Wafer cleaning method
By using a solution with low hydrogen ions and hydroxide ions concentration to form an isolation film before wafer cleaning, the problem of water etching is solved, key sizes are protected, and the wafer cleaning effect and product quality are improved.
Patent Information
- Application Number
- CN202510572490.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-30
- Publication Date
- 2025-08-08
AI Technical Summary
In the existing wafer cleaning methods, hydrogen ions and hydroxide ions in water cause etching on the silicon surface, resulting in key dimension changes and affecting device performance.
The first cleaning is performed using a first solution with a concentration of hydrogen ions and hydroxide ions lower than that of deionized water to form an isolation film, and then a second cleaning is performed with deionized water. The isolation film reduces the etching effect of hydrogen ions and hydroxide ions on the wafer surface.
Reduces etching of exposed materials on wafer surfaces during deionized water cleaning, protects critical sizes, and improves product performance and yield.
Smart Images
Figure CN120453157A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for manufacturing a semiconductor integrated circuit, in particular to a wafer cleaning method. Background Art
[0002] During integrated circuit manufacturing, wet cleaning processes are often required to clean the wafer surface to remove byproducts or surface particles from previous steps. However, during the wafer cleaning process, the exposed structure and film quality may react with the chemical solution, causing surface changes or etching.
[0003] Take a structure that is actually encountered as an example: Figure 1 FIG. 1 is a schematic diagram showing the effect of an existing wafer cleaning method on the etching of silicon exposed on the wafer surface on the critical dimensions of silicon patterns; Figure 1 In the embodiment, the wafer includes a semiconductor substrate 101 such as a silicon substrate, and a first pattern structure 102 is formed on the semiconductor substrate 101 by patterning and etching the semiconductor substrate 101. Figure 1 , a schematic diagram of a cross-sectional view of the first graphic structure 102 is shown in FIG. , where the width of the first graphic structure 102 is a critical dimension (CD); shallow trench isolations 103 are formed on both sides of the first graphic structure 102 .
[0004] Figure 1 In the structure shown, there is an exposed silicon surface. When the existing wafer cleaning method is used for cleaning, it is found that only water cleaning will still cause etching on the exposed silicon surface, resulting in changes in the CD of the silicon, that is, the CD of the first graphic structure 102. Figure 1 When the critical dimension of the first pattern structure 101 is small, such as tens of nanometers, the wafer cleaning method will have a significant impact on the critical dimension of the first pattern structure 101 if the silicon loss is only a few nanometers. Therefore, if the device performance requires that this step is sensitive to the size of the exposed silicon, it is necessary to improve the etching performance.
[0005] There are two reasons why water etches the silicon surface:
[0006] First, there are still H+ and OH- ions in the water, and both ions will react with Si to cause Si etching;
[0007] Si+H + →Si 2+ +H2;
[0008] Si+OH - →SiO3 2- +H2.
[0009] Second, exposed Si will oxidize in the air, and water will accelerate the occurrence of this phenomenon;
[0010] Si+O2→SiO2. Summary of the Invention
[0011] The technical problem to be solved by the present invention is to provide a wafer cleaning method which can reduce the etching of materials exposed on the wafer surface.
[0012] To solve the above technical problems, the present invention provides a wafer cleaning method comprising the following steps:
[0013] A first solution is used to clean the wafer surface for the first time and form an isolation film on the wafer surface, wherein the hydrogen ion concentration of the first solution is lower than the hydrogen ion concentration of deionized water and the hydroxide ion concentration of the first solution is lower than the hydroxide ion concentration of the deionized water.
[0014] The wafer is cleaned for a second time using the deionized water. During the second cleaning, the isolation film reduces the etching effect of hydrogen ions and hydroxide ions in the deionized water on the material exposed on the surface of the wafer.
[0015] A further improvement is that the wafer includes a semiconductor substrate, and a first graphic structure composed of semiconductor material is formed on the semiconductor substrate.
[0016] A further improvement is that the semiconductor substrate is a silicon substrate, and the semiconductor material is silicon.
[0017] A further improvement is that the first graphic structure is formed by patterning and etching the semiconductor substrate, shallow trench isolations are formed on both sides of the first graphic structure, and the top surface of the first graphic structure protrudes above the top surface of the shallow trench isolations.
