TWI700730B - Wafer cleaning device and method - Google Patents

Abstract

The present invention discloses a device for cleaning packaged wafers. The device includes: a chuck carrying at least two wafers, the at least two wafers are at a distance from the center of the chuck, and the surface of each wafer has multiple Microstructure; a driving device that drives the rotation of the chuck; at least one nozzle that sprays fluid to the wafer to clean or dry the wafer. The present invention also discloses a wafer cleaning method. The method includes: loading at least two wafers on a chuck, the at least two wafers are at a distance from the center of the chuck, and the surface of each wafer has multiple Small structure; drive the chuck to rotate; spray fluid to the wafer to clean or dry the wafer.

Description

Wafer cleaning device and method

The present invention relates to a wafer cleaning device and method, and in particular, to clean the semiconductor structure of the wafer-level package by driving the chuck to alternately rotate at a low speed and a high speed during the cleaning process, so as to remove flux residues more thoroughly and efficiently.

As the size of semiconductor devices becomes smaller and smaller, integrated circuit packaging technology has developed to a new stage. A process method called Wafer Level Packaging (WLP) is applied to package wafers and has a tendency to become one of the mainstream technologies in the microelectronic packaging industry. The WLP process is completely different from the traditional chip packaging process, because in the traditional chip packaging process, the process is divided into several steps, for example, first cut several chip units from the wafer, and then each chip unit is packaged one by one ,test. However, in the WLP process, almost all subsequent steps can be completed at one time, which makes the WLP process more efficient.

The WLP process is more advantageous, but it is challenging to clean the wafer packaged by the WLP process, because the surface of the wafer packaged by the WLP process has many chip units, and there are many tiny chips formed between two adjacent chip units. Structures, such as beams, bridges, gaps, grooves, etc. Therefore, cleaning such wafers is much more complicated than cleaning conventional wafer surfaces. In general, there are two important problems in the complete removal of contaminants from the wafer packaged by the WLP process: (1) The high temperature in the reflow soldering step can easily cause the scorching of the flux and make it difficult to remove the residual flux. (2). The wafer before slicing is essentially an integrated body of flip chip, which is composed of bumps and ball grid arrays. As the size and pattern spacing continue to shrink, the bump structure becomes more fragile This trend of miniaturization and fragility makes the space that can be cleaned between the bump units become narrower, and it also makes it more challenging to clean such a narrow space thoroughly and uniformly.

In order to meet the performance and reliability standards, the packaged wafer must be free of flux, fingerprint contamination, water or other surface contaminants, otherwise these contaminants will lead to ion contamination and corrosion, resulting in insufficient underfill and voids , Causing problems such as moisture concentration, overheating and partial failure.

Therefore, there is a need for an improved cleaning system that can clean contaminants thoroughly and uniformly.

In a specific embodiment of the present invention, a wafer cleaning device is provided. The device includes: a chuck carrying at least two wafers, the at least two wafers being at a distance from the center of the chuck, wherein each wafer There are multiple tiny structures on the surface of the chuck; a driving device that drives the rotation of the chuck; at least one nozzle that sprays fluid to the wafer to clean or dry the wafer; wherein the drive device drives the chuck to alternate between low and high rotation speeds during the cleaning process The low speed N1 is lower than the critical speed, and the high speed is higher than the critical speed. The critical speed is determined by the diameter of the wafer, the shortest distance between the wafer and the center of the chuck, the height of the microstructure on the wafer surface, and the chuck. The rotation time, fluid density and fluid surface tension coefficient are determined.

In a specific embodiment of the present invention, a method for cleaning wafers is provided. The method includes: loading at least two wafers on a chuck, the at least two wafers being at a distance from the center of the chuck, wherein each There are multiple tiny structures on the surface of the wafer; drive the chuck to rotate; spray fluid to the wafer to clean or dry the wafer, where the chuck rotates alternately at low and high speeds during the cleaning process, where the low speed N1 Below the critical speed, the high speed is higher than the critical speed. The critical speed is determined by the diameter of the wafer, the shortest distance between the wafer and the center of the chuck, the height of the microstructure on the wafer surface, the time for the chuck to rotate, the fluid density, and the fluid The surface tension coefficient is determined.

