emptied, minimizing the mixing of two different abrasive sizes in the distribution unit.

[0044] After a preset delay, the control unit sends a start liquid supply command to the second supply unit. First, the stirring pump 70 is started to ensure that the second abrasive is uniformly suspended; then, the circulation pump 80 is started to provide conveying power for the second abrasive. The flow controller 90 of the second supply unit 20 starts working and precisely adjusts and establishes a new and stable abrasive supply according to the preset target flow rate of the fine grinding stage.

[0045] Through the above steps, the system achieves seamless, automatic and smooth switching between different abrasive supplies, thereby achieving the two originally contradictory goals of high removal rate and high surface quality in a single process on a single machine.

[0046] This method can use large-particle abrasives in the coarse grinding stage to improve material removal efficiency, and automatically switch to small-particle abrasives in the fine grinding stage to remove surface damage generated in the coarse grinding stage. This not only improves product yield and quality, but also avoids the cost and risks of processing with multiple equipment, and efficiently obtains silicon wafers with high surface quality.

[0047] A silicon wafer surface polishing apparatus for implementing the method described above, such as Figure 2 As shown, the device includes a grinding mill body, a first supply unit 10 for storing and supplying a first abrasive, a second supply unit 20 for storing and supplying a second abrasive, a distribution unit for guiding the abrasive to the grinding area, and a control unit for controlling the switching between the first supply unit 10 and the second supply unit 20. Both the first supply unit 10 and the second supply unit 20 include a slurry tank 60, a circulation pump 80 for providing driving force to the abrasive, a stirring pump 70 for stirring the abrasive in the slurry tank 60, and a flow controller 90 for regulating the abrasive flow rate.

[0048] The grinding machine body includes an upper plate 40 for applying pressure and a grinding disc 30 for carrying and rotating silicon wafers, wherein the grinding area is formed by the upper plate 40, the silicon wafers and the grinding disc 30.

[0049] like Figure 3 As shown, the distribution unit is a sand pot 50 for carrying the supplied liquid. It has at least two inlets 51 and one outlet 52. In this embodiment, the inlet 51 connected to the first supply unit 10 is located at the center of the top of the sand pot 50. There are two inlets 51 connected to the second supply unit 20, which are symmetrically arranged on the diameter of the top of the sand pot 50. When in use, only one of them is used, and the other is blocked for backup.

[0050] Furthermore, the sand-flowing vessel 50 has a frustum-shaped liquid collection tank 54 and a dispersion surface 55 located below the liquid collection tank 54. The dispersion surface 55 is constructed as a frustum, and the minor diameter surfaces of the liquid collection tank 54 and the dispersion surface 55 are opposite each other, with their generatrices forming obtuse angles. At least two overflow ports 53 are also provided on the cylindrical surface of the sand-flowing vessel 50, with the overflow ports 53 located near the top end of the sand-flowing vessel 50.

[0051] The collection tank 54, resembling a bucket with a wider top and narrower bottom, is used to receive and buffer the abrasive. It receives the abrasive flowing at high speed from the pipeline through the upper inlet, and this structure can safely and smoothly receive the abrasive flowing in from all the inlets 51, converting the impact force into static pressure. All the abrasive gathers at the center position, facilitating its downward flow out.

[0052] The dispersing surface 55 is an inverted frustum, resembling a funnel, wider at the bottom than the top, used for diffusion and flow guidance. It smoothly and evenly diffuses the abrasive flowing from the bottom of the collection tank 54 along its inclined surface, ultimately flowing out from the outlet 52. In this embodiment, several outlets 52 are evenly arranged along its annular bottom surface, ensuring abrasive flows out from various locations.

[0053] The short-diameter surfaces of the collection tank 54 and the dispersion surface 55 are positioned opposite each other, that is, the small bottom surface of the collection tank 54 and the small top surface of the dispersion surface are positioned vertically opposite each other, with a narrow outlet in the middle. This arrangement forms a buffer throttling orifice, which can stabilize the flow rate.

