Wafer cleaning method based on droplet impact

Abstract

A wafer cleaning method based on droplet impact. The method comprises: during the rotation of a wafer, spraying a first cleaning solution onto the surface of the wafer to form a continuous liquid film, such that contaminants are desorbed from the surface of the wafer into the liquid film; and continuously dripping, onto the surface of the wafer, droplets formed from a second cleaning solution, such that the contaminants within the liquid film are dislodged by the continuous impact of the droplets, and leave the wafer as the liquid film flows, wherein the diameters of the droplets range from 14 microns to 30 microns. In the method, during cleaning, droplets, which have diameters ranging from 14 microns to 30 microns and are formed from a second cleaning solution, are continuously dripped onto the surface of a wafer, such that contaminants within a liquid film, especially small-diameter contaminants at the bottom of the liquid film, are dislodged by the impact of the droplets, thereby leaving the wafer as the liquid film flows. By means of the method, damage to micro-patterns on the surface of a wafer caused by the way in which a cleaning solution is sprayed by using a large amount of high-pressure nitrogen in the prior art is prevented. The method is applicable to the cleaning of wafers with a size of 14 nm or below.

Description

Wafer cleaning method based on droplet impact Technical Field

[0001] The present invention belongs to the technical field of semiconductor cleaning, and in particular relates to a wafer cleaning method based on droplet impact. Background Art

[0002] If the wafer is contaminated by dust particles or metal during the manufacturing process, it can easily damage the internal circuit function of the chip, causing short circuits or open circuits, leading to failure of the integrated circuit. Therefore, in addition to eliminating external sources of contamination, wet cleaning or dry cleaning is required before processes such as high-temperature diffusion and ion implantation.

[0003] Wet cleaning refers to the process of using various chemical reagents to react or dissolve impurities and oil stains adsorbed on the surface of the object to be cleaned, so that the impurities are desorbed (desorbed) from the surface of the object to be cleaned, and then rinsed to obtain a clean surface.

[0004] During rinsing, high-pressure, high-flow nitrogen gas is used to atomize and spray the cleaning liquid across the wafer surface. This method provides excellent cleaning results with minimal wafer damage, meeting the cleaning requirements for wafers larger than 28nm. However, for wafers smaller than 14nm, the surface patterns become more complex and fragile, and existing methods can easily damage these patterns.

[0005] Summary of the Invention

[0006] Based on this, in order to solve the above technical problems, a wafer cleaning method based on droplet impact is provided.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] The present invention provides a wafer cleaning method based on droplet impact, comprising:

[0009] During the wafer rotation process, a first cleaning liquid is sprayed onto the surface of the wafer to form a continuous liquid film, so that pollutants are desorbed from the surface of the wafer into the liquid film;

[0010] Droplets of the second cleaning liquid are continuously dripped onto the surface of the wafer. The continuous impact of the droplets lifts up the pollutants inside the liquid film and separates from the wafer with the flow of the liquid film. The diameter of the droplets is 14-30 microns.

[0011] During cleaning, the present invention continuously drips droplets of 14-30 microns in diameter formed by the second cleaning liquid onto the surface of the wafer. The impact of the droplets lifts up pollutants inside the liquid film, especially small-diameter pollutants located at the bottom of the liquid film, and then separates from the wafer with the flow of the liquid film. This avoids the damage to micro-patterns on the wafer surface caused by the existing method of spraying cleaning liquid with a large amount of high-pressure nitrogen gas. The invention is suitable for cleaning applications of wafers of 14nm and below. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG1 is a flow chart of the present invention;

[0013] FIG2 is a schematic structural diagram of a nozzle of the present invention;

[0014] FIG3 is a schematic diagram of the nozzle of the present invention. DETAILED DESCRIPTION

[0015] The following will illustrate the implementation of the present invention in conjunction with the drawings in the specification. It should be noted that the implementation methods involved in this specification are not exhaustive and do not represent the only implementation methods of the present invention. The following corresponding embodiments are only for the purpose of clearly illustrating the invention content of the patent of this invention and are not intended to limit its implementation methods. For ordinary technicians in this field, different forms of changes and modifications can be made based on the description of this embodiment. Any obvious changes or modifications that belong to the technical concept and invention content of the present invention are also within the scope of protection of the present invention.