In a specific embodiment of the present invention, another wafer cleaning method is proposed. The method includes: taking out at least two wafers from the wafer cassette and loading the at least two wafers on a chuck located in a process chamber, The at least two wafers are at a distance from the center of the chuck, where each wafer has multiple microstructures on the surface; driving the chuck to rotate; spraying fluid on the wafer to clean or dry the wafer, where the chuck In the cleaning process, it rotates alternately at low and high speeds. Among them, the low speed N1 is lower than the critical speed, and the high speed is higher than the critical speed. The critical speed is determined by the diameter of the wafer and the shortest distance between the wafer and the center of the chuck. , The height of the microstructure on the wafer surface, the time of chuck rotation, the fluid density and the fluid surface tension coefficient are determined.

1000: Wafer

1001: chip unit

1002: surface

1003: tiny structure

2000: installation

2001: Chuck

2002: Drive

2003: nozzle

2004: a nozzle

3000: device

3001: Chuck

3002: drive device

3003: nozzle

3004: nozzles

3005‧‧‧Megasonic device

3006‧‧‧Gas pipeline

4001‧‧‧Chuck

4002‧‧‧Support

4003‧‧‧Locating pin

4004‧‧‧Clamping parts

4005‧‧‧Base

4006‧‧‧Activities Department

4003a‧‧‧Locating pin

4003b‧‧‧Locating pin

9000‧‧‧device

9001‧‧‧Chuck

9002‧‧‧Drive device

9003‧‧‧Nozzle

9004‧‧‧ nozzles

9005‧‧‧Megasonic device

9006‧‧‧Side nozzle

9007‧‧‧ nozzle

1101‧‧‧Chuck

1300‧‧‧Craft cavity

1301‧‧‧Chuck

1302‧‧‧wafer box

Figures 1A-1B are a specific embodiment of a wafer packaged by the WLP process; Figure 2 is a specific embodiment of a wafer cleaning device; Figures 3A-3B are another specific embodiment of a wafer cleaning device; Figure 4A- 4C is a specific embodiment of a chuck that carries a wafer; FIGS. 5A-5B are another specific embodiment of a chuck that carries a wafer; FIGS. 6A-6B are a specific embodiment of a clamping member; A specific embodiment of a positioning pin for fixing a wafer; FIG. 8 is another specific embodiment of a positioning pin for fixing a wafer; FIGS. 9A-9C are another specific embodiment of a wafer cleaning device; 10 is a flowchart of a wafer cleaning method; FIG. 11 illustrates the wafer cleaning method in FIG. 10; FIG. 12 is a flowchart of another wafer cleaning method; FIG. 13 illustrates the wafer cleaning method in FIG.

1A-1B are a specific embodiment of a wafer packaged using the WLP process. FIG. 1A shows a top view of a wafer 1000 packaged using the WLP process, and FIG. 1B shows a cross-sectional view of the wafer 1000 in FIG. 1A. There are many chip units 1001 on the surface 1002 of the wafer 1000 (so-called wafer-level packaged wafer). There are multiple microstructures 1003 between adjacent chip units 1001. The microstructures 1003 include but are not limited to beams, bridges, gaps, Grooves and so on. The wafer unit 1001 usually has a certain height, and the lower case "h" in FIG. 1B is the height of the wafer unit 1001. Due to the complex microstructure 1003, the wafer 1000 packaged by the WLP process is difficult to clean. However, in the following specific embodiments, the present invention will provide a device for cleaning the wafer 1000.

FIG. 2 is a specific embodiment of the wafer cleaning device of the present invention. The device 2000 includes: a chuck 2001 carrying at least two wafers 1000, each wafer 1000 is at a distance from the center of the chuck 2001, and the surface 1002 of each wafer has multiple microstructures 1003; a driving device 2002 and the card The disc 2001 is connected and drives the chuck 2001 to rotate; at least one upper nozzle is used to spray fluid to clean or dry the wafers on the chuck 2001. In one embodiment, the fluid may be deionized water, cleaning fluid, gas or steam. In one embodiment, there are two upper nozzles in FIG. 2, one nozzle 2003 sprays deionized water and cleaning liquid to clean the wafer 1000, and the other nozzle 2004 sprays gas or steam to dry the wafer 1000.

