Method for cleaning wafer in grinding cavity

Abstract

The invention provides a method for cleaning a wafer in a grinding cavity. A base and a cleaning nozzle are arranged at the top of the base, a driving device is mounted in the base, the cleaning nozzle is mounted at the top of the base, works cooperatively with the driving device and can spray water in a 360-degree rotating manner, and a water curtain covering the diameter of a wafer is sprayed to the crystal face of the wafer, so that the ground wafer is pre-cleaned; and controlling the impact force of the water curtain on the wafer to be smaller than the self weight of the wafer so as to prevent the wafer from deflecting. The cleaning nozzle can spray out a water curtain covering the diameter of a wafer, the front cleaning area of the wafer is increased, the cleaning pressure of consumable items in a cleaning cavity is reduced, the service life of the consumable items is prolonged, the replacement frequency of the cleaning consumable items is reduced, the production cost is reduced, the wafer defects are reduced, and the wafer yield is improved.

Description

Technical Field

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

[0002] like Figure 1 As shown, taking the Reflexion LK 300MM CMP polishing machine as an example, the wafer located at the wafer input position of the wafer exchanger is polished by three grinding plates in the polishing chamber and then sent to the cleaning chamber. It will undergo preliminary cleaning in the wafer output device of the wafer exchanger before entering the cleaning chamber for further cleaning.

[0003] like Figure 2 As shown in the middle left picture, the carrier in the wafer outgoing position will spray out a thin stream of water when the wafer is not in contact with it to detect whether the wafer exists. Figure 2 As shown in the middle right figure, when the wafer is loaded on the carrier, the water column disappears, the water pressure inside the carrier becomes stronger, and the water pressure passes through the transducer to make the water spray base (such as Figure 2 6 cleaning nozzles (as shown in the left figure) on Figure 3 ) is triggered, thereby spraying water to clean the front side of the wafer.

[0004] like Figure 4 As shown in the figure above, the traditional cleaning nozzle is fixed and when it sprays water on the front side of the wafer, it sprays a water column with a certain angle relative to the crystal surface. Due to the angle and shape of the water spray, it cannot completely cover the entire area of ​​the front side of the 12-inch wafer (such as Figure 4 As shown in the figure below, the blank area represents the uncleaned wafer area. Wafers are not thoroughly cleaned at the wafer exit point, resulting in increased pressure during subsequent cleaning of the wafer by the cleaning chamber consumables, reducing the normal service life of the cleaning chamber consumables. When the cleaning chamber consumables reach the end of their service life, their cleaning ability weakens. Incomplete cleaning of residues on the polished wafer surface can lead to wafer defects and affect wafer yield. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of this application is to provide a method for cleaning wafers in a grinding chamber, which is used to solve the problem in the prior art that incomplete cleaning of wafers in the grinding chamber leads to a reduced service life of cleaning chamber consumables.

[0006] To achieve the above object and other related objects, the present application provides a method for cleaning a wafer in a polishing cavity, which comprises: setting a base with a driving device installed inside at the center of the wafer transmission position of the polishing cavity, and setting a cleaning nozzle capable of spraying water in a 360-degree rotation on the top of the base to work with the driving device, spraying a water curtain covering the diameter of the wafer to the wafer surface to pre-clean the polished wafer, and controlling the impact force of the water curtain on the wafer to be less than the weight of the wafer to prevent the wafer from deflecting.

[0007] Preferably, the water curtain is in a fan shape, and the included angle θ of the fan shape is 120°.

[0008] Preferably, the cleaning nozzle rotates at an angular velocity ω, and the angular velocity ω and the pre-cleaning time t satisfy the following condition: ω·t≧2π.

[0009] Preferably, when the wafer is a 12-inch wafer, the distance from the nozzle outlet of the cleaning nozzle to the wafer surface is ≧100 mm.

[0010] Preferably, the flow rate of the nozzle outlet is ≦3 m / s.

[0011] Preferably, the driving device comprises a driving motor and a shaft coupling, one end of the shaft coupling is connected to the driving motor, and the other end is connected to the cleaning nozzle.

[0012] Preferably, the driving motor is a high-precision brushless DC motor, and the shaft coupling is a metal bellows coupling.

[0013] Preferably, the cleaning nozzle adopts a centrifugal nozzle structure.

[0014] Preferably, the bearing table in the wafer transmission position sprays an elongated water column when the wafer does not contact, detects whether the wafer exists, and disappears when the wafer is loaded on the bearing table, converts the water pressure rising signal in the bearing table into a voltage signal through a conversion device in the circuit to trigger the driving device.

[0015] Preferably, after the pre-cleaning is completed, the wafer is moved into a cleaning cavity for further cleaning.

[0016] As described above, the method for cleaning a wafer in a polishing cavity provided by the present application has the following beneficial effects: a driving device is installed in the original water spraying base position, and a cleaning nozzle capable of spraying water in a 360-degree rotation is set on the top of the base to work with the driving device, the cleaning nozzle can spray a water curtain covering the diameter of the wafer, which increases the cleaning area of the front surface of the wafer, reduces the cleaning pressure of the cleaning cavity, and prolongs the service life of the consumables, not only reduces the replacement frequency of the cleaning consumables and the production cost, but also reduces the wafer defects and improves the wafer yield. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the description of the embodiments or the prior art. Obviously, the drawings described below are only some of the embodiments of the present application, and all other drawings obtained by those of ordinary skill in the art based on the embodiments of the present application without creative effort are within the scope of protection of the present application.