[0018] A further improvement is that the width of the first graphic structure is tens of nanometers.
[0019] A further improvement is that the first solution includes isopropyl alcohol.
[0020] A further improvement is that the shallow trench isolation formation process includes an oxide layer filling and an oxide layer etching back process;
[0021] The first cleaning is performed after the oxide layer etch-back process of the shallow trench isolation is completed.
[0022] Before the wafer is cleaned with deionized water, the present invention uses a first solution with a lower hydrogen ion and hydroxide ion content than deionized water for cleaning. In this way, the first solution will adhere to the surface of the wafer to form an isolation film. The isolation film can isolate the hydrogen ions and hydroxide ions in the deionized water, reducing the etching effect of the hydrogen ions and hydroxide ions on the materials exposed on the wafer surface. That is, compared with the direct contact of the hydrogen ions and hydroxide ions in the deionized water with the materials exposed on the wafer surface, the present invention can reduce the etching effect of the deionized water on the materials exposed on the wafer surface during cleaning, for example, it can reduce the etching effect on silicon materials.
[0023] The present invention reduces the etching effect of materials exposed on the wafer surface, such as silicon, during deionized water cleaning, thereby preventing the reduction of the critical size of the pattern formed by the materials exposed on the wafer surface, thereby ultimately improving product performance and yield. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:
[0025] Figure 1 It is a structural schematic diagram of the effect of the etching effect of the silicon exposed on the wafer surface by the existing wafer cleaning method on the critical dimensions of the silicon pattern;
[0026] Figure 2 is a flow chart of a wafer cleaning method according to an embodiment of the present invention;
[0027] Figure 3 This is a comparison chart of silicon etching amounts of the wafer cleaning method according to an embodiment of the present invention and the conventional wafer cleaning method. DETAILED DESCRIPTION
[0028] like Figure 2 FIG. 1 is a flow chart of a wafer cleaning method according to an embodiment of the present invention. The wafer cleaning method according to an embodiment of the present invention comprises the following steps:
[0029] Step S101: Use a first solution to clean the wafer surface for the first time and form an isolation film on the wafer surface, wherein the hydrogen ion concentration of the first solution is lower than the hydrogen ion concentration of deionized water and the hydroxide ion concentration of the first solution is lower than the hydroxide ion concentration of the deionized water.
[0030] Please refer to Figure 1 As shown, in an embodiment of the present invention, the wafer includes a semiconductor substrate 101, and a first pattern structure 102 composed of a semiconductor material is formed on the semiconductor substrate 101. In some embodiments, the semiconductor substrate 101 is a silicon substrate, and the semiconductor material is silicon.
[0031] The first graphic structure 102 is formed by patterning and etching the semiconductor substrate 101 . Shallow trench isolations 103 are formed on both sides of the first graphic structure 102 . The top surface of the first graphic structure 102 protrudes above the top surface of the shallow trench isolations 103 .
[0032] The formation process of the shallow trench isolation 103 includes an oxide layer filling and an oxide layer etching back process;
[0033] The first cleaning is performed after the oxide layer etch-back process of the shallow trench isolation 103 is completed.
[0034] Figure 1 , a cross-sectional structure of the first pattern structure 102 in the width direction is shown in FIG. , wherein the critical dimension (CD) is the width of the first pattern structure 102. In some embodiments, the width of the first pattern structure 102 is tens of nanometers. The first solution includes isopropyl alcohol.
[0035] Step S102 , using the deionized water to clean the wafer for a second time. During the second cleaning, the isolation film reduces the etching effect of hydrogen ions and hydroxide ions in the deionized water on the material exposed on the surface of the wafer.
[0036] When the width of the first graphic structure 101 is tens of nanometers, the etching amount of the first graphic structure 101 in the second cleaning process will account for a large proportion of the width of the first graphic structure 101 . Therefore, reducing the etching amount in the second cleaning process can improve the quality of the first graphic structure 101 .
[0037] In an embodiment of the present invention, before the wafer is cleaned with deionized water, a first solution having a lower hydrogen ion and hydroxide ion content than deionized water is used for cleaning. In this way, the first solution will adhere to the surface of the wafer to form an isolation film. The isolation film can isolate the hydrogen ions and hydroxide ions in the deionized water, thereby reducing the etching effect of the hydrogen ions and hydroxide ions on the materials exposed on the wafer surface. That is, compared with the direct contact of the hydrogen ions and hydroxide ions in the deionized water with the materials exposed on the wafer surface, the embodiment of the present invention can reduce the etching effect of the materials exposed on the wafer surface during deionized water cleaning, for example, it can reduce the etching effect on silicon materials.