The driving device 2002 drives the chuck 2001 to rotate alternately at low and high speeds during the cleaning process. The low speed N1 is lower than the critical speed, and the high speed is higher than the critical speed. The critical speed is determined by the diameter of the wafer, the wafer and the card. The shortest distance between the center of the disk, the height of the microstructure on the wafer surface, the time of the chuck rotation, the fluid density and the fluid surface tension coefficient are determined.

高轉速Nh高於臨界轉速

；其中，D為晶圓1000的直徑，r為晶圓1000和卡盤2001中心之間的最短距離，h為晶圓1000上的微小結構1003的高度，t為卡盤2001轉動的時間，ρ為流體密度(例如，液體密度)，σ為流體表面張力係數(例如，液體表面張力係數)。 According to a specific embodiment, the low speed N1 is lower than the critical speed

High speed Nh is higher than critical speed

; Among them, D is the diameter of the wafer 1000, r is the shortest distance between the center of the wafer 1000 and the chuck 2001, h is the height of the microstructure 1003 on the wafer 1000, t is the time for the chuck 2001 to rotate, ρ Is the fluid density (for example, liquid density), and σ is the fluid surface tension coefficient (for example, the liquid surface tension coefficient).

In the cleaning process, in order to clean the contaminants thoroughly and uniformly, the rotation speed of the chuck 2001 should be well controlled. In the cleaning process, low and high speeds are alternately applied to the chuck. When using a low speed, the deionized water or cleaning fluid sprayed by the nozzle 2003 can easily flow through the microstructure 1003 and evenly cover the wafer surface 1002. Before the high speed is used, the deionized water or cleaning fluid will be on the wafer surface 1002 stays for a period of time, so that the deionized water or cleaning solution can completely dissolve the pollutants during this period. Furthermore, when a high speed is used, centrifugal force is generated, and the centrifugal force is strong enough to overcome the surface tension of the liquid. The centrifugal force pulls the deionized water or cleaning fluid away from the surface of the wafer 1000, and the contaminants are carried away with the deionized water or cleaning fluid. Therefore, the device 2000 can provide thorough and uniform cleaning of contaminants.

3A-3B are another specific embodiment of the wafer cleaning device. The device 3000 includes: a chuck 3001 carrying at least two wafers 1000, the at least two wafers 1000 are at a distance from the center of the chuck 3001, and each wafer surface 1002 has multiple microstructures 1003; a driving device 3002 and The chuck 3001 is connected and drives the chuck 3001 to rotate; at least one upper nozzle is used to spray fluid to the wafer 1000 to clean or dry the wafer 1000. In one embodiment, the fluid may be deionized water, cleaning fluid, gas or steam. In one embodiment, there are two upper nozzles in FIG. 3, one nozzle 3003 sprays deionized water and cleaning liquid to clean the wafer 1000, and the other nozzle 3004 sprays gas or steam to dry the wafer 1000. The device 3000 also includes at least one ultrasonic or megasonic device 3005 located above the chuck 3001. When the nozzle 3003 sprays deionized water, cleaning liquid, gas or steam to clean the wafer loaded on the chuck 3001, the ultrasonic or megasonic device 3005 can apply ultrasonic or megasonic energy to clean the wafer 1000.

The driving device 3002 drives the chuck 3001 to rotate alternately at low and high speeds during the cleaning process. The low speed N1 is lower than the critical speed, and the high speed is higher than the critical speed. The critical speed is determined by the diameter of the wafer, the wafer and the card. The shortest distance between the center of the disk, the height of the microstructure on the wafer surface, the time of the chuck rotation, the fluid density and the fluid surface tension coefficient are determined.