[0016] As shown in Figure 1, the embodiment of the present application provides a wafer cleaning method based on droplet impact, which is used to clean wafers of 14nm and below. For wafers of 14nm and below, the graphic structure on its surface becomes more complex and more fragile, with a high graphic density and a small size, which poses a higher challenge to the cleaning process. Protecting the graphic from damage is the most basic requirement of the cleaning process. The specific process of the embodiment of the present application is as follows:

[0017] S101 . During wafer rotation, spray a first cleaning liquid onto the surface of the wafer to form a continuous liquid film, so that pollutants inside the liquid film are desorbed from the wafer surface into the liquid film.

[0018] S102 , continuously dripping droplets formed by the second cleaning liquid onto the surface of the wafer, so that the contaminants inside the liquid film are lifted up by the continuous impact of the droplets and separated from the wafer with the flow of the liquid film.

[0019] It should be pointed out that during the rotation of the wafer, the flow rate of the top layer of the liquid film is the largest, and the flow rate decreases as it is farther away from the top layer. The bottom layer can be considered stationary. On this basis, due to the large volume of large-diameter contaminants, they can be separated from the wafer with the flow of the liquid film, while small-diameter contaminants, especially those located at the bottom layer of the liquid film that are close to stationary, are difficult to separate from the wafer. Therefore, in the embodiment of the present application, by continuously dripping droplets into the interior of the liquid film, the interior of the liquid film is impacted, so that the contaminants inside the liquid film, especially the small-diameter contaminants located at the bottom layer of the liquid film, are lifted up, and thus separated from the wafer with the flow of the liquid film. The droplets falling into the liquid film will not cause an impact on the micro-image on the wafer surface, and will not damage the micro-pattern on the wafer surface.

[0020] The diameter of the droplets is 14-30 microns, and the second cleaning liquid is squeezed by continuous vibration force to form uniform and controllable droplets through the dripping holes on the nozzle.

[0021] Specifically, as shown in Figures 2 and 3, the nozzle includes a nozzle body 110, which has a flow channel 111 therein, and the nozzle body 110 has a liquid inlet 112, a liquid outlet 113, a mounting cavity 114 and a plurality of drip holes 115 located on its lower end surface.

[0022] The flow channel 111 is a flat sandwich.

[0023] Illustratively, the vertical cross-section of the flow channel 111 may be U-shaped, having a horizontal section 111 a passing horizontally through the lower end of the nozzle body 110 , and the horizontal section 111 a is connected to the plurality of drip holes 115 , as shown in FIG. 3 .

[0024] As shown in FIG. 2 , the liquid inlet 112 and the liquid outlet 113 are both located on the upper end surface of the nozzle body 110 and are connected to the two ends of the flow channel 111 respectively.

[0025] As shown in Figure 3, the installation cavity 114 is located on the upper side of the horizontal section 111a, and a vibration source 120 is provided therein. The vibration source 120 is used to apply continuous vibration force on the upper side of the horizontal section 111a, and squeeze the second cleaning liquid 3 flowing through the horizontal section 111a through the vibration force, so that the second cleaning liquid 3 forms droplets 4 through the drip hole 115. Exemplarily, the installation cavity 114 can be a blind hole extending downward from the upper surface of the nozzle body 110 to the horizontal section 111a, and the blind hole is concentric with the nozzle body 110. The vibration source 120 can be a piezoelectric ceramic vibrator of an external frequency generator 2 (such as an ultrasonic generator), which converts the electrical signal of the frequency generator 2 into a continuous vibration force.

[0026] The diameter of the drip hole 115 is 6-30 microns. It is a tapered hole with a radius that gradually decreases from top to bottom, so as to increase the liquid flow rate. Multiple drip holes 115 can be arranged in a circular array.

[0027] In order to ensure that the nozzle is in a clean environment, the nozzle is immersed in a sink of deionized water when it is not working. Before cleaning, after removing the nozzle from the sink, the surface tension will cause the residual liquid to cover the multiple drip holes 115 on the lower surface of the nozzle, resulting in the inability of each drip hole 115 to independently form droplets during cleaning. Therefore, it is necessary to first purge and dry the lower surface of the nozzle with nitrogen or inert gas to dry the liquid remaining on the lower surface of the nozzle. After the cleaning work is completed, the nozzle is immersed in the deionized water in the sink again.

[0028] The first cleaning liquid is a conventional cleaning liquid, such as deionized water or SC1 (a mixture of ammonia, hydrogen peroxide and water), the second cleaning liquid is deionized water or diluted SC1, and the nozzle is made of a material compatible with the second cleaning liquid, such as quartz or plastic.

[0029] As can be seen from the above, during cleaning, the embodiment of the present application continuously drips droplets with a diameter of 14-30 microns formed by the second cleaning liquid onto the surface of the wafer. Through the impact of the droplets, the pollutants inside the liquid film, especially the small-diameter pollutants located at the bottom of the liquid film, are lifted up and then separated from the wafer with the flow of the liquid film, avoiding the damage to the micro-patterns on the wafer surface caused by the method of spraying a large amount of high-pressure nitrogen gas to clean the liquid in the prior art. It is suitable for cleaning applications of wafers of 14nm and below.

[0030] Obviously, those skilled in the art should realize that the above embodiments are only used to illustrate the present invention and are not used to limit the present invention. As long as they are within the scope of the essence of the present invention, any changes and modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A wafer cleaning method based on droplet impact, characterized in that, Including: During the rotation of the wafer, a first cleaning liquid is sprayed onto the surface of the wafer to form a continuous liquid film, so that contaminants are desorbed from the surface of the wafer into the liquid film; Liquid droplets formed by a second cleaning liquid are continuously dripped onto the surface of the wafer. Due to the continuous impact of the liquid droplets, the contaminants inside the liquid film are lifted up and separated from the wafer along with the flow of the liquid film. The diameter of the liquid droplets is 14 - 30 microns.

2. The wafer cleaning method based on droplet impact according to claim 1, wherein, The continuously dripping of the liquid droplets formed by the second cleaning liquid onto the surface of the wafer further includes: The second cleaning liquid is extruded by a continuous vibration force so that the liquid droplets are formed through the droplet holes on the nozzle.

3. The wafer cleaning method based on droplet impact according to claim 2, characterized in that, The nozzle includes a nozzle body. A flow channel is provided inside the nozzle body. The nozzle body is provided with a liquid inlet, a liquid outlet and an installation cavity. The flow channel has a horizontal section that passes horizontally through the inside of the lower end of the nozzle body. The liquid inlet and the liquid outlet are respectively connected to both ends of the flow channel. The installation cavity is located above the horizontal section. A vibration source for applying the continuous vibration force above the horizontal section is provided in the installation cavity. A plurality of droplet holes communicating with the horizontal section are formed on the lower end surface of the nozzle body. The diameter of the droplet holes is 6 - 30 microns.

4. A wafer cleaning method based on droplet impact according to claim 3, characterized in that The droplet holes are conical holes with a gradually decreasing radius from top to bottom.

5. A wafer cleaning method based on droplet impact according to claim 3, characterized in that, The vertical cross-section of the flow channel is U-shaped. Both the liquid inlet and the liquid outlet are located on the upper end surface of the nozzle body.

6. The wafer cleaning method based on droplet impact according to claim 3, characterized in that, The flow channel is a flat sandwich.

7. A wafer cleaning method based on droplet impact according to claim 3, characterized in that The installation cavity is a blind hole extending downward from the upper surface of the nozzle body to the horizontal section, and the blind hole is concentric with the nozzle body.

8. A wafer cleaning method based on droplet impact according to claim 3, wherein The vibration source uses a piezoelectric ceramic vibrating part connected to an external frequency generator.

9. A wafer cleaning method based on droplet impact according to any one of claims 3-8, characterized in that It further includes: Before the cleaning work, the nozzle is taken out of the water tank, and its lower surface is purged and dried with nitrogen or inert gas; After the cleaning work is completed, the nozzle is immersed in the deionized water in the water tank.

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