[0018] Figure 1 A schematic diagram showing the internal structure of the polishing cavity;

[0019] Figure 2 A photo showing the wafer transmission position in the polishing cavity;

[0020] Figure 3 A photo showing the Figure 2 water spraying base in the middle;

[0021] Figure 4 A photo showing the Figure 3 water spraying base in the middle spraying water column to the wafer surface through the cleaning nozzle arranged on the top of the water spraying base and the cleaning area of the wafer by the water column;

[0022] Figure 5 A schematic diagram showing the device for cleaning the wafer in the polishing cavity provided by the embodiments of the present application;

[0023] Figure 6 A schematic diagram showing the Figure 5 moving process of the water curtain sprayed by the device shown in the middle;

[0024] Figure 7 A schematic diagram showing the Figure 5 cleaning area of the wafer surface by the device shown in the middle. DETAILED DESCRIPTION

[0025] The embodiments of the present application will be described below through specific, concrete examples. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in the present specification. The present application can also be implemented or applied through other different specific embodiments, and each detail in the present specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present application.

[0026] The technical solutions in the present application will be described below in a clear and complete manner with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0027] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating positions or location relationships, are used solely to facilitate the description of this application and simplify the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to internal connections between two components; they can refer to wireless connections or wired connections. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0029] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0030] An embodiment of the present application provides a method for cleaning wafers in a grinding chamber, wherein a base with a driving device installed inside is set at the center position of the wafer exit position in the grinding chamber, and a cleaning nozzle that can rotate 360 ​​degrees and spray water in cooperation with the driving device is installed on the top of the base to spray a water curtain covering the diameter of the wafer onto the wafer surface to pre-clean the ground wafer, and the impact force of the water curtain on the wafer is controlled to be smaller than the weight of the wafer itself to prevent the wafer from deflecting.

[0031] like Figure 5 As shown, the driving device provided in the base 10 includes a driving motor 11 and a coupling 12. One end of the coupling 12 is connected to the driving motor 11, and the other end is connected to the cleaning nozzle 20. When the polished wafer (placed on the carrier 30 with the crystal surface 21 facing downward and the crystal back 23 facing upward) is pre-cleaned, the cleaning nozzle 20 sprays a water curtain 22 covering the diameter of the wafer onto the crystal surface 21. During the 360-degree rotation of the cleaning nozzle 20, the movement process of the water curtain 22 is as shown in FIG. Figure 6 As shown, the water curtain 22 rotates 360 degrees around the center of the wafer, and the cleaning effect is as follows: Figure 7 As shown, full surface coverage cleaning is achieved, that is, the cleaning area is the area of ​​the crystal surface 21.

[0032] like Figure 2 As shown, the carrier in the wafer outgoing position sprays a thin stream of water when the wafer is not in contact to detect whether the wafer exists.Figure 5 As shown, when the wafer is loaded on the carrier table 30, the water column disappears, the water pressure inside the carrier table 30 rises, and the water pressure signal is converted into a voltage signal by a conversion device in the circuit to trigger the driving device, and then the cleaning nozzle 20 sprays the water curtain 22 to the wafer surface 21.

[0033] As an example, the driving motor 11 adopts a high-precision brushless DC motor with a rated speed of 600 RPM and a waterproof level of IP67; the shaft coupling 12 adopts a metal bellows coupling to compensate for axial / radial deviation and transmit a torque of ≧0.5 N·m.

[0034] The cleaning nozzle 20 adopts a centrifugal nozzle structure. After the water flow enters the centrifugal nozzle, it rotates at high speed along the annular flow channel and spreads outward under the action of centrifugal force; the guide vanes guide the rotating water flow to a specific angle to form a fan-shaped water curtain 22.

[0035] As shown, in the case where the diffusion angle (fan angle) θ of the water curtain 22 is 120°, the distance R from the nozzle outlet of the cleaning nozzle 20 to the wafer surface 21 of the wafer is determined by the following formula (1): Figure 5

[0036] In order to ensure that the water curtain 22 covers the wafer diameter, taking a 12-inch wafer (diameter of 300 mm) as an example, the projection width D of the water curtain 22 on the wafer surface 21 should be greater than 300 mm, and R≧100 mm is obtained from formula (1). 覆盖

[0037]

[0038] Due to the limitation of the vertical distance between the top of the pedestal and the wafer, if the diffusion angle θ of the water curtain 22 is too small, in order to ensure that the water curtain 22 covers the wafer diameter, it will cause the R value to be too small, which is easy to cause the wafer to deflect; if the diffusion angle θ of the water curtain 22 is too large, a considerable proportion of the water flow on the outside of the water curtain 22 will be sprayed to the back of the wafer at the same time, which is easy to cause the wafer to separate from the carrier table and cause damage to the wafer. After repeated experiments, it is determined that the diffusion angle θ of the water curtain 22 is 120°.