[0054] For the collecting tank 54, its obtuse angle generatrix is ​​an outward-expanding structure. The gentle sidewalls allow the abrasive to be guided more smoothly to the central outlet, reducing turbulence and dead zones, and preventing particles from accumulating in corners. As for the dispersing surface 55, it has a gentle, open obtuse-angled outer slope. The gentle slope guides the abrasive to spread evenly in all directions, covering the entire cross-section of the outlet 52, ensuring a consistent flow rate throughout the circumference during outflow.

[0055] The silicon wafer surface grinding method and equipment designed in this application adopts an automatically switching dual slurry tank liquid supply mode in a single process of the same equipment. In the coarse grinding stage, large-particle abrasive is used to improve material removal efficiency, and in the fine grinding stage, it automatically switches to small-particle abrasive to remove the surface damage generated in the coarse grinding stage. This not only improves product yield and quality, but also avoids the cost and risk brought about by multi-equipment processing, and efficiently obtains silicon wafers with high surface quality.

[0056] The embodiments of this application have been described in detail above. These descriptions are merely preferred embodiments and should not be construed as limiting the scope of this application. All equivalent variations and modifications made within the scope of this application should still fall within the patent coverage of this application.

Claims

1. A method for polishing the surface of a silicon wafer, characterized in that the steps include... include: Control the first supply unit to supply the first abrasive to the grinding area; Receive and respond to switching signals; Control the second supply unit to supply the second abrasive to the grinding area; The first abrasive and the second abrasive have different particle sizes.

2. The method according to claim 1, characterized in that, The switching signal is one of the following: a timing signal based on grinding time, a preset timing signal based on grinding process steps, or a thickness signal based on the real-time thickness of the silicon wafer reaching a preset threshold.

3. The method according to claim 1 or 2, characterized in that, The first abrasive and the second abrasive are grinding sands of the same composition, and the average particle size of the second abrasive is smaller than the average particle size of the first abrasive.

4. The method according to claim 3, characterized in that, The average particle size range of the first abrasive is 10-11 μm, and the average particle size range of the second abrasive is 8-9 μm.

5. The method according to any one of claims 1-2 and 4, characterized in that, When controlling the second supply unit to supply the second abrasive to the grinding area, the first supply unit is first controlled to stop supplying liquid, and then the second supply unit is started to supply liquid after a preset time delay.

6. The method according to claim 5, characterized in that, The first supply unit and the second supply unit supply liquid to the grinding area via the same distribution unit.

7. The method according to claim 6, characterized in that, The liquid supply of the first supply unit and the second supply unit is regulated by independent flow controllers; and both the first supply unit and the second supply unit are equipped with a stirring pump and a circulation pump.

8. A silicon wafer surface polishing apparatus for implementing the method according to any one of claims 1-7, characterized in that, The device includes: The grinding machine body includes an upper plate for applying pressure and a grinding disc for carrying and rotating silicon wafers; The first supply unit is used to store and supply the first abrasive. The second supply unit is used to store and supply the second abrasive. A distribution unit is used to guide abrasive to the grinding area. It is provided with at least two liquid inlets and one liquid outlet, and is connected to the first supply unit and the second supply unit through the liquid inlets respectively. The control unit is used to control the switching between the first supply unit and the second supply unit.

9. The device according to claim 8, characterized in that, The distribution unit is a sand pot for carrying the liquid supply. It has a frustum-shaped liquid collection tank and a dispersion surface located below the liquid collection tank. The dispersion surface is constructed as a frustum, and the minor diameter surfaces of the liquid collection tank and the dispersion surface are opposite each other, and the included angle between their generatrices is an obtuse angle.

10. The device according to claim 9, characterized in that, Both the first supply unit and the second supply unit include: a mortar tank, a circulating pump for providing driving force to the abrasive, a stirring pump for stirring the abrasive in the mortar tank, and a flow controller for regulating the abrasive flow rate.

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