；高轉速Nh高於臨界轉速

； 其中，D為晶圓1000的直徑，r為晶圓1000和卡盤3001中心之間的最短距離，h為晶圓1000上微小結構1003的高度，t為卡盤3001轉動的時間，ρ為流體密度(例如，液體密度)，σ為流體表面張力係數(例如，液體表面張力係數)。 According to a specific embodiment, the low speed N1 is lower than the critical speed

; High speed Nh is higher than critical speed

; Among them, D is the diameter of the wafer 1000, r is the shortest distance between the center of the wafer 1000 and the chuck 3001, h is the height of the microstructure 1003 on the wafer 1000, t is the rotation time of the chuck 3001, and ρ is Fluid density (for example, liquid density), σ is the fluid surface tension coefficient (for example, liquid surface tension coefficient).

Correspondingly, in a specific embodiment of the present invention, the chuck 3001 carries at least two wafers 1000 through vacuum suction. 4A-4C are a specific embodiment of a chuck 3001 carrying a wafer 1000, FIG. 4A shows a top view of a chuck 3001 holding at least two wafers 1000 through vacuum suction, and FIG. 4B shows no wafers carrying it. A top view of the chuck 3001, and FIG. 4C shows a cross-sectional view of the chuck 3001. The chuck 3001 includes at least two independent gas pipes 3006. Each gas pipe 3006 is used to fix a wafer 1000 on the chuck 3001 through vacuum adsorption. Each gas pipe 3006 is individually controlled and does not affect each other.

Correspondingly, in a specific embodiment of the present invention, another chuck is provided. 5A-5B are another specific embodiment of a chuck carrying a wafer. The chuck 4001 in FIG. 5A has a wafer 1000 fixed on it, and the chuck 4001 in FIG. 5B has no wafer 1000 on it. The chuck 4001 includes at least two sets of support members 4002, and each set of support members 4002 includes a positioning pin 4003 and at least three clamping members 4004 to fix a wafer 1000. One positioning pin 4003 and at least three clamping members 4004 are evenly distributed around the wafer 1000, and the positioning pin 4003 is located closest to the center of the chuck 4001.

Figures 6A-6B are a specific embodiment of the clamping member. The clamping member 4004 includes a base 4005 and a movable part 4006. The movable part 4006 is movably mounted on the base 4005. When an external force is applied to the movable part 4006, the movable part 4006 swings back and forth. When the chuck 4001 rotates, the centrifugal force generated is applied to the movable part 4006 as an external force. In this case, the bottom of the movable part 4006 rises, and the top of the movable part 4006 descends, making the top of the movable part 4006 press the wafer 1000 Under the action of the downward pressure on the surface of the wafer 1000, the wafer 1000 is clamped by the clamping member 4004. On the contrary, if the chuck 4001 remains stationary, the movable part 4006 will remain vertical under the action of gravity, which is convenient for the robot to move the wafer 1000.

FIG. 7 is a specific embodiment of a positioning pin used to fix a wafer. During the rotation of the chuck 4001, the positioning pin 4003 and the clamping member 4004 work together to prevent the wafer 1000 from moving. The shape of the positioning pin 4003 is arbitrary. As shown in FIG. 7 in a specific embodiment of the present invention, the shape of the positioning pin 4003a is a rectangular parallelepiped. As shown in FIG. 8 in another specific embodiment of the present invention, the shape of the positioning pin 4003b is a cylinder.

