Method for improving wafer surface pit problem

Abstract

The invention discloses a method for improving a wafer surface pit problem, and the method comprises the steps: S1, providing a wafer which is subjected to a passivation layer etching process, and cleaning the wafer through a cleaning solution; s2, spraying deionized water to the wafer by using a nozzle, and rotating the wafer at a first rotating speed; s3, deionized water is sprayed to the wafer through a nozzle, meanwhile, the wafer is rotated at a second rotating speed, and the second rotating speed is slightly larger than the first rotating speed; s4, deionized water is sprayed to the wafer through a nozzle, meanwhile, the wafer is rotated at a third rotating speed, and the third rotating speed is far larger than the second rotating speed; wherein the first rotating speed ranges from 15 RPM to 25 RPM, the second rotating speed ranges from 40 RPM to 60 RPM, and the third rotating speed ranges from 800 RPM to 1000 RPM. According to the scheme, the problem that pits appear on the surface of the wafer in the prior art can be solved.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor manufacturing, and in particular to a method for improving the problem of pits on the surface of a wafer. Background Art

[0002] The passivation layer is the last step in the wafer manufacturing process and is used to protect the entire chip. The traditional passivation layer structure includes a silicon nitride layer, an oxide layer, a titanium nitride layer, and an aluminum layer from top to bottom.

[0003] For subsequent packaging, a passivation layer etching process is required to expose the bottom aluminum layer. Passivation layer etching generally uses a capacitively coupled plasma machine and adopts CxFy gas as the etching gas. Especially when etching the titanium nitride layer on the surface of the aluminum layer, since CxFy gas has no chemical reaction with the metal, it can only rely on high bias voltage to increase the intensity of the plasma to etch the titanium nitride layer, while ensuring sufficient over-etching. This will lead to the formation of a large amount of titanium nitride / fluorine-containing polymers, which poses new challenges for the cleaning of the polymer after etching. Traditional processes often use hydrofluoric acid with strong cleaning ability as the cleaning solution after passivation layer etching, but hydrofluoric acid has strong corrosiveness and often forms pits and other defects on the surface of the aluminum layer, such as Figure 1 shown. Summary of the Invention

[0004] In order to solve the above problems, the present application provides a method for improving the problem of pits on the wafer surface.

[0005] The present invention provides a method for improving the problem of wafer surface pits, including: S1: providing a wafer that has undergone a passivation layer etching process, and cleaning the wafer using a cleaning solution; S2: spraying deionized water onto the wafer using a nozzle while rotating the wafer at a first rotation speed; S3: spraying deionized water onto the wafer using a nozzle while rotating the wafer at a second rotational speed, the second rotational speed being greater than the first rotational speed; S4: using a nozzle to spray deionized water onto the wafer, while rotating the wafer at a third rotational speed, wherein the third rotational speed is greater than the second rotational speed.

[0006] In some embodiments, the cleaning fluid is a hydrofluoric acid solution.

[0007] In some embodiments, in step S1, the cleaning time of the cleaning solution is 60 seconds.

[0008] In some embodiments, the duration of step S2 is 6 to 10 seconds.

[0009] In some embodiments, the duration of step S3 is 6-10s.

[0010] In some embodiments, the duration of step S4 is 6-10s.

[0011] In some embodiments, the first rotation speed is 15-25 RPM, the second rotation speed is 40-60 RPM, and the third rotation speed is 800-1000 RPM.

[0012] In some embodiments, after step S4, the method further comprises: S5: atomizing the deionized water in the nozzle using N2; S6: drying the wafer surface using nitrogen.

[0013] The technical solution of the present application has at least the following advantages: 1. The surface of the wafer treated by the cleaning solution has strong hydrophobicity. In the present application, the wafer is first cleaned at a low first rotation speed using deionized water to form a liquid film on the wafer surface, which can effectively remove the residual cleaning solution on the wafer surface. Then, the rotation speed of the wafer is increased to a second rotation speed slightly greater than the first rotation speed, so that the liquid film on the wafer surface moves to the edge of the wafer. Finally, the rotation speed of the wafer is increased to a third rotation speed much greater than the second rotation speed, so that the deionized water containing residual cleaning solution is thrown out of the wafer surface, achieving cleaning of the residual cleaning solution on the wafer surface and avoiding the formation of pits on the wafer surface caused by the cleaning solution. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed in the description of the specific embodiments or the prior art. Obviously, the drawings described below are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0015] Figure 1 is a schematic diagram of a wafer surface with pit defects provided in the background art of the present application.

[0016] Figure 2 is a flowchart of a method for improving the pit problem of a wafer surface provided by an exemplary embodiment of the present application.

[0017] Figure 3 is a schematic diagram for showing the relative position relationship between the nozzle and the wafer provided by an exemplary embodiment of the present application.

[0018] Figure 4is a schematic diagram of a wafer surface obtained after the method for improving the wafer surface pit problem provided by an exemplary embodiment of the present application is implemented. DETAILED DESCRIPTION

[0019] The technical solutions in the present application will be clearly and completely described in combination with 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 in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the scope of the present application.

[0020] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0021] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements, it can be wireless connection, or it can be wired connection. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0022] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0023] The present application provides a method for improving the wafer surface pit problem, referring to Figure 2 The method comprises: S1: providing a wafer subjected to a passivation layer etching process, and cleaning the wafer using a cleaning liquid.

[0024] Exemplarily, the wafer subjected to the passivation layer etching process is placed into a process chamber of a cleaning machine after being offline, and the wafer is placed on a rotatable platform in the process chamber, and a nozzle is arranged above the wafer, as shown in Figure 3 The wafer can include a substrate and an aluminum layer formed on the substrate.

[0025] The cleaning liquid is a hydrofluoric acid (HF) solution.

[0026] Further, the duration of this step can be 60 s, which can be adjusted according to the cleaning effect.

[0027] S2: spray deionized water to the wafer using the nozzle while rotating the wafer at a first rotation speed.

[0028] For example, referring to the figure, deionized water is sprayed to the wafer through the nozzle, so as to remove the cleaning liquid residue on the wafer surface. In this process, the wafer rotates at the first rotation speed under the driving of the platform.

[0029] The first rotation speed can be 15-25 RPM, for example, 20 RPM. At this rotation speed, the deionized water mixed with the removed cleaning liquid residue on the wafer surface will form a water film and cover the wafer surface.

[0030] Further, the duration of this step can be 6-10 s, for example, 8 s.

[0031] S3: spray deionized water to the wafer using the nozzle while rotating the wafer at a second rotation speed, which is slightly greater than the first rotation speed.

[0032] For example, the nozzle continues to spray deionized water to the wafer, and the rotation speed of the wafer is slightly increased, so that the wafer rotates at the second rotation speed. Through the implementation of this step, the liquid film formed on the wafer surface will be thrown to the edge of the wafer.

[0033] The second rotation speed can be 40-60 RPM, for example, 50 RPM.

[0034] Further, the duration of this step can be 6-10 s, for example, 8 s.

[0035] S4: spray deionized water to the wafer using the nozzle while rotating the wafer at a third rotation speed, which is much greater than the second rotation speed.

[0036] For example, the nozzle continues to spray deionized water to the wafer, and the rotation speed of the wafer is greatly increased, so that the wafer rotates at the third rotation speed. Through the implementation of this step, the liquid film that has been on the edge of the wafer will be thrown out of the wafer surface, thereby achieving cleaning of the cleaning liquid residue and reducing the possibility of the remaining cleaning liquid corroding the aluminum layer on the wafer surface and forming pits, as shown in the wafer surface image in Figure 4 .

[0037] The third rotation speed can be 800-1000 RPM, for example, 800 RPM.

[0038] Further, the duration of this step can be 6-10 s, for example, 8 s.

[0039] Further, after step S4, the following process can also be included: S5: atomize the deionized water in the nozzle using N2.

[0040] For example, the nozzle stops spraying deionized water, and instead, nitrogen gas is introduced into the pipe of the nozzle, so that the deionized water remaining in the pipe and the nozzle is atomized by the nitrogen gas.

[0041] S6: dry the wafer surface using nitrogen gas.

[0042] For example, the nozzle continues to spray nitrogen gas onto the wafer surface, and in the process, the nozzle moves above the wafer in a direction parallel to the wafer surface. In the process, the platform simultaneously drives the wafer to rotate at a high speed, thereby achieving the drying process of the wafer surface.

[0043] In this step, the rotation speed of the wafer can be 1500 RPM.

[0044] The method for improving the problem of pits on the wafer surface provided by the embodiments of the present application utilizes the fact that the surface of the wafer treated by the cleaning solution has strong hydrophobicity. By first using deionized water to clean the wafer at a first rotation speed, a liquid film composed of deionized water and residual cleaning solution can be formed on the wafer surface, thereby effectively removing the residual cleaning solution on the wafer surface. Then, the rotation speed of the wafer is increased to a second rotation speed slightly greater than the first rotation speed, so that the liquid film on the wafer surface moves to the edge of the wafer. Finally, the rotation speed of the wafer is increased to a third rotation speed much greater than the second rotation speed, so that the deionized water containing residual cleaning solution is thrown off the wafer surface, thereby cleaning the residual cleaning solution on the wafer surface and avoiding pits caused by the cleaning solution on the wafer surface.

[0045] Obviously, the above embodiments are merely examples for clear illustration, and are not intended to limit the embodiments. Based on the above description, other different forms of changes or variations can be made by those of ordinary skill in the art. Here, it is not necessary and impossible to enumerate all the embodiments. The changes or variations derived therefrom are still within the scope of protection of the present application.

Claims

1. A method for improving the problem of pits on the wafer surface, characterized in that: include: S1: providing a wafer that has undergone a passivation layer etching process, and cleaning the wafer using a cleaning solution; S2: spraying deionized water onto the wafer using a nozzle while rotating the wafer at a first rotation speed; S3: spraying deionized water onto the wafer using a nozzle while rotating the wafer at a second rotational speed, the second rotational speed being slightly greater than the first rotational speed; S4: spraying deionized water onto the wafer using a nozzle while rotating the wafer at a third speed, the third speed being much greater than the second speed; The first speed is 15-25 RPM, the second speed is 40-60 RPM, and the third speed is 800-1000 RPM.

2. The method for improving the wafer surface pit problem according to claim 1, characterized in that: The cleaning liquid is a hydrofluoric acid solution.

3. The method for improving the wafer surface pit problem according to claim 1, wherein: In step S1, the cleaning time of the cleaning liquid is 60 seconds.

4. The method for improving the wafer surface pit problem according to claim 1, wherein: The duration of step S2 is 6 to 10 seconds.

5. The method for improving the wafer surface pit problem according to claim 1, wherein: The duration of step S3 is 6 to 10 seconds.

6. The method for improving the wafer surface pit problem according to claim 1, wherein: The duration of step S4 is 6 to 10 seconds.

7. The method for improving the wafer surface pit problem according to claim 1, wherein: After step S4, the method further includes: S5: using N2 to atomize the deionized water in the nozzle; S6: Drying the wafer surface using nitrogen.

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