[0039] The cleaning nozzle 20 rotates at an angular velocity ω, and the angular velocity ω and the pre-cleaning time t satisfy the following condition: ω·t≧2π (at least one rotation is completed).

[0040] In order to control the impact force of the water curtain 22 on the wafer to be less than the weight of the wafer itself, taking a 12-inch wafer as an example, the impact force should be less than 0.1 N, and thus the nozzle outlet flow rate of the cleaning nozzle 20 is designed according to the Bernoulli principle: according to the Bernoulli equation P1+ P1: static pressure at the nozzle inlet (Pa), dynamically adjusted by a voltage pump; P2: static pressure at the nozzle outlet (Pa), usually equal to the ambient pressure P0≈101325 Pa; ρ: fluid density (kg / m​​3 ), deionized water density p = 1000 kg / m 3 ; v1: inlet flow rate (m / s), determined by the inlet cross-sectional area A1 and the flow rate Q (v1 = Q / A1); v2: nozzle outlet flow rate (m / s), derived from the continuity equation Q = A1v1 = A2v2 and the Bernoulli equation By increasing the inlet pressure P1, v2 can be increased to enhance the cleaning effect, but it is necessary to ensure that v2≤3 m / s to prevent wafer deflection.

[0041] Compared with the original cleaning method, the cleaning method for wafers in the polishing cavity provided in the application increases the cleaning area of the wafer, realizes full coverage of the wafer area, and has the following advantages:

[0042] First, the water consumption of the original six cleaning nozzles is integrated, the water flow shape of the nozzles is changed, the cleaning area of the wafer front surface is increased, and the formation of wafer defects is reduced.

[0043] Second, the cleaning pressure of the cleaning cavity consumables is reduced, the service life of the consumables is prolonged, the replacement frequency of the cleaning consumables is reduced, and the production cost is reduced.

[0044] Third, the product scrap rate is reduced, the wafer yield is improved, and the product profit margin is improved.

[0045] It should be noted that the diagrams provided in the embodiments only illustrate the basic concept of the application in a schematic manner, and only the components related to the application are shown in the diagrams, not the number, shape and size of the components when actually implemented. The actual implementation of each component may be arbitrarily changed in shape, number and proportion, and the layout pattern of the components may be more complex.

[0046] In summary, the cleaning method for wafers in the polishing cavity provided in the application installs a driving device in the original water spraying base position, and sets a 360-degree rotatable water spraying cleaning nozzle cooperating with the driving device on the top of the base. The cleaning nozzle can spray a water curtain covering the diameter of the wafer, increase the cleaning area of the wafer front surface, reduce the cleaning pressure of the cleaning cavity consumables, prolong the service life of the consumables, not only reduce the replacement frequency of the cleaning consumables and reduce the production cost, but also reduce the wafer defects and improve the wafer yield. Therefore, the application effectively overcomes the various shortcomings in the prior art and has high industrial utilization value.

[0047] The above embodiments are only illustrative of the principles of the present application and its effects, and are not intended to limit the present application. Any modification or change made by any person skilled in the art without departing from the spirit and scope of the present application shall be covered by the claims of the present application.

Claims

1. A method for cleaning a wafer in a grinding chamber, characterized in that: A base with a driving device installed inside is set at the center of the wafer exit position in the grinding chamber, and a cleaning nozzle that can rotate 360 ​​degrees and spray water is installed on the top of the base and works in conjunction with the driving device to spray water curtains covering the diameter of the wafer to pre-clean the wafer after grinding. The impact force of the water curtain on the wafer is controlled to be less than the weight of the wafer itself to prevent the wafer from deflecting.

2. The method according to claim 1, characterized in that The water curtain is fan-shaped, and the fan-shaped angle θ is 120°.

3. The method according to claim 1, characterized in that The cleaning nozzle rotates at an angular velocity ω, and the angular velocity ω and the pre-cleaning time t satisfy the following condition: ω·t≧2π.

4. The method according to claim 1, wherein When the wafer is a 12-inch wafer, the distance from the nozzle outlet of the cleaning nozzle to the crystal surface of the wafer is ≧100 mm.

5. The method according to claim 4, characterized in that The nozzle outlet flow rate is ≤3m / s.

6. The method according to claim 1, characterized in that The driving device includes a driving motor and a coupling, one end of the coupling is connected to the driving motor, and the other end is connected to the cleaning nozzle.

7. The method according to claim 6, characterized in that The driving motor adopts a high-precision brushless DC motor, and the coupling adopts a metal bellows coupling.

8. The method according to claim 1, characterized in that The cleaning nozzle adopts a centrifugal nozzle structure.

9. The method according to claim 1, characterized in that The carrier in the wafer transfer position sprays out a slender water column when the wafer is not in contact to detect whether the wafer exists. When the wafer is loaded on the carrier, the water column disappears, and the energy conversion device in the circuit converts the water pressure increase signal inside the carrier into a voltage signal to trigger the driving device.

10. The method according to claim 1, characterized in that After the pre-cleaning is completed, the wafer is moved into a cleaning chamber for further cleaning.

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