9A-9C are another specific embodiment of the wafer cleaning device. The device 9000 includes: a chuck 9001 that carries at least two wafers 1000, preferably, the chuck 9001 carries four or six wafers 1000. If the chuck carries too many wafers 1000, the size of the chuck 9001 needs to be large enough to make the chuck 9001 difficult to rotate. Four or six wafers 1000 are at a distance from the center of the chuck 9001, and the surface 1002 of each wafer has multiple microstructures 1003. The driving device 9002 is connected to the chuck 9001 and drives the chuck 9001 to rotate. At least one upper nozzle is used to spray deionized water, cleaning fluid, gas or steam to clean or dry the wafer 1000 carried on the chuck 9001. In one embodiment, there are two upper nozzles in FIG. 9A. One nozzle 9003 sprays deionized water and cleaning liquid to clean the wafer 1000, and the other nozzle 9004 sprays gas or steam to dry the wafer 1000. Nozzle 9003 and nozzle 9004 are located above the chuck 9001. Both nozzles are scanning nozzles or swing nozzles that can rotate around the axis of rotation and spray deionized water, cleaning fluid, gas or steam to different points on the wafer 1000 . In a specific embodiment, the device 9000 further includes at least one side nozzle 9006 located on one side of each wafer 1000. The side nozzle 9006 has a plurality of linearly arranged and parallel nozzles 9007 for spraying fluid to clean or dry the wafer. Round 1000. The device 9000 also includes at least one ultrasonic or megasonic device 9005 located above the chuck 9001. When the nozzle 9003 sprays deionized water, cleaning fluid, gas or steam to clean the wafers loaded on the chuck 9001, the ultrasonic or megasonic The device 9005 can apply ultrasonic or megasonic energy to clean the wafer 1000.

The driving device 9002 drives the chuck 9001 to rotate alternately at low and high speeds during the cleaning process. The low speed N1 is lower than the critical speed, and the high speed is higher than the critical speed. The critical speed is determined by the diameter of the wafer, the wafer and the card. The shortest distance between the center of the disk, the height of the microstructure on the wafer surface, the time of the chuck rotation, the fluid density and the fluid surface tension coefficient are determined.

高轉速Nh高於臨界轉速

； 其中，D為晶圓1000的直徑，r為晶圓1000和卡盤9001中心之間的最短距離，h為晶圓1000上微小結構1003的高度，t為卡盤9001轉動的時間，ρ為流體密度(例如，液體密度)，σ為流體表面張力係數(例如，液體表面張力係數)。 According to a specific embodiment, the low speed N1 is lower than the critical speed

High speed Nh is higher than critical speed

; Among them, D is the diameter of the wafer 1000, r is the shortest distance between the center of the wafer 1000 and the chuck 9001, h is the height of the microstructure 1003 on the wafer 1000, t is the rotation time of the chuck 9001, and ρ is Fluid density (for example, liquid density), σ is the fluid surface tension coefficient (for example, liquid surface tension coefficient).

其中，t為卡盤9001的轉動時間，ρ為流體密度，σ為流體表面張力係數。 During the cleaning process, the speed must be high enough to generate centrifugal force to overcome the surface tension of the liquid, which will cause radial centripetal acceleration. According to Newton's second law, the following formula can be obtained: Fc - Fs = mac (1); Among them, F _c is the centrifugal force, F _s is the liquid surface tension, m is the liquid quality, and a _c is the centripetal acceleration. 9C, D is the diameter of the wafer 1000, r is the shortest distance between the center of the wafer 1000 and the chuck 9001, h is the height of the microstructure 1003 on the wafer 1000, and ω is the angular velocity of the chuck 9001. According to formula (1), the critical speed N can be calculated:

Among them, t is the rotation time of the chuck 9001, ρ is the fluid density, and σ is the fluid surface tension coefficient.

In a specific embodiment, the rotation time t=1s, the diameter of the wafer A=B=300mm, the height of the microstructure 1003 h=40μm, the shortest distance between the center of the wafer 1000 and the chuck 9001 r=100mm, and the liquid It is deionized water with density ρ=1000kg/m ³ , and the liquid surface tension coefficient of deionized water at 20°C is σ=0.0727N/m, so the critical speed is N=1181RPM.

Fig. 10 is a flowchart of a wafer cleaning method. Figure 11 illustrates the wafer cleaning method in Figure 10. According to the above specific embodiments, the wafer cleaning method can be set as follows: Process steps: Step 1: Load at least two wafers 1000 on the chuck 1101, the at least two wafers 1000 are at a distance from the center of the chuck 1101, There are multiple tiny structures 1003 on the surface 1002 of each wafer 1000; Step 2: Drive the chuck 1101 to rotate; Step 3: Spray fluid to the wafer 1000 to clean or dry the wafer 1000; Among them, during the cleaning process, the chuck 1101 rotates alternately at low and high speeds. Among them, the low speed N1 is lower than the critical speed, and the high speed is higher than the critical speed. Among them, the critical speed is determined by the diameter of the wafer 1000, the center of the wafer 1000 and the chuck 1101. The shortest distance, the height of the microstructure on the wafer surface, the time of chuck rotation, the fluid density and the fluid surface tension coefficient are determined.