[0038] Table 1
[0039]
[0040] Table 1 is a comparison table of silicon etching amounts of the wafer cleaning method according to the embodiment of the present invention and the conventional wafer cleaning method. In Table 1, wafer 1 adopts the conventional wafer cleaning method, and wafer 2 adopts the wafer cleaning method according to the embodiment of the present invention. The front layer SiCD refers to Figure 1The CD of the first graphic structure 102 before the wafer is cleaned, and the CD of the back layer Si is Figure 1 The CD of the first graphic structure 102 after the wafer is cleaned, the Si CD loss, corresponds to the reduction in CD of the first graphic structure 102, that is, the silicon etching amount. It can be seen that the Si CD loss of wafer 1 is 5.98nm, and the Si CD loss of wafer 2 is 5.48nm. The Si CD loss of wafer 2 is smaller, that is, the silicon etching amount of the wafer cleaning method according to the embodiment of the present invention is improved.
[0041] like Figure 3 FIG. 1 is a comparison chart of silicon etching amounts between the wafer cleaning method according to an embodiment of the present invention and the conventional wafer cleaning method. Figure 3 , the data in the area 201 to the left of the dotted line AA is the silicon etching amount obtained by testing when multiple wafers are cleaned using the existing wafer cleaning method, and the data in the area 202 to the right of the dotted line AA is the silicon etching amount obtained by testing when multiple wafers are cleaned using the wafer cleaning method of an embodiment of the present invention. It can be seen that the silicon etching amount in area 202 is less than the silicon etching amount in area 201.
[0042] The embodiments of the present invention help prevent the reduction of critical dimensions of patterns formed by materials exposed on the wafer surface, such as silicon, by reducing the etching effect of deionized water on materials exposed on the wafer surface during cleaning, thereby ultimately improving product performance and yield.
[0043] In an embodiment of the present invention, an isopropyl alcohol cleaning step is added before water cleaning. A layer of isopropyl alcohol liquid film is first generated before water cleaning, which can isolate the contact between water and the silicon surface to a certain extent, thereby inhibiting the etching effect of water on the exposed silicon surface and improving the etching of the silicon surface during the cleaning process.
[0044] The embodiments of the present invention have strong process feasibility and mass production applicability.
[0045] The present invention has been described in detail above by means of specific embodiments, but these do not constitute limitations of the present invention. Without departing from the principles of the present invention, those skilled in the art may make many variations and improvements, which should also be considered as the scope of protection of the present invention.
Claims
1. A wafer cleaning method, characterized in that: Including steps: Using a first solution to clean the wafer surface for the first time and form an isolation film on the wafer surface, wherein the hydrogen ion concentration of the first solution is lower than the hydrogen ion concentration of deionized water and the hydroxide ion concentration of the first solution is lower than the hydroxide ion concentration of the deionized water; The wafer is cleaned for a second time using the deionized water. During the second cleaning, the isolation film reduces the etching effect of hydrogen ions and hydroxide ions in the deionized water on the material exposed on the surface of the wafer.
2. The wafer cleaning method according to claim 1, wherein: The wafer includes a semiconductor substrate, on which a first pattern structure composed of semiconductor material is formed.
3. The wafer cleaning method according to claim 2, wherein: The semiconductor substrate is a silicon substrate, and the semiconductor material is silicon.
4. The wafer cleaning method according to claim 3, wherein: The first graphic structure is formed by patterning and etching the semiconductor substrate. Shallow trench isolations are formed on both sides of the first graphic structure. The top surface of the first graphic structure protrudes above the top surface of the shallow trench isolations.
5. The wafer cleaning method according to claim 4, wherein: The width of the first graphic structure is tens of nanometers.
6. The wafer cleaning method according to claim 4, wherein: The first solution includes isopropyl alcohol.
7. The wafer cleaning method according to claim 4, wherein: The shallow trench isolation formation process includes oxide layer filling and oxide layer etching back processes; The first cleaning is performed after the oxide layer etch-back process of the shallow trench isolation is completed.