According to a specific embodiment, the critical speed is:

Among them, D is the diameter of the wafer, r is the shortest distance between the wafer and the center of the chuck, h is the height of the microstructure on the wafer, t is the time for the chuck to rotate, ρ is the fluid density, and σ is the fluid surface Tension coefficient.

In a specific embodiment, the method further includes the following steps: when spraying fluid onto the wafer surface 1002, cleaning the wafer 1000 with ultrasonic or megasonic energy; the fluid sprayed through at least one nozzle includes deionized water, cleaning fluid, and gas. Or steam.

Figure 12 is a flowchart of another wafer cleaning method. FIG. 13 illustrates the wafer cleaning method in FIG. 12. According to the above specific embodiments, another wafer cleaning method can be set as follows: Process steps: Step 1: Take out at least two wafers 1000 from the wafer cassette 1302 and load the wafers 1000 on the chuck located in the process chamber 1300 On 1301, the at least two wafers 1000 are at a distance from the center of the chuck 1301, and the surface 1002 of each wafer 1000 has a plurality of microstructures 1003; Step 2: Drive the chuck 1301 to rotate; Step 3: Move to the wafer 1000 spray fluid to clean or dry the wafer 1000; wherein, during the cleaning process, the chuck 1301 rotates alternately at low and high speeds, where the low speed N1 is lower than the critical speed, and the high speed is higher than the critical speed; among them, The critical speed is determined by the diameter of the wafer 1000, the shortest distance between the center of the wafer 1000 and the chuck 1301, the height of the microstructure 1003 on the surface of the wafer 1002, the rotation time of the chuck, the fluid density and the fluid surface tension coefficient.

According to a specific embodiment, the critical speed is:

Where D is the diameter of the wafer 1000, r is the shortest distance between the center of the wafer 1000 and the chuck 1301, h is the height of the microstructure 1003 on the wafer 1000, t is the rotation time of the chuck 1301, and ρ is the fluid Density and σ are the fluid surface tension coefficient.

In a specific embodiment, the method further includes the following steps: when spraying fluid on the surface of the wafer, using ultrasonic or megasonic energy to clean the wafer; the fluid sprayed through at least one nozzle includes deionized water, cleaning liquid, gas or steam .

Although the present invention is illustrated by specific embodiments, examples, and applications, obvious modifications and replacements in the art will still fall within the protection scope of the present invention.

1000‧‧‧wafer

2000‧‧‧device

2001‧‧‧Chuck

2002‧‧‧Drive

2003‧‧‧Nozzle

2004‧‧‧ nozzles

Claims (21)

A wafer cleaning device, characterized by comprising: a chuck for carrying at least two wafers, the at least two wafers are at a distance from the center of the chuck, and a plurality of microstructures are provided on the surface of each wafer; The drive device drives the chuck to rotate; at least one nozzle sprays fluid to the wafer to clean or dry the wafer; wherein the drive device drives the chuck to rotate alternately at low and high speeds during the cleaning process, where the low speed N1 Below the critical speed, the high speed is higher than the critical speed; among them, the critical speed is determined by the diameter of the wafer, the shortest distance between the wafer and the center of the chuck, the height of the microstructure on the wafer surface, the time for the chuck to rotate, and the fluid density. And the fluid surface tension coefficient is determined. The device according to claim 1, characterized in that the critical speed can be defined as:

Among them, D is the diameter of the wafer, r is the shortest distance between the wafer and the center of the chuck, h is the height of the microstructure on the wafer, t is the time for the chuck to rotate, ρ is the fluid density, and σ is the fluid surface Tension coefficient. The device according to claim 1, wherein the fluid sprayed through the at least one nozzle is deionized water, cleaning liquid, gas or steam. The device according to claim 1, wherein the chuck includes at least two sets of support members, and each set of support members includes a positioning pin and at least three clamping members to fix a wafer. The device according to claim 4, characterized in that, for each group of support members, one positioning pin and at least three clamping members are evenly distributed around the wafer, and the positioning pin is located closest to the center of the chuck. The device according to claim 4, wherein the clamping member includes a base and a movable part, the movable part is movably mounted on the base, and the movable part swings back and forth when receiving an external force. The device according to claim 1, wherein the chuck fixes at least two wafers through vacuum suction. The device according to claim 1, wherein the chuck includes at least two independent gas pipes, and each gas pipe is used to fix a wafer on the chuck through vacuum adsorption. The device according to claim 1, wherein the micro structure includes a beam, a bridge, a gap or a groove. The device according to claim 1, wherein the wafer is a wafer-level packaged wafer. The device according to claim 1, wherein the chuck carries four or six wafers. The device according to claim 1, wherein the nozzle is installed above the chuck. The device according to claim 1, further comprising an upper nozzle located above the chuck, the upper nozzle being a scanning nozzle or a swinging nozzle. The device according to claim 1, further comprising at least one side nozzle located on one side of each wafer, and the side nozzle has a plurality of linearly arranged and parallel nozzles for spraying fluid to clean or dry the wafer. round. The device according to claim 1, characterized in that it further comprises at least one ultrasonic or megasonic device located above the chuck for cleaning wafers. A wafer cleaning method, characterized in that it comprises: loading at least two wafers on a chuck, the at least two wafers are at a distance from the center of the chuck, and the surface of each wafer has a plurality of microstructures; Drive the chuck to rotate; spray fluid to the wafer to clean or dry the wafer; wherein, during the cleaning process, the chuck rotates alternately at low and high speeds, where the low speed N1 is lower than the critical speed, and the high speed is higher than Critical speed: Among them, the critical speed is determined by the diameter of the wafer, the shortest distance between the wafer and the center of the chuck, the height of the microstructure on the wafer surface, the rotation time of the chuck, the fluid density and the fluid surface tension coefficient. The method according to claim 16, characterized in that the critical speed is defined as:

Among them, D is the diameter of the wafer, r is the shortest distance between the wafer and the center of the chuck, h is the height of the microstructure on the wafer, t is the time for the chuck to rotate, ρ is the fluid density, and σ is the fluid surface Tension coefficient. The method according to claim 16, further comprising the steps of: cleaning the wafer with ultrasonic or megasonic energy when spraying fluid on the surface of the wafer; the fluid sprayed through at least one nozzle includes deionized water, cleaning fluid , Gas or steam. A wafer cleaning method, characterized by comprising: taking out at least two wafers from a wafer cassette and loading the wafers on a chuck located in a process chamber, the at least two wafers and the center of the chuck At a certain distance, there are multiple tiny structures on the surface of each wafer; drive the chuck to rotate; spray fluid to the wafer to clean or dry the wafer; where, during the cleaning process, the chuck rotates alternately at low and high speeds Among them, the low speed N1 is lower than the critical speed, and the high speed is higher than the critical speed. The critical speed is determined by the diameter of the wafer, the shortest distance between the wafer and the center of the chuck, the height of the microstructure on the wafer surface, and the chuck. The rotation time, fluid density and fluid surface tension coefficient are determined. The method according to claim 19, characterized in that the critical speed is defined as:

Among them, D is the diameter of the wafer, r is the shortest distance between the wafer and the center of the chuck, h is the height of the microstructure on the wafer, t is the time for the chuck to rotate, ρ is the fluid density, and σ is the fluid surface Tension coefficient. The method according to claim 19, further comprising the following steps: when spraying fluid on the surface of the wafer, cleaning the wafer with ultrasonic or megasonic energy; and the fluid sprayed through at least one nozzle includes deionized water, cleaning liquid , Gas or